Histology of the kidney Dóra Dávid - PowerPoint Presentation

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Histology of the kidney

Dóra Dávid

Assistant lecturer

2018.

a

pril

Parenchyme of the kidney

cortex

medulla

Medullary ray

Cortical labyrinth

Microscopic structure

Renal

corpuscle (

corpusculum renale Malpighi) + non-branching renal tubule (tubulus renalis). Number of nephrons by kidneys: 1,4 millionRenal corpuscle:

glomerulus (around 30 capillary loop), sorrounded by Bowman’s capsule. Function: ultrafiltration of blood, result is the primary urine (filtrate).

Parts of the renal tubule:Proximal tubule

(convoluted and straight)Tubulus intermedius (thin segment, with a loop),

 Loop of HenleDistal tubule (convoluted and straight

)Ductus reuniens

Different segments of the renal tubule modify the composition of the primary urine: 99% of water is reabsorbed, just like many useful molecules (glucose and amino acids) and ions, active secretion, adjustment of urine PH

Sammelrohr

Tubulus

proximalis

Renal corpuscle

Tubulus

distalis

Tubulus

intermedius

Ductus

reuniens

Collecting duct

kéreg

Outer cortex

Collecting duct:

long straight duct, collecting 10-20 nephrons’ urine. The final enlarged segment is called papillary duct ending at the renal papillae, leading the urine to the calyxes.

Inner cortex

Outer zone

Inner zone

p.convoluta

p.

recta

p.

convoluta

p.

recta

Loop of Henle

: proximal tubule straight part (pars recta) + tubulus intermedius + distal tubule straight part (pars recta)Alternative: „descending and ascending limb” /thin and thick segment/

Structural and functional unit: nephron

-Proximal convoluted tubule -

Proximal

tubule

- Proximal tubule straight part –

Thick descending limb-Loop of Henle

– Thin segments-

Distal tubule straight part –

Thick ascending limb- Distal convoluted tubule

– Distal tubule

Alternative nomenclatures

Histology vs. Physiology

Renal corpuscle (Malpighi)

Bowman’s capsule:

Parietal layer: squamous epithelium with basement membrane; visceral layer: podocytes

2.

Glomerulus: Capillary web with 30 loops, afferent arteriole and efferent arteriole

Vascular pole

(vas afferens and efferens),

urinary poleMesangium

Urinary pole

Parietal layer of Bowman’s

Distal tubule

.

Mesangial cellBowman’s space

Funkció:

A vér ultraszűrése

: (elsődleges vizelet)

Macula

densa

Bowman’s capsule

Inside of capsule

after Kriz

and Sakai

Structure of glomerolus

Fenestrated endothelium,

(anionic glycocalyx on cell surfaces)

Lamina

basalis

Capillaries:

Podocytes:

Mesangial cell

Fenestrated endothelium

pedicles

Visceral layer of Bowman’s capsule, branching epithelial cells with processes (pedicles). They cover the basement membrane of capillaries from the outside, on wich they „stand with small feet”. Between the feet filtration slits.

Mesangium

:

Mesangial cells in an ECM. Contractile cells, anchored to capillary basement membrane and podocytes. Regulation of capillary lumen diameter by their contractility

Lumen

Podocyte

Endothel

*

Glomerular filter

Filtration slit

Components:

Middle part of basement membrane (lamina densa)

. Dense web of collagen IV.

2. Electrostatically active glykokalyx with negative charge

on the endothelium and podocyte pedicles (

podocalyxin (glycolipoprotein), 400 nm thick layer).3. Filtration slits between interdigitating podocyte pedicles, connected with zonula adherenses. Presence of cadherins (nephrin

and neph1)

Function:Filtratory apparatus: The pores are permeable until 70 kDa, no bigger molecules can pass. The glomerular filter is just minimally permeable to the most abundant plasma protein, the albumin

.

Endothelium

Podocyta feet

Proximal tubule

Morphology:

Brush border

(enlarging apical surface!),

Pinocytotic vesicules at the origin of microvili, endocytosis!

Lysosomes

Mitochondria (perpendicularly to the basal surface of cells) „basal striation” in light microscope.

Basale labyrinth: Neighbouring cells interdigitate with each other with their basale plasma membrane.

The luminal surface of the tubules is irregular, arcadic.

Function:Reabsorbtion of useful molecules: glucose, amino acids, ions water. Proteins accidentaly passing through the glomerolus filtration membrane are reuptaken by endocytosis with megalin

receptorsTubular maximum: maximum reabsorption capacity for specific molecules  glucose: 10mmol/l  diabetic glucosuria

Proximal tubule in light miscroscope

Proximal tubules

(

pars

convoluta)

Distal tubules (pars convoluta)

Cortical labyrinth (HE)

Brush border

lysosomecapillary

Proximal tubule cross section semithin toluidin blue

Luminal surface is arcadic, vague and irregular

Tubulus intermedius (thin segment)

Microscopic morphology:

Squamous epithelium, lack of cell organelles.

Function:

Water reabsorption in the descending limb (aquaporin channel type I), NaCl reabsorption in the ascending limb, that is not permeable to water

Distal tubule

Microscopic morphology:

Well developed basale labyrinth

Mitochondria

NO brush border or pinocytotic vesiclesLuminal cell surface is smooth and distinct from the lumen.

Function Cl- reabsorption without water reabsorption

Macula

densa: Part of the distal tubule at the junction between the convoluted and straight part fits to the angle between the afferent and efferent arteriole. Cell nuclei of epithelial cells are more closely arranged, the area shows stronger staining. Part of the juxtaglomerular apparatus.

Macula

densa

Tubulus reuniens and collecting duct

Main cells:

Lighter staining of cuboidal epithelial cells with many tight junctions

Function: concentration of urine

Water reabsorption is regulated by the hormone ADH

Dark cells

Cells with darker staining between main cells with many mitochondriaFunction: H+

pumping into the urine (H+ATPase, H+K+ ATPase).

Acid-base balance: regulating the PH of urine and body fluids  regulated by the hormone aldosterone

Blood supply

Two seperated capillary system in the cortex

Interlobular artery (a. corticalis radiata) → afferent arteriole

→

glomerule capillaries → efferent arteriole→ peritubular capillary system

(reabsorbed molecules and water is recirculated to the venous system here) → interlobular vein (v. corticalis radiata

)Vasa recta in the medulla:

Close contact with the thin and thick segment  countercurrent exchanger  concentration of urine

vesetok

Renale lobule (lobulus renalis)

From outside to inside

Interlobular arteries with Malpighian bodies



convoluted tubules of nephrons



straight tubules  collecting ducts in the middle

Straight tubules (cross sections)

Renale corpuscles

Convoluted tubules

Juxtaglomerular apparatus (JGA)

Components

macula densa

: Perception of Cl- concentration in the urine, osmoreceptor

extraglomerular mesangial cells

: Signal transduction to renin secreting JGCsJuxtaglomerular cells (JGCs)

: Renin production

Function of JGA:1.

Tubulo-glomerular feedback: osmoreception in distal tubules  signal transduction to JGCs  smooth muscle contraction/relaxation of afferent/efferent arterioles (high Cl

- concentration  decreasing blood flow by smooth muscle contraction).

2. Systematic effect: Increase in blood pressure due to the activation of renin-angiotensin-aldosterone system

.

Extraglomerular mesangium

Juxtaglomerular cell (JGC)

Smooth muscle

Mesangial cell

Distal tubule

Kriz

és

Sakai

után

dp

Calyx

minor

area

cribrosa

Outer

medulla:

Proximal

straight tubuleDistal straight tubule

Collecting ductcapillaries

Middle medulla:

Distal straight tubuleCollecting duct Loop of Henle

Capillaries

Inner medulla:Collecting duct

Loop of HenleCapillaries

CortexProximal

convoluted tubuleDistal convoluted tubule

CapillariesGlomeruli(Collecting ducts)

Source of imagesRöhlich Pál: Histology (Hungarian), Semmelweis

Kiadó, Budapest,

4th edition,

2014And:

*

Ross, Kaye, Pawlina:

Histology, 2003Thank you for your attention!