Human Urinary System: Structure, Function & Urine Formation PDF

The Human Urinary System: Structure, Function, and Urine Formation  Recall The urinary system is crucial for maintaining homeostasis in the body Main functions: Waste elimination Regulation of blood volume and composition Hormone p...

The Human Urinary System: Structure, Function, and Urine Formation  Recall The urinary system is crucial for maintaining homeostasis in the body Main functions: Waste elimination Regulation of blood volume and composition Hormone production Key components: renal arteries, kidneys, ureters, bladder, and urethra  Image Detail Renal Arteries Pair of blood vessels that branch off from the abdominal aorta Function: Supply oxygenated blood to the kidneys Characteristics: Approximately 5mm in diameter Carry about 20% of the cardiac output Kidneys: Structure and Function Bean-shaped organs located in the lower back Functions: Filter blood Regulate blood pressure Produce hormones (e.g., erythropoietin) Composed of: Outer cortex Inner medulla Renal pelvis  Ureters Image Detail Pair of thin tubes connecting kidneys to the bladder Function: Transport urine from kidneys to bladder Characteristics: 25-30 cm long Muscular walls that contract to move urine (peristalsis)  Image Detail Urinary Bladder Hollow, muscular organ that stores urine Functions: Temporary urine storage Urine expulsion through urination Characteristics: Expandable (can hold up to 600 mL) Contains stretch receptors to signal fullness Image Detail Kidney Structure: Nephrons Nephron: functional unit of the kidney Each kidney contains about 1 million nephrons Components of a nephron: Renal corpuscle (glomerulus + Bowman's capsule) Proximal convoluted tubule Loop of Henle Distal convoluted tubule Collecting duct Image Detail The Glomerulus Ball of capillaries within Bowman's capsule Function: Filtration of blood Characteristics: High blood pressure Image Detail Urine Formation: Stage 1 - Filtration Occurs in the glomerulus Process: Blood pressure forces fluid through filtration barrier Small molecules (water, ions, glucose, amino acids) pass through Large molecules (proteins, blood cells) remain in blood Result: Formation of glomerular filtrate in Bowman's capsule Urine Formation: Stage 2 - Reabsorption Occurs mainly in proximal convoluted tubule and Image Detail loop of Henle Process: Useful substances are reabsorbed into blood Includes water, glucose, amino acids, and ions Types of transport: Active transport (against concentration gradient) Passive transport (with concentration gradient) Urine Formation: Stage 3 - Secretion Occurs mainly in distal convoluted tubule and Image Detail collecting duct Process: Substances are secreted from blood into tubule Includes H⁺ ions, K⁺ ions, and drugs Function: Fine-tuning of urine composition Regulation of blood pH  Types of Transport in the Nephron Passive transport: Diffusion: movement along concentration gradient Osmosis: water movement across semipermeable membrane Active transport: Primary active transport: uses ATP (e.g., Na⁺/K⁺ pump) Secondary active transport: uses concentration gradients created by primary active transport  Hormonal Regulation of Urine Formation Antidiuretic Hormone (ADH): Increases water reabsorption in collecting duct Aldosterone: Increases Na⁺ reabsorption and K⁺ secretion Atrial Natriuretic Peptide (ANP): Increases Na⁺ and water excretion  Review and Key Takeaways The urinary system is essential for waste elimination and homeostasis Key structures: renal arteries, kidneys, ureters, bladder Nephron is the functional unit of the kidney Urine formation involves three stages: filtration, reabsorption, and secretion Various transport mechanisms and hormones regulate urine composition