Histology of cardiovascular system explained

1. Histology of cardiovascular systemHistology of cardiovascular system
►The cardiovascular systemThe cardiovascular system
► heart and of blood vessels.heart and of blood vessels.
arteries,arterioles, capillaries,arteries,arterioles, capillaries,
venules and veins.venules and veins.
►Arteries bring blood from heartArteries bring blood from heart
to different organs or tissues.to different organs or tissues.
►Arterioles divide to form theArterioles divide to form the
network called capillaries whichnetwork called capillaries which
pervade with tissues.pervade with tissues.
►In some organ capillaries areIn some organ capillaries are
replaced by sinusoids.replaced by sinusoids.
►The blood from capillaries orThe blood from capillaries or
sinusoids is collected in thesinusoids is collected in the
venules which unite to formvenules which unite to form
veins.veins.
►Veins bring blood to heart.Veins bring blood to heart.

2. Layers of ArteryLayers of Artery
Fig: A medium sized muscular artery
showing its layers.

3. Basic structure of ArteriesBasic structure of Arteries
1.The innermost layer, tunica1.The innermost layer, tunica
intima ( tunica=coat).it consistsintima ( tunica=coat).it consists
ofof
a. An endothelial lininga. An endothelial lining
b. A thin layer of glycoproteinb. A thin layer of glycoprotein
called basal lamina.called basal lamina.
c. A delicate layer ofc. A delicate layer of
subendothelial connectivesubendothelial connective
tissue.tissue.
d. A membrane formed by thed. A membrane formed by the
elastic fibres called theelastic fibres called the internalinternal
elastic lamina.elastic lamina.
2.The tunica media.2.The tunica media.
. Elastic tissue or smooth muscle. Elastic tissue or smooth muscle
limited outside by a membranelimited outside by a membrane
formed byformed by external elasticexternal elastic
lamina.lamina.
3. The tunica adventitia3. The tunica adventitia
consists of connective tissue inconsists of connective tissue in
which collagen fibres arewhich collagen fibres are
prominent.prominent.

4. Types of arteries:Types of arteries:
► On the basis of the kindOn the basis of the kind
of tissue predominates inof tissue predominates in
the tunica media arteriesthe tunica media arteries
divide into elastic arterydivide into elastic artery
and muscular.and muscular.
► Elastic arteriesElastic arteries ::
► The largest artery in theThe largest artery in the
body.e.g. aorta,body.e.g. aorta,
pulmonary trunk withpulmonary trunk with
subdivisionsubdivision
branchiocephalic ,branchiocephalic ,
common carotid,common carotid,
subclavian ,vertebral,subclavian ,vertebral,
pulmonary and commonpulmonary and common
iliac.iliac.
► Tunica media is made upTunica media is made up
of elastic tissueof elastic tissue
► Some smooth muscle areSome smooth muscle are
also present in the media.also present in the media.
► The subendothelial tissueThe subendothelial tissue
contains more elasticcontains more elastic
tissues.tissues.

5. ELASTIC ARTERY: AORTA

6. ►aa

8. ► Muscular Artery:Muscular Artery:
► They are theThey are the
continuation of elasticcontinuation of elastic
artery.artery.
► Predominant smoothPredominant smooth
muscles in the tunicamuscles in the tunica
media.media.
► Muscle fibres arrangedMuscle fibres arranged
circularly.circularly.
► Connective tissues areConnective tissues are
also present in betweenalso present in between
the muscle fibres.the muscle fibres.
Internal
elastic lamina
Tunica
media
Tunica adventitia

9. Muscular Artery (x4)Muscular Artery (x4)

10. Muscular Artery (L) vs Elastic ArteryMuscular Artery (L) vs Elastic Artery
(R)(R)

11. Arterioles:Arterioles:
► The muscular arteriesThe muscular arteries
having diameter lesshaving diameter less
than 100 µm are calledthan 100 µm are called
the arteriole.the arteriole.
► Muscular arterioles:Muscular arterioles:
diameter 100-50 µm .diameter 100-50 µm .
► Lack of internal elasticLack of internal elastic
lamina.lamina.
► Few layers of smoothFew layers of smooth
muscles.muscles.
► Terminal arteriole:Terminal arteriole:
diameter> 50diameter> 50 μμmm
► A thin layer of smoothA thin layer of smooth
muscles fibres in themuscles fibres in the
tunica media.tunica media.
T.S. of arterioles

12. ArterioleArteriole
Large Small

13. ►Capillaries :Capillaries :
► Terminal arterioles areTerminal arterioles are
continued into capillary plexuscontinued into capillary plexus
► The arrangement of theThe arrangement of the
capillary plexus and theircapillary plexus and their
density varies.density varies.
► In the wall of capillaries thereIn the wall of capillaries there
are the lining of endothelium.are the lining of endothelium.
► Endothelial cells are linedEndothelial cells are lined
outside by a basal laminaoutside by a basal lamina
► Overlying the basal laminaOverlying the basal lamina
there may be somethere may be some
perivascular cells( pericyte)perivascular cells( pericyte)
► Capillaries are two typesCapillaries are two types
► ContinuousContinuous :: the edges ofthe edges of
adjoining endothelial cells areadjoining endothelial cells are
fuse .e g. in muscle, skin ,fuse .e g. in muscle, skin ,
lungs,brainlungs,brain
► Fenestrated:Fenestrated: apertures areapertures are
present in endothelial cells.present in endothelial cells.
E.g. small intestine, endocrineE.g. small intestine, endocrine
glands and kidney.glands and kidney.

14. CAPILLARY
Endothelium

15. Sinusoids:Sinusoids:
These are also network- differentThese are also network- different
from the capillaries.from the capillaries.
► The wall of sinusoids containsThe wall of sinusoids contains
only the endothelial cellsonly the endothelial cells
covered by a layer ofcovered by a layer of
connective tissue.connective tissue.
► In some places the wall isIn some places the wall is
incomplete.incomplete.
► The lumen is broader butThe lumen is broader but
irregular than the capillaries.irregular than the capillaries.
► The sinusoids are found in theThe sinusoids are found in the
organ which is made up of theorgan which is made up of the
cords of cells.e.g.cords of cells.e.g.
liver,spleen ,suprarenal gland.liver,spleen ,suprarenal gland.
and pitutary glandand pitutary gland

16. Fig : sinusoids in liver

17. veinsveins
► Basic structure is same asBasic structure is same as
arteryartery
► The wall of vein is thinner.The wall of vein is thinner.
► Presence of abundantPresence of abundant
collagen fibres in mediacollagen fibres in media
layer.layer.
► The smooth muscle fibresThe smooth muscle fibres
or elastic fibres reduced .or elastic fibres reduced .
► The tunica adventitia layerThe tunica adventitia layer
is thicker.is thicker.
► Significant amount ofSignificant amount of
elastic fibres and also theelastic fibres and also the
muscle fibres in adventitia.muscle fibres in adventitia.
► There is no distinction of 3There is no distinction of 3
layers especially in smalllayers especially in small
vein.vein.
Fig: Medium sized vein. right
(verhoff’s staining for elastic
fibres the left (hematoxylin
&Eosin staining)

18. Vein x10Vein x10

21. venulesvenules
► Smallest vein which drainSmallest vein which drain
from capillaries are calledfrom capillaries are called
the venule.the venule.
► Diameter 20-30Diameter 20-30 μμm.m.
► The wall consists ofThe wall consists of
endothelial lining, basalendothelial lining, basal
lamina and a thinlamina and a thin
adventitia.adventitia.
► wall is very muchwall is very much
permeable especiallypermeable especially
lymphocytes and otherlymphocytes and other
cells may pass out intocells may pass out into
blood stream.blood stream.
Fig : T.S. of venules

22. Endothelial lining
Basal
lamina
Fig; venules

23. The heartThe heart
► Made up of 3 layersMade up of 3 layers
► Inner endocardiumInner endocardium
► A middle myocardiumA middle myocardium
► An outer epicardiumAn outer epicardium
► The endocardium: simple squmaous epitheliumThe endocardium: simple squmaous epithelium
and a thin subendothelial connective tissue.and a thin subendothelial connective tissue.
► The myocardium: thickest layer and it consists ofThe myocardium: thickest layer and it consists of
cardiac muscle fibres.cardiac muscle fibres.
► The epicardium consists of squamousThe epicardium consists of squamous
mesothelium and an underlying subepicardialmesothelium and an underlying subepicardial
layer of connective tissue.layer of connective tissue.
► The subepicaridal layer contains coronary bloodThe subepicaridal layer contains coronary blood
vessels ,nerves and adipose tissue.vessels ,nerves and adipose tissue.

26. HEARTHEART

27. ►Purkinje fibers specialized for thePurkinje fibers specialized for the
conduction of system of heart.conduction of system of heart.
►Short and larger fibers with central nucleus,Short and larger fibers with central nucleus,
cytoplasm contains more glycogen.cytoplasm contains more glycogen.

28. ..
►..

29. Atherosclerotic LesionsAtherosclerotic Lesions
►Increase in thickening of intima.Increase in thickening of intima.
►Proliferation of smooth muscle cells,Proliferation of smooth muscle cells,
increased deposition of CT fibers,increased deposition of CT fibers,
lipoproteins.lipoproteins.
►Macrophages engulf lipoproteins.Macrophages engulf lipoproteins.
►Thickening occludes vessel.Thickening occludes vessel.

30. Atherosclerotic Plaque in CoronaryAtherosclerotic Plaque in Coronary
ArteryArtery

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