Biology – Homeostasis in mammals | e-Consult
Homeostasis in mammals (1 questions)
Both glomerular filtration and selective reabsorption are essential processes in urine formation, working together to ensure the body maintains homeostasis. However, they differ significantly in their mechanisms and outcomes.
Glomerular Filtration:
- Process: The movement of water and solutes from the glomerular capillaries into Bowman's capsule.
- Mechanism: Driven by hydrostatic pressure in the glomerular capillaries and opposing pressures in the Bowman's capsule and glomerular capillaries. Relies on the glomerular filtration barrier.
- Key Features: Non-selective; allows passage of most small solutes. Results in the formation of glomerular filtrate, which is plasma without large proteins and blood cells.
- Homeostatic Role: Determines the volume and composition of the fluid that will be processed by the kidneys.
- Factors Influencing Rate: Glomerular capillary hydrostatic pressure, capsular hydrostatic pressure, glomerular capillary oncotic pressure, and glomerular membrane area. Higher pressure and larger area increase filtration rate.
Selective Reabsorption:
- Process: The movement of substances from the glomerular filtrate back into the peritubular capillaries.
- Mechanism: Involves active transport, facilitated diffusion, and osmosis. Requires energy (ATP) for active transport.
- Key Features: Highly selective; reabsorbs essential substances and water. Restores valuable substances to the bloodstream.
- Homeostatic Role: Prevents the loss of essential substances and maintains blood volume, blood pressure, and electrolyte balance.
- Factors Influencing Rate: The concentration gradients of solutes in the filtrate, the efficiency of transport proteins, and the overall metabolic needs of the body.
Comparison: Both processes are crucial for maintaining homeostasis, but filtration is a passive process that determines the initial composition of the urine, while reabsorption is an active process that modifies the composition of the filtrate. Filtration is non-selective, while reabsorption is highly selective. The rate of filtration is primarily determined by hydrostatic and osmotic pressures, while the rate of reabsorption is influenced by concentration gradients and transport protein efficiency.