Circulation

tunica externa is made up of

collagen and elastin and nuerons

what is vasa vasarum

small vessels on the tunica externa supplying nutrients to large vessels that can not through diffusion

What is tunica externa made up of

simple squamous epithelium

What is tunica media?

middle layer of smooth muscle in a vessel that constricts or dilates and controls flow

What controls vasoconstriction/dilation

Norepinephrine (NE) and local factors (o2, pH)

How do arteries move blood? (high to low pressure) (pressure reservoir)

The pressure from the heart causes the artery walls to expand at first and “rebound” or contract to push it forward (elastic recoil)

Size of the arteries largest to smallest

Elastic (conducting) to muscular (distributing) to arterioles

Characteristics of Elastic Arteries

absorb lots of pressure, large, elastic and strong, example is aorta

Characteristic of Muscular Arteries

large tunica media, carry blood to specific organs, less elastin, more smooth muscle

Characteristics of Arterioles

smallest arteries, smallest have no tunica externa, constantly changing diameter due to local factors (end in capillaries)

What are the three types of capillaries?

continuous, fenestrated, and sinusodial

continuous capillary

most common, tightly held together, exchange of nutrients and gas (ex blood brain barrier)

fenestrated capillary

has pores/windows for small molecules (proteins or hormones) to move in and out of blood (ex kidney, endocrine glands)

sinusodial capillary

large pores for large molecules ot move in and out

What is the flow of blood in a capillary bed?

terminal arteriole to pre-capillary sphincter (open or closed) to capillary bed for nutrient exchange to thoroughfare channel to post capillary venule

What makes veins different from arteries?

carry deoxygenated blood, have very low pressure (no pulse), have valves, and have a larger lumen and smaller tunica media

What is the skeletal muscular pump?

skeletal muscle in the limb contracts, putting pressure on the veins. valves ensure the blood flows in only one direction up to the heart