Chapter 25: The urinary system Flashcards
Renin
regulation of blood pressure
Erythropoietin
Regulation of RBC production
Kidneys
major excretory organs
Ureters
transport urine from kidneys to urinary bladder
Urinary bladder
temporary storage reservoir for urine
Urethra
Transports urine out of the body
Blood and Nerve Supply of kidneys
- > Kidneys cleanse blood; adjust its composition
- > renal arteries deliver ~ 1/4 (1200 ml) of cardiac output to kidneys each minute
- > arterial flow into and venous flow out of kidneys follow similar paths
- > Nerve supply via sympathetic fibers from renal plexus
Nephrons
Structural and functional units that form urine
two main parts: renal corpuscle and renal tubule
Renal Corpuscle (two parts)
Glomerulus: Tuft of capillaries; fenestrated endothelium -> highly porous -> allows filtrate formation
Glomerular capsule (Bowman’s capsule): Cup-shaped, hollow structure surrounding glomerulus
Three part of Renal Tubule
Proximal convouluted tubule: proximal-> closest to renal corpuscle
Nephron Loop
Distal convoluted tubule: Distal -> farthest from renal corpuscle
Proximal convoluted tubule (renal tubule)
- > cuboidal cells with dense microvilli (brush border -> increases surface area
- > functions in reabsorption and secretion
- > confined to cortex
Nephron loop (Renal tubule)
descending and ascending limbs
distal descending limb =descending thin limb; simple squamous epithelium
Thick ascending limb (cuboidal to columnar cells)
Distal convoluted tubule (DCT) (renal tubule)
cuboidal cells with very few microvilli
functions more in secretion than reabsorption
confined to cortex
Collecting duct
- > receive filtrate from many nephrons
- > run through medullary pyramids -> striped appearance
- > fuse together to deliver urine through papillae into minor calyces
Cortical nephrons
85% of nephrons; almost entirely in cortex
Juxtamedullary nephrons
Long nephron loops deeply invade medulla
Ascending limbs have thick and thin segments
Important in production of concentrated urine
Renal tubule associated with two capillary beds
glomerulus
peritubular capillaries
How much urine is created from the fluid we process daily?
1.5 liters. we produce 180 L daily
Glomerular Filtration
produces cell and protein free filtrate
Tubular Reabsorption
Selectively returns 99% of substances from filtrate to blood in renal tubules and collecting ducts
Tubular secretion
selectively moves substances from blood to filtrate in renal tubules and collecting ducts
Kidneys filter body’s entire plasma volume….
60 times each day; Consume 20-25% oxygen used by body at rest; produce urine from filtrate
Glomerular Filtration
- > passive process
- > hydrostatic pressure forces fluids and solutes through filtration membrane
- > Porous membrane between blood and interior of flomerular capsule
Net filtration
Outward pressure-inward pressure
55-(15+30)= 10 mmHg
