Any blood that accumulates in a vein will increase the pressure within it, which can then be reflected back into the smaller veins, venules, and eventually even the capillaries. Increased pressure will promote the flow of fluids out of the capillaries and into the interstitial fluid. The presence of excess tissue fluid around the cells leads to a condition called edema.
Most people experience a daily accumulation of tissue fluid, especially if they spend much of their work life on their feet like most health professionals.
However, clinical edema goes beyond normal swelling and requires medical treatment. Edema has many potential causes, including hypertension and heart failure, severe protein deficiency, renal failure, and many others.
In order to treat edema, which is a sign rather than a discrete disorder, the underlying cause must be diagnosed and alleviated. Figure 7. Varicose veins are commonly found in the lower limbs. Edema may be accompanied by varicose veins, especially in the superficial veins of the legs. This disorder arises when defective valves allow blood to accumulate within the veins, causing them to distend, twist, and become visible on the surface of the integument.
Varicose veins may occur in both sexes, but are more common in women and are often related to pregnancy. More than simple cosmetic blemishes, varicose veins are often painful and sometimes itchy or throbbing. Without treatment, they tend to grow worse over time.
The use of support hose, as well as elevating the feet and legs whenever possible, may be helpful in alleviating this condition. Laser surgery and interventional radiologic procedures can reduce the size and severity of varicose veins. Severe cases may require conventional surgery to remove the damaged vessels. As there are typically redundant circulation patterns, that is, anastomoses, for the smaller and more superficial veins, removal does not typically impair the circulation.
There is evidence that patients with varicose veins suffer a greater risk of developing a thrombus or clot. In addition to their primary function of returning blood to the heart, veins may be considered blood reservoirs, since systemic veins contain approximately 64 percent of the blood volume at any given time. Their ability to hold this much blood is due to their high capacitance , that is, their capacity to distend expand readily to store a high volume of blood, even at a low pressure.
The large lumens and relatively thin walls of veins make them far more distensible than arteries; thus, they are said to be capacitance vessels. When blood flow needs to be redistributed to other portions of the body, the vasomotor center located in the medulla oblongata sends sympathetic stimulation to the smooth muscles in the walls of the veins, causing constriction—or in this case, venoconstriction. This increases pressure on the blood within the veins, speeding its return to the heart.
As you will note in the image above, approximately 21 percent of the venous blood is located in venous networks within the liver, bone marrow, and integument. This volume of blood is referred to as venous reserve. Vascular surgery is a specialty in which the physician deals primarily with diseases of the vascular portion of the cardiovascular system. This includes repair and replacement of diseased or damaged vessels, removal of plaque from vessels, minimally invasive procedures including the insertion of venous catheters, and traditional surgery.
Following completion of medical school, the physician generally completes a 5-year surgical residency followed by an additional 1 to 2 years of vascular specialty training. Vascular technicians are specialists in imaging technologies that provide information on the health of the vascular system. They may also assist physicians in treating disorders involving the arteries and veins.
This profession often overlaps with cardiovascular technology, which would also include treatments involving the heart. Although recognized by the American Medical Association, there are currently no licensing requirements for vascular technicians, and licensing is voluntary. The United States Bureau of Labor projects this profession to grow by 29 percent from to Blood pumped by the heart flows through a series of vessels known as arteries, arterioles, capillaries, venules, and veins before returning to the heart.
Arteries transport blood away from the heart and branch into smaller vessels, forming arterioles. Arterioles distribute blood to capillary beds, the sites of exchange with the body tissues. Capillaries lead back to small vessels known as venules that flow into the larger veins and eventually back to the heart. The arterial system is a relatively high-pressure system, so arteries have thick walls that appear round in cross section.
The venous system is a lower-pressure system, containing veins that have larger lumens and thinner walls. They often appear flattened. Arteries, arterioles, venules, and veins are composed of three tunics known as the tunica intima, tunica media, and tunica externa.
Capillaries have only a tunica intima layer. The tunica intima is a thin layer composed of a simple squamous epithelium known as endothelium and a small amount of connective tissue. The tunica media is a thicker area composed of variable amounts of smooth muscle and connective tissue. It is the thickest layer in all but the largest arteries. The tunica externa is primarily a layer of connective tissue, although in veins, it also contains some smooth muscle.
Blood flow through vessels can be dramatically influenced by vasoconstriction and vasodilation in their walls. Answer the question s below to see how well you understand the topics covered in the previous section. Skip to main content. Search for:. Structure and Function of Blood Vessels Learning Objectives By the end of this section, you will be able to: Compare and contrast the three tunics that make up the walls of most blood vessels Distinguish between elastic arteries, muscular arteries, and arterioles on the basis of structure, location, and function Describe the basic structure of a capillary bed, from the supplying metarteriole to the venule into which it drains Explain the structure and function of venous valves in the large veins of the extremities.
Disorders of the Cardiovascular System: Edema and Varicose Veins Despite the presence of valves and the contributions of other anatomical and physiological adaptations we will cover shortly, over the course of a day, some blood will inevitably pool, especially in the lower limbs, due to the pull of gravity.
Careers in Action: Vascular Surgeons and Technicians Vascular surgery is a specialty in which the physician deals primarily with diseases of the vascular portion of the cardiovascular system. Visit this site to learn more about vascular surgery.
Visit this site to learn more about vascular technicians. Critical Thinking Questions Arterioles are often referred to as resistance vessels. Cocaine use causes vasoconstriction.
Is this likely to increase or decrease blood pressure, and why? A blood vessel with a few smooth muscle fibers and connective tissue, and only a very thin tunica externa conducts blood toward the heart.
Blood vessels are essential for transporting blood around the body. The heart and blood vessels make up the cardiovascular system. This system contains a complex network of vessels with various structures and functions. In this article, we discuss the differences between arteries and veins. We also outline different types of blood vessels and how they work as a part of the cardiovascular system.
Arteries and veins are types of blood vessels that transport blood around the body. Arteries carry blood away from the heart, while veins return it. Blood vessels form two systems going to and from the heart. These two systems form the blood circulatory system. The systemic arteries transport oxygen-rich blood from the left ventricle to the rest of the body.
Afterward, the blood that is now low in oxygen is collected in systemic veins and travels to the right atrium. Pulmonary arteries transport low oxygen blood from the right ventricle to the lungs. Pulmonary veins then transport oxygen-rich blood back to the heart through the left atrium. Capillaries are a third type of blood vessel in the body. They carry blood between arteries and veins.
There are three types of arteries:. Elastic arteries are the large vessels coming out of the heart. For example, they include the pulmonary artery and the aorta. The aorta is the main artery carrying blood away from the heart.
The heart forcefully pumps blood out to keep it moving around the body. Elastic arteries must be flexible to handle surges of blood. The other system, the systemic vessels, carries blood from the left ventricle to the tissues in all parts of the body and then returns the blood to the right atrium.
Based on their structure and function, blood vessels are classified as either arteries , capillaries , or veins. Arteries carry blood away from the heart. Pulmonary arteries transport blood that has a low oxygen content from the right ventricle to the lungs. Systemic arteries transport oxygenated blood from the left ventricle to the body tissues.
Blood is pumped from the ventricles into large elastic arteries that branch repeatedly into smaller and smaller arteries until the branching results in microscopic arteries called arterioles. The arterioles play a key role in regulating blood flow into the tissue capillaries. About 10 percent of the total blood volume is in the systemic arterial system at any given time. 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. What are the different types of arteries? What are the different types of veins? Artery and vein diagram. Anatomy of veins and arteries. The cardiovascular system. The takeaway.
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