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These effects cheap 25mg viagra super active amex losartan causes erectile dysfunction, however buy viagra super active 25 mg with amex erectile dysfunction ginkgo biloba, can lead to digitalis tox- icity when the cell gains so much calcium that the capacity of the sarcoplasmic and sarcolemmal binding sites is ex- ceeded. At this point, the mitochondria begin to take up the excess calcium; however, too much mitochondrial cal- FIGURE 10. When con- ATP needs already increased by enhanced contractility, is tractility is increased, the rate of rise of force is increased, the time less able to pump out accumulated calcium, and the final re- to afterload force is decreased, and potential force is increased. The muscle shortens faster and further (A) while isometric relaxation sult is a lowering of metabolic energy stores and a reduction (B) and relengthening (C) are minimally affected (D). Some changes in the contractility of car- diac muscle may be permanent and life threatening. Many of these changes are due to disease or factors external to the chondria of cardiac muscle (12) are also capable of accumulat- heart and may be described by the general term cardiomy- ing and releasing calcium, although this system does not ap- opathy (see Clinical Focus Box 10. Sources of Energy for Cardiac Muscle Function Calcium and the Function of Inotropic Agents. Inotropic agents usually work through changes in the internal cal- In contrast to skeletal muscle, cardiac muscle does not cium content of the cell. An increase in the heart rate, for have the opportunity to rest from a period of intense ac- instance, allows more separate influxes of calcium per tivity to “pay back” an oxygen debt. As a result, the me- minute, and the amount of releasable calcium in the subsar- tabolism of cardiac muscle is almost entirely aerobic un- colemmal space and SR increases. More crossbridges are der basal conditions and uses free fatty acids and lactate as activated, and the force of isometric contraction (and other its primary substrates. There is a tendency for the curves to converge at the lower A, Decreased starting length (with constant contractility) produces forces. B, Increased contractility produces increased velocity of lower velocities of shortening at a given afterload. Because of the shortening at a constant muscle length, but there is no tendency for presence of resting force (characteristic of heart muscle), it is impos- the curves to converge at the low forces. Under conditions of hypoxia (lack of oxygen), the anaerobic component of the metab- olism may approach 10% of the total, but beyond that limit, the supply of metabolic energy is insufficient to sus- tain adequate function. The substrates that provide chemical energy input to the heart during periods of increased activity consist of carbo- hydrates (mostly in the form of lactic acid produced as a re- sult of skeletal muscle exercise; see Chapters 8 and 9), fats (largely as free fatty acids), and, to a small degree, ketone body acids and amino acids. The relative amounts of the various metabolites vary according to the nutritional status of the body. Because of the highly aerobic nature of cardiac muscle metabolism, there is a strong correlation between the amount of work performed and the amount of oxygen consumed. Under most conditions, the contraction of car- diac muscle in the intact heart is approximately 20% effi- cient, with the remainder of the energy going to other cel- lular processes or wasted as heat. Regardless of the dietary or metabolic source of energy, ATP (as in all other muscle types) provides the immediate energy for contraction. As in The paths of calcium in and out of the car- skeletal muscle, cardiac muscle contains a “rechargeable” FIGURE 10. While some of these are occur at the subcellular level by interfering with energy related to problems with the valves or the electrical con- metabolism while producing little apparent structural dis- duction system (see Chapters 13 and 14), many are due to ruption. Such conditions, which can usually only be diag- malfunctions of the cardiac muscle itself. These condi- nosed by direct muscle biopsy, are difficult to treat effec- tions, called cardiomyopathy, result in impaired heart tively, although spontaneous recovery can occur. In hypertrophic cardiomyopathy, trypanosome (Chagas’ disease) can produce chronic car- an enlargement of the cardiac muscle fibers occurs be- diomyopathy. The tick-borne spirochete infection called cause of a chronic overload, such as that caused by hyper- Lyme disease can cause heart muscle damage and lead tension or a defective heart valve. Such muscle may fail to heart block, a conduction disturbance (see Chapter 13). An acute ischemic episode may be fol- diac muscle so weakened that it cannot pump strongly lowed by a stunned myocardium, with reduced me- enough to empty the heart properly with each beat. Chronic ischemia can produce a hi- strictive cardiomyopathy, the muscle becomes so stiff- bernating myocardium, also with reduced mechanical ened and inextensible that the heart cannot fill properly be- performance. Chronic poisoning with heavy metals, such as dling, which can lead to destructively high levels of inter- cobalt or lead, can produce toxic cardiomyopathy.

Inadequate Bone Mineralization Initially this occurs at an approximately equivalent rate purchase viagra super active 25 mg with amex impotence due to diabetes, Osteomalacia and rickets are characterized by the inade- but women begin to experience a more rapid bone min- quate mineralization of new bone matrix generic 50mg viagra super active amex erectile dysfunction drugs cost comparison, such that the ra- eral loss at the time of menopause (about age 45 to 50). As a result, bones This loss appears to result from the decline in estrogen may have reduced strength and are subject to distortion in secretion that occurs at menopause. When the disease occurs in supplementation of postmenopausal women is usually ef- adults, it is called osteomalacia; when it occurs in children, fective in retarding bone loss without causing adverse ef- it is called rickets. This condition of increased bone loss in women af- a bowing of the long bones in the legs. In adults, it is often ter menopause is called postmenopausal osteoporosis associated with severe bone pain. These on target tissues receptor defects changes can be roughly extrapolated into changes in bone mass Uremia and bone strength CHAPTER 36 Endocrine Regulation of Calcium, Phosphate, and Bone Metabolism 645 CLINICAL FOCUS BOX 36. As a result of its ability to interact with bone 17 -estradiol is a major contributing factor in the develop- cells and their precursors to regulate local paracrine sig- ment of osteoporosis in postmenopausal women. Until re- naling mechanisms, estradiol produces anti-osteoporotic cently, specific mechanisms by which estradiol might in- effects in bone. Recent When estradiol is present, as in a premenopausal state, studies suggest that estradiol influences the production it acts as a governor to reduce cytokine production and and/or modulates the activity of several cytokines involved limit osteoclast activity. Osteoclast-mediated bone resorption involves Current research efforts attempt to define more two processes: the activation of mature, functional osteo- clearly the specific source(s) and roles of the cytokines clasts and the recruitment and differentiation of osteoclast involved. In addition to PTH, the cytokines interleukin-1 the development of diagnostic tools, such as the assess- (IL-1) and tumor necrosis factor (TNF) are involved in the ment of cytokine levels, to monitor osteoporosis. The primary cause of osteomalacia and rickets is a defi- Paget’s Disease Leads to ciency in vitamin D activity. Vitamin D may be deficient in Disordered Bone Formation the diet; it may not be adequately absorbed by the small in- testine; it may not be converted into its hormonally active Paget’s disease affects about 3% of people older than 40. It form; or target tissues may not adequately respond to the is typified by disordered bone formation and resorption (re- active hormone (Table 36. Dietary deficiency is gener- modeling) and may occur at a single local site or at multiple ally not a problem in the United States, where vitamin D is sites in the body. Radiographs of affected bone often exhibit added to many foods; however it is a major health problem increased density, but the abnormal structure makes the in other parts of the world. Often those with Paget’s disease are involved in converting vitamin D3 into its hormonally experience considerable pain, and in severe cases, crippling active form, primary disease of either of these organs may deformities may lead to serious neurological complications. Impaired vitamin D actions The cause of the disease is not well understood. In netic and environmental factors (probably viral) appear to be particular, some anticonvulsants used in the treatment of important. Several therapies are available for treating the dis- epilepsy may produce osteomalacia or rickets with pro- ease, including treatment with CT, but these typically offer longed treatment. REVIEW QUESTIONS DIRECTIONS: Each of the numbered (B) 50% (D) Bile items or incomplete statements in this (C) 60% 4. Which of the following is ONE lettered answer or completion that is of calcium during a 24-hour period. What is the major route of calcium involved in formation of 1,25- excretion from the body? As part of a routine physical exam, a (A) Urine (A) Bone patient’s serum electrolyte levels were (B) Sweat (B) Skin measured. Among the measurements, it (C) Feces (C) Kidney was determined that total plasma (D) Bile (D) Liver calcium concentration was 10. A 42-year-old woman develops an What percentage of total plasma phosphate leaves the body is via the autoimmune disease that damages her calcium is normally present as the free (A) Urine kidneys. Male (C) 25-Hydroxycholecalciferol to Raise plasma calcium and phosphate skeletal health and osteoporosis. A 62-year-old woman stumbles on a (B) Lower plasma calcium and raise Griffin JE, Ojeda SR, eds. Textbook of En- crack in the sidewalk, falls, and breaks plasma phosphate docrine Physiology. She suffers from a form (C) Raise plasma calcium and lower Oxford University Press, 2000. The 25-hydroxyvitamin D 1 - there is an equivalent loss of bone hydroxylase.

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The lated from the arterial (Ca) and venous (Cv) blood concen- interstitial hydrostatic pressure ranges from slightly nega- tration as: tive to 8 to 10 mm Hg and purchase viagra super active 25mg mastercard iief questionnaire erectile function, in most organs generic viagra super active 100mg on-line injections for erectile dysfunction after prostate surgery, is substantially E (Ca Cv)/Ca (2) less than capillary pressure. CHAPTER 16 The Microcirculation and the Lymphatic System 269 The Osmotic Forces Developed by sue hydrostatic pressure is a filtration force when negative Plasma Proteins Oppose the Filtration and an absorption force when positive. The primary defense against excessive fluid filtration is Standing causes high capillary hydrostatic pressures from the colloid osmotic pressure, also called plasma oncotic gravitational effects on blood in the arterial and venous ves- pressure, generated by plasma proteins. Support stockings are too large to pass readily through the vast majority of compress the interstitial environment to raise hydrostatic water-filled pores of the capillary wall. In fact, more than tissue pressure and compress superficial veins, which helps 90% of these large molecules are retained in the blood lower venous pressure and, thereby, capillary pressure. Colloid osmotic pressure is conceptually similar to drostatic pressure becomes very negative and opposes fur- osmotic pressures for small molecules generated across se- ther fluid loss (Fig. If a substantial amount of water is lectively permeable cell membranes; both primarily de- added to the interstitial space, the tissue hydrostatic pres- pend on the number of molecules in solution. However, a margin of safety exists over a plasma protein that impedes filtration is serum albumin wide range of tissue fluid volumes (see Fig. The colloid osmotic pressure of plasma tissue volume exceeds a certain range, swelling or edema proteins is typically 18 to 25 mm Hg in mammals when occurs. In extreme situations, the tissue swells with fluid to measured using a membrane that prevents the diffusion of the point that pressure dramatically increases and strongly all large molecules. The ability of tissues to allow Colloid osmotic pressure offsets the capillary hydro- substantial changes in interstitial volume with only small static blood pressure to the extent that the net filtration changes in pressure indicates that the interstitial space is force is only slightly positive or negative. As a general rule, about 500 to 1,000 mL of pressure is sufficiently low, the balance of colloid osmotic fluid can be withdrawn from the interstitial space of the en- and hydrostatic pressures is negative, and tissue water is ab- tire body to help replace water losses due to sweating, diar- sorbed into the capillary blood. The balance of pressures is likely 1 to 2 The Balance of Filtration and Absorption Forces mm Hg in most organs. Regulates the Exchange of Fluid Between the Blood and the Tissues The Leakage of Plasma Proteins Into Tissues The role of hydrostatic and colloid osmotic pressures in de- Increases the Filtration of Fluid From the Blood termining fluid movement across capillaries was first postu- to the Tissues lated by the English physiologist Ernest Starling at the end of the nineteenth century. In the 1920s, the American A small amount of plasma protein enters the interstitial physiologist Eugene Landis obtained experimental proof space; these proteins and, perhaps, native proteins of the space generate the tissue colloid osmotic pressure. This pressure of 2 to 5 mm Hg offsets part of the colloid osmotic pressure in the plasma. This is, in a sense, a filtration pres- Edema sure that opposes the blood colloid osmotic pressure. As discussed earlier, the lymphatic vessels return plasma pro- teins in the interstitial fluid to the plasma. Normal Hydrostatic Pressure in Tissues Can Either 0 Favor or Oppose Fluid Filtration From the Blood to the Tissues The hydrostatic pressure on the tissue side of the endothe- Safe range Excessive volume lial pores is the tissue hydrostatic pressure. This pressure is determined by the water volume in the interstitial space Dehydration and tissue distensibility. Tissue hydrostatic pressure can be increased by external compression, such as with support Interstitial fluid volume stockings, or by internal compression, such as in a muscle FIGURE 16. The tissue hydrostatic pressure in vari- interstitial fluid volume is altered. If the interstitial fluid volume exceeds the “safe range,” ing normal hydration of the interstitial space and becomes high tissue hydrostatic pressures and edema will be present. The relationship is defined for a change occurs in both venules and capillaries. CFC values single capillary by the Starling-Landis equation: in tissues such as skeletal muscle and the small intestine are typically in the range of 0. JV is the net volume of fluid moving across the capillary The CFC replaces the hydraulic conductivity (Kh) and 3 wall per unit of time ( m /min). Kh is the hydraulic con- capillary surface area (A) in the Starling-Landis equation for ductivity for water, which is the fluid permeability of the filtration across a single capillary. Kh is expressed as m /min/( m of capillary fluid permeability, the surface area (determined by the surface area) per mm Hg pressure difference. For Kh increases up to 4-fold from the arterial to the venous end example, during the intestinal absorption of foodstuff, par- of a typical capillary. A is the vascular surface area, Pc is the ticularly lipids, both capillary fluid permeability and per- capillary hydrostatic pressure, and Pt is the tissue hydro- fused surface area increase, dramatically increasing CFC.

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At Veins of the Lower Extremity the level of the fifth lumbar vertebra 50 mg viagra super active for sale impotence guidelines, the right and left common The lower extremities viagra super active 50 mg fast delivery erectile dysfunction type of doctor, like the upper extremities, have both a iliacs unite to form the large inferior vena cava (fig. The deep veins accompany corresponding arteries and have more valves than do the superficial veins. Circulatory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 Chapter 16 Circulatory System 577 FIGURE 16. Circulatory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 578 Unit 6 Maintenance of the Body Inferior vena cava Right common iliac v. Circulatory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 Chapter 16 Circulatory System 579 The superficial veins of the lower extremity are the small soids). The right and left hepatic veins that drain the venous and great saphenous veins. The small saphenous vein arises blood from the liver and empty it into the inferior vena cava from the lateral side of the foot and ascends deep to the skin (fig. As a consequence of the hepatic portal system, the along the posterior aspect of the leg. It empties into the popliteal absorbed products of digestion must first pass through the liver vein, posterior to the knee. The great saphenous vein is the before entering the general circulation. It originates from the medial side of The hepatic portal vein is the large vessel that receives the foot and ascends along the medial aspect of the leg and thigh blood from the digestive organs. The great saphenous vein superior mesenteric vein, which drains nutrient-rich blood from is frequently excised and used as a coronary bypass vessel. If a su- the small intestine, and the splenic vein, which drains the perficial vein is removed, the venous return of blood from the ap- spleen. The splenic vein is enlarged because of a convergence of pendage is through the remaining deep veins. The right gastroepiploic vein, also from the stomach, drains directly into the superior mesenteric vein. The inferior vena cava parallels the abdominal aorta on the Three additional veins empty into the hepatic portal vein. As the inferior vena cava ascends through the abdomi- stances, such as alcohol, that are absorbed into the blood from the small intestine. However, excessive quantities of alcohol nal cavity, it receives tributaries from veins that correspond in cannot be processed during a single pass through the liver, and so a name and position to arteries previously described. Eventually, the liver is able to process Four paired lumbar veins (not shown) drain the posterior the alcohol as the circulating blood is repeatedly exposed to the liver abdominal wall, the vertebral column, and the spinal cord. Alcoholics may eventually suffer from cirrhosis of the liver as the normal liver tissue is destroyed. The right testicular vein in males (or the right In summary, it is important to note that the sinusoids of the ovarian vein in females) drains the corresponding gonads, and liver receive blood from two sources. The hepatic artery supplies the right suprarenal vein drains the right adrenal gland. These oxygen-rich blood to the liver, whereas the hepatic portal vein veins empty into the inferior vena cava. The left testicular vein transports nutrient-rich blood from the small intestine for process- (or left ovarian vein) and the left suprarenal vein, by contrast, ing. The inferior phrenic veins re- Liver cells exposed to this blood obtain nourishment from it and ceive blood from the inferior side of the diaphragm and empty are uniquely qualified (because of their anatomical position and into the inferior vena cava. Right and left hepatic veins origi- enzymatic ability) to modify the chemical nature of the venous nate from the capillary sinusoids of the liver and empty into the blood that enters the general circulation from the GI tract. Note that the inferior vena cava does not receive blood Knowledge Check directly from the GI tract, pancreas, or spleen. Instead, the ve- nous outflow from these organs first passes through capillaries in 21. Point out the vein that may bulge in the side of the neck when a person performs Valsalva’s maneuver and the vein that is com- Hepatic Portal System monly used as a site for venipuncture. Describe the positions, sources, and drainages of the small A portal system is a pattern of circulation in which the vessels and great saphenous veins.

The saclike scrotum buy 50 mg viagra super active with visa erectile dysfunction and diet, located in the the tubular structures on the testes where 4 cheap viagra super active 50mg overnight delivery erectile dysfunction estrogen. The glans penis is the terminal end, urogenital portion of the perineum, spermatozoa mature and are stored. Each testis is contained within its own ductus deferens forms a component of the and Ejaculation (pp. Erection of the penis occurs as the erectile from the other by the scrotal septum. The seminal vesicles and prostate provide tissue becomes engorged with blood. The testes are partitioned into wedge- (a) The seminal vesicles are located ejaculatory ducts, and ejaculation is the shaped lobules; the lobules are composed posterior to the base of the urinary forceful expulsion of semen from the of seminiferous tubules, which produce bladder; they secrete about 60% of the ejaculatory ducts and urethra of the penis. Spermatogenesis occurs by meiotic just below the urinary bladder; it with blood as arteriole flow increases and division of the cells that line the secretes about 40% of the additive venous drainage decreases. Ejaculation is the result of sympathetic (a) At the end of the first meiotic (c) Spermatozoa constitute less than 1% reflexes in the smooth muscles of the division, two secondary spermatocytes of the volume of an ejaculate. The perineum is fibers found within located at (a) a membranous covering over the (a) the scrotum. Male Reproductive © The McGraw−Hill Anatomy, Sixth Edition Development System Companies, 2001 724 Unit 7 Reproduction and Development (c) the ejaculatory duct 3. Describe the location and structure of the Critical-Thinking Questions (d) the ductus deferens scrotum. Spermatozoa are stored prior to emission regulate the position of the testes in the spermatogenesis. Discuss the function of the sustentacular using up all of the spermatogonia. List the structures that constitute the because it is not necessary for the survival (a) secrete mucus. Why is the inguinal canal however, the reproductive system does (c) secrete hormones. Diagram a spermatozoon and describe the features as well as bone structure. Describe the structure of the penis and tying and surgically removing a short (d) It is controlled by the hypothalamus explain the mechanisms that result in section of each ductus deferens within the of the brain and sacral portion of the erection, emission, and ejaculation. What develops male accessory sex organs consist of and what are its properties? If it takes only one sperm cell to fertilize (d) the absence of estrogens. Which of the following does not arise of the perineum of an embryo during the expelled during ejaculation? A number of pathogenic (disease-causing) (a) the epididymis with that of an adult male. List the structures of the male pathogen, why does coitus provide an (d) the prostate reproductive system that form from the ideal means of propagation? Female Reproductive © The McGraw−Hill Anatomy, Sixth Edition Development System Companies, 2001 Female Reproductive System 21 Introduction to the Female Reproductive System 726 Structure and Function of the Ovaries 728 Secondary Sex Organs 732 Mammary Glands 738 Ovulation and Menstruation 740 Developmental Exposition: The Female Reproductive System 743 CLINICAL CONSIDERATIONS 744 Clinical Case Study Answer 751 Chapter Summary 752 Review Activities 752 Clinical Case Study A 28-year-old female was brought to the emergency room following a 4-day history of moderate right-sided pelvic pain. On the morning of the fifth day the pain had become more severe, prompting her to seek medical attention. She complained of weakness and light-headedness, and stated that she hadn’t had a period for about 8 weeks. The consulting gynecologist said that a ruptured ectopic pregnancy was likely. He ordered a blood test, the results of which suggested that the patient had suffered a slight amount of hem- orrhage. A culdocentesis (needle sampling of the peritoneal cavity via the posterior vaginal wall) was positive for pooled blood. Briefly explain the se- quence of events leading up to the rupture of the ectopic pregnancy beginning with ovulation. Explain how blood from a ruptured ectopic preg- nancy can be aspirated through the vagina. FIGURE: Examining fetal structures for Hints: Carefully study the position of the uterus and uterine tubes with respect to the ovaries congenital problems, sampling fetal tissues for within the peritoneal cavity. Read about ectopic pregnancies in the clinical sections of this metabolic disorders, and conducting in utero chapter and refer to figure 22.

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