PHYS20008 Lecture Notes - Lecture 23: Distal Convoluted Tubule, Proximal Tubule, Efferent Arteriole
12 Jun 2018
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Lecture 23
PHYS20008 - HUMAN PHYSIOLOGY
LECTURE 23
EXCRETORY SYSTEM
KIDNEY FUNCTION
•Filtration of water soluble waste products, regulating B
(by controlling blood volume through regulating Na+
balance), electrolyte balance, H2O balance. Lipid
soluble waste products are gotten rid of by the liver.
•Which urine contents are waste products?
•Water, sodium, hydrogen ions, creatinine, calcium,
urea. They’re all water soluble.
•What is urine made mostly of?
•ICF, interstitial fluid, blood, plasma.
•How much plasma does it take to make up 2L of
urine?
•0.2L, 2L, 20L, 200L.
•Top right diagram:
•Concentrations of these things are much lower in our
plasma than in our urine. So how can we put something
into the kidneys at a low conc (eg. The plasma) and have
something come out (urine) at high concentrations of
the same things? The stuff all goes in, we reabsorb
the water and the stuff stays. We can also use energy
to secrete or pack it in there.
NEPHRONS
•Outer layer is cortex, inner layer is medulla.
•Cortex = bark of a tree in latin.
•Inside the cortex there are nephrons; the
functional unit of a kidney. There are 1 million
nephrons in a kidney. So 2 million in your body.
•Filtration occurs in the glomerulus. The tube coming
out of the glomerulus is right next (proximal) to the
glomerulus. So it is the proximal convoluted tubule.
It is where the bulk reabsorption of Na+ and H2O
occurs. This means we want to increase SA for
absorption, so the inside has microvili to aid
absorption.
•The next part is the Loop of Henle. It has an
ascending limb and descending limb. The next
convoluted tubule is the distal convoluted tubule.
Next to this is the connecting tubule which
connects it to the collecting duct, which has
multiple tubules connecting to it. The outer
part of the glomerulus is the Bowman’s
capsule, which has arterioles moving into it.
So blood flow moves in but only a small
portion of it is filtered through the tubes;
the rest goes back out. The arteriole leading
into the kidney is the afferent arteriole, and
the one leading out of the kidney is the
efferent arteriole. Remember by ‘A before
E’. Also called pre glomerular arteriole and !
Document Summary
Kidney function: filtration of water soluble waste products, regulating b (by controlling blood volume through regulating na+ balance), electrolyte balance, h2o balance. Lipid soluble waste products are gotten rid of by the liver: which urine contents are waste products, water, sodium, hydrogen ions, creatinine, calcium, urea. The stuff all goes in, we reabsorb the water and the stuff stays. We can also use energy to secrete or pack it in there. Nephrons: outer layer is cortex, inner layer is medulla, cortex = bark of a tree in latin, inside the cortex there are nephrons; the functional unit of a kidney. There are 1 million nephrons in a kidney. So 2 million in your body: filtration occurs in the glomerulus. The tube coming out of the glomerulus is right next (proximal) to the glomerulus. It is where the bulk reabsorption of na+ and h2o occurs.
