Bio 255 Exam Questions and Answers

Bio 255 Exam Questions and Answers How many layers do blood vessels contain? 3 Tunica externa consists of epithelial cells, connective tissue, elastic fibers Tunica media consists of elastic fibers and smooth muscle (usually the largest layer) tunica intima (interna) endothelial cells, connective tissue Elastic arteries largest arteries by diameter, contain more elastic fibers than smooth muscle Muscular arteries (distributing arteries) contain large amounts of smooth muscle Most arteries fall into this category arterioles smallest in diameter, slightly larger than diameter of one red blood cell, attached to capillary beds, pre-capillary sphincter (chemoreceptor for oxygen) used to control blood flow through the systemic capillary capillary diameter about the size of one red blood cell capillary action site of the exchange of fluids and nutrients/waste; only have tunica intima continuous capillaries overlapping endothelial cells; filtration cleft; only small molecules can fit through; diffusion and bulk flow endocytosis; found in systemic capillaries fenestrated capillaries have pores in vessel wall in addition to filtration cleft; found in kidneys, intestines, and endocrine glands sinusoidal capillaries larger filtration pores; large molecules can filter; found in the liver leaky capillaries Veins Blood vessels that carry blood back to the heart, have valves Veins need what to create pressure to assist in returning blood to the heart. vasoconstriction, valves, skeletal muscle pump, respiratory pump, and cardiac suction Venuels smallest veins, attach to capillary bed medium sized veins slightly larger diameter veins