A&P II TEST 4

Order of how things move through nephrons

Blood arrives by afferent arterioles and leaves by efferent. Glomerulus>PCT>Nephron loop (descending then ascending)>DCT>Collecting duct>papillary duct>minor calyx

Effects of Angiotensin II

Contraction of vascular smooth muscle in peripheral capillary beds Increased aldosterone secretion by adrenal glands -increases NA+ retention Increased arterial pressures Stimulation of thirst centers Increased production of ADH OVERALL: increase in systemic blood pressure and blood vol and restoration of normal GFR

Hormonal regulation

Increase blood vol. -Automatic increases GFR to promote fluid loss -If increse in blood vol is severe, hormonal factors further increase GFR

Net filtration pressure

NFP=NHP-BCOP

Natriuretic peptides

Release by heart in response to stretched walls due to increased blood vol or pressure Atrial natriuretic peptide (ANP) is released by atria Trigger dilation of afferent glomerular arterioles and constriction of efferent glomerular arterioles Increase glomerular pressures and increase GFR ANP also decreases sodium reabsorption Net result is increased urine production and decreased blood vol and pressure

Macula densa and Juxtaglomerular cells

The epithelial cells of DCT near the renal corpuscle are taller than those elsewhere along the DCT. THeir nuclei are clustered together this region is the mascula densa. The cells of the mascula densa are closely related to smooth muscle fibers in the walls of the arteriole (act as a bariorecipetor: secretes renin)

RAAS

activated when there is decreased blowflow to kidneys (by loss of blood vol.) or drop in blood pressure. Increases salt and water reasborption. Three stimuli cause juxtaglomerular complex to release renin. Decrease in blood pressure at glomerulus due to decrease in blood vol, decrease in systemic pressure, or blockage of renal artery Stimulation of juxtaglomerular cells by sympathetic innervation Decrease in osmotic concentration of tubular fluid at macula densa renin converts inactive angiotensinogen to inactive angiotensin I Angiotensin I is converted to angiotensin II by angiotensin-converting enzyme (ACE) (capillaries of lung)

Layers of filtration membrane of renal corpuscle

fenestrated endothelium, podocyetes, and basement membrane

basic structures how urine flows

kideny>ureters>urinary bladder>urethera

Capsular hydrostatic pressure (CsHPP

opposes GHP. CsHP, which tends to push water and solutes out of the filtrate and into the plasma, results from the resistance of filtrate already present in the nephron that must be pushed toward the renal pelvis. The difference between GHP and CsHP is the net hydrostatic pressure (NHP)

Specialized cells in renal corpusels

podocytes. Their pedicles ("foot projections") material passing out of the blood at the glomerulus must be small enough to pass through the narrow filtration slits between adjacent pedicels. *Large cells of viseral layer. fenstrated. Mesangial cells lie between adjacent capillaries. Have actin like filaments to enable them to contract. To control capilary diameter and the rate of capillary blood flow. *located among glomerular capillaries *specialized cells derived from smooth muscle: contain the protien actin; allows cells to contact which controls diameter of capillaries. *provide support, filtration, and phagocytosis

Primary function of the PCT

reabsorption of organic nutrients active reabsorption of ions re absorption of water passive re absorption of ions: secretions: secretion of H ions *Reabsorption of ions

functions of the urinary system

regulates blood vol and pressure regulation of plasma concentration of certain ions stabilization of blood pH Conserving nurients

Blood Colloid Osmotic Pressure (BCOP)

tends to draw water out of the filtrate and into the plasma; thus opposes filtration. Over the entire length of the glomerular capillary bed, the BCOP averages about 25mmHg.

Glomerular filtration rate (GFR)

the amount of filtrate the kidneys produce each minute. (125 mL/minute)

Glomerular hydrostatic pressure (GHP)

the blood pressure in the glomerular capillaries. This pressure tends to push water and solute molecules out of the plasma and into the filtrate. The GHP, which averages 50mmHg, is significantly higher than capillary pressures elsewhere in the systemic circut, because the efferent arteriole is smaller in diameter than the afferent arteriole.

Net filtration pressure (NFP)

the net pressure acting across the glomerular capillaries. It represents the sum of the hydro static pressures and the colloid osmotic pressures. Under normal circumstances the net filtration pressure is approx 10mmHg. This is the average pressure forcing water and dissolved substances out of the glomerular capillaries and into the capsular space.