The urinary system is simpler in terms of the number of organs compared to the digestive system.
Main focus on kidneys and their functions in the body.
Functions of the Urinary System
Waste Removal:
Filters blood to remove metabolic wastes.
Types of metabolic wastes:
Carbon dioxide, excess water, excess salts/ions.
Nitrogenous Wastes:
Urea: Main nitrogenous waste in humans, a product of protein metabolism.
Ammonia: Not produced much by humans due to its toxicity.
Uric Acid: Can cause gout if accumulated; produced from excess protein intake.
Blood Chemistry Regulation:
Maintains blood pH, osmotic pressure, and volume.
Produces hormones like erythropoietin, which regulates red blood cell production.
Produces calcitriol for vitamin D production.
Organs of Excretion
Lungs: Remove carbon dioxide and excess water vapor.
Skin: Sweats out water, salts, and urea.
Liver: Metabolizes proteins, removes nitrogen to form urea.
Main Organs of the Urinary System
Kidneys:
Retroperitoneally located, protected by vertebral ribs.
Receive 20% of cardiac output for filtration.
Composed of over a million nephrons for filtration.
Ureters:
Transport urine from kidneys to the bladder by peristalsis.
Urinary Bladder:
Stores urine until voiding (micturition).
Urethra:
Single tube for expelling urine, regulated by internal and external sphincters.
Kidney Structure
Fibrous Capsule: Outer layer protecting the kidney.
Renal Cortex: Outer zone, site of filtration, contains nephrons.
Renal Medulla: Inner zone, contains pyramids, columns, and papilla.
Renal Sinus: Hollow area within the kidney.
Urine Flow Path:
Through minor calyces, major calyces, renal pelvis, ureter, bladder, urethra.
Blood Supply of the Kidneys
Renal Artery: Brings blood to the kidney.
Segmental, Interlobar, Arcuate, Cortical Radiate Arteries: Pathway of blood within kidney.
Cortical Radiate, Arcuate, Interlobar, Renal Veins: Pathway of blood out of the kidney.
Nephrons
Types: Cortical (short, most common) and Juxtamedullary (longer, less common).
Functions:
Filtration: Glomerular filtration in renal corpuscle.
Reabsorption: Obligatory and facultative reabsorption of water and nutrients.
Secretion: Tubular secretion of ions/toxins in distal convoluted tubule.
Urine Collection: Via collecting ducts and papillary ducts.
Functions in Blood Regulation
Adjusts blood pH, volume, and chemistry through filtration, reabsorption, and secretion processes.
Influenced by hormones such as ADH and aldosterone.
Conclusion
Understanding kidney structure and nephron function is crucial for comprehending how the urinary system maintains homeostasis through waste removal and blood regulation.