THE SYSTEMIC AND PULMONARY CIRCULATIONS in Visual Studio .NET

Draw Code 128A in Visual Studio .NET THE SYSTEMIC AND PULMONARY CIRCULATIONS

For ease of study, the major vessels and heart chambers are often grouped together into two connected circulations The pulmonary or right-heart circulation involves the circulation of blood to, through, and from the lungs The systemic (sis-TEM-ik) or left-heart circulation, in contrast, represents the circulation of blood to, through, and from the tissues of all the major body organ systems (except for the lungs) [Study suggestion: Review Figure 162 From this diagram, which speci c chamber of the heart begins the pulmonary circulation Which speci c blood vessels end the pulmonary circulation What particular heart chamber begins the systemic circulation What particular blood vessels end the systemic circulation ]

Pulmonary circulation Systemic circulation AORTIC ARCH To tissues SVC To lungs CPA LA Pulmonary veins

Fig 162 The major heart pumps and types of blood vessels (A) The major chambers and vessels attached to the heart (B) Smaller blood vessels

The four-chambered human heart (two upper atria, two lower ventricles) plus a double circulation (pulmonary circulation plus systemic circulation) is pretty typical of the heart and circulation found in both birds and other mammals Being endotherms (or homeotherms) that regulate their own internal body temperature ( 12), birds and mammals have a great need for energy and oxygen to keep their body heat always at a fairly high level A double circulation plus powerful four-chambered heart provide both the required force to pump a large volume of heated blood and a separate pulmonary circulation that adds plenty of oxygen to the blood The pulmonary (right-heart) circulation in mammals, therefore, is specialized for adding oxygen to the bloodstream But the systemic (left-heart) circulation specializes in extracting oxygen from the bloodstream and delivering it to the tissues of the major organ systems In the process, carbon dioxide is picked up from the tissues The circulation in vertebrates that are heterotherms (poikilotherms), such as sh, amphibians, and reptiles, is quite another matter Fish have a twochambered heart with only a single circulation Amphibians rely upon a three-chambered heart (two atria, one ventricle) beating within their chests Reptiles, likewise, possess a three-chambered heart, with two atria and one ventricle that is partially subdivided Both amphibians and reptiles have double circulations, but there is much less specialization of function of the two circulations

The powerful four-chambered heart of humans and other mammals has a complex internal anatomy (Figure 163) Consider, for example, the myocardium (my-oh-CAR-dee-um) or heart (cardi) muscle (my) The cardiac muscle bers of the myocardium are arranged in a fairly circular pattern around the heart, so when they contract, they squeeze the blood out of the heart chambers like a noose tightening around a bag The blood from the atria is pushed down into the ventricles, through a pair of one-way valves Not surprisingly, these valves are called the right and left atrioventricular (aytree-oh-ven-TRIK-you-lar) valves These two A-V (atrioventricular) valves essentially act as one-way doors They are actually aps of connective tissue that are pushed open from above by blood in the atria

Intercalated discs (intercellular bridges)

Myocardium (cardiac muscle fibers)

The atria contract because they are excited by cardiac pacemaker cells These pacemaker cells are actually modi ed cardiac muscle bers that are self-exciting Sodium (Na ) and other charged particles are automatically let into the pacemaker cells at a certain rate or rhythm This happens because the proteins in the membranes of the pacemaker cells tend to shift around, allowing ions to enter and excite the pacemaker cells or turn themselves on The main cardiac pacemaker area is called the sinoatrial (sigh-no-AY-treeal) or S-A node (NOAD) This region is called a node because it is somewhat