Kidney and Osmoregulation - Finished Flashcards
What are the 2 main functions of the kidneys?
- Remove nitrogenous waste products (urea)
* Control the water content of the blood (osmoregulation)
Name the 3 layers of the Kidney
- Pelvis (Inner Layer)
- Medulla (Middle Layer)
- Cortex (Outer Layer)
Where is the nephron found?
The nephron is in the Cortex but the Loop of Henle travels into the Medulla
What is Ultrafiltration?
Filtration under pressure to seperate small soluble molecules from the blood plasma
Where does ultrafiltration take place?
in the Bowmans capsule
How many layers does the filtrate pass through?
- The Endothelium of the Capillary - lots of round pores known as fenstrae in it which allow most molecules through. Blood cells cannot pass through.
- The Basement Membrane - Layer of Gylcoproteins and collagen fibres - acts of a “Molecular sieve” - its is very selective as it only lets small molecules through. Large proteins cannot pass through.
- Podocyte cells inthe walls of the Bowmans capsule - There are gaps “filtration slits” between their footlike processes. These allow most molecules through.
What is the basement membrane?
The basement membrane of the capillary forms a selective barrier between the blood and the nephron and it acts as a “molecular sieve”
The basement acts as the finest filter compared to the relatively coarser filtration given by the gaps between cells in the 2 layers either side.
How is high pressure created in the glomerulus?
High blood pressure in the renal artery
A difference in diameter between afferent and efferent arterioles.
What is selective reabsorbtion?
The process by which useful substances are reabsorbed back into the blood as the filtrate passes along the nephron.
It mainly occurs in the proximal convoluted tubule
What is absorbed during selective reabsorbtion?
ALL glucose reabsorbed - by active transport
MOST salt ions reabsorbed - Sodium ions (actively transported) Chloride ions (Passively)
MOST water reabsorbed - by osmosis
What adaptations have happened in the wall of the tubules for reabsorbtion?
- Microvilli on the lumen-facing membrane increases the surface area for absorbtion.
- Infolding of the basal membrane known as basal channels increase the surface area
- Blood cappilaries - very close = short diffusion distance
What is the loop of henle’s function?
It creates the conditions within the medulla of the kidney that will allow the reabsorbtion of water.
How does the loop of henle work?
It increases solute concentration/lowers water potential which creates an osmotic gradient.
There is active transport of Na+ and Cl- out of the ascending limb. This creates a region of high solute concentration in the tissue fluid of the medulla region.
Water mves down the water potential gradient out of the desending limb and then passes into nearby cappilaries (such as the vasa recta)
What is the definition of Homeostasis?
The maintenance of a constant internal environment
What do all homeostatic mechanisms involve?
a detector
a co-ordinator
an effector
