Chapter 16 Cardiovascular System- Vessels

Types of Vessels

• There are 5 types of blood vessels.

• Arteries - take blood away from heart-aorta and pulmonary trunk

• arterioles - medium sized

• capillaries - microscopic vessels in tissues

Types of Vessels

• venules - small veins

• veins - take blood back to heart

• arteries --> arterioles --> capillaries --> venules --> veins

Blood Reservoirs

• Because veins carry so much blood, certain veins function as blood reservoirs, or holders of blood.

• The main areas are veins of the abdominal organs.

• This blood can be diverted quickly to other parts of the body when needed such as skeletal muscles.

Arteries and Arterioles

• Lumen -hollow space thru which blood flows

• Inner layer of endothelium- simple squamous

• Middle layer of smooth muscle and elastic tissue

• Outer layer of elastic and collagen fibers

Nervous System Control

• Vasoconstriction - sympathetic nervous stimulation causes contraction of muscle and decrease in diameter of lumen

• Vasodilation - decrease in stimulation of SNS causes relaxation of muscle and increase in diameter of lumen

Veins and Venules

• Veins return blood from the body to the heart-deoxygenated blood

• Middle and inner layers thinner than arteries

• contain valves which prevent backflow of blood– varicose veins caused by repeated pressure

from backflow which pushes vein walls out

Venous Return• Due to pressure

from– heart contractions– skeletal muscle

pump

– respiratory pump

• diaphragm moves down and decrease thoracic pressure and increasing abdominal pressure

Capillaries connect arteries and veins. This is where oxygen is exchanged with the body.

Capillaries

• Microscopic with blood flow when tissue active

• movement of substances into and out of tissue cells

Capillary exchange• Simple Diffusion

Bulk Flow

• bulk flow - passive process of movement of large numbers of particles in same direction

Bulk Flow

– filtration - water and solutes flow from capillary into interstitial fluid

– reabsorption - water and solutes flow from interstitial fluid back into capillary

– autoregulation - tissue control of flow by vasodilation and vasoconstriction

Blood Pressure

• Pressure exerted on walls of vessels

• vascular resistance is opposition to blood flow and affects BP

– size of blood vessel lumen (inner space)

– blood viscosity (thickness)

– total blood vessel length

• regulation

– cardiovascular center

– hormonal

• Systolic – pressure when heart contracts

• Diastolic – pressure when heart relaxes

• Sphygmomanometer – blood pressure cuff

• Which number should be higher? Why?

Systemic

• Systemic circulation- includes the aorta that carries oxygenated blood from the left ventricle to the body and the veins and venules that carry deoxygenated blood back to the right atrium

Pulmonary

• Pulmonary circulation- the flow of deoxygenated blood from the right ventricle to air sacs in the lungs and the return of oxygenated blood to the left atrium

Vocabulary

• Artery• Arteriole• Capillary• Capillary exchange

• Venule• Vein• Blood pressure• Systemic circulation• Pulmonary circulation