Renal Tubules Flashcards
Function of renal corpuscle
Regulate filtrate, filtrate making machine
What within the filtrate should be completely reabsorbed?
**Should never be found in the urine
- Glucose, amino acids, bicarb
What within the filtrate should be regulated?
**Partially reabsorbed
- Water, Na+, K+, Cl-
What within the filtrate should be excreted as urine?
- Urea, creatinine, drugs
Descending limb of LOH: permeability
Water permeable: releases water
Ascending limb of LOH: permeability
Impermeable to water: releases ions but not water
Collecting ducts: permeability
Sometimes permeable to water (in the presence of ADH)
Afferent arterioles: nephrons
Arcuate arteries (run along border of medulla + cortex) and give rise to radial arteries
Radial arteries give rise to afferent arterioles which go to the nephrons
Efferent arterioles: renal tubules
Spread over tubules to reabsorb the good stuff
Makes a capillary bed across DCT/PCT and LOH
Then goes into venous drainage
Vasta recta: tiny capillary beds that collects good stuff & gets rid of bad stuff (goes into arcuate vein)
Ways to reabsorb solutes & water (x2)
Active transport: requires energy
Passive transport: concentration gradient (note: water always follows sodium)
Where does most of the water reabsorption occur (obligatory)?
In the PCT and descending LOH (they’re water permeable)
What is facultative water reabsorption and where does it occur?
Water reabsorption that increases/decreases depending on the amount required by the body
Controlled by ADH –> makes collecting ducts water permeable
During dehydration –> lots of ADH is put out
What is the most active area for reabsorption?
PCT!
100% of solutes reabsorbed
65% of water reabsorbed by the end of the PCT
Types of active transport (x2)
Primary active transport: uses ATP
Secondary active transport: uses energy of movement of ions down their conc. gradient for transport other solutes
Types of active transport (x2)
Primary active transport: uses ATP
Secondary active transport: uses energy of movement of ions down their conc. gradient for transport other solutes
Types of secondary active transport
Symporter: when the protein moves the ion & solute in the same direction
Antiporter: when the protein moves the ion & solute in opposite directions
Maximum rate: transport proteins
Transport proteins can only bind + move solutes at a fixed rate
Saturation of this transport mechanism limits reabsorption of substances like glucose
What does glycosuria mean?
Tm of active transporters has been reached (Na+-glucose symporter)
How is the glucose symporter coupled to the Na+/K+ pump?
2 sodiums pull in 1 glucose
Sodium is moved into interstitial fluid via Na+/K+ pump
Glucose leaves cell –> interstitial fluid via glucose facilitated diffusion transporter
What happens when the kidneys fail?
Salt & waste products (urea) build up & blood pH goes down
Massive edema results from salt retention
Acidemia results from the inability to excrete acids (H+)
Potassium levels get too high –> hyperkalemia + cardiac arrest
(K+ destabilizes cardiac rhythm)
Treatments for kidney failure
Kidney dialysis: takes nasty stuff of blood out & puts it back in body
Peritoneal dialysis: port goes into peritoneal cavity & flushes in lots of fluid, salts & waste go there and then everything gets sucked out
Kidney transplant
What does the detrusor muscle do?
Contracts to push urine out
What is the trigone?
Area in-between 2 urethral openings, part of the bladder that doesn’t contract
Deep transverse perineus
Has fibers that run up the urethra
Striated –> voluntary control
What do the levator muscles do?
Lift up & down (faces & urinary content), keeps sphincter closed
Micturition reflex
Stretch receptors in bladder get stimulated (sends messages to sacral portion of spinal cord, parasym)
Triggers an autonomic reflex which sends parasympathetic motor signals to the detrusor muscle (smooth muscle, not voluntary) and the internal urethral sphincter (in males, SM) relaxes
There is still the external sphincter –> conscious control, need to relax to pee
Somatic nerves and micturition reflex
The somatic nerves holding the external sphincter closed are inhibited by the micturition reflex - pressure buildup is usually not enough to open the external sphincter
