Unit 5 urinary system Flashcards
functions of the urinary system
filter and cleanse blood!
-regulation of blood composition, volume, and pH
-excretion of metabolic wastes (urea, uric acid, creatinine)
-secretion of hormones
structure of kidneys
right and left, anterior is covered by peritoneum, some protection from rib cage
function of ureters
walls contract to conduct urine from kidney to urinary bladder by peristalsis
function of urinary bladder
expandable, stores urine, three openings. detrusor (smooth) muscle contracts to release urine
function of urethra
tube from bladder to external orifice. Males is longer, carries urine and semen.
Structures of the kidneys
-hilum
-adrenal gland
-fibrous capsule
hilum function
entry/exit for ureter and renal A&V
adrenal gland function
cortex produces steroid hormones, medulla produces epinephrine and norepinephrine
fibrous capsule function
covers each kidney
internal features of the kidney
-renal cortex: outermost region
-medulla: middle region, contains pyramids and coulmns
-pelvis: innermost region, collection of urine from all major calyces
urine flow
- wastes collected in collecting duct (located inside renal pyramid of renal medulla)
- empties into minor calyx then major calyx
- drains into renal pelvis-> ureter-> bladder->urethra-> external orifice
blood flow
aorta-> renal artery-> segmental artery-> interlobar artery-> arculate artery-> cortical radiate artery-> afferent arterioles-> glomerulus (capillary)-> efferent arteriole-> peritubular capillary-> renal vein-> IVC
nephron structure
microscopic system of tubules intertwined with capillaries
nephron function
urine producing units. occurs through filtration, reabsorption, secretion
cortical nephrons
located mostly in cortex. associated with peritubular capillaries.
juxtamedullary nephrons
located in both cortex and medulla. associated with vasa recta
regions of a nephron
renal corpuscle (glomerulus and glomerular capsule), renal tubules, proximal convuluted tubule (PCT), loop of the nephron. distal convuluted tubule (DCT), multiple nephrons drain into a collecting duct
glomerular capsule structure
hollow cup like structure. parietal layer: simple squamous epithelium. visceral layer: podocytes surrounding glomerulus (part of filtration membrane)
glomerulus structue
fenestrated capillaries (moderately permeable). filtrate=solute-rich lfuid from blood that enters the capsular space.
PCT structure
cuboidal epithelium with dense microvilli, proximal to corpuscle. microvilli= brush border increases SA for reabsorption
DCT structure
cuboidal epithelium with few microvilli, distal to corpuscle
which structure has more absorption: PCT or DCT and why?
PCT has more absorption because of the increased Surface Area due to more microvilli.
loop of nephron structure
u-shaped loop, with descending then ascending limbs, portions may be thick or thin
collecting duct structure
not part of nephron! located within renal pyramids, collects filtrate from many nephrons. ducts fuse, then dump filtrate into minor calyces. cells regulate water balance
urine formation steps
- glomelular filtration
- tubular reabsorption
- tubular secretion
filtration membrane structure
separating blood and inside of capsule
fenestrated endothelium of capillary
pores allow everything but blood cells to pass through
basement membrane (basal lamina)
glycoproteins that block large proteins (also repels proteins due to negative charge)
foor processes of podocytes
membranes between processes trap any macromolecules
what enters the tubules of the nephron?
enters capsular space, becomes filtrate: water, solutes, nutrients, nitrogenous wastes
REMAINS IN CAPILLARY: blood cells, plasma proteins
Glomerular filtration is like what?
washing grapes in a strainer grapes represent blood cells
renal artery branches into many smaller arterioles,
arteriole brings blood to glomerulus
filtration
passive process where blood is filtered
filtrate enters capsular space due to…
hydrostatic forces
what remains in capillary after glomerular filtration?
blood cells and plasma proteins!
increase in glomerular filtration rate (GFR) is caused by…
increase in urine output, decrease in blood volume and pressure
glomerular filtration rate (GFR) is affected by
-filtration pressures (main factor)
-surface area available
-permeability
glomerular filtration rate (GFR) is highly regulated by
-autoregulation (intrinsic control)
-nervous and endocrine systems (extrinsic controls)
pressures in the glomerulus:
include hydrostatic and osmotic pressures of glomerular capillary vs. capsular space
positive NFP means..
outward pressures greater than inward pressures, fluid moves out of capillary into capsular space
Tubular reabsorption key idea
water and solutes return to capillary (from nephron tubules-> to peritubular capillaries)
at the PCT what are reabsorbed and where?
water, nutrients, and ions are reabsorbed. they are reabsorbed into peritubular capillaries.
transport occurs through which routes?
trans or paracellular routes
how does sodium cross the apical membrane?
secondary active transport
how does sodium pass the basolateral membrane?
primary active transport
how do glucose and amino acids pass the apical membrane?
secondary active transport
how do glucose and amino acids pass the basolateral membrane?
facilitated diffusion
what is passively absorbed?
-lipid-soluble substances by simple diffusion
-Ions and urea through paracellular diffusion
-water by osmosis through aquaporins
which tubule absorbs the majority of the filtrate?
PCT
transport proteins are _ to substance and _.
specific, limited
when transporters are saturated…
maximum transport is met, so excess excreted in urine. Occurs with diabetes-> glucose in urine
what is reabsorbed by osmosis?
water
the ascending limb is impermeable to what? so it reabsorbs what?
water, solutes reabsorbed by secondary active transport
the descending limb is impermeable to what? so it reabsorbs what?
solutes, water reabsorbed by osmosis
