Microsoft PowerPoint - 5-2circulatory_system.ppt2

• The structure of the arteries • The structure of the veins • The structure of the lymphatic vessels
3

• Junqueira's Basic Histology, twelfth edition, text and atlas, Anthony L. Mescher, McGraw-Hill Companies
4
Summary
VESSELS • LYMPHATIC VASCULAR SYSTEM
Blood vascular system: composed heart : pump blood arteries: efferent vessels, carry blood with
nutrients & oxygen tissue capillaries: smallest blood vessels, interchange veins: convergence of capillaries, convey blood
heart
6
return fluid of tissue space blood
7
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
A muscular organ contract rhythmically, pumping blood
R & L ventricles: blood lung & rest of body R& L atria: receive blood from body & lung Walls of heart:
internal endocardium middle mycardium external epicardium
9
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
10
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
(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
12
Consist: 2 nodes located in right atrium:
sinoatrial (SA) node: pacemaker atrioventricular (AV) node
Atrioventricular bundle (of His)
13
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
14
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 heart
Ganglionic nerve cells & nerve fibers: present close to SA & AV nodes affect heart rate & rhythm
15
afferent free nerve endings sensibility & pain
Partial obstruction of coronary arteries: reduce supply of oxygen cause pain (angina pectoris)
16
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
17
smooth muscle cells Among smooth muscle cells:
elastic fibers & lamellae, reticular fibers, proteoglycans, glycoprotein
In arteries: external elastic lamina separate from adventitia
18
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
19
neurotransmitter – diffusion smooth muscle : gap junctions
Thinner walled veins: nerve ending: in adventitia & media
overall density : less than encountered arteries
20
nerve supply Acetylcholine: act on endothelium
produce nitric oxide diffuse to smooth muscle cells
muscle relax lumen dilated
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
Adventitia: relatively underdeveloped 23
Control blood flow 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
24
Arterioles
Muscular arteries branch repeatedly smaller and smaller 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 25
Capillaries
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
26
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
27
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 form tunica media & cells with various
other functions in re-establishing microvasculature & its ECM
28
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
29
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
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
Postcapillary venules: similar structurally to capillaries with pricytes but diameter: from 15-20μm participate in exchange converge larger collecting venules
2 or 3 smooth muscle layers muscular venules
32
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 33
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
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
35
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
36
Lymphatic capillaries 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
37
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 veins
38
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