Module 5: Structure and Function of the Kidney Flashcards
The kidneys have 2 main homeostatic roles , what are they involved in?
excretion and osmoregulation
Name the vessel that supplies the kidneys with blood and name the structure that these vessels branch from
the renal artery , they branch off from the abdominal aorta
Name the vessel that removes blood that has circulated through the kidneys and state where these vessels lead to
the renal vein
it drains blood into the inferior vena cava
Name the tiny structures that make up the kidneys (we have millions of these)
These structures act as what …
nephrons
filtering units
Name the sterile liquid produced by the kidney tubules
This liquid passes out the kidneys down tubes called …
urine
ureters
Where do the ureters lead to(this is where urine is stored)?
the bladder
What happens when the bladder becomes full?
the sphincter at the exit of the bladder opens and urine passes out the body through the urethra
What are the 3 main areas within the kidneys structure?
the cortex , medulla and pelvis
Where is the cortex located and what happens here in summary?
the outer layer of the kidney
this is where filtering of the blood takes place
Where is the medulla located and what structures are present here?
the middle section of the kidney
contains the tubules of the nephrons that form the renal pyramids and the collecting ducts
Where is the renal pelvis located?
What happen here in summary?
its the central chamber of the kidney
this is where urine collects before passing down the ureter
What happens in the nephrons?
this is where blood is filtered
When blood is filtered in the nephrons , what substances are removed and therefore do not return to the blood?
Give 4 examples of substances that are selectively reabsorbed back into the blood
nitrogenous wastes
water , glucose , salts , amino acids etc
What are the 5 main structures of nephrons?
The Bowman’s capsule
Proximal Convoluted Tubule(PCT)
Loop of Henle
Distal Convoluted Tubule(DCT)
Collecting Duct
Describe the structure of the Bowmans capsule
2 points
-a cup shaped structure that surrounds a network of capillaries known as the glomerelus
-contains specialised cells called podocytes in its inner layer
What is the purpose of the podocytes in the Bowmans capsule?
to act as an additional filter to ensure any cells , large plasma proteins or platelets that have passed through epithelial cells do not enter the tubules
Describe the structure of the PCT
3 points
-the first coiled region after the Bowmans capsule
-the epithelial cells within its wall have microvilli to increase the surface area available for selective reabsorption
-the epithelial cells also contain many mitochondria to provide ATP for active transport of sodium ions
What process occurs in the PCT?
Briefly describe this
selective reabsorption
this is where all the glucose , amino acids and hormones in the filtrate are reabsorbed back into the blood
Describe the structure of the loop of Henle
3 points
-made up of the descending limb and the ascending limb
-its a long loop of tubule that creates a region with a high solute concentration in the medulla
-different areas have different permeabilities to water
Once substances have been removed from the nephron by selective reabsorption , where do they go?
How is a steep concentration gradient maintained here?
they diffuse into the extensive capillary network that surrounds the tubules
by the constant flow of blood through capillaries
Once filtrate reaches the loop of Henle , its … with the tissue fluid surrounding the tubule and the blood
isotonic
Describe how the loop of Henle acts as a counter current multiplier
2 points
-by using energy to produce concentration gradients that result in movement of substances such as water from one cell to another
-cells also use ATP to actively transport ions , creating a diffusion gradient in the medulla
Make 3 points about the descending limb of the loop of Henle
(include what substance moves out filtrate here , the permeability of this area , and refer to chloride and sodium ions)
-the region where water moves out filtrate down a concentration gradient
-upper part is impermeable to water but lower part is permeable and runs into the medulla
-concentration of sodium and chloride ions in tissue fluid of medulla increases moving through the cortex to pyramids as a result of activity of the ascending limb
Filtrate entering the descending limb is .. to blood
What two molecules is the descending limb not permeable to?
Therefore none of what process occurs , what does this result in?
isotonic
sodium and chloride ions , so no active transport occurs
this results in fluid reaching the hairpin of the loop being very hypertonic to blood in capillaries
Make 3 points about the ascending limb of the loop of Henle
-the first section is very permeable to sodium and chloride ions so they move out of the fluid by diffusion down a concentration gradient
-in the second section sodium and chloride ions are actively pumped into medulla tissue fluid against a concentration gradient
-its impermeable to water , meaning fluid left in the ascending limb becomes increasingly dilute while tissue fluid of medulla develops the very high ion concentration
Why is it important that the tissue fluid of the renal medulla has a very high ion concentration?
Fluid that reaches the top of the ascending limb is … to blood
its essential for the kidney to produce urine that is more concentrated than the blood
hypotonic
Make 3 points about the structure and function of the DCT
-where water needs of the body and pH of blood is balanced
-permeability of the walls are controlled by levels of ADH
-cells lining the DCT have many mitochondria so are adapted to carry out active transport
What happens if the body lacks salt?
(in terms of the DCT)
-sodium ions will be actively pumped out the DCT with chloride ions following
-water can also leave the DCT if the walls of the tubule are permeable in response to ADH
Make 2 points about the collecting duct
-passes down through the tissue fluid of the renal medulla
-permeability of collecting duct to water also controlled by ADH , which determines how much or little water is reabsorbed
