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Vascular system
Chapter 15 definitions
| Term | Definition |
|---|---|
| Tunica intima | Innermost layer of a vein or artery; consists of simple squamous epithelium; smooth surface keeps blood flowing freely; produces chemicals that cause vessels to dilate or constrict |
| Endothelium | Simple squamous epithelium of the tunica intima |
| Tunica media | Middle layer of veins and arteries, also the thickest layer; Composed of smooth muscle and elastic tissue; innervated by the autonomic nervous system which allows the blood vessel to change diameter |
| Tunica externa | Outer layer of veins and arteries; strong, flexible, fibrous connective tissue; supports and protects the blood vessel; thickest layer in veins, a little thinner than the middle layer in arteries |
| Aneurysm | Formed when a portion of the arterial wall weakens, blood inside the artery pushes against the weakened area, causing it to bulge |
| Arterioles | Smallest arteries; also called resistance vessels; connected to capillaries by metarterioles |
| Arteries | Carry oxygenated blood away from the heart to the body |
| Veins | Carry deoxygenated blood from the body to the heart |
| Conducting arteries | The body's largest arteries; also called elastic arteries; examples are the aorta, common carotid artery, subclavian artery |
| Distributing arteries | Carry blood to specific organs and areas of the body; also called muscular arteries; examples are brachial, femoral, and renal arteries |
| Capacitance vessels | Veins; so named because of their great capacity for storing blood |
| Exchange vessels | Capillaries; so named because nutrients, wastes, and hormones are tranferred between blood and tissues within them |
| Capillary beds | Networks of capillaries |
| Microcirculation | What is formed when capillaries connect arterioles to venules |
| Precapillary sphincter | The beginning of each capillary bed that regulates the flow of blood into the network |
| Sinusoid | Unique capillary of the liver, bone marrow, and spleen; irregular, blood-filled space that is more permeable to allow for the passage of proteins and blood cells |
| Diffusion | Most important mechanism of capillary exchange; substances move from an area of greater to lesser concentration |
| Filtration | Method of capillary exchange that occurs close to the arterial side of the capillary bed; higher pressure pushes plasma & dissolved nutrients into the fluid of the surrounding tissues |
| Colloid osmotic pressure | Albumin in the blood pulls tissue fluid & the cell's waste products into the capillaries |
| Edema | Occurs when fluid filters out of the capillaries faster than it's reabsorbed; appears as swelling in the ankles, fingers, abdomen, or face |
| Increased capillary filtration | Cause of edema; rise in capillary pressure causes a rise in filtration; causes include kidney failure, poor venous return from inactivity, or failure of the right ventricle |
| Reduced capillary reabsorption | Deficiency of albumin, causing edema; may result from liver disease, severe burns, and kidney disease |
| Obstructed lymphatic drainage | Cause of edema; obstruction of the lymphatic system causing fluid to accumulate |
| Portal systems | Blood flows through 2 networks of capillaries; occur in the kidneys and liver |
| Anastomosis | 2 vessels join together; provides alternative routes of blood flow in case a vessel becomes obstructed |
| Pulmonary circulation | Begins at the right ventricle and involves the circulation of blood through the lungs |
| Systemic circulation | Begins at the left ventricle and involves the circulation of blood through the body |
| Superior mesenteric artery | Supplies most of the small interstine and part of the large intestine |
| Inferior mesenteric artery | Supplies part of the large intestine |
| External carotid artery | Supplies most of the external head structures |
| Internal carotid artery | Enters the cranial cavity and supplies the orbits and 80% of the cerebrum |
| Basilar artery | The 2 vertebral arteries unite on the undersurface of the brainstem |
| Circle of Willis | Anastomoses that create a circle of arteries at the base of the brain; helps ensure that the brain receives an adequate supply of blood |
| Internal jugular vein | Drains most of the blood from the brain |
| Cephalic vein | Frequent site for the administration of intravenous fluids |
| Median cubital | Most common site for drawing blood |
| Great saphenous vein | Longest vein in the body; frequently harvested for use as grafts in coronary artery bypass surgery |
| External jugular vein | Drains blood from the scalp, facial muscles, and other superficial structures |
| Pressure gradient | The difference in pressure between 2 structures |
| Systolic pressure | As the left ventricle contracts, typical normal pressure of 110 mm Hg |
| Diastolic pressure | The left ventricle relaxes, the pressure drops to an average of 70 mm Hg |
| Blood pressure | The force exerted by the blood against a vessel wall; determined by cardiac output, blood volume, and resistance |
| Peripheral resistance | The opposition to flow resulting from the friction of moving blood against the vessel walls |
| Pulse pressure | The difference between systolic and diastolic pressure |
| Vasomotion | Adjusting the diameter of blood vessels |
| Vasoconstriction | Reduction of the diameter of a vessel that increases the resistance to blood flow |
| Vasodilation | Increase in vessel diameter that decreases resistance to blood flow |
| Vasomotor center | An area of the medulla in the brain that sends impulses via the autonomic nervous system to alter blood vessel diameter and, therefore, blood pressure |
| Baroreceptors | In the carotid sinus and aortic arch that detect changes in blood pressure and transmit signals along the gloospharangeal and vagus nerves to the cardiac control center and the vasomotor center |
| Skeletal muscle pump | Muscles surrounding leg veins aid in venous return |
| Respiratory pump | The process of breathing promotes the flow of venous blood in the thoracic and abdominal cavities |
| Vena cava | The body's cheif vein, which serves to return blood to the heart |
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