Download Circulatory system 2009

Circulatory system
2009
Circulatory system
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Heart
Macrocirculation
Microcirculation
Lymphatic vessels
Heart
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Endocardium (as t. intima)
− Endothelium
− Subendothelial layer (loose connective tissue with
smooth muscle cells, elastic and collagen fibers)
− Subendocardial layer (connective tissue, veins, nerves
and conducting system of the heart)
Myocardium (Cardiomyocytes)
Epicardium (Mesothelium + connective tissue)
− Subepicardial layer adipose tissue, veins, nerves and
autonomic ganglia
Pericardium
Cardiac fibrous skeleton – septum membranaceum,
trigona fibrosa and annuli fibrosi – dense connective
tissue
Atrial cardiac muscle cells
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Production of atrial natriuretic factor (granules)
More RER and larger GA
Function – to stimulate diuresis, natriuresis
antagonist of vasopressin (ADH) and aldosteroneangiotensin II system
Prevent resorption of Na+ and water – prevent
hypervolemia
Conducting system of the heart
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Modified cardiac muscle cells - smaller than artial
cardiac muscle cells:
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Sinoatrial node (Keith-Flack)
Atrioventricular node (Aschoff-Tawar)
Purkyně fibres are thicker than cardiomyocytes,
They are rich on glycogen, positive on
acetylcholin esterase
Atrioventricular bundle of His
Left and right bundle of Tawar
Left has two branches
Purkyně fibres
Circulatory system
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Macrocirculation >
0,1mm
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Elastic arteries
Mixed and hybrid
arteries
Muscular arteries
Arterioles
Venules
Small and middle sized
veins
Large veins
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Microcirculation <
0,1mm
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Arterioles
Metharterioles
Capillares
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Continuous, somatic
Fenestrated, visceral
Fenestrated without
diaphragm
Discontinuous
-sinusoids
Venules
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Pericytic
Muscular
Elastic arteries
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INTIMA
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Endothelium
Subendothelial layer – loose connective tissue with
smooth muscle cells, macrophages
Internal elastic lamina
MEDIA
Perforated elastic membranes -membranae
elasticae fenestratae up to 60, smooth muscle cells,
collagen fibers (collagen type 3)
External elastic lamina
ADVENTITIA - dense collagen connective tissue
(collagen type 1)
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Intima – thick up to
100μm in elastic
arteries.
It comprises
glycosaminoglycans
Muscular arteries
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INTIMA
Endothelium and
basement membrane
Internal elastic lamina
MEDIA
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Smooth muscle cells circular oriented
External elastic lamina
ADVENTITIA
Dense collagen
connective tissue
Hybrid and mixed arteries
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Continue with elastic arteries
Wall turns gradually from elastic (media with
elastic membranes) into muscular (media contains
only smooth muscle cells)
Intima as thick as in elastic arteries
Media – first groups cells, than layer of smooth
muscle cells (arteria femoralis)
Other arteries – sharp border – a. renalis
Arterioles
Regulate distribution of blood in tissue – capacity of
vasoconstriction and vasodilatation
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Tunica intima – endothelium and basement
membrane
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Tunica media – 2 to 5 layers of smooth muscle cells
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Tunica adventitia – loose collagen connective tissue
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Venules
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Similar to capillary wall
Endothelium, lamina basale, pericytes
Larger- connective tissue in adventitia and later
also muscle cells
More permeable than capillaries
Specific venules within lymph nodes (high
endothelium venules) – cuboidal cells – L-selectin
– lymphocytes cross the wall and enter lymphatic
tissue - homing
Small and middle sized veins
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Intima
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Endothelium and subendothelial connective tissue
Internal elastic membrane is missing, it is present only
veins in lower limbs and v.cava inferior
Media – collagen connective tissue with circular
smooth muscle cells, external elastic membrane is
not present
Adventitia – collagen connective tissue with
longitudinal oriented smooth muscle cells
Valves are present!
VARIABILITY IN WALL STRUCTURE
Large veins
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Intima – thick layer
Media – thin or cannot be present
Very thick adventitia – longitudinal
bundles of smooth muscle cells
All cell (macrocirculation) comprise
vasa vasorum and nervi vasorum in
adventitia
Veins
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Draining veins: splenic, intracranial (sinuses), ophtalmica,
facialis, jugularis – only intima and adventitia, muscle are
absent in the wall
Propulsive veins: veins in lower extremities, mesenterica
superior, portae, renalis – very thick adventitia with many
muscle cells forming bundles + valves
Differences between arteries and veins
Arteries contain internal and external elastic membrane,
thicker media and thinner adventitia
Veins – internal elastic membrane is not often present,
media is thinner and adventitia thicker, wall is thinner,
diameter larger, valves are present
Microcirculation – structure of
capillary
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Endothelium
Lamina basale
Pericytes
Endothelium - function
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Gas exchange -diffusion
Transport- pinocytosis - calveoles
Synthesis of vasoactive substances -NO,
prostacycline, endothelin1
Control of vascular growth – produce growth
factors
Regulation of immune reactions –facilitate
leucocyte crossing through capillary wall – Eselectin, L-selectin
Activity in haemostasis – von Willebrant factor –
Weibel Palade granules in endothelial cell of
arterioles
Weibel Palade granules
Continuous-somatic capillaries
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Endothelium
Lamina basale
Pericytes
Occurrence:
Permeable: skin, lung, muscles
Impermeable: (haemato-encephalic barrier) CNS,
thymus, testes, peripheral nerves
Fenestrated, visceral capillaries
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Endothelium with fenestrae - opening
Lamina basale
Pericytes
Occurrence:
Intestinal villi, endocrine glands and exocrine
pancreas, peritubular capillaries in kidney, choroid
plexus
Fenestrated capillaries without
diaphragm
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Glomerular capillaries in kidney
Discontinuous capillaries,
sinusoids
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Endothelium, wide intercellular spaces
Discontinuous lamina basale
Pericytes are not present
Occurrence: bone marrow, spleen, liver
Microcirculation in organs
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Arteriovenous anastomoses
Portal systems:
Artery – artery – vein (kidney)
Artery- vein – vein (liver, hypophysis)
Lymphatic vessels
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Capillaries- start as blind, closed-ended vessels in
connective tissue.
Wide intercellular spaces, anchoring fibrils –
junction between endothelial cells and collagen
fibrils within surrounding connective tissue
(collagen type 6), discontinuous lamina basale
Larger lymphatic vessels are similar in structure to
veins. Typical are valves.