Osmoregulation 

The absorption and excretion of water and dissolved substances so water balance is maintained between organisms and its surroundings

Osmoregulation in Marine Fish

1. Marine fish is hypoosmotic with its environment
2. Water is constantly lost by osmosis
3. Marine fish constantly drink, rarely urinate

Osmoregulation in Fresh Water Fish

1. Body of fresh water fish is hyperosmotic with its environment
2. Water constantly diffuses into the fish
3. Fresh water fish rarely drink, constantly urinate

Kidneys

A pair of bean-shaped organs that adjust how much water and salt the body excretes or saves

Cortex

Outer tissue zone of the kidney where the Bowmans capsule is located

Medulla

Inner tissue zone of the kidney where the loop of henle are

Renal Artery

Brings blood into the kidney

Renal Vein

takes blood out of the kidney

Ureter

Connects the kidney to the urinary bladder

Nephrons

• Filters water and solutes from blood, then reabsorbs adjusted amounts of both
• Each kidney contains more than a million nephrons

Bowman's Capsule

• A bulb-shaped body at one end where the nephron tube begins

Glomerulus

A dense ball of capillaries

Proximal Convoluted Tubule

• Starts at the Bowman's capsule and ends at the loop of Henle
• Where most reabsorption occurs

Loop of Henle

• Located in the medulla of the kidney
• Descending tube water leaves
• Ascending tube NaCl leaves

Distal Convoluted Tubule

• Starts at the loop of Henle and ends at the collecting duct

Collecting Duct

• Descends toward the center of the kidney and is shared by many nephrons
• Empties into renal pelvis

Glomerular Filtration

• First step in urine formation
• Blood enters glomerulus
• Glucose, amino acids, toxins, salts, leave capillaries and enters Bowman's capsule
• Red blood cells and proteins remain in the capillaries

Tubular Reabsorption

• Second step in urine formation
• occurs in proximal tubule
• 100% of glucose and aminos acids goes back into the capillaries

Concentrating the Urine

• More and more water leaves the descending loop of Henle concentrating the urea
• Ascending loop of Henle is impermeable to water and Na is pumped out with Cl following

ADH

• Antidiuretic Hormone
• When your body needs water hypothalamus stimulates the pituitary gland to secrete ADH
• ADH binds to distal tubules causing them to become more permeable and water moves out into the capillaries so less water is lost

Aldosterone

• Renin, an enzyme, is released that signals the adrenal gland to secrete aldosterone
• This hormone stimulates production of sodium-potassium pumps
• Pump more Na out and water follow it