Nakamura Human Anatomy Ch 19

Question 1

Heartbeat

Answer 1

•70–80 beats/minute at rest
•Systole: contraction
•Diastole: expansion
•Systole and diastole also refer to:
     –Stage of heartbeat when ventricles contract and expand

Question 2

Structure of heart wall

Answer 2

Walls differ in thickness
     –Atria: thin walls
     –Ventricles: thick walls
•Left ventricle
     -three times thicker than right
     –Exerts more pumping force
     –Flattens right ventricle into a crescent shape

Question 3

Valve structure

Answer 3

Each valve composed of endocardium with connective tissue core
•Atrioventricular (AV) valves: between atria and ventricles
•Aortic and pulmonary valves: at junction of ventricles and great arteries

Question 4

The heart

Answer 4

A muscular double pump
–Pulmonary circuit: takes blood to and from the lungs
–Systemic circuit: vessels transport blood to and from body tissues
-4 chambers
•l/R Atria: receive blood from the pulmonary and systemic circuits
•L/R Ventricles: the pumping chambers of the heart

Question 5

Heart sounds

Answer 5

Lub-dup” : sound of valves closing
•First sound “lub”: the AV valves closing
•Second sound “dup”: the semilunar valves closing
-Each valve sound is best heard near a different heart corner
–Pulmonary valve: superior left corner (2nd intercostal space)
–Aortic valve: superior right corner (2nd intercostal space)
–Mitral (bicuspid) valve: at the apex (5th intercostal space)
–Tricuspid valve: inferior right corner (5th intercostal space)

Question 6

Fibrous skeleton

Answer 6

•Surrounds all four valves
–Composed of dense connective tissue
•Functions
–Anchors valve cusps
–Prevents overdilation of valve openings

Question 7

Conducting system

Answer 7

-Cardiac muscle tissue has intrinsic ability to:
–Generate and conduct impulses
–Signal these cells to contract rhythmically
•Conducting system
–A series of specialized cardiac muscle cells
–Sinoatrial (SA) node sets the inherent rate of contraction

Question 8

Innervation

Answer 8

-Heart rate is altered by external controls
•Nerves to the heart include:
–Visceral sensory fibers
–Parasympathetic branches of the vagus nerve
–Sympathetic fibers: from cervical and upper thoracic chain ganglia

Question 9

Blood supply to the heart

Answer 9

Functional blood supply from Coronary arteries
•Arise from the aorta
–Located in the coronary sulcus
–Main branches are Left and right coronary arteries
Brain can only last 20 mins without oxygen

Question 10

Conducting system steps

Answer 10

1. Sinoatrial node (pacemaker) (main electricity from here)
2. Atrioventricular node
3. Atrioventricular bundle
4. Bundle branches
5. Purkinje fibers

Question 11

Function of atrioventricular valve (open)

Answer 11

1. Blood returning to the heart fills atria, putting pressure against atrioventricular valves forcing them open
2. As ventricles fill, atrioventricular valve flaps hang limply into ventricles
3. Atria contract, forcing additional blood into ventricles

Question 12

Function of the atrioventricular valves closed

Answer 12

1. Ventricles contract, forcing blood against atrioventricular valve cusps
2. Atrioventricular valves close
3. Papillary muscles contract and chordae tendineae tighten, preventing valve flaps from everting into atria

Question 13

Function of the semilunar valves (open)

Answer 13

As ventricles contract and interventricular pressure rises, blood is pushed against semilunar valves, forcing them open

Question 14

Function of semilunar valves (closed)

Answer 14

As ventricles relax and interventricular pressure falls, blood flows back from the arteries, filling the cusps of semilunar valves and forcing them to close