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If ventilation is insufficient and the partial pressure of oxygen drops in the alveolar air claritin 10 mg on line, the capillary is constricted and blood flow is redirected to alveoli with sufficient ventilation buy 10 mg claritin with mastercard. External respiration refers to gas exchange that occurs in the alveoli best claritin 10mg, whereas internal respiration refers to gas exchange that occurs in the tissue. These cells contain a metalloprotein called hemoglobin, which is composed of four subunits with a ring-like structure. When all of the heme units in the blood are bound to oxygen, hemoglobin is considered to be saturated. An oxygen–hemoglobin saturation/dissociation curve is a common way to 1080 Chapter 22 | The Respiratory System depict the relationship of how easily oxygen binds to or dissociates from hemoglobin as a function of the partial pressure of oxygen. At the same time, once one molecule of oxygen is bound by hemoglobin, additional oxygen molecules more readily bind to hemoglobin. Other factors such as temperature, pH, the partial pressure of carbon dioxide, and the concentration of 2,3-bisphosphoglycerate can enhance or inhibit the binding of hemoglobin and oxygen as well. Fetal hemoglobin has a different structure than adult hemoglobin, which results in fetal hemoglobin having a greater affinity for oxygen than adult hemoglobin. Carbon dioxide is transported in blood by three different mechanisms: as dissolved carbon dioxide, as bicarbonate, or as carbaminohemoglobin. For this conversion, carbon dioxide is combined with water with the aid of an enzyme called carbonic anhydrase. This combination forms carbonic acid, which spontaneously dissociates into bicarbonate and hydrogen ions. As bicarbonate builds up in erythrocytes, it is moved across the membrane into the plasma in exchange for chloride ions by a mechanism called the chloride shift. At the pulmonary capillaries, bicarbonate re-enters erythrocytes in exchange for chloride ions, and the reaction with carbonic anhydrase is reversed, recreating carbon dioxide and water. The partial pressures of carbon dioxide and oxygen, as well as the oxygen saturation of hemoglobin, influence how readily hemoglobin binds carbon dioxide. The less saturated hemoglobin is and the lower the partial pressure of oxygen in the blood is, the more readily hemoglobin binds to carbon dioxide. However, in certain cases, the respiratory system must adjust to situational changes in order to supply the body with sufficient oxygen. For example, exercise results in increased ventilation, and chronic exposure to a high altitude results in a greater number of circulating erythrocytes. Hyperpnea, an increase in the rate and depth of ventilation, appears to be a function of three neural mechanisms that include a psychological stimulus, motor neuron activation of skeletal muscles, and the activation of proprioceptors in the muscles, joints, and tendons. As a result, hyperpnea related to exercise is initiated when exercise begins, as opposed to when tissue oxygen demand actually increases. In contrast, acute exposure to a high altitude, particularly during times of physical exertion, does result in low blood and tissue levels of oxygen. This change is caused by a low partial pressure of oxygen in the air, because the atmospheric pressure at high altitudes is lower than the atmospheric pressure at sea level. Over a long period of time, a person’s body will adjust to the high altitude, a process called acclimatization. During acclimatization, the low tissue levels of oxygen will cause the kidneys to produce greater amounts of the hormone erythropoietin, which stimulates the production of erythrocytes. Ectodermal tissue in the anterior portion of the head region invaginates posteriorly, forming olfactory pits, which ultimately fuse with endodermal tissue of the early pharynx. At about this same time, an protrusion of endodermal tissue extends anteriorly from the foregut, producing a lung bud, which continues to elongate until it forms the laryngotracheal bud. The proximal portion of this structure will mature into the trachea, whereas the bulbous end will branch to form two bronchial buds. Development progresses after week 16 as respiratory bronchioles and alveolar ducts form, and extensive vascularization occurs. As the fetus grows, the respiratory system continues to expand as more alveoli develop and more surfactant is produced. Beginning at about week 36 and lasting into childhood, alveolar precursors mature to become fully functional alveoli. Fetal breathing movements begin around week 20 or 21, and occur when contractions of the respiratory muscles cause the fetus to inhale and exhale amniotic fluid. These movements continue until birth and may help to tone the muscles in preparation for breathing after birth and are a sign of good health. Explain how spirometry test results can be used to diagnose respiratory diseases or determine the effectiveness of disease treatment. The ________ circulation picks up oxygen for cellular use and drops off carbon dioxide for removal from the a. Of course, you enjoy the apple’s taste as you chew it, but in the hours that follow, unless something goes amiss and you get a stomachache, you don’t notice that your digestive 1086 Chapter 23 | The Digestive System system is working. You may be taking a walk or studying or sleeping, having forgotten all about the apple, but your stomach and intestines are busy digesting it and absorbing its vitamins and other nutrients. In short, whether you pay attention or not, the organs of the digestive system perform their specific functions, allowing you to use the food you eat to keep you going. This chapter examines the structure and functions of these organs, and explores the mechanics and chemistry of the digestive processes. Although the small intestine is the workhorse of the system, where the majority of digestion occurs, and where most of the released nutrients are absorbed into the blood or lymph, each of the digestive system organs makes a vital contribution to this process (Figure 23. As is the case with all body systems, the digestive system does not work in isolation; it functions cooperatively with the other systems of the body. Arteries supply the digestive organs with oxygen and processed nutrients, and veins drain the digestive tract. These intestinal veins, constituting the hepatic portal system, are unique; they do not return blood directly to the heart. Rather, this blood is diverted to the liver where its nutrients are off-loaded for processing before blood completes its circuit back to the heart. At the same time, the digestive system provides nutrients to the heart muscle and vascular tissue to support their functioning. Hormones secreted by several endocrine glands, as well as endocrine cells of the pancreas, the stomach, and the small intestine, contribute to the control of digestion and nutrient metabolism. Contribution of Other Body Systems to the Digestive System Body Benefits received by the digestive system system Cardiovascular Blood supplies digestive organs with oxygen and processed nutrients Endocrine Endocrine hormones help regulate secretion in digestive glands and accessory organs Table 23. Accessory digestive organs comprise the second group and are critical for orchestrating the breakdown of food and the assimilation of its nutrients into the body. Between those two points, the canal is modified as the pharynx, esophagus, stomach, and small and large intestines to fit the functional needs of the body. Both the mouth and anus are open to the external environment; thus, food and wastes within the alimentary canal are technically considered to be outside the body. Only through the process of absorption do the nutrients in food enter into and nourish the body’s “inner space. Within the mouth, the teeth and tongue begin mechanical digestion, whereas the salivary glands begin chemical digestion. Once food products enter the small intestine, the gallbladder, liver, and pancreas release secretions—such as bile and enzymes—essential for digestion to continue. Together, these are called accessory organs because they sprout from the lining cells of the developing gut (mucosa) and augment its function; indeed, you could not live without their vital contributions, and many significant diseases result from their malfunction.

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If your sight is poor discount claritin 10 mg amex, an eye doctor who is an expert in low vision may be able to give you glasses or other devices that can help you use your limited vision more fully 10mg claritin with amex. You may want to ask your health care provider about support groups and job training for people with poor vision buy claritin 10mg mastercard. A recent study shows that controlling your blood glucose can prevent or delay the onset of kidney disease. When the kidneys fail, a person has to have his or her blood fltered through a machine (a treatment called dialysis) several times a week or has to get a kidney transplant. If the tests show microalbumin in the urine or if your Work with your health care kidney function isn’t provider to prevent or treat normal, you’ll need to kidney problems. Protecting Your Kidneys Keep Your Blood Glucose Under Control High blood glucose can damage your kidneys as time goes by. Know the Effects of Some Medicines and X-Ray Dyes If you have kidney disease, ask your health care provider about the possible effects that some medicines and X-ray dyes can have on your kidneys. You’re more likely to have heart and blood vessel problems if you smoke cigarettes, have high blood pressure, or have too much cholesterol or other fats in your blood. Talk with your health care team about what you can do to lower your risk for heart and blood vessel problems. Signs of Heart and Blood Vessel Problems If you feel dizzy, have sudden loss of sight, slur your speech, or feel numb or weak in one arm or leg, you may be having serious heart and blood vessel  problems. Danger signs of circulation problems to the heart include chest pain or pressure, shortness of breath, swollen ankles, or irregular heartbeats. Signs of circulation problems to your legs are pain or cramping in your buttocks, thighs, or calves during physical activity. Preventing and Controlling Heart and Blood Vessel Problems Eat Right and Get Physical Activity Choose a healthy diet, low in salt. See pages 14–18 to read more about If you’re overweight, talk with healthy choices for food your dietitian about how to safely lose weight. When you have diabetes and also use tobacco, the risk of heart and blood vessel problems is even greater. One of the best choices you can make for your health is to never start smoking—or if you smoke, to quit. If your cholesterol is higher than 200 mg/dL on two or more checks, you can do several things to lower it. You can work with your health care team to improve your blood glucose control, you can lose weight (if you’re overweight), and you can cut down on foods that are high in fat and cholesterol. Some Signs of Diabetic Nerve Damage Some signs of diabetic nerve damage are pain, burning, tingling, or loss of feeling in the feet and hands. It can cause you to sweat abnormally, make it hard for you to tell when your blood glucose is low, and make you feel light-headed when you stand up. Having trouble telling your glucose is low Nerve damage can lead may be a sign of nerve to other problems. Nerve damage can also cause bowel problems, make it hard to urinate, cause dribbling  with urination, and lead to bladder and kidney infections. For example, men can have trouble keeping their penis erect, a problem called impotence Tell your health care provider (erectile dysfunction). Protecting Your Nerves from Damage Keep Your Blood Glucose in Control High blood glucose can damage your nerves as time goes by. Have a Physical Activity Plan Physical activity or exercise may help keep some nerves healthy, such as those in your feet. Ask your health care provider to check your At least once a year, your health care provider should do a feet at each visit. For more information on foot care, call the National Diabetes Information Clearinghouse at 1-800-860-8747. Check Your Feet for Changes If you’ve lost feeling in your feet, you’ll need to take special care of them. Sometimes nerve damage can deform or misshape your feet, causing pressure points that can turn into blisters, sores, or ulcers. Blisters, sores, ulcers, infected corns, and ingrown toenails need to be seen by your health care provider or foot doctor (podiatrist) right away. Protecting Your Feet Get Your Health Care Provider to Check Your Feet at Least  Times a Year Ask your health care provider to look at your feet at least 4 times a year. If you have nerve damage, deformed or misshaped feet, or a circulation problem, your feet need special care. Trim Your Toenails Carefully Trim your toenails after you’ve washed and dried your feet—the nails will be softer and safer to cut. If you can’t see well, or if your nails are thick or yellowed, get them trimmed by a foot doctor or another health care provider. Wear shoes and socks when you walk on hot surfaces, such as beaches or the pavement around swimming pools. For more information on foot care, call the National Diabetes Information Clearinghouse at 1-800-860-8747. Keeping your blood Healthy teeth and gums glucose under control is also depend on regular care important. Signs of Dental Disease Sore, swollen, and red gums that bleed when you brush your teeth are a sign of a dental problem called gingivitis. To help keep bacteria from growing on your toothbrush, rinse it after each brushing and store it Protect your teeth upright with the bristles by brushing twice at the top. Floss Your Teeth Daily Besides brushing, you need to foss between your teeth each day to help remove plaque, a flm that forms on teeth and can cause tooth problems. Your dentist or dental hygienist will help you choose a good method to remove plaque, such as dental foss, bridge cleaners, or water spray. If you don’t have a dentist, fnd one or ask your health care provider for the name of a dentist in your community. Signs of the fu may include sudden high fever, chills, body aches, sore throat, runny nose, dry cough, and headache. It can cause serious infections of the lungs (pneumonia), the blood (bacteremia), and the covering of the brain (meningitis). Most people get Td toxoid as part of their routine childhood vaccinations, but all adults need a Td booster shot every 10 years. Keep your vaccination records up-to-date so you and your health care provider will know what vaccines you may need. You can protect your If you don’t want to baby and yourself by controlling your blood become pregnant, talk with glucose before and during your health care provider pregnancy. Protecting Your Baby and Yourself Keeping your glucose levels near normal before and during pregnancy can help protect you and your baby. Work with your diabetes care team to get and keep your blood glucose in the normal or near-normal range before you become pregnant. Your glucose records and your A1C test results will show when you have maintained a safe range for a period of time. You may need to change your meal plan and your usual physical activity, and you may need to take more frequent insulin shots. This condition, which is called gestational diabetes, can be controlled just like other kinds of diabetes.

It is produced in the lungs but binds to the surfaces of endothelial cells in the afferent arterioles and glomerulus purchase claritin 10mg with visa. It acts systemically to cause vasoconstriction as well as constriction of both the afferent and efferent arterioles of the glomerulus cheap 10mg claritin with amex. Its release is usually stimulated by decreases in blood pressure buy 10 mg claritin with mastercard, and so the preservation of adequate blood pressure is its primary role. At the + + same time that aldosterone causes increased recovery of Na , it also causes greater loss of K. It binds to the aldosterone receptor and weakly stimulates Na reabsorption and increased water recovery. It may cause increased retention of water during some periods of the menstrual cycle in women when progesterone levels increase. It promotes the recovery of water, decreases urine volume, and maintains plasma osmolarity and blood pressure. It does so by stimulating the movement of aquaporin proteins into the apical cell membrane of principal cells of the collecting ducts to form water channels, allowing the transcellular movement of water from the lumen of the collecting duct into the interstitial space in the medulla of the kidney by osmosis. On the other hand, in people with diabetic kidney disease, endothelin is chronically elevated, resulting in sodium retention. Natriuretic Hormones Natriuretic hormones are peptides that stimulate the kidneys to excrete sodium—an effect opposite that of aldosterone. The retention of phosphate would result in the formation of calcium phosphate in the plasma, reducing ++ ++ circulating Ca levels. Blood volume is important in maintaining sufficient blood pressure, and there are nonrenal mechanisms involved in its preservation, including vasoconstriction, which can act within seconds of a drop in pressure. Thirst mechanisms are also activated to promote the consumption of water lost through respiration, evaporation, or urination. Volume-sensing Mechanisms The body cannot directly measure blood volume, but blood pressure can be measured. Blood pressure often reflects blood 1234 Chapter 25 | The Urinary System volume and is measured by baroreceptors in the aorta and carotid sinuses. When blood pressure increases, baroreceptors send more frequent action potentials to the central nervous system, leading to widespread vasodilation. Due to its structural similarity to aldosterone, progesterone binds + to the aldosterone receptor in the collecting duct of the kidney, causing the same, albeit weaker, effect on Na and water retention. In cases of high blood pressure, diuretics may be prescribed to reduce blood volume and, thereby, reduce blood pressure. An example is the indigestible sugar mannitol, which is most often administered to reduce brain swelling after head injury. In cases of poorly controlled diabetes mellitus, glucose levels exceed the capacity of the tubular glucose symporters, resulting in glucose in the urine. Classically, in the days before glucose could be detected in the blood and urine, clinicians identified diabetes mellitus by the three Ps: polyuria (diuresis), polydipsia (increased thirst), and polyphagia (increased hunger). It plays a larger role in the osmolarity of the plasma than + any other circulating component of the blood. If there is too much Na present, either due to poor control or excess dietary consumption, a series of metabolic problems ensue. Over a long period, this increases the risk of serious complications such as heart attacks, strokes, and aneurysms. When more Na is reabsorbed, more K is secreted; when + + less Na is reabsorbed (leading to excretion by the kidney), more K is retained. When aldosterone causes a recovery of + + – Na in the nephron, a negative electrical gradient is created that promotes the secretion of K and Cl into the lumen. Its close association with + Na in the extracellular environment makes it the dominant anion of this compartment, and its regulation closely mirrors + that of Na. In the collecting ducts, the apical surfaces of intercalated cells have + proton pumps that actively secrete H into the luminal, forming urine to remove it from the body. Regulation of Nitrogen Wastes Nitrogen wastes are produced by the breakdown of proteins during normal metabolism. Proteins are broken down into amino acids, which in turn are deaminated by having their nitrogen groups removed. Human urinary wastes typically contain primarily urea with small amounts of ammonium and very little uric acid. Large drug molecules such as heparin or those that are bound to plasma proteins cannot be filtered and are not readily eliminated. Some drugs can be eliminated by carrier proteins that enable secretion of the drug into the tubule lumen. There are specific carriers that eliminate basic (such as dopamine or histamine) or acidic drugs (such as penicillin or indomethacin). As is the case with other substances, drugs may be both filtered and reabsorbed passively along a concentration gradient. Activated vitamin D is important for absorption of ++ ++ Ca in the digestive tract, its reabsorption in the kidney, and the maintenance of normal serum concentrations of Ca and phosphate. Calcium is vitally important in bone health, muscle contraction, hormone secretion, and neurotransmitter release. Deficits may also result in problems with cell proliferation, neuromuscular function, blood clotting, and the inflammatory response. Recent research has confirmed that vitamin D receptors are present in most, if not all, cells of the body, reflecting the systemic importance of vitamin D. If you move to a higher altitude, the partial pressure of oxygen is lower, meaning there is less pressure to push oxygen across the alveolar membrane and into the red blood cell. Normally, all of the glucose is recovered, but loss of glucose control (diabetes mellitus) may result in an osmotic dieresis severe enough to produce severe dehydration and death. A loss of renal function means a loss of effective vascular volume control, leading to hypotension (low blood pressure) or hypertension (high blood pressure), which can lead to stroke, heart attack, and aneurysm formation. Severe hypo-osmolarity can cause problems like lysis (rupture) of blood cells or widespread edema, which is due to a solute imbalance. Inadequate solute concentration (such as protein) in the plasma results in water moving toward an area of greater solute concentration, in this case, the interstitial space and cell cytoplasm. If the kidney glomeruli are damaged by an autoimmune illness, large quantities of protein may be lost in the urine. The resultant drop in serum osmolarity leads to widespread edema that, if severe, may lead to damaging or fatal brain swelling. Severe hypertonic conditions may arise with severe dehydration from lack of water intake, severe vomiting, or uncontrolled diarrhea. When the kidney is unable to recover sufficient water from the forming urine, the consequences may be severe (lethargy, confusion, muscle cramps, and finally, death). Failure of K regulation can have serious consequences on nerve conduction, skeletal muscle function, and most significantly, on cardiac muscle contraction and rhythm. Move the pH away from the optimum for a specific enzyme and you may severely hamper its function throughout the body, including hormone binding, central nervous system signaling, or myocardial contraction.

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