Kidney

Question 1

Kidney’s functions:

Answer 1

1) Regulation of Water, salts & acid balance.
2) Removal of foreign chemicals & metabolic waste.
3) Gluconeogenesis
4) Production of hormones & enzymes

Question 2

Describe the functions of:
- Erythropoietin
- Renin
- Vit D

Answer 2

Erythropoietin: controls RBC production.
Renin: controls blood pressure & sodium balance.
Vit D: Uses an enzyme to activate Vitamin D (regulates Ca).

Question 3

Kidney structure:

Answer 3

Ureter leads into the renal pelvis, leading into the medulla, which is in the cortex, encased in the capsule.

Question 4

Describe: Glomerular Filtration

Answer 4

Bowman’s Capsule contains the Glomerulus, a region of blood vessels encased in endothelial cells with a large SA, surrounded by Podocytes, creating a sieve-like structure, allowing the passage of only small molecules from the blood into the kidney tubes.
Fluid filtered through glomeruli by pressure of flowing through blood vessels, meaning the GFR can be regulated by adjusting blood pressure on either side of glomerulus.

Question 5

Tubular Secretion:

Answer 5

Substances are secreted into the nephron for excretion.

Question 6

Tubular reabsorption:

Answer 6

The blood reabsorbing something which entered the nephron.

Question 7

Controlling the Glomerular Filtration Rate:

Answer 7

• Reducing pressure in the glomerulus reduces GFR:
  Constricting afferent vessels & dilating efferent vessels reduces water & salt loss through excretion.
• Increasing pressure in the glomerulus increases GFR:
  Constricting efferent vessels & dilating afferent vessels increases water & salt excretion.

Question 8

Proximal Convoluted Tubule: Tubule to Cell

Answer 8

Na+ moved from tubules into cells through two mechanisms:
* Co-transport with other molecules. E.g. Glucose
* Counter-transport of Hydrogen ions (Na+ in, H+ out)

Question 9

Proximal Convoluted Tubule: Cell to Blood

Answer 9

Na+ moved from cells to interstitial space & then blood via active transport:
* Na+/K+ ATPase pump, requires ATP
* K+ returns to interstitial fluid via ion channels, down the [gradient]

Question 10

Loop of Henle: Tubule to Cell

Answer 10

Na+ moved from tubules into cells through cotransport with K+ and Cl-
K+ moves back into tubule via ion channels down the [gradient]

Question 11

Loop of Henle: Cell to Blood

Answer 11

Na+/K+ ATPase moves Na+ out to interstitial space & K+ into cells via active transport.
K+ moves back into tubule via ion channels down the [gradient].

Question 12

Collecting Duct Na+ Reabsorption: Tubule to Cell

Answer 12

Na+ moves into cell and K+ moves out through ion channel down [gradient]

Question 13

Collecting Duct Na+ Reabsorption: Cell to Body

Answer 13

Na+/K+ ATPase moves Na+ out to interstitial space and K+ into cells

Question 14

Describe: Aldosterone

Answer 14

A steroid hormone which regulates Na+ reabsorption & blood pressure.
Acting within collecting duct tubule cells, increasing expression of ion channels & Na+/K+ ATPase

Question 15

Water Reabsorption: Loop of Henle

Answer 15

Ascending loop absorbs salts making a hypertonic solution, where water is absorbed in the descending loop.

Question 16

Water Reabsorption: Collecting Ducts

Answer 16

Contains aquaporins - water channels.
The interstitial space is full of salt from reabsorption, letting water out of cell through the tubule into the interstitial space.
Vasopressin - a hormone which makes more water channels

Question 17

Carbonate reabsorption

Answer 17

Carbonic acid created in tubule cells breaks down into H+ & HCO3-
H+ transported into tubules, combines with filtered HCO3- into Carbonic Acid.
The HCO3- is transported into body.
While filtered HCO3- becomes water and CO2, forming carbonic acid again, whilst HCO3- generated inside cell enters the body.
Net result: no loss of HCO3-

Question 18

Carbonate Generation – H+ Secretion:

Answer 18

Carbonic acid generated in tubular cells.
H+ combines with filtered phosphate (HPO42-) & is excreted.
HCO3- transported into body
Net result: Gain of HCO3-

Question 19

Carbonate Generation – Glutamine Metabolism:

Answer 19

The glutamine enters tubule cells either from the filtrate or blood plasma, then glutamine is metabolised inside the cell to ammonia (NH4+) & HCO3-
Ammonia secreted into the tubules & excreted
HCO3- transported into the body
Net result: Gain of HCO3-

Question 20

Acidosis response:

Answer 20

Lots of H+ is secreted into tubules, so all filtered HCO3- is reabsorbed, & additional HCO3- is absorbed as H+ excreted bound to phosphate.
Glutamine metabolism enhanced generating more HCO3-

Question 21

Alkalosis Response:

Answer 21

H+ secretion into tubules cannot keep up with filtered HCO3-, excess HCO3- excreted.
Glutamine metabolism decreased reducing HCO3- generation

Question 22

Urine pH & Drug excretion:

Answer 22

In alkaline urine, acidic drugs are ionised
In acidic urine, alkaline drugs are ionised
Ionised drugs are more water soluble, which increases their excretion.