endocrine impacts on kidney function

Question 1

describe renal structure and function

Answer 1

• contains hundreds to thousands of small functional units called nephrons
• a nephron is basically a small tubule with a vascular component
• prinicple role is to filter out and excrete the bad stuff whilst preventing loss of useful stuff and water
• 3 components to function: filtration,, selective resporption and secretion
• kidney functions depends on the number of availible nephrons
• there is a functional reserve so it may take >70% nephron loss to see impact

Question 2

describe how filtration and resoption of the kidneys

Answer 2

• ultrafiltration occurs between the capillaries of the golmerulus and bowmans capsule
• is filtration under pressure, pressure increase caused by having narrower afferent arteriole
• filtration depends on molecule size and charge
• how much plasma gets filtered is glomerular filtration rate (GFR) which depends on renal blood flow/pressure and number of availible nephrons
• most resportion occurs in the proximal convoluted tubule
• epithelial cells linin tubule have microvilli at the luminal surface, folds at the capillary surface and many mitochondria

Question 3

list substances the body wants to excrete. retain?

Answer 3

excrete:
- nitrogenous waste (urea and creatinine)
- phosphorus
- potassium

retain:
- water
- electrolytes
- glucose
- protein
- urea

Question 4

explain how urine is concentrated vs dilute

Answer 4

• medullary conentration gradient depends on different permeability in different parts of the nephron, associated vascular network, urea, and loop of henle collecting ducts
• collecting ducts are final stage of water resportion
• hormones influence retention/excretion (ADH and RAAS)

Question 5

what is osmotic diuresis? what causes it

Answer 5

increased urination due to the presence of certain substances in the body
caused by glucose in tubule acting as osmolyte, drawing water into the tubule by osmosis, = greater urine production
- also caused by salts, or therapeutic diuretics

Question 6

what is azotaemia

Answer 6

• increased blood levels of urea or creatinine
• coud be due to not enough blood being filtered or not enough nephrons to do the job

Question 7

what is urine specific gravity

Answer 7

• a measure of concentration of urine
• if filtrate neither concentrated or dilute, should be between 1.008-1.012
• we expect dehydrated, poor renal flow cases to have concentrated urine

Question 8

what is diabetes insipidus

Answer 8

• something is stopping the action of ADH (not being made or action being blocked)
• ADH acts on the part of the nephron between the most dilute to the final urine concentration

Question 9

summarise renal function

Answer 9

• glomerulus filters the plasma, cells and proteins do not pass into the filtrate
• PCT then reabsorbs the useful stuff
• the loop of henle concentrates the tissue fluid of the medulla
• water passes by osmosis from the filtrate into the medulla
• the amount of water reabsorbed is controlled by ADH at collecting ducts
• Na and water can be further conserved through aldosterone action in distal nephron

Question 10

what is PTH and how is the kidney involed

Answer 10

primary hyperparathyroidism: excessive PTH promote renal calcium retention and phosphate loss