Lesson 19 The Urinary System Part I 04 07 2014 Describe the structures of the urinary system and explain their function The 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 compounds The urinary tract is an organ that s function is to eliminate urine o Urine 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 exterior o The urinary bladder and urethra eliminate urine by urination micturition The muscular urinary bladder contracts and forces urine through the urethra and out of the body Explain the function of the urinary system The three major functions are i Excretion the removal of organic waste products from body ii Elimination the discharge of these waste products into the iii Homeostatic regulation of the volume and solute concentration fluids environment of blood plasma Explain how the urinary system maintains homeostasis within the body The 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 kidney The 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 tissue o Fibrous capsule innermost layer A layer of collagen fibers Covers outer surface of entire organ o Perinephric around perimeter fat capsule A thick layer of adipose tissue Surrounds renal capsule The protective portion o Renal fascia outermost layer A dense fibrous outer layer that hold everything in position Anchors kidney to surrounding structures Typical 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 nerves The renal cortex is the outer portion of the kidney The inner portion is the renal medulla that consists of 6 18 distinct triangular structures renal pyramids o The tip of the pyramids projects into the renal sinus o Adjacent 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 o Urine is produced in the renal lobes in nephrons Ducts within renal papilla discharge urine into the minor calyx 4 5 minor calyces major calyx 2 3 major calyces form renal pelvis o Renal pelvis fills most of the renal sinus and is connected to the ureter which drains he kidney Describe the blood supply to the kidneys The 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 output Kidney receives blood through renal artery Blood 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 nerves The 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 o Glomerulus tuft of capillaries filtration o Bowman s capsule enlarged cup shaped capsule which surrounds the glomerulus collects filtrate o Proximal convoluted tubule tubular reabsorption o Loop of Henle sodium and water balance o Distal convoluted tubule tubular secretion Each nephron consists of a renal corpuscle and renal rube A capillary network know as the glomerulus is found in the renal corpuscle place Explain the difference between the renal tubule and the glomerulus The 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 Explain 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 glomerulus Secretion occurs in the proximal convoluted tubule distal convoluted tubule and collecting duct Explain the difference between cortical and juxtamedullary nephrons Cortical nephrons are
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