15.5 Strcutre And Function Of Mammalian Kidney Flashcards
What are the 2 functions kidneys are responsible for
- as an osmoregulatory organ: they regulate the water content of the blood
- excretory organ: they excrete the toxic waste products of metabolism and substances in excess of requirements
Function of the renal artery
Carries oxygenated blood containing urea and salta to kidneys
Renal vein function
Carries deoxygenated blood away from kidneys
Ureter function
Carries urine from kidney to bladder
Bladder function
Stores urine temporality
Urethra function
Releases urine outside of body
What is the kidney surrounded by
It’s surrounded by a fairly tough outer layer known as fibrous capsule
Beneath the fibrous capsule of a kidney what is the three main area
The cortex
Medulla
Renal pelvis
The cortex
Is a dark outer layer
Where Filtering of the blood takes place
it has a very dense capillary network carrying blood from renal artery to the nephrons
The medulla
Is lighter in colour
Contains the tubules of the nephrons that form the pyramids of the kidney and the collecting ducts
The renal pelvis
Is the central chamber were urine collects before passing out down the ureter
Wat does each kidney contain and what does it do
Each kidney contains thousands of nephrons
It is the functional unit of the kidney and responsible for the formation of urine
Main structure of a nephron
- bowman’s capsule
- proximal convoluted tubule
- loop of Henle
- distal convoluted tubule
- collecting duct
Function of collecting duct
The urine passes down the collecting duct through the medulla to the pelvis
More fine tuning of the water balance takes place
Wall of this part of the tubule are also sensitive to ADH
Function of bowman’s capsule
- cup shaped structure containing glomerulus
- its a tangle of capillaries
- more blood goes into the glomerulus than leaves it due to the ultrafiltration processes that take place
Function of proximal convoluted tubule
First coiled region of the tubule after the bowman’s capsule
Found in cortex of the kidney
This is where many of the substances needed by the body ar re absorbed into the blood
Function of loop of henle
- long loop of tubule that creates a region with high solute concentration in the tissue fluid deep in kidney medulla
- the descending loop runs down from cortex through medulla to a hairpin bend at the bottom of the loop
- ascending limb travels back up through medulla to cortex
Distal convoluted tubule function
A second twisted tubule where the fine tuning of the water balance of the body takes place
Permeability of the walls to water varies in response to the levels of ADH in the blood
Further regulation of ion balance and ph of the blood also take place in this tubule
What two stages does urine formation in the kidney occur
Ultrafiltration
Selective re absorption
What is does ultrafiltration result in
- it results in the formation of tissue fluid in the capillary beds of the body and is the result of the structure of the glomerulus and the cells lining the bowman’s capsule
Describe the process of ultrafiltration
- Blood arrives at glomerulus through afferent arterioles
- Glomerulus found in bowman’s capsule of nephrons
- Blood leaves through efferent arteriole
- Hydrostatic pressure builds in the glomerulus
- Fluid passes through holes in capillary endothelium (basement membrane)
- then passes through epithelium of bowman’s capsule itself
- Fluid is now called filtrate
What molecules can and cant pass through the barriers during ultrafiltration
Can pass: water, glucose, amino acids acids, urea, ions and hormones
Can’t pass: red blood cells and plasma proteins
How does hydrostatic pressure build up in the glomerulus
The afferent arteriole has a wider lumen than the efferent arteriole
What features aid ultrafiltration
- the blood in the glomerular capillaries is separated from the lumen of the bowman’s capsule by two cell layers with a basement membrane in between them
- first cell layer is endothelium capillary:
Gaps between endothelium cells allow small molecules to pass through this layer - next layer is the basement membrane
Made up of mesh of collagen and glycoproteins so small molecules can pass through the holes in the mesh - second layer is the epithelium
Have finger like projections known as podocytes which there are gaps for small molecules to pass through
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