Kidneys and Homeostatic Flashcards
(34 cards)
What is homeostasis?
Mechanisms that maintain a relative constant environment for cellular reactions
What do fish excrete and why?
Ammonia as they live in water so no water loss and ammonia is soluble
What do birds and reptiles excrete and why?
Uric acid as it minimises water loss (as its a precipitate) and is insoluble
What do most mammals excrete and why?
Urea as its less toxic then ammonia and sacrifices less water
How is urea made in animals?
Amino acids are deaminated in the liver, to make ammonia and pyruvic acid for respiration
How can homeostasis be maintained?
Negative feedback
What is the role of positive feedback?
To enhance the size of the stimulus
Draw and label a diagram of a kidney
Cortex, fibrous capsule, medulla, renal pelvis, renal artery and vein, nephron
Draw and label a diagram of a nephron
Afferent artiole, glomerulus, Bowman’s capsule, efferent artiole, proximal convoluted tubule, descending limb of Loop of Henle, ascending limb of Loop of Henle, Loop of Henle, distal convoluted tubule vasa recta, collecting duct
How to recognise PCT from DCT in an electron microscope
PCT has microvilli, DCT doesn’t
How to recognise glomerulus and Bowman’s capsule in an electron microscope of the cortex?
Bowman’s capsule around glomerulus, glomerulus has lots of small “swiggles” inside it
How to recognise Loop of Henle from Collecting duct in an electron microscope of the medulla?
Collecting Duct has sectors in it and thicker walls then loop of Henle
What is ultrafiltration and what process is it similar to?
Filtration of water at high press.
Similar to formation of tissue fluid but “glomerular filtrate” is made
How is the press in the capillaries in the glomerulus high?
From high hydrostatic press of renal artery
The diff in diameter of afferent and efferent arteriole
Where are the molecules transport from and to in ultrafilteration?
From the capillaries of the glomerulus into the Bowman’s Capsule
Name and describe the layers of the capillaries?
- Endothelial cells with fenestrations.
- Basement membrane made with glycoproteins and collagen with a molecular sieve
- Podocytes with pedicels that have between filtration slits between them
What types of molecules can go through the sieve of the basement membrane in the capillaries of the glomerulus as glomerulus filtrate?
Anyone that are smaller then 68000RMM
-Glucose
-Na
-H2O
-Urea
What types of molecules can’t go through the sieve of the basement membrane in the capillaries of the glomerulus as glomerulus filtrate?
Plasma proteins, blood cells, platelets as they are too big to go through the sieve of the basement membrane
What is the glomerulus filtration rate?
Rate at which fluid moves out of capp. in glomerulus to the lumen of Bowman’s Capsule
Where does selective reabsorption happen?
In the PCT
Describe the adaptations of the proximal convoluted tubule (PCT) to increase the efficiency of selective reabsorption.
-Thin walls, short diff pathway
-Microvilli, SA
-Lots of mitochondria
-Permeable to O2, glucose etc
-Close to blood supply to carry away reabsorbed food
-Tight conjunctions to stop molecules going back to filtrate
Describe the process of selective reabsorption with Na and glucose (same with any other molecules)
- Na+/K+ pumps out Na+, so low conc. of Na+ in epithelial cell
- Co-transport of 1 Na+ and 1 glucose by facilitated diffusion and secondary active transport (glucose against conc.)
- Na+ diffuses into filtrate by Na+ pump and glucose by facilitated diffusion
- Both diffuse into blood of capillary in the filtrate
Where is most of the water reabsorbed into the blood?
In the PCT via osmosis
What is the water pot. of the PCT compared to the blood plasma at the end of selective reabsorption?
Isotonic
