9.5: Excretory System & Urine Formation

Excretion in Mammalian Vertebrates

simple organisms can excrete directly into the environment from their cells, water currents in external environment can carry waste away

Structures in Mammalian Vertebrates to maintain fluid balance

• Contractive vacuole

• Metanephridium

• Malpighian tubules

Excretion in Non-Mammalian Vertebrates

They conserve water by exretin nitrogenous wastes in a paste of uric acid crystal, it is removed with feces

The Kidneys

remove wastes. balance blood pH and maintain water balance

• Blood supplied via renal artery

• Clean blood exits via renal vein

Parts of the Kidney

• rena medulla

• renal cortex

• renal artery

• renal vein

• renal pelvis

• ureter

Glomerulus & Bowman’s capsule

in the cortex, filtration, water and small substances pass into nephrons

Proximal Convulted Tubule

in the cortex, reabsorption & secretion, some of ions water and rea return to interstitial fluid

Afferent arteriole

vessel that supplies blood to nephrons

Efferent arteriole

vessel that carries away filtered blood from nephrons

Peritubular Capillaries

reabsorb essential ions & minerals from filtered blood

Loop of Henle Descending

Cortex into medulla,reabsorption and sectretion at the top, additional water is returned to interstitial fluid

Loop of Henle Ascending

Medulla into Cortex, reasborption and secrtion at the top, additional ions are returned to the interstitial fluiD

Distal Convuleted Tubule

cIn cortex, reasboprotion and secretion

Colleting Duct

cortex through the medulla, secUretion

Urine is

hypoosmotic

3 features of the nepphorn that interact to conserve nutrients, water, etc

1) Arrangement of loop of henle

2) Diff in permeability of parts in nephron

3) Conc of gradient of molecules & ions in the interstitial fluid

Filtration

1) Body fluids move from blood to Bowman’s Capsule

3) Cells of bowman’s Capsule & capillaries for SPC let water and ions in high pressure drives fluid into capsule

Blood cells, platelets,and plasma are too big and stay in capillaries

Reabsorption

1) Fluid goes to bowman’s capsule then enters the proximal tubule where reasboprotion occurs and water ions are transferred back into intertidal fluid via passive and active transport

2) filtrate is now hypoosmotic to the IF and the water flows out, these nutrients enter peritubular capillaries and are absorbed into blood flow

3) in loop of Henle water and ions are reabsorbedmore water and ions leave through distal tubule and H⁺ is secreted

Secretion

removal of waste from blood and interstitial fluid

• Some substances secreted from proximal tubule

• Smal amounts of ammonia are also sereted

These substances stay in the nephron & become part of the urine which then leave through the ureter to the bladder and urethra