Blood Vessels & Circulation Chapter 13

Types of Blood Vessels Arteries Capillaries Veins Blood vessels that carry blood away from the heart Capillaries microscopic blood vessels that allow exchanges between blood and tissue Veins Blood vessels that carry blood to the heart

General Features of Blood Vessels Veins and arteries consist of three layers Tunica intima: innermost layer Tunica media: middle layer Tunica adventia: outermost layer

Arteries THREE TYPES OF ARTERIES Elastic arteries Largest in diameter Thickest walls Mostly elastic tissue Stretch when ventricles pump into them Prevents blood pressure from falling rapidly Maintains blood flow when ventricles are relaxed

Arteries Muscular arteries Medium and smaller diameter Made up of a lot of smooth muscle Control blood flow to different regions of body Vasoconstriction: Caused by contraction of smooth muscle in blood vessels Decreases blood vessel diameter and blood flow Vasodilation: Relaxation of smooth muscle in blood vessels Increases blood vessel diameter and blood flow

Arteries Small arteries Arterioles Smaller diameter Smaller walls Smallest arteries Transport blood from small arteries to capillaries

Capillaries Structure Function Single layer of simple squamous epithelium Diameter approximately the same as that of a red blood cell (7.5 micrometers) Function Receive blood from arterioles Branches out to form networks Regulated by precapillary sphincters Give up oxygen and nutrients to body tissues Take up carbon dioxide and other waste products from body tissues.

Single Erythrocyte squeezing through capillary

Capillaries Video Clip

Capillaries

Veins Venules Small Veins Medium Sized Veins Receive deoxygenated blood from capillaries Diameter a little larger than capillaries Small Veins Receive blood from venules Medium Sized Veins Collect blood from small veins and deliver it to large veins

Veins Valves Found in veins that are larger than 2 millimeters in diameter. Allow blood to flow to the heart, but not backward Composed of two cusps, or flaps Similar in function to the semi-lunar valves Valve animation

Types of Blood Vessels Video Clip

Blood Pressure Blood Pressure= measure of force blood exerts against the blood vessel walls. Systolic: Top number. Pressure in the arteries when the ventricles contract. Diastolic: Bottom number. Pressure in the arteries between beats when ventricles are resting.

Blood Pressure

Blood Pressure Blood pressure values Normal adult value is about 120 Hg systolic and 80 Hg diastolic or 120/80.