Chapter 26 - Introduction to the Urinary System (Also Table 27.4) Three Functions of the Urinary System 0. Excretion: removal of organic wastes from body fluids 0. Elimination: discharge of waste products 0. Homeostatic regulation: of blood plasma volume and solute concentration Kidneys : produce urine Urinary tract : eliminate urine: Ureters (two tubes); Bladder (muscular sac) & Urethra (exit tube) Urination ( micturition ) : process of eliminating urine; contraction of muscular urinary bladder forces urine through urethra & out of body Five Homeostatic Functions of Urinary System 0. Regulates blood volume & pressure by adjusting water lost in urine (erythropoietin & renin) 0. Regulates plasma Na + , K + & Cl - ions (control urine loss); Ca ++ ion levels (through calcitriol) 3. Helps stabilize blood pH by controlling loss of hydrogen ions & bicarbonate ions in urine 4. Conserves valuable nutrients by preventing excretion while excreting organic waste products 5. Assists liver in detoxifying poisons Kidneys are located on either side of vertebral column & superior surface capped by adrenal gland Position is maintained by overlying peritoneum, adjacent visceral organs & connective tissues Each kidney is protected and stabilized by 0. Fibrous capsule: a layer of collagen fibers that covers outer surface of entire organ 1. Perinephric fat capsule: a thick layer of adipose tissue surrounds renal capsule 2. Renal fascia: a dense, fibrous outer layer anchors kidney to surrounding structures Sectional Anatomy of the Kidneys (One Question) i. Renal sinus: i nternal cavity within kidney & lined by fibrous renal capsule b. Renal Cortex is superficial portion of kidney; reddish brown and granular c. Renal Medulla is innermost portion and contains: a. Renal Pyramids : 6-18 distinct conical structures in medulla; base abuts cortex & tip ( renal papilla ) projects into renal sinus b. Renal Columns : bands of cortical tissue separate renal pyramids & extend into medulla c. Renal Papilla : ducts discharge urine into minor calyx, a cup-shaped drain d. Major Calyx: formed by four or five minor calyces e. Renal Pelvis: funnel-shaped chamber connected to ureter, which drains kidney Nephrons - microscopic, tubular structures in cortex of renal lobe where urine production begins Blood Supply to Kidneys: kidneys receive 20–25% of total cardiac output; 1200 mL/min of blood renal vein renal artery ↑ ↓ ↑ segmental arteries ↑ ↓ interlobar veins interlobar arteries ↑ ↓ arcuate veins arcuate arteries ↑ ↓ interlobular veins interlobular arteries ↑ ↓ venules Nephrons afferent arteriole (larger diameter than efferent) ↑ ↓ peritubular capillaries glomerulus ↑ efferent arteriole ↓ Sympathetic Innervation : adjusts rate of urine formation by changing blood flow & BP at nephron; ↑ release of renin which ↓ losses of H 2 O & salt in urine by ↑ reabsorption at nephron 1
Nephron is 1.) Renal tubule : long tube begins at corpuscle & 2.) Renal corpuscle: round structure with: glomerular capsule (Bowman’s capsule) & capillary network ( glomerulus ) Glomerulus:
You've reached the end of your free preview.
Want to read all 7 pages?