Foundations Exam 1

Tunica intima

the innermost layer of a blood vessel, composed of endothelium, which consists of a sheet of simple squamous epithelium and its basal lamina. Endothelial cells provide a smooth surface over which blood can flow with a minimum friction and turbulence. Deep to endothelium is a thin layer of subendothelial connective tissue and a layer of elastic fibers called the internal elastic lamina. Elastic fibers lead to distensibility and elasticity

Describe the basic properties of muscular arteries

-intermediate diameter -distributing arteries -well-developed tunica media composed primarily of smooth muscle cells -most smaller branches off the aorta -control blood flow to organs -regulate blood pressure -diameter does change significantly with vasoconstriction and vasodilation

Describe the basic properties of elastic arteries

-largest-diameter arteries -also known as conducting arteries -extensive elastic lamina -aorta and its immediate branches -under highest pressure of any vessels so need to be extremely distensible as they are greatly stretched with each ventricular systole -small amount of smooth muscle tissue means that they do not change diameter significantly with stimulation from vasomotor nerves. -Conduct blood under high pressure to organs

Venules

-small venules have only a tunica intima, larger venules have all three tunics -drain capillary beds

Predict the possible effects of defective elastic fibers in arteries

Elastic fibers in an artery allow the vessel to stretch and recoil to its original size after being stretched. Defective elastic fibers would make a vessel noncompliant (not able to stretch) or unable to recoil to its original size after stretching.

Tunica media

Middle layer of the blood vessel wall. Composed of two components: a layer of smooth muscle cells arranged in a circular manner around the lumen, and another layer of elastic fibers called the external elastic lamina. The smooth muscle cells of the tunica media control the diameter of the blood vessel and so the amount of blood that flows to organs.

Which type of artery controls blood flow to organs?

Muscular arteries

Tunica externa

Outermost layer of a blood vessel. Composed of dense irregular collagenous connective tissue that supports the blood vessel and prevents it from overstretching.

Metarterioles

Smallest arterioles that directly feed capillary beds in most tissues

Of which tissue type is the tunica media composed?

Smooth muscle cells and external elastic lamina

precapillary sphincters

Smooth muscle cells of metarterioles are confined mostly to a precapillary sphincter that encircles the metarteriole-capillary junction

How do veins differ structurally and functionally from arteries?

Structurally: thinner walls, fewer elastic fibers, less smooth muscle, larger lumens Functionally: drain blood from capillary beds and deliver it back to the heart

What are venous valves and what are their functions?

They are extensions of the tunica intima that overlap and prevent blood from flowing backward in the venous circuit

What are vasoconstriction and vasodilation?

Vasoconstriction- narrowing of the blood vessels Vasodilation- widening of the blood vessels

Vasoconstriction

Vasomotor nerves of the sympathetic nervous system stimulate the smooth muscle cells of the tunica media to contract. This narrows the diameter of the vessel

Blood reservoirs

Veins outnumber arteries and their lumens have a larger average diameter. For these reasons, up to 70% of the total blood in the body is located in the veins at any given moment. When necessary, blood can be diverted from the veins to other parts of the body.

Would you expect the same effects if venous elastic fibers were defective?

Veins would also be affected, as they are very compliant. However, they are under lower pressure than arteries and so the effects would be less obvious

What are venules and how do they differ from veins?

Venules are the smallest veins that drain blood from the capillary beds. As venules merge the three tunics become more distinct and they become veins

Vasodilation

When sympathetic stimulation of the smooth muscle cells decreases, these cells relax and the vessel's diameter increases

Capillaries

are the exchange system of the vasculature. Capillaries are vessels of very small diameter that form branching networks called capillary beds. Gases, nutrients, wastes, and other substances are quickly exchanged between cells and the blood through the capillary walls.

Of which tissue type is the Tunica intima composed?

composed of endothelium, which consists of a sheet of simple squamous epithelium and its basal lamina. Deep to endothelium is the subendothelial connective tissue and the internal elastic lamina.

Of which tissue type is the tunica externa composed?

dense irregular collagenous connective tissue

Veins

function as the collection system of the vasculature. They drain blood from capillary beds and return it to the heart. Small veins merge to become progressively larger as they get closer to the heart. Pulmonary circuit is oxygenated blood, systemic circuit is deoxygenated blood.

Arteries

the distribution system of the vasculature. Vessels that travel away from the heart, branching into vessels of progressively smaller diameter. Arteries in the pulmonary circuit carry deoxygenated blood. Arteries in the systemic circuit carry oxygenated blood

Describe the basic properties of arterioles

-smallest arteries -thin walls with all three tunics -control blood flow to tissues -feed capillary beds

Define the three types of blood vessels in the cardiovascular system.

Arteries- vessels that travel away from the heart, branching into vessels of progressively smaller diameter Capillaries- vessels of very small diameter that form branching networks called capillary beds where gases, nutrients, wastes, and other substances are quickly exchanged between cells and the blood through the capillary walls Veins- drain blood from the capillary beds and return it to the heart. Merge with other veins to become progressively larger in diameter as they get closer to the heart.

Which type of artery control blood flow to tissues?

Arterioles

How does atherosclerosis change the structure of an artery? How does this impair the artery's ability to perform its functions?

Atherosclerosis makes an artery narrow and hard through damage to the endothelium. This interferes with its function of delivering blood to capillary beds by decreasing the amount of blood that can flow through the artery.

Chemoreceptors

chemical sensors in the brain and blood vessels that identify changing levels of oxygen and carbon dioxide. Found in aorta and common carotid artery.

Muscular arteries (distributing arteries)

intermediate in diameter. Well developed tunica media composed of primarily smooth muscle cells so diameter does change with vasoconstriction and vasodilation

Elastic arteries (conducting arteries)

largest diameter; include aorta and its immediate branches; nearest heart and therefore under highest pressure of any vessels in cardiovascular system. Extensive elastic lamina with fewer smooth muscle cells so diameter does not change significantly with stimulation from the vasomotor nerves

Vascular anastomoses

locations where vessel connect via pathways called collateral vessels

What is an anastomosis?

locations where vessel connect via pathways called collateral vessels

Baroreceptors

monitor blood pressure. Found in the aorta and common carotid artery

venous anastomoses

neighboring veins are connected by small collaterals

Vasa vasora

small blood vessels that supply oxygen and nutrients to the outer layers of the larger blood vessels, whose cells are too far away from the lumen to receive oxygen and nutrients by diffusion alone

Arterioles

smallest arteries. Contain each of the three layers of blood vessels but the layers are thin, and the tunica media contains only one to three layers of smooth muscle cells