HISTOLOGY OF CVS

PROF. DR. FAUZIAH OTHMAN

DEPT OF HUMAN ANATOMY

CONTENT

Histological features of cardiac muscles,

epicardium, endocardium,

Histological features of the Purkinje fibres.

Histological features of the elastic artery,

muscular artery and arteriole

Histological features of the large and medium

vein, venule.

Histological features of capillaries.

Cardiac muscle

Striated

Involuntary

single, centrally placed nucleus

COVERING OF THE HEART

Pericardium

The membrane surrounds to protects heart.

Consist 2 principal portions: • fibrous pericardium

• Serous pericardium

Fibrous Pericardium Serous pericardium

•Superficial

•Tough

•Inelastic

•Dense irregular connective tissue

Fx: prevent overstretching of

heart, provide protection & anchor

of the heart to mediastinum.

•Deeper

•Thinner

•More delicate membrane that

form double layer round the heart

•Outer parietal of serous

pericardium –fused to fibrous

pericardium

Visceral layer of serous

pericardium--epicardium

HEART WALL

Heart comprises of three layers;

1. Epicardium( external layer)

2. Myocardium ( middle layer)

3. Endocardium (inner layer)

Epicardium (epi= on top of)

Visceral layer of the serous pericardium

Thin, transparent outer layer of the wall

Composed mesothelium & CT

Myocardium (myo = muscle)

Composed cardiac muscle tissue

Responsible for pumping action.

Stratified, involuntary & intercalating bundles

Endocardium (endo= within)

thin layer of endometrium

Smooth muscle

The outmost layer is composed of irregularly

arranged collagen fibres that merge with collagen

surrounding adjacent cardiac muscle fibres. This

layer may contain some Purkinje fibres, which are

part of the impulse conducting system .

PURKINJE FIBERS (OR PURKYNE TISSUE)

are located in the inner ventricular walls of the

heart, just beneath the endocardium. These

fibers are specialized myocardial fibers that

conduct an electrical stimulus or impulse that

enables the heart to contract in a coordinated

fashion.

PURKINJE FIBERS

SPECIALIZED CARDIAC MUSCLE FIBERS

Heart: contracting cardiac muscle fibers and impulse-conducting

Purkinje fibers. Stain: Mallory-azan

5 MAIN TYPES OF BLOOD VESSELS

1. Arteries (ar= air; ter= to carry)

2. Arterioles

3. Capillaries

4. Venules

5. Veins

TYPE OF ARTERIES

There are 3 types of arteries Elastic arteries

Muscular arteries

Arterioles

The luminal diameter of artery gradually

decrease with each branching.

ARTERY

Wall have 3 tunics: Tunica interna (intima)

Tunica media

Tunica externa

Tunica interna (intima) composed simple squamous epithelium (endothelium)

& layer elastic tissue (internal elastic lamina)

Closest to lumen

Tunica media

Thickest layer

Elastic fiber & smooth muscle fibers arranged in ring

around lumen

Tunica Externa

Composed principally of elastic & collagen fibers

Elastic arteries/ conducting

arteries

Muscular arteries/ distributing

arteries

Largest blood vessel in the body

Larger-diameter

Tunica media contain high

proportion of elastic fiber

Eg: aorta & pulmonary trunk

Most numerous vessels in the

body.

Medium size

Tunica media contain high

proportion of smooth muscle fiber

Eg: brachial artery or popliteal

artery

ARTERIOLE (= SMALL ARTERY)

The smallest branches of arterial system.

The wall of arteriole consist of one to five layers

of smooth muscle fibers.

Arteriole deliver blood to the capillaries, which

are microscopic blood vessels that connect

arteriole with the venules.

DIFERRENCES BETWEEN ARTERY & VEIN

Artery Vein

•Thick and elastic muscular walls

•No valves

•carriers of oxygenated blood

(exception: pulmonary arteries

which carry de-oxygenated blood

from the heart to the lungs).

•Thin and slightly muscular walls.

•internal valves (to prevent back

flow of blood)

•veins carry de-oxygenated blood

(exception: pulmonary veins which

carry oxygenated blood from the

lungs to the heart)

Artery and vein in connective tissue of the vas deferens. Stain: iron

hematoxylin and alcian blue

Muscular artery and vein (transverse section). Stain: elastic stain

Blood and Lymphatic vessels stain with H&E

Wall of large vein: portal vein(tranverse section). Stain:H&E

Heart: right ventricle, pulmonary trunk, and pulmonary valve. Stain:

H&E

CAPILLARIES

Microscopic vessel that connect arteriole to

venule.

Capillary wall composed of ONLY a single layer

of endothelial cell & a basement membrane.

NO tunica media & NO tunica externa

Perculiar- protuding nucleus in the lumen.

Type of

Capillaries.

Continuous Fenestrated Discontinuous/

Sinusoidal

Plasma membrane of

endothelial cells form

are continuous tube

Found in skeletal

muscle, central nervous

system, skin, gonads,

connective tissue and

lungs

Plasma membrane of

endothelial cells have

many small pores,

ranging from 70-100nm

in diameter

Found in

endocrine glands,

intestines, pancreas

and glomeruli of kidney

Wider & more winding

than other capillaries

Large pores

Primarily located in the

liver, spleen, bone

marrow, lymph nodes,

and adrenal cortex.

VASA VASORUM

network of small blood vessels that supply large

blood vessels.

This is because:

The wall of larger arteries and vein are too thick to

receives nourishment direct diffusion from their

lumina .

VENULES

Several capillaries form small vein

The smallest venules, those closest to the

capillaries, consist of a tunica interna of

endothelium & tunica media that has only a few

scattered smooth muscle fiber & fibroblast.

VEINS

Same as tunica in arteries BUT different in

thickness.

Tunica interna more thinner (little SM & elastic

fiber)

Tunica externa of veins is thickest layer (collagen

& elastic fibers)

Vena cava- longitudinal fiber of smooth muscle.

Veins LACK external or internal elastic lamina

found in arteries

CLINICAL CORRELATION

Congestive heart failure occurs when the heart is unable to adequately pump blood. Because of this the body's tissues don't receive enough blood to function properly. Congestive heart failure can be a devastating disease for both dogs and cats, striking primarily older and obese animals