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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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