chapter 19

Tunica intima

Innermost layer of blood vessels in direct contact with blood in lumen, containing endothelium.

Tunica media

Middle layer of blood vessels, composed of circular smooth muscle and elastin, controlling vessel diameter.

Tunica externa

Outermost layer of blood vessels made of collagen fibers, reinforcing and anchoring vessels.

Atherosclerosis

A condition characterized by a buildup of fatty plaques (atheromas) in arterial walls, reducing lumen size.

Arteriosclerosis

Hardening, thickening, and loss of elasticity in arterial walls, leading to reduced blood flow.

Aneurysm

A balloon-like outpocketing of an artery wall that is at risk for rupture.

Capillaries

Smallest blood vessels consisting of only tunica intima, facilitating the exchange of materials between blood and interstitial fluid.

Continuous capillaries

Most common type of capillary, found in skin and muscles, characterized by a continuous endothelium.

Fenestrated capillaries

Capillaries with pores that allow greater permeability, found in areas of active absorption such as the kidneys.

Sinusoid capillaries

Highly permeable capillaries with large openings, found in the liver, spleen, and bone marrow.

Venules

Small veins that converge to form veins, postcapillary venules are the smallest and very permeable to fluids and white blood cells.

Veins

Blood vessels that return blood to the heart, with thinner walls and larger lumens than arteries, containing valves to prevent backflow.

Blood pressure (BP)

The force exerted by circulating blood on the walls of blood vessels, measured in mm Hg.

Systolic pressure

The pressure in the arteries during ventricular contraction.

Diastolic pressure

The pressure in the arteries during ventricular relaxation.

Mean arterial pressure (MAP)

The average pressure in a person's arteries during one cardiac cycle, important for assessing blood flow to organs.

Net Filtration Pressure (NFP)

The difference between the pressures promoting filtration and forces opposing it in capillary hemodynamics.

Peripheral resistance

The resistance of the arteries to blood flow, affecting blood pressure and flow rates.

Baroreceptors

Stretch receptors located in major arteries that sense changes in blood pressure and help regulate it.

Baroreceptor location

Aortic arch, coratid sinus and kidney

Chemoreceptors

Receptors that respond to changes in blood chemistry (e.g., CO2, O2), impacting blood flow and respiration.

Hypertension

Chronically elevated blood pressure, classified as systolic >140 mm Hg or diastolic >90 mm Hg.

Venous return

The process by which blood is transported back to the heart, aided by mechanisms like the muscular and respiratory pumps.

Circulatory shock

Condition when blood vessels are inadequately filled and blood cannot circulate effectively to meet tissue needs.

Hypovolemic shock

A type of shock resulting from large-scale fluid or blood loss, leading to decreased blood volume.

Vascular shock

Shock due to extreme vasodilation that compromises normal circulation, despite normal blood volume.

Umbilical vein

Carries oxygenated blood from the placenta to the fetus.

Ductus venosus

Fetal shunt that bypasses the liver, directing oxygenated blood to the heart.

Foramen ovale

Fetal shunt that allows blood to flow from the right atrium to the left atrium, bypassing the lungs.

Ductus arteriosus

Fetal shunt connecting the pulmonary trunk to the aorta, allowing blood to bypass the lungs.

Umbilical arteries

Carry deoxygenated blood from the fetus back to the placenta.