Kidneys and Stuff

Question 1

Define Excretion

Answer 1

The removal of the waste products of metabolic pathways (Note: egestion is NOT considered excretion because feces is not a waste product of metabolic reactions – it is simply undigested food)

Question 2

Define Osmoregulation

Answer 2

A process controlled by the kidneys in which water and blood solute concentrations, tissue, or cytoplasm are regulated (Note that the pancreas also helps to maintain solute concentrations of glucose)

Question 3

Functions of The Kidneys

Answer 3

Kidneys (in vertebrate animals) filter blood to remove metabolic waste (such as urea), toxins, and excess water.
Kidneys also reabsorb essential nutrients (water, proteins, glucose, ions) back into the bloodstream

Question 4

Waste Products of Protein

Answer 4

Breakdown of amino acids called deamination (removal of amine (NH2) group). Once removed, NH2 is incorporated into one of 3 different waste molecules: ammonia, urea, or uric acid (determined by an organism’s evolutionary habitat).

Question 5

Why do Fish Produce Ammonia?

Answer 5

Fish live in water so have an unlimited supply of water to dilute ammonia and it does not require much energy to make

Question 6

Disadvantages of Ammonia as a Waste Product

Answer 6

VERY toxic (must be removed from the body quickly and diluted with LARGE amounts of water)

Question 7

Mammals, amphibians, and sharks produce urea because…

Answer 7

Urea only toxic at higher levels; kidneys prevent excessive build up. Requires some water for dilution but not as much as ammonia (mammals have less access to water than fish); can be stored (short-term) in bladder

Question 8

Disadvantages of Urea

Answer 8

Requires some water for dilution and requires more energy to produce than ammonia

Question 9

Why do Birds, many reptiles, and insects produce uric acid?

Answer 9

Insoluble in aqueous solutions (so CAN be stored with reptile and bird embryos in developing eggs - no toxicity of ammonia); requires little to no water for dilution (excreted in concentrated form) and removal from the body, so do not need to find water as frequently

Question 10

Disadvantages of Uric Acid

Answer 10

Requires A LOT of energy to produce

Question 11

What do insects have instead of blood

Answer 11

hemolymph

Question 12

Function of Malphigian Tubes in Insects

Answer 12

Malpighian tubules remove wastes from the hemolymph, and they CONNECT to the digestive system. Malpighian tubules branch off the intestinal tract in insects.

Question 13

Structure of Malphigian Tubes

Answer 13

Malpighian tubules branch off intestinal tract in insects. At the far ends, they filter salts and ammonia (active transport), and water out of the hemolymph (these then pass INTO the gut). Salts, solutes, and water are reabsorbed back into the hemolymph in the hindgut
and ammonia (converted to uric
acid) forms a precipitate/ solid/ paste and combines with undigested food and is excreted with feces via the rectum/ anus.

Question 14

Components of a Nephron

Answer 14

• A capillary bed (glomerulus)
• A capsule surrounding the
  capillary bed (Bowman’s
  capsule)
• A tube (tubule) extending
  From Bowman’s capsule
  (made up of the proximal
  convoluted tubule, loop of
  Henle, and distal convoluted
  tubule) surrounded by a
  second capillary bed (peritubular capillary bed)

Question 15

What is a Nephron?

Answer 15

Each kidney contains
~1.25 million nephrons, tiny cellular complexes that are responsible for filtering blood, reabsorbing water, and managing waste and toxins before they are excreted.

Question 16

Adaptations of the Glomerulus and how it aids its function

Answer 16

• Wide afferent arteriole (a small branch of renal artery) and narrow efferent arteriole
• Highly branched (inside Bowman’s capsule)
• Vessels contain fenestrations (small openings/ pores)

Question 17

Nephron Adaptations

Answer 17

Basement membrane (mesh-like structure between glomerulus and Bowman’s capsule) prevents large substances (blood cells, proteins, platelets) from passing into the filtrate.

Question 18

Bowman’s capsule adaptations

Answer 18

Single layer of fenestrated cells called podocytes with pedicels (extensions that wrap blood vessels of glomerulus)

Question 19

What [the fuck] is Ultrafiltration

Answer 19

Ultrafiltration is the process by which various substances are filtered through the glomerulus and into Bowman’s capsule under extremely high pressure (forming a fluid called filtrate).

Question 20

Step 1 of Ultrafiltration

Answer 20

Blood (from the renal artery) enters the capsule through afferent arteriole (larger than efferent (draining) arteriole –creating extremely high pressure inside the capsule)

Question 21

Step 2 of Ultrafiltration

Answer 21

High pressure forces water and blood contents (except large proteins, platelets and blood cells) through fenestrations (small slits/ pores) in the glomerulus.

Question 22

Step 3 of Ultrafiltration

Answer 22

Filtered contents of blood (“glomerular filtrate” – water, glucose, salts, amino acids, urea) then pass through basement membrane (which blocks large proteins, blood cells, and platelets from passing through) and through fenestrations in podocytes (cells) lining Bowman’s capsule.

Question 23

Step 4 of Ultrafiltration

Answer 23

Filtrate passes into the proximal convoluted tubule.

Question 24

Step 5 of Ultrafiltration

Answer 24

Blood cells, proteins, platelets etc. that do NOT become part of the filtrate exit the capsule still in the blood in the efferent arteriole, which then branches into the peritubular capillary bed (vasa recta) surrounding the proximal and distal convoluted tubules and the loop of Henle

Question 25

Loop of Henely

Answer 25

Actively transports sodium into the medulla of the kidney, forcing water closer to the capillary beds so that it can be reabsorbed into the blood.
(Note: The Loop of Henely length corresponds with the environment/water accessibility of the species)

Question 26

Osmoregulators

Answer 26

Animals whose internal tissues maintain different solute concentrations than their environment (birds, mammals, humans, freshwater fish).

Question 27

Osmoconformers

Answer 27

Animals whose internal tissues maintain the same solute concentrations as their environment (they are iso-osmotic to their surroundings).

Question 28

How and where does ADH increase water reabsorption in the Kidneys?

Answer 28

ADH causes the dilation of aquaporins, water channels that reabsorb water within the collecting duct.