Cardiovascular System - Blood vessels Flashcards
What are the components of the vascular wall?
Tunica Externa - outermost coat, consists of squamous epithelium, basement membrane, loose CT and blood vessels
Tunica Media - consists of circular layers of smooth muscle, collagen and elastin
Tunica Interna - innermost, consists of endothelium, basal lamina.
Explain how venous valves prevent backflow.
2 leaflets (thin folds of the tunica intima) jutting out from the wall into the lumen
Blood flowing towards the heart pushes the cusps of the valve open
Cusps of valve close if blood tries to flow in the opposite direction - this prevents back flow of blood.
Explain the roles of arterioles in microvasculature.
Arterioles are small arteries that deliver blood to the arteries
Arterioles control blood flow by contracting or dilating the size of the lumen, tunica media layer contains concentric layers of smooth muscle to do this
Controls blood pressure of blood entering capillary beds as a constant flow is needed so gas exchange can occur.
Have largest peripheral resistance.
Explain the role of venules in microvasculature.
They have thin walls with less smooth muscle and connective tissue compared to arterioles, allowing them to accommodate changes in blood volume without significant changes in pressure.
Venules serve as conduits for blood returning from capillary beds to larger veins and eventually to the heart.
Explain the roles of capillaries in microvasculature.
Capillaries are the smallest and most numerous blood vessels in the body, forming an extensive network that allows for the exchange of gases, nutrients, and waste products between the blood and surrounding tissues.
Their walls are composed of a single layer of endothelial cells. The narrow diameter of capillaries allows red blood cells to pass through in single file, facilitating efficient exchange with surrounding tissues.
Describe the difference between elastic arteries and muscular arteries.
Elastic arteries receive blood directly from the heart. Thin lumen compared to diameter. In between heart contractions, elastic wall recoils to maintain blood pressure and continually moves blood.
Muscular arteries - Walls have lots of smooth muscle so can contract or dilate to change the amount of blood delivered
Sheet of elastin much thinner than in elastic arteries and is found in-between the tunica media and tunica interna in the internal elastic layer.
Name the major arteries and veins of the systemic circulation system.
Arteries - aorta, coronary, renal, brachiocephalic, carotid, pulmonary
Veins - superior and inferior vena cava, pulmonary, hepatic, renal, portal
What are the 3 types of capillaries?
Continuous - Endothelial cells provide a complete continuous lining - linked by tight junctions
Basal lamina is also continuous. Caveolae transports substances across the endothelium. Pericytes are associated with endothelium and provide stability.
Fenestrated - Have membranes that act as diaphragms
Basement membrane is continuous.
Discontinuous -
Gaps in endothelial cells are larger than in fenestrated capillaries
Basement membrane is discontinuous.
What is atherosclerosis?
Infiltration of lipid material into tunica intima
Reduces lumen diameter
Forerunner of heart attacks and strokes
Build up of fibrous plaques .
