Sperm make up only 5 percent of the final volume of semen trusted 100 mg kamagra gold erectile dysfunction treatment in kenya, the thick purchase kamagra gold 100mg line erectile dysfunction in diabetes patients, milky fluid that the male ejaculates. The bulk of semen is produced by three critical accessory glands of the male reproductive system: the seminal vesicles, the prostate, and the bulbourethral glands. Seminal Vesicles As sperm pass through the ampulla of the ductus deferens at ejaculation, they mix with fluid from the associated seminal vesicle (see Figure 27. The fluid, now containing both sperm and seminal vesicle secretions, next moves into the associated ejaculatory duct, a short structure formed from the ampulla of the ductus deferens and the duct of the seminal vesicle. It excretes an alkaline, milky fluid to the passing seminal fluid—now called semen—that is critical to first coagulate and then decoagulate the semen following ejaculation. The temporary thickening of semen helps retain it within the female reproductive tract, providing time for sperm to utilize the fructose provided by seminal vesicle secretions. When the semen regains its fluid state, sperm can then pass farther into the female reproductive tract. Mild to moderate symptoms are treated with medication, whereas severe enlargement of the prostate is treated by surgery in which a portion of the prostate tissue is removed. Aggressive forms of prostate cancer, in contrast, involve metastasis to vulnerable organs like the lungs and brain. Prostate cancer is detected by a medical history, a blood test, and a rectal exam that allows physicians to palpate the prostate and check for unusual masses. If a mass is detected, the cancer diagnosis is confirmed by biopsy of This OpenStax book is available for free at http://cnx. Bulbourethral Glands The final addition to semen is made by two bulbourethral glands (or Cowper’s glands) that release a thick, salty fluid that lubricates the end of the urethra and the vagina, and helps to clean urine residues from the penile urethra. The fluid from these accessory glands is released after the male becomes sexually aroused, and shortly before the release of the semen. It is important to note that, in addition to the lubricating proteins, it is possible for bulbourethral fluid to pick up sperm already present in the urethra, and therefore it may be able to cause pregnancy. When erect, the stiffness of the organ allows it to penetrate into the vagina and deposit semen into the female reproductive tract. The shaft is composed of three column-like chambers of erectile tissue that span the length of the shaft. The corpus spongiosum, which can be felt as a raised ridge on the erect penis, is a smaller chamber that surrounds the spongy, or penile, urethra. The end of the penis, called the glans penis, has a high concentration of nerve endings, resulting in very sensitive skin that influences the likelihood of ejaculation (see Figure 27. The skin from the shaft extends down over the glans and forms a collar called the prepuce (or foreskin). The foreskin also contains a dense concentration of nerve endings, and both lubricate and protect the sensitive skin of the glans penis. A surgical procedure called circumcision, often performed for religious or social reasons, removes the prepuce, typically within days of birth. Penile erections are the result of vasocongestion, or engorgement of the tissues because of more arterial blood flowing into the penis than is leaving in the veins. The rapid increase in blood volume fills the erectile chambers, and the increased pressure of the filled chambers compresses the thin- walled penile venules, preventing venous drainage of the penis. The result of this increased blood flow to the penis and reduced blood return from the penis is erection. Depending on the flaccid dimensions of a penis, it can increase in size slightly or greatly during erection, with the average length of an erect penis measuring approximately 15 cm. These physical and emotional conditions can lead to interruptions in the vasodilation pathway and result in an inability to achieve an erection. The trial showed that the drug was not effective at treating heart conditions, but many men experienced erection and priapism (erection lasting longer than 4 hours). Importantly, men with health problems—especially those with cardiac disease taking nitrates—should avoid Viagra or talk to their physician to find out if they are a candidate for the use of this drug, as deaths have been reported for at-risk users. The alternate term for Leydig cells, interstitial cells, reflects their location between the seminiferous tubules in the testes. In male embryos, testosterone is secreted by Leydig cells by the seventh week of development, with peak concentrations reached in the second trimester. This early release of testosterone results in the anatomical differentiation of the male sexual organs. They increase during puberty, activating characteristic physical changes and initiating spermatogenesis. Functions of Testosterone The continued presence of testosterone is necessary to keep the male reproductive system working properly, and Leydig cells produce approximately 6 to 7 mg of testosterone per day. Testicular steroidogenesis (the manufacture of androgens, including testosterone) results in testosterone concentrations that are 100 times higher in the testes than in the circulation. Maintaining these normal concentrations of testosterone promotes spermatogenesis, whereas low levels of testosterone can lead to infertility. In addition to intratesticular secretion, testosterone is also released into the systemic circulation and plays an important role in muscle development, bone growth, the development of secondary sex characteristics, and maintaining libido (sex drive) in both males and females. In females, the ovaries secrete small amounts of testosterone, although most is converted to estradiol. Control of Testosterone The regulation of testosterone concentrations throughout the body is critical for male reproductive function. The intricate interplay between the endocrine system and the reproductive system is shown in Figure 27. The hypothalamus and the pituitary gland in the brain integrate external and internal signals to control testosterone synthesis and secretion. These polypeptide hormones correlate directly with Sertoli cell function and sperm number; inhibin B can be used as a marker of spermatogenic activity. The resulting reduction in circulating testosterone concentrations can lead to symptoms of andropause, also known as male menopause. While the reduction in sex steroids in men is akin to female menopause, there is no clear sign—such as a lack of a menstrual period—to denote the initiation of andropause. Instead, men report feelings of fatigue, reduced muscle mass, depression, anxiety, irritability, loss of libido, and insomnia. A reduction in spermatogenesis resulting in lowered fertility is also reported, and sexual dysfunction can also be associated with andropausal symptoms. Whereas some researchers believe that certain aspects of andropause are difficult to tease apart from aging in general, testosterone replacement is sometimes prescribed to alleviate some symptoms. Recent studies have shown a benefit from androgen replacement therapy on the new onset of depression in elderly men; however, other studies caution against testosterone replacement for long-term treatment of andropause symptoms, showing that high doses can sharply increase the risk of both heart disease and prostate cancer. Unlike its male counterpart, the female reproductive system is located primarily inside the pelvic cavity (Figure 27. External Female Genitals The external female reproductive structures are referred to collectively as the vulva (Figure 27. The labia majora (labia = “lips”; majora = “larger”) are folds of hair-covered skin that begin just posterior to the mons pubis. The thinner and more pigmented labia minora (labia = “lips”; minora = “smaller”) extend medial to the labia majora. Although they naturally vary in shape and size from woman to woman, the labia minora serve to protect the female urethra and the entrance to the female reproductive tract.
As one molecule of glucose gives rise to two molecules of pyruvate by glycolysis purchase kamagra gold 100mg amex impotence with antihypertensives, intermediates of citric acid cycle also result as two molecules buy 100mg kamagra gold with mastercard best erectile dysfunction drug review. The frst reaction of the pentose phosphate pathway is the dehydrogenation of glucose 6-phosphate by glucose 6-phosphate dehydrogenase to form 6-phosphoglucono d-lactone. Glycogenesis is a very essential process since the excess of glucose is converted and stored up as glycogen which could be utilised at the time of requirement. In the absence of this process the tissues are exposed to excess of glucose immediately after a meal and they are starved of it at other times. Step 1 The frst step in the breakdown of glycogen is catalyzed by two enzymes which act independently. The frst enzyme, namely glycogen phosphorylase with inorganic phosphate catalyses the cleavage of a terminal a 1-4 bond of glycogen to produce glycogen with one molecule less and a molecule of glucose 1-phosphate. This is carried out by another enzyme called the debranching enzyme (a 1-6 glucosidase) which hydrolyses these bonds and thus make more a 1-4 linkage accessible to the action of glycogen phosphorylase. The combined action of glycogen phosphorylase and the debranching enzyme converts glycogen to glucose 1-phosphate. Glucose 6-phosphatase removes phosphate group from glucose 6-phosphate enabling the free glucose to diffuse from the cell into the extra cellular spaces including blood. It usually occurs when the carbohydrate in the diet is insuffcient to meet the demand in the body, with the intake of protein rich diet and at the time of starvation, when tissue proteins are broken down to amino acids. In glycolysis, glucose is converted to pyruvate and in gluconeogenesis pyruvate is converted to glucose. Fructose 6-phosphate is formed from fructose 1,6-diphosphate by hydrolysis and the enzyme fructose 1,6-diphosphatase catalyses this reaction. Most of the glucogenic amino acids are converted to the intermediates of citric acid cycle either by transamination or deamination. Further metabolism of glycerol does not take place in the adipose tissue because of the lack of glycerol kinase necessary to phosphorylate it. Instead, glycerol passes to the liver where it is phosphorylated to glycerol 3-phosphate by the enzyme glycerol kinase. Hence, glycogen stored up in the muscle is converted into lactic acid by glycogenolysis followed by anaerobic glycolysis and thus lactate gets accumulated in the muscle. Muscle tissue lacks the enzyme glucose 6-phosphatase hence it is incapable of synthesizing glucose from lactic acid and the conversion take place only in the liver. In the liver lactate is oxidised to pyruvate which undergoes the process of gluconeogenesis resulting in the resynthesis of glucose. The glycogen may be once again converted to glucose (glycogenolysis) and may be recycled to the muscle through the blood. The process of gluconeogenesis completes the cycle by converting glucose once again to muscle glycogen. So the word diabetes milletus refers to chronic excretion of large volume of urine containing glucose. Diabetes mellitus, caused by a defciency in the secretion or action of insulin, is a relatively common disease. Diabetes mellitus is really a group of diseases in which the regulatory activity of insulin is defective. Type one requires insulin therapy and careful, life long control of the balance between glucose intake and insulin dose. Decreased permeability of the cell membrane for glucose resulting in the accumulation of glucose in the blood. The diabetic has voracious appetite, but inspite of over eating, they lose weight and become lean and emaciated. As glucose is not enough for energy production, increased mobilisation of fat from adipose tissue occurs. But the metabolism of fat is incomplete resulting in the production of large amounts of the intermediary products of fat metabolism namely ketone bodies (eg. Biochemical measurements on the blood and urine are essential in the diagnosis and treatment of diabetes, which causes profound changes in metabolism. The blood glucose concentration is measured before the test dose and at 30 min intervals for several hours thereafter. A normal individual assimilates the glucose readily, the blood glucose rising to no more than about 80 to 120 mg/100 ml; little or no glucose appears in the urine. Diabetic individuals assimilate the test dose of glucose poorly; their blood glucose level far exceeds the kidney threshold (about 180 mg/100ml), causing glucose to appear in their urine. Which one of the following enzyme is involved in substrate level phosphorylation i) citrate synthase ii) isocitrate dehydrogenase iii) succinyl CoA synthetase iv) fumarase f. The bonding is catalysed by the enzyme peptidyl transferase which is present in 50s ribosomal subunit. A peptide bond is formed between the third amino acid of site-A and the second amino acid of the dipeptide present in the P-site. The elongation of polypeptide chain is brought about by a number of protein factors called elongation factors. The reactions of deamination and transamination bring about the formation of keto acids which can undergo a further series of changes. Inter- conversion between keto acids and amino acids results in the synthesis of many nutritionally non essential amino acids. During protein synthesis the amino acids are absorbed from the blood, as the liver does not store them. Most of the amino acids are converted to a-keto acids by the removal of nitrogen in the form of ammonia which is quickly transformed into urea or it gets incorporated into some other amino acids. This is the mechanism where in the amino acids lose two hydrogen atoms (dehydrogenation) to form keto acids and ammonia. Oxidative deamination is accompanied by oxidation and is catalysed by specifc amino acid oxidases or more appropriately, dehydrogenases present in liver and kidneys. The imino acid then undergoes the second step, namely hydrolysis which results in a keto acid and ammonia. Transamination The process of transfer of an amino group from an amino acid to an a-keto acid, resulting in the formation of a new amino acid and keto acid is known as transamination. Transmethylation The transfer of methyl group from one compound to another is called transmethylation and the enzymes involved in the transfer are known as transmethylases. By this process various important, physiologically active compounds such as epinephrine, creatine, thymine and choline are synthesised in the body. Active Methionine + Norepinephrine → Epinephrine Active Methionine + Nictoinamide → N-methyl nicotinamide Active Methionine + Uracil → Thymine Active Methionine + Guanido acetate → Creatine (Methyl group donor) (Methyl group acceptor) Active methionine contains S-methyl bond which is a high energy bond and hence methyl group is liable and can be easily transferred to a methyl group acceptor. Catabolism of the carbon skeleton of amino acids The carbon skeletons left behind after deamination are identifed as a-keto acids. Synthesis of amino acids They may get reductively aminated by reversal of transdeamination or undergo transamination to form once again the original amino acids.
S. Hjalte. Roger Williams University.