Endotherms 5

Question 1

What are the basic plans of excretory systems?

Answer 1

Excretory systems centre on water balance causing very different requirements on land and fresh and salt water environments

Question 2

What are the key steps in excretory systems?

Answer 2

There is a filtration execratory tubule collects filtrate from the blood with water and solutes are forced by blood pressure across the selectively permeable membranes of a cluster of capillaries and into the excretory tubule
This is followed by a selective reabsorption phase when the transport epithelium reclaims valuable substances from the filtrate and returns them to the body fluids
This is followed by secretion allowing removal of waste products and toxins from the tissue into the excretory tubule

Question 3

What are the key differences of the excretory systems of mammals and birds?

Answer 3

Mammals have retained the ancestral system of secreting urea
Highly developed kidney for producing concentrated urine
Birds secrete uric acid which has a higher cost of production but allows for more efficient water retention and is easily stored inside an egg

Question 4

What are the differences in loops of Henle in mammalian species in different environments?

Answer 4

Mammals which live in very dry conditions have longer loops allowing an increased gradient for water retention
Freshwater aquatic mammals have short loops of Henle
terrestrial mammals living in moist conditions have intermediate loops

Question 5

How do vampire bats alter their renal function?

Answer 5

These bats produce highly dilute urine immediately after a meal and then produced concentrated urine after they return to where they roost

Question 6

What are the features of the kidneys in birds?

Answer 6

In birds the kidney is divided into lobules which each have a cortex and a medulla
They contain two different types of nephron, retile-like cortical ones where there are no loops, these shut down during heavy salt loads as well as mammalian type nephrons high filtration rate and is always on

Question 7

What is the main water conservation tactic in birds?

Answer 7

The creation of uric acid which is performed by reptile-like nephrons
It is excreted as a paste, contains 2 times as much nitrogen as urea per molecule 80-90% of urinary nitrogen

Question 8

How does the concentration of uric acid occur?

Answer 8

This uric acid is encapsulated in protein coat in proximal tubule as it crystalises
It is produced through sodium, potassium and ammonium salts of uric acid
Water is reabsorbed as uric acid precipitates
Sodium and potassium also reabsorbed