Histology of urinary system Lecture 42 Flashcards
What are endocrine functions of the kidney?
-hydroxylation of 25-OH vitamin D3 to
1,25 OH2 (dihydroxyacetone)
-erythropoietin ( EPO): acts on bone marrow to regulate erythrocyte formation in low blood oxygen concentration
-secretion of renin- enzyme involved in blood pressure regulation
what is the embryonic origin of the kidney?
intermediate mesoderm
What is the capsule of the kidney like?
capsule thin fibrous capsule
where is the hilum located on the kidney?
at the concave medial border- the point of entry of neuromuscular supply and origin of the ureter ( renal pelvis)
What is the renal sinus of the kidney?
space around the hilarity structures filled with loose connective tissue
Describe the Cortex of the kidney.
- granular in appearance
- Consists most of the components of the nephron
- Extends between the medullary pyramids as renal columns ( columns of Bertin)
Describe the medulla of the kidney.
- arranged as pyramids
- apical portion of pyramid ( renal papilla) projects into minor calyx
- striated appearance-consists of straight portions of tubules and straight blood vessels
what is the functional unit of the kidney? what are its components
the nephron
- renal corpuscle: glomerulus, Bowman’s capsule
- Tubules:
- –Proximal convoluted tubule
- —LOOP OF HENLE
- proximal straight tubule
- thin descending and ascending limb, distal straight tubule
- —- distal convoluted tubule
what is the Nephron + connecting tubule called?
urinifernous tubule
What does the Renal lobe consist of ?
medulla and associated cortex
what are the two regions of the cortex of the renal lobule?
PIC
- medullary ray ( pars recta)/ straight tubules
2. Cortical labyrinth ( Pars convoluta)/ renal corpuscles and convoluted tubules
describe the placement of the parts of the renal lobule
PIC
SLIDE 11
- medullary ray in the middle with areas of cortical labyrinth on either side
- Consists of a collecting duct and the nephrons it drains
- bounded by interlobular arteries
what are the straight tubules found in the medulla?
proximal straight tubules (juxta medullary nephron)
thin loop of henle ( juxta medullary nephron)
distal straight tubule ( juxta medullary nephron)
collecting ducts
vasa recta
what is the main blood supply of the kidneys?
the renal artery then divisional branches then interlobular arteries
what arteries demarcate the cortico-medullary junction?
arcuate artery
what do the interlobular arteries arise from and what do they supply?
arcuate and supply the renal lobules.
_______ arterioles arise from interlobular arteries and form the glomerular capsule
afferent arterioles
Capillaries leave the corpuscle as _________
efferent arterioles
Cortical nephrons: efferent arterioles forms _______ capillary network
peritubular
Juxtamedullary nephrons: efferent arterioles become ________
vasa recta
what occurs at the vasa recta?
( arteriole and venulae rectae)
- countercurrent exchange of ionsin the medulla
- runs parallel to loops of Henle
What are the three types of nephrons?
cortical: short loops of Henle ( hairpin turn by distal straight)
Intermediate:mid cortical
Juxtamedullary: long loops of Henle, these are crucial for concentrating urine
what are the components of the Nephron’s Renal corpuscle?
Glomerulus
Bowman’s capsule
Mesangium
At the Glomerulus the afferent arteriole and efferent arteriole are found at the ______.
vascular pole
The bowman’s capsule surrounds the ________.
glomerulus
the mensangium has mesangial cells found _______
Look at pic
intraglomerularly
Ultrafiltrate collects in urinary space
( bowman’s space/capsular space)
and is directed to the _____ at the _______
Proximal convoluted tubule
urinary pole
The visceral layer of the Bowman’s capsule is made up of _______
podocytes
- modified squamous cells
- invests globular capillaries
The parietal layer of the Bowman’s capsule is the ____ layer. What is the epithelium? what is it contnuous with?
outer
simple squamous epithelium
continuous with proximal convoluted tubule
Filitration occurs at bowman’s capsule occurs across the filtration barrier, such as _________ and _________.
capillary endothelium
podocytes
Describe the visceral layer of the bowman’s capsule
PIC slide 21
-modified epithelial cells called podocytes, highly ramified.
-primary processes> secondary processes> pedicels
-Filtration slits between pedicels
- 40 nm wide
covered by slit diaphragm
Describe the slit diaphragm at the kidney glomerular filtration barrier
PIC
zipper- like thin sheet with a dense center counting nephrin ( transmembrane protein)
- anchored to actin filaments within pedicels of podocytes
describe endothelium of glomerular capillaries at Kidney glomerular filtration barrier
PIc slide 23
- numerous fenestrations
- no diaphragms
- produces nitric oxide and prostaglandins (PGE2)
- Abundant aquaporin-1 receptors
describe glomerular basement membrane (GBM) at Kidney glomerular filtration barrier?
- it is thick
- fused basal lamina of endothelial cells and podocyte
what molecular structures can you find at the Glomerular basement membrane?
Type 4 collagen
Heparan sulphate
what is the structural arrangement of the GBM? Glomerular basement membrane
I: lamina rara intern of capillary
II Lamina densa: type 4 collagen/ physical barrier
III: Lamina rara externa: ( of the podocytes) rish in heparan sulphate to repel negatively charged molecules
What are factors that can affect filtration at the glomerular filtration barrier?
- Charge: negatively charged molecules are repelled
- size: >70,000 Da molecular weight/ substance like albumin cannot pass through
- shape > 3.6 nm radium; ex blood cells cannot pass through
what is goodPasture’s syndrome?
IGG against type 4 collagen collagen of basement membrane> glomerulonephritis
- hematuria, proteinuria
affects lungs, bloody sputum, coughing
What re the components of the renal corpuscle’s mesangium?
mesangial cells ( contain actin filaments)
what are the two types of mesangial cells ?
1-at vascular pole
2-within corpuscle enclosed by GBM
what are the function of mesangial cells?
-phagocytosis of residue along the GBM
structural support- secretes ECM
-Secretion of inflammatory substances
interleukin-1, prostaglandin E2, PDGF
- contractile cells
regulate glomerular distension in high blood pressure
- response to angiotensin II and atrial natriuritic factor ANF
what the purpose of renal tubules?
Reabsorption, secretion, reduces urine volume, creates hyperosmotic fluid
What are the features of the proximal convoluted tubule? what epitheliumm?
- predominant tubular profile in cortex
- simple cuboidal epithelium for absorption
- large cells; large spaces between adjacent cellular nuclei
what are the functions of the proximal convoluted tubule?
- receive the ultra filtrate from the urinary space and reabsorbs 65% of it ( 100% glucose 97% amino acids)
- some protein and large peptides are returned to the blood via endocytosis
what can you find at the apical border of the proximal convoluted tubule?
microvilli which forms the brush border
what can you find at the lateral border of the proximal convoluted tubule?
- tight junctions and zonula adherins,
- Plicae= folds with interdigitate with adjacent cellular processes
- basal interdigitation
- basal striations associated with elongated mitochondria
Where are the sodium postasium pumps located on the proximal convoluted tubule?
lateral folds, they create osmotic gradient for water reabsorption,
what is the endocytic complex at the proximal convoluted tubule?
apical tubular pits between microvilli, endocytic vesicles, endoscopes, and lysosomes=== protein absorption and recycling
proximal convoluted tubules: glycocalyx
PIC
contains enzymes for absorption of glucose, peptides___ stain with PAS
extensive brush border.
