By H. Vasco. Walla Walla University. 2018.
Chemical carcinogens buy generic viagra professional 50 mg on line impotence 40 years, chemotherapeutic agents order viagra professional 50mg line erectile dysfunction pills generic, tibodies may exhibit some infertility problems. However, certain drugs, environmental toxins, irradiation, and ex- studies of men who have developed low or moderate levels of treme temperatures are factors that can reduce the number antisperm antibodies after vasectomy and who have had their of replicating germ cells or cause chromosomal abnormali- vasa deferens reconnected have normal fertility if the vasec- ties in individual cells. Vasectomy does not ap- 658 PART X REPRODUCTIVE PHYSIOLOGY pear to change hormone or sperm production by the testes. Divisions and Become Spermatids The mature spermatozoon exhibits a remarkable degree Spermatogonia undergo several rounds of mitotic division of structural and functional specialization well adapted to prior to entering the meiotic phase (see Fig. The cell is small, compact, and spermatogonia remain in contact with the Sertoli cells, mi- streamlined; it is about 1 to 2 m in diameter and can ex- grate away from the basal compartment near the walls of ceed 50 m in length in humans. It is packed with special- the seminiferous tubules and cross into the adluminal com- ized organelles and long axial fibers but contains only a few partment of the tubule (see Fig. After crossing into of the normal cytoplasmic constituents, such as ribosomes, the adluminal compartment, the cells differentiate into ER, and Golgi apparatus. It has a very prominent nucleus, a spermatocytes prior to undergoing meiosis I. The first mei- flexible tail, numerous mitochondria, and an assortment of otic division of primary spermatocytes gives rise to diploid proteolytic enzymes. The spermatozoon consists of three main parts: a head, a The second meiotic division produces haploid (1 set of middle piece, and a tail. The spermatids emanating from a primary spermatocyte, two haploid chromatin is transcriptionally inactive throughout contain X chromosomes and two have Y chromosomes the life of the sperm until fertilization, when the nucleus de- (see Fig. Because of the numerous mitotic divisions condenses and becomes a pronucleus. The acrosome con- and two rounds of meiosis, each spermatogonium com- tains proteolytic enzymes, such as hyaluronidase, acrosin, mitted to meiosis should have yielded 256 spermatids, if neuraminidase, phospholipase A, and esterases. The most frequent is Klinefelter’s syndrome, olytic action enables sperm to penetrate through the egg which causes hypogonadism and infertility in men. The middle piece contains spiral sheaths of mi- with this disorder have an accessory X chromosome caused tochondria that supply energy for sperm metabolism and lo- by meiotic nondisjunction. The tail is composed of a 9 2 arrangement of XXY, but there are other chromosomal mosaics. Testicular microtubules, which is typical of cilia and flagella, and is sur- volume is reduced more than 75% and ejaculates contain rounded by a fibrous sheath that provides some rigidity. Spermatogonic cell differentia- tail propels the sperm by a twisting motion, involving inter- tion beyond the primary spermatocyte stage is rare. The Formation of a Mature Spermatozoon Requires Extensive Cell Remodeling Testosterone Is Essential for Sperm Production and Maturation Spermatids are small, round, and nondistinctive cells. Dur- ing the second half of the spermatogenic cycle they un- Spermatogenesis requires high intratesticular levels of dergo considerable restructuring to form mature spermato- testosterone, secreted from the LH-stimulated Leydig cells. Notable changes include alterations in the nucleus, the The testosterone diffuses across the basement membrane of formation of a tail, and a massive loss of cytoplasm. The nu- the seminiferous tubule, crosses the blood-testis barrier, cleus becomes eccentric and decreases in size, and the and complexes with ABP. Sertoli cells some-like structure unique to spermatozoa, buds from the also contain FSH receptors. However, recent studies using Golgi apparatus, flattens, and covers most of the nucleus. The absolute requirement for FSH in sperm nine peripheral doublet microtubules surrounding a central production remains unknown. This becomes the axoneme or that testosterone may be sufficient for spermatogenesis. Throughout this reshaping The actions of FSH and testosterone at each point of process, the cytoplasmic content is redistributed and dis- sperm cell production are unknown. During spermiation, most of the remaining cyto- sis, spermatogenesis appears to depend on the availability plasm is shed in the form of residual bodies. In human males, FSH is thought The reasons for this lengthy and metabolically costly to be required for the initiation of spermatogenesis before process become apparent when the unique functions of puberty. Unlike other cells, the spermato- achieved, LH alone (through stimulation of testosterone zoon serves no apparent purpose in the organism. Its only production) or testosterone alone is sufficient to maintain function is to reach, recognize, and fertilize an egg; spermatogenesis. CHAPTER 37 The Male Reproductive System 659 TESTICULAR STEROIDOGENESIS hydrogenase), which substitutes the keto group in posi- tion 17 with a hydroxyl group.
A simple mastectomy is ever cheap viagra professional 50mg on line erectile dysfunction protocol scam or not, localized infections and inflammations do occur 50 mg viagra professional fast delivery erectile dysfunction treatment drugs. These are removal of the entire breast but not the underlying lymph nodes. The symptoms breast, the lymphatic drainage, and perhaps the pectoralis major of vaginitis are a discharge of pus (leukorrhea) and itching (pruri- muscle. The two most common organisms that cause vaginitis are the the pectoralis major muscle is always removed, as well as the pec- protozoan Trichomonas vaginalis and the fungus Candida albicans. Female Reproductive © The McGraw−Hill Anatomy, Sixth Edition Development System Companies, 2001 Chapter 21 Female Reproductive System 749 (a) (b) FIGURE 21. These contraceptives usually consist of a people, but the popularity of this technique has declined as more synthetic estrogen combined with a synthetic progesterone in successful methods of contraception have been introduced the form of pills that are taken once each day for 3 weeks after (fig. In the rhythm method, an attempt is made to pre- the last day of a menstrual period. This procedure causes an im- dict the day of the woman’s ovulation and restrict coitus to safe mediate increase in blood levels of ovarian steroids (from the times of the cycle that allow no chance for fertilization to occur. As a result of negative feedback inhibition of gonadotrophin temperature or by a change in mucous discharge from the vagina. The entire cycle is like a false This technique has one of the highest failure rates of any of the luteal phase, with high levels of progesterone and estrogen and widely used birth control methods, largely because women’s cy- low levels of gonadotrophins. Because the contraceptive pills contain ovarian steroid More popular methods of birth control include sterilization, hormones, the endometrium proliferates and becomes secretory, oral contraceptives, intrauterine devices (IUDs), and barrier just as it does during a normal cycle. In order to prevent an ab- methods—including condoms for the male and female and di- normal growth of the endometrium, women stop taking the pill aphragms for the female. This causes estrogen and progesterone levels to they vary with respect to safety,side effects,and degree of efficacy. The contraceptive pill is Sterilization techniques include vasectomy for the male and an extremely effective method of birth control, but it does have tubal ligation for the female. In the latter technique (which ac- potentially serious side effects—including an increased incidence counts for over 60% of sterilization procedures performed in the of thromboembolism and cardiovascular disorders. This is analo- pointed out, however, that the mortality risk associated with gous to the procedure performed on the ductus deferentia in a contraceptive pills is still much lower than the risk of death from vasectomy. Female Reproductive © The McGraw−Hill Anatomy, Sixth Edition Development System Companies, 2001 750 Unit 7 Reproduction and Development (a) (b) (c) (d) (e) (f) (g) (h) FIGURE 21. Female Reproductive © The McGraw−Hill Anatomy, Sixth Edition Development System Companies, 2001 Chapter 21 Female Reproductive System 751 Another way in which to deliver hormonal contraceptives signed to resist moisture, the patch releases a week’s worth of es- to a woman’s body is by means of a subdermal implant. They that fits into the uterine cavity where it slowly releases progestin are implanted just under the skin, usually on the upper arm, up to a five-year period. The contraceptive hormone gradually tives have fewer side effects than Depro-Provera, which has been leaches out through the walls of the rods and enters the blood- available since 1992. Intrauterine devices (IUDs) do not prevent ovulation, but instead prevent implantation of the blastocyst in the uterine wall in the event that fertilization occurs. The mechanisms by which their contraceptive effects are produced are not well un- Clinical Case Study Answer derstood but appear to involve their ability to cause inflamma- An ectopic pregnancy is any pregnancy that implants outside the uterine tory reactions in the uterus. Because The events leading up to our patient’s problem are as follows: An oocyte of the potential problems with IUDs, their use has diminished. Soon after it enters the tube, the oocyte is fertilized, creating a cal caps—are only slightly less effective than hormonal contra- zygote. Up to this point, the events are no different from those that ceptives or IUDs, but they do not have serious side effects. In the case of tubal pregnancy, however, Barrier contraceptives are most effective when they are used in the transporting ability of the uterine tube fails, causing the conceptus to be retained in the tube. Implantation then occurs within tissues that conjunction with spermicidal (sperm-killing) foams and gels. For example, the uterine tube does Many couples avoid them, however, because they detract from not expand well to accommodate a growing embryo, nor does it possess the spontaneity of sexual intercourse.
However viagra professional 50 mg erectile dysfunction doctor in pune, there is scepticism as to whether the brain can manufacture sufficient peptide to regulate the ubiquitous GABAA receptor on a moment-to-moment basis viagra professional 100mg discount erectile dysfunction doctors in utah. Currently, the binding of TTN to the peripheral benzodiazepine site, and its effect on neurosteroid synthesis, is attracting greater interest (Do Rego et al. Finally, the presence in human post-mortem brain tissue of the active metabolite of diazepam, desmethyldiazepam, raised some curiosity and frank alarm (Sangameswaran et al. At the time of its discovery in the brain it was thought that there was no enzyme system capable of producing such halogenated compounds and that its presence in the brain reflected dietary intake from an environment contaminated by overuse of its parent compound. However, its discovery in stored brain tissue which had been obtained before the synthesis of the benzodiazepines allayed these fears. It is now thought possible that some benzodiazepines, including desmethyl- diazepam, occur naturally and that they are taken in as part of a normal diet (Table 19. Although, by analogy with the opioids, one would expect there to be an endogenous ligand for the widely distributed benzodiazepine receptor, its existence remains uncertain and we must be alert to the possibility that any such ligand(s) could have either agonist or inverse agonist activity. Chrysin Wheat grain Diazepam, desmethyldiazepam, lormetazepam Potato Diazepam, desmethyldiazepam, lormetazepam Karmelitter Geist Amentoflavon 410 NEUROTRANSMITTERS, DRUGS AND BRAIN FUNCTION ENDOGENOUS LIGANDS AND BENZODIAZEPINE RECEPTORS: AN EXPLANATION FOR THE CAUSE OF ANXIETY The undisputed efficacy of benzodiazepines in relief of anxiety led to the question of whether this disorder could arise from abnormal concentrations in the brain of an endogenous ligand or a malfunction of the benzodiazepine/GABA receptor system. An important study, aimed at distinguishing between these possibilities, has been carried out in humans (Nutt et al. In this case, the administration of the antagonist, flumazenil, should induce anxiety in normal subjects and exacerbate anxiety in anxious patients. In this case, the administration of flumazenil should relieve anxiety in anxious patients and have no, or sedative, effects in healthy subjects. In this case, flumazenil (which normally has zero efficacy) should induce anxiety in anxious patients but have no effects in healthy subjects because they have normal receptors. To distinguish between these possibilities, flumazenil was administered to panic patients and control subjects. The results of the experiment were consistent with the third possibility: flumazenil induced panic attacks in 8 of 10 patients but not in control subjects (Fig. Unfortunately, the change(s) in the benzodiazepine receptor or its coupling to the rest of the GABAA receptor are unknown, as are the stimuli that could explain this functional change. Recent studies suggest that the binding of [11C]flumazenil is abnormally low in panic patients (Malizia et al. However, this is the only tested theory so far to connect panic anxiety directly with a disorder of the GABAA receptor. The receptor shift theory could also explain why benzodiazepines are ineffective in treating panic disorder but, because these drugs do effectively relieve generalised anxiety, it seems that the theory might explain the origin of the former, but not the latter disorder, and that they have different causes. He went on to stimulate the locus coeruleus of (chair- restrained) monkeys and showed that this caused behavioural changes, some of which resembled a cluster of behaviours displayed by the animals when under threat. This work led to the proposal that anxiety was due to (or exacerbated by) excessive ANXIETY 411 Figure 19. This proposes that patients with panic disorder have dysfunctional GABAA receptors such that the actions of drugs that behave as antagonists in normal subjects are expressed as inverse agonism in panic patients. It is unlikely that this theory extends to generalised anxiety disorder (GAD), for which benzodiazepine agonists are highly effective treatments, but it could explain why these drugs are relatively ineffective at treating panic disorder. This is an a2-adrenoceptor antagonist that increases the firing rate of, and release of noradrena- line from, noradrenergic neurons by blockade of presynaptic a2-adrenoceptors on the neuronal cell bodies and terminals, respectively. Increases in noradrenaline release, inferred from measurement of the noradrenaline metabolite, 3-methoxy, 4-hydroxy- phenylglycol (MHPG), in plasma, have shown that the noradrenergic response in panic patients who experience a panic attack with yohimbine is greater than that in either panic patients who do not express this response or in normal patients (Bremner et al. Unfortunately, the noradrenergic response to yohimbine is not exaggerated in patients with GAD, suggesting that the aetiology of this form of anxiety could differ from that of panic disorder. Nevertheless, the a2-adrenoceptor agonist, clonidine, which has the opposite effect to yohimbine on noradrenergic neurons, is sometimes used to relieve anxiety, especially that associated with alcohol and opiate withdrawal. However, it is not a viable long-term treatment for anxiety because of its effects on the cardio- vascular system. One complication with the above concept is that, in some brain regions, the majority of a2-adrenoceptors are postsynaptic and so a reduction in a2-adrenoceptor-mediated noradrenergic transmission, after treatment with yohimbine, cannot be ruled out as a causal factor for the anxiety induced by this drug.
The examination conﬁrms the difﬁculty cluded that the pattern of the boy’s venous sinuses is essentially swallowing buy cheap viagra professional 50 mg on-line erectile dysfunction medication online pharmacy, and reveals that the man’s voice is hoarse and gravely viagra professional 100mg free shipping erectile dysfunction young male, normal. Which of the following describes the usual pattern of the and that he is unable to elevate his left shoulder against resistance. Based on this man’s deﬁcits, (A) Always drains equally into the right and left transverse which of the following represents the most likely location of this sinuses thrombus? Which of the following vessels forms a characteristic loop in the Answers for Chapter 8 cisterna magna that is prominent on lateral angiograms and, in the process, supplies blood to the choroid plexus of the fourth ventri- 1. The pericallosal artery is located immediately superior to the (C) Posterior spinal artery corpus callosum and the frontopolar artery serves the medial as- (D) Superior cerebellar artery pect of the frontal lobe. The internal parietal arteries are the ter- (E) Vertebral artery minal branches of the pericallosal artery; these vessels distribute to the medial portion of the parietal lobe, the precuneus. The MRI of a 42-year-old man shows a small tumor in the choroid etooccipital artery is one of the terminal branches (part of P4) of plexus of the third ventricle. Which of the fol- lowing represents the blood supply to this portion of the choroid 2. In a small percentage of cases (B) Choroidal branches of AICA the ophthalmic artery may originate from other locations on the (C) Choroidal branches of PICA internal carotid artery, including its cavernous portion. This ves- (D) Lateral posterior choroidal artery sel does not originate from the petrous portion of the internal (E) Medial posterior choroidal artery carotid or from anterior or middle cerebral arteries. Answer C: The point at which the thalamostriate vein (also inating from the lateral aspect of the basilar bifurcation and ex- called the superior thalamostriate vein at this position) abruptly tending into the space between the posterior cerebral and superior turns 180 to form the internal cerebral vein is called the venous cerebellar arteries. This angle is located immediately caudal to the position of which of the following deﬁcits would most likely be seen in this the interventricular foramen and is, therefore, an important land- woman? The thalamostriate vein is located in the groove between the (A) Constriction of the ipsilateral pupil thalamus and the caudate nucleus. At the superior aspect of the (B) Inability to look down and out with the ipsilateral eye thalamus, this vein is the superior thalamostriate vein, and, on the (C) Inability to look laterally with the ipsilateral eye inferior surface, it is called the inferior thalamostriate vein. None (D) Inability to look up, down, or medially with the ipsilat- of the other choices is involved in the formation of the venous an- eral eye gle. Answer E: The superﬁcial middle cerebral vein is a compara- tively obvious venous structure on the lateral surface of the hemi- 13. The position of the posterior communicating artery, as frequently sphere that communicates directly with the veins of Trolard (to seen in MRA, is an important landmark that speciﬁes the intersec- the superior sagittal sinus) and Labbé (to the transverse sinus). The other choices do not re- (C) M2 and M3 segments ceive venous blood directly from the superﬁcial middle cerebral (D) P1 and P2 segments vein. Answer C: The position of this lesion is in that portion of the hemisphere occupied by the lenticular nucleus; the lenticulostri- 296 Q & A’s: A Sampling of Study and Review Questions with Explained Answers ate branches of the M1 segment of the middle cerebral artery serve may cause certain deﬁcits, but not those experienced by this man. Answer B: The posterior inferior cerebellar artery (commonly ercular branches (M3) serve cortical structures. Answer C: As the internal carotid artery exits the cavernous si- the cisterna magna (giving off small branches to the choroid plexus nus, it becomes the cerebral part of the internal carotid and, after in the fourth ventricle), then joins the inferior and medial surface giving rise to three important small branches (ophthalmic, ante- of the cerebellum. None of the other choices forms prominent rior choroidal, posterior communicating), bifurcates into the an- vascular structures in the cisterna magna or serves the choroid terior and middle cerebral arteries. Answer E: The medial posterior choroidal artery originates from bral artery is the smaller of these two terminal branches. None of the P2 segment of the posterior cerebral artery, arches around the the other choices gives rise to the anterior and middle cerebral ar- midbrain, and enters the caudal end of the third ventricle. Answer B: The superior sagittal sinus, straight sinus, the two choroideum and extends into the plexi of the temporal horn and transverse, and the occipital sinus (when present) converge at the the body of the ventricle. These patterns may be somewhat vari- conﬂuence of sinuses (conﬂuens sinuum), which is located inter- able. Choroidal branches of anterior inferior cerebellar artery nal to the external occipital protuberance. The venous angle is the (AICA) serve the choroid plexus extending through the foramen of junction of the thalamostriate and the internal cerebral veins, and Luschka, and these branches from the posterior inferior cerebellar the great cerebral vein (of Galen) receives the internal cerebral artery (PICA) serve the plexus within the fourth ventricle. Answer D: The oculomotor nerve (III) is located between the tains the transition from the sigmoid sinus to the internal jugular posterior cerebral and superior cerebellar arteries and may be vein and the terminus of the inferior petrosal sinus. Most eye movement composed mainly of the basal part of the occipital bone; this is the would be lost (the trochlear (IV) and abducens (VI) nerves are in- location of the basilar plexus.
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