BIO 12 UNIT 4: Study Notes

BLOOD VESSELS

1. ARTERIES: Thick walls, inside layer (endothelium), move blood away from heart and towards arterioles (O2ated) 

1. Inner Layer: Epithelial cells
2. Middle Layer: Elastic tissue and smooth muscle
3. Outer Layer: Fibrous connective tissue **Walls help with function to expand after heartbeat/maintain blood pressure**
2. ARTERIOLES: Smaller arteries, middle layer=smooth muscle, fibers of muscle contract and relax relating to blood pressure, transports O2ated blood towards capillaries (away from heart)
3. CAPILLARIES: Narrow, one-cell thick, endothelium walls, form capillary beds, regulates blood flow from the arterioles to the venules (bridge), gas exchange/nutrient exchange site--> O2 and other nutrients leaves thin capillary walls and joins tissue fluid, wastes diffuse into capillary                                     
4. VENULES: Small veins that drain capillary bed and join to form a vein, moves blood towards heart (deO2ated towards veins)   
5. VEINS: Has valves, brings deO2ated blood from capillary (venules) to the heart, valves allow for blood to flow in the right direction in the heart and prevent backflow, blood reservoirs (contain much of blood volume)