admin
Admin
عدد المساهمات : 9483
تاريخ التسجيل : 06/08/2009
 | موضوع: heart physiology  السبت نوفمبر 06, 2010 4:46 am | |
| The human heart
compact – size of your fist!
hardest working muscle in your body - constantly pumping, day after day!
70 times per minute, OR approximately 90,000 times per day!
each beat must be able to pump fluid through ~160,000 km of vessels!
must maintain a steady flow, but be able to adjust quickly – and without conscious controls – to demands for an increase or decrease in the pressure of fluid within the system!
pumps in 2 directions at once without mixing the fluid travelling in the 2 directions!
Heart Anatomy
The heart is composed of 4 chambers
Right & Left Atrium: receives blood from veins
Atria: thin walls and do not generate much force – only have to push blood to adjacent ventricles
Right & Left Ventricle: delivers blood into arteries
Ventricles: thicker, muscular walls - push blood out through blood vessels and capillary beds in the pulmonary/ systemic circulatory systems
Left ventricle has the thickest walls, since it must force blood the greatest distance
The heart contains 4 valves that prevent backflow of blood.
2 AtrioVentricular valves (AV valves)
Tricuspid valve (b/w right atrium and ventricle)
Bicuspid (or Mitral) valve (b/w left atrium and ventricle)
2 Semi-Lunar valves
Aortic valve (b/w left ventricle and aorta)
Pulmonary valve (b/w right ventricle and pulmonary artery)
Heart Sounds
The “lub-dub” sound* of you hear through a stethoscope is caused by the closing of these valves!!
“Lub” - softer: AV valve closing
“Dub” – louder: Semi-Lunar valves closing
Blood flow through the heart
Recall: Blood enters heart through atria leaves the heart through ventricles
“Double pump” - forces blood through the cardiac cycle
Blood returns to body collected in superior vena cava, then flows into right atrium atria contract and right atrium pumps blood into right ventricle ventricles contract, right ventricle pumps blood from heart out to lungs through pulmonary artery oxygenated blood returns to heart (pulmonary vein)- which enter left atrium atria contract again left atrium pumps blood into left ventricle ventricles contract, left ventricle pumps blood out through aorta to systemic circulatory system.
Note: The atria contract at the same time, and the ventricles contract at the same time. Thus, only 2 contractions are required to force blood through all 4 chambers.
Heart Rate (HR)
average heart rate for
adult men is 70 bpm (beats per minute)
women is 75 bpm
Children and smaller people usually have a higher average
to download the lecture completely press on this link............................
dr khaled abulfadle
 | |
|
