Excretion Flashcards
What do the kidneys excrete?
Nitrogenous wastes; Ammonia, urea, uric acid, creatinine
——–O——-
H2N -C- NH2
Urea; Water soluble, excreted in urine
What is urea composed of?
3% Urea, 2% Salts, 95% Water
What gives urine its yellow colour?
urochrome from breakdown of heme
Renal vein
Carries blood from kidenys back to heart
Renal artery
Carries blood to kidenys
Kidenys three major divisions?
Cortex (outer layer), Medulla (middle layer), and Pelvis (inner cavity)
Bowmans capsule
Where wastes are forced out of the blood and into the nephron and enters the glomerulus
Afferent artiriole vs Efferent artiriole
Carries blood to glomerulus
Carries blood from glomerulus
Urine formation (3)
- Pressure filtration
- Selective re-absorbtion
3.Tubular excretion
What can and cannot pass through the glomerulus?
Can: (Small molecules)
H2O, nitrogenous wastes, nutrients, ions (salts)
Cannot: (Large molecules)
Blood cells, platelets, protein
What is filtrate?
The small molecules that were forced into the Bowmans capsule.
Function of the Juxtoglomelar apparatis?
To achieve high pressures for filtration. If needed will release Renin hormone to increase blood pressure
What gets reabsorbed after pressure filtration?
H2O, nutrients, salts (Na+, Cl-)
What does not get reabsorbed?
Some H2O, wastes, excess salts do not get reabsorbed and continue through the loop of Henle
What is active transport?
Requires ATP and a carrier molecule (glucose, Na+)
What is passive transport?
e.g Cl-, H2O
What is the primary role of the loop of Henle?
Reabsorption of H2O
Why is the urine hypertonic to plasma?
Na+ Cl- is also passively and actively reabsorbed concentrating the urine
What is tubular excretion?
Process where other non filterable wastes can be added to tubular fluid and excreted in urine
Where and what is excreted in tubular excretion?
An active process, occurs in the DCT (distal convuluted tubule)
Substances include: Penicillan, H+, NH3
Explain the hormone renin.
Renin is released by the Juxtoglomelur apparatis to achieve high pressures for filtration. It increases blood pressure. People with kidney disease have high blood pressure from the constant release of renin.
What is the function of ADH?
Promotes reabsorption if low H2O content of blood. Decreases the urine volume by diluting it to increase blood volume
What does aldesterone do?
Released by the adrenal cortex, makes the kidneys retain more Na+ and excrete K+
Hypertension
Na+ in the blood is too high
Hypotension
Na+ in the blood is too low, results in not enough H2O reabsorbed
What if the blood is more acidic?
More H+ and ammonia is excreted, more sodium bicarbonate is reabsorbed which neutralizes acid
What if blood is more alkaline?
Less H+ excreted, less Na+ and HCO3- reabsorbed
