Anatomy & Physiology (Chapter 18_ Urinary System) PDF

hapter 18 C URINARY SYTEM SEELEY'S ESSENTIALS OF ANATOMY AND PHYSIOLOGY, 9TH EDITION. Created by: Johmel De Ocampo  Created by: Johmel De Ocampo URINARY SYSTEM FUNCTIONS OF URINARY SYSTEM 1...

hapter 18 C URINARY SYTEM SEELEY'S ESSENTIALS OF ANATOMY AND PHYSIOLOGY, 9TH EDITION. Created by: Johmel De Ocampo  Created by: Johmel De Ocampo URINARY SYSTEM FUNCTIONS OF URINARY SYSTEM 1. Excretion 2. Regulation of blood volume + pressure. 3. Regulation of the concentration of solutes in the blood. 4. Regulation of RBC synthesis. 5. Regulation of vit. D synthesis. ANATOMY OF THE KIDNEY Kidneys – bean-shaped organs; size of a tightly clenched fist Renal capsule – CT that surround each kidney Hilum – where the renal artery and nerves enter Renal sinus – cavity that contains blood vessels Cortex (outer) Medulla (inner) – surround the renal sinus Renal pyramids – located bet. the cortex & medulla Calyx – funnel-shaped structure that surround the tip of each pyramid Renal pelvis – formed by calyces into a larger funnel Ureter – exits the kidney and connects to the urinary bladder Nephron – functional unit of the kidney Renal corpuscle Proximal convoluted tubule Loop of Henle Distal convoluted tubule Collecting duct – carries the fluid from the cortex through the medulla Papillary duct – empty their contents into a calyx Juxtamedullary nephrons (15%) – have loops of Henle that extend deep into the medulla Cortical nephrons (85%) – have loops of Henle that do not extend deep into the medulla Bowman’s capsule – consists of the enlarged end of the nephron  Created by: Johmel De Ocampo URINARY SYSTEM Glomerulus – tuft of capillaries that resembles a ball of arn; lies within the indentation of Bowman’s capsule Podocytes – inner layer of Bowman’s capsule that consists of specialized cells Filtration membrane – formed by glomerular capillaries, basement membrane, and podocytes of BC Filtrate – the fluid that passes across the filtration membrane  Created by: Johmel De Ocampo URINARY SYSTEM ARTERIES AND VEINS Renal arteries – branch off the abdominal aorta and enter the kidneys Interlobar arteries – pass bet. the renal pyramids Arcuate arteries – arch bet. the cortex and the medulla Interlobular arteries – branch off the arcuate arteries and project into the cortex Afferent arterioles – arise form branches of the interlobular arteries and extend to the glomerular capillaries Efferent arterioles – extend from the glomerular capillaries Peritubular capillaries – surround the proximal convoluted and distal convoluted tubules and the loops of Henle Vasa recta – specialized portions of the peritubular capillaries that extend deep into the medulla Juxtaglomerular apparatus – formed where the distal convoluted tubule comes in contact with the afferent arteriole next to BC URINE FORMATION 1. FILTRATION Movement of water, ions, and small molecules through the FM into the BC Filtration pressure – forces fluid from the glomerular capillary across the FM into the BC Glomerular capillary pressure – BP in the glomerular capillary Capsular pressure – pressure of filtrate already inside the BC Colloid osmotic pressure – pressure of filtrate within the glomerular capillary Regulation of Filtration Cardiovascular shock – the filtration pressure and filtrate formation fall dramatically 2. TUBULAR REABSORPTION Movement of substances from the filtrate across the wall of the nephrons back into the blood of the peritubular capillaries 3. TUBULAR SECRETION Active transport of solutes across the nephron walls into the filtrate  Created by: Johmel De Ocampo URINARY SYSTEM  Created by: Johmel De Ocampo URINARY SYSTEM  Created by: Johmel De Ocampo URINARY SYSTEM REGULATION OF URINE CONCENTRATION AND VOLUME HORMONAL MECHANISM 1. Renin-Angiotensin-Aldosterone-Mechanism Renin is secreted from the kidney when blood pressure decreases Renin converts angiotensinogen to angiotensin I; then converted to angiotensinogen II; which stimulates aldosterone Aldosterone increases Na+ and Cl+ reabsorption from the nephron 2. Antidiuretic Hormone Mechanism Secreted from the posterior pituitary when blood concentration increases / blood pressure decreases Increases the permeability to water of the distal convoluted tubules and collecting ducts Increases water reabsorption by the kidney 3. Atrial Natriuretic Hormone Secreted from the RA in response to increased blood pressure Acts on the kidney to increase Na+ & water loss in the urine URINE MOVEMENT Anatomy and Histology of the Ureters, Urinary Bladder, and Urethra Ureters – small tubes that carry urine Urinary bladder – hollow muscular container that stores urine Urethra – tube that carries urine form the urinary bladder to the outside of the body Internal urinary sphincter (males) – smooth muscle at the junction of the urinary bladder and urethra External urinary sphincter (males + females) – skeletal muscle that surrounds the urethra Micturition Reflex Activated by stretch of the urinary bladder wall  Created by: Johmel De Ocampo URINARY SYSTEM  Created by: Johmel De Ocampo URINARY SYSTEM BODY FLUID COMPARTMENTS Intracellular fluid compartment – fluid inside all the cells in the body Extracellular fluid compartment – fluid outside all the cells in the body Composition of the Fluid in the BFC Intracellular fluid – contains more K, Mg, PO4, SO4, protein, Extracellular fluid – contains more Na, Ca, Cl, HCO3 Exchange bet. BFC Water moves continually bet. compartments I response to hydrostatic pressure differences and osmotic differences bet. the compartments REGULATION OF EXTRACELLULAR FLUID COMPOSITION Thirst Regulation Blood concentration increases = thirst center initiates sensation of thirst When water is consumed, blood concentration increases = thirst sensation decreases Blood pressure decreases = thirst sensation is triggered Consumption of water = increases blood volume + allows blood pressure to increase Thirst center – neurons in the hypothalamus that control water intake Thirst – one of the important means of regulating ECF volume and concentration  Created by: Johmel De Ocampo URINARY SYSTEM Ion Concentration Regulation Sodium ions are dominant extracellular ions Aldosterone increases Na+ reabsorption from filtrate ADH increases water reabsorption from the nephron ANH increases Na+ loss in urine Aldosterone increases K+ secretion in urine Increased blood levels of K+ stimulate Decreased blood levels of K+ inhibit PTH increases extracellular Ca2 + levels Causes bone resorption Increases Ca2 + uptake in the kidney PTH increases vit. D synthesis Calcitonin (thyroid gland) Inhibits bone resorption Lowers blood Ca2 + levels Phosphate + Sulfate Ions When levels are low in the filtrate = ions are reabsorbed When levels are high = excess is lost in the urine REGULATION OF ACID-BASE BALANCE Buffers Resist changes in the pH; Proteins, phosphate buffer system, bicarbonate buffer system Respiratory System Increase respiratory rate raises pH = rate of CO2 elimination is increased Reduced respiratory rate = reduces pH (CO2 elimination is reduced) Kidneys Excrete H+ in response to decreasing blood pH Reabsorb H+ in response to an increasing blood pH  Created by: Johmel De Ocampo URINARY SYSTEM Acidosis and Alkalosis Acidosis – occurs when blood pH falls below 7.35 Respiratory acidosis – respiratory is unable to eliminate adequate amounts of CO2 Metabolic acidosis – excess production of acidic substances (lactic acid + ketone bodies) Alkalosis – occurs when blood pH increases above 7.45 Respiratory alkalosis – results from hyperventilation in response to stress Metabolic alkalosis – results from rapid elimination of H+ from body  Created by: Johmel De Ocampo URINARY SYSTEM