The Kidneys Flashcards
What is a nephron?
functional unit of the kidney where filtration and selective reabsorption takes place
describe filtration in the kidneys
blood flows through the glomerulus under high pressure
small molecules (urea, glucose etc), water and ions are filtered out the blood and into the bowman’s capsule of the nephron
Why do larger molecules (red blood cels etc) remain in the blood?
they are too large to fit through the pores in the capillary walls
Which substances are selectively reabsorbed from the nephron tubule?
All sugars
some water
some ions
What happens to the molecules which are not selectively reabsorbed?
travel down kidney tubule as urine and are transported the the bladder via the ureter. here they are stored and eventually excreted
how is concentration and volume of urine controlled?
controlled by the secretion of anti-diuretic hormone (ADH)
What produces ADH?
Pituitary gland
Describe how ADH affects the reabsorption of water from the kidneys tubule?
ADH increases the permeability of the collection ducts, enabling more water to be reabsorbed into the blood
What is required to maintain the ideal water content of blood?
negative feedback system involving:
receptors in hypothalamus
Hypothalamus
effector i.e. Pituitary gland
describe the negative feedback loop which occurs when low blood water concentration is detected. (7)
receptors detect low blood water content
send information to hypothalamus
sends instructions to pituitary glands
pituitary gland increases ADH secretion
ADH increases collecting duct permeability so more water is reabsorbed
blood water content increases
more concentrated urine is produced
describe the negative feedback loop when high water blood concentration is detected.
receptors detect high blood water content
send information to the hypothalamus
send instructions to pituitary gland
pituitary gland decreases ADH secretion
ADH decreases collecting duct permeability so less water is reabsorbed
blood water content decreases
more dilute urine is produced
How can kidney failure be treated?
Kidney transplant
Kidney dialysis
what is kidney dialysis?
a machine artificially filters a patients blood
How does kidney dialysis work?
selectively permeable barrier separates patients blood from dialysis fluid
materials are exchanged across the barrier etc urea, water and excess ions move out of blood and into dialysis fluid
large molecules remain in the blood
describe the composition of dialysis fluid
same conc of glucose and ions as in normal blood plasma
no urea
