Chapter 15 - Kidney/Liver/Excretion Flashcards
What is the toxic substance produced in deamination.
Ammonia, NH3
The liver has considerable powers of regeneration, even if a high proportion of its cells are damaged.
Name the liver cells that can lead to this regeneration and the type of cell division that they carry out.
Hepatocytes
Mitosis
Explain how the longer loop of Henle is able to assist the desert kangaroo rat in preventing excessive water loss.
The loop of Henle is longer so more Na+ and Cl- can move out from ascending limb to medulla.
This creates a water potential gradient
Water reabsorbs from collecting duct so less water loss.
Describe how the endocrine and nervous systems work together to increase water reabsorption from the collecting duct.
Hypothalamus causes release of ADH from pituitary and aldosterone is also released from adrenal cortex.
In the endocrine system, ADH is released from the pituitary gland and binds to the receptors on the cell membrane of the DCT and collecting duct. This causes a cAMP messenger to be released and vesicles which contain aquaporins move to the cell surface membrane and increase the permeability.
In the nervous system, there are osmoreceptors in the hypothalamus which detect low water potential in the blood. ADH is produced in the hypothalamus. When water potential rises, less ADH is produced and less reabsorption and more urine is produced. When water potential lowers, more ADH is produced and more reabsorption so less urine is produced. This all works on a negative feedback loop.
State one function of the distal convoluted tubule.
Regulates the water needs of the body
Reabsorption of Na+ and Cl-
When old red blood cells are broken down, each haem group is converted to a molecule called bilirubin. Bilirubin passes through the digestive system. Bilirubin gives faeces their characteristic colour.
Explain why bilirubin production and processing is an example of excretion.
Bilirubin is a metabolic waste product as it is produced from haem during RBC breakdown and then removed from the body.
A person’s glomerular filtration rate (GFR) provides an indication of the health of their kidneys. The GFR is a measure of the volume of blood that can be filtered by the kidneys every minute.
GFR can be estimated by monitoring the blood concentration of creatinine, which is a breakdown product of creatine phosphate in muscles.
Suggest two characteristics of a patient that must be taken into account when using this GFR measurement to diagnose kidney damage.
Explain why each characteristic must be considered.
Gender - men and women have different muscle mass
Age - kidney function declines with age
The process of ultrafiltration in the kidney shares similarities with the formation of tissue fluid.
Describe the similarities and differences between ultrafiltration and the formation of tissue fluid. (6)
The similarities between ultrafiltration and formation of tissue fluid is that both process occur in capillaries and small molecules are able to diffuse out of the blood whilst the larger molecules (proteins) remain in the blood. Both are under high hydrostatic pressure and are greater than oncotic pressure so that molecules such as water can be forced out the capillary. Both also have basement membranes.
The differences are that filtrate enters the bowman capsule and the PCT in the kidney but tissue fluid enter intercellular space.
In the kidney, the waste product formed is urine whilst in the kidney it is the lymph.
How might the peritoneum differ in its function from the artificial membrane in a dialysis machine used in haemodialysis?
It can use active transport
Suggest why patients receiving peritoneal dialysis usually need to have the peritoneal dialysis fluid replaced four times a day, but those receiving haemodialysis only need treatment three times a week.
peritoneal dialysis can remove less waste
haemodialysis uses counter-current floW
H - can maintain concentration gradient whilst peritoneal reduces the concentration gradient
Explain why some foods (crisps, sweets, chocolate, bread) affect urine production.
salted crisp and sweets reduce water potential as high sugar content so osmoreceptors detect this and increase release of ADH causing more water to be reabsorbed. Chocolate, bread increase water potential of blood so less ADH released.
Explain why peritoneal dialysis can use active transport and diffusion while haemodialysis relies on diffusion alone.
Peritoneal wall is made up of living cells, so contains mitochondria and produces ATP for active transport.
Haemodialysis is only a membrane and can only have diffusion
Explain why podocytes are usually unable to undergo mitosis.
They have already differentiated so cannot divide
The shape is too irregular so cannot divide
Spindle fibres cannot be formed
Studies show that after damage by infection or injury, it is possible for nephron tissues to be regenerated. Adult stem cells are involved in this process.
What features of adult stem cells make them suitable for regeneration of tissues in the kidney?
Adult stem cells are multipoint and can divide to any cell type within the kidney.
compare the processes occurring in the proximal and distal convoluted tubules.
Both use active transport, and selective reabsorption
Difference is that DCT cotransport ions only whilst PCT involves ions and glucose molecules.
