Excretory System
- Introduction
• The excretory system removes waste products and maintains fluid and electrolyte balance in the body.
• Main excretory organs include the kidneys, ureters, urinary bladder, and urethra.
• It also involves other organs that expel waste like lungs (CO2), skin (sweat), and liver (metabolic waste) but focus is on the urinary system. - Main Organs of the Excretory System
A. Kidneys
• Pair of bean-shaped organs located retroperitoneally on either side of the spine.
• Functions:
• Filter blood to remove waste and excess substances.
• Regulate water and electrolyte balance.
• Produce urine.
• Produce hormones like erythropoietin (stimulates RBC production) and renin (regulates BP).
B. Ureters
• Muscular tubes connecting kidneys to urinary bladder.
• Transport urine by peristalsis.
C. Urinary Bladder
• Hollow, muscular organ that stores urine.
• Can expand and contract.
D. Urethra
• Tube that carries urine from the bladder to outside the body.
• Shorter in females, increasing risk of urinary infections. - Microscopic Structure and Function of Kidney
A. Nephron
• Functional unit of the kidney (~1 million per kidney).
• Components:
• Renal corpuscle: glomerulus + Bowman’s capsule; site of blood filtration.
• Renal tubule: proximal convoluted tubule, loop of Henle, distal convoluted tubule; reabsorbs needed substances and secretes wastes.
• Collecting ducts collect urine from multiple nephrons.
B. Blood Supply
• Renal artery supplies blood.
• Blood filtered in glomerulus.
• Filtered blood leaves through renal vein. - Process of Urine Formation
A. Filtration
• Blood plasma filtered from glomerulus into Bowman’s capsule.
• Filters out water, salts, glucose, urea, and wastes.
B. Reabsorption
• Useful substances (water, glucose, amino acids, ions) reabsorbed back into blood from tubules.
C. Secretion
• Additional wastes secreted into tubules from blood.
D. Excretion
• Final urine collected in collecting ducts → renal pelvis → ureters → bladder → urethra. - Functions of the Excretory System
• Removes metabolic wastes (urea, creatinine, uric acid).
• Maintains electrolyte balance (Na+, K+, Ca2+).
• Regulates acid-base balance (pH).
• Controls blood volume and pressure via water regulation.
• Produces hormones controlling erythropoiesis and blood pressure. - Other Excretory Organs and Their Role
A. Lungs
• Remove carbon dioxide and small amounts of water vapor.
B. Skin (Sweat Glands)
• Excretes water, salts, and small quantities of urea through sweat.
C. Liver
• Breaks down toxins and produces urea from ammonia (a toxic substance). - Common Disorders of Excretory System
• Urinary Tract Infection (UTI)
• Nephrolithiasis (Kidney stones)
• Chronic Kidney Disease (CKD)
• Acute Renal Failure
• Glomerulonephritis (inflammation of glomeruli)
• Nephrotic Syndrome (protein loss in urine)
• Urinary incontinence - Nursing Care and Considerations
• Monitor urine output, color, and odor.
• Assist with catheterization if needed.
• Encourage fluid intake to prevent infections and stones.
• Educate patients on hygiene to prevent UTI.
• Monitor electrolyte levels in blood tests.
• Support patients with dialysis if necessary.
• Watch for symptoms of urinary retention or dysuria. - Summary for Quick Review
The excretory system primarily includes the kidneys, ureters, bladder, and urethra, working together to remove metabolic wastes and maintain fluid and electrolyte balance. The functional unit, the nephron, filters blood, reabsorbs vital substances, secretes wastes, and forms urine. Urine travels from kidneys through ureters to the bladder and is expelled via the urethra. The skin, lungs, and liver also contribute to waste removal. Nursing care focuses on monitoring urinary function, preventing infections, managing chronic conditions, and educating patients on maintaining a healthy excretory system.