Urinary Study Guide

• the movement of substances from the blood within the glomerulus into the capsular space of the renal corpuscle due to pressure differences across the filtration membrane

• Seperated fluid - protein-free plasma

• the movement of substances from the tubular fluid back into the blood • all vital solutes and most water that was in the filtrate are reabsorbed- the excess solutes, some water, and waste products remain within the tubular fluid

• the movement of solutes, usually by active transport, out of the blood within the peritubular and vasa recta capillaries into the tubular fluid • materials are moved selectively into tubules to be eliminated or excreted from the body

-the filtration membrane is porous, thin, and negatively charged structure that is formed by the glomerulus and visceral layer of the glomerular capsule composed of: • Endothelium of fenestrated capillary • Basement membrane of capillary • Filtration slits of visceral layer

-allows plasma and its dissolved substances to be filtered, while restricting the passage of large structures such as the formed elements

• porous • composed of glycoprotein and proteoglycan molecules • restricts the passage of large plasma protein such as albumin while allowing smaller structures to pass

-composed of specialized cells called podocytes

• octopus like cells that have long, “foot-like” processes called pedicals that wrap around glomerular capillary to support it • pedicals are separated by thin spaces called filtration slits that are covered with membrane and prevent the passage of most small proteins

water glucose amino acids ions urea many hormones vitamin B and C ketones very small amounts of protein

HPg • blood pressure in the glomerulus that pushes water and some solutes out of the glomerulus and into the capsular space of the renal corpuscle • has a higher value than blood pressure of other systemic capillaries to allow for filtration to occur and is due to relative size of afferent and efferent arteriole • larger diameter of afferent arteriole than efferent arteriole

OPg • Osmotic pressure exerted by the blood IN • due to the dissolved solutes that it contains (most important is the plasma) • opposes filtration because it pulls fluids into glomerulus

HPc • The pressure in the glomerular capsule due to filtrate that is already present in the capsular space • opposes filtration

NFP • filtration occurs if the pressure that promotes filtration (HPg) is greater than the pressures that oppose filtration (OPg and HPc) • the difference in these pressures is the Net Filtration pressure • NFP = HPg – (HPc+OPg)

• important variable influenced by net filtration pressure • is defined as the rate at which the volume of the filtrate is formed and it is expressed as volume per unit time • the net filtration pressure directly influences the GFR-if HPg increases so does GFR

• important structure in regulating filtrate formation and systemic blood pressure • releases renin into the blood in response to low blood pressure or stimulation by the sympathetic nervous system

composed of: • Granular Cells • Macula Densa Cell

-modified smooth muscle cells of the afferent arteriole located near its entrance into the renal corpuscle

• They contract when stimulated either by blood pressure or the sympathetic division • they synthesize, store, and release the enzyme renin to decrease the GFR

required for the produciton of angiotensin I

• a group of modified epithelial cells in the wall of the distal convoluted tubule where it contacts the granular cells • located only on the tubule side next to the afferent arteriole and they are narrower and taller than other distal convoluted tubule epithelial cells

• detect changes in the sodium chloride (NaCl) concentration of tubular filtrate and signal granular cells to release renin though paracrine stimulated • Decreased BP=Decrease NaCl

• the intrinsic ability of the kidney to maintain a constant blood pressure and glomerular filtration rate despite change in systemic arterial pressure • allows the kidneys to produce urine at a constant rate despite fluctuations in systemic blood pressure

myogenic response tubuloglomerular feedback mechanism