Excretory System Flashcards Preview

Nicole mcat > Excretory System > Flashcards

Flashcards in Excretory System Deck (30)
Loading flashcards...

Passage through excretory system

nephron , renal pelvis, ureter, bladder, urethra


Kidney structure

cortex, medulla, renal hilum (deep slit in the center of its medial surface, renal artery vein and ureter enter/ exit via the renal hilum)


Portal system

2 capillary beds in series for blood to travel through before returning to the heart


Afferent arterioles

flow from cortex to the medulla. glomeruli are highly convoluted tufts derived from afferent arterioles


efferent arterioles

lead blood away from the afferent form the vasa recta. which isth e secondary capillary bed surrounding the loop of henle


what surrounds the glomerulus

bowmans capsule


renal corpuscle

bowmans capsule and glomerulus. leads to the pct, descenidng loh, ascending loh, dct, collecting duct


micturition reflex

stretching of bladder = parasympathetic nerves fire and detrusor muscle contracts the bladder causins the interal sphinctor to relax



filtration , secretion, reabsorption



hydrostatic pressure in glomerulus is higher than in bowmans space, which causes blood to travel to the nephron. but osmolarity of blood is higher than that in bowmans space, pressure moves against blood into nephron. since hydrostatic pressure is greater than oncotic pressure the blood will move to the nephron


kidney stone

buildup of urine behind the stone increases the hydrostatic pressure of bowmans space and therefore filtration is hindered


Filtrate is

isotonic to blood



movement of solutes from blood to filtrate anywhere besides bowmans capsule. nephron secretes salts, acids, bases and urea directly into tubule by active or passive transport



componds, glucose amino acids and vitamins. movement of solutes from filtrate to blood. what we want to keep


bowmans capsule, pct and dct = primarily focused on

identity of particles in urine (keep what body needs, lose what it doesnt)


LOH and collecting duct

focused on volume and concentration of urine


PCT proximal convoluted tubule

reabsorbed= a. a , glucose water soluble vitamins and salts na cl, and water. secreted= H ions, urea , NH3 and K. Dump the "HUNK"


descending loop of henle

permeable to only water. the deeper you go into the medulla we have increased intertitial conc, so water moves out


ascending loop of henle

permeable to salts but impermeable to water. so na and cl move out of the filtrate.


Diluting segment LOH

transition between inner and outer medulla , cells lining are larger, more mitochondria and therefore more active transport. filtrate becomes hypotonic (more dilute) compared to the interstitium in the ascending lOH.


countercurrent multiplier system

flow of filtrate through LOH is opposite direction from flow of blood through the vasa recta. by making both components flow in opp directions, the filtrate is constantly being exposed to hypertonic blood, which allows for the maximum reabsorp of water


DCT - distal convoluted tubule

responds to aldosterone, which is a steroid hormone that promotes sodium reabsorption, water follows and this results in concentrated urine and decreased urine volume.


Collecting Duct

Responsive to ADH and aldosterone. Reabsorbes H20 as permeability of CD increases. Hydrated= means it is impermeable to salt and H20. "point of no return"


Mechanism of Aldosterone

Basics= aldosterone is a steroid hormone that is secreted by adrenal cortex in response to low bp. How is low bp sensed ? Juxtaglom cells release renin. renin cleaves angiotensinogen to angiotensin I. Angiotensin I gets converted to angiotensin II via ACE. angiotensin II is what promotes the release of aldosterone. Mainly aldosterone alters the ability of DCT and CT to reabsorb sodium. so blood volume increases and bp will then increase. K ion and H ion excreted


Mechanism of ADH / Vasopressin

Peptide hormone synthesized by hypothal and released by posterior pit in response to increased blood osmolarity. This basically alters the permeability ofo the collecting duct allowing more water to be reabsorbed by making the cell junctions of the duct leaky. extension of this is alcohol and caffiene, which inhibit adh release and therefore can cause frequent excretion of dilute urine


What will happen if afferent arteriole constricts

bp drops and renin can be secreted to raise bp


osmotic pressure

sucking pressure that draws water into vasculature by all dissolved particles


oncotic pressure

osmotic pressure that is attributed to proteins specifically


blood osmolarity

290-300 mOsm/L


Bicarb buffer equation

Co2 (g) + H2o (l) H2Co3 (aq) H+ (aq) + HCo3 - (aq)