The Circulatory SystemWednesday, February 3rd, 2009

The Blood Vessels

TODAY’ S TARGETS:

Identify the functions of the circulatory system

C5b: Structure of types of vessels

C5c: Distinguish between the pulmonary and systemic circuits

C5a: Identify the functions of several vessels

Think About It

• What are the functions of the circulatory system?

Functions of the Circulatory System

• Primary function is to transport necessary materials to all the cells of an animal’s body, and to transport waste products away from the cells where they can be released into the environment

• What necessary materials?• What waste products?

Think About It

• What are the types of vessels in the human body?

• What is their function?

Characteristics of Blood Vessels

• The part of the circulatory system that transports blood throughout body

• 3 layers:– External layer of connective tissue– Middle layer of smooth muscle &

elastic tissue– Inner layer of endothelium

ArteriesArteries carry blood AWAY from the heart

have THICK walls composed of elastic and muscular fibers Why?

Aneurysms

Aortic aneurysm

ArteriolesArteries branch into arterioles

small branches of arteries about 0.2 mm in diameter or smaller arterioles can dilate or constrict to control blood distribution to tissues

Arterial Structure

Veins and VenulesTake blood from the capillaries TO the heartVenules drain blood from capillaries and then join to form a vein Vein walls are thinner than arterial walls, have

less elastic & smooth muscle, less rigid

veinartery

VeinsVeins have valves Why?Valves allow blood to flow only toward the heart when they are open and prevent the

backward flow of blood when they are closed

Prosthetic Valve under researchhttp://gtresearchnews.gatech.edu/newsrelease/vein-valve.htm

Think About It• Predict how blood returns to the heart through

veins (works against gravity & low blood pressure)

14

Varicose Veins

Quiz yourself on Venous return

• http://www.phschool.com/science/biology_place/biocoach/cardio2/venousreturn.html

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CapillariesSmallest and narrowest vessels in the body Gas and nutrients/wastes exchange across

capillary walls (O2, CO2, glucose, etc.)Only single-celled layer of endothelium Why?Sphincter muscles encircle the entrance to each

capillary

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Diameter of capillaries only one cell thick Why?

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Some numbers…

Average human body has ~5-6 L of blood (7-8% of body’s weight)

At any one time the veins contain about 75% of the body's blood; about 20% is in the arteries; only about 5% is in the capillaries.

You have close to 100,000 km of blood vessels! Largest vessel in human aorta (diameter of garden hose)Capillaries very small about 10 together = 1 human hair

Pulmonary Circuit Path of blood from heart lungs heart Deoxygenated blood from all tissues RIGHT ATRIUM (heart)

pumped to the right ventricle sent to pulmonary trunk, which divides into PULMONARY ARTERIES, which divide up into the arterioles of the lungs.

Pulmonary Circuit These arterioles take blood to the pulmonary capillaries, where CO2 is

released in exchange for O2 . The oxygenated blood then enters pulmonary venules, then the

PULMONARY VEINS, and finally back to the LEFT ATRIUM (heart).

Systemic Circuit

Includes all blood vessels except those in the pulmonary circuit.

It takes oxygenated blood from

the LEFT VENTRICLE of the heart, through the tissues & organs of the body, and brings deoxygenated blood back to the RIGHT ATRIUM of the heart.

• The mammalian cardiovascular system

Pulmonary vein

Right atrium

Right ventricle

Posteriorvena cava Capillaries of

abdominal organsand hind limbs

Aorta

Left ventricle

Left atrium

Pulmonary vein

Pulmonaryartery

Capillariesof left lung

Capillaries ofhead and forelimbs

Anteriorvena cava

Pulmonaryartery

Capillariesof right lung

Aorta

Figure 42.5

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10

11

5

4

6

2

9

33

7

8

Pulmonary and Systemic Circuits

Quiz Yourself• http://www.phschool.com/science/

biology_place/biocoach/cardio2/naming.html• http://www.phschool.com/science/

biology_place/biocoach/cardio2/pumping.html

Video• http://www.youtube.com/watch?v=oHg5ZvrI4NY

C5-a:• Complete worksheet on blood vessels.C5-b: • List the 5 different vessel types.

Artery, arterioles, capillaries, venules, veins• In a chart compare the structure and function of arteries, veins,

and capillaries.

PLO Journal

Artery Vein Capillary

•Thick muscular, elastic walls•Takes blood AWAY from heart

•Thin, less rigid walls•Has valves (except veins coming from head)•Delivers blood TO heart

•Walls one-cell thick•Site of gas/nutrient exchange with tissue cells

C5-c:• Fill in the missing blanks:

Systemic Circulation:Oxygenated blood travels from the heart (left ventricle) to body cells/tissues through arteries.Deoxygenated blood travels from body cells/tissues to the heart (right atrium) through veins.Pulmonary Circulation:Oxygenated blood travels from capillaries of lung tissues to the heart (left atrium) through the pulmonary veins.Deoxygenated blood travels from the heart (right ventricle) to capillary beds in the lungs through the pulmonary arteries.

PLO Journal