Urinary System
Why do we urinate? To remove metabolic wastes from body Cells produce wastes that are toxic Nitrogenous wastes are converted to urea by the liver Urea
Why do we urinate? To regulate solute concentration of blood varying amount of water excreted [solutes = dissolved substances] To regulate pH - varying amount H+ secreted
Components of the urinary system Kidney: Forms urine, regulates solute concentration & pH of blood Kidney Ureter: Transports urine to bladder Ureter Urinary bladder: Stores urine until expelled Urinary bladder Urethra Urethra: Transports urine to outside of body
Anatomy of the kidney 3 major parts Renal Cortex Renal Medulla Renal Pelvis
Anatomy of the kidney Microscopic tubules Produce urine The functional unit of the kidney is called a nephron There are millions of nephrons in each kidney Microscopic tubules Produce urine
Nephron Structure glomerulus
How do Kidneys Work? Kidney contains lots of nephrons microscopic tubules high surface area for processing blood Nephrons are composed of: A knot of capillaries inside the nephron capsule tubules (proximal tubule nephron loop distal tubule.) Capillary network around the tubules
Three Steps of Urine Formation Filtration small substances are filtered out of the blood into the nephron capsule includes waste products, urea, water, salts, nutrients
Three Steps of Urine Formation Reabsorption nutrients such as glucose and amino acids are reabsorbed into the blood selective process: active transport Na+ is actively pumped back to the blood, then water follows by osmosis
Three Steps of Urine Formation Secretion Additional molecules from blood move into tubules. uric acid, ammonia, hydrogen ions, penicillin
After Urine is Formed Urine moves down collecting tubules into renal pelvis Passes into ureters which carry it to urinary bladder Stored in the bladder until it is excreted through the urethra