Circulatory system

Reason for creation
The circulatory system has evolved to allow a good supply of nutrients and oxygen to the tissues. This could no longer be provided by diffusion, which is significantly inefficient (slow) over long distances. In animals with small body size, however, diffusion amply replaces the circulatory system.

Systems
There are two basic types of circulation systems.
 * Open system - this is a system in which blood is pumped into haemocoels (open blood spaces).
 * Closed system - is the one we have, for example. The blood is pumped in it in a closed circuit, in which the blood circulates.

Pumps
For the proper functioning of both open and closed systems, the presence of a pump is required to drive the blood. There are two types of pumps.
 * Peristaltic pump - works like peristalsis of the intestines. The blood is driven by smooth muscle, in which there is a gradual circular contraction.
 * Chamber pump - works by means of valves that open only when pressure is applied from the correct side. They will not open the other way round. The contraction occurs either by its own contractile wall (i.e. the pump wall is made of muscle) or by pressure from surrounding tissues (most commonly skeletal (i.e. striated) muscle contraction).

The human circulatory system contains a chamber-type pump with its own contractile wall, and even one that consists of four subunits (two main pumps (chambers) and two auxiliary pumps (atria)). But that is not all. Our circulation system also includes a second type of pump - the peristaltic pump. This type is found in the large veins of the lower limbs. It is called the muscular pump. This pump works against the force of gravity (if the person being observed is standing) and downstream of the direction of blood flow. It is helped by the valves.

Types of circulation
There are again two basic types of circulation:
 * Simple circulation - there is only one circulation, in which both the pump and the place for oxygenation of the blood are arranged in a row. Thus, there is no pulmonary and body circulation as in the other type of circulation.
 * Double circulation - double is called because it contains two circulations - one pulmonary and one corporal. The two are also arranged in series (i.e. they are connected in series), but both have their own pump. However, the two have different pressures, which is why the pulmonary circulation is called low pressure and the corporal circulation is called high pressure.

Heart
Ventricle wall thickness
 * right ventricle: 3-4 mm;
 * left ventricle: 16-20 mm;

Koch's triangle
 * bounded by the base of the septal tip of the tricuspid valve, the sinus coronarius orifice into the right atrium, and a lash extending from the v. cava inferior orifice into the right ventricle to the septum (in the depth of this lash is Todaro's tendon attaching to the trig. fibrosum dextrum); subendocardially, the nodus atrioventricularis is located in Koch's triangle.

Valsalva's sinuses
 * sinus aortae (dexter, sinister, posterior) - extension of the ascending aorta above the individual valvulae of the aortic valve, the right and left coronary arteries branch off from the right and left sinus of Valsvalva.

Pressure parameters

 * central venous pressure: 0-8 mmHg;
 * wedge pressure: 4-14 mmHg;


 * pressure in the right atrium: 0-8 mmHg;
 * pressure in the right ventricle: systolic 25-30 mmHg (enddiastolic 0-8 mmHg);
 * pressure in the truncus pulmonalis: 25-30 mmHg;


 * pressure in the left atrium: 4-12 mmHg;
 * pressure in the left ventricle: systolic 100-140 mmHg (enddiastolic 4-12 mmHg);
 * pressure in the aorta: 100-140 mmHg;

Other hemodynamic parameters

 * CO: 4–8 l/min;
 * CI: 2.5-4.2 l/min/m2 (CO/body surface);
 * ejection fraction: 60-75%;

Related articles

 * Blood vessels
 * Blood
 * Fetal Blood Circulation
 * Heart