Ch 14 Part 3 -- Urinary System -- VTPP 435

Ch 14 Part 3 -- Urinary System -- VTPP 435

Lateral Spaces

-gaps between adjacent cells, where there is interstitial fluid
-tight junctions between cells

Transepithelial Transport

1. Luminal Cell Membrane
2. Cytosol
3. Cross Basolateral Cell Membrane
4. Interstitial Fluid
5. Capillary Wall

Distal and Collecting Tubules Na+ Reabsorption

-subject to hormonal control
-regulates ECF volume to control arterial blood pressure

Renin

-enzymatic hormone
-secreted by granular cells of juxtaglomerular apparatus
-secreted when NaCl low, ECF volume low, and arterial BP low

3 ways Granular Cells are stimulated to secrete renin

1) granular cells intrarenal baroreceptors, low BP in afferent arteriole makes high renin
2) low NaCl causes Macula Densa cells to secrete renin
3) if BP low, sympathetic stimulation increases renin from granular cells from the baroreceptor reflex

2 Types of Cells in Distal and Collecting Tubules

1) Principal cells - where aldosterone and ADH act
2) Intercalated cells -- control acid-base balance

Aldosterone

-inserts more Na+ leak channels in luminal membrane & more Na+-K+ pumps on basolateral membrane to increase Na+ reabsorption
-triggered by low NaCl, low plasma volume, low arterial BP

Angiotensin II

-constricts arterioles --> increase total peripheral resistance
-causes increase thirst --> high ADH --> high plasma vol, and high arterial pressure

Atrial Natriuretic Peptide (ANP & Brain Natriuretic Peptide (BNP)

-peptide hormones
-cause excretion of Na+ a lot
-produced by heart
-triggered by heart muscle cell stretch due to high ECF volume
-inhibit renin and aldosterone
-dilate afferent arterioles and constrict efferent arterioles
-relax glomerular mesangial cells
-reduce cardiac output

Filtered Load

-quantity of any substance filtered per minute
-plasma concentration x GFR of the substance

Glucose Regulation

-glucose plasma concentration maintained by endocrine and liver mechanisms
-glucose usually not in urine because kidney holds onto glucose

Phosphate Regulation

-kidneys maintain needed phosphate plasma and urinate excess
-subject to hormonal control

Water Reabsorption

-passively reabsorbed thru aquaporins in tubular cells
-osmotically follows Na+ reabsorption
-also effected by plasma-colloid osmotic pressure

Urea Reabsorption

-a waste product from breakdown of protein
-passively reabsorbed from concentration gradient that is produced by H20 reabsorption in proximal tubule

Chloride Reabsorption

-passively reabsorbed down electrical gradient
-electrical gradient caused by Na+ active reabsorption