BIO 241 1st Edition Lecture 25 Outline of Last Lecture I. Renal blood supply and nerve supplyII. Juxtaglomerular apparatusIII. Basic functions of the nephronIV. Three processes in urine formationV. Glomerular filtrationVI. Net filtration pressure (NFP)VII. Glomerular filtration rate (GFR)VIII.Renal autoregulationIX. Hormonal regulation – RAA systemX. Tubular reabsorption of solutesOutline of Current Lecture II. Tubular reabsorption of waterIII. Negative feedback control of ADHIV. Countercurrent multiplier and exchangerV. Tubular secretionVI. Renal clearanceVII. Summary of nephron functionsVIII. Urine drainage from the kidneysIX. Urinary bladderX. UrethraXI. Micturition reflexCurrent LectureII. The tubular reasbsorption of water occurs in two parts. The first part accounts for 90% and is called obligatory reabsorption. It is the indirect control of water and the osmosis is related to solutes. Na+ has major effects on this reabsorption (aldosterone). Facultative reabsorption (10%) is the direct control of water. It involves antidiuretic hormone (ADH) and aquaporins. These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.III.IV. The function of the loop of Henle is to concentrate urine by removing water.V. Tubule cells extract from blood and secretes into filtrate. These cells serve two purposes: waste removal – urea, uric acid, bile acids, ammonia, creatinine and acid-base balance – hydrogen ions or bicarbonate ions. If H+ secretion = HCO3- filtration, then no change in ECF pH. If H+ secretion > HCO3- filtration, then ECF pH increases (more H+ in urine). If H+ secretion < HCO3- filtration, then ECF pH decreases (less H+ in urine). The net results are that the body directly rids itself of toxic wastes and the body uses kidneys to make ECF pH changes (renal compensation). VI. Renal clearance is the volume of blood plasma from which a particular waste is completely removed (“cleared”) in one minute.VII.VIII. Urine drains from the kidneys in the following direction: papillary ducts → minor calyces → major calyces → renal sinus → ureter → urinary bladder.IX. The urinary bladder is located on the pelvic floor and its shape is known as a trigone. Its histology consists of transitional epithelium, detrusor muscles (remains relaxed to allow the bladder to store urine, and contracts during urination to release urine), and ureteral sphincters (prevent urine backflow).X. The urethra is the canal that urine exits the body through. It has an internal sphincter (involuntary) and an external sphincter (voluntary). The voluntary sphincter allows for one to hold urine. The female urethra is short and somewhat wide. The male’s is long and somewhat narrow. Males’ urethra are membranous and they also have a prostate which secretes fluid that nourishes and protects sperm.XI. The micturition reflex is the relaxation of the urethral sphincter in response to increased pressure in the bladder. The stretch of the urinary bladder (about ½ full) stimulates stretch receptors in bladder wall. This sends sensory input to the sacral parasympathetic area, causing: efferent parasympathetics cause contraction of detrusor muscle and relaxation of internal urethral sphincter + sensory input to the pons for voluntary control. If it is an inappropriate time, pons returns inhibitory signals to sacral spinal cord so that the external urethral sphincter remains contracted. If it is an appropriate time, pons returns excitatory signals to sacral spinal cord so that the external urethral sphincter relaxes, and urine is voided. In the infant, relaxation of the external sphincter is linked to relaxation of the internal
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