The Cardiovascular System: Blood Vessels and Circulation

Flashcards covering the structure and function of blood vessels, hemodynamics, blood pressure regulation, and fetal circulation from Chapter 20.

Arteries

Blood vessels that conduct blood away from the heart.

Veins

Blood vessels that conduct blood toward the heart.

Lumen

The hollow internal space of a blood vessel through which blood flows.

Vasa vasorum

Small vessels that supply blood to the walls of larger arteries and veins.

Tunica Intima

The innermost layer of a blood vessel wall composed of epithelial and connective tissue, including the endothelium and internal elastic membrane.

Endothelium

The specialized epithelial layer of the tunica intima that lines the interior of all blood vessels.

Tunica Media

The middle layer of a blood vessel wall, composed of smooth muscle and supported by the external elastic membrane.

Tunica Externa

The outermost layer of a blood vessel wall made of connective tissue that helps hold the vessel in position.

Vasoconstriction

The narrowing of a blood vessel lumen resulting from the contraction of the smooth muscle in the tunica media.

Vasodilation

The widening of a blood vessel lumen as the smooth muscle in the tunica media relaxes.

Elastic arteries

Arteries located close to the heart that contain significant elastic fibers, allowing them to expand and recoil.

Muscular arteries

Medium-sized arteries with a thick tunica media capable of significant vasoconstriction.

Arterioles

Tiny arterial vessels that lead into capillaries and are primary sites for the regulation of blood pressure.

Continuous capillary

A capillary with a complete endothelial lining and tight junctions; examples include the capillaries forming the blood brain barrier.

Fenestrated capillary

A permeable capillary containing pores (fenestrations) and tight junctions, commonly found in the small intestine.

Sinusoid capillary

Capillaries with intercellular gaps and an incomplete basement membrane, found in the liver, spleen, and lymph nodes.

Metarteriole

A vessel with characteristics of both an arteriole and a capillary that supplies a capillary bed and can serve as a vascular shunt.

Precapillary sphincter

Small circular smooth muscle cells that regulate the flow of blood into a capillary bed.

Thoroughfare channel

The distal portion of a metarteriole that allows blood to drain into a venule.

Venules

Small vessels, ranging from $8$ to $100$ microns in diameter, that join multiple capillaries and are the primary site of diapedesis.

Diapedesis

Also known as emigration, it is the process by which white blood cells pass through the walls of capillaries or venules.

Venous reserve

The volume of blood contained in the systemic veins (about $64\%$ of total blood) that can be redistributed to other parts of the body.

Blood flow

The volume of blood per unit of time passing through a vessel, tissue, or organ.

Resistance

Any factors, such as blood viscosity or vessel length and diameter, that slow down the flow of blood.

Blood pressure

The hydrostatic pressure of a fluid against the vessel wall or heart chambers, measured in $mm\,Hg$.

Systolic pressure

The arterial pressure resulting from the contraction of the ventricles.

Diastolic pressure

The arterial pressure during the period of ventricular relaxation.

Pulse Pressure (PP)

The difference between systolic and diastolic pressure, calculated as $\text{Systolic} - \text{Diastolic} = PP$.

Mean Arterial Pressure (MAP)

The average pressure of blood in the arteries, calculated using the formula $MAP = \text{diastolic BP} + (PP/3)$.

Ischemia

A restriction in blood supply to tissues, which becomes a clinical concern if MAP falls below $60\,mm\,Hg$ for an extended period.

Korotkoff sounds

The sounds a health professional listens for with a stethoscope while measuring blood pressure with a sphygmomanometer.

Compliance

The ability of a blood vessel or compartment to expand to accommodate more content.

Skeletal muscle pump

A mechanism involving the contraction of skeletal muscles to push blood in the veins back toward the heart.

Respiratory pump

A mechanism where inhalation causes blood to flow into the thoracic cavity and exhalation speeds blood flow into the heart.

Capillary hydrostatic pressure

The pressure of blood within the capillaries that pushes fluid out into the interstitial space.

Blood colloid osmotic pressure

The pressure exerted by large plasma proteins that pulls water from the tissues back into the vascular capillaries.

Baroreceptor reflexes

Neural mechanisms in the aortic and carotid sinuses that monitor blood pressure and help maintain vascular homeostasis.

Antidiuretic hormone (ADH)

Also known as vasopressin, this hormone from the brain helps restore blood volume and pressure through water retention and vasoconstriction.

Atrial natriuretic hormone (ANH)

A hormone secreted by atrial cells in the heart that promotes the loss of sodium and water to reduce blood volume and pressure.

Myogenic response

A localized autoregulatory process where a vessel's smooth muscle contracts in response to stretching to maintain consistent perfusion.

Hypertension

A clinical condition of high blood pressure, typically defined as a reading of $140/90\,mm\,Hg$ or higher.

Hypovolemic shock

Circulatory shock caused by hemorrhage or extensive fluid loss, resulting in a rapid, weak pulse.

Cardiogenic shock

A type of shock resulting from the heart's inability to maintain cardiac output, often caused by a myocardial infarction (MI).

Hemangioblasts

Embryonic mesoderm cells that differentiate into angioblasts and blood islands to form blood vessels.

Foramen ovale

An opening in the interatrial septum that allows blood to flow from the right atrium to the left atrium in the fetal heart.

Ductus arteriosus

A fetal vessel connecting the pulmonary trunk to the aorta, allowing most blood to skip the lungs.

Ductus venosus

A branch from the fetal umbilical vein that allows oxygenated blood to head directly toward the fetal heart.