Histology Of The Renal System

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Macroscopic Kidney

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MICROANATOMY OF THE KIDNEY

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CAPSULE = connective tissue cover
CORTEX = outer region
filtration apparatus, tubules, vessels
MEDULLA = inner region
Tubules, capillary network
RENAL PELVIS = expanded origin of Ureter
RENAL SINUS = connective & adipose tissue
Plus the renal pelvis & major calyces

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Renal Corpuscle

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In the kidney, a renal corpuscle is the initial blood-filtering component of a nephron. It consists of two structures: a glomerulus and a Bowman's capsule.

spherical
200 μm diameter
Renal Corpuscle consists of:
Glomerulus = capillary loops
Bowman’s Capsule = double-layered epithelial cup
Urinary Space = Bowman’s Space

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Bowman’s Capsule

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Bowman’s Capsule has 2 parts:
1. Parietal layer
simple squamous epithelium
2. Visceral layer
Podocyte cells

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TUBULES Proximal & Distal Convoluted Tubules

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simple cuboidal epithelium
located between renal corpuscles

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Medullary Rays

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not in medulla (in cortex) name of paralellel tubules

Straight tubules (Loop of Henle)
Collecting tubules
Lined with a simple cuboidal epithelium
Run parallel with each other

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PARTS OF THE NEPHRON

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Front 8

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- elongated cells are the macula densa cells in the distal tubules
- endothelial cells (fenestrated)

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FILTRATION APPARATUS
located in the renal corpuscle

the layers ultrafiltrate travels through

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1. glomerular capillaries
fenestrated (90nm diameter) - i.e nothing larger than 70KDa
diaphragm is absent

2. glomerular basement membrane
350nm (the podcytes add thickness)
double as thick than normal

3. Visceral layer of Bowman’s Capsule
Podocyte cells
extend cytoplasmic processes around capillaries
Pedicels or Foot Processes

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FILTRATION APPARATUS
high power EM

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the podcytes foot processes look like they arent attached but they really are

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the 3 barriers

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thus 3 barriers.
1. endothial fenestration
2. ionic membrane (and basement membrane)
3. squeeze through foot processes

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PODOCYTE

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JUXTAGLOMERULAR APPARATUS

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located in the renal corpuscle 1. macula densa cells 2. Juxtaglomerular cells
3.Extraglomerular mesangial cells Endocrine function Regulates blood volume & composition Via renin-angiotensin-aldosterone system (RAS) Regulates blood pressure

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EXTRAMESANGIAL

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phagocytic
ght-staining cells in the kidney found outside the glomerulus, near the vascular pole and macula densa

? Function secrete;
Erythropoietin
IL-1
PDGF

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Macula densa cells

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Located in wall of distal convoluted tubule
Tall, narrow cells, nuclei appear crowded
Low [Na+] in distal tubule
Macula densa release prostaglandins
Paracrine affect on juxtaglomerular cells

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Juxtaglomerular cells

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•modified smooth muscle cells of afferent arteriole
•spherical nuclei, cytoplasmic granules contain renin
Endocrine function renin released into bloodstream

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Proximal convoluted tubules

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= initial & major site of reabsorption
cuboidal epithelial cell lining
Specific modifications For absorption function
1. Microvilli on apical surface
2. Junctional complex on lateral surface
3. Plicae on lateral surface
4. Basal striations
5. numerous mitochondria in basal region

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Why basal Striations?

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to INC. SA
- because we have abs. and secrition across oth membranes

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Distal convoluted tubules

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Is only 1/3 as long as the proximal
cuboidal epithelial cell lining

Specific modifications For absorption function
1. few, short Microvilli (most reabsorption already occured)
2. Junctional complex on lateral surface
3. Plicae on lateral surface
4. Basal striations
5. numerous mitochondria in basal region

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CONVOLUTED TUBULES
DDx Proximal vs Distal

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the microvilli gives it a funny appearance

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COLLECTING DUCTS

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Simple squamous or
cuboidal epithelium

wider lumenal diameter

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Parenchyma (Interstitial tissue) of the Kidney

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Connective tissue surrounding the nephrons,
ducts and blood vessels
Fibroblasts, collagen and myofibroblasts

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URINARY BLADDER

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URINARY BLADDER - MUCOSA

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epithium + loose connective tissue = mucosa

stratified (not all cells reach the BM)

can strect out and become flatten squanmous cells (from dome cells)

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Ureter

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DDx between an advential layer vs serosa

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ADVENTITIA: not exposed to the cavity and so atttached to other regions

SEROSA: lines a free surface (like pericardium... ) as opposed to adeventia