Excretory System Flashcards
The glomerulus exits the Bowman’s capsule via which vessel?
Efferent arteriole
Characteristics of marine fish:
Saltwater fish
Hypoosmotic to their environment- less salty than the surrounding saltwater
Constantly loosing water to their environment
Constantly drink water
Rarely urinate
Urine is very concentrated to minimize water loss from extraction
Secrete accumulated salts through their gills
Characteristics of freshwater fish:
Hyperosmotic compared to their environment
More salty than the surrounding freshwater
Constantly absorbing too much water (gain water from the environment)
Rarely drink water
Constantly urinate
Very dilute urine
Absorb salts through their gills
What are the functions (5) of the kidneys?
1) Regulate blood pressure
2) Maintenance of blood pH
3) Stimulate the production of RBCs via secretion of erythropoietin
4) Regulate osmolarity
5) Filter the blood and excretion
Podocytes
- cells of the Bowman’s capsule that wrap around the glomerulus to form fenestrations
- filter blood by preventing large molecules (proteins, RBCs) from entering and allowing small molecules (water, solutes, sugars, vitamins, salts) to pass through
Reabsorption
Removal of water and solutes from the filtrate back into the blood vasculature
Where does majority of reabsorption occur? what is being reabsorbed?
- In the proximal convoluted tubules
- active reabsoption (transport) of almost all glucose, amino acids, and some NaCl
- passive reabsorption (transport) of potassium ions and bicarbonate ions (water follows these ions out so the cortex is not salty)
Descending loop
- High permeability to water, low permeability to salts
- Water is reabsorbed into the blood via aquaporins
- Filtrate becomes more concentrated (less dilute) - body’s way of reabsorbing and retaining water
- solute concentration in the tube increases
- water picked up by vasa recta –> medulla stays salty
Ascending loop
- High permeability to salts, impermeable to water
- Solutes are reabsorbed out of the filtrate and are absorbed by the vasa recta
- Filtrate becomes less concentrated (more dilute) - body’s way of reabsorbing and retaining important salts
- solute concentration in the tube decreases
- makes the renal medulla salty: first passively and then actively by pumping out NaCl
Secretion
Transfer of solutions from the blood vasculature directly into the nephron tubule filtrate
The longer the nephron the (more/less) concentrated the urine will be. Why?
More, the interstitial fluid surrounding the nephron becomes more concentrated with salts which is why the longer the, the more concentrated the urine will be.
Where does secretion occur?
Proximal and distal convoluted tubules secrete products taken up from the peritubular capillaries
Proximal: urea (uric acid), creatine, drugs and other waste products are secreted via active transport
Distal: protons (H+) potassium and urea are secreted via active transport
Parathyroid hormone affects on calcium levels in blood:
Increases calcium levels in the blood by stimulating reabsorption of calcium in the tubules (as well as causing bones to release calcium)
Calcitonin affects on calcium levels in blood:
Decreases calcium levels by inhibiting reabsorption of calcium from the tubules (as well as causing bones to absorb it)
Antidiuretic hormone
(ADH or vasopressin)
Released from the posterior pituitary gland upon stimulation of the hypothalamus
Prevents diuresis, production of urine, by causing aquaporins to insert into the collecting duct of the nephron which increases water reabsorption (less water foes to urine, more water back into the body)
