LO 12/13/14 Flashcards
Describe the structure and position of the heart
- Triangular-shaped organ
- Fist-sized
- Hollow; 4 chambers
- Located in mediastinum
- Two thirds lies to the left of the body’s midline; one third to the right
- Apex lies on diaphragm
- Lies between the sternum and the thoracic vertebrae
- Positioning makes CPR possible
Describe the atrium/atria
- Two upper chambers
- Right and left ‘receiving’ chambers (low pressure) – blood from body returns to atriums via veins
- Smaller and thinner-walled than ventricles
Describe the ventricles
- Two lower chambers
- Right and left ‘discharging’ chambers
- Blood leaves the heart through the ventricles via arteries
Describe the myocardium
- cardiac muscle tissue that makes up wall of each heart chamber
- Atrial septum divides atria
- Ventricular septum divides ventricles
Describe the endocardium
- thin layer of very smooth tissue lining each heart chamber
- Endocarditis = inflammation of endocardium; can promote formation of blood clots
Describe the pericardium
- Covering ‘sac’
- Two-layered fibrous sac with a lubricated space between the two layers to allow them to slide against each other without friction as heart beats
- Inner layer = visceral pericardium, or epicardium. Completely covers heart
- Outer layer = parietal pericardium. Loose sac around heart
- Pericarditis = painful inflammation of pericardium
________ is the contraction of the heart, while ________ is the relaxation of the heart
- Systole
- Diastole
Provide the general direction of blood flow in the heart
Atria receive blood 🡪 atria contract 🡪
blood forced into ventricles 🡪
ventricles fill 🡪 blood forced out of heart
Direction of blood is controlled by valves
Venous blood 🡪
RA (thru sup. & inf. vena cavae) 🡪
tricuspid AV valve into RV 🡪
thru pulmonary SL valve 🡪
pulmonary artery 🡪
lungs 🡪 pulmonary veins 🡪
LA 🡪
bicuspid/mitral AV valve 🡪
LV 🡪
aortic SL valve 🡪
aorta 🡪
arterial blood distributed throughout body
What are 4 valves in the heart that prevent the back flow of blood?
- 2 atrioventricular valves (AV valves)
- 2 semilunar valves (SL valves)
Describe the atrioventricular valves (AV valves)
- Separate atria from ventricles
- Tricuspid valve: on right side of heart
- Bicuspid or mitral valve: on left side of heart
- Chordae tendinae attach AV valves to wall of heart
Describe the semilunar valves (SL valves)
- Pulmonary SL valve - Between right ventricle and pulmonary artery
- Aortic SL valve - Between left ventricle and aorta
Describe the lub dup sounds in each heartbeat cycle
- First (lub) sound (longest): caused by the vibration & sudden closure of AV valves during contraction of the ventricles
- Second (dup) sound: caused by the closure of the semilunar valves during relaxation of the ventricles
How does the heart act as 2 different pumps?
- RA and RV perform different functions from the LA and LV
- With each heart beat, the LA and RA contract simultaneously to fill the LV and RV with blood = atrial systole
- Next, the LV and RV contract simultaneously = ventricular systole
Describe coronary circulation (blood supply to the heart)
- Constantly working cardiac muscle (myocardium) needs a constant supply of oxygen and nutrient rich blood
- The blood that supplies oxygen and nutrients to the myocardium, flows through the right and left coronary arteries (very first branches of the aorta)
- Blockage of blood flow through the coronary arteries is called myocardial infarction (MI), or heart attack
Describe angina pectoris
Chest pain caused by inadequate oxygen to the heart
Describe coronary bypass surgery
Veins from other parts of the body are used to bypass blockages in coronary arteries
Describe the cardiac cycle
- Heartbeat is regular and rhythmic—each complete beat is called a cardiac cycle
- Each cycle (beat) is approx. 0.8 sec long
- Average = 72 beats/minute, normal 60-100 bpm
- Each cycle is subdivided into systole (contraction phase/lub) and diastole (relaxation phase/dup)
The _________ is the amount of blood that one ventricle ejects with each beat
Stroke volume
The _________ is the amount of blood that one ventricle ejects each minute (ave = 5L at rest)
Cardiac output
What 5 specialized structures embedded in the wall of the heart help generate strong impulses and conduct them to the various regions of the heart wall?
- Intercalated disks
- Sinoatrial node (SA node)
- Atrioventricular node (AV node)
- AV bundle (bundle of His)
- Purkinje fibres
Describe Intercalated disks
Special electrical ‘connections’ between cardiac muscle fibers allowing cardiac muscle to contract as a whole, at about the same time
Describe the Sinoatrial (SA) node
- the pacemaker – where impulse starts
- located in the wall of the RA near the opening of the superior vena cava
Describe the AV (atrioventricular) node
located in the RA along the lower part of the interatrial septum
Describe the AV bundle (bundle of His)
located in the septum of the ventricle