kidneys Flashcards
parts of nephron (2)
- glomerulus (gcn surrounded by bowmans capsule)
2. system of tubules (proximal tubule, thin segment and distal tubule)
type of blood flow into kidneys (and 2 other places in body it occurs) 3
- afferent atriole -> capillaries -> efferent atriole
this is called portal circulation - also in liver and (3) ant pituitary gland
name of afferent artery and capillaries in kidney
renal artery
glomerular capillary net
3 steps to urine formation (and location)
- filtration of plasma, in GCN
- reabsorption, in proximal tublue, thin segment and distal tubule
- excretion
filtration pressures (3) and their sum (1)
- GHP (glumeral hydrostatic pressure) = 60 mmHg pushing plasma out of glomerulus into bowmans capsule
- Bowmans capsule (HP) = 18 mmHg - opposing filtration
- Colloid Osmotic Pressure (COP) aka oncotic pressure = 32 mm Hg - ave pressure of blood going in (28) and and coming out (36) of GCN
- sum of all these is net filtration pressure = (60-18-32) = 10mm Hg
filtration coefficient (def and #)
- amount of filtrate made in 1 minute by both kidneys
2. = 12.5 mL * 10 = 125 mL filtrate/ min (=180L/day)
5 layers of the filtration membrane
- endothelium
- basement membrane
- dead space
- basement membrane of bowmans capsule
- epithelium of bowmans capsule (podocytes)
reabsorption in proximal tubule (4)
starts in proximal tubule and is an active process
1. Na in filtrate => epithelium of proximal tubule
2. leaves epithelium by active transport => interstitial space => capillaries (because this is active there is an electrochemical gradient which recruits more Na)
3. because Cl is stupid, it follows
4. water follows salt
this process is 60% of reabsorption
reabsorption in thin segment (2- location and type of absorption)
- thin segment is in medulla
2. passive reabsorption of water
reabsorption in distal tubule (3)
- same as in prox tubule but under control of aldosterone
- aldosterone actively causes reabsorption of Na but filters out K
- wall of distal tubule is impermeable to H2O in normal conditions, so water is stuck in tubule (filtrate) and creates very dilute filtrate => collecting tubule
permeability of distal tubule to water (3)
- controlled by anti-diuretic hormone (aka vasoporessin)
- secreted by pituitary
- when secreted the walls are permeable to H2O which allows reabsorption when the body needs to retain H2O (desert)
2 anatomical factors that give the kidney to determine needed [urine]
- justamedullar nephrons (10%)
2. vasarecta (blood vessels) that follow tubules deep into medulla
2 physiological factors that give the kidney to determine needed [urine]
- very slow blood flow thru vasa recta (2% of blood flow in kidney)
- counter current mechanism
counter current mechanism (4)
- traps Na in medulla, making it hyperosmol (up to 4x more than regular)
- when body needs H2O => releases anti-diuretic hormone => more permeable collecting tubule
- hyperosmolarity medulla sucks H2O fro tubule back into body -> increased [urine]
- when body needs to get rid of H2O, no hormone is secreted and highly diluted filtration is excreted
macula densa (3) (location and description) renin- angiotensen system (type of feedback and details) (5)
- located at distal tubule where the walls touch both the afferent and efferent atriole
- macula densa are cells of epithelium located in the distal tubule that have golgi apparatus on the basal side (look different)
- as BP decreases => less filtration pressure => less stretch on tubular walls which is sensed by epithelial cells of macula densa
- this impacts walls of AA and EA, which release granules of renin into blood
- when renin enters plasma, quickly => angiotensen I
- in lungs angiotensen I => angiotensen II
- this is a very powerful, systemic vasoconstrictor => increase in BP
- this is a (-) feedback mechanism; started with BP decreasing => release of chemical that causes vasoconstriction which causes increase in BP
