Chapter 20 - The Heart

Question 1

Heart Overview

Answer 1

• Double pump
  
  • Systemic and pulmonary circuits
  • Pumps 8,000 liters of blood
• Beats 100,000 times a day
  
  • contracts in series: atria, then ventricles
  • autorhythmicity (neural or hormonal stimulation)

Question 2

Heart Position, Size, and Shape

Answer 2

• located in mediastinum
• size of a fist
• base is superior
• apex points inferiorly, to the left

Question 3

Pulmonary Circuit

Answer 3

• blow flows from right heart to lungs

- gas exchange in lungs (oxygen loaded into blood)

Question 4

Systemic Circuit

Answer 4

• blood flows from left heart to all body organs

- gas exchange in organs (oxygen unloaded from blood)

Question 5

Pericardium

Answer 5

• double-walled
  
  • pericardial sac (parietal) - fibrous, serous layers
  • epicardium (visceral)
  • pericadial cavity - space between walls

Question 6

The Heart Wall

Answer 6

• three-layer wall
  
  • epicardium - serous membrane
  • myocardium - cardiac muscle, vortex pattern
  • endocardium - lines chambers, simple squamous epithelium

Question 7

Left and Right Atria

Answer 7

• thin-walled, superior
• separated by interatrial septum
• receiving chambers
• auricles - ear-like extensions
• pectinate muscles - internal ridges

Question 8

Left and Right Ventricles

Answer 8

• thick-walled, inferior
• separated by interventricular septum
  
  • anterior, posterior interventricular sulci overlay it
• pumping chambers
• trabeculae carnae - internal ridges

Question 9

Heart Valves

Answer 9

• atrioventricular (AV) valves close when ventricles contract
  
  • right AV (tricuspid) valve
  • left AV valve or mitral valve
  • tendineae chordae tether valves to papillary muscles
• semilunar valves close when ventricles relax
  
  • pulmonary valve - at exit of right ventricle
  • aortic valve - at exit of left ventricle

Question 10

Coronary Circulation

Answer 10

arterial supply to cardiac muscle

Question 11

Myocardial Infarction

Answer 11

• death of heart tissue
• “heart attack”
• caused by blockage

Question 12

Left Coronary Artery

Answer 12

• anterior interventricular branch
• circumflex branch
  
  • left marginal branch

Question 13

Right Coronary Artery

Answer 13

• right marginal branch

- posterior interventricular branch

Question 14

Venous Drainage of Cardiac Muscle

Answer 14

• most blood is returned to right atria through the coronary sinus, which received blood from:
  
  • great cardiac vein
  • posterior interventricular (middle cardiac) vein
  • left marginal vein

Question 15

Conduction System

Answer 15

• cardiac muscle contracts on its own by “pacemaker cells” in sinoatrial node in right atrium
• specialized cardiac cells initiate and distribute the stimulus or electrical impulses
  
  • “conduction sys.” or “nodal sys.”
• actual contraction lags behind the impulse (action potential)
• SA node, AV (atrioventricular) node, and conduction cells

Question 16

___________ nervous system modulates heart’s intrinsic activity.

Answer 16

autonomic

Question 17

_____________ __________ stimulates heart with cardiac nerves from cervical ganglia.

Answer 17

sympathetic division

• innervation of myocardium
• stimulation increases force of contraction

Question 18

_________________ __________ slows the heart with activity of the vagus nerve.

Answer 18

parasympathetic division

• right vagus nerve innervates mainly SA node
• left vagus nerve innervates mainly AV node

Question 19

Heart Changes at Birth

Answer 19

• in fetal heart, foramen ovale and ductus arteriosis cause most blood to bypass pulmonary circuit
• when lungs inflate at birth, their resistance to blood flow decreases
  
  • flap seals foramen ovale (eventually fossa ovalis)
• serveral hours after birth, ductus arteriosis closes
  
  • eventual remnant is ligmentum arteriorsum

Question 20

The Aging Heart

Answer 20

• arteries stiffen with age
  
  • heart works harder to overcome resistance
  • thicken muscles can shrink chamber volume/cardiac output
• valves become more fibrous and likely to prolapse
• loss of cells from intrinsic conduction system can lead to irregular rhythms
• loss of myocytes can weaken contractions

Question 21

Heart Diseases

Answer 21

• leading cause of death in US
• coronary atherosclerosis (common form)
  
  • can lead to myocardial infarction
• categories of heart disease:
  
  • congenital defects in anatomy
  • myocardial hypertrophy or degeneration
  • inflammation of pericardium or heart wall
  • valvular defects
  • cardiac tumors