Chapter 20 - The Heart Flashcards
Heart Overview
- 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)
Heart Position, Size, and Shape
- located in mediastinum
- size of a fist
- base is superior
- apex points inferiorly, to the left
Pulmonary Circuit
- blow flows from right heart to lungs
- gas exchange in lungs (oxygen loaded into blood)
Systemic Circuit
- blood flows from left heart to all body organs
- gas exchange in organs (oxygen unloaded from blood)
Pericardium
- double-walled
- pericardial sac (parietal) - fibrous, serous layers
- epicardium (visceral)
- pericadial cavity - space between walls
The Heart Wall
- three-layer wall
- epicardium - serous membrane
- myocardium - cardiac muscle, vortex pattern
- endocardium - lines chambers, simple squamous epithelium
Left and Right Atria
- thin-walled, superior
- separated by interatrial septum
- receiving chambers
- auricles - ear-like extensions
- pectinate muscles - internal ridges
Left and Right Ventricles
- thick-walled, inferior
- separated by interventricular septum
- anterior, posterior interventricular sulci overlay it
- pumping chambers
- trabeculae carnae - internal ridges
Heart Valves
- 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
Coronary Circulation
arterial supply to cardiac muscle
Myocardial Infarction
- death of heart tissue
- “heart attack”
- caused by blockage
Left Coronary Artery
- anterior interventricular branch
- circumflex branch
- left marginal branch
Right Coronary Artery
- right marginal branch
- posterior interventricular branch
Venous Drainage of Cardiac Muscle
- 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
Conduction System
- 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
___________ nervous system modulates heart’s intrinsic activity.
autonomic
_____________ __________ stimulates heart with cardiac nerves from cervical ganglia.
sympathetic division
- innervation of myocardium
- stimulation increases force of contraction
_________________ __________ slows the heart with activity of the vagus nerve.
parasympathetic division
- right vagus nerve innervates mainly SA node
- left vagus nerve innervates mainly AV node
Heart Changes at Birth
- 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
The Aging Heart
- 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
Heart Diseases
- 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
