Lectr Heart and Blood Vessels Mt

8/12/2019 Lectr Heart and Blood Vessels Mt

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HEART AND BLOOD

VESSELS

Maya Tejasari

HISTOLOGY DEPARTMENT

BANDUNG ISLAMIC UNIVERSITY


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I. GENERAL FEATURES

Circulatory system

A. General Function

Transport and homeostatic distribution of

oxygen, nutrients, wastes, body fluids

and solutes and immune system

component.


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B. The two systems

1. The cardiovascular system

Closed system

Pump

Four components : heart, arteries,

veins, capillary

Blood vessels contribute to homeostasis by providing

the structures for the blood flow to and from the heart,

and the exchange of nutrients and wastes in tissues.

They also play important role in adjusting the velocity

and volume of blood flow


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2. The lymphatic vascular system

Moves only one direction

Lacks separate pump

Three types :

Lymphatic capillaries

Lymphatic vessels

Lymphatic ducts


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C. Walls of the blood and lymphatic

vessels

1. Tunica intimae

Innermost layer

Endothelium and subendothelial layer

Internal elastic lamina (artery)

2. Tunica media

Middle layer

Vascular smooth muscle fibers

Arteries thicker, external elasticlamina


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3. Tunica adventitia

Outermost layer

Connective tissue, Collagen and elastic fibers

In veins adventitia is the thickest layer

Vasa vasarum


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Walls of the blood vessels


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A. ARTERIES

Three types :

a. Large elastic arteries, conducting arteries

exp : Aorta, pulmonary arteries, common carotidarteries, large lumen

T. intimae

- endothelium cells

- subendothelial : elastic fibers, collagen, smooth

muscle cells.

Internal elastic lamina

II. BLOOD VESSELS

Classified according to type and size


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T. Media

- concentric fenestrated elastic lamellae- some collagen fibers and smooth muscle cells

Poorly defined external elastic lamina

T. Adventitia :

- Scattered collagen fibers

- Small elastic fibers

- Vasa vasorum

- Small lymphatic

- Nerve fibers


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ELASTIC ARTERY


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b. Medium (Muscular) arteries

Medium sized, distributing arteries

Relatively thick wall

More smooth muscle(40 layers)

Fewer elastic fiber in t.media

Example a brachialis, a mesenteric superior

T. intima

- Endothelium

- Subendothelial connective tissue

Internal elastic lamina : prominent


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T. media :

- Thick

- Circularly smooth muscle layer

- Elastic and reticular fibers

External elastic lamina

T. Adventitia

- relatively thin (smaller) than t. media

- Collagen fibers

- Elastic fibers

- Vasa vasorum


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Photomicrograph

of a section of

muscular artery

stained by

Weigerts method

for elastic

structures

Internal

Elastic

Laminamedia

Adventitia


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Muscular artery(transverse section)


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MUSCULAR ARTERY


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Arterioles / resistance vessels

10 - 100 m

T. intimae

- Endothelium

- Lack subendothelial connective tissue

- Membrane elastica interna (smaller arteriole)

T. Media : 1-5 layer, smooth muscles

T. adventitia, very thin : collagen fibers


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Metarteriole

Small branches of arteriole Precapillary sphincters

T. Intimae :

Internal elastic membrane -

T. Media : single layer smooth muscle

10 100 capillaries capillary bed


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The distal end of a metarteriole has no smooth muscle

fibers, which empties into a venule, is called thoroughfare

channel

Blood flows intermittently through a capillary bed due

to alternating contraction and relaxation of the smooth

muscle of metarterioles and the precapillary sphincters

is called vasomotion


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Simplified schematic diagram of the vessels of the blood vascular system.

Schematic cross sections of the various types of vessels are also shown.

Compare the relative thickness of the 3 tunics in the cross-sections : intima

(white, media (heavy stipple) and adventitia (light stipple).

Capillary bed

Muscularartery

Arteriole Metarteriole


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1. Venules :

T. Intimae, endothelium

T. Media and adventitia very thin Contractile Pericytes

2. Small and medium sized

V. saphena, hepatic portal

T. Intimae : endothelium + subendothellial

connective tissue, valves +

Internal elastic membrane -

T. Media :

- thin smooth muscle cells and elastic fibers

T. adventitia, relatively thick


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3. Large Vein

e.g. superior and inferior venaecavae

T. Intimae :

- Endothelium and subendothelial connective tissue- Valve + (2 semilunar folds of the tunica intima that

project into the lumen)

T. Media : smooth muscle, reticular fibers, collagen, elastic

fibers

T. Adventitia :

- Thickest

- Prominent bundles of smooth muscle + collagen fibers

- Vasa vasorum


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WALL OF LARGE VEIN


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Simplified schematic diagram of the vessels of the blood vascular system.

Schematic cross sections of the various types of vessels are also shown.

Compare the relative thickness of the 3 tunics in the cross-sections : intima

(white, media (heavy stipple) and adventitia (light stipple).

Capillary bed

Muscularartery

Arteriole Metarteriole


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C. BLOOD CAPILLARIES

79 m

Single layer endothelial cells with bulging nuclei

Basal lamina

Contractile Pericytes/mesenchymall cell

At the junction of a capillary, there is a ring of

smooth muscle (precapillary sphincter)


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Capillaries

E : Endothelial cells

P : Pericytes


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TYPES OF CAPILLARIES

a. Continuous capillaries

Smooth nonporous

Junctional complexes

Muscles, the brain and peripheral nerves

b. Fenestrated capillaries

Fenestrae : +

Two types : - unobstructed pores

- Pores + , thin diaphragm

Kidneys : intestines, endocrine glands


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c. Sinusoidal capillaries (discontinuous)

Wide lumens

Follow a tortuous path

Gaps between endothelial cells

Fenestration ++

Phagocytic cells

Discontinuous basal lamina

Liver, spleen, bone marrow


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2a

1

b

3Fenestrated

Continuous

Discontinuous


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Capillaries are known as exchangevessels

The flow of blood from arterioles tovenules through capillaries is calledmicrocirculation (< 0.1 mm)


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CONNECTIONS BETWEEN SMALL ARTERIES AND VEINS

1. Capillaries

2. Arteriovenous anastomoses

3. Glomus

4. Portal system


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A. Chambers

Two atria Two ventricles

B. Tunics, walls of the heart

1. Endocardium

Endothelium

Subendothelial connective tissue

Subendocardium Purkinje fibers

2. Myocardium: cardiac muscles3. Epicardium

Visceral pericardiumSingle layer squamous

Subepicardial con. Tissuevessels, nerves,

adipose

III. HEART


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HEART


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CARDIAC MUSCLE&PURKINJE

FIBERS


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Cardiac valve

The cardiac valvescentralcore of dense fibrous connectivetissue (containing both collagenand elastic fibers), lined on both

sides by endothelial layers.

The bases of the valves areattached to the annuli fibrosi ofthe fibrous skeleton.

Th d ti t


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The conducting system

Sinoatrial node (pacemaker node)

Modified cardiac muscle cells that fusiform, smaller than atrial

muscle cells, and has fewer myofibrils

Atrioventicular (AV) node

modified cardiac muscle cells that fusiform, smaller than atrial

muscle cells, and has fewer myofibrils. Their cytoplasmic

projections branch in various directions, forming a network.

Atrioventicular (AV) bundle (of his) : bundle ofspecialized conducting cardiac fibers, located in theinterventricular septum

Purkinje fibersModified cardiac muscle cells, have one or two central nuclei,and their cytoplasm is rich in mitochondria and glucogen. aftertraveling in the subendocardic layer, they penetrate theventricle and become intramyocardic.


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Superior vena cava

Sinoatrial node

Atrioventricular node

Bundle of His

Right bundle branch

Purkinje system

Posterior fascicle

Anterior fascicle

Left bundle branch

Aorta

Diagram of the heart, showing the impulse-

generating and conducting system


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Blood supply

Coronary artery

Lymphatic supply

Lymphatic capillaries in myocardium

Innervations

Myelinated and unmyelinatedautonomic motor fiber

Sympathetic increases heart rate

Parasympathetic decreases


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Lectr Heart and Blood Vessels Mt

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