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MIS 264SESSION 1
HISTOLOGY OF THE
CARDIOVASCULAR SYSTEM
2013
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THE VASCULAR SYSTEM
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GENERAL STRUCTURE OF
BLOOD VESSELS
Tunics of the blood vessel wall:
Tunica intima
Tunica media
Tunica adventitia
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BLOOD VESSEL WALLTunica Intima
Endothelial layer
Basal lamina
Subendothelium
Loose connective tissue
Smooth muscle cells
Internal elastic lamina
(Arteries)
Venous valves
(endoteel + bl+
Subendothelium)
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Smooth muscle tissue
Connective tissue (elastic-, reticular-
collagen- fibres) Ground substance
External elastic lamina (larger arteries)
Concentric layers
170 layers
BLOOD VESSEL WALLTunica Media
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Connective tissue Loose- to dense connective tissue
(collagen type I fibres and elastic fibres)
Ground substance
Connective tissue fuse with surrounding connectivetissue
Vasa vasorum
Nervi vascularis
BLOOD VESSEL WALLTunica Adventitia
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GENERAL STRUCTURE OF ARTERIES
AND VEINS
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SPECIFIC HISTOLOGICAL STRUCTURE
OF BLOOD VESSELS
Capillaries
Arteries
Veins
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CAPILLARIES
General structure
COMPOSED OF:
Single layer of endothelial cells, resting on a
Basal lamina
Pericytes are genrally found on the outer surface
of capillares en venules, enclosed in the basal
lamina of the capillaries endothelial cells
Pericytes are able to contract and differentiate
into endothelial cells, smooth muscle cells and
fibroblasts; during repair and growth of
capillaries
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CONTINUOUS CAPILLARIES
FENESTRATED CAPILLARIES WITH A
DIAPHRAGM
FENESTRATED CAPILLARIES WITHOUT
A DIAPHRAGM
SINUSOIDS
TYPES OF CAPILLARIES
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Endothelium:
Continuousno openings between adjacent cells - limitsthe movement of substances between cells
No fenestrae in the capillary wall
Large number of pinocytotic vesicles* (70 nm) present,
responsible for the transport of macro-molecules across the
endothelial cell layer
Basal lamina: Continuous basal lamina
Regulate movement of substances across this lamina
CONTINUOUS CAPILLARIES
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Occurrence:
Muscle tissue, lung, most connective tissues, exocrineglands and nervous tissue
Remarks:
Pinocytotic vesicles is absent or limited in the capillariesof the Central Nervous System (Blood brain barrier)
limited and regulated transport of macro-molecules across
the endothelium
Pericytes may be present
CONTINUOUS CAPILLARIES (cont.)
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CONTINUOUS CAPILLARIES
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CONTINUOUS CAPILLARIES
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Remarks: It is encountered in tissues where rapid interchange of
larger molecular substances occurs between the tissues and
the blood and/or fluid absorption
Endothelium: Large fenestrae (80100 nm) present in the endothelial
wall - fenestrae covered with a diaphragmregulated
transport of larger molecules
Pinocytotic vesiclestransport of macro-molecules across
the endothelial layer
Basal lamina: Continuous basal lamina
Regulate movement of substances across this lamina
FENESTRATED CAPILLARIES WITH A
DIAPHRAGM
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Occurrance: It is encountered in tissues where rapid interchange of
larger molecular substances occurs between
the tissues and the blood and/or fluid absorption
Peritubular network and vasa recta of the kidney, smallintestine, endocrine glands and gall bladder
Remarks:
Fenestrae (80100 nm) creates channels across the fullthickness of the edothelial layer
Diaphragm regulates the transport of substances
The number of fenestrae and pinocytotic vesicles correlate
with the functional activity across the capillary wall
FENESTRATED CAPILLARIES WITH A
DIAPHRAGM
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FENESTRATED CAPILLARIES WITH A
DIAPHRAGM
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Remarks: Renal glomeruluscontribute to the urinary filtration
barrier
Endothelium: Large fenestrae (80100 nm) present in the endothelial
wall - NO diaphragmtransport of larger molecules
Pinocytotic vesiclestransport of macro-molecules across
the endothelial layer
Basal lamina: Thickend continuous basal lamina
Increased regulation of movement of substances across this
lamina
FENESTRATED CAPILLARIES
WITHOUT A DIAPHRAGM
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Occurrance: Renal glomeruluscontribute to the urinary filtration
barrier
Remarks: Fenestrae (80100 nm) creates channels across the full
thickness of the edothelial layer
Urinary filtration barrier consists of capillary endothelium,
fused basal laminas of the endothelial cells and Podocytes,
and pedicels of Podocytes. The filtration slits between the
pedicels of podocytes are covered b a diaphragm
FENESTRATED CAPILLARIES
WITHOUT A DIAPHRAGM (cont.)
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Remarks:
Lumen has a large diameter, which slow the circulation ofblood
Endothelium: Discontinuousgaps between cellslarge-molecular
substances can cross
Large fenestrae (80100 nm) present in the endothelial
wall - NO diaphragmtransport of larger molecules
Basal lamina: Discontinuous or absenteasy movement substances
SINUSOIDS
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Occurrence:
Liver, spleen and bone marrow
Remarks: Lumen has a large diameter, which slow the circulation of
blood Irregular shapevaries between organs and specialised in
different organs
SINUSOIDS (cont.)
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Regulate blood flow and blood pressure
Arteries are classified based on their size:
Elastic arteries
Aorta, pulmonary a, Renal a, Brachiocephalica, Common carotid a, Subclavian a, andCommon iliac a.
Muscular arteries
Most arteries with names
Arterioles
ARTERIES
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Aorta, pulmonary a, Renal a, Brachiocephalic a,Common carotid a, Subclavian a, and Common iliac a.
Regulate blood flow and blood pressure
ELASTIC ARTERIES
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ELASTIC ARTERIESTunica Intima
Endothelial layer Continuous and with adhesions between cells
Basal lamina
Sub endothelium
Loose connective tissue with collagen and elastic fibres
Smooth muscle cells
Internal elastic lamina
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Smooth muscle tissue
Fenestrated elastic laminae Diffusion of substances
Blood pressure, blood flow,and secondary pump
Connective tissue (elastic-, collagen- fibres
and fibrils)
Ground substance
External elastic lamina
Concentric layers
4070 layers
BLOOD VESSEL WALLTunica Media
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Connective tissue Relatively thin
Loose network of collagen and elastic fibres
Ground substance
Collagenlimits vascular distension
Vasa vasorum* Nutrition of blood vessel wall
Nervi vascularis Sympathetic and Parasympathetic innervations - blood
pressure
BLOOD VESSEL WALLTunica Adventitia
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ELASTIC ARTERIES
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MUSCULAR ARTERIESTunica Intima
Thinner than that of Elastic arteries
Endothelial layer
Basal lamina
Sub endothelium
Thin, Loose connective tissue Smooth muscle cells
Internal elastic lamina
PROMINENT
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Thickest layer
Smooth muscle tissue Blood pressure
Connective tissue (elastic-, collagen- fibres)
Ground substance
External elastic lamina (larger arteries)
Concentric layers 740 layers
MUSCULAR ARTERIESTunica Media
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Connective tissue Relatively thick
Loose connective tissue
Fibroblasts, adipocytes
Collagen and elastic fibres
Ground substance
Collagenlimits vascular distension
Vasa vasorum* Nutrition of blood vessel wall
Nervi vascularis Sympathetic and Parasympathetic innervations - blood
pressure
MUSCULAR ARTERIESTunica Adventitia
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MUSCULAR ARTERIES
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MUSCULAR ARTERIES
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SMALL ARTERIES AND ARTERIOLES
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Relatively small lumensdiameter less than 0.5mm.
Arterioles1-2 layers of smooth muscle
Small arteries36 layers of smooth muscle
Regulate blood flow to capillaries
Peripheral resistance Blood pressure
SMALL ARTERIES AND ARTERIOLES
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ARTERIOLESTunica Intima
Endothelial layer
Basal lamina
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Smooth muscle tissue
Connective tissue
Concentric layers
12 layers
ARTERIOLESTunica Media
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Connective tissue Thin layer
Connective tissue fuse with surrounding connective
tissue
ARTERIOLESTunica Adventitia
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ARTERIOLES
VEINS
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Return blood back to the heart aided by the
action of smooth muscle and specialisedvalves
Veins are classified as: Venules
Small veins
Medium veins Large veins
VEINS
LARGE VEINS
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Tunica adventitia is the thickest layer
Diameter larger than 10 mm
LARGE VEINS
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LARGE VEINSTunica Intima
Endothelial layer
Basal lamina
Sub endothelium
Thin loose connective tissue
Smooth muscle cells
Boundary between Tunica intima and Tunica media
NOT clear
Venous valves
(One directional flow)
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Relatively thin
Smooth muscle tissue Blood pressure
Collagen fibres
A few fibroblasts
Poorly defined
concentric layers
LARGE VEINSTunica Media
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Thickest layer
Connective tissue -prevent over-distension of vein Collagen and elastic fibres
Ground substance Fibroblasts
Smooth muscle -prevent over-distension of vein
Longitudinal bundles
Vasa vasorum
Nervi vascularis
LARGE VEINSTunica Adventitia
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LARGE VEINS
A G S
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LARGE VEINS
VENEOUS VALVES
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VENEOUS VALVES
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DIFFERENCES BETWEEN AN ARTERY
AND A VEIN
ARTERIE VEIN
-ROUNDED - OVALSHAPED
-THICK WALL - THIN WALL
-INTIMA SCALLOPED - INTIMA SMOOTH
-THREE LAYERS ARE - DIFFICULT TO
CLEARLY DISTIN- IDENTIFY THE
GUISHALBE DIFFERENT LAYERS
(T. MEDIA IS (T. ADVENTITIA
PROMINENT) IS PROMINENT)
DIFFERENCES BETWEEN AN ARTERY
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DIFFERENCES BETWEEN AN ARTERY
AND A VEIN
ARTERY Rounded
Thick wall
Intima scalloped Three layers are
Clearly distinguishable
T. Media is prominent
VEIN Ovalshaped
Thin wall
Intima smooth Difficult to identify the
different layers
T. Adventitia prominent Valves
ARTERIES AND VEINS
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ARTERIES AND VEINS
ARTERIES AND VEINS
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ARTERIES AND VEINS
ARTERIES AND VEINS
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ARTERIES AND VEINS
ARTERIES AND VEINS
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ARTERIES AND VEINS
SUPPLY OF NUTRIENTS AND GASSES TO
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Inner portion of blood vessel wall (T. Intima
and inner 1/3 of T. Media) receives nutrients
and gasses by means of diffusion from theblood vessel lumen
Distance for effective diffusion is limited.
The outer part of the blood vessel wall needs
an alternative mechanism vasa vasorum
SUPPLY OF NUTRIENTS AND GASSES TO
BLOOD VESSEL WALL AND
VASA VASORUM
VASA VASORUM
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Distance for effective diffusion is limited.
The outer part of the blood vessel wall needs
an alternative mechanism vasa vasorum
Blood supply to the outer 2 layers of the
blood vessel wall (T. Media en T. Adventitia)of large blood vessels.
The vasa vasorum penetrates the large blood
vessels from the T Adventitia side andsupply the T. Adventitia and outer 2/3 of T.
Media.
VASA VASORUM
THE HEART
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THE HEART
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THE HEART
THE WALL OF THE HEART CONSIST
OF THE FOLLOWING:
1. Cardiac muscle
2. Fibrous skeleton
3. Impuls conducting system
THE HEART
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THE HEART
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THE HEART
THE WALL OF THE HEART CONSIST
OF THE FOLLOWING LAYERS:
1. Endocardium
2. Myocardium
3. Epicardium
1 ENDOCARDIUM
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1. ENDOCARDIUM
-Endothelium
-Subendothelium
SUBENDOCARDIAL LAYER
-Purkinje fibers
-Veins
-Nerves
2 MYOCARDIUM
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2. MYOCARDIUM
- 3 layers cardiac muscle
SUBEPICARDIAL LAYER
- Loose connective tissue
- Adipose tissue- Blood vessels
- Nerves
3. EPICARDIUM
- Connective tissue
- Mesothelium
THE HEART
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THE HEART