Histology Flashcards
Location of pain fibers of the kidney
renal pelvis
calyces
ureter
renal capsule
muscles the kidneys lie over in the abdominal wall
quadratus lumborum
psoas muscles
what part of the kidney does not contain afferent pain fibers
parenchyma
afferent innervation of the kidney
abdominal and thoracic splanchnic nerves
these terminate in the renal capsule, renal pelvis & major & minor calyces
divisions of the renal artery prior to entering the hilum
anterior and posterior divisions
Where do the arcuate arteries start?
cortico-medullary junction
What serves as the margins of the renal lobules?
interlobular arteries
these give off afferent arterioles
What type of gland is the kidney considered to be?
compound tubular gland
Contents of the medullary ray
straight tubules (both proximal and distal) cortical collecting ducts
embryologic origin of the nephron
metanephric blastema
What part designates the termination of the nephron?
connecting tubule
Note: the collecting ducts are not part of the nephron
embryologic origin of the collecting ducts
ureteric bud
do not have a loop of Henle that penetrates the inner medulla or an ascending thin limb of LOH
cortical nephrons
What type of epithelium lines Bowman’s capsule?
simple squamous epithelium
aka parietal epithelium
What type of endothelium lines the glomerular capillary?
fenestrated endothelium
What composes the visceral epithelium of the renal corpuscle?
podocytes
cells which play a role in regulating the sieving coefficient (Kf) of the glomerular filter
mesangial cells
They alter the caliber of the lumen of the glomerular capillaries and the size of the endothelial fenestrations with their contractile properties
3 Elements of the Glomerular Filtration Barrier
glomerular capillary endothelium basal lamina (shared by endothelium and epithelium) podocytes
mesangial cells are derived from?
bone marrow
cells which play a role in regulating the sieving coefficient (Kf) of the glomerular filter
mesangial cells
What generates the negative charge of the lamina rara externa?
heparan sulfate and other glycosaminoglycans and glycoproteins
What size molecules are restricted from passage through the GB lamina (GBL)?
36 Angstroms or 70 kD (70,000 Daltons)
Which layer of the GBM contains Type IV collagen fibers layered to prevent filtration of albumin
lamina densa
Which part of the GBM are pedicels of podocytes attached?
lamina rara externa
What generates the negative charge of the lamina rara externa?
heparan sulfate and other polyanions
What size molecules are restricted from passage through the GBM?
36 Angstroms or 70 kD (70,000 Daltons)
What anchors nephrin 2 to the pedicels?
CD2-associated proteins & podocin
Podocin is attached by zonula occludin-1, F-actin and CD2-associated protein
Size of albumin
66-68 kD
since molecules greater than 70 kD are restricted, the negative charge is important in prevention of albumin from passing into the filtrate
What height does the filtration sit above the glomerular basement lamina?
60 nm
It is the final barrier to the glomerular capillary lumen
Surface area of the rectangular filtration pore
56 nm2
What anchors nephrin 2 to the pedicels?
CD2-associated proteins & podocin
Size of albumin
66-68 kD
Which part of the proximal tubule is not in the cortex?
S3
It is only as long as the outer stripe of the medulla.
All S3 segments terminate at the junction of the outer and inner stripes.
Area of the rectangular filtration pore
56 nm2
Receptors of the proximal tubule membrane for endocytosis of albumin
Megalin and Cubulin
these prevent protein from appearing in the urine, since protein is normally filtered daily
Which parts of the proximal tubule are convoluted?
S1 and part of S2
Transporters of the proximal tubule that remove anion molecules from the blood to the lumen
on the basolateral side: OAT1 and OAT3 and NaC3 (dicarboxylate transporter)
on the luminal side: MRP2 and MRP4
greatest number of these transporters is in S2 and S3
Describe the differences in the S3 segment of the proximal tubule
mitochondria are smaller and ovoid (rather than long in S1-S2)
much less complex
Enzyme of the proximal tubule that converts Vit D to the active form (1,25-dihydroxycholecalciferol)
1alpha-hydroxylase
Which segment of the proximal tubule has the greatest number of secondary lysosomes?
S2
Transporters of the proximal tubule that remove anion molecules from the blood to the lumen
on the basolateral side: OAT1 and OAT3 and NaC3
on the luminal side: MRP2 and MRP4
Activity of these 2 enzymes is the highest in the proximal tubule brush border, higher than anywhere else in the body
gamma-glutamyltransferase
dihydropeptidase
Enzyme of the proximal tubule that converts Vit D to the active form
1alpha-hydroxylase
Which segment of the proximal tubule has the greatest number of lysosomes?
S2
Where do all thin descending limbs of the LOH begin?
at the junction of the inner medullary and outer medullary stripes
Where are ascending thin limbs found?
intermediate and juxtamedullary nephrons
Where does urea enter the medullary interstitium?
at the bend of the thin ascending limb in the papillary region
Where do all ascending thick limbs of the LOH begin?
at the junction of the inner stripe of the outer medulla with the inner medulla
Another name for the straight segment of the distal tubule
pars recta
may mean straight segment, in general
Features of the epithelium of the thick ascending limb
cuboidal
no brush border
Thick basolateral membrane
numerous long mitochondria perpendicular to the basal lamina (almost span the thickness)
central nucleus
Called the “diluting segment” -> where furosemide inhibits the Na/K/2Cl transporter
Why is the basolateral membrane of the thick ascending limb thicker?
to accommodate the numerous Na-K ATPases required to provide the sodium gradient
What features of the thick ascending limb of the LOH are absent from the macula densa cells?
extensive basolateral invaginations & long mitochondria
Where are renin granules located?
in the modified smooth muscle cells of the afferent arteriole
What is the primary effect of PTH on the DCT?
promote calcium reabsorption by the Na/Ca exchanger
Features of the epithelial cells of the DCT
basolateral infoldings and greater-sized mitochondria push the nucleus toward the apical membrane
Where is the Na-Cl cotransporter exclusively located?
distal convoluted tubule
What is the primary effect of PTH on the DCT?
promote calcium reabsorption by the Na/Ca exchanger (NCXT)
The receptors for PTH are on the basolateral membrane
Where are calbindin-D28K and calcium channel TRPV5 expressed?
connecting tubule and second half of DCT
Which 2 distal segments reach the subcapsular space?
DCT and CCT (cortical or initial collecting tubules)
Look for the capsule to help identify the segment as DCT rather than medullary thick ascending limb (the cells look the same in DCT and TAL)
Where is the activity of the Na-K-ATPase the greatest?
Distal convoluted tubule
This is from the ppt and not logical at all
What 2 types of epithelial cells are located in the connecting tubule?
connecting tubule cells & intercalated cells (alpha type predominates)
The connecting tubule is the first distal segment of the nephron with 2 morphologically distinct epithelial cells
What are the effects of aldosterone on the connecting tubule (the first segment to respond)?
increased transcription of amiloride-sensitive ENaCs and the Na-K-ATPase
Transporters of the alpha-intercalated cells in the cortical collecting tubule and cortical collecting duct
apical (luminal) H+-ATPase for H+ excretion
basolateral Cl-/HCO3- exchanger AE1
Note: beta-intercalated cells have the Cl-/HCO3- exchanger on the apical membrane for bicarb secretion
Features of the intercalated cell
Darker staining
larger
small microvilli (microplicae) on the luminal membrane
smaller ovoid nuclei
thinner basolateral membrane, relative to the connecting tubule cell
Features of the cortical collecting duct
7-8 cortical collecting tubules merge to form 1 cortical collecting duct
principal cells that respond to aldosterone (increased transcription of amiloride-sensitive ENaC & Na-K-ATPase)
alpha and beta intercalated cells in similar numbers
Contribute to chronic metabolic acidosis in hyperglycemia
H+-ATPases in the cortical collecting tubule and duct are nonenzymatically glycosylated, making them nonfunctional
Factors determining K+ secretion by the cortical collecting duct and tubule
plasma levels of K+
aldosterone
ANG II
Features of the principal cells
Light staining "light cell" low cuboidal few sub-nuclear basolateral infoldings ovoid nucleus highly responsive to aldosterone
Where are the cilium that serve as mechanosensors located?
principal cells of the cortical collecting duct
ECM protein of the cilium mechanosensor of principal cells
polycystin-1
gene mutation implicated in ADPKD
calcium permeable channel of the cilium mechanosensor of principal cells
polycystin-2
gene mutation implicated in ADPKD
2 transporters expressed by medullary collecting duct intercalated cells
electrogenic H+-ATPase
electroneutral H+-K+-ATPase
both are located on the luminal membrane and are regulated by K+ homeostasis, having important effects on acid-base homeostasis
Describe the inner medullary collecting duct
3 segments: IMCD1, IMCD2, IMCD3
IMCD1 is similar to the outer medullary collecting duct
IMCD2 and IMCD3 has 1 cell type: columnar & devoid of organelles
AQP2 (apical) APQ3 & APQ4 (basolateral) expression increased for water transport in response to ADH (AVP)
Urea is transported in IMCD2 & IMCD3
AQP2 expression in cortical collecting tubule principal cells and connecting tubule cells
increased expression on basolateral membrane (with AQP3 & AQP4) for water reabsorption in response to aldosterone
note read slide. This info is very confusing and picky
Which urea transporters are expressed exclusively in IMCD cells?
UT-A1 (apical)
UT-A3 (intracellular & basolateral)
Where is UT-A1 expressed?
IMCD3
Where is UT-A2 expressed?
descending thin limb of LOH
Another name for IMCD3
papillary collecting duct
What type of cell is involved in EPO synthesis?
type 1 cortical interstitial cells
Types of cortical interstitial cells
2 types:
type 1 -> resembles fibroblast & synthesizes & secretes EPO
type 2 -> lymphocyte like
What is the function of type 1 medullary interstitial cells?
synthesize prostaglandins (PGE2)in response to ANG (receptors for ANG are present in the medullary interstitial cells) *these do NOT synthesize EPO
Function of medullary type 2 interstitial cell
phagocytosis
pericyte found between two leaflets of the basement membrane of the vasa recta (in outer medulla & outer-inner medulla)
type 3 interstitial cell
absent from type 1 medullary interstitial cells
EPO mRNA
ecto-5’-nucleotidase
What mediates prostaglandin synthesis by medullary interstitial cells?
COX-2
this increases during water deprivation and hypertonicity
What is in the lipid droplets of the medullary type 1 interstitial cells?
triglycerides rich in arachidonic acid and cholesterol esters
How many minor calices are present in a multilobar kidney?
7-12
3-4 minor calyces merge to form a major calyx
3-5 major calyces merge to form the renal pelvis
Parasympathetic innervation of the renal pelvis and ureters
S2-S4 via the inferior and superior hypogastric plexuses
Muscle layers of the ureter
Upper 2/3 has 2 outer layers of smooth muscle, the innermost layer being longitudinally oriented
Lower 1/3 has a 3rd layer of outer smooth muscle oriented longitudinally.
arterial blood supply to the bladder
internal iliacs
Segments of epithelium of the urethra in males
transitional epithelium -> prostatic urethra
pseudostratified columnar or stratified columnar -> membranous urethra
pseudostratified columnar epithelium -> penile urethra
Note: urethral opening: nonkeratinized stratified squamous
Segments of epithelium in female urethra
initial segment is transitional epithelium
near the urethral orifice: nonkeratinized stratified squamous epithelium
female urethra has paraurethral glands that secrete an alkaline substance
What type of gland is the prostate?
compound tubulo-alveolar gland
Key identifying feature of the prostate
concretions in the lumen and some glandular regions
Other features:
capsule on posterior and lateral surfaces
anterior portion has no glandular epithelium and is covered in stroma