Kidney Function and Nephron Structure

Study Notes

Glomerular Filtration: Blood pressure forces water and wastes from the glomerulus into Bowman's capsule.
Selective Reabsorption: Substances like water, glucose, amino acids, vitamins, and salts are reabsorbed back into the blood. This can be an active or passive process. Passive relies on diffusion and osmosis.
Tubular Secretion: Substances not filtered or reabsorbed are actively secreted into the filtrate.

Nephron: The functional unit of the kidney consists of the corpus Malpighi and the convoluted tubules. - The corpus Malpighi contains the glomerulus (a network of capillaries) and Bowman's capsule. - Convoluted tubules include the proximal convoluted tubule, loop of Henle, and the distal convoluted tubule.
Structure of the Nephron: The structure of the Nephron is critical to its function. It is long, coiled and has specific cells enabling maximum reabsorption. The Bowman's capsule is cup shaped, which provides a large surface area for filtration. The proximal convoluted tubule has a large surface area for reabsorption. The loop of Henle further concentrates and regulates water reabsorption.

Glomerulus: The afferent arteriole (bringing blood to the glomerulus) is larger than the efferent arteriole. This higher input pressure forces waste products into the Bowman's capsule.
Podocytes: Specialized filtration cells in Bowman's capsule improve filtration efficiency.
Bowman's Capsule: Cup-shaped with a large surface area to maximize filtration.

Hypothalamus Receptors: Detect low blood water levels.
ADH Release: Pituitary gland releases ADH.
Increased Permeability: Renal tubules become more permeable to water.
Water Reabsorption: Increased water reabsorption into blood.
Normal Water Levels: Water levels in the blood return to normal.
Excessive Water: Receptors in the hypothalamus that are stimulated by excess water will reduce ADH production.
Reduced Permeability: Reduced water reabsorption to remove the excess water and reduce blood water levels.

High Blood Salt Levels: Receptors detect high blood salt.
Aldosterone Release: Adrenal gland releases aldosterone.
Reduced Permeability: Renal tubules are less permeable to salt; more salt is excreted with urine.
Normal Salt Levels: Salt levels in the blood return to normal.
Low Blood Salt Levels Triggers release of more aldosterone. Increases permeability for salt reabsorption and excretes less salt into urine to return to healthy levels.

Kidney Stones: Hard crystals form in the kidneys.
Kidney Failure: Impaired kidney function requiring dialysis or transplantation.
Dialysis: A process to filter blood when kidneys fail.
Kidney Transplant: Replacing failing kidneys with healthy ones.