29 Flashcards
Which kidney is most inferior, and why?
The right, because of the location of the liver
What structures comprise a kidney lobe?
A medulllary pyramid and the cortex that surrounds it
What is the nephron
Microscopic
functional unit of
the kidney
How many nephron per kidney
Approx 1 million
What is a nephron responsible for
Urine formation
Two types of nephron
- Cortical nephrons
- 85%
- Lie mainly in cortex
- Juxtamedullary nephrons
- Extend deep into medulla (renal corpuscle is located towards the boundary of cortex and medulla)
- Important for the formation of concentrated urine
Types of Nephron
- Cortical nephrons
- 85%
- Lie mainly in cortex
- Juxtamedullary nephrons
- Extend deep into medulla
- Important for the formation of concentrated urine
Function of The nephron and associated structures
• Selectively filter blood (into the glomeric capsule)
• Return to blood anything to be kept
• Carry waste away for storage & expulsion
Each nephron is comprised of:
– A Glomerular capsule
– Renal tubules
– A collecting duct
Each nephron is associated with:
– A glomerulus
– Peritubular capillaries
Glomerular capillaries are specialised for:
Filtration
Structure of Glomerular capillaries
Thin walled single
layer of fenestrated
endothelial cells
What are the Glomerular capillaries fed and drained by?
Arterioles
Blood pressure in the Glomerular capillaries is
Tightly regulated
What are Peritubular capillaries
Specialised for?
Absorbtion
What do Peritubular capillaries
Wrap around?
Renal tubules
Where does Peritubular capillaries receive what kind of blood from?
Receives filtered blood from
glomerulus via efferent
arterioles
Peritubular capillaries reserve reabsorbed filtrate from where?
Receives reabsorbed filtrate
from nephron
What do peritubular capillaries receive from nephrons?
reabsorbed filtrate
Some non-______ solutes that
need to be ______ can pass
from ________ capillaries into _______
Some non-filtered solutes that
need to be excreted can pass
from peritubular capillaries into nephron
Vasa recta - what are they?
- Extensions that follow nephron
loops deep into the medulla - Only found with juxtamedullary
nephrons
(The way they are associated with the long nephron loops means sodium chloride can be concentrated down in the medulla, as sodium levels the nephron can be taken in by the vasa recta and taken down into the medulla, when water is reabsorbed from the descending limb instead of accumulating in medullary region it can enter the capillary end of vasa recta and be returned to the veins - getting rid of water)
Foetal development of Renal capsule
What is the glomerus enclosed by?
Glomerulus enclosed by the Glomerular
capsule
Where does the capillary and nephron meet?
The renal corpuscle
What is the site of the filtration barrier ?
The renal corpuscle
What is the first part of the nephron ?
Glomerular capsule
Glomerulat capsule is also known as the
Bowman’s
capsule
Two layers of the glomerular capsule
- Outer parietal layer of simple squamous cells
- Inner visceral layer of podocytes
What is between the two layers of the glomerular capsule and what does it receive
Between the two
layers is the
capsular space
(a.k.a. Bowman’s
space/urinary
space) which
receives filtrate
Renal corpuscle is made up of
- glomerulus
- glomerular capsule
What surrounds the glomerular capillaries
Podocytes
What are podocytes
Very branched, very specialised epithelium
Branches form
intertwining foot
processes called
Pedicels
What forms between pedicels
Filtration slits
What passes through the filtration slits
Filtered blood (filtrate)
goes through these slits
and passes into capsular
space
Filtration barrier is also called the
blood-urine barrier/glomerular
capsular membrane
Filtration barrier lies between
blood and capsular space
Filtration barrier allows
free passage of water and small
molecules
Filtration barrier restricts the passage of
most proteins
RBCs are not filtered into nephron
Three layer of the filtration barrier
– Fenestrated endothelium of glomerular capillary
– Fused basement membrane (contains collegian and proteoglycans)
– Filtration slits between the pedicels of the podocytes
Yas
What happens after filtrations?
• Urine is waste fluid and solutes filtered from the blood
• Not everything that is filtered is excreted
• Some filtrate is reabsorbed
• And some of what wasn’t filtered is secreted into the nephron
• So, urine = Filtered – Reabsorbed + Secreted
What happens in the Proximal convoluted tubule
• Bulk reabsorption (2/3)
What surrounds Proximal convoluted tubule
Surrounded by
peritubular capillaries
Proximal convoluted tubule (PCT) structure
• Structure:
– Cuboidal epithelial cells
– Dense microvilli (brush border) on luminal membrane
– Highly folded basolateral membrane
– Many mitochondria for active transport
– Leaky epithelium
What is the nephron loop also known as?
Loop of Henle
Where does the nephron loop down into?
The medulla
What is the length of the nephron important for?
- Length is important in production of dilute/concentrated urine
What is the nephron loop surrounded by? (juxtamedullary nephrons
only)
vasa recta
Structure of the Nephron loop
Thick descending limb
- Similar to PCT structure
Thin descending limb
- Simple squamous epithelium
Thin ascending limb
- Simple squamous epithelium
Thick ascending limb
- Similar to DCT structure
Nephron loop Different permeabilities to:
water and sodium
What happens mainly in distal convoluted tubule
- fine tuning (with hormones - ADH and actedlytone)
What kind of epithelium in DCT
Cuboidal
epithelium,
Distal convoluted tubule is _______ is proximal DT
Thinner
Structure of DCT
Structure
- Few microvilli = no brush border
- Fewer mitochondria
- Reabsorption influenced by aldosterone
Main role of collection duct:
Fine tuning
(Principle cells absorb secreting potassium, absorbing sodium, reabsortion g water
Intercollated cells secrete hydrogen and bicarbonate ions)
Filtrate from several _____ drains into one _________, which empty at _______
Filtrate from several
DCTs drains into one
collecting duct, which
empty at papilla
Structure of Collecting duct
Wall of simple cuboidal epithelium
Principal cells
- Reabsorption
Intercalated cells
- Acid/Base balance
Reabsortion in the collecting duct is influenced by
Reabsorption influenced by aldosterone and ADH
• Understanding
the structure of the epithelium throughout the nephron is essential to help you to understand the function of each section
Yeh
Histology of the nephron
\
Flow of filtrate/urine through the nephron and kidney
Do this
Describe the gross internal structure of the kidneys,
including a brief overview of the path of blood towards the site of filtration. Describe the structures present in the renal corpuscle that allow filtration from the blood to
occur, and which vessels receive reabsorbed filtrate.
