Anatomy and Physiology II Exam III Urinary System Functions of the Urinary System Regulate aspects of homeostasis o Water balance with Antidiuretic Hormone ADH o Acid base balance in the blood by regulating plasma pH o Regulate plasma ionic composition electrolytes with aldosterone o Regulate blood pressure and blood volume by regulating plasma volume and plasma osmolality o Red blood cell production secrete erythropoietins stimulates RBC production when low oxygen levels are detected and renin aka angiotensinogenase released in low blood pressure o Activates vitamin D3 calcitriol Elimination of waste products o Nitrogenous wastes o Toxins o Drugs Developmental Aspects of the Urinary System Functional kidneys are developed by the third month Urinary system of a newborn o Bladder is small o Urine cannot be concentrated for first 2 months o Void 5 to 40 times per day Structures of the Urinary System Kidneys form urine Ureters transport urine from kidneys to bladder Urethra excretes urine from bladder to outside of body Bladder stores urine Urinary Bladder Smooth collapsible muscular sac Control of the voluntary urethral sphincter does not start until age 18 months Complete nighttime control may not occur until the child is 4 years old Urinary infections are the most common problems before old age Esherichia coli a type of bacteria accounts for 80 of UTI urinary tract infection Alcohol inhibits ADH release Temporarily stores urine a moderately full bladder is about 5 inches long and holds about 500 mL of urine Trigone is a triangular region of the bladder base o Three openings One to the urethra Two form the ureters o In males the prostate gland surrounds the neck of the bladder Urinary Bladder Wall Three layers of smooth muscle collectively called the detrusor muscle Mucosa made of transitional epithelium Walls are thick and folded in an empty bladder Bladder can expand significantly without increasing internal pressure The right kidney is slightly lower than the left due to position of the liver Renal hilum is a medial indentation where several structures enter or exit the kidney ureters renal blood vessels and nerves An adrenal gland sits atop each kidney One quarter of the total blood supply of the body passes through the kidneys each minute Renal artery provides each kidney with arterial blood supply Renal artery divides into segmental arteries interlobar arteries arcuate arteries cortical radiate arteries Venous blood flow cortical radiate veins arcuate veins interlobar veins renal vein Nephron Anatomy and Physiology The structural and functional units of the kidneys are nephrons Responsible for forming urine Renal tubule extends from glomerular capsule and ends at the collecting duct Kidney Features Blood Supply o Glomerular Bowman s capsule o Proximal convoluted tubule PCT o Loop of Henle o Distal convoluted tubule DCT Types of Nephrons Cortical nephrons o Located in the cortex o Includes most Juxtamedullary nephrons found at the boundary of the cortex and dips into the medulla Nephron Anatomy Nephrons are associated with various capillary beds o o Peritubular capillary bed o Vasa recta only Juxtamedullary nephrons Glomerulus o Knot of o Capillaries are covered with podocytes from the renal tubule o Glomerulus sits within a glomerular capsule the first part of the renal tubule Glomerulus Fed and drained by arterioles o Afferent arteriole arises from a cortical radiate artery and feeds the glomerulus o Efferent arteriole receives blood that has passed through the glomerulus Specialized for filtration High pressure forces fluid and small solutes out of blood and into the capsule Peritubular Capillary Beds Arise from efferent arteriole of the glomerulus Normal low pressure capillaries Adapted for absorption instead of filtration Cling close to the renal tubule to reabsorb reclaim some substances from tubes Renal Corpuscle Renal corpuscle o Bowman s capsule inflow end of renal tubules o Glomerulus tuft of capillaries Site of filtration movement from to tubules Collecting Duct Receives urine from many Run through the medullary pyramids Delivers urine into the calyces and renal pelvis Basic Renal Processes Glomerular filtration is from glomerulus to Bowman s capsule Reabsorption is from tubules to Peritubular capillaries is from Peritubular capillaries to tubules Excretion is from tubules out of body Glomerular Filtration Mostly nonselective passive process size of solute Water and solutes smaller than proteins are forced through capillary walls and blood cells are normally too large to pass through the filtration membrane Filtrate is collected in the glomerular capsule and leaves via the renal tubule o GFR 125 mL min or 180 liters day Reabsorption Movement from tubules into capillaries returned to blood o Most occurs in proximal tubule o Most is not regulated o Barrier for reabsorption Epithelial cells of renal tubules Endothelial cells of capillary minimal Tubular Reabsorption The Peritubular capillaries reabsorb useful substances o Water o Glucose o o ions Some reabsorption is passive most is active Most reabsorption occurs in the proximal convoluted tubule Materials not reabsorbed o Nitrogenous waste products o Uric acid from nucleic acid breakdown o Creatinine is associated with creatine metabolism in muscles Reabsorption in Proximal Tubule Proximal tubule is a mass absorber Non regulated reabsorption has a large surface area Approximately 70 water and sodium reabsorbed 100 glucose reabsorbed Tubular Secretion Can Be Described as Reabsorption in Reverse Secretion is the movement of materials from the Peritubular capillaries into the renal tubules Process is important for getting rid of substances not already in the filtrate Materials left in the renal tubule move toward the Some secreted substances Amount of substance excreted amount filtered amount secreted amount reabsorbed Amount excreted depends on 3 factors o Potassium o Hydrogen ions o Choline o Creatinine o Penicillin Excretion Rate o o Secretion rate Reabsorption rate Renal Handling of Solute Clearance If amount of solute excreted per minute is less than filtered load solute was reabsorbed If amount of solute excreted per minute is greater than filtered load solute was Volume of plasma from which a substance has been removed by kidneys per unit time The clearance of can be used to measured glomerular filtration rate Clearance excretion rate concentration in urine UxXV Px Clearance of substance freely filtered fully
View Full Document
Unlocking...