Chapter 19

The Cardiovascular System: Blood Vessels:

Part A

Blood Vessels

Delivery system of dynamic structures that begins and ends at heart

Arteries: carry blood away from heart; oxygenated except for pulmonary circulation and umbilical vessels of fetus

Capillaries: contact tissue cells; directly serve cellular needs

Veins: carry blood toward heart

Structure of Blood Vessel Walls

Lumen

Central blood-containing space

Three wall layers in arteries and veins

Tunica intima, tunica media, and tunica externa

Capillaries

Endothelium with sparse basal lamina

Tunics

Tunica intima

Endothelium lines lumen of all …show more content…

t backflow of blood

Most abundant in veins of limbs

Venous sinuses: flattened veins with extremely thin walls (e.g., coronary sinus of the heart and dural sinuses of the brain)

Vascular Anastomoses

Interconnections of blood vessels

Arterial anastomoses provide alternate pathways (collateral channels) to given body region

Common at joints, in abdominal organs, brain, and heart; none in retina, kidneys, spleen

Vascular shunts of capillaries are examples of arteriovenous anastomoses

Venous anastomoses are common

Physiology of Circulation: Definition of Terms

Blood flow

Volume of blood flowing through vessel, organ, or entire circulation in given period

Measured as ml/min

Equivalent to cardiac output (CO) for entire vascular system

Relatively constant when at rest

Varies widely through individual organs, based on needs

Physiology of Circulation: Definition of Terms

Blood pressure (BP)

Force per unit area exerted on wall of blood vessel by blood

Expressed in mm Hg

Measured as systemic arterial BP in large arteries near heart

Pressure gradient provides driving force that keeps blood moving from higher to lower pressure areas

Physiology of Circulation: Definition of Terms

Resistance (peripheral resistance)

Opposition to flow

Measure of amount of