Blood Vessels & Circulation
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69 Terms
What are the three major types of blood vessels?
Arteries, capillaries, and veins
Which vessels carry blood away from the heart?
Arteries
Which vessels carry blood toward the heart?
Veins
What is the primary function of capillaries?
Exchange of nutrients, gases, hormones, and wastes
Which layer of blood vessel is in direct contact with blood?
Tunica intima
What type of epithelium forms the endothelium?
Simple squamous epithelium
What is the function of the endothelium?
Selective permeability and regulation of vessel diameter
Which vessel layer contains smooth muscle?
Tunica media
Which vessel layer controls vasoconstriction and vasodilation?
Tunica media
What is vasomotion?
Changes in vessel diameter caused by smooth muscle contraction or relaxation
Which vessel layer contains connective tissue that anchors the vessel?
Tunica externa
What are vasa vasorum?
Small blood vessels that supply large blood vessel walls
Why are arteries called resistance vessels?
They resist high blood pressure due to strong elastic walls
Which arteries are the most elastic?
Large arteries
What allows arteries to stretch and recoil?
Elastic tissue in their walls
What are small arteries called?
Arterioles
Which type of capillary is most common?
Continuous capillaries
Which capillary type has tight junctions?
Continuous capillaries
What are pericytes?
Contractile cells that regulate capillary blood flow
Which capillary type contains fenestrations?
Fenestrated capillaries
Where are fenestrated capillaries commonly found?
Kidneys and small intestine
Which capillary type is the most permeable?
Sinusoid capillaries
Where are sinusoid capillaries found?
Liver, spleen, and bone marrow
Which capillaries allow proteins and blood cells to pass through?
Sinusoids
What is a capillary bed?
A network of capillaries supplied by a metarteriole
What is a thoroughfare channel?
A direct pathway from arteriole to venule
What controls blood flow into capillary beds?
Precapillary sphincters
What happens when precapillary sphincters open?
Blood enters capillaries
What happens when precapillary sphincters close?
Blood bypasses capillaries through the thoroughfare channel
Approximately what percentage of capillaries are closed at rest?
About 75%
Why are veins called capacitance vessels?
They contain most of the body's blood volume
How much of the body's blood is found in veins?
About 54%
What are the smallest veins called?
Postcapillary venules
Why are postcapillary venules important?
They exchange fluid with tissues
What structures prevent blood from flowing backward in veins?
Venous valves.
What is the skeletal muscle pump?
Contraction of skeletal muscles that pushes blood toward the heart
What are venous sinuses?
Thin-walled veins with large lumens and no smooth muscle
What is venous return?
Flow of blood back to the heart
What is the most important force promoting venous return?
Blood pressure
How does the respiratory pump aid venous return?
Inhalation lowers thoracic pressure and pushes blood toward the heart
What is venous pooling?
Blood accumulation in veins due to inactivity
Why can prolonged standing cause dizziness?
Reduced venous return lowers cardiac output
What is blood pressure?
Force exerted by blood against vessel walls
What is systolic pressure?
Pressure during ventricular contraction
What is diastolic pressure?
Pressure during ventricular relaxation
What is a normal blood pressure reading?
Approximately 120/75–80 mm Hg
What is hypertension?
Blood pressure greater than 140/90 mm Hg
Why is hypertension called the "silent killer"?
It causes damage before symptoms appear
What is hypotension?
Chronically low blood pressure
What do carotid sinus baroreceptors monitor?
Blood pressure
What do carotid body chemoreceptors monitor?
O₂, CO₂, and pH
What do aortic bodies monitor?
O₂, CO₂, and pH
What is the most important mechanism of capillary exchange?
Diffusion
Which substances diffuse out of capillaries?
Oxygen and glucose
Which substances diffuse into capillaries?
Carbon dioxide and wastes
What pressure pushes fluid out of capillaries?
Hydrostatic pressure
What pressure pulls fluid into capillaries?
Colloid osmotic pressure
Where does filtration occur?
Arterial end of capillaries
Where does reabsorption occur?
Venous end of capillaries
What is edema?
Excess accumulation of fluid in tissues
What are the three major causes of edema?
Increased filtration, reduced absorption, blocked lymphatics
What is a varicose vein?
Enlarged vein caused by valve failure and blood pooling
What is circulatory shock?
Cardiac output insufficient to meet body needs
What is the most common type of shock?
Hypovolemic shock
What is a transient ischemic attack (TIA)?
Temporary cerebral ischemia
What is a stroke (CVA)?
Death of brain tissue due to loss of blood flow
What is an aneurysm?
Weak bulging area in an artery or heart wall
What is the most common cause of aneurysms?
Atherosclerosis and hypertension
What is deep vein thrombosis (DVT)?
A blood clot in a deep vein that may travel to the lungs