3.2 cardiovascular

innermost layer for cardiovascular

tunica intima or endocardium

middle layer for cardiovascular

tunica media or myocardium

outer most layer for cardiovascular

tunica adventitia or epicardium

tunica intima

closest to lumen

simple squamous epithelium (endothelium)

contacts blood

beneath endothelium is a subendothelial layer that is thicker in smooth muscle and is composed of LCT containing some smooth muscle

endothelium and elements of subendothelium are oriented

longitudinally

same axis of blood flow

5 major functions of endothelium

1. Maintains selective permeability barrier such as the blood-brain barrier.

2. Maintains non-thrombogenic barrier through secretion of anti-coagulant and

anti-thrombotic substances. Under some circumstances, releases pro-thrombotic

agents.

3. Modulates blood flow and vascular resistance by release of either

vasoconstrictors or vasodilators.

4. Regulates cell growth by releasing substances such as platelet Derived Growth

Factor (PDGF).

5. Regulates immune response by interactions with leukocytes.

6. Maintains ECM through synthesis of basal lamina components.

7. Involved in lipoprotein metabolism by release of free radicals and oxidation of

LDL

tunica media

most prominent layer in arteries

concentric layer of smooth muscle and elastic membranes

reticular fibers (type 3 collagen) and proteoglycans are found here

All ECM in media is made by smooth muscle cells

in arteries the media is separated from intima by

internal elastic lamina

tunica adventitia

most prominent layer in veins

connective tissue sheath that contains mostly type 1 collagen but also elastic fibers and smooth muscle

longitudinally arranged

blood vessels in large vessels

vasomotor nerves (nervi vascularis) form a network of

postganglionic sympathetic axons in the adventitia

they innervate smooth muscle of media to cause vasoconstriction

3 layers of heart

endocardium

myocardium

epicardium

the heart has an internal conducting system made up of

highly specialized muscle cells

endocardium

innermost

composed of endothelial lining with an underlying subendocardium

subendocardium composed of

LCT containing elastic and collagen fibers as well as some smooth muscle cells

also small veins, nerves and in some locations purkinje fibers

conduction system

made up of highly specialized cardiac muscle cells called purkinje fibers which are much larger than ordinary cardiac muscle cells, have fewer myofibrils (stain lighter), central nucleus (often binucleated) with light area where glycogen accumulates

impulses initiated at the SA node (pacemaker of heart) travel to

the AV node and then via the atrioventricular bundle (bundle of his) to its right and left bundle branches to the apex of the heart

an ischemic attack involving areas where purkinje fibers are located can be fatal

since damage to these fibers can result in the inability of the heart to contract rhythmically and effectively

myocardium

middle layer

thicker in ventricles than atria bc of high pressures

in ventricles there is an inner circular layer and an outer spiral layer

cardiac muscle is anchored to the

fibrous skeleton (cardiac skeleton) a dense fibrous connective tissue layer

heart muscle is post mitotic

ischemia due to coronary artery insufficiency can cause focal death of myocardial fibers

fibers are replaced by scare tissue

epicardium

outermost layer

thick layer of LCT with variable amounts of adipose tissue

contains arteries, veins and nerves

simple squamos

the mesothelium

is the visceral pericardium, a serous membrane that allows smooth muscle movement of the heart within the pericardial sac

heart valves are attached to

fibrous skeleton heart

two atrioventricular valves

right- tricuspid

left- bicuspid or mitral

large elastic arteries

called conducting arteries

characterized by prominent elastic lamellae in the media

have 40-70 layers of smooth

muscular arteries

media has 3-39 layers of smooth muscle

intima of elastic arteries

layer of endothelial cells resting on a thick subendothelium

connective tissue longitudinally oriented

internal elastic lamina not clearly defined bc of other elastic laminae in media

media of elastic arteries

concentrically arranged membranes of elastin

contains smooth muscle

concentric circularly arranged lamellae range 40-70 layers which increase in number from infancy to adulthood

rebound of elastin in media helps maintin blood pressure during diastole

adventitia of elastic arteries

relatively thin compared to the size of the vessel

contains vasa vasorum that extend into the media

marfans syndrome

abnormal fibrillin gene

abnormal elastic tissue

dissecting aneurysm of aorta

intima of muscular arteries

layer of endothelial cells resting on subendothelial layer

longitudinally arranged

most prominent feature is scalloped internal elastic lamina that separates the intima from the media

the internal elastic lamina can be seen especially in larger muscular arteries

media of muscular arteries

3-40 concentric layers of smooth muscle cells organized circularly

various amounts of elastin membrane interpsaced between smooth muscle layers, but unlike the internal elastic lamina they are only seen when special stain is used

adventitia of muscular arteries

external elastic lamina separates the media from adventitia

contains longitudinally oriented fibroblasts, collagen fibers and elastic fibers

contains vasa vasorum and lymphatics. vasa vasorum can extend into media but lymphatics do not

Atherosclerosis risk factors

-Age (more common in elderly)

-Gender (more common in men)

-Genetics

-Obesity

-High blood cholesterol levels

-High blood pressure

-Cigarette smoking

-Diabetes

intimal thickening of atherosclerosis

proliferation of intimal smooth muscle cells and accumulation of lipid

lipid accumulates in macrophages and smooth muscle cells (foam cells)

platelet derived growth factor (PDGF) implicated in smooth muscle cell proliferation

endothelium breaks down, platelets deposited, form plaques

plaques in atherosclerosis become

vascularized by vasa plaquorum

arterioles intima layer

layer of endothelial cells resting on a very thin subendothelium

internal elastic lamina not visible

media layer of arterioles

1-2 layers of concentrically arranged smooth muscle cells

adventitia of arterioles

very thin

look at slide 48 cardiovascular

capillaries

where exchange of nutrients, oxygen, carbon dioxide and metabolic waster occurs

continuous capillaries

continuous endothelium joined by tight junctions (zonula occludens)

found in CNS, PNS, muscle, CT and exocrine glands

also called somatic capillaries

CNS capillaries

continuous

surrounding basal lamina are astrocytic end feet which induce BBB

fenestrated capillaries

also called visceral capillaries

have pores in endothelium

many organs have diaphragms over the pores but not renal glomeruli

sinusoidal capillaries

also called discontinuous capillaries

large lumens

have macrophages on their walls

found in liver and lymphatic/hematopoietic organs

macrophages in sinusoidal capillaries for liver

kupffer cells

in diabetes mellitus and microvascular disease

capillary laminae thicken

also increase in laminin and collagen type 4 synthesis by endothelial cells

venules

small postcapillary vessels

thin walls

layer for veins

thin intima

thin media

thick adventitia

small or medium sized veins have

valves which are formed from subendothelial connective tissue and as such have a covering of endothelium

large veins layers

thick intima

thin media

prominent well developed adventitia (especially vena cava which has longitudinal bundles of smooth muscle in adventitia)

internal elastic laminae are seen in

muscular arteries

lymphatics

very thin walled vessels

larger irregular lumens than vascular capillaries

large lymphatics similar to veins but not well defined tunics