11.3 Blood Vessels

Pages 487-494

Blood Vessels

• 19 000 km

Arteries

• Carry blood away from the heart3-layers:Outer connective tissue (elastic)Middle muscle layerInner epithelial layer (endothelium)

Arterioles

• Arteries branch into arterioles

Controlling blood flow

Vasodilation: Increases diameter of blood vesselIncreased blood flow to the skinCooling strategy

Controlling Blood Flow

Vasoconstriction• Nerves cause smooth muscle to contract• Narrowing of blood vessel diameter• Restricts blood flow• Response to cold

Capillaries

• No cell is farther than two cells away from a capillary.

• Blood cells move through them in single file.

Pre-capillary sphincters

• Relax and increase blood flow during exercise

Venules and veins

• Return blood to the heart• Less elasticity in the walls• Less smooth muscles in the walls• Valves keep blood flowing in the right

direction

Varicose veins

• Damaged valves in legs

Blood pressure

• Sphygmomanometer• Blood pressure cuff• Inflated until blood flow ceases then released• Systolic pressure…heart contracts 120 mmHg• Diastolic pressure…heart relaxed

80 mm Hg

Hypertension

• High blood pressureDiet, age, weight, activity level, medication are contributors to high blood pressure

Lymphatic System

• Circulatory system and immune system• Maintains blood volume• Destroys foreign invaders

Lymph

• Proteins from blood tissue fluidlymph vessels veins

Contains fluid, germs, dead or damaged cells, fat from lacteals of villi

Lymph nodes filter out germs

Spleen and tonsils

• Spleen filters lymphatic system, reservoir for RBC’s and WBC’s

• Tonsils filter germs/enlarge

thymus

• Secretes hormones that help lymphocytes, a type of leuknocyte, develop their ability to recognize and attack foreign invaders