lec 3 PT 2 water/electrolyte balance

define KIDNEY and what 2 things it functions in

-excretory organ of vertebrates

-function in EXCRETION and OSMOREGULATION

2 distinct regions of kidney? how many sections is one of them divided into and what is section called and what shape

1. Outer renal cortex

2. Inner renal medulla (divided into EIGHT OR MORE triangle sections called renal pyramids)

whats the functional unit of kidney

nephron

what does the nephron consist of?

single long tubule and ball of capillaries called glomerulus, which is surrounded by the Bowman’s capsule which revieves filtrate from glomerulus capillaries

where does filtration occur? describe what happens with glomerulus and bowmans capsule when it occurs

at renal corpuscle

-filtration occurs as BLOOD PRESSURE forces fluid from blood in glomerulus to lumen of bowman’s capsule

whats the renal corpuscle

-where filtration occurs

-MADE OF GLOMERULUS and BOWMAN’S CAPSULE

what are the pores of the glomerulus capillaries called? what are popdocytes? what are these 2 things permeable to?

-fenestrated endothelium (pores of capillaries)

-podocytes (capsule cells (specialized epithelial cells in which foot processes are wrapped around glomerular capillaries that fold into series of narrow gaps called filtration slits)

-these are permeable to SMALL molecs (water, salts, glucose, aa, vitamins, nitrogenous wastes) BUT NOT TO BLOOD CELLS or PLASMA PROTEINS

what is GFR and what it stand for

GFR: Glomerular Filtration Rate is the VOLUME of glomerular filtrate formed by kidneys PER MINUTE

list the 3 kinds of Intrinsic (self) regulation of GFR (globerular filtration rate) which is rapid

1. Myogenic response (rapid)

2. Tubuloglomerular feedback (slower)

3. Mesangial control

describe this kind of intrinsic self regulation of GFR: Myogenic response and what are the 2 purposes

Myogenic response: RAPID RESPONSE: afferent arteriole smooth muscle cells contract or relax due to changes in blood pressure

-when bp increase, arteriole wall stretch = trigger rapid contraction of smooth muscle = constrict afferent arteriole = reduce glomerular blood flow and GFR

PURPOSES:

1. PROTECT glomerulus from damage from high pressures

2. MAINTAIN STABLE GFR when bp rises

describe this kind of intrinsic self regulation of GFR and describe what happens when GFR increase vs decrease. Tubuloglomerular feedback

Tubuloglomerular feedback: SLOWER response. links the composition of tubular filtrate in nephron to maintain stable GFR

-macula densa cells of distal tubule sense sodium chloride levels in distal tube and send signal to smooth muscle cells of afferent arteriole

-if GFR INCREASE, flow of sodium chloride to macula densa cell INCREASE = cause the cells to release ATP signal (then converted to adenosine) - and the adenosine binds to receptors on smooth muscle cells to cause VASOCONSTRICTION of afferent arteriole = lower GFR back to normal levels

-if GFR DECREASE, flow of sodium chloride to macula densa cell DECREASE = no adenosine generated = lead to VASODILATION of afferent arteriole = increase GFR back to normal levels