Overview of Blood Vessel Types and Structure

Vocabulary flashcards covering the main vessel categories, wall layers, cell junctions, and functional terms introduced in the lecture.

Artery

Macroscopic blood vessel that carries blood away from the heart; possesses the thickest overall wall, dominated by a large tunica media of smooth muscle.

Arteriole

Microscopic continuation of an artery; small-diameter vessel that leads directly to capillary beds and still contains smooth muscle for vasomotor control.

Vein

Macroscopic vessel that returns blood to the heart; wall is thinner than an artery’s and contains a relatively smaller tunica media.

Venule

Microscopic vein that drains capillaries and funnels blood toward larger veins; generally lacks a true tunica media.

Capillary

Microscopic exchange vessel composed almost entirely of the tunica intima (endothelium); thinness permits efficient diffusion of gases, nutrients, and wastes.

Tunica Intima (Tunica Interna)

Innermost layer of a vessel wall; consists of simple squamous endothelium anchored to a thin, elastic-rich connective tissue called the elastic lamina.

Tunica Media (Tunica Muscularis)

Middle layer, primarily smooth muscle with variable elastic fibers; responsible for vasoconstriction and vasodilation and is the thickest layer in arteries.

Tunica Adventitia (Tunica Externa)

Outermost layer made mostly of connective tissue (often dense irregular); anchors the vessel and houses the vasa vasorum in large arteries.

Endothelium

Simple squamous epithelial lining of the lumen that promotes smooth, laminar blood flow and allows limited diffusion.

Elastic Lamina

Thin sheet of elastic-rich connective tissue that binds the endothelium to the tunica media within the tunica intima.

Smooth Muscle (Vascular)

Muscle tissue in the tunica media that can be neurally or hormonally stimulated to change vessel diameter.

Vasoconstriction

Narrowing of a vessel’s lumen caused by contraction and inward bunching of vascular smooth muscle cells.

Vasodilation

Widening of a vessel’s lumen resulting from the relaxation of vascular smooth muscle cells.

Laminar Blood Flow

Smooth, streamlined flow of blood along the flat endothelial surface; opposite of turbulent flow.

Desmosome

Strong, flexible cell junction that mechanically links adjacent smooth muscle (or cardiac) cells in the vessel wall.

Gap Junction

Intercellular channel that permits electrical communication between smooth muscle cells, allowing coordinated, unit-like contraction.

Focal Density

Attachment point on the inner plasma membrane where smooth muscle contractile filaments anchor; critical for the cell’s inward ‘bunching’ during contraction.

Myofilaments (Actin & Myosin) in Smooth Muscle

Contractile proteins arranged diagonally rather than in linear sarcomeres, giving smooth muscle its characteristic shape change.

Vasa Vasorum

“Vessels of the vessels”; small arteries, arterioles, veins, and venules that supply the thick walls of large arteries, traveling mainly within the tunica adventitia.