What is the function of smooth muscle in arterioles?
Function. Vascular smooth muscle contracts or relaxes to change both the volume of blood vessels and the local blood pressure, a mechanism that is responsible for the redistribution of the blood within the body to areas where it is needed (i.e. areas with temporarily enhanced oxygen consumption).
Why does an artery need a layer of smooth muscle?
These include arteries such as the femoral and coronary arteries. The walls of these arteries have lots of smooth muscle, which means that they are able to contract or relax (dilate) to change the amount of blood delivered, as needed. There is a well defined circular layer of smooth muscle in the tunica media.
When smooth muscle contracts What happens to blood vessel diameter?
When vascular smooth muscle contracts, the diameter of the blood vessel becomes smaller. This is called vasoconstriction. You just studied 24 terms!
What is it called when the muscles of an artery contract and the lumen is reduced in size?
Specifically in arteries, vasoconstriction decreases blood flow as the smooth muscle in the walls of the tunica media contracts, making the lumen narrower and increasing blood pressure.
What happens when smooth muscles contract?
When made to contract, the smooth muscle cells shorten, thereby propelling the luminal contents of the organ, or the cell shortening varies the diameter of a tube to regulate the flow of its contents. There are also bundles of smooth muscle cells attached to the hairs of the skin and to the iris and lens of the eye.
Is the heart smooth muscle?
Cardiac muscle cells are located in the walls of the heart, appear striated, and are under involuntary control. Smooth muscle fibers are located in walls of hollow visceral organs, except the heart, appear spindle-shaped, and are also under involuntary control.
How many layers of tissue does an artery have?
The wall of an artery consists of three layers. The innermost layer, the tunica intima (also called tunica interna), is simple squamous epithelium surrounded by a connective tissue basement membrane with elastic fibers. The middle layer, the tunica media, is primarily smooth muscle and is usually the thickest layer.
What kind of tissue prevents veins from collapsing?
The tunica externa is often thicker in veins to prevent collapse of the blood vessel and provide protection from damage since veins may be superficially located.
What tissues are likely to be found in arteries?
Each artery is a muscular tube lined by smooth tissue and has three layers:
- The intima, the inner layer lined by a smooth tissue called endothelium.
- The media, a layer of muscle that lets arteries handle the high pressures from the heart.
- The adventitia, connective tissue anchoring arteries to nearby tissues.
How can the stretching of smooth muscle lead to smooth muscle contraction?
The triggers for smooth muscle contraction include hormones, neural stimulation by the ANS, and local factors. In certain locations, such as the walls of visceral organs, stretching the muscle can trigger its contraction (the stretch-relaxation response).
Which blood vessels contain smooth muscle?
Arterioles provide blood to the organs and are chiefly composed of smooth muscle. The autonomic nervous system influences the diameter and shape of arterioles.
What blood vessels do not have smooth muscle?
Cerebral arteries and veins: These arteries are rather thin-walled for their caliber, with a well-developed internal elastica and virtually no elastic fibers in the rest of the vascular wall. The veins have a thin wall devoid of smooth muscle cells.
What are the 4 major arteries?
The right coronary artery, the left main coronary, the left anterior descending, and the left circumflex artery, are the four major coronary arteries.
Which blood vessels have the thickest walls?
Arteries and arterioles have thicker walls than veins and venules because they are closer to the heart and receive blood that is surging at a far greater pressure (Figure 2). Each type of vessel has a lumen—a hollow passageway through which blood flows.
What are the thinnest veins called?
Capillaries. Capillaries are the shortest, narrowest, and thinnest blood vessels. They connect arterioles to venules to complete the circuit. Capillaries consist only of endothelium with some connective tissue binding the cells.