E2 Flashcards
What is the overall function of a nephron?
To filter blood, reabsorb essential substances, and secrete waste to form urine.
What are the four main processes of urine formation?
Glomerular filtration, tubular reabsorption, tubular secretion, water reabsorption.
What is glomerular filtration?
Movement of water and small solutes from blood plasma into the nephron.
Why are glomerular capillaries more permeable?
They have fenestrae (pores) that allow small particles to pass.
What particles pass through during filtration?
Water, ions, glucose, amino acids, ammonia, urea, uric acid.
What particles stay in the blood during filtration?
Blood cells, platelets, and proteins.
What drives glomerular filtration?
High blood pressure and pressure gradients.
Is glomerular filtration passive or active?
Passive (does not require energy).
What happens in the proximal tubule?
Active reabsorption of nutrients and positive ions; passive reabsorption of negative ions and water; secretion of H+ and ammonia.
Why do proximal tubule cells have many mitochondria?
To produce ATP for active transport.
What is the descending loop of Henle permeable to?
Water (reabsorbed by osmosis).
What is the ascending loop of Henle permeable to?
Salt (diffuses and is actively transported into the capillaries); impermeable to water.
What occurs in the distal tubule?
Active secretion of wastes (ammonia, H+, K+, medications); reabsorption of water, Na+, Cl-, and HCO3-.
What happens in the collecting duct?
Water is reabsorbed by osmosis; filtrate becomes highly concentrated.
What regulates the permeability of the distal tubule and collecting duct?
Hormones and blood plasma concentration.
What is filtrate called after it leaves the nephron?
Urine (about 1% of the original volume).
How does urine travel out of the body?
Through renal pelvis → ureters → bladder → urethra.
