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Salt and Water Relationship

• Adding salt to blood draws water via concentration gradient.

• Osmotic gradient is controlled indirectly through ions.

Kidney Functions

• Maintain balance of water, salts, and acids/bases.

• Secrete renin to manage blood pressure.

• Release erythropoietin (EPO) for red blood cell production in low oxygen conditions.

• Convert vitamin D to active form.

• Remove metabolic waste, primarily nitrogenous waste like urea.

Nitrogenous Waste

• Major waste from protein metabolism; ammonia is toxic.

• Terrestrial mammals excrete urea to conserve water; birds excrete uric acid for greater water efficiency.

Kidney Anatomy

• Kidneys filter blood constantly, receiving significant blood flow despite being only 1% of body weight.

• Retroperitoneal position behind the peritoneum membrane.

Urinary System Overview

• Ureters transport urine from kidneys to bladder through peristalsis.

• Ureters have a tri-layered wall structure: epithelial mucosa, smooth muscle, fibrous connective layer.

• Urinary bladder is a muscular and collapsible storage organ for urine.

Urinary Bladder Features

• Contains trigone area which is smooth and stable for ureter entry.

• Four layers: epithelial mucosa, elastic connective tissue, smooth muscle, and serous coat (parietal peritoneum).

• Receptors in the bladder help monitor fullness without high internal pressure.