Kidney Flashcards
What is deamination?
Surplus amino acids that are not used for protein synthesis cannot be stored in the body and are deaminated in the liver= the removal of the amino group to leave ammonia and pyruvic acid. The ammonia is converted to urea in the liver. The rest of the amino acid can be used in respiration as a source of energy or converted into fat and stored.
What is nitrogenous waste?
Waste products containing nitrogen, primarily formed from the breakdown of proteins and nucleic acids. The type an organism produces depends on the environment it inhabit. Some animals excrete their ammonia directly, others first convert it to less toxic wastes, such as urea or uric acid.
What is ammonia and what happens to it in different organisms?
Ammonia molecules are small, very toxic and soluble. Most aquatic animals excrete ammonia. In soft-bodied invertebrates, ammonia diffuses across the whole body surface into the surrounding water. In freshwater fish, most of the ammonia is lost as ammonium ions across the epithelium of the gills, with kidneys playing only a minor role in excretion of nitrogenous waste.
What is uric acid?
Thousands of times less soluble in water than either ammonia or urea and is excreted as a precipitate after nearly all the water has been reabsorbed from the urine. Land snails, insects, birds, and some reptiles excrete uric acid as the major nitrogenous waste. In birds and reptiles, the paste-like urine is eliminated along with faeces from the intestine.
What do animals do with Urea?
-Most terrestrial animals convert the ammonia to urea and excrete this.
-A terrestrial animal would have produced lots of urine to get rid of ammonia, because a compound so toxic could only be transported and excreted in a very dilute solution.
-Urea can be transported in a much more concentrated form because it is about 100,000 times less toxic than ammonia.
-Urea excretion enables the animal to sacrifice less water to discard it’s nitrogenous waste, an important adaptation for living on land.
What are the different types of nitrogenous waste?
Urea, uric acid, ammonia, creatinine.
Uric acid and urea represent two different adaptations that enable terrestrial animals to excrete nitrogenous waste with a minimal loss of water.
What is the structure of kidneys?
Each kidney contains approximately 1 million tiny tubules called nephrons. A nephron ( individual blood filtering unit) begins with a cup shaped structure called a Bowman’s capsule followed by the proximal concluded tubule (PCT) then loop of Henle which leads into the distal convoluted tubule (DCT) and finally joins to a collecting duct. Blood flowing through an afferent arterials which has branched from the renal artery forms a capillary network called the glomerulus within the bowman’s capsule.
What is homeostasis?
The maintenance of a constant internal environment by an organism.
It helps maintain optimal conditions for cellular reactions, and gives organisms independence from the external environment whilst still existing in it.
Describe homeostasis and kidney function:
- Stimulus produces change in variable.
- Change detected by receptors.
- Input: info sent along afferent pathway to control centre.
- Output: info sent along efferent pathway to effector.
- Response of effector feeds back to influence magnitude of stimulus and return variable to homeostasis.
What is homeostasis maintained by?
Maintained through a combination of nervous and hormonal mechanisms, often by negative feedback: whenever a factor moves away from the ideal/norm, a set of processes moves it back towards normal again.
What are hormones?
Molecules that are released by endocrine glands directly into the blood that travel to a target organ to produce an effect.
When is an endocrine gland?
A duct-less gland that secretes hormones directly into the blood.
What are the functions of the kidney?
-Filter the blood to remove nitrogenous metabolic waste to produce urine.
-Homeostatic function of osmoregulation (control of water and solute composition of body fluid (blood)).
What is an exocrine gland?
Secretes substances into a duct (=tube lined with epithelial cells and conveying secretion).
What is the nephron function?
-Blood in the vasa recta (a capillary network surrounding the loop of Henle) delivers nutrients and oxygen to the cells of nephrons.
-Carries waste and mineral ions reabsorbed from the kidneys.
Label human urinary system:
Answer in booklet.
Label the internal structure of a kidney:
Answer in booklet.
Label a nephron:
Answer in booklet.
How do you know if it’s a collecting duct on a microscope slide?
You can see the individual membranes.
How do you know if it’s a PCT on a microscope slide?
Have brush border.
How do you know if it’s a DCT on a microscope slide?
Has no brush border.
Why is the blood pressure in the capillaries high?
The efferent arteriole has a narrower lumen than the afferent arteriole so will cause an increase in pressure.
What is Ultrafiltration?
Filtering blood at high pressure, to remove urea. It happens in the glomerulus/Bowman’s capsule.
What materials pass into the Bowman’s capsule?
All small molecules, water, salts, amino acids, urea, glucose.
What doesn’t pass out of the blood and into the nephron?
RBCs, WBCs, platelets, large plasma proteins.
What’s the function of Podocytes?
Withstand pressure. Stops bursting.
Describe the process of selective reabsorption:
- Sodium ions are actively transported out of the cells lining the PCT at the basal membrane and potassium ions are actively transported into the cell using a sodium-potassium pump. The protein pumps are embedded in the basal membrane and require ATP. It is the sodium ion conc gradient that results in the movement of glucose in co-transport, not ATP directly=secondary active transport.
- There is now a higher conc of Na+ in the filtrate (lumen of PCT) than inside the cell. 2Na+ are co-transported into the cell with one molecule of glucose by facilitated diffusion. The rate of co-transport is dependent on the sodium ion gradient.
- Na+ and glucose diffuse through the cell down their conc gradients towards the basal membrane. Glucose is transported out of the cell by facilitated diffusion. Na+ are pumped out of the cell by the sodium potassium pump.
- Glucose diffuses from an area of high conc outside the capillary to an area of low conc in the capillary. Transport into the capillary occurs by facilitated diffusion. (As the heart pumps the blood, it carries the glucose away from the kidney and maintains the conc gradient).
This absorbs 85-90% of water in the nephron. The remaining 10-15% is regulated in the loop of Henle and collecting duct.
What is selective reabsorption?
The re-absorption of all the glucose and amino acids and most of the water and ions from the filtrate back into the blood.
What does ‘renal threshold’ (for glucose mean)?
Amount of (glucose) that can be absorbed in the time it takes to reach end of PCT.
Explain what happens when there is a decrease in water potential in the blood:
- Decrease in water potential of the blood (stimulus).
- Osmoreceptors in hypothalamus detect the decrease in water potential of blood (detector/ receptor).
- Posterior lobe of pituitary gland-increases ADH secretion (coordinator).
- Collecting ducts and DCT of the kidney nephron become more permeable to water (effector).
- More water moves into the medulla by osmosis and is quickly removed by the vasa recta – a small volume of concentrated (hypertonic) urine is produced (response).
Explain what happens when there is a increase in water potential in the blood:
- Increase in water potential of the blood (stimulus).
- Osmoreceptors in hypothalamus detect the increase in water potential of blood (detector/ receptor).
- Posterior lobe of pituitary gland-decreases ADH secretion (coordinator).
- Collecting ducts and DCT of the kidney nephron become less permeable to water (effector).
- Less water moves into the medulla by osmosis and is quickly removed by the vasa recta – a large volume of dilute (hypotonic) urine is produced (response).
What is osmoregulation?
Homeostatic control of water and solute composition of the blood; under hormonal control.
Happens in the collecting duct and DCT.
Describe Osmoregulation:
The permeability of the walls of the DCT and the collecting duct can be affected by ADH. This allows mammals to control the volume of water reabsorbed into the blood and so maintain a constant water potential of the blood.
Certain molecules are actively pumped from the blood capillaries surrounding the DCT into the filtrate for removal in the urine (protons, excretory drug breakdown products, ions).
The filtrate inside the collecting duct and DCT will have a higher water potential than the surrounding TF of the medulla. Water will therefore move by osmosis out of these tubules and into the medulla, where it will re enter the capillaries.
What happens if the cells shrink during osmoregulation?
Will stimulate neurosecretory cells in the hypothalamus to release ADH. The ADH can be stored in the posterior pituitary gland.
What happens if the cells swell in osmoregulation?
Will stimulate neurosecretory cells in the hypothalamus to release less ADH.
The drier the habitat the… what, the loop of Henle?
Longer.
When are the aquaporins always open and when do they change (in osmoregulation)?
Always open on ‘blood side’.
Change based on ADH on ‘lumen side’.
What happens in the hair-pin counter current multiplier (loop of Henle)?
- Na+ and Cl- ions pumped out of ascending limb to the medulla, causing a decrease of water potential of the tissue fluid.
- H2O moves out of descending limb by osmosis (the water is absorbed by the vasa recta).
- The fluid in the descending limb becomes more concentrated.
- The filtrate and the tissue fluid of the medulla have the highest concentration of Na+ ions at the apex of the loop of Henle.
H2O returns to vasa recta due to low water potential of blood due to blood proteins.
What does the hair-pin counter current multiplier (loop of Henle) do?
Creates an environment with a very low WP in the tissue fluid in the medulla. Water diffuses by osmosis from the filtrate (from specific parts of the nephron) into the tissue fluid and then diffuses into blood plasma. Enables mammals to conserve water. Enables mammals to maintain the solute conc of the blood (osmoregulation). Actively concentrates salts in the tissue fluid of the medulla. Water reabsorbed from filtrate into blood to produce concentrated urine. The ascending limb is relatively impermeable to water but permeable to Na+ and Cl-, while the descending limb is permeable to wa6er but impermeable to Na+ and Cl-.
Why is it that the longer the loop of Henle, the more salty?
More water has been conserved. Increased saltiness in TF/Interstitial fluid further down descending limb you go.
What is a solution?
Solute+solvent.
How do you make a solution more concentrated?
Add solute (Na+/Cl-)
Remove solvent (water)
How do you make a solution more dilute?
Remove solutes (Na+/Cl-)
Add solvent (water).
What are afferent arterioles?
Blood vessels that branch from the renal artery and branch into glomeruli to supply blood to the nephrons of the kidney.
What is Antidiuretic hormone (ADH)?
A hormone produced by the hypothalamus that passes to the posterior pituitary gland from where it is secreted. ADH increases water reabsorption in the kidneys.
What is a basement membrane?
A thin, fibrous, extracellular matrix of tissue that separate the glomerular endothelial cells and podocyte cells of the Bowman’s capsule.
What is the Bowman’s capsule?
The cup shaped portion of the start of the nephron that encloses the glomerulus.
What is the cortex?
Outer region of the kidney that contains the Bowman’s capsules and convoluted tubules.
What is the Distal convoluted tubule (DCT)?
Tubule that forms from the loop of Henle and feeds into the collecting duct. Selective reabsorption find tunes ion and water levels.
What is efferent arteriole?
Blood vessels that form from the convergence of the capillaries of the glomeruli before forming the network of capillaries responsible for reabsorption of materials from the nephron.
What is the glomerular filtrate?
Solution formed from the ultrafiltration of the blood in Bowman’s capsule.
What is the glomerulus?
Bundle of capillaries located in a Bowman’s capsule in the kidney. Site of ultrafiltration of the blood.
What is the hypothalamus?
Region of the brain adjoining the pituitary gland that acts as the control centre for the autonomic nervous system and regulated body temperature and fluid balance.
What is the loop of Henle?
The portion of the nephron that forms a hairpin loop that extends into the medulla of the kidney. It has a role in the reabsorption of water.
What is the medulla?
Central region of the kidney that contains the loops of Henle.
What is a nephron?
Basic functional unit of the mammalian kidney responsible for the formation of urine.
What is the pituitary gland?
Gland of the endocrine (hormone) system situated at the base of the brain. It has 2 parts, anterior and posterior.
What is the proximal convoluted tubule (PCT)?
Tubule that forms from the Bowman’s capsule and feeds into the loop of Henle. Glucose is selectively reabsorbed.
What is selective reabsorption?
The ability of a cell to preferentially absorb some substances over others from the glomerular filtrate back into the blood.
What is ultrafiltration?
Filtration assisted by blood pressure, e.g. in the form of tissue fluid and glomerular filtrate.
What is Urea?
Molecule formed in mammals from the breakdown of excess amino acids. Slightly toxic. Removed from the body in urine.
