Download lymphatic vascular system

組織學
Historlogy
台北醫學大學/解剖學科
教授：邱瑞珍
分機號碼：3261
電子郵件信箱：[email protected]
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The Circulatory
System
台北醫學大學/解剖學科
教授：邱瑞珍
分機號碼：3261
電子郵件信箱：[email protected]
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學習目的
• The structure of the arteries
• The structure of the veins
• The structure of the lymphatic vessels
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參考資料
• Junqueira's Basic Histology, twelfth
edition, text and atlas, Anthony L.
Mescher, McGraw-Hill Companies
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Summary
• HEART
• STRUCTURAL PALN OF BLOOD
VESSELS
• LYMPHATIC VASCULAR SYSTEM
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Circulatory system:
blood & lymphatic vascular systems
Blood vascular system: composed
heart : pump blood
arteries: efferent vessels, carry blood with
nutrients & oxygen Æ tissue
capillaries: smallest blood vessels, interchange
veins: convergence of capillaries, convey blood
Æ heart
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Lymphatic vascular system:
begin with lymphatic capillaries
closed-ended tubules Æ larger vessels
Æ blood vascular system
return fluid of tissue space Æ blood
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Internal surface: endothelium
Circulatory system:
macrovasculature:
vessels more than 0.1mm in diameter
large arterioles, muscular &
elastic arteries, muscular veins
microvasculature:
arterioles, capillaries,
post-capillary venules
functional important:
site of interchange
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HEART
A muscular organ
contract rhythmically, pumping blood
R & L ventricles: blood Æ lung & rest of body
R& L atria: receive blood from body & lung
Walls of heart:
internal endocardium
middle mycardium
external epicardium
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Endocardium
A single layer of squamous endothelial cells
Thin layer of loose connective tissue:
elastic & collagen fibers &
smooth muscle cells
Subendocardial layer:
veins & nerves, branch of impulse-conducting
system
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Myocardium
Thickest, consist of cardiac muscle cells
Arranged in layers: surround heart chambers
complex spiral
Ventricles thicker than atria
Epicardium
Simple squamous epithelium (mesothelium)
support by a thin layer of connective tissue
Subepicardial layer:
veins, nerves, adipocytes
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Heart valves:
central core: dense fibrous connective tissue
(containing elastic & collagen fibers)
both sides: endothelial layers
bases: attach to strong fibrous rings
part of fibrous skeleton
site of origin & insertion of
cardiac muscle fibers
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Heart: specialized system
generate a rhythmic stimulus for contraction
Consist:
2 nodes located in right atrium:
sinoatrial (SA) node: pacemaker
atrioventricular (AV) node
Atrioventricular bundle (of His)
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SA node:
a small mass of modified cardiac muscle cells
fusiform, smaller & fewer myofibrils
AV node:
similar to SA node
cytoplasmic projections branch in various
directions
AV bundle:
originate from node
pass along interventricular septum
split into L & R bundles
branches to both ventricles
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Distal fibers of AV bundles:
larger than ordinary cardiac muscle fibers
conducting myofibers or Prukinje fibers
1 or 2 nuclei
cytoplasm: rich in mitochondria, glycogen
myofibrils: sparse, restricted to periphery
Both parasympathetic & sympathetic
neural components Æ heart
Ganglionic nerve cells & nerve fibers:
present close to SA & AV nodes
affect heart rate & rhythm
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Parasympathetic: slow heartbeat
Sympathetic: accelerate rhythm
Between muscle fibers:
afferent free nerve endings
sensibility & pain
Partial obstruction of coronary arteries:
reduce supply of oxygen
cause pain (angina pectoris)
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STRUCTURAL PALN OF BLOOD VESSELS
3 layers of vascular wall:
Tunica intima
One layer of squamous epithelial cells
Subendothelial layer: loose connective tissue
smooth muscle found in
In arteries:
internal elastic lamina
most external component of intima
composed of elastin
holes (fenestrated) allow diffusion
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Tunica media
Middle layer
Concentric layers of helically arranged
smooth muscle cells
Among smooth muscle cells:
elastic fibers & lamellae, reticular fibers,
proteoglycans, glycoprotein
In arteries:
external elastic lamina
separate from adventitia
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Tunica adventitia (tunica externa)
Consist of type I collagen & elastic fibers
Continuous with stromal connective tissue of organs
Large vessels:
vasa vasorum
consist of arterioles, capillaries, venules
in tunica adventitia & outer part of media
provide metabolites to cells of those layers
large vessels: walls too thick
to be nourished by diffusion from lumen
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Larger vessels:
supplied with sympathetic nerve fibers
norepinephrine Æ vasoconstriction
nerve not enter media of arteries:
neurotransmitter – diffusion
smooth muscle : gap junctions
Thinner walled veins:
nerve ending: in adventitia & media
overall density :
less than encountered arteries
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In skeletal muscle:
arteries: also receive cholinergic vasodilator
nerve supply
Acetylcholine: act on endothelium
produce nitric oxide
diffuse to smooth muscle cells
Æ muscle relax Æ lumen dilated
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Large Elastic Arteries
Help to stabilize blood flow
Include: aorta & its large branches
Fleshly: yellowish color from elastin in media
Intima: thicker than muscular arteries
internal elastic lamina: present
may not easily discerned
Media:
elastic fibers & concentrically
arranged elastic laminae
smooth muscle cells, reticular
fibers, proteoglycans,
glycoproteins
Adventitia: relatively underdeveloped
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Muscular Arteries
Control blood flow Æ organs
Intima: very thin subendothelial layer
prominent internal elastic lamina
Media: up to 40 layers of more
prominent smooth muscle cells
intermingled with elastic lamellae, reticular
fibers, proteoglycans
external elastic lamina:
only in larger muscular arteries
Adventitia: connective tissue
contain lymphatic capillaries, vasa vasorum,
nerves
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Arterioles
Muscular arteries branch repeatedly
Æ smaller and smaller
Æ 2 or 3 medial layers of muscle
Arterioles:
smallest arteries
1 or 2 layers of smooth muscle layers
generally less than 0.5 mm in diameter
lumen as wide as wall is thick
subendothelial layer: very thin
elastic laminae: absent
media: circularly arranged smooth
muscle cells
adventitia: very thin & inconspicuous
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Capillaries
Permit different levels of metabolic exchange
between blood & tissues
Composed of :
a single layer of endothelial cells
Endothelial cells: form a tube
Capillaries:
5-10 μm average diameter
length: 50 μm
comprise over 90% of all blood vessels
total length: 96000km
total diameter: 800 times larger than aorta
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Velocity of blood:
in aorta: 320 mm/s
in capillaries: 0.3 mm/s
because their thin wall & slow flow
a favorable place for exchange
water, solutes, macromolecules
In general:
endothelial cells: polygonal & elongated
in the direction of blood flow
nucleus: bulge into lumen
junctions of tight zonula occludentes type present
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Pericytes:
enclosed by a basal lamina
may fuse with that of endothelial cells
well-developed networks of myosin, actin,
tropomyosin : contractile function
After tissue injuries:
pericytes proliferate & differentiate
Æ form tunica media & cells with various
other functions in re-establishing
microvasculature & its ECM
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Capillary: structural variations
3 types
1. continuous (tight) capillaries
allow regular exchange of material
most common type
found in muscles, connective tissue,
exocrine glands & nervous tissue
pinocytotic vesicles : luminal
& basal surface
transport of material
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2.Fenestrated capillaries:
allow more extensive molecular exchange
presence of small circular fenestrae
covered by a very thin diaphragm
containing heparan proteoglycans
no lipid bilayer
basal lamina: continuous voering fenestrae
found in kidney, intestine, choroid plexus,
endocrine glands
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3. Sinusoid (Discontinuous) capillaries :
permit maximal exchange
endothelial cells:
large fenestrae without diaphragm
form a discontinuous layer
separate from one another:wide space
basal lamina: also discontinuous
irregularly shaped
diameter: 30-40μm
found in liver, spleen, some endocrine organs,
bone marrow
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Venules
Transition from capillaries to venules:
gradually
Postcapillary venules:
similar structurally to capillaries
with pricytes
but diameter: from 15-20μm
participate in exchange
converge Æ larger collecting venules
Æ 2 or 3 smooth muscle layers
Æ muscular venules
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Veins
Blood entering vein: very low pressure
move forward heart:
contraction of tunica media
external compression from surrounding
muscles or organs
Valve:
projection from tunica intima
to prevent back-flow of blood
Most veins: small or medium veins
diameter less than 1 cm
located in parallel with
muscular arteries
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Intima
thin subendothelial layer
Media
small bundles of smooth muscle cells
intermixed with reticular fibers & a delicate
network of elastic fibers
Adventitia
collagenous
well-developed
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Big venous trunks, paired with elastic arteries:
large veins
Well developed intima
Media: relative thin
few layers of smooth muscle cells
abundant connective tissue
Adventitia:
thick in large veins
frequently contain longitudinal bundles of
smooth muscle
Both media & adventitia:
contain elastic fibers
not like those of elastic arteries
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LYMPHATIC VASCULAR SYSTEM
Collect excess interstitial fluid from tissue space
return to blood
Fluid: lymph
Flow in only one direction: toward the heart
Lymphatic capillaries
originate in various tissue
thin, closed-ended vessels
a single layer of endothelium +
an incomplete basal lamina
held open by bundles of anchoring filaments
of elastic fiber system
also bind vessels to connective tissue
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Lymphatic capillaries Æ larger lymphatic vessels
Interposed in path : lymph nodes
Lymphatic: found in almost all organs
except CNS & bone marrow
Larger lymphatics:
similar to veins
thinner walls
lack a clear-cut separation between tunics
more numerous internal valves
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Lymphatic vessels:
dilated
assumed a nodular or beaded, between valves
Lymphatic circulation:
aided by external forces
contraction of skeletal muscles
unidirectional flow: many valves
contraction of smooth muscles of larger
lymphatic vessels: also help to propel
End up as 2 large trunk:
thoracic duct & right lymphatic trunk
empty lymph Æ veins
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Structure of lymphatic ducts:
similar to that of large veins
reinforced smooth muscle in middle layer
muscle bundles:
longitudinally & circularly arranged
former predominating
adventitia: relatively undeveloped
contain vasa vasorum & neural network
Lymphatic vessels:
also a major distributor of lymphocytes,
antibodies, immune components
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