25%

Glomerulus and Bowman’s Capsule

Blood is constituted of water (Solvent). RBC, WBC, and platelets are suspended in water.

Antidiuretic hormone, secreted in posterior pituitary gland

1%

Outer cortical region and inner medullary region.

The volume of fluid filtered from the glomerular capillaries into the Bowman’s capsule per unit time. This can be useful measure of glomerular function both under normal physiological conditions and in disease cases.

Water

ADH and RAAS – aim to reabsorb water
ANP – increases water excretion

Angiotensin I is converted into Angiotensin II by angiotensin converting enzyme (ACE).
This enzyme is found on capillary endothelium of lungs.

Upper: kidney and ureter
Lower: bladder and urethra

The glomerular basement
- a membrane, which lies between the endothelium and the podocytes (noncellular and is composed of collagen, or collagen like proteins in a glycoprotein matrix and is negatively charged) acts as the main filtration barrier.

Cells of the PCT secrete substances into the lumen, including xenobiotics such as penicillin. Penicillin is excreted in high concentrations and would be most ideal in combating UTIs.

Increased plasma osmolality, decrease blood pressure, decrease blood volume, increase angiotensin II, sympathetic stimulation, dehydration.

•It is a function of the kidney to maintain plasma osmolality within very narrow limits (within 1%), or else cell function is compromised.
•If plasma osmolality is too high net movement of H2O out of cell.
•If plasma osmolality is too low net movement of H2O into cell.

Sheep – bean shaped
Cat – bean shaped with prominent veins seen (almost transparent and highly vascularized)
Horse – not bean shaped and asymmetrical. One is heart shaped and another is lobed
Pig – elongated kidney.

Our big plasma proteins, such as albumin, are so important because their oncotic pressures are exerting a pull that is retaining H2O in circulation, so it’s excess water is not being excreted in urine. There is a problem in circulation balance if there is a decreased concentration of albumin because it alters the net filtration pressure, which is important in ensuring proper filtration in the glomerulus.

Bowman’s capsule, proximal tubule, descending limb, loop of Henle, ascending limb, distal tubule, collecting duct to bladder.

- Important in regulating renal function and regulating plasma volume. ANP secretion:
- Inhibits secretion of renin, aldosterone, and ADH causes net effect of ANP is increase Na+ and increase H2O excretion.
- Causes vasodilation and decreases vascular resistance.

ADH has cells on the late distal tubule and collecting duct. If ADH binds to vasopressin receptors on the cell membrane, it will induce the insertion of aquaporins, allowing for water to move from the tubule lumen in a transcellular fashion into the medullary interstitum and ultimately back. URINE BECOMES MORE CONCENTRATED

• Elimination of waste substances from plasma
• Salvage of essential compounds from filtrate
• Regulation of ion levels
• Maintenance of plasma osmolality cells.
• Regulation of plasma volume, which regulates blood pressure
• Production of hormones

• Single layer of endothelial cells – line the glomerular capillaries and restrict the passage of blood cells
• Basement membrane – serves as a scaffold. Podocytes are anchored to this. The pore size between the podocytes serve as a barrier that allows the transit of specific sized molecules
• Single layer of visceral epithelial cells (podocytes) line the bowman’s capsule and restrict the passage of merium-sized proteins and phagocystose macromolecules.

Diffusion – random movement from high to low concentration
Facilitated diffusion: proteins act as carriers or pores to permit flux of substances that can’t diffuse directly through the membrane. Still moves from high to low concentration (passive movement)
Primary active transport – proteins in membrane act like pumps to move ions or small molecules up concentration gradient (low to high). Requires energy (ATP)
Secondary Active Transport – uses proteins similar to those for facilitated diffusion. Requires energy.

- When Na+ levels are low in the tubular fluid of the DCT, macula densa cells cause juxtaglomerular cells (granular cells) of the afferent arteriole to secrete renin (a proteolytic enzyme) into blood.
- Renin converts angiotensinogen (a plasma peptide) into angiotensin I. Angiotensin I is converted into Angiotensin II by angiotensin converting enzyme (ACE).
- Angiotensin II acts on zona glomerulosa cells of the adrenal cortex. Adrenal cortex secretes the hormone aldosterone into the blood.
- Aldosterone stimulates synthesis and insertion of the epithelial sodium channel (ENaC) and a sodium pump in distal tubule and collecting ducts. This will consequentially promote Na+ reabsorption from tubular fluid and K+ secretion to tubular fluid.
- Sodium is the principal determinant of extracellular fluid volume and plasma volume. Reabsorption of Na+ by PCT is active. Na+ reabsorption is regulated in the distal tubule and collecting ducts via the action of aldosterone – aldosterone provides level of discretionary reabsorption of Na+.
- WATER FOLLOWS Na+ ALWAYS increased water reabsorption as well increased extracellular fluid volume.

• A decrease in blood pressure of volume will stimulate ADH secretion. Blood pressure changes are sensed by baroreceptors (stretch receptors) in the aortic arch and carotid sinus which responds to stretch. If there is a decrease in blood volume, decrease in BP, and a decrease firing of these baroreceptors ADH secreted increased water retention increased plasma osmolality within the circulation increased blood volume increase blood pressure.