Chronic diseases are defined broadly as conditions that last 1 year or more and require ongoing medical attention or limit activities of daily living or both. Chronic diseases such as heart disease, cancer, and diabetes are the leading causes of death and disability in the United States. They are also leading drivers of the nation’s $4.1 trillion in annual health care costs.
Three major Chronic Diseases are: heart disease, cancer, and diabetes.
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The major organs of the respiratory system function primarily to provide oxygen to body tissues for cellular respiration, remove the waste product carbon dioxide, and help to maintain acid-base balance. Portions of the respiratory system are also used for non-vital functions such as sensing odors, speech production, and for straining such as during childbirth or coughing.
The conducting zone consists of all of the structures that provide passageways for air to travel into and out of the lungs: the nasal cavity, pharynx, larynx, trachea, bronchi, and most bronchioles. The nasal passages contain the conchae and meatuses that expand the surface area of the cavity which helps to warm and humidify incoming air while removing debris and pathogens. The respiratory zone includes the structures of the lung that are directly involved in gas exchange: the terminal bronchioles and alveoli.
the main function of the conducting zone structures is to provide a passageway for air to move into and out of each lung. In addition, the mucous membrane traps debris and pathogens.
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Asthma is a common condition that affects the lungs in both adults and children. Approximately 8.2 percent of adults (18.7 million) and 9.4 percent of children (7 million) in the United States suffer from asthma. In addition, asthma is the most frequent cause of hospitalization in children.
Asthma is a chronic disease characterized by inflammation and edema of the airway and bronchospasms (that is, constriction of the bronchioles), which can inhibit air from entering the lungs. In addition, excessive mucus secretion can occur which further contributes to airway occlusion.
Bronchospasms occur periodically and lead to an “asthma attack.” An attack may be triggered by environmental factors such as dust, pollen, pet hair, or dander, changes in the weather, mold, tobacco smoke, and respiratory infections, or by exercise and stress.
An asthma attack includes thickened mucosa, increased mucus-producing goblet cells, and eosinophil infiltrates. (Figure 1)
Symptoms of an asthma attack involve coughing, shortness of breath, wheezing, and tightness of the chest. Symptoms of a severe asthma attack that requires immediate medical attention would include difficulty breathing that results in blue (cyanotic) lips or face, confusion, drowsiness, a rapid pulse, sweating, and severe anxiety. The severity of the condition, frequency of attacks, and identified triggers influence the type of medication that an individual may require. Longer-term treatments are used for those with more severe asthma. Short-term, fast-acting drugs that are used to treat an asthma attack are typically administered via an inhaler. For young children or individuals who have difficulty using an inhaler, asthma medications can be administered via a nebulizer.
In many cases, the underlying cause of the condition is unknown. However, recent research has demonstrated that certain viruses, such as human rhinovirus C (HRVC), and the bacteria Mycoplasma pneumoniae and Chlamydia pneumoniae that are contracted in infancy or early childhood, may contribute to the development of many cases of asthma.
Asthma symptoms can appear when you are exposed to a trigger. A trigger is something you are sensitive to that makes your airways become inflamed. This causes swelling, mucus production, and narrowing in your airways. Common asthma triggers are pollen, air pollution, animal allergens, scents/fragrances, certain gases, extreme weather changes, smoke, dust mites, stress, and exercise.
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A doctor may use a few different ways to look for asthma. These include:
The doctor will look at the results from these tests. They will then decide what type of asthma you have. They will develop a treatment plan based on the type and severity of your symptoms.
Although medicines help a lot, they may not be able to do the job alone. You have to avoid the things that cause or trigger your asthma symptoms as much as you can. Asthma triggers can be found outside or inside your home, school, or workplace.
Improving the indoor air quality in your home is an important part of asthma control. Your indoor air can be more polluted than outside air. The interactive Healthy Home by the Asthma and Allergy Foundation of America can show you ways to improve the indoor air quality of your home. A healthier home can reduce your exposure to allergens and irritants.
Racial and ethnic differences in asthma frequency, illness, and death are caused by complex factors, including:
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Cancer is a disease in which some of the body’s cells grow uncontrollably and spread to other parts of the body.
Cancer can start almost anywhere in the human body, which is made up of trillions of cells. Normally, human cells grow and multiply (through a process called cell division) to form new cells as the body needs them. When cells grow old or become damaged, they die, and new cells take their place.
Sometimes this orderly process breaks down, and abnormal or damaged cells grow and multiply when they shouldn’t. These cells may form tumors, which are lumps of tissue. Tumors can be cancerous or not cancerous (benign).
Cancerous tumors spread into, or invade, nearby tissues and can travel to distant places in the body to form new tumors (a process called metastasis). Cancerous tumors may also be called malignant tumors. Many cancers form solid tumors, but cancers of the blood, such as leukemias, generally do not.
Benign tumors do not spread into, or invade, nearby tissues. When removed, benign tumors usually don’t grow back, whereas cancerous tumors sometimes do. Benign tumors can sometimes be quite large, however. Some can cause serious symptoms or be life threatening, such as benign tumors in the brain.
Cancer cells differ from normal cells in many ways. For instance, cancer cells:
Many times, cancer cells rely so heavily on these abnormal behaviors that they can’t survive without them. Researchers have taken advantage of this fact, developing therapies that target the abnormal features of cancer cells. For example, some cancer therapies prevent blood vessels from growing toward tumors, essentially starving the tumor of needed nutrients.
Cancer is a genetic disease—that is, it is caused by changes to genes that control the way our cells function, especially how they grow and divide. (Figure 2.1)
Figure 2.1 Cancer is caused by certain changes to genes, the basic physical units of inheritance. Genes are arranged in long strands of tightly packed DNA called chromosomes. Credit: © Terese Winslow LLC U.S Govt. has certain rights
The body normally eliminates cells with damaged DNA before they turn cancerous. But the body’s ability to do so goes down as we age. This is part of the reason why there is a higher risk of cancer later in life.
Each person’s cancer has a unique combination of genetic changes. As the cancer continues to grow, additional changes will occur. Even within the same tumor, different cells may have different genetic changes.
The genetic changes that contribute to cancer tend to affect three main types of genes—proto-oncogenes, tumor suppressor genes, and DNA repair genes. These changes are sometimes called “drivers” of cancer.
Proto-oncogenes are involved in normal cell growth and division. However, when these genes are altered in certain ways or are more active than normal, they may become cancer-causing genes (or oncogenes), allowing cells to grow and survive when they should not.
Tumor suppressor genes are also involved in controlling cell growth and division. Cells with certain alterations in tumor suppressor genes may divide in an uncontrolled manner.
DNA repair genes are involved in fixing damaged DNA. Cells with mutations in these genes tend to develop additional mutations in other genes and changes in their chromosomes, such as duplications and deletions of chromosome parts. Together, these mutations may cause the cells to become cancerous.
As scientists have learned more about the molecular changes that lead to cancer, they have found that certain mutations commonly occur in many types of cancer. Now there are many cancer treatments available that target gene mutations found in cancer. A few of these treatments can be used by anyone with a cancer that has the targeted mutation, no matter where the cancer started growing.
A cancer that has spread from the place where it first formed to another place in the body is called metastatic cancer. The process by which cancer cells spread to other parts of the body is called metastasis. (Figure 2.2)
Metastatic cancer has the same name and the same type of cancer cells as the original, or primary, cancer. For example, breast cancer that forms a metastatic tumor in the lung is metastatic breast cancer, not lung cancer.
Under a microscope, metastatic cancer cells generally look the same as cells of the original cancer. Moreover, metastatic cancer cells and cells of the original cancer usually have some molecular features in common, such as the presence of specific chromosome changes.
In some cases, treatment may help prolong the lives of people with metastatic cancer. In other cases, the primary goal of treatment for metastatic cancer is to control the growth of the cancer or to relieve symptoms it is causing. Metastatic tumors can cause severe damage to how the body functions, and most people who die of cancer die of metastatic disease.
Not every change in the body’s tissues is cancer. Some tissue changes may develop into cancer if they are not treated, however. Here are some examples of tissue changes that are not cancer but, in some cases, are monitored because they could become cancer: (Figure 2.3)
Figure 2.3 Normal cells may become cancer cells. Before cancer cells form in tissues of the body, the cells go through abnormal changes called hyperplasia and dysplasia. In hyperplasia, there is an increase in the number of cells in an organ or tissue that appear normal under a microscope. In dysplasia, the cells look abnormal under a microscope but are not cancer. Hyperplasia and dysplasia may or may not become cancer. Credit: © Terese Winslow
It is usually not possible to know exactly why one person develops cancer and another doesn’t. But research has shown that certain risk factors may increase a person’s chances of developing cancer. (There are also factors that are linked to a lower risk of cancer. These are called protective factors.)
Cancer risk factors include exposure to chemicals or other substances, as well as certain behaviors. They also include things people cannot control, like age and family history. A family history of certain cancers can be a sign of a possible inherited cancer syndrome.
Most cancer risk (and protective) factors are initially identified in epidemiology studies. In these studies, scientists look at large groups of people and compare those who develop cancer with those who don’t. These studies may show that the people who develop cancer are more or less likely to behave in certain ways or to be exposed to certain substances than those who do not develop cancer.
Such studies, on their own, cannot prove that a behavior or substance causes cancer. For example, the finding could be a result of chance, or the true risk factor could be something other than the suspected risk factor. But findings of this type sometimes get attention in the media, and this can lead to wrong ideas about how cancer starts and spreads.
When many studies all point to a similar association between a potential risk factor and an increased risk of cancer, and when a possible mechanism exists that could explain how the risk factor could actually cause cancer, scientists can be more confident about the relationship between the two.
The list below includes the most studied known or suspected risk factors for cancer. Although some of these risk factors can be avoided, others—such as growing older—cannot. Limiting your exposure to avoidable risk factors may lower your risk of developing certain cancers. Click on each risk factor below to find out more:
Tobacco use is a leading cause of cancer and of death from cancer. People who use tobacco products or who are regularly around environmental tobacco smoke (also called secondhand smoke) have an increased risk of cancer because tobacco products and secondhand smoke have many chemicals that damage DNA.
Tobacco use causes many types of cancer, including cancer of the lung, larynx (voice box), mouth, esophagus, throat, bladder, kidney, liver, stomach, pancreas, colon and rectum, and cervix, as well as acute myeloid leukemia. People who use smokeless tobacco (snuff or chewing tobacco) have increased risks of cancers of the mouth, esophagus, and pancreas.
There is no safe level of tobacco use. People who use any type of tobacco product are strongly urged to quit. People who quit smoking, regardless of their age, have substantial gains in life expectancy compared with those who continue to smoke. Also, quitting smoking at the time of a cancer diagnosis reduces the risk of death.
Scientists believe that cigarette smoking causes about 30% of all cancer deaths in the United States.
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Lung cancer includes two main types: non-small cell lung cancer and small cell lung cancer. Smoking causes most lung cancers, but nonsmokers can also develop lung cancer. These categories refer to what cancer cells look like under a microscope. Non-small cell lung cancer is more common than small cell lung cancer.
Different people have different symptoms for lung cancer. Some people have symptoms related to the lungs. Some people whose lung cancer has spread to other parts of the body (metastasized) have symptoms specific to that part of the body. Some people just have general symptoms of not feeling well. Most people with lung cancer don’t have symptoms until the cancer is advanced. Lung cancer symptoms may include—
Other changes that can sometimes occur with lung cancer may include repeated bouts of pneumonia and swollen or enlarged lymph nodes (glands) inside the chest in the area between the lungs.
These signs and symptoms can happen with other illnesses, too. If you have some of these signs and symptoms, talk to your doctor, who can help find the cause.
Cigarette smoking is the number one risk factor for lung cancer. In the United States, cigarette smoking is linked to about 80% to 90% of lung cancer deaths. Using other tobacco products such as cigars or pipes also increases the risk for lung cancer. Tobacco smoke is a toxic mix of more than 7,000 chemicals. Many are poisons. At least 70 are known to cause cancer in people or animals.
People who smoke cigarettes are 15 to 30 times more likely to get lung cancer or die from lung cancer than people who do not smoke. Even smoking a few cigarettes a day or smoking occasionally increases the risk of lung cancer. The more years a person smokes and the more cigarettes smoked each day, the more risk goes up.
People who quit smoking have a lower risk of lung cancer than if they had continued to smoke, but their risk is higher than the risk for people who never smoked. Quitting smoking at any age can lower the risk of lung cancer.
Cigarette smoking can cause cancer almost anywhere in the body. Cigarette smoking causes cancer of the mouth and throat, esophagus, stomach, colon, rectum, liver, pancreas, voicebox (larynx), lung, trachea, bronchus, kidney and renal pelvis, urinary bladder, and cervix, and causes acute myeloid leukemia.
Lung cancer is treated in several ways, depending on the type of lung cancer and how far it has spread. People with non-small cell lung cancer can be treated with surgery, chemotherapy, radiation therapy, targeted therapy, or a combination of these treatments. People with small cell lung cancer are usually treated with radiation therapy and chemotherapy.
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Breast cancer is the second most common cancer in women after skin cancer. Mammograms can detect breast cancer early, possibly before it has spread.
The breast is made up of lobes and ducts. Each breast has 15 to 20 sections called lobes, which have many smaller sections called lobules. Lobules end in dozens of tiny bulbs that can make milk. The lobes, lobules, and bulbs are linked by thin tubes called ducts.(Figure 4)
Each breast also has blood vessels and lymph vessels. The lymph vessels carry an almost colorless, watery fluid called lymph. Lymph vessels carry lymph between lymph nodes. Lymph nodes are small, bean-shaped structures that filter lymph and store white blood cells that help fight infection and disease. Groups of lymph nodes are found near the breast in the axilla (under the arm), above the collarbone, and in the chest.
Different people have different symptoms of breast cancer. Some people do not have any signs or symptoms at all.
Some warning signs of breast cancer are—
Keep in mind that these symptoms can happen with other conditions that are not cancer.
Besides female sex, advancing age is the biggest risk factor for breast cancer. Reproductive factors that increase exposure to endogenous estrogen, such as early menarche and late menopause, increase risk, as does the use of combination estrogen-progesterone hormones after menopause. Nulliparity and alcohol consumption also are associated with increased risk.
Women with a family history or personal history of invasive breast cancer, ductal carcinoma in situ or lobular carcinoma in situ, or a history of breast biopsies that show benign proliferative disease have an increased risk of breast cancer.
Increased breast density is associated with increased risk. It is often a heritable trait but is also seen more frequently in nulliparous women, women whose first pregnancy occurs late in life, and women who use postmenopausal hormones and alcohol.
Exposure to ionizing radiation, especially during puberty or young adulthood, and the inheritance of detrimental genetic mutations increase breast cancer risk.
The Breast Cancer Risk Assessment Tool (BCRAT), also known as The Gail Model, allows health professionals to estimate a woman's risk of developing invasive breast cancer over the next five years and up to age 90 (lifetime risk).
The tool uses a woman's personal medical and reproductive history and the history of breast cancer among her first-degree relatives (mother, sisters, daughters) to estimate absolute breast cancer risk-her chance or probability of developing invasive breast cancer in a defined age interval.
This calculator takes about five minutes to complete.
The tool has been validated for White women, Black/African American women, Hispanic women, and for Asian and Pacific Islander women in the United States.
The tool may underestimate risk in Black women with previous biopsies and Hispanic women born outside the United States. Because data on American Indian/Alaska Native women are limited, their risk estimates are partly based on data for White women and may be inaccurate. Further studies are needed to refine and validate these models.
This tool cannot accurately estimate breast cancer risk for:
Although a woman's risk may be accurately estimated, these predictions do not allow one to say precisely which woman will develop breast cancer. In fact, some women who do not develop breast cancer have higher risk estimates than some women who do develop breast cancer.
Breast cancer is treated in several ways. It depends on the kind of breast cancer and how far it has spread. People with breast cancer often get more than one kind of treatment.
Doctors from different specialties often work together to treat breast cancer. Surgeons are doctors who perform operations. Medical oncologists are doctors who treat cancer with medicine. Radiation oncologists are doctors who treat cancer with radiation.
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Colorectal cancer is a disease in which malignant (cancer) cells form in the tissues of the colon or the rectum. Colorectal cancer is the third leading cause of death from cancer in the United States.
Figure 5 The colon is part of the body’s digestive system. The digestive system removes and processes nutrients (vitamins, minerals, carbohydrates, fats, proteins, and water) from foods and helps pass waste material out of the body. The digestive system is made up of the mouth, throat, esophagus, stomach, and the small and large intestines. The colon (large bowel) is the first part of the large intestine and is about 5 feet long. Together, the rectum and anal canal make up the last part of the large intestine and are 6 to 8 inches long. The anal canal ends at the anus (the opening of the large intestine to the outside of the body).
Colorectal polyps (abnormal growths in the colon or rectum that can turn into cancer if not removed) and colorectal cancer don’t always cause symptoms, especially at first. Someone could have polyps or colorectal cancer and not know it. That is why getting screened regularly for colorectal cancer is so important.
If you have symptoms, they may include—
Most people should begin screening for colorectal cancer soon after turning 45, then continue getting screened at regular intervals. However, you may need to be tested earlier than 45, or more often than other people, if you have—
Seven types of standard treatment are used:
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The vital importance of the heart is obvious. If one assumes an average rate of contraction of 75 contractions per minute, a human heart would contract approximately 108,000 times in one day, more than 39 million times in one year and nearly 3 billion times during a 75-year lifespan! Each of the major pumping chambers of the heart ejects approximately 70 mL blood per contraction in a resting adult. This would be equal to 5.25 litres of fluid per minute and approximately 14,000 litres per day. Over one year, that would equal 10,000,000 litres (2.6 million gallons) of blood sent through roughly 97,000 kilometres (60,000 miles) of vessels. In order to understand how that happens, it is necessary to understand the anatomy and physiology of the heart.
The human heart consists of four chambers: The left side and the right side each have one atrium and one ventricle. Each of the upper chambers, the right atrium (plural = atria) and the left atrium, acts as a receiving chamber and contracts to push blood into the lower chambers, the right ventricle and the left ventricle. The ventricles serve as the primary pumping chambers of the heart, propelling blood to the lungs or to the rest of the body.
There are two distinct but linked circuits in the human circulation called the pulmonary and systemic circuits. Although both circuits transport blood and everything it carries, we can initially view the circuits from the point of view of gases. The pulmonary circuit transports blood to and from the lungs, where it picks up oxygen and delivers carbon dioxide for exhalation. The systemic circuit transports oxygenated blood to virtually all the tissues of the body and returns relatively deoxygenated blood and carbon dioxide to the heart to be sent back to the pulmonary circulation.
The right ventricle pumps deoxygenated blood into the pulmonary trunk, which leads toward the lungs and bifurcates into the left and right pulmonary arteries. These vessels in turn branch many times before reaching the pulmonary capillaries, where gas exchange occurs: Carbon dioxide exits the blood and oxygen enters. The pulmonary trunk arteries and their branches are the only arteries in the post-natal body that carry relatively deoxygenated blood. Highly oxygenated blood returning from the pulmonary capillaries in the lungs passes through a series of vessels that join together to form the pulmonary veins—the only post-natal veins in the body that carry highly oxygenated blood. The pulmonary veins conduct blood into the left atrium, which pumps the blood into the left ventricle, which in turn pumps oxygenated blood into the aorta and on to the many branches of the systemic circuit. Eventually, these vessels will lead to the systemic capillaries, where exchange with the tissue fluid and cells of the body occurs. In this case, oxygen and nutrients exit the systemic capillaries to be used by the cells in their metabolic processes, and carbon dioxide and waste products will enter the blood.
The blood exiting the systemic capillaries is lower in oxygen concentration than when it entered. The capillaries will ultimately unite to form venules, joining to form ever-larger veins, eventually flowing into the two major systemic veins, the superior vena cava and the inferior vena cava, which return blood to the right atrium. The blood in the superior and inferior venae cavae flows into the right atrium, which pumps blood into the right ventricle. This process of blood circulation continues as long as the individual remains alive. Understanding the flow of blood through the pulmonary and systemic circuits is critical to all health professions (Figure 6.1.3).
There are four valves in the heart. The valves ensure unidirectional blood flow through the heart. Between the right atrium and the right ventricle is the right atrioventricular valve, or tricuspid valve.
Emerging from the right ventricle at the base of the pulmonary trunk is the pulmonary semilunar valve, or the pulmonary valve.
Located at the opening between the left atrium and left ventricle is the mitral valve, also called the bicuspid valve or the left atrioventricular valve.
At the base of the aorta is the aortic semilunar valve, or the aortic valve, which prevents backflow from the aorta.
Figure 6.1.3. Dual system of the human blood circulation. Blood flows from the right atrium to the right ventricle, where it is pumped into the pulmonary circuit. The blood in the pulmonary artery branches is low in oxygen but relatively high in carbon dioxide. Gas exchange occurs in the pulmonary capillaries (oxygen into the blood, carbon dioxide out), and blood high in oxygen and low in carbon dioxide is returned to the left atrium. From here, blood enters the left ventricle, which pumps it into the systemic circuit. Following exchange in the systemic capillaries (oxygen and nutrients out of the capillaries and carbon dioxide and wastes in), blood returns to the right atrium and the cycle is repeated.
You will recall that the heart is a remarkable pump composed largely of cardiac muscle cells that are incredibly active throughout life. Like all other cells, a cardiomyocyte requires a reliable supply of oxygen and nutrients, and a way to remove wastes, so it needs a dedicated, complex, and extensive coronary circulation. And because of the critical and nearly ceaseless activity of the heart throughout life, this need for a blood supply is even greater than for a typical cell.
Supply blood to the myocardium and other components of the heart. The first portion of the aorta after it arises from the left ventricle gives rise to the coronary arteries.
Figure 6.1.14. Coronary circulation. The anterior view of the heart shows the prominent coronary surface vessels. The posterior view of the heart shows the prominent coronary surface vessels.
Cardiovascular diseases (CVDs) are a group of disorders of the heart and blood vessels. They include:
Heart attacks and strokes are usually acute events and are mainly caused by a blockage that prevents blood from flowing to the heart or brain. The most common reason for this is a build-up of fatty deposits on the inner walls of the blood vessels that supply the heart or brain. Strokes can be caused by bleeding from a blood vessel in the brain or from blood clots.
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Coronary artery disease is the leading cause of death worldwide. It occurs when the build-up of plaque—a fatty material including cholesterol, connective tissue, white blood cells, and some smooth muscle cells—within the walls of the arteries obstructs the flow of blood and decreases the flexibility or compliance of the vessels. This condition is called atherosclerosis, a hardening of the arteries that involves the accumulation of plaque. As the coronary blood vessels become occluded, the flow of blood to the tissues will be restricted, a condition called ischaemia that causes the cells to receive insufficient amounts of oxygen, called hypoxia. Figure 6.1.15 shows the blockage of coronary arteries highlighted by the injection of dye. Some individuals with coronary artery disease report pain radiating from the chest called angina pectoris, but others remain asymptomatic. If untreated, coronary artery disease can lead to MI or a heart attack.
Figure 6.1.15. Atherosclerotic coronary arteries. In this coronary angiogram (X-ray), the dye makes visible two occluded coronary arteries. Such blockages can lead to decreased blood flow (ischaemia) and insufficient oxygen (hypoxia) delivered to the cardiac tissues. If uncorrected, this can lead to cardiac muscle death (myocardial infarction).
Leading risk factors for heart disease and stroke are high blood pressure, high low-density lipoprotein (LDL) cholesterol, diabetes, smoking and secondhand smoke exposure, obesity, unhealthy diet, and physical inactivity.
High blood pressure is a leading cause of heart disease and stroke because it damages the lining of the arteries, making them more susceptible to the buildup of plaque, which narrows the arteries leading to the heart and brain. About 116 million US adults (nearly 1 in 2) have high blood pressure, defined as 130/80 mm Hg or higher. Only about 1 in 4 of these people have their high blood pressure under control. About 7 in 10 people who have a first heart attack and 8 in 10 people who have a first stroke have high blood pressure.
Eating too much sodium can lead to high blood pressure. Americans aged 2 years or older consume an average of about 3,400 mg of sodium each day, well over the 2,300 mg recommended by the Dietary Guidelines for Americans. More than 70% of the sodium Americans consume is added outside the home (before purchase), not added as salt at the table or during home cooking.
High LDL cholesterol can double a person’s risk of heart disease. That’s because excess cholesterol can build up in the walls of arteries and limit blood flow to a person’s heart, brain, kidneys, other organs, and legs. Although nearly 86 million US adults could benefit from taking medicine to manage their high LDL cholesterol, only about half (55%) are doing so.
Adults with diabetes are twice as likely to have heart disease or a stroke as people who do not have diabetes. Over time, high blood sugar from diabetes can damage blood vessels in the heart and block blood vessels leading to the brain, causing a stroke. More than 2 in 3 people with diabetes have high blood pressure. Diabetes also raises triglycerides and LDL cholesterol.
Smoking is a major cause of heart disease and stroke and causes 1 in every 4 deaths from these conditions. Smoking can damage the body several ways by:
About 34 million US adults smoke cigarettes, and every day, about 1,600 young people under age 18 try their first cigarette.
Compared to those at a normal weight, people with overweight or obesity are at increased risk of heart disease and stroke and their risk factors, including high blood pressure, high LDL cholesterol, low HDL cholesterol, high triglycerides, and type 2 diabetes. In the United States, nearly 74% of adults have overweight or obesity.
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refers to the movement of blood through a vessel, tissue, or organ, and is usually expressed in terms of volume of blood per unit of time. It is initiated by the contraction of the ventricles of the heart. Ventricular contraction ejects blood into the major arteries, resulting in flow from regions of higher pressure to regions of lower pressure, as blood encounters smaller arteries and arterioles, then capillaries, then the venules and veins of the venous system. This section discusses a number of critical variables that contribute to blood flow throughout the body. It also discusses the factors that impede or slow blood flow, a phenomenon known as resistance.
Hydrostatic pressure is the force exerted by a fluid due to gravitational pull, usually against the wall of the container in which it is located. One form of hydrostatic pressure is blood pressure, the force exerted by blood upon the walls of the blood vessels or the chambers of the heart. Blood pressure may be measured in capillaries and veins, as well as the vessels of the pulmonary circulation; however, the term blood pressure without any specific descriptors typically refers to systemic arterial blood pressure—that is, the pressure of blood flowing in the arteries of the systemic circulation. In clinical practice, this pressure is measured in mm Hg and is usually obtained using the brachial artery of the arm.
Arterial blood pressure in the larger vessels consists of several distinct components (Figure 6.7.1): systolic and diastolic pressures, pulse pressure, and mean arterial pressure.
When systemic arterial blood pressure is measured, it is recorded as a ratio of two numbers (e.g., 120/80 is a normal adult blood pressure), expressed as systolic pressure over diastolic pressure. The systolic pressure is the higher value (typically around 120 mm Hg) and reflects the arterial pressure resulting from the ejection of blood during ventricular contraction, or systole. The diastolic pressure is the lower value (usually about 80 mm Hg) and represents the arterial pressure of blood during ventricular relaxation, or diastole.
As shown in Figure 6.7.1, the difference between the systolic pressure and the diastolic pressure is the pulse pressure. For example, an individual with a systolic pressure of 120 mm Hg and a diastolic pressure of 80 mm Hg would have a pulse pressure of 40 mmHg.
Mean arterial pressure (MAP) represents the “average” pressure of blood in the arteries, that is, the average force driving blood into vessels that serve the tissues. Mean is a statistical concept and is calculated by taking the sum of the values divided by the number of values.
Five variables influence blood flow and blood pressure:
Blood moves from higher pressure to lower pressure. It is pumped from the heart into the arteries at high pressure. If you increase pressure in the arteries (afterload), and cardiac function does not compensate, blood flow will actually decrease. In the venous system, the opposite relationship is true. Increased pressure in the veins does not decrease flow as it does in arteries, but actually increases flow. Since pressure in the veins is normally relatively low, for blood to flow back into the heart, the pressure in the atria during atrial diastole must be even lower. It normally approaches zero, except when the atria contract. (see Figure 6.7.1).
Cardiac output is the measurement of blood flow from the heart through the ventricles and is usually measured in litres per minute. Any factor that causes cardiac output to increase, by elevating heart rate or stroke volume or both, will elevate blood pressure and promote blood flow.
Compliance is the ability of any compartment to expand to accommodate increased content. A metal pipe, for example, is not compliant, whereas a balloon is. The greater the compliance of an artery, the more effectively it is able to expand to accommodate surges in blood flow without increased resistance or blood pressure. Veins are more compliant than arteries and can expand to hold more blood. When vascular disease causes stiffening of arteries, compliance is reduced and resistance to blood flow is increased. The result is more turbulence, higher pressure within the vessel, and reduced blood flow. This increases the work of the heart.
The relationship between blood volume, blood pressure, and blood flow is intuitively obvious. Water may merely trickle along a creek bed in a dry season but rush quickly and under great pressure after a heavy rain. Similarly, as blood volume decreases, pressure and flow decrease. As blood volume increases, pressure and flow increase.
Viscosity is the thickness of fluids that affects their ability to flow. Clean water, for example, is less viscous than mud. The viscosity of blood is directly proportional to resistance and inversely proportional to flow; therefore, any condition that causes viscosity to increase will also increase resistance and decrease flow.
The length of a vessel is directly proportional to its resistance: the longer the vessel, the greater the resistance and the lower the flow. As with blood volume, this makes intuitive sense, since the increased surface area of the vessel will impede the flow of blood. Likewise, if the vessel is shortened, the resistance will decrease and flow will increase.
The length of our blood vessels increases throughout childhood as we grow, of course, but is unchanging in adults under normal physiological circumstances. Further, the distribution of vessels is not the same in all tissues. Adipose tissue does not have an extensive vascular supply. One pound of adipose tissue contains approximately 200 miles of vessels, whereas skeletal muscle contains more than twice that.
In contrast to length, the diameter of blood vessels changes throughout the body, according to the type of vessel. The diameter of any given vessel may also change frequently throughout the day in response to neural and chemical signals that trigger vasodilation and vasoconstriction. The vascular tone of the vessel is the contractile state of the smooth muscle and the primary determinant of diameter, and thus of resistance and flow. The effect of vessel diameter on resistance is inverse: Given the same volume of blood, an increased diameter means there is less blood contacting the vessel wall, thus lower friction and lower resistance, subsequently increasing flow. A decreased diameter means more of the blood contacts the vessel wall, and resistance increases, subsequently decreasing flow.
The influence of lumen diameter on resistance is dramatic: A slight increase or decrease in diameter causes a huge decrease or increase in resistance.
In order to maintain homeostasis in the cardiovascular system and provide adequate blood to the tissues, blood flow must be redirected continually to the tissues as they become more active. In a very real sense, the cardiovascular system engages in resource allocation, because there is not enough blood flow to distribute blood equally to all tissues simultaneously. For example, when an individual is exercising, more blood will be directed to skeletal muscles, the heart, and the lungs. Following a meal, more blood is directed to the digestive system. Only the brain receives a more or less constant supply of blood whether you are active, resting, thinking, or engaged in any other activity.
Three homeostatic mechanisms ensure adequate blood flow, blood pressure, distribution, and ultimately perfusion: neural, endocrine, and autoregulatory mechanisms. They are summarized in Figure 6.9.1.
We will focus on endocrine control involving the kidneys as the kidneys play an important role in long-term level of arterial blood pressure regulation.
Antidiuretic hormone (ADH), also known as vasopressin, is secreted by the cells in the hypothalamus. The primary trigger prompting the hypothalamus to release ADH is increasing osmolarity of tissue fluid, usually in response to significant loss of blood volume. ADH signals its target cells in the kidneys to reabsorb more water, thus preventing the loss of additional fluid in the urine. This will increase overall fluid levels and help restore blood volume and pressure. In addition, ADH constricts peripheral vessels.
The renin-angiotensin-aldosterone mechanism has a major effect upon the cardiovascular system (Figure 6.9.3). Renin is an enzyme, although because of its importance in the renin-angiotensin-aldosterone pathway, some sources identify it as a hormone. Specialized cells in the kidneys found in the juxtaglomerular apparatus respond to decreased blood flow by secreting renin into the blood. Renin converts the plasma protein angiotensinogen, which is produced by the liver, into its active form—angiotensin I. Angiotensin I circulates in the blood and is then converted into angiotensin II in the lungs. This reaction is catalyzed by the enzyme angiotensin-converting enzyme (ACE).
Angiotensin II is a powerful vasoconstrictor, greatly increasing blood pressure. It also stimulates the release of ADH and aldosterone, a hormone produced by the adrenal cortex. Aldosterone increases the reabsorption of sodium into the blood by the kidneys. Since water follows sodium, this increases the reabsorption of water. This in turn increases blood volume, raising blood pressure. Angiotensin II also stimulates the thirst center in the hypothalamus, so an individual will likely consume more fluids, again increasing blood volume and pressure.
Secreted by cells in the atria of the heart, atrial natriuretic hormone (ANH) or also known as atrial natriuretic peptide, is secreted when blood volume is high enough to cause extreme stretching of the cardiac cells. Natriuretic hormones are antagonists to angiotensin II. They promote loss of sodium and water from the kidneys, and suppress renin, aldosterone and ADH production and release. All of these actions promote loss of fluid from the body, so blood volume and blood pressure drop.
Figure 6.9.1. Summary of factors maintaining vascular homeostasis from Fundamentals of Anatomy and Physiology. Adequate blood flow, blood pressure, distribution, and perfusion involve autoregulatory, neural, and endocrine mechanisms.
High blood pressure increases the risk for heart disease and stroke, two leading causes of death for Americans. High blood pressure is also very common. Tens of millions of adults in the United States have high blood pressure, and many do not have it under control.
High blood pressure usually has no symptoms, so the only way to know if you have it is to get your blood pressure measured.
https://youtu.be/4YNdp3pRjig?si=yJikzXqyaGc2U48k
Take home:
Your blood pressure changes throughout the day based on your activities. For most adults, a normal blood pressure is less than 120 over 80 millimeters of mercury (mm Hg), which is written as your systolic pressure reading over your diastolic pressure reading — 120/80 mm Hg. Your blood pressure is considered high when you have consistent systolic readings of 130 mm Hg or higher or diastolic readings of 80 mm Hg or higher.
Classification | Systolic and diastolic readings |
---|---|
Normal | systolic: less than 120 mm Hg. diastolic: less than 80 mm Hg |
Elevated | systolic: 120–129 mm Hg. diastolic: less than 80 mm Hg |
High blood pressure | systolic: 130 mm Hg or higher. diastolic: 80 mm Hg or higher |
https://youtu.be/24h7ZkF8C_4?si=zRzyrYMTPgn4_p41
If you have high blood pressure, your provider may recommend that you adopt a heart-healthy lifestyle to help lower and control high blood pressure.
Changing habits can be hard. To help make lifelong heart-healthy changes, try making one change at a time. Add another change when you feel comfortable with the previous one. You’re more likely to manage your blood pressure when you practice several of these healthy lifestyle habits together and can keep them up over time.
When healthy lifestyle changes alone do not control or lower high blood pressure, your healthcare provider may prescribe blood pressure medicines. These medicines act in different ways to lower blood pressure. When prescribing medicines, your provider also considers their effect on other conditions you have, such as heart disease or kidney disease.
Keep up your healthy lifestyle changes while taking these medicines. The combination of medicines and heart-healthy lifestyle changes can help control and lower your high blood pressure and prevent heart disease.
By the end of this section, you will be able to:
Weight that is higher than what is considered healthy for a given height is described as overweight or obesity. Body Mass Index (BMI) is a screening tool for overweight and obesity.
Obesity is a complex disease that occurs when an individual’s weight is higher than what is considered healthy for his or her height. Obesity affects children as well as adults. Many factors can contribute to excess weight gain including eating patterns, physical activity levels, and sleep routines. Social determinants of health, genetics, and taking certain medications also play a role.
Eating and physical activity patterns, insufficient sleep and several other factors influence excess weight gain.
The conditions in which we live, learn, work, and play are called social determinants of health (SDOH). It can be difficult to make healthy food choices and get enough physical activity if these conditions do not support health. Differences in SDOH affect chronic disease outcomes and risks, including obesity, among racial, ethnic, and socioeconomic groups as well as in different geographies and among people with different physical abilities.
Places such as childcare centers, schools, or communities affect eating patterns and activity through the foods and drinks they offer and the physical activity opportunities they provide. Other community factors that influence obesity include the affordability of healthy food options, peer and social supports, marketing and promotion, and policies that determine community design.
Genetic changes in human populations occur too slowly to be responsible for the obesity epidemic. Yet variants in several genes may contribute to obesity by increasing hunger and food intake. Rarely, a specific variant of a single gene (monogenic obesity) causes a clear pattern of inherited obesity within a family.[1], [2]
Some illnesses, such as Cushing’s disease, may lead to obesity or weight gain. Drugs such as steroids and some antidepressants may also cause weight gain. Research continues on the role of other factors such as chemical exposures and the role of the microbiome.
People who have obesity, compared to those with a healthy weight, are at increased risk for many serious diseases and health conditions. In addition, obesity and its associated health problems have a significant economic impact on the US health care system. Obesity also affects military readiness.
Obesity in children and adults increases the risk for the following health conditions:
Childhood obesity is also associated with:
Adults with obesity have higher risks for stroke, many types of cancer, premature death, and mental illness such as clinical depression and anxiety.
Communication is a process in which a sender transmits signals to one or more receivers to control and coordinate actions. In the human body, two major organ systems participate in relatively “long distance” communication: the nervous system and the endocrine system. Together, these two systems are primarily responsible for maintaining homeostasis in the body.
The nervous system uses two types of intercellular communication—electrical and chemical signaling—either by the direct action of an electrical potential, or in the latter case, through the action of chemical neurotransmitters such as serotonin or noradrenaline. Neurotransmitters act locally and rapidly.
In contrast, the endocrine system uses just one method of communication: chemical signaling. These signals are sent by the endocrine organs, which secrete chemicals—the hormone—into the extracellular fluid. Hormones are transported primarily via the bloodstream throughout the body, where they bind to receptors on target cells, inducing a characteristic response. As a result, endocrine signaling requires more time than neural signaling to prompt a response in target cells, though the precise amount of time varies with different hormones.
The endocrine system includes the pituitary, thyroid, parathyroid, adrenal and pineal glands (Figure 14.1.1). Some of these glands have both endocrine and non-endocrine (exocrine) functions, for example, the pancreas contains cells that function in digestion as well as cells that secrete the hormones insulin and glucagon, which regulate blood glucose levels. The hypothalamus, thymus, heart, kidneys, stomach, small intestine, liver, skin, female ovaries and male testes are other organs that contain cells with endocrine function. Additionally, adipose tissue has long been known to produce hormones and recent research has shown that even bone tissue has endocrine functions.
Figure 14.1.1. Endocrine system. Endocrine glands and cells are located throughout the body and play an important role in homeostasis.
The hypothalamus–pituitary complex (Figure 14.3.1) can be thought of as the “command center” of the endocrine system. This complex secretes several hormones that directly produce responses in target tissues, as well as hormones that regulate the synthesis and secretion of hormones of other glands.
Figure 14.3.1. Hypothalamus–pituitary complex. The hypothalamus region lies inferior and anterior to the thalamus. It connects to the pituitary gland by the stalk-like infundibulum. The pituitary gland consists of an anterior and posterior lobe, with each lobe secreting different hormones in response to signals from the hypothalamus.
Major pituitary hormones and their target organs are shown in Figure 14.3.5.
Figure 14.3.5. Major pituitary hormones. Major pituitary hormones and their target organs
Adipose tissue produces and secretes several hormones involved in lipid metabolism and storage. One important example is leptin, a protein manufactured by adipose cells that circulates in amounts directly proportional to levels of body fat. Leptin is released in response to food consumption and acts by binding to brain neurons involved in energy intake and expenditure. Binding of leptin produces a feeling of satiety after a meal, thereby reducing appetite. It also appears that the binding of leptin to brain receptors triggers the sympathetic nervous system to regulate bone metabolism, increasing deposition of cortical bone. Adiponectin—another hormone synthesized by adipose cells—appears to reduce cellular insulin resistance and to protect blood vessels from inflammation and atherosclerosis. Its levels are lower in people who are obese and rise following weight loss.
https://youtu.be/zMjS_X5Hk7Y?si=GwgmStF0XDQQMYkL
https://youtu.be/VlOMDf6wUGI?si=IDy3Rj2tMSAE0eaJ
Easy access to nutrients has contributed to the increase in obesity in the human population. But, what is obesity and why isn’t everybody fat? Dr. Stephen O’Rahilly provides a biomedical perspective of obesity, and evaluates which genes could potentially shift the balance towards obesity. As he explains, one becomes obese when the balance between energy intake and energy spent is shifted. Surprisingly, mutations that lead to obesity in humans aren’t in genes involved in metabolism and energy storage, but failure in satiety signals in the brain that result in people eating too much. The excess of energy intake over energy expenditure leads to obesity.
What is the consequence of obesity in human health? Physically, obesity can result in lower mobility and sleeping disorders. But, in humans, the link between obesity and metabolic diseases isn’t straightforward. For example, not everyone that’s obese becomes insulin resistant. As O’Rahilly explains, the probability of an obese individual to have a metabolic disease is linked to the capacity of adipose tissue to store the extra fat. Mutations that decrease fat storage in adipose tissue increase the chance of metabolic diseases, like insulin resistance, even when the person is not obese.
By the end of this section, you will be able to:
The pancreas is a long, slender organ, most of which is located posterior to the bottom half of the stomach (Figure 14.9.1). Although it is primarily an exocrine gland, secreting a variety of digestive enzymes, the pancreas has an endocrine function. Its pancreatic islets—clusters of cells formerly known as the islets of Langerhans—secrete the hormones glucagon, insulin, somatostatin and pancreatic polypeptide (PP) among others.
Figure 14.9.1. Pancreas. The pancreatic exocrine function involves the acinar cells secreting digestive enzymes that are transported into the small intestine by the pancreatic duct. Its endocrine function involves the secretion of insulin (produced by beta cells) and glucagon (produced by alpha cells) within the pancreatic islets. These two hormones regulate the rate of glucose metabolism in the body. The micrograph shows pancreatic islets. LM × 760. (Micrograph provided by the Regents of University of Michigan Medical School © 2012).
Glucose is required for cellular respiration and is the preferred fuel for all body cells. The body derives glucose from the breakdown of the carbohydrate-containing foods and drinks we consume. Glucose not immediately taken up by cells for fuel can be stored by the liver and muscles as glycogen or converted to triglycerides and stored in the adipose tissue. Hormones regulate both the storage and the utilization of glucose as required. Receptors located in the pancreas sense blood glucose levels, and subsequently the pancreatic cells secrete glucagon or insulin to maintain normal levels.
Receptors in the pancreas can sense the decline in blood glucose levels, such as during periods of fasting or during prolonged labor or exercise (Figure 14.9.2). In response, the alpha cells of the pancreas secrete the hormone glucagon, which has several effects:
Taken together, these actions increase blood glucose levels. The activity of glucagon is regulated through a negative feedback mechanism; rising blood glucose levels inhibit further glucagon production and secretion.
The primary function of insulin is to facilitate the uptake of glucose into body cells. Red blood cells, as well as cells of the brain, liver, kidneys, and the lining of the small intestine, do not have insulin receptors on their cell membranes and do not require insulin for glucose uptake. Although all other body cells do require insulin if they are to take glucose from the bloodstream, skeletal muscle cells and adipose cells are the primary targets of insulin.
The presence of food in the intestine triggers the release of gastrointestinal tract hormones such as glucose-dependent insulinotropic peptide (previously known as gastric inhibitory peptide). This is in turn the initial trigger for insulin production and secretion by the beta cells of the pancreas. Once nutrient absorption occurs, the resulting surge in blood glucose levels further stimulates insulin secretion.
Insulin also reduces blood glucose levels by stimulating glycolysis, the metabolism of glucose for generation of ATP. Moreover, it stimulates the liver to convert excess glucose into glycogen for storage, and it inhibits enzymes involved in glycogenolysis and gluconeogenesis. Finally, insulin promotes triglyceride and protein synthesis. The secretion of insulin is regulated through a negative feedback mechanism. As blood glucose levels decrease, further insulin release is inhibited.
Figure 14.9.2. Homeostatic regulation of blood glucose levels. Blood glucose concentration is tightly maintained between 70 mg/dL and 110 mg/dL (or between 4.0 mmol/L and 7.8 mmol/L). If blood glucose concentration rises above this range, insulin is released, which stimulates body cells to remove glucose from the blood. If blood glucose concentration drops below this range, glucagon is released, which stimulates body cells to release glucose into the blood.
Dysfunction of insulin production and secretion, as well as the target cells’ responsiveness to insulin, can lead to a condition called diabetes mellitus.
There are two main forms of diabetes mellitus. Type 1 diabetes is an autoimmune disease affecting the beta cells of the pancreas. Certain genes are recognized to increase susceptibility. The beta cells of people with type 1 diabetes do not produce insulin; thus, synthetic insulin must be administered by injection or infusion. This form of diabetes accounts for less than five percent of all diabetes cases. Type 2 diabetes accounts for approximately 95 percent of all cases. About 80 to 90 percent of people with type 2 diabetes are overweight or obese. In type 2 diabetes, cells become resistant to the effects of insulin. In response, the pancreas increases its insulin secretion, but over time, the beta cells become exhausted. In many cases, type 2 diabetes can be reversed by moderate weight loss, regular physical activity, and consumption of a healthy diet; however, if blood glucose levels cannot be controlled, the diabetic will eventually require insulin.
Two of the early manifestations of diabetes are excessive urination and excessive thirst. They demonstrate how the out-of-control levels of glucose in the blood affect kidney function. The kidneys are responsible for filtering glucose from the blood. Excessive blood glucose draws water into the urine, and as a result the person eliminates an abnormally large quantity of sweet urine. The use of body water to dilute the urine leaves the body dehydrated, and so the person is unusually and continually thirsty. The person may also experience persistent hunger because the body cells are unable to access the glucose in the bloodstream.
Over time, persistently high levels of glucose in the blood injure tissues throughout the body, especially those of the blood vessels and nerves. Inflammation and injury of the lining of arteries lead to atherosclerosis and an increased risk of heart attack and stroke. Damage to the microscopic blood vessels of the kidney impairs kidney function and can lead to kidney failure. Damage to blood vessels that serve the eyes can lead to blindness. Blood vessel damage also reduces circulation to the limbs, whereas nerve damage leads to a loss of sensation, called neuropathy, particularly in the hands and feet. Together, these changes increase the risk of injury, infection, and tissue death (necrosis), contributing to a high rate of toe, foot, and lower leg amputations in people with diabetes.
Uncontrolled diabetes can also lead to a dangerous form of metabolic acidosis called ketoacidosis. Deprived of glucose, cells increasingly rely on fat stores for fuel. However, in a glucose-deficient state, the liver is forced to use an alternative lipid metabolism pathway that results in the increased production of ketone bodies (or ketones), which are acidic. The build-up of ketones in the blood causes ketoacidosis, which—if left untreated—may lead to a life-threatening “diabetic coma.” Together, these complications make diabetes the seventh leading cause of death in the United States.
Diabetes is diagnosed when lab tests reveal that blood glucose concentrations are higher than normal, a condition called hyperglycemia.
The treatment of diabetes depends on the type, the severity of the condition, and the ability of the patient to make lifestyle changes. Research advances have resulted in alternative options, including medications that enhance pancreatic function.
Type 1 diabetes is thought to be caused by an immune reaction (the body attacks itself by mistake).
Risk factors for type 1 diabetes are not as clear as for prediabetes and type 2 diabetes. Known risk factors include:
In the United States, White people are more likely to develop type 1 diabetes than African American and Hispanic or Latino people.
Currently, no one knows how to prevent type 1 diabetes.
If you have non-alcoholic fatty liver disease you may also be at risk for type 2 diabetes.
Ready to see where you stand? Take the 1-minute prediabetes risk test.
Can Type 2 Diabetes Be Prevented? Yes! You can prevent or delay type 2 diabetes with proven, achievable lifestyle changes—such as losing a small amount of weight and getting more physically active—even if you’re at high risk.
Tests for Type 1 Diabetes, Type 2 Diabetes, and Prediabetes
By the end of this section, you will be able to:
In humans, the left kidney is located at about the T12 to L3 vertebrae, whereas the right is lower due to slight displacement by the liver. Upper portions of the kidneys are somewhat protected by the eleventh and twelfth ribs (Figure 17.3.1).
Figure 17.3.1. Kidneys from Fundamentals of Anatomy and Physiology. The kidneys are slightly protected by the ribs and are surrounded by fat for protection (not shown).
On the superior aspect of each kidney is the adrenal gland. The adrenal cortex directly influences renal function through the production of the hormone aldosterone to stimulate sodium reabsorption.
Nephrons are the “functional units” of the kidney; they cleanse the blood and balance the constituents of the circulation. (Figure 17.3.3)
Madhero88 Physiology of Nephron, CC BY 3.0, via Wikimedia Commons
Diagram showing the basic physiologic mechanisms of the kidney and the three steps involved in urine formation. Namely filtration, reabsorption, secretion, and excretion. Tubular secretion occurs throughout the different parts of the nephron, from the proximal convoluted tubule to the collecting duct at the end of the nephron.
All systems of the body are interrelated. A change in one system may affect all other systems in the body, with mild to devastating effects. A failure of urinary continence can be embarrassing and inconvenient but is not life threatening. The loss of other urinary functions may prove fatal.
In order for vitamin D to become active, it must undergo a hydroxylation reaction in the kidney. Activated vitamin D is important for absorption of Ca2+ in the digestive tract, its reabsorption in the kidney and the maintenance of normal serum concentrations of Ca2+ and phosphate. Calcium is vitally important in bone health, muscle contraction, hormone secretion, and neurotransmitter release.
Erythropoietin, EPO stimulates the formation of red blood cells in the bone marrow. The kidney produces 85 percent of circulating EPO; the liver, the remainder.
Due to osmosis, water follows where Na+ leads. Much of the water the kidneys recover from the forming urine follows the reabsorption of Na+.
The kidneys cooperate with the lungs, liver and adrenal cortex through the renin–angiotensin–aldosterone system. The liver synthesizes and secretes the inactive precursor angiotensinogen. When the blood pressure is low, the kidney synthesizes and releases renin. Renin converts angiotensinogen into angiotensin I and ACE produced in the lung converts angiotensin I into biologically active angiotensin II (Figure 17.10.1). The immediate and short-term effect of angiotensin II is to raise blood pressure by causing widespread vasoconstriction. Angiotensin II also stimulates the adrenal cortex to release the steroid hormone aldosterone, which results in renal reabsorption of Na+ and its associated osmotic recovery of water. The reabsorption of Na+ helps to raise and maintain blood pressure over a longer term.
Blood pressure and osmolarity are regulated in a similar fashion.
Sodium, calcium and potassium must be closely regulated. Failure of K+ regulation can have serious consequences on nerve conduction, skeletal muscle function, and most significantly, on cardiac muscle contraction and rhythm.
Enzymes lose their three-dimensional conformation and therefore their function, if the pH is too acidic or basic. Proper kidney function is essential for pH homeostasis.
https://youtu.be/FN3MFhYPWWo?si=r6fbG_0n2imcUljM
CKD is a condition in which the kidneys are damaged and cannot filter blood as well as they should. Because of this, excess fluid and waste from blood remain in the body and may cause other health problems, such as heart disease and stroke.
Diabetes and high blood pressure are the more common causes of CKD in most adults. Other risk factors include heart disease, obesity, a family history of CKD, inherited kidney disorders, past damage to the kidneys, and older age.
One of the earliest signs of kidney disease is when protein leaks into your urine (called proteinuria).
Because your kidneys remove waste, toxins, and extra fluid from the blood, a doctor will also use a blood test to check your kidney function. The blood tests will show how well your kidneys are doing their job and how quickly the waste is being removed. Here are a few blood tests that are used:
https://youtu.be/VmOiat5-JxA?si=BKM6c_hyGQj8lvzV
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