Blood Vessels Flashcards
What is a LUMEN?
a hollow passageway through which blood flows.
Why do arteries and arterioles have thicker walls than veins?
they are closer to the heart and receive blood that is surging at a far greater pressure
What are the walls of arteries and veins mostly composed of?
living cells and their products (including collagenous and elastic fibers); the cells require nourishment and produce waste.
In larger arteries, there is a thick, distinct layer of elastic fibers known as the what?
the internal elastic membrane (also called the internal elastic lamina)
The internal elastic membrane (also called the internal elastic lamina) is located where?
at the boundary with the tunica media
What are the 3 Tunics called?
Tunic interna, tunic media, and tunic externa
Specifically in arteries, what decreases blood flow as the smooth muscle in the walls of the tunica media contracts, making the lumen narrower and increasing blood pressure?
Vasoconstriction
What happens during vasodilation?
increased blood flow as the smooth muscle relaxes, allowing the lumen to widen and blood pressure to drop.
vasoconstriction and vasodilation are regulated in part by small vascular nerves, known as ________ that run within the walls of blood vessels.
nervi vasorum, or “nerves of the vessel”
Appearing wavy in slides (microscope), ______ separates the tunica media from the outer tunica externa in larger arteries.
the external elastic membrane (also called the external elastic lamina)
Besides being innervated by the nervi vasorum, what else controls the vaso consticion/dilation of the blood vessels?
Hormones and local chemicals
What is the outer tunic, the tunica externa (also called the tunica adventitia)?
It is a substantial sheath of connective tissue composed primarily of collagenous fibers.
What is a blood vessel that conducts blood away from the heart.
An artery
What type of artery is close to the heart and has the thickest walls, containing a high percentage of elastic fibers in all three of the tunics.
an elastic artery
Why is an elastic artery is also known as a conducting artery?
because the large diameter of the lumen enables it to accept a large volume of blood from the heart and conduct it to smaller branches.
What is a very small artery that leads to a capillary.
Arteriole
With a lumen averaging 30 micrometers or less in diameter, ________ are critical in slowing down—or resisting—blood flow and, thus, causing a substantial drop in blood pressure.
arterioles
What are the primary mechanisms for distribution of blood flow.
The vasoconstriction and vasodilation in the arterioles.
Why are arterioles so important in terms of blood flow?
They are the primary site of both resistance and regulation of blood pressure.
The exchange of gases and other substances that occur in the capillaries between the blood and the surrounding cells and their tissue fluid (interstitial fluid) is what?
A process called perfusion.
A microscopic channel that supplies blood to the tissues themselves is called a _____.
Capillary
Flow through capillaries is often described as ______.
a microcirculation, just big enough form an erythrocyte to get through.
What are three major types of capillaries?
Continuous, fenestrated, and sinusoid capillaries. All differ according to their “leakiness”.
What is a type of vessel that has structural characteristics of both an arteriole and a capillary?
Metarteriole
Circular smooth muscle cells that surround the capillary at its origin with the metarteriole, tightly regulate the flow of blood from a metarteriole to the capillaries it supplies.
The precapillary sphincters
What is an extremely small vein, generally 8–100 micrometers in diameter.
A venule
What is a vein?
A blood vessel that conducts blood toward the heart.
What is the capacity to distend (expand) readily to store a high volume of blood, even at a low pressure called?
capacitance
What are capacitance vessels?
The large lumens and relatively thin walls of veins make them far more distensible than arteries.
The volume of blood that is approximately 21 percent of the venous blood is located in venous networks within the liver, bone marrow, and integument is called what?
The venous reserve
Refers to the movement of blood through a vessel, tissue, or organ, and is usually expressed in terms of volume of blood per unit of time.
Blood flow
This phenomenon discusses the factors that impede or slow blood flow?
Resistance
The force exerted by blood upon the walls of the blood vessels or the chambers of the heart.
Blood pressure
