Vander's Ch. 1 Function and Anatomy Flashcards
Functions of the kidney
1) Waste excretion
2) Blood pressure regulation
3) Regulates RBC production
4) Produces vitamin D
5) Gluconeogenesis (although most occurs in the liver)
How do the kidneys regulate RBC production?
Release of erythropoietin (stimulated by decrease in partial pressure of O2 in the kidneys)
How many nephrons are in each kidney?
1 million
What is the function of the renal corpuscle?
separation of a protein-free filtrate from plasma (initial step in urine formation)
What forms the renal corpuscle?
Combination of glomerulus and Bowman’s capsule
What is the glomerulus?
tuft of interconnected capillary loops where blood flows to be filtered
What is Bowman’s capsule?
hollow capsule that surrounds the glomerulus (has fluid filled space called Bowman’s space that holds filtered fluid)
Has two ends:
1) vascular pole
2) filtrate pole (has opening that leads into 1st portion of the tubule)
What 3 cell types make up the Juxtaglomerular apparatus?
1) Granular cells (secrete renin)
2) Macula densa
3) Extraglomerular mesangial cells (phagocytes)
What are the 3 layers of the filtration barrier in the renal corpuscle?
1) capillary endothelium of glomerular capillaries
2) Thick basement membrane
3) single-celled layer of epithelial cells
What do podocytes sit on?
glomerular capillary loops inside Bowman’s space
What are the characteristics of the capillary endothelium, the first barrier in filtration?
- fenestrated
- permeable to everything in blood except RBC and platelets
What are the characteristics of the capillary basement membrane?
gel-like acellular meshwork of glycoproteins and proteoglycans
What are the characteristics of the 3rd barrier, the epithelial cells?
podocytes! sit on basement membrane; pedicels (foot like processes) interdigitate with each other and spaces between them form path thru which filtrate enters Bowman’s space
Podocytes are linked by what type of cellular connection?
slit diaphragms (widened versions of tight junction)
What are the two segments of the proximal tubule and where does it start?
1) Proximal convoluted tubule (coiled segment)
2) Proximal straight segment (descends toward medulla)
prox tubule starts at end of Bowman’s capsule
The proximal tubule drains into what….
the descending thin loop of Henle
What are the specialized cells in the thick ascending limb closest to Bowman’s capsule?
Macula densa
The macula dense marks the end of the ____________ and the beginning of the ___________
thick ascending limb; distal convoluted tubule
Flow of filtrate from distal tubule:
cortical collecting duct–>large ducts–> papillary collecting ducts –> calyx
Pathway of fluid flow in a nephron
cortex (Bowman’s capsule) –> medulla (descending loop) –> cortex (thick ascending loop) –> medulla (medullary collecting tubule –> CALYX
True or false: the tubular epithelium has a one-cell thickness throughout
true
________ arteries go into the glomerulus, ________ arteries come out of it
afferent; efferent
Which part of the kidney receives greater blood flow, the cortex or the medulla?
CORTEX (no glomeruli in the medulla)
What are the vasa recta?
straight, parallel vessels that penetrate deep into the medulla
3 kinds of nephrons
1) superficial cortical nephrons
2) midcortical nephrons
3) juxtamedullary nephrons
(all have differing lengths of loop of Henle)
What is the macula densa responsible for?
detecting luminal content of nephron at end of thick ascending limb and contribute to GFR
Definition of filtration
process by which water and solutes in blood leave vascular system thru filtration barrier and enter Bowman’s space
Definition of secretion
process of moving substances into tubular lumen from cytosol of epithelial cells from the walls of the nephron (either come from interstitium or originate from cells)
Definition of reabsorption
process of moving substances from lumen across the epithelial layer into the surrounding interstitium (then onto blood vessels - 2 step)
Definition of excretion
exit of substance from the body
True or False: the filtrate present in Bowman’s space is very chemically similar to blood plasma
True BUT filtrate does not contain much protein
What is the avg GFR in a young, adult male?
180L/day
total plasma volume is 3L so it is filtered 60 times a day!
Once tubular cells reabsorb material, where does it go to get back to the body’s main system?
peritubular capillaries (branches of efferent arterioles)
What percentage of the plasma is filtered into Bowman’s space?
20%
What are the 3 basic renal processes?
1) glomerular filtration
2) tubular reabsorption
3) tubular secretion
What do sympathetics control in the kidney?
1) renal blood flow
2) glomerular filtration
3) release of vasoactive substances (renin-angtiotensin)
What does aldosterone regulate and from where is it secreted?
sodium and potassium excretion
secreted from adrenal cortex
What does the proximal tubule reabsorb?
2/3 of the filtered water, sodium, and chloride
What does the loop of henle reabsorb?
20% of the filtered sodium
10% of filtered water
(reabsorbs slightly more salt than water to make the luminal fluid more dilute than plasma)
What part of the nephron do aldosterone and ADH act on specifically?
cortical collecting tubule
How do aldosterone and ADH differ?
Aldosterone: enhances Na reabsorption and K secretion
ADH: enhances water absorption
