Renal: structure, function, glomerular filtration Flashcards
describe the course of nephron
renal corpuscle > proximal tube > thin descending LH > thin ascending LH > thick ascending LH > distal convoluted tubule > connecting tubule > cortical collecting duct > medullary collecting duct > papillary duct
what are the 2 types of nephrons?
- cortical (85%)
2. juxtamedullary (15%)
what are sturctural differences of nephrons?
cortical – short LH & thick ascending LH mostly in the cortex
juxtamedullary – long LH & mainly in the medulla
what is the functional role of cortical and juxtamedullary?
cortical - tubular reasorption (removal of solutes and H2O
juxtamed - maintain osmotic gradient in medulla
trace blood flow through renal artery
renal artery > interlobar a.a. > arcuate a.a. > interlobular a.a. > afferent arterioles > glomeruli > efferent arteriols > peritubular capillarties or vesa recta
how many capillary beds are associated with renal vasculature?
cortical - perttubular nephrons (90% of blood flow)
juxtamed - vesa recta (10% of blood flow)
major functions of kidney
- Regulate the volume of body water
- Regulate the balance of inorganic ions
- Regulate body pH
- Excrete metabolic waste products & foreign substances
- Produce hormones and enzymes
- Help regulate blood pressure
what is approx. osmolartiy of body fluids?
300 mOsm
what are the inorganic ions in osmolarity?
Na K Cl H HCO3
what metabolic waste is is excreted from by the kidney?
urea - nitrogen metab
uric acid - nucleic acid metab.
creatinine - creatinine phosphate
urobilinogen - Hb breakdown
what hormones are produced by the kidneys?
erythropoietin (EPO) Vitamin D3 (Calcitrol)
what enzyme is produced in the kidney?
Renin
what is EPO? when is produced?
a. protein that stimulates erythrocyte (RBC) production
b. when renal O2 pressure is low
what is calcitrol? what’s its function?
a. steroid
b. increase Ca and PO4 (phosphate) uptake in intestine
what is renin? What’s its function?
a. enzyme
b. hydrolyzes angiotensinogen to angiotensin 1 (Ang I). Ang I is converted to Ang II by angiotensin converting enzyme (ACE)
c. Renin increases arterial B/P
what is angiotensin?
peptide hormone that causes vasoconstriction
what causes H2O retention in kidney?
low MAP or blood volume > ADH/Vasopressin secretion > H2O retention
what causes an increase in MAP (in reference to kidneys)
low MAP or blood volume > Renin secrection > angiotensinogen conversion to Ang I > Ang I converted to Ang II (by ACE) > Vasoconstriction
What causes Na retention in the kidney?
low MAP or blood volume > Renin secrection > angiotensinogen conversion to Ang I > Ang I converted to Ang II (by ACE) > aldosterone secrection > Na retention
How is water ingestion triggered ?
thirst mechanism triggered by Ang II
what structures make up the juxtaglomerular apparatus (JGA)? what arteriole is it associated with?
a. juxtaglomerular cells and macula densa of distal tubule
b. afferent arterial
What structures compose the renal corpuscle?
bowman’s capsule (2 layers – parietal & visceral (podocyte - foot prosesses)
glomerular capillary
What 3 glomerular filtration barriers?
- endothelial cells
- basil lamina
- epithelial cells (podocytes)
What is true of endothelial cells?
- they are fenestrated
- plasm fluides freely permeate
- composed of pores
- part of the capillary lumen
what is true of the basil lamina?
- negatively charged
- repels negativly charged proteins
- extracellular matrix
- located between endothelial and epithelial cells
what is true of epithelial cells?
- a.k.a. podocytes
- octopus like structures
- compose filtration slits
- part of the lumen of bowan’s capsule
how does glomerular filtration occur?
occurs due to the difference between a blood pressure in the capillaries and a pressure in Bowman’s space.
which force favors filtration? opposes it?
a. favors - glomerular capillary pressure (Pgc) in mmHg
b. opposes - fluid pressure in Bowmans space (Pbs) and oncotic pressure ( ) (in mmHg)
what causes oncotic pressure?
large proteins in the plasma
oncotic pressue is higher than the pressure in bowmans space
calculate net glomerular filtration pressure
cut and paste pic
what is renal blood flow rate?
1 L/min
20% of resting CO
what is renal plasma flow rate?
625 mL/min (approx. 900 L/day)
how much of the plasma gets filtered in Bowman’s capsule? what is this known as?
a. approx. 180 L/day @ 125 mL/min (20% of renal plasma flow) the rest passes through glomerular capillaries into efferent arterioles
b. GRR - glomerular filtration rate
What is true of plasma filtration?
- 99% of filtered plasma is reabsorbed
- reabsorb approx 178-179 L/day
- excrete approx 1-2 L/day
- Plasma vol = 3 L
- filtered approx 60 times/day
How is GFR controlled?
constriction of dilation of afferent or efferent arterioles
how is the pressure between the arteries and capillaries in bowman’s space decreased ?
- constriction of afferent arteriole (increase resistance) OR dilation of efferent arteriole
- decreases glomerular capillary pressure (Gcp)
- decreases GFR
How is the pressue between the arteries and capillaries in bowman’s space increased?
- Constriction of efferent arteriole OR dilation of afferent?
- increases (Gcp) “dam’s it up”
- increases GFR
how to remember how GFR is decreased
"C.A.D.E. decreases GFR" Constricted Afferent arterioles or Dilated Efferent arterioles
NOTE: increase GFR is C.E.D.A
what are extrarenal requlators of afferent and efferent arterioles ?
neural inputs
hormones
what are the intrarenal regulators of afferent and efferent arterioles?
a.k.a autoregulation (independent of neural and homonal input
What are the mechanisms of intrarenal regulation?
myogenic
tubuloglomerular feedback
Describe the myogenic mechanism
Smooth muscles of afferent arterioles are stretched in response to high blood pressure → Stretch-activated ion channels are activated, leading to muscle contraction → reduces the volume of blood → reduces Pgc. Conversely, muscle relax → raise Pgc
Describe the tubuloglomerular feedback mechanism
Macula densa cells sense changes in luminal salt load → release paracrines → alter smooth muscle contraction in afferent arterioles → adjust Pgc
what cells receive the neuronal and hormonal inputs ?
mesangial cells (smooth muscle cells that surround the glomerular capillaries
constriction of cells reduce surface area of capillaries
