Glomerular Filtration Flashcards
(14 cards)
Define filtration
process where water and small solutes are forced from the blood within the glomerulus into the capsular space
Define reabsorption
process where renal tubules reclaim water and solutes from the tubular fluid and return them to the blood
Define secretion
process where the renal tubules extracts chemical from the capillary blood and secretes them into the tubular fluid
Components that stay in the blood during glomerular filtration
- blood cells
- plasam proteins
- large anions
- protein- bound minerals and hormones
Components that leave the blood during glomerular filtration
- water
- urea
- electrolytes
- glucose
- amino acids
- fatty acids
- vitamins
- uric acid
- creatinine
Describe the layers that filtrates need to pass through during glomerular filtration
fenestrated endothelium:
- endothelial cells are honeycombed with large pores
basement membrane:
- contains a proteoglycan gel that prevent large solutes to reach the other side
filtration slits:
- contain tiny slits that only allow for extremely small solutes to pass through
What pressure pushes the filtrate out of the blood during glomerular filtration
blood hydrostatic pressure (BHP)
What is glomerular filtration rate (GFR)?
amount of filtrate formed per minute by both kidneys
typical values:
- male: ~ 125 mL/min
- female: ~ 105 mL/min
Describe the two autoregulatory mechanisms that kick in when GFR is too low
mesangial sensors:
juxtaglomerular cells:
Describe podocytes and how they impact the glomerulas
- octopus-shaped cell in the visceral layer of the glomerular capsule
- forms the filtration membrane
- prevents proteing loss
- regulates filtration
What neural and endocrine mechanisms control GFR?
neural control:
- sympathetic nervous system: constricts afferent arterioles, reducing GFR and urine output
endocrine control:
- renin-angiotensin-aldosterine mechanism: low BP stimulates renin release, which produces angiotensin II, which constricts efferent arterioles and stimulates aldosterone secretion
- natriuretic peptide: secreted by the heart due to high BP which dilates afferent arterioles, constrict efferent arterioles, and inhibit ADH and aldosterone secretion, increasing GFR
Function of macular densa
- sensory cells that secretes ATP when GFR is too high
- ATP is converted into adenosine
Function of justaglomerulus (granular) cells
- responds to adenosine by constricting the arteriole, reducing blood flow into the glomerulus and lowering GFR
- contains renin that is secreted in response to low BP
Renin angiotensin aldosterone pathway
- drop in BP stimulates kidney to release renin
- renin converts angiotensinogen to angiotensin I
- angiotensin-converting enzyme (ACE) in the lungs converts angiotensin I to angiotensin II
- this signals the hypothalamus in the brain to increase thirst and drinking; blood vessels to constrict, and the adrenal cortex to secrete aldosterone
- aldosterone signals the kidney to reabsorb more sodium and water
- all of these increase BP
