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The Structure and Function of the Heart and Blood Vessels

The Structure and Function of the Heart and Blood Vessels

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Page 1: The Structure and Function of the Heart and Blood Vessels

The Structure and Function of the Heart and Blood Vessels

Page 2: The Structure and Function of the Heart and Blood Vessels

Blood Vessels

• Arteries: thick-walled blood vessels that ALWAYS carry blood AWAY from the heart.

• Veins: thin-walled blood vessels that ALWAYS carry blood TOWARD the heart.

Arteries Arterioles Capillaries Venules Veins

Page 3: The Structure and Function of the Heart and Blood Vessels

Blood Vessels

Page 4: The Structure and Function of the Heart and Blood Vessels

Arterial System

• Transports blood under pressure.• Blood moves in a pulse-like wave.• Contraction & relaxation of arterioles is

the major determinant of the overall blood pressure.

Page 5: The Structure and Function of the Heart and Blood Vessels

Capillaries

• Narrowest of all blood vessels.• RBCs travel in single file.• Branching of the capillaries increases the

surface area available for diffusion.• Connects the arterial & venous systems.

Page 6: The Structure and Function of the Heart and Blood Vessels

Venous System

• Thinner walls, larger diameters & less muscle than arteries.

• Contains 70% of total blood volume.• Most veins work against gravity.

• Valves allow one-way flow.• Contraction of skeletal muscles pushes blood

toward heart.

Page 7: The Structure and Function of the Heart and Blood Vessels

Blood Vessels

Page 8: The Structure and Function of the Heart and Blood Vessels

The Heart

• Size of fist.• Hardest-working muscle.• Contains four chambers:

• Left & right atria (receiving chambers).• Left & right ventricles (delivery chambers).

• Septum separates left & right sides.

Page 9: The Structure and Function of the Heart and Blood Vessels

The Heart

• Protected by the ribcage, sternum & spine.

Page 10: The Structure and Function of the Heart and Blood Vessels

Pathways of Blood

• Pulmonary Circuit• Right side of heart.• Low-pressure system.

• Systemic Circuit• Left side of heart.• High-pressure system.

Page 11: The Structure and Function of the Heart and Blood Vessels

Pulmonary Circuit

• Right atrium receives oxygen-poor blood from:• Superior vena cava.• Inferior vena cava.

• Blood flows through the tricuspid valve or the right atrioventricular (AV) valve to the right ventricle.

Page 12: The Structure and Function of the Heart and Blood Vessels

Pulmonary Circuit

• Blood flows through the pulmonary semi-lunar valve & enters the pulmonary trunk, which divides into the left & right pulmonary arteries.• Divides into capillaries where external gas exchange occurs.

• Oxygenated blood enters the left & right pulmonary veins, returning blood to the left atrium.

Page 13: The Structure and Function of the Heart and Blood Vessels

Systemic Circuit

• Blood flows through the left AV-valve or bicuspid (mitral) valve to the left ventricle.• Left ventricular walls are two times thicker than in

the right ventricle.• Blood travels through the aortic

semi-lunar valve to the aorta.

Page 14: The Structure and Function of the Heart and Blood Vessels

Systemic Circuit

• Aorta branches into smaller systemic arteries, which branch into arterioles & then capillaries.• Internal gas exchange occurs.

• Capillaries rejoin as venules & then veins.• Deoxygenated blood returns to the right

atrium via the superior & inferior vena cava.

Page 15: The Structure and Function of the Heart and Blood Vessels

Systemic Circuit

Page 16: The Structure and Function of the Heart and Blood Vessels

Coronary Circulation

• Delivers oxygenated blood to the heart muscle.• Consists of the left & right coronary artery.

Page 17: The Structure and Function of the Heart and Blood Vessels

Cardiac Contractions

• Sinoatrial (SA) node or pacemaker in the right atrium maintains the heart’s intrinsic pumping rhythm.• Nerves influence the rate & strength of the heart’s

contractions.• This signal travels to the atrioventricular (AV) node,

where it is delayed for 0.1 seconds .• It travels to the ventricles via Purkinje fibers & Bundle

of His.• The delay at the AV node causes the atria to contract

simultaneously before the ventricles.

Page 18: The Structure and Function of the Heart and Blood Vessels

Cardiac Contractions

Page 19: The Structure and Function of the Heart and Blood Vessels

The Heart Cycle

• The cardiac cycle is a continuous cycle of relaxation & contraction.• Diastole

• Heart relaxation

• Systole• Heart contraction.

Page 20: The Structure and Function of the Heart and Blood Vessels

Diastole (80 mm Hg)

• Blood enters all four chambers.• Pulmonary veins left atrium.• Inferior & superior vena cava right

atrium.• Left & right AV valves are open.• Pulmonary & aortic semi-lunar valves are

closed.

Page 21: The Structure and Function of the Heart and Blood Vessels

Systole (120 mm Hg)

• Aria contract to further fill the ventricles.• Tricuspid & bicuspid valves forced closed

due to an increase in ventricular pressure.• Ventricles contract to force blood from the

heart.• Pulmonary & aortic semi-lunar valves are

open.

Page 22: The Structure and Function of the Heart and Blood Vessels

Diastole & Systole

Page 23: The Structure and Function of the Heart and Blood Vessels

Blood Pressure

• Pressure exerted on the arterial walls.• The elastic property of vessels allows

for continuous blood flow throughout the circulatory system.

• The difference between your systolic pressure & your diastolic pressure is called your pulse pressure.

Page 24: The Structure and Function of the Heart and Blood Vessels

Blood Pressure

• Highest in the aorta.• Blood pressure & velocity both decline as

blood enters the arterioles.• The drop in pressure results from the

resistance (friction) to blood flow.• Low blood pressure reduces your capacity to

transport blood.• High blood pressure weakens & ruptures

arterial walls.

Page 25: The Structure and Function of the Heart and Blood Vessels

Blood Pressure

Page 26: The Structure and Function of the Heart and Blood Vessels

Heart Valves & Heart Sounds

• “Lub”: Tricuspid & bicuspid valves close (beginning of systole).

• “Dub”: Pulmonary and aortic semi-lunar valves close (end of systole).

Page 27: The Structure and Function of the Heart and Blood Vessels

Heart Valves & Heart Sounds