Urinary System Overview

Urinary System Overview

• The kidneys perform 5 homeostatic functions: regulating blood volume and blood pressure, regulating plasma ion concentrations, stabilizing blood pH, conserving valuable nutrients (like glucose), and assisting the liver in detoxification.
• Kidneys are bean-shaped and retroperitoneal, held in place by three layers of connective tissue: renal fascia, adipose capsule, and renal capsule.
• Kidneys receive 20-25% of the total cardiac output (1200 mL of blood per minute).
• Blood reaches the kidneys via the renal artery.
• Kidneys weigh 150g each.
• Urine exits the kidney through the hilum, which is also where the renal artery, vein, nerves, and ureters pass through.
• The hilum leads to the renal sinus cavity, which contains urine-draining structures and adipose tissue.

Kidney Structure

• The kidney has three distinct regions: cortex, medulla, and pelvis.
• The renal cortex and medulla form the urine-producing portion of the kidneys.
• The renal pelvis and associated structures drain the urine.

Renal Corpuscle and Renal Tubule

• The renal corpuscle filters blood, and it consists of the glomerulus and Bowman's capsule.
• The glomerulus is a network of fenestrated capillaries.
• Bowman's capsule is an outer epithelial sheath that surrounds the glomerulus.
• The renal tubule processes the filtrate and is divided into the proximal convoluted tubule (PCT), nephron loop (loop of Henle), and distal convoluted tubule (DCT).

Nephron Types

• There are two main types of nephrons: cortical nephrons and juxtamedullary nephrons.
• Cortical nephrons are primarily located in the renal cortex.
• Juxtamedullary nephrons have a long nephron loop extending deep into the renal medulla.

Urine Production

• Urine production involves four processes: filtration, reabsorption, secretion, and excretion.
• Filtration occurs at the glomerulus, where liquid components of the blood are filtered into Bowman's capsule.
• Reabsorption (of needed substances) takes place in the renal tubules.
• Secretion (of waste products) occurs in the tubules.
• Excretion is the final removal of urine.

Urine Drainage

• Urine flows from minor calyces into major calyces and into the renal pelvis.
• The renal pelvis connects to the ureters.

Micturition (Urination)

• Micturition involves voluntary and involuntary muscles.
• Urinalysis examines urine composition for diagnosing diseases.
• Urine color, ranging from clear to dark, can indicate concentration levels (more concentrated urine is darker).
• Cloudy urine might indicate infection or high protein levels.