Cardiovascular

propel blood to the pulmonary and

systemic circulation, respectively

propel blood to the pulmonary and

systemic circulation, respectively

right and left ventricles

Right and Left atria

receive blood from the body and the pulmonary

veins, respectively

Pumping the blood through the circulatory

Heart

Innermost layer

Endocardium

Consists of a very thin inner layer of endothelium and

supporting connective tissue, a middle myoelastic layer of smooth muscle fibers and connective tissue, and a deep layer of connective tissue (subendocardial layer) that merges with the myocardium

Endocardium

Thickest layer

Myocardium

Consists mainly of cardiac muscle with its fibers arranged

spirally around each heart chamber

Myocardium

Simple squamous mesothelium supported by a layer of

loose connective tissue containing blood vessels and

nerves

Epicardium

Corresponds to the visceral layer of the pericardium

reflected back as the parietal layer lining the

pericardium

Epicardium

regions of dense irregular connective Tissue

Anchoring and supporting the heart valves

Providing firm points of insertion for cardiac muscle

Helping coordinate the heartbeat by acting as electrical insulation

between atria and ventricles

innervate the

heart

parasympathetic and sympathetic neural

(vagus nerve) slows the heartbeat

parasympathetic division

accelerates activity of the pacemaker

sympathetic nerve

Located in the right atrial wall near the superior vena cava

•Impulses initiated by these cells move along the

myocardial fibers of both atria, stimulating their contraction

SA node

Thickest layer

•Located in the floor of the right atrium near the AV valve •Conducting muscle fibers from the AV node form the AV

bundle, pass through an opening in the cardiac skeleton into the interventricular septum, and bifurcate into the wall of each ventricle

AV node

Pale-staining fibers, larger than the adjacent contractile

muscle fibers, with sparse, peripheral myofibrils and much glycogen

Pukinje fiber

Mingle distally with contractile fibers of both ventricles

and trigger waves of contraction through both ventricles simultaneously.

Pukinje fiber

The endothelium presents a --------- on which blood will

not clot and actively secretes agents that control local clot formation (such as heparin, tissue plasminogen activator, and von Willebrand factor)

non-thrombogenic surface

has several roles in inflammation and local immune responses. §���Secrete various growth factors

Endothelium

occur in the walls of all vessels larger than capillaries and

are arranged helically in layers

Smooth muscle fibers

•Innermost layer which consists of the endothelium and a

thin subendothelial layer of loose connective tissue

•Has internal elastic lamina in vessels and large veins

Tunica intima

Located in the right atrial wall near the superior vena cava

Tunica intima

Middle layer, consists chiefly of concentric layers of

helically arranged smooth muscle cells

•Middle layer, consists chiefly of concentric layers of

helically arranged smooth muscle cells

Tunica media

Outermost layer

•Consists principally of type I collagen and elastic fibers •Continuous with and bound to the stromal connective

tissue of the organ through which the blood vessel runs. •In large vessels, has vasa vasorum (vessel of the vessel) –

which supplies oxygen and nutrients to the vessel

Tunica

adventitia

•Includes aorta, the pulmonary artery, and their largest

branches; •Also called conducting arteries because their major role

is to carry blood to smaller arteries.

Elastic arteries

Light dilations of the bilateral internal carotid arteries

where they branch from the (elastic) common carotid arteries; they act as important baroreceptors monitoring arterial blood pressure

Carotid sinus

Chemoreceptors that monitor blood levels of CO2 and

O2, as well as its hydrogen ion concentration (pH)

•Located in the walls of the carotid sinuses and aortic arch,

respectively

Carotid bodies and aortic bodies

•Distribute blood to the organs and help regulate blood

pressure by contracting or relaxing the smooth muscle in the media. The intima has a very thin subendothelial layer and a prominent internal elastic lamina

Muscular arteries

• Have only one or two smooth muscle layers – indicating the

beginning of an organ’s microvasculature where exchanges between blood and tissue fluid occur.

•Acting as “resistance vessels,” muscle tone usually keeps

arterioles partially closed and makes these vessels the major determinants of systemic blood pressure.

•Alternate microvascular pathways: arteriovenous shunts, and

portal system

Arterioles

Permit and regulate metabolic exchange between blood and

surrounding tissues. •These smallest blood vessels always function in groups •Capillaries are generally grouped into three histologic types,

depending on the continuity of the endothelial cells and the external lamina

Capillary

beds

Have many tight, well-developed occluding junctions between

slightly overlapping endothelial cells, which provide for continuity along the endothelium and well-regulated metabolic exchange across the cells.

•Found in muscle, connective tissue, lungs, exocrine glands, and

nervous tissue

Continuous capillaries

A sieve- like structure that allows more extensive molecular exchange

across the endothelium.

•The endothelial cells are penetrated by numerous small circular

openings or fenestrations.

•Found in organs with rapid interchange of substances between

tissues and the blood, such as the kidneys, intestine, choroid plexus, and endocrine glands.

Fenestrated capillaries

Permit maximal exchange of macromolecules as well as allow easier

movement of cells between tissues and blood.

•Individual endothelial cells here have large perforations without

diaphragms; collectively they form a discontinuous layer, with wide, irregular spaces between the cells.

•Found in the liver, spleen, some endocrine organs, and bone marrow

Discontinuous capillaries

Postcapillary venules – collecting – muscular venules

•A characteristic feature of all venules is the large diameter of

the lumen compared to the overall thin- ness of the wall

Venules

Carry blood back to the heart from microvasculature all over

the body •Valves project from the tunica intima to prevent backflow of

blood

Veins

Usually located close and parallel to corresponding muscular

arteries

Small veins

The big venous trunks, paired with elastic arteries close to the

heart; example is vena cava •well-developed intima, but the media is relatively thin, with

alternating layers of smooth muscle and connective tissue

Large veins

Have very thin endothelial cells wals with spaces between

cells. •Drains interstitial fluid (lymph) that is not pulled into venules

by colloidal osmotic pressure •Converge into larger, thin-walled lymphatic vessels in which

lymph is propelled by movements of surrounding muscles and organs, with intimal valves keeping the flow unidirectional. •

Lymphatic vessels

The largest lymphatic vessels, ----- both with walls having tunics like those of veins, return lymph to the circulatory system by joining veins near the heart

the thoracic duct and right lymphatic duct