Kidneys and Stuff Flashcards
Define Excretion
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)
Define Osmoregulation
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)
Functions of The Kidneys
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
Waste Products of Protein
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).
Why do Fish Produce Ammonia?
Fish live in water so have an unlimited supply of water to dilute ammonia and it does not require much energy to make
Disadvantages of Ammonia as a Waste Product
VERY toxic (must be removed from the body quickly and diluted with LARGE amounts of water)
Mammals, amphibians, and sharks produce urea because…
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
Disadvantages of Urea
Requires some water for dilution and requires more energy to produce than ammonia
Why do Birds, many reptiles, and insects produce uric acid?
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
Disadvantages of Uric Acid
Requires A LOT of energy to produce
What do insects have instead of blood
hemolymph
Function of Malphigian Tubes in Insects
Malpighian tubules remove wastes from the hemolymph, and they CONNECT to the digestive system. Malpighian tubules branch off the intestinal tract in insects.
Structure of Malphigian Tubes
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.
Components of a Nephron
- 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)
What is a Nephron?
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.
Adaptations of the Glomerulus and how it aids its function
- 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)
Nephron Adaptations
Basement membrane (mesh-like structure between glomerulus and Bowman’s capsule) prevents large substances (blood cells, proteins, platelets) from passing into the filtrate.
Bowman’s capsule adaptations
Single layer of fenestrated cells called podocytes with pedicels (extensions that wrap blood vessels of glomerulus)
What [the fuck] is Ultrafiltration
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).
Step 1 of Ultrafiltration
Blood (from the renal artery) enters the capsule through afferent arteriole (larger than efferent (draining) arteriole –creating extremely high pressure inside the capsule)
Step 2 of Ultrafiltration
High pressure forces water and blood contents (except large proteins, platelets and blood cells) through fenestrations (small slits/ pores) in the glomerulus.
Step 3 of Ultrafiltration
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.
Step 4 of Ultrafiltration
Filtrate passes into the proximal convoluted tubule.
Step 5 of Ultrafiltration
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
Loop of Henely
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)
Osmoregulators
Animals whose internal tissues maintain different solute concentrations than their environment (birds, mammals, humans, freshwater fish).
Osmoconformers
Animals whose internal tissues maintain the same solute concentrations as their environment (they are iso-osmotic to their surroundings).
How and where does ADH increase water reabsorption in the Kidneys?
ADH causes the dilation of aquaporins, water channels that reabsorb water within the collecting duct.
