Blood Vessel Structure, Function, and Physiology

Comprehensive vocabulary flashcards covering blood vessel anatomy, systemic circulation classes, capillary types, and physiological regulatory mechanisms.

Arteries

Blood vessels that carry blood away from the heart, typically carrying oxygenated blood (except pulmonary arteries) and possessing thick, elastic walls to withstand high pressure.

Veins

Blood vessels that return blood to the heart, containing valves to prevent backflow and acting as blood reservoirs by holding most of the body's blood volume.

Capillaries

Microscopic vessels only one cell thick that connect arterioles and venules; they serve as the primary site for exchange of gases, nutrients, and wastes.

Vasoconstriction

The decrease in lumen diameter as the smooth muscle in the tunica media contracts.

Vasodilation

The increase in lumen diameter as the smooth muscle in the tunica media relaxes.

Tunica intima

The innermost layer of a blood vessel wall containing the endothelial lining, a connective tissue layer, and the internal elastic membrane in arteries.

Tunica media

The middle layer of the vessel wall composed of concentric sheets of smooth muscle and elastic fibers; it is regulated by sympathetic vasomotor nerve fibers.

Tunica externa (adventitia)

The outermost layer of a vessel wall containing a connective tissue sheath of collagen and elastic fibers that anchors the vessel to adjacent tissues.

Vasa vasorum

Small arteries and veins found in the walls of large vessels that supply the cells of the tunica media and tunica externa.

Elastic arteries

Also called conducting arteries, these are large vessels like the aorta that contain many elastic fibers to dampen and even out pulse force.

Muscular arteries

Also called distributing arteries, these medium-sized vessels have a thick tunica media with many muscle cells and are active in vasoconstriction.

Arterioles

The smallest arterial branches, also known as resistance vessels, which change diameter in response to neural, hormonal, and chemical stimulation to regulate flow into capillaries.

Atherosclerosis

A form of arteriosclerosis involving lipid deposits in the tunica media and damage to the endothelial lining.

Aneurysm

A bulge in an arterial wall caused by a weak spot in the elastic fibers, which may rupture due to pressure.

Pericytes

Cells that help stabilize capillary walls and control permeability.

Continuous capillaries

The least permeable capillaries, abundant in skin and muscles, where tight junctions connect endothelial cells; specialized versions form the blood-brain barrier.

Fenestrated capillaries

Capillaries containing pores (fenestrations) that make them more permeable; found in the kidneys, small intestines, and endocrine glands for absorption or filtration.

Sinusoid capillaries

The most permeable capillaries with large lumens and intercellular clefts; found in the liver, bone marrow, and spleen to allow passage of large molecules and blood cells.

Metarteriole

A vessel structural bridge in a capillary bed that is intermediate between an arteriole and a capillary, continuing into a thoroughfare channel.

Precapillary sphincters

Smooth muscle rings that regulate blood flow into true capillaries based on local chemical conditions and vasomotor nerves.

Angiogenesis

The formation of new blood vessels, stimulated by Vascular Endothelial Growth Factor (VEGF) in embryos or in response to hypoxic conditions.

Venous sinuses

Flattened veins with extremely thin walls, such as the coronary sinus of the heart and dural sinuses of the brain.

Blood flow

The volume of blood flowing through a vessel, organ, or the entire circulation in a given period, measured in $\text{mL/min}$.

Blood Pressure (BP)

The force per unit area exerted on a vessel wall by blood, expressed in $\text{mmHg}$.

Peripheral resistance

The opposition to flow caused by friction encountered with vessel walls; determined by blood viscosity, total vessel length, and vessel diameter.

Systolic pressure

The pressure exerted in the aorta during ventricular contraction, averaging $\text{120\,mmHg}$ in a normal adult.

Diastolic pressure

The lowest level of aortic pressure reached during ventricular relaxation.

Pulse pressure

The difference between systolic and diastolic blood pressure.

Muscular pump

A mechanism aiding venous return where the contraction of skeletal muscles "milks" blood toward the heart.

Vasomotor tone

The state of moderate constriction maintained in blood vessels by steady sympathetic impulses from the vasomotor center.

Baroreceptors

Pressure-sensitive mechanoreceptors located in the carotid sinuses, aortic arch, and large arteries of the neck and thorax that detect changes in blood pressure.

Direct renal mechanism

A long-term blood pressure control where kidneys alter blood volume independently of hormones by increasing urine elimination when BP is high.

Indirect renal mechanism

The Renin-Angiotensin-Aldosterone pathway where renin release catalyzes a sequence to produce Angiotensin II, raising blood pressure.

Autoregulation

The automatic adjustment of blood flow within a tissue based on its specific metabolic requirements.

Filtration

The process at the arterial end of a capillary where high blood pressure pushes fluid out into the interstitial space.

Reabsorption

The process at the venous end of a capillary where osmotic pressure pulls fluid back into the vessel because blood pressure has dropped.