Chapter 26: The Urinary System

Introduction

• Focus on the anatomy of the renal system.
• Functions involve removal of waste products from metabolic activity.
• Kidneys produce urine to eliminate these wastes.

Components of the Urinary System

• Kidneys: Two organs that filter waste.
• Ureters: Tubes that transport urine from the kidneys to the bladder.
• Urinary Bladder: Stores urine.
• Urethra: Excretes urine from the body.
• Urination/Micturition: Process of excreting urine.

Functions of the Urinary System

• Excretion: Removal of metabolic wastes from body fluids.
• Elimination: Removal of wastes from the body.
• Homeostasis Maintenance:
  • Regulating blood volume and pressure.
  • Controlling solute concentration, including sodium.
  • Regulating pH of blood by controlling hydrogen and bicarbonate ions.

Hormonal Regulation

• Erythropoietin: Involved in blood cell production.
• Renin: Part of the renin-angiotensin-aldosterone system.
• Calcitriol: Helps absorb calcium in the intestines.

Anatomy of the Kidneys

• Located posteriorly, under the ribcage.
• The left kidney is slightly higher than the right due to the liver.
• Adrenal Glands: Sit atop kidneys.
• Retroperitoneal Organs: Positioned behind the peritoneum.
• Protective Layers:
  • Fibrous Capsule: Tough outer layer.
  • Perinephric Fat: Adipose tissue around kidneys.
  • Renal Fascia: Connective tissue holding kidneys in place.

Internal Structure of the Kidneys

• Cortex: Outer portion, granular appearance.
• Medulla: Contains pyramids and columns.
• Pyramids: Seashell-shaped structures.
• Columns: Located between pyramids.
• Lobes: Composed of pyramids, columns, and surrounding cortex.
• Urine Production: Occurs in nephrons within cortex and medulla.

Circulation and Blood Supply

• Renal Artery: Supplies oxygenated blood (25% of cardiac output).
• Renal Vein: Removes deoxygenated blood.
• Blood travels through lobar arteries to arcuate arteries for nephron function.

Nephron: Functional Unit

• Renal Corpuscle: Includes glomerular/Bowman's capsule and glomerulus.
• Renal Tubules: Process filtrate from corpuscle.
• Glomerulus: Ball of yarn-like capillaries for filtration.
  • Afferent Arteriole: Blood enters.
  • Efferent Arteriole: Blood exits.
• Capsular Space: Space between layers of the glomerular capsule.

Specialized Cells in Kidneys

• Mesangial Cells: Supportive, involve filtration, phagocytosis, and capillary regulation.
• Podocytes: Have foot processes forming filtration slits around glomerular capillaries.

This concludes the detailed overview of the urinary system, focusing on anatomy, function, and the critical role of the nephrons and hormonal regulation in maintaining bodily homeostasis.