CHAPTER 1 : TRANSPORT

1.2 The Concept of Circulatory System

LEARNING OUTCOME

•Describe the structure of human blood vessels

STRUCTURE OF HUMAN BLOOD VESSELS

• Tubes that transport blood from one part to another in the human body

3 types of human blood vessels

•Transport blood away from the

heart

•Connect arterioles to

venules

• Transport blood to the heart.

ARTERIES• Carry blood away from the

heart• Branch into smaller vessels

arterioles capillaries• To transport blood quickly &

at high pressure to the tissues.

• Arteries walls consist of epithelial tissue, smooth muscle & connective tissue

• The muscle tissue enables the artery to constrict & dilate.

CAPILLARIES• The sites for the exchange

of nutrients, respiratory gases & waste products.

• Thin-walled blood vessels which allow rapid gaseous exchange to occur, only one-cell thick.

• Capillaries venules veins

VEINS• Transport blood back to

the heart• Consist of epithelial

tissue surrounded by smooth muscle (thinner than arteries) & connective tissue

• Blood flows under low pressure

• Have large lumens & valves that maintain the one-way flow of blood

Differences between arteries, capillaries & veins

Arteries Capillaries Veins

Transport blood away from the heart

Connect arterioles to venules

Transport blood to the heart

Transport oxygenated blood

(except the pulmonary artery)

Act as the sites for exchange of

substances with the cells

Transport deoxygenated blood

(except the pulmonary vein)

Thick muscular wall Thinnest wall, one cell in thickness

Thinner wall

No valves except semi-lunar valves at the base of the aorta & pulmonary artery

No valves Valves present to prevent back flow of

blood

Blood flows in pulse under high pressure

No pulses; pressure lower than arteries

but higher than veins

No pulses; blood flows under lower

pressure than arteries