Kidney Function and Nephron Structure

Processes of the Kidney

• 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.

The Functional Unit of the Kidney

• 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.

Adaptations of Kidney Parts

• 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.

Water Balance (ADH)

• 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.

Salt Balance (Aldosterone)

• 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 Diseases

• 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.