HIS 2.02 v2 Heart and Blood Vessels

Mechanical valve integrity, rich in elastin.

Elastic (Conducting), Muscular (Distributing), and Arterioles.

Aorta, brachiocephalic trunk, common carotid, subclavian, and pulmonary trunk.

The tunica adventitia/externa is composed of Type I collagen and elastin.

Carotid sinuses are slight dilatations of the bilateral internal carotid artery that act as baroreceptors to detect increases in blood pressure.

Smooth muscle cells.

It expands, reducing the pressure and allowing strong blood flow to continue during diastole.

Endocardium, Myocardium, and Epicardium (Visceral Pericardium).

It has small bundles of smooth muscle cells mixed with a network of reticular fibers and delicate elastic fibers.

To carry blood from the heart to smaller arteries and help stabilize blood flow.

Continuous capillary, Fenestrated capillary, Discontinuous/Sinusoidal capillary.

Endocardium (En), Subendocardium (SEn), Purkinje fibers (P), Myocardium (M).

Presence of Purkinje cells, which are light staining compared to regular cardiac muscle cells.

Radial, femoral, coronary, cerebral arteries.

The tunica adventitia/externa is the thickest layer in veins.

Less than 0.5mm in diameter (microvasculature), with some sources noting less than 0.1mm.

A system of fine lymphatic channels provides a network throughout the body via lymph nodes to the thoracic duct, which eventually excretes the excess fluid to the kidneys, lungs, feces, skin, etc.

Vasomotor nerves release norepinephrine, a vasoconstrictor, which acts on alpha-1 adrenergic receptors in smooth muscle cells of arterioles.

Myocardium

Lymphatics do not have any RBCs in their lumen.

Capillaries are the smallest blood vessels, averaging 4-10 μm in diameter, composed of a single layer of endothelial cells, surrounded by a thin basement membrane, and contain pericytes.

Radial, femoral, coronary, and cerebral arteries.

The tunica media is composed of concentric layers of helically arranged smooth muscle, elastin, elastic lamellae, reticulin fibers, and proteoglycans.

The tunica media is thicker in arteries.

The heart pumps blood.

1-9 mm in diameter.

In organs with rapid interchange of substances between tissue and blood, such as kidneys, intestine, choroid plexus, and endocrine glands.

Endothelin and Nitric Oxide (NO).

Venules have a larger lumen, look bigger because they are collapsible due to their elastin component.

The elastic component of blood vessels will compensate to accommodate the high pressure. If unable to stabilize the pressure, there is a risk of blood vessel rupture, resulting in an aneurysm.

Aorta, brachiocephalic trunk, common carotid, subclavian, pulmonary trunk.

The EEL is evident in larger arteries but disappears in smaller muscular arteries with 1-2 layers.

Sinusoid (S), Adipocytes (A), Hematopoietic cells (H).

In the tunica adventitia/externa of large blood vessels.

Arteries have a smaller lumen, while veins have a bigger lumen.

The subendocardium is continuous with the myocardium and contains the impulse conducting system or specialized cardiac muscle cells (Purkinje cells & bundle of His).

Capillaries form capillary beds where the interchange between blood and tissues takes place.

Usually thin, lined by simple squamous epithelium (endothelium), and may contain connective tissue.

The lymphatic system returns the fluid of tissue spaces to the blood and plays a role in edema.

A disease of elastic arteries and large muscular arteries initiated by damaged or dysfunctional endothelial cells.

Angina pectoris is chest pain caused by reduced blood flow to the heart muscles.

Masson's trichrome.

Partial obstruction of the coronary arteries by atherosclerotic plaques.

To conduct blood from the heart and help move blood forward under steady pressure with elastic recoil.

To drain capillary beds and serve as the site of leukocyte exit from vasculature.

d) All of the above

Capillaries are very small, making them sometimes not visible due to their size.

Arteries have a thicker tunica media compared to veins, which have a thinner tunica media and a thicker adventitia.

Tunica Intima, Tunica Media, and Tunica Adventitia/Externa.

Distributing arteries.

The ventricles.

The atria receive blood from the body and pulmonary veins.

The cardiovascular system and the lymphatic system.

The endocardium is the innermost layer, composed of simple squamous endothelium, and may have loose fibroelastic connective tissue and scattered fibers of smooth muscle.

Dense collagenous core connected to valvular supporting structures.

A specialized epithelium lined by simple squamous epithelium.

Elastic artery, muscular artery, arteriole, capillary, venules (postcapillary vein, collecting vein, muscular vein), vein (small, medium, large vein).

It prevents blood coagulation (anti-thrombogenic).

Purkinje fibers are responsible for conducting electrical impulses that regulate the heart's rhythm.

Smooth muscle and connective tissue.

Capillaries can vary histologically and include continuous, fenestrated, and sinusoidal types.

Angina Pectoris.

To convey the blood to be pumped again.

To return blood to the heart.

Elastic arteries (conducting arteries), muscular arteries (distributing arteries), and arterioles (terminal branches).

The tunica intima is composed of endothelium and a thin subendothelial layer of loose connective tissue. Smooth muscle presence is variable.

At the junction between the metarteriole and the true capillaries.

5-10 cycles per minute.

The ventricles propel blood to the pulmonary and systemic circulations.

They are the major determinant of systemic blood pressure.

The myocardium is the thickest layer of the heart, composed of cardiac muscle cells arranged spirally around each heart chamber.

Pulmonary circulation involves the movement of blood from the right ventricle through the lungs to the left atrium for oxygenation, while systemic circulation involves the distribution of oxygenated blood from the left ventricle to the body and the return of low-oxygen blood to the right atrium.

The specialized system generates a rhythmic stimulus that is spread to the entire myocardium.

Well-developed with prominent valves.

The left ventricle propels blood to the aorta to be distributed to the body.

The vasa vasorum are small blood vessels that supply the walls of larger blood vessels.

A gruel-like mix of smooth muscle cells, collagen fibers, and lymphocytes with necrotic regions of lipid, debris, and foam cells.

To deliver oxygen-rich blood to capillaries.

Arteries maintain their circular shape and have a very prominent and thick tunica media.

It separates the tunica media and tunica externa/tunica adventitia.

They regulate blood flow into the true capillaries by opening and closing the entrance.

The tunica adventitia is composed of collagenous and elastic fibers, is thinner than the media, contains vasa vasorum, and lacks smooth muscles.

To control the distribution of blood to organs and help regulate blood pressure by contraction or relaxation.

To prevent backflow of blood.

The cardiac skeleton surrounds, anchors, and supports the valves, provides firm points of insertion for cardiac muscles, and acts as electrical insulation between the atria and ventricles.

Veins contain valves.

Proteoglycans.

Smooth muscle.

They penetrate the ventricle, become intramyocardic, and trigger waves of contraction through both ventricles.

Blood bypasses the capillary bed and flows through the thoroughfare channel to the venule.

Thickest layer with longitudinal bundles of smooth muscle and elastic fibers.

A thrombus (intravascular clot) is formed, exposing subendothelial tissues that induce platelet aggregation and fibrin production, eventually forming the clot.

Dyslipidemia, hyperglycemia of diabetes, hypertension, and smoking.

To drain into small veins that open into larger veins.

To exchange metabolites by diffusion to and from cells.

Fenestrated

In older patients or those with atherosclerosis, blood vessels are less elastic and may produce a 'crunchy sound' when held.

It consists largely of many well-developed elastic lamellae.

Arteriole → muscular artery → elastic artery.

Basal lamina (BL), Golgi apparatus (G), Nucleus (N), Centrioles (C).

Carotid bodies are small, ganglia-like structures near the bifurcation of the common carotid artery that act as chemoreceptors sensitive to blood CO2 and O2 concentrations, and pH.

They become surrounded by a recognizable tunica media with smooth muscle layers called muscular venules.

The heart and blood vessels.

It consists only of endothelium, where the cells may have rounded nuclei.

The myocardium is the thickest layer, especially in the ventricles, to generate more force to eject blood through the systemic and pulmonary circulations.

70-80% in systemic circulation, 18% in pulmonary circulation, and 12% in the heart.

It acts as the pacemaker of the heart.

Relatively thin with alternating smooth muscle and connective tissue, containing elastic fibers.

To aid in directing venous blood flow towards the heart.

The microvasculature, including arterioles, capillaries, and post-capillary venules.

To pump blood.

Artery

Arterioles can maintain their circular shape, have a visible tunica media, and are made of smooth muscle.

The tunica media is extremely elastic, contains sheets of elastin, connective tissues more visible than smooth muscles, and has around 40 layers that help blood flow become more uniform.

Conducting arteries.

Pericytes are mesenchymal cells with long cytoplasmic processes that are contractile and regulate flow through junctions in capillaries.

Lumen (L), Nucleus (N), Endothelial cells (E), Basal lamina (BL), Pericytes (P), Collagen fibers (C).

Blood flow is normal and well-perfused, moving from the capillary bed to the venule.

It has multiple layers of smooth muscle thicker than the elastic lamellae and fibers.

They have tight, occluding junctions with minimal fluid leakage and continuity of endothelial cells in their walls.

Arteries carry oxygen-rich blood and nutrients to the tissues, except for pulmonary arteries which carry deoxygenated blood from the heart to the lungs.

Close to the heart, such as the superior and inferior vena cava.

They have large fenestrations permitting maximal exchange of macromolecules and easier movement of cells between tissues and blood.

The right atrium receives blood from the superior and inferior vena cava.

The right ventricle propels blood to the pulmonary trunk into the lungs.

Fibro-fatty plaques.

They buffer the increases in pulsatility that occur due to intermittent left ventricular contraction.

Elevated blood pressure which may occur secondary to renal or endocrine problems.

Carotid sinus massage can initiate a vagal reflex, resulting in bradycardia and hypotension, and is used to terminate some supraventricular tachycardias (SVTs).

Capillary beds are formed by the branching of arterioles, function in networks, are supplied by metarterioles, and their density is related to the metabolic activity of the tissues.

To drain capillary beds and serve as the primary site of WBC adhesion to the endothelium.

Continuous capillaries, fenestrated capillaries, and discontinuous (sinusoidal) capillaries.

Venules have a larger lumen and thinner walls, while arterioles have a smaller lumen and thicker walls.

To carry blood back to the heart and serve as a major reservoir of extra blood.

They have a sieve-like structure with numerous fenestrations allowing more extensive molecular exchange.

Acts as a semipermeable membrane, regulates vascular tone and blood flow, prevents blood coagulation, and plays a role in inflammation and local immune responses.

In the liver, spleen, bone marrow, and some endocrine organs.

The left atrium receives blood from the two pairs of pulmonary veins.

Lipid-filled macrophages that accumulate along with free LDL, forming fatty streaks.

In the veins of the legs.

Localized destruction within the wall, weakening it and causing arterial bulges or aneurysms which can rupture.

To form capillary beds where interchange between blood and tissues takes place.

Blood flow is slow and bypasses the capillary bed, moving from the metarteriole to the venule through the thoroughfare channel.

In muscle, connective tissue, lungs, exocrine glands, and nervous tissue.

Endothelium, collagenous fibers, elastic fibers, and sheets. It is yellowish due to elastin and has a thicker intima compared to muscular arteries.

The epicardium, also known as the visceral pericardium, is the outermost layer, consisting of simple squamous epithelium (mesothelium) and some loose connective tissue that may or may not have fat tissues.

Collagenous, thick, and well-developed.

Arteries, veins, and capillaries.

The epicardium can be thick especially when there are lots of adipose tissue/fat cells.

Macrovasculature is greater than 0.1 mm, while microvasculature is less than 0.1 mm.

They can occlude blood flow to downstream vessels, leading to ischemic heart disease.

Many muscle fibers die as a result of low levels of O2, and the cardiac tissue can transform into scarred tissue if not treated early.

a) Right atrium

Delivery of O2 and nutrients to tissues, removal of CO2 and metabolic wastes, distribution of molecules like hormones, conduit for immune cells, and temperature regulation.

Fibrosa, Spongiosa, and Ventricularis.

The endothelium.

Vasa vasorum are arterioles, venules, and capillaries that provide metabolites to cells of large blood vessels. They are found in the tunica adventitia of large blood vessels.

Specialized cardiac cells that are pale staining, larger fibers with 1-2 central nuclei, and cytoplasm rich in mitochondria and glycogen.

They connect precapillary arterioles to postcapillary venules and are continuous with thoroughfare channels.

Damaged or dysfunctional endothelial cells oxidizing low-density lipoproteins (LDLs) in the tunica intima.

Hypertension is a condition characterized by consistently high blood pressure.

They act as a conduit to deliver a steady flow of blood to the microvasculature.

A wide variety of mechanisms that increase arteriolar constriction.

a) Vein

The heart consists of three layers: the epicardium, myocardium, and endocardium.

Atherosclerosis is a condition characterized by the buildup of fatty deposits (plaques) in the walls of arteries, leading to reduced blood flow.

Responsible for the vasoconstriction and vasodilation of the walls.

The internal elastic membrane.

To carry blood (nutrients and O2) to the tissues.

To distribute blood to all organs and maintain steady blood pressure and flow with vasodilation and constriction.

VEGF stimulates the formation of the vascular system from embryonic mesenchyme (vasculogenesis), helps maintain vasculature in adults, and promotes capillary sprouting and outgrowth from small vessels (angiogenesis).

Arteries → Arterioles → Capillaries → Venules → Veins.

Tunica media (TM), Tunica adventitia (TA), Valve (V).

Pulmonary arteries, which carry deoxygenated blood from the heart to the lungs.

To resist and control blood flow to capillaries and act as a major determinant of systemic blood pressure.