Anatomy & Physiology Chapter 20: The Circulatory System - Blood Vessels and Circulation

Vocabulary flashcards for reviewing the circulatory system and blood vessels.

Arteries

Carry blood away from the heart.

Veins

Carry blood back to the heart.

Capillaries

Connect smallest arteries to smallest veins, creating a circuit.

Tunica Interna (Tunica Intima)

Innermost layer of blood vessel walls; lines the blood vessel and is exposed to blood.

Endothelium

Simple squamous epithelium; selectively permeable barrier.

Tunica Media

Middle layer of blood vessel walls; consists of smooth muscle, collagen, and elastic tissue.

Tunica Externa (Tunica Adventitia)

Outermost layer of blood vessel walls; consists of loose connective tissue.

Vasa Vasorum

Small vessels that supply blood to the outer part of larger vessels.

Conducting (Elastic or Large) Arteries

Biggest arteries; examples include the aorta and common carotid arteries.

Elastic Arteries Function

Expand during systole and recoil during diastole.

Distributing (Muscular or Medium) Arteries

Distribute blood to specific organs; examples include brachial and femoral arteries.

Resistance (Small) Arteries

Small arteries with a thicker tunica media in proportion to their lumen.

Arterioles

Smallest of the resistance arteries; control amount of blood to various organs.

Aneurysm

Weak point in artery or heart wall; forms a thin-walled, bulging sac.

Dissecting Aneurysm

Blood accumulates between tunics of artery and separates them, usually because of degeneration of the tunica media

Arterial Sense Organs

Sensory structures in walls of major vessels that monitor blood pressure and chemistry.

Carotid Sinuses

Baroreceptors in walls of internal carotid artery; monitor blood pressure.

Carotid Bodies

Chemoreceptors near branch of common carotids; monitor blood chemistry.

Aortic Bodies

Chemoreceptors in walls of aortic arch; monitor blood chemistry.

Capillaries

Exchange vessels where gases, nutrients, wastes, and hormones pass between the blood and tissue fluid.

Continuous Capillaries

Capillaries with endothelial cells that have tight junctions, forming a continuous tube with intercellular clefts.

Pericytes

Wrap around capillaries and contain the same contractile protein as muscle; contract and regulate blood flow

Fenestrated Capillaries

Capillaries found in organs that require rapid absorption or filtration; endothelial cells riddled with filtration pores.

Sinusoids

Organs with Irregular blood-filled spaces with large fenestrations; allow proteins and new blood cells to enter circulation.

Capillary Beds

Networks of 10 to 100 capillaries, usually supplied by a single arteriole.

Precapillary Sphincters

Control flow in capillary beds supplied with metarterioles.

Veins

Thin-walled and flaccid vessels with a greater capacity for blood containment than arteries.

Postcapillary Venules

Smallest veins; more porous than capillaries; exchange fluid with surrounding tissues.

Muscular Venules

Receive blood from postcapillary venules; have one or two layers of smooth muscle.

Medium Veins

Veins with a thin tunica media and thick tunica externa; tunica interna forms venous valves.

Varicose Veins

Result from failure of venous valves.

Venous Sinuses

Especially thin-walled veins with large lumens and no smooth muscle; not capable of vasoconstriction.

Large Veins

Veins with smooth muscle in all three tunics; thickest layer is the tunica externa.

Portal System

Blood flows through two consecutive capillary networks before returning to the heart.

Anastomosis

Convergence between two vessels other than capillaries.

Arteriovenous Anastomosis (Shunt)

Artery flows directly into vein, bypassing capillaries.

Arterial Anastomosis

Two arteries merge; provides collateral routes of blood supply.

Blood Flow

Amount of blood flowing through an organ, tissue, or blood vessel in a given time.

Perfusion

Flow per given volume or mass of tissue in a given time.

Hemodynamics

Physical principles of blood flow based on pressure and resistance.

Blood Pressure (BP)

Force that blood exerts against a vessel wall.

Systolic Pressure

Peak arterial BP taken during ventricular contraction.

Diastolic Pressure

Minimum arterial BP taken during ventricular relaxation.

Pulse Pressure

Difference between systolic and diastolic pressure.

Mean Arterial Pressure (MAP)

Average blood pressure that most influences risk level for edema, fainting, atherosclerosis, kidney failure, and aneurysm.

Arteriosclerosis

Stiffening of arteries due to deterioration of elastic tissues of artery walls.

Atherosclerosis

Build up of lipid deposits that become plaques.

Hypertension

High blood pressure; chronic resting BP >140/90.

Hypotension

Chronic low resting BP.

Peripheral Resistance

Opposition to flow that blood encounters in vessels away from the heart.

Blood Viscosity

RBC count and albumin concentration.

Laminar Flow

Flows in layers, faster in center.

Vasoreflexes

Changes in vessel radius.

Vasoconstriction

Smooth muscle of tunica media contracts.

Vasodilation

Smooth muscle relaxes; blood pressure expands vessel.

Vasomotion

Collective term for both vasoconstriction and vasodilation; controlled in part by vasomotor center in medulla oblongata.

Autoregulation

Ability of tissues to regulate their own blood supply.

Vasoactive Chemicals

Substances secreted by platelets, endothelial cells, and perivascular tissue to stimulate vasomotor responses.

Shear Stress

Stimulates endothelial cells to secrete vasodilators.

Reactive Hyperemia

If blood supply cut off then restored, flow increases above normal.

Angiogenesis

Growth of new blood vessels.

Vasomotor Center of Medulla

Exerts sympathetic control over blood vessels throughout the body.

Baroreflex

Automatic, negative feedback response to change in blood pressure.

Chemoreflex

Response to changes in blood chemistry.

Medullary Ischemic Reflex

Automatic response to a drop in perfusion of the brain.

Angiotensin II

Raises blood pressure; potent vasoconstrictor.

Aldosterone

Promotes Na+ retention by the kidneys; supports blood pressure.

Natriuretic Peptides

Secreted by the heart; lower blood pressure by antagonizing aldosterone and promoting vasodilation.

Antidiuretic Hormone (ADH)

Promotes water retention and raises BP; acts as a vasoconstrictor at pathologically high concentrations.

Epinephrine and Norepinephrine

Adrenal and sympathetic catecholamines; cause vasoconstriction in most blood vessels.

Capillary Exchange

Two-way movement of fluid across capillary walls.

Transcytosis

Vesicle-mediated transport moves materials across endothelium.

Blood Hydrostatic Pressure

Drives fluid out of capillary.

Colloid Osmotic Pressure (COP)

Draws fluid into capillary.

Oncotic Pressure

Net COP (blood COP − tissue COP).

Edema

Accumulation of excess fluid in a tissue.

Venous Return

The flow of blood back to the heart.

Thoracic (respiratory) pump

Inhalation expands thoracic cavity.

Cardiac Suction

During contraction of the ventricles, valves are pulled downward and atrial space expands.

Circulatory Shock

Any state in which cardiac output is insufficient to meet body’s metabolic needs.

Cardiogenic Shock

Inadequate pumping of heart.

Low Venous Return (LVR) Shock

Cardiac output low because too little blood returns to heart.

Hypovolemic Shock

Loss of blood volume.

Obstructed Venous Return Shock

Tumor or aneurysm compresses a vein.

Venous Pooling (Vascular) Shock

Long periods of standing, sitting, or widespread vasodilation.

Neurogenic Shock

Loss of vasomotor tone, vasodilation.

Septic Shock

Bacterial toxins trigger vasodilation and increased capillary permeability.

Anaphylactic Shock

Severe immune reaction to antigen, histamine release, generalized vasodilation, increased capillary permeability.

Compensated Shock

Several homeostatic mechanisms bring about spontaneous recovery.

Decompensated Shock

When compensation fails; life-threatening positive feedback loops occur.

Transient Ischemic Attacks (TIAs)

Brief episodes of cerebral ischemia.

Stroke, or Cerebral Vascular Accident (CVA)

Sudden death of brain tissue caused by ischemia.

Unique Response to Hypoxia in Lungs

Pulmonary arteries constrict in diseased area.

Hypertension

Most common cardiovascular disease affecting about 30% of Americans over 50.

Secondary Hypertension

Increased BP is caused by (secondary to) other disease.