By K. Arakos. Shorter College. 2017.

The blood coming from the ate trapped in the mucus gel layer neutralizes acid best 10mg maxalt, pre- stomach during active acid secretion contains much venting damage to the mucosal cell surface. The os- motic gradient created by the HCl concentration in the gland lumen drives water passively into the lumen, thereby, Hydrochloric Acid Is Secreted by the Parietal Cells maintaining the iso-osmolality of the gastric secretion. The HCl present in the gastric lumen is secreted by the parietal cells of the corpus and fundus. The mechanism of Gastric Juice Contains Various Electrolytes HCl production is depicted in Figure 27. At a low se- etal cell actively pumps H out of the cell in exchange for cretion rate, gastric juice contains high concentrations of Na and Cl and low concentrations of K and H. When the rate of secretion increases, the concentration of Na Plasma Parietal cell Lumen decreases while that of H increases significantly. Also coupled with this increase in gastric secretion is an increase in Cl concentration. To understand the changes in elec- CO2 CO2 + H2O trolyte composition of gastric juice at different secretion Carbonic anhydrase + rates, it is important to remember that gastric juice is de- H H+ rived from the secretions of two major sources: parietal H2CO3 - ATP cells and nonparietal cells. Secretion from nonparietal cells HCO3 HCO - is probably constant; therefore, it is parietal secretion (HCl 3 ADP+Pi K+ secretion) that contributes mainly to the changes in elec- + + trolyte composition with higher secretion rates. Cl- - K K Cl - Cl- Cl Na+ Gastric Secretion Performs Digestive, Na+ ATP Protective, and Other Functions ADP+Pi + + Gastric juice contains several proteins: pepsinogens, K K pepsins, salivary amylase, gastric lipase, and intrinsic factor. The chief cells of the oxyntic glands release inactive The mechanism of HCl secretion by the pepsinogen. Pepsin also cat- CHAPTER 27 Gastrointestinal Secretion, Digestion, and Absorption 487 160 Cl- Vagal Gastric juice stimulation 140 H+ 120 ACh 2+ K+ 100 Ca Gastric hydrogen ion pump H+ 80 Gastrin cAMP Adenylyl 60 cyclase ATP 40 Histamine FIGURE 27. Chicago: Year 2 ceptors results in an increase in intracellular Ca concen- Book, 1977.

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Such drugs have not been risked in patients but phencyclidine cheap 10mg maxalt, which has been used as an anaesthetic (and drug of abuse), is known to cause amnesia and has been found to directly block NMDA receptor channels. Generally in both animals and humans, increases in NA activity (a1 agonists, a2 antagonists) improve cognition although both positive and negative effects have been reported with a2 agonists and cardiovascular effects cannot be ruled out in all these studies. Removal of the posterior pituitary in rats shortens retention of a conditioned avoidance response, an effect which can be overcome by the administration of vasopressin. Variable but generally weak positive effects on cognition have been seen with this peptide in humans. Opioids tend to impair and their antagonists improve memory in animals (see McGough, Introlni-Collison and Castellano 1993). THERAPY Therapy should be aimed at either (a) The manipulation of NTs known to be affected by the neurodegeneration or (b) The attenuation and possible reversal of any cause of AzD such as amyloid production and deposition It must be made clear from the outset, however, that there is currently no way of stopping the progression of (i. MANIPULATION OF NEUROTRANSMITTERS AUGMENTING CHOLINERGIC FUNCTION Since ACh appears to be important in memory processing and as its concentration is significantly reduced in appropriate brain areas in AzD then augmenting its action should at least improve memory function. ACh activity may be increased by (1) Enhancing its synthesis (and presumed release) through giving the precursor choline (2) Stopping its degradation by cholinesterase with anticholinesterase drugs (3) Reproducing its action with appropriate agonists Ð (a) muscarinic, (b) nicotinic Approaches (1) and (2) depend on sufficient cholinergic function remaining to make its supplementation feasible, while all three methods suffer from the fact that not only does ACh have other central effects (e. Increased synthesis This requires the provision of the precursor choline which is often given as lecithin (phosphatidyl choline), a natural source of choline found in many foods such as eggs and fish. Brain penetration is modest but uptake into cholinergic nerve terminals is through a sodium-dependent high-affinity system that is normally adequately supplied and possibly saturated with choline. In any case, ACh can only be synthesised from choline in cholinergic nerve terminals, many of which will have degenerated, and just increasing the activity of those remaining may not be ade- quate. Whether choline could reverse the choline leakage and resulting autocannibalism (see above) of cholinergic neurons is not known.

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Describe the structure and position of the uterine tubes During pregnancy discount maxalt 10mg overnight delivery, the vulva becomes swollen and bluish— and explain how an ovum is transported through a uterine especially the labia minora—because of increased vascularity tube to the uterus. Describe the histological structure of the uterine wall and comes more apparent as pregnancy progresses. The vulva has both sympathetic and parasympathetic in- nervation, as well as extensive somatic neurons that respond to 11. Parasympathetic stimulation causes a re- changes do these structures undergo during sexual excite- sponse similar to that of the male: dilation of the arterioles of the ment and coitus? Mechanism of Erection and Orgasm MAMMARY GLANDS The homologous structures of the male and female reproductive Mammary glands are modified sweat glands composed of secre- systems (see table 21. The erectile tissues of a female, like those of a male, be- male breasts at puberty and function in lactation. Objective 12 Distinguish between the mammary glands and During sexual excitement, the hypothalamus of the brain sends the breast and describe the structure of the mammary glands. Female Reproductive © The McGraw−Hill Anatomy, Sixth Edition Development System Companies, 2001 Chapter 21 Female Reproductive System 739 Clavicle Suspensory ligaments 1st rib Lactiferous sinus Nipple Pectoralis major muscle Lobule (cut) Areola Adipose tissue Mammary ducts Intercostal muscles Pectoralis minor muscle (b) Pectoral fascia Lactiferous duct Lobe Lactiferous sinus Lung Mammary duct (a) Suspensory ligaments FIGURE 21. In structure, the mammary glands, located in the breasts, are Each mammary gland is composed of 15 to 20 lobes, each modified sweat glands and are a part of the integumentary sys- with its own drainage pathway to the outside. In function, however, these glands are associated with the rated by varying amounts of adipose tissue. The amount of adi- reproductive system because they secrete milk for the nourish- pose tissue determines the size and shape of the breast but has ment of the young. The size and shape of the breasts vary consid- nothing to do with the ability of a woman to nurse. Each lobe is erably from person to person in accordance with genetic subdivided into lobules that contain the glandular mammary differences, age, percentage of body fat, or pregnancy. The mammary alveoli are the structures that berty, estrogen from the ovaries stimulates growth of the mam- produce the milk of a lactating female.

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Other functions of inferior vena cava for the right adrenal gland and through the insulin include stimulating muscle and liver cells to convert suprarenal vein into the left renal vein for the left adrenal gland cheap maxalt 10 mg with amex. Failure of beta cells to rons of the splanchnic nerves and by fibers of the celiac and asso- produce insulin causes the common hereditary disease diabetes ciated sympathetic plexuses. The action of the hormones from the pancreatic islets is summarized in table 14. Functions of the Adrenal Glands Knowledge Check Over 30 hormones have been identified as being produced by the adrenal cortex. What disease is caused by the insufficient production coids, glucocorticoids, and gonadocorticoids. The mineralocorticoids are produced by the zona glomeru- losa of the adrenal cortex and regulate the concentrations of ex- tracellular electrolytes. Aldos- ADRENAL GLANDS terone affects the kidneys, causing them to reabsorb sodium and increase potassium excretion. At the same time, it promotes The adrenal cortex and adrenal medulla are structurally and func- water reabsorption and reduces urine output. The adrenal medulla secretes catecholamine The glucocorticoids are produced primarily by the zona fasci- hormones that complement the action of the sympathetic division culata of the adrenal gland and influence the metabolism of car- of the ANS. The adrenal cortex secretes corticosteroids that func- bohydrates, proteins, and fats. The glucocorticoids also promote tion in the regulation of mineral balance, energy balance, and re- vasoconstriction, act as antiinflammatory compounds, and help productive activity. Objective 15 List the hormones secreted by the adrenal glands and discuss their effects. Endocrine System © The McGraw−Hill Anatomy, Sixth Edition Coordination Companies, 2001 472 Unit 5 Integration and Coordination (a) (b) FIGURE 14. Cortisol and related anti-inflammatory compounds are com- thought that these hormones supplement the sex hormones monly used to treat patients suffering from arthritis and vari- produced in the gonads.

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