Blood Vessels and Circulation

blood vessels

transport O2, nutrients, waste

closed loop system with heart

not rigid or immobile, so able to change shape based on needs

How do arteries change as they branch away from the heart and lead to capillaries?

larger to smaller

Capillaries

single cell thickness

filters and allows for quick gas and nutrient exchange

only consists of tunica intima, basement membrane, endothelium

group of capillaries = capillary bed

branching decreases BP

How to veins change as they merge towards the heart

smaller to larger

Blood Vessel Tunics (3)

tunica intima: innermost, endothelium layer lining lumen

tunica media: middle layer, circular arrangement of smooth muscle, vasoconstriction and vasodilation, thicker on arteries

tunica externa: outermost layer, areolar connective tissue, anchors vessel to other tissues

types of arteries

elastic, muscular, arterioles

venules to veins

drain capillaries and returns blood to heart

valves prevent backflow since BP is low in veins

thinner walls, larger lumen

skeletal muscle pump

deep veins pass between skeletal muscle groups

veins are squeezed during contraction

hold ~60% of blood at rest

anastomosis

connection or opening made between vessels

decreases chance of stroke (blood clot to brain)

multiple pathways of blood flow to same part of brain

Hepatic Portal System

venous network that drains GI tact and shunts blood to liver for processing and absorption of arterials

allows for digesting of nutrients from food