Anatomy exam 4 - urinary and fluid/electrolyte balance

•Components of the urinary system

kidneys, ureters, bladder, urethra

functions of the kidney

regulate ion levels and acid-base balance, produce and release erythropoietin, regulate bp (renin release)

hilum of kidney

concave medial border of the kidney where vessels, nerves, and ureters connect

adrenal glands location

on top of each kidney (superior aspect of kidneys)

nephron

functional unit of the kidney

nephron components

renal corpuscle and renal tubule; all of corpuscle and most tubules reside in kidney cortex

parts of the nephron (specific)

renal corpuscle (glomerulus, glomerular capsule, capsular space), proximal convoluted tubule, nephron loop, distal convoluted tubule

nephrons drain into ______ which empty into _______

collecting tubule ; collecting ducts

collecting tubules and collecting ducts project toward

renal papilla where fluid empties into papillary duct

juxtaglomerular apparatus (JG)

helps regulate blood filtrate formation, systemic blood pressure

juxtaglomerular apparatus components

granular cells, macula densa cells

granular cells

smooth muscle cells of the afferent arteriole that are near renal corpuscle; they contract by stretch or sympathetic stimulation and synthesize, store, and release RENIN*

macula densa

modified epithelial cells of DCT* on tubule side next to afferent arteriole; signal granular cells to release renin through paracrine stimulation; they respond to decreases in NaCl concentration of fluid in DCT

blood flow through kidneys

20-25% of resting cardiac output goes to kidneys; filtrate is formed when blood flows through glomerulus and plasma components enter capsular space

t/f the kidneys are very vascular

true - lots of blood flows through them for filtration

blood supply to kidneys

renal artery --> smaller arteries as it branches out toward the cortex --> afferent arteriole that carries blood to glomerular capsule --> peritubular capillaries and vasa recta

filtrate

formed by water and solutes that are filtered from blood plasma in the glomerulus

3 steps in urine formation

glomerular filtration, tubular reabsorption, tubular secretion

glomerular filtration

movement of substances from blood w/in glomerulus into the capsular space

tubular reabsorption

movement of substances from tubular fluid back into blood

tubular secretion

movement of substances from blood into tubular fluid

filtration membrane

made up of endothelium of fenestrated capillary, basement membrane of capillary, and filtration slits of visceral layer

visceral layer of glomerular capsule

pedicels, filtration slits, and podocytes

fenestrated capillary in filtration membrane

has slits/gaps for materials to pass through

net filtration pressure

net difference bettween blood osmotic pressure (oncotic pressure) and fluid pressure in capsular space of renal corpuscle

glomerular filtration rate

ovolume of fluid filtered from the glomerular capillaries into the capsular space per unit time (typically one minute); how many ml/min the kidneys filter

GFR controls:

urine production

what influences GFR

luminal diameter of afferent arteriole, surface area of filtration membrane, intrinsic kidney controls, and extrinsic controls

renal autoregulation

intrinsic ability of the kidney to maintain glomerular bp and GFR despite changes in systemic arterial pressure

myogenic response

muscle contraction or relaxation of smooth muscle or afferent arteriole wall

myogenic response causes:

decreased bp, less smooth muscle stretch in arteriole, smooth muscle relaxation, more glomerular blood flow, **GFR remains normal**

decreasing GFR

through sympathetic stimulation; less blood flow, less filtration, less urine production, more fluid retention, increased blood flow `

contraction of ______ cells decreases surface area

mesangial cells