Produce Urine.

Outter = cortex

Inner = medulla

Functional unit of the kidney that spans the cortex and medulla.

Nephron + collecting duct/tubules

Used for storage of urine before excretion.

Forms and outpocket of the Cloaca.

Renal Capsule (Bowman's)

Proximal Tubule

Loop of Henle

Distal Tubule

Collecting Duct

1. Glomerular Filtration in the glomerulus and renal capsule
2. Tubular Reabsoption in the tubules, loops, and collecting ducts.
3. Tubular Secretion in the distal convoluted tubule.

Glom is a capillary bed between two arterioles so there is a higher pressure than normal capillary bed.

This forces fluid out of the cap. into the renal capsule with all the components  (formed elements do not leave - RBC, WBC, platelets, plasma proteins).

What is left travels back through the circulature.

Reabsorb substances from the ultrafiltrate back into the blood since the glom filtration is very effective - the ultrafiltrate is waste and non waste - nonwaste needs to be reabsorbed.

Begins in proximal tubule. Sugars, amino acids, water reabsorbed.

Some water, nitro wastes, and excess salts, sugars are not reabsorbed.

Descending Loop - water leaves.

Ascending Loop - salt leaves (impermeable to water)

Loop goes from cortex to medulla - as you go to medulla, solute concentration outside the loop increases to create an osmotic gradient.

Loop length relative to water conservation capabilities.

Second way for substances to enter the nephron.

Active reabsorption of Na.

Substances such as creatinine, protons, etc are transferred to the distal convoluted tubule as well.

1.  Renal arteries bring blood to kidney.
2. Arteries from cap beds (glom) each bed associated with a renal capsule
3. Glom filtrate formed
4. Filtrate enters prox convoluted tubule
5. Filtrate enters Loop of Henle
6. Filtrate enters distal conv tubule for tubular secretion
7. Enters collecting duct

Reabsorb water and solutes removed from the filtrate.

Connects to the renal vein via a venule.

From the mesoderm (dorsal and post body wall).

Mesoderm expands and forms the nephric ridge which is separated into 3 locations:

1. Anterior = pronephros

2. Posterior = metaonephros

3. Middle = Mesonephros

1. Ammonotelism
2. Uricotelism
3. Ureotelism
    

Direct excretion of NH3 that requires a lot of water (NH3 is soluble in water).

Aquatic animals.

Elimination of ammonia over the gills.

Mechanism to conserve water.

Excrete uric acid (slightly soluble in water) from kidneys.
Little water required. 

In cloaca, uric acid precipitates with Na, K, ammonia salts as "sludge"

Ex: Birds/reptiles

Mechanism to conserve water because urine is concentrated.

Exrete urea.

Kidneys accumulate urea and excrete it as concentrated urine.

Ex: mammals.

Inside of fish is saltier than environment.

Hyperosmotic.

Take up water.

Well developed kidneys and large glomeruli.

High dilute urine to eliminate water.

Inside of the fish is less salty then environment.

Hypoosmotic.

Lose water - do not produce much filtrate/urine.

The goal is to mangage water flux.

Drink water.

Thick integument, need to recover water before eliminating wastes.

Filtration kidneys and concentrated urine.

DCT revoers salt from urine.

Gills pump out salt (SW) or into the body (FW).

Rectal Glands.

Salt Glands (Birds/reptiles)

Skin/Aquatic Amphibians lose salt passivelt across skin and actively take up salt across the skin.