CH. 22 Heart

Question 1

What are the two basic types of blood vessels and in which direction do they transport blood?

Answer 1

Arteries - transport blood away from the heart; carry blood high in oxygen

Veins - transport blood back to the heart; carry blood low in oxygen

Question 2

What are the related characteristics and functions of the heart?

Answer 2

1. Heart’s anatomy ensures the unidirectional flow of blood through it and backflow is prevented by valves
2. acts like two side by side pumps that work ath the same rate and pump the same volume of blood; one directs blood to the lungs for respiratory gas exchange, whereas the other directs blood to body tissues for nutrient and respiratory gas delivery
3. heart develops blood pressure through alternate cycles of heart wall contraction and relaxation

Question 3

What are the two circulations of the cardiovascular system?

Answer 3

1. Pulmonary circulation: conveys deoxygenated
   blood from the right side of the heart through blood vessels to the lungs for the pickup of oxygen and the release of carbon dioxide,
   and then back through blood vessels to the left side of the heart.
2. Systemic circulation: moves oxygenated blood
   from the left side of the heart through blood vessels to the systemic cells such as those of the liver, skin, muscle, and brain. Nutrients, respiratory
   gases, and wastes are exchanged with these systemic cells before blood
   is returned to the right side of the heart

Question 4

Describe the position of the heart.

Answer 4

• the heart is located left of the body midline posterior to the sternum in the mediastinum
• slightly rotated such that its right border is located more anteriorly

Question 5

Describe the differences between the base and the apex of the heart.

Answer 5

Base: posterosurface of the heart that is formed primarily by the left atrium; pulmonary veins that enter the left atrium border this base

Apex: inferior, conical end; projects slightly anteroinferiorly toward the left side of the body

Question 6

Describe the function and characteristics of the pericardium.

Answer 6

a fibrous sac and serous lining of which the heart is contained; restricts the heart’s movements so that it doesnt bouce and move about in the thoracic cavity, and prevents the heart from overfilling with blood

composed of two parts:

1. fibrous pericardium: outer portion that consists of a tough, dense connective tissue layer
2. serous pericardium: inner portion is a thin, double layered serous membrane
   - can be subdivided into two 2 layers: 1) parietal layer and 2) visceral layer

Question 7

Describe the 3 distinctive layers of the heart wall.

Answer 7

epicardium: outermost heart layer and is composed of a serous membrane and areolar CT
myocardium: the middle layer of the heart wall and is composed of cardiac muscle tissue; contraction of cardiac muscle composing the myocardium generates the force necessary to pump blood
endocardium: covers the internal surface of the heart chambers and external surfaces of the heart valves; composed of simple squamous ET and and underlying layer of areolar CT

Question 8

What are the four hollow chambers that the external heart is composed of?

Answer 8

The left and right atria and the larger left and right inferior chambers known as the ventricles

Question 9

How do the valves function to create the “lubb dupp” sound of a beating heart?

Answer 9

when the flaps of the atrioventricular valves close, they produce the first “lubb” sound

when the semilunar valves close, the “dupp” sound is produced

Question 10

What are the functions of the fibrous skeleton of the heart?

Answer 10

1) provides structural support at the boundary between the atria and the ventricles
2) forms supportive fibrous rings to anchor the heart valves
3) provides a rigid framework for the attachment of cardiac muscle tissue
4) acts an an electrical insulator because it does not conduct action potentials and thus prevents the ventricles from contracting at the same time as the atria

Question 11

What are the 3 major vessels that empty into the right atrium?

Answer 11

1) superior vena cava: drains blood from the head, neck, upper limbsm and superior regions of the trunk
2) inferior vena cava: drains blood from the lower limbs and trunk
3) coronary sinus: drains blood from the heart wall

Question 12

What thin wall separates the right and left atria?

Answer 12

the interatrial septum

Question 13

What occurs after gas exchange occurs in the lungs?

Answer 13

oxygenated blood travels through the pulmonary veins to the left atrium

Question 14

What supplies the heart wall?

Answer 14

the left and right coronary arteries travel within the coronary sulcus of the heart to supply the heart wall

Question 15

Where do the cardiac veins all drain into?

Answer 15

they all drain into the coronary sinus, a large vein that lies in the posterior aspect of the coronary sulcus; the coronary sinus drains directly into the right atrium of the heart

Question 16

What makes the precise coordinated contractions of the heart chambers possible?

Answer 16

contractions are made possible by the properties of cardiac muscle tissue and by specialized cells in the heart, known collectively as its conducting system

Question 17

How do cardiac and skeletal muscle tissue differ?

Answer 17

■ The sarcoplasmic reticulum in cardiac muscle is less extensive
and not as organized as in skeletal muscle.
■ Cardiac muscle has no terminal cisternae, whereas skeletal
muscle does.
■ Cardiac muscle lacks the extensive association of sarcoplasmic
reticulum and transverse tubules (T-tubules) present in skeletal
muscle.
■ In cardiac muscle, T-tubules overlie Z discs instead of the
junctions of A bands and I bands as seen in skeletal muscle.
■ The T-tubules in cardiac muscle have a less extensive distribution and a reduced association with SER compared to those in skeletal muscle, allowing for both the delayed onset and prolonged contraction of cardiac muscle tissue.

Question 18

What attributes to cardiac muscle’s ability to contact muscle impulses that are distributed immediately and simultaneously throughout all cells of first the atria and then the ventricles?

Answer 18

Neighboring cardiac muscle cells in the walls of heart chambers have formed specialized cell-cell contacts called intercalated discs which electrically and mechanically link the cells together and permit the immediate passage of muscle impulses

Question 20

What specialized cardiac muslce cell initiates the heartbeat?

Answer 20

cells of the sinoatrial node, which are located in the posterior wall of the right atrium act as the pacemaker, the rhythmic center that establishes the pace for cardiac activity

Question 21

Describe the events in a normal cardiac cycle,

Answer 21

1. atrial contraction and ventricular filling: brief contraction of atrial myocardium initiated by SA node; contraction of atria finishes filling the ventricles through the open AV valves while the ventricles are in diastole
2. isovolumetric contraction: AV valves are forced closed and semilunar valves remain closed; atria remain in diastole
3. ventricular ejection: pressure on blood in the ventricles forces the semilunar valves to open, and blood is ejected into the arterial trunks. the atria remain in diastole, and the AV valves remain closed
4. isovolumetric relaxation: semilunar valves close to prevent blood backflow into the ventricles; AV valves remain closed and the atria remain in diastole
5. atrial relaxation and ventricular filling: atria remain in diastole and the AV valves open, and passive filling of the ventricle from the atria begins; semilunar valves remain closed

Question 22

Provide a summary of blood flow.

Answer 22

■ Blood flows from high pressure to low pressure.
■ Heart valves keep blood flowing in one direction.
■ Blood flows from veins into the atria under low pressure.
■ About 70% of the ventricular filling occurs passively when
both chambers are relaxed, atrial pressure is greater than the
ventricular pressure, and the AV valves are open. Atrial systole
fills the final 30% of the ventricles.
■ Ventricular contraction (systole) increases pressure on the blood
within the ventricles. This pressure continues to increase, first
closing the AV valves, then forcing the semilunar valves open
to eject blood into the great arteries.