10.1 - Urine Formation Flashcards
List and explain the three stages of urine formation
- Filtration: removing maximum waste from blood into nephron and creating a filtrate
- Reabsorption: bringing useful molecules back into blood
- Secretion (aka tubular excretion): bringing as much harmful molecules from the blood as possible
Define filtrate
Something that can go through the membrane
Where does step 1 of filtration occur?
In glomerulus and bowman’s capsule
What is the filtration of urine known as? Why?
It is known as “pressure filtration”, this is because of the blood pushing against the capillary wall to take out small molecules (blood pressure)
What do the substances removed create? Where?
Plasma-like filtrate in the Bowman’s capsule
What is filtered into Bowman’s capsule from the blood?
- amino acids
- water
- NaCl (Na+ and Cl- ions)
- glucose
- H+ ions (protons)
- urea
- K+ (potassium ion)
- HCO3- (bicarbonate ion) -> can be essential!
What is NOT filtered into the Bowman’s capsule from the blood? Why?
- plasma protein (too big)
- blood cells (too big) -> RBC, WBC, Platelets
- some water, salts, glucose, amino acids, and H+ stay
What is the direction of filtration?
Blood to nephron (aka tubule)
What is the direction of reabsorption? What direction does arrow point?
Tubule to blood (arrow on diagram points out of tubule)
How is urea formed? Why?
2 ammonias (NH3) + 1 CO2 -> makes urea + H2O (1 H taken off each ammonia, and 1 O taken off CO2) -> this happens because urea is less toxic than ammonia
Where does formation of urea occur?
Blood
What is the direction of secretion? What is being removed?
Blood -> nephron (removing H+ from blood)
When is pH high or low?
Low = 0 - 7 (acidic)
-> more [H+] ions
High = 7- 14 (basic)
-> low [H+] ions
Why does the kidney secrete H+?
To raise pH in blood
Why does kidney reabsorb bicarbonate (HCO3-)?
It is a base, so it increases pH of blood
