FSU BSC 2086 - Lesson 19: The Urinary System Part I

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Describe the structures of the urinary system and explain their functionThe structures of the urinary system are: Kidneys, Urinary tract (Ureters, Urinary bladder, and Urethra)The function of the kidneys (2) is to produce urine, which contains water, ions, and small soluble compoundsThe urinary tract is an organ that’s function is to eliminate urineUrine flows out of the kidneys to  urinary tract (consists of ureters) urinary bladder, a muscular sac for temporary storage of urine  urethra, conducts urine to the exteriorThe urinary bladder and urethra eliminate urine by urination/micturitionThe muscular urinary bladder contracts and forces urine through the urethra and out of the bodyExplain the function of the urinary systemThe three major functions are:i. Excretion- the removal of organic waste products from body fluidsii. Elimination- the discharge of these waste products into the environmentiii. Homeostatic regulation of the volume and solute concentration of blood plasmaExplain how the urinary system maintains homeostasis within the bodyThe urinary system preforms carefully regulated activities to keep the composition of blood within acceptable limits by:i. Regulating blood volume and blood pressure, by adjusting the volume of water lost in urine, releasing erythropoietin, and releasing renin.ii. Regulating plasma concentrations of sodium, potassium, chloride, and other ions, by influencing the quantities lost in urine. The kidneys also control calcium ion levels through the synthesis of calcitriol.iii. Helping to stabilize blood pH, by controlling the loss of hydrogen ions and bicarbonate ions in urine.iv. Conserving valuable nutrients, by preventing their loss in urine while removing organic wastes—especially nitrogenous wastes such as urea and uric acid.v. Assisting the liver in detoxifying poisons and, during starvation, deaminating amino acids so that other tissues can metabolize them.Describe the anatomy of the kidneyThe kidneys are located on either side of vertebral column. The left kidney is superior to the right kidney and the superior surface capped by adrenal gland. The position of the kidneys are maintained by: overlying peritoneum, contact with adjacent visceral organs, and supporting connective tissues.Each kidney is protected and stabilized by three concentric layers of connective tissueFibrous capsule (innermost layer)A layer of collagen fibersCovers outer surface of entire organPerinephric (around perimeter) fat capsuleA thick layer of adipose tissueSurrounds renal capsuleThe protective portionRenal fascia (outermost layer)A dense, fibrous outer layer that hold everything in positionAnchors kidney to surrounding structuresTypical Adult Kidney is about 10 cm long, 50.5 cm wide, and 3 cm thick (4 in. ´ 2.2 in. ´ 1.2 in.) and weighs ~ 150 g (5.25 oz)The fibrous capsule lines the renal sinus, an internal cavity within the kidney. It stabilizes the position of the ureter and of the renal blood vessels and nervesThe renal cortex is the outer portion of the kidneyThe inner portion is the renal medulla that consists of 6-18 distinct triangular structures, renal pyramids.The tip of the pyramids projects into the renal sinusAdjacent renal pyramids are separated by bands of cortical tissue, renal columns (extend into medulla)A renal lobe consists of a renal pyramid, the overlying area of re- nal cortex, and adjacent tissues of the renal columns.Urine is produced in the renal lobes in nephronsDucts within renal papilla discharge urine into the minor calyx (4/5 minor calyces= major calyx, 2/3 major calyces form renal pelvis)Renal pelvis fills most of the renal sinus and is connected to the ureter, which drains he kidneyDescribe the blood supply to the kidneysThe kidneys receive some blood from the Cardiovascular system but only a small amount gets filted (16-20%), a lot of the fluid plasma remains in blood. Kidneys receive 20-25% of total cardiac outputKidney receives blood through renal arteryBlood flow: from renal artery → segmental arteries → interlobar arteries → arcuate arteries → cortical radiate (interlobular) arteries → afferent arterioles (form part of nephron) → glomerulus efferent arteriole → peritubular capillaries (located around the renal tubules) → venules → cortical radiate (interlobular) veins → arcuate veins → interlobar veins → renal vein (which leaves the kidney)There are NO segmental veins!Explain the function of the renal nervesThe renal nerves innervate kidneys and ureters through sympathetic innervation by adjusting the rate of urine formation by changing blood flow and blood pressure at nephron and stimulating the release of renin (Restricts losses of water and salt in urine by stimulating reabsorption at nephron. Renin-angiotensin system stimulates aldosterone release from adrenal cortex)Describe the structure of the nephron and explain its function. What is found in the renal corpuscle?Parts of the nephron and processes that occur:Glomerulus - tuft of capillaries; filtrationBowman's capsule - enlarged, cup-shaped capsule which surrounds the glomerulus; collects filtrateProximal convoluted tubule - tubular reabsorptionLoop of Henle - sodium and water balanceDistal convoluted tubule - tubular secretionEach nephron consists of a renal corpuscle and renal rubeA capillary network know as the glomerulus is found in the renal corpuscleExplain the difference between the renal tubule and the glomerulusThe glomerulus is a part of the renal corpuscle, where blood is filtered, and the renal tubule is composed of the proximal convoluted tubule (PCT) where reabsorption and secretion takes placeExplain where filtration, reabsorption, and secretion takes place on the nephron. What is filtered, reabsorbed, and/or secreted?Filtration occurs in renal corpuscle. Blood pressure forces water and dissolved solutes of glomerular capillaries into capsular space and produces a filtrate (a protein-free solution, similar to blood plasma expect is lacks proteins)Reabsorption in the renal tubule (has two segments: PCT & DCT) occurs in proximal convoluted tubule, and distal convoluted tubule. In reabsorption useful materials are recaptured before filtrate leaves kidneys, reabsorbs more than 90% of water in filtrate and secretes into the tubule lumen any waste products that did not pass into the filtrate at the glomerulusSecretion occurs in the proximal convoluted tubule, distal convoluted tubule, and collecting ductExplain the


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FSU BSC 2086 - Lesson 19: The Urinary System Part I

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