Ciencias

Circulatory System
* Heart . Muscular pumping devise
* Arteries, veins, and capillaries. Closed system of vessels.
The cardiovascular system makes its appearance early in development and reaches a functional state long before any other major organ system.

* The primitive heart begins to beat regularly early in the fourth week following fertilization.
* The vital role of thecardiovascular system in maintaining homeostasis depends on the continuous and controlled movement of blood through the thousands of miles of capillaries that permeate every tissue and reach every cell in the body. It is in the microscopic capillaries that blood performs its ultimate transport function. Nutrients and other essential materials pass from capillary blood into fluids surrounding thecells as waste products are removed.

* Blood is the transport medium.
* The heart is the organ that keeps the blood moving through the vessels.
* The heart pumps about 5 liters of blood every minute throughout life
Structure of the Heart
* Four-chambered muscular organ, shaped and sized like a man's closed fist with two-thirds of the mass to the left of midline.
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Layersof the Heart Wall
* Outer layer epicardium. Thin layer on the surface of the heart in which the coronary arteries lie.
* Middle layer myocardium. It is the heart muscle and is the thickest layer of the heart.
* Inner layer endocardium. Thin membrane that lines the interior of the heart.
* The pericardium is a thin sac the heart sits in, often filled with a small amount of fluid,which separates the heart from the other structures in the chest such as the lungs.
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Layers of the Heart Wall

Valves of the Heart
* Valves between the atria and ventricles are called atrioventricular or cuspid valves.
* Valves at the bases of the large vessels leaving the ventricles are called semilunar valves.
* Right atrioventricular valve : tricuspid
* Leftatrioventricular valve: bicuspid or mitral
* Valve between the right ventricle and pulmonary trunk : pulmonary semilunar valve.
* Valve between the left ventricle and the aorta : aortic semilunar valve.
Valves

Heartbeat
* Heart beat is a sequence of contration and relaxation of the heart chambers.
A cardiac cycle last about 8/10 of a second
* Systole : contraction phase
*Diastole: relaxation phase
Ventricles relax before the atria contracts, and ventricles contract when atria relax

* When the relaxed atria is filling with blood, the fluid pressure inside and the AV valves open.Blood flows into ventricles.
* When filled ventricle begin to contract, fluid pressure inside them ,forcing AV valves shut and semilunar valves open so blood flows out of theheart and into the aorta and pulmonary arteries. Ventricles relax and semilunar valves close.
* Half a second the atria and ventricle are in diastole; then the blood- filled atria contract, and the cycle repeats

Two Circuits of the Blood Flow
* Pulmonary Circuit : Blood picks up oxygen in the lungs.
* Blood from tissues enter the right atrium
through AV valve (tricuspid)ventricle contracts pulmonar semilunar valve main pulmonary artery, then right and left pulmonary arteries lungs (capillaries) picks up oxygen and gives up CO2 than will be exhaled freshly oxygenated blood returns through two sets of pulmonary veins left atrium
Pulmonary Circuit

Systemic Circuit
* Blood travels to andfrom tissues.
* Oxigenated blood in the pulmonary veins returns to the heart ( left atrium)…AV valve…left ventricle…semilunar valve into the aorta.
* The aorta descends into the torso,major arteries branch off it, funneling blood to organs and tissues where O2 is used and CO2 is produced

* Blood returns to the heart in veins.
* From the head,arms and chest through the superior...