Outline-2, BIO 3220, Urinary System


A. Kidney

1. Overall function

a. Osmoregulation

b. Nitrogenous waste in Tetrapods

1. Ammonia in amphibians

2. Urea in mammals

3. Uric Acid in birds and reptiles

2. Nephron – Functional unit of kidney; makes urine by filtering blood

a. Glomerulus – Network of blood capillaries

1. Afferent glomerular arteriole

2. Efferent glomerular arteriole

b. Bowman’s capsule – Cup-shaped around glomerulus to “catch” filtrate

c. Renal Corpuscle – Glomerulus plus the capsule function as filtration unit

d. Renal Tubules – Increase in complexity in higher vertebrates

1. Function – Secretion directly from blood and Reabsorption from tubules back to blood based on need.

2. ADH – Antidiuretic Hormone promotes water reabsorption from tubules

3. Aldosterone – Hormone that promotes sodium reabsorption from tubules and water passively follows

4. Countercurrent – Arrangement of kidney tubules allows for maximum efficiency

e. Peritubular capillaries

f. Common collecting tubule

g. Longitudinal kidney duct – Carries urine to cloaca in all but placental mammals

3. Pronephros – Forms from intermediate mesoderm (mesomere) very far cranially

a. Temporary pronephric tubules

b. Pronephric duct to cloaca – Persists in anamniotes, but changes name to mesonephric duct

c. Functional embryonic kidney in anamniotes

4. Mesonephros – Middle region of intermediate mesoderm

a. Mesonephric duct

b. Functional embryonic kidney in amniotes

c. Adult kidney of fish & amphibians

d. Vasa efferentia – Carries sperm from testicle to mesonephric duct

e. Spermatic duct = Vas deferens = Mesonephric duct in males

5. Metanephros – Caudal-most intermediate mesoderm

a. Adult amniote kidney

b. Cortex – Outer region of kidney

c. Medulla – Inner region of kidney

1. Pyramids

2. Papilla

d. Pelvis – Slit like funnel collecting urine from kidney medulla

e. Ureter[= metanephric duct]

B. Urinary Bladder

1. Cyclostomes and Elasmobranchs – No urinary bladder


a. Mesonephric ducts form bladder

3. Dipnoans – Bladder is cloacal derivative


a. Cloaca derivative & urinary bladder empties into cloaca in all – Except placental mammals

b. Allantois – This embryonic structure forms urinary bladder in placental mammals

1. Urachus – Remnant of allantois

2. Umbilical ligament – Fate of urachus

c. Urinary bladder empties into the urethra.

5. Function – Water reservoir in all except placental mammals. Water can be reabsorbed under ADH release. In placental mammals, urinary bladder serves as a holding tank for urine and for pheromones/marking territory.