Transcript Kidney
Excretion • Purpose: - Maintain Homeostasis – Keeping the “status quo” externally and internally • Function: Rids body of metabolic wastes – Salts, Carbon Dioxide, Urea • Excretory Organs – Skin – water and salts – Lungs – CO2 – Kidneys and associated organs - Urea The Excretory System ((Liquid/salts) • Kidneys (2, lower back) – Filtration system urine • Ureters – Tubes carrying urine from kidneys to bladder • Urinary bladder – Saclike organ where urine is stored • Urethra – Tubes from which urine is released from the body Excretory System Vein Kidney (Cross Section) Cortex Medulla Kidney Ureter Urinary bladder Urethra Artery Kidney Nephron Bowman’s capsule Cortex Capillaries Glomerulus Medulla Renal artery Renal vein Ureter Collecting duct Vein To the bladder Artery Loop of Henle To the ureter Structure of Kidney • Renal Cortex – outer portion • Renal Medulla – Inner portion (loop of Henley) • Nephrons – Straddle the cortex and medulla – Functional unit of kidneys; filters blood • Flow – Blood enters arteriole capillaries (filtration) waste products accumulate in collecting duct Duct joins ureter Function of Kidney • Purification of blood • Three processes: – Filtration, – Reabsorption – Secretion Filtration Most filtration occurs in the glomerulus. Blood pressure forces water, salt, glucose, amino acids, and urea into Bowman’s capsule. Proteins and blood cells are too large to cross the membrane; they remain in the blood. The fluid that enters the renal tubules is called the filtrate. Reabsorption As the filtrate flows through the renal tubule, most of the water and nutrients are reabsorbed into the blood. The concentrated fluid that remains is called urine. Secretion Substances such as hydrogen ions are transferred from the blood to the filtrate. Nephron • Bowman’s capsule – Found in Cortex – Contains glomerulus (capillary bed) and collecting duct – Filters the blood (extracts waste products) • Renal tubes – Reabsorb essential nutrients (glucose and aa) – Secrete H+ • Loop of Henle – Found in medulla – Water conservation (reabsorb) Result: • Purified blood returned to circulatory system • Urine is collected in the bladder – Released through the urethra Kidneys • Regulate water and waste content of blood – Blood volume, pH, waste products – Really controlled by blood levels • What happens when you drink more water? • What happens if you eat salty food? Dialysis • Artificial cleansing of the blood