Circulatory System: Features

Circulatory system.
We will discuss:
Blood clotting and blood groups
The heart
Cardiac cycle and
Vascular circulation and blood pressure
The lymph system

The functional organization of a higher animal depends on a cellular differentiation process whereby cells are functionally specialized and operated physiological division of labor among them. For example, a neuron equipped to capture and transmit environmental information, it does not in search of food, defend themselves and reproduce. But you need to live in an environment that ensures their survival. This will produce other cells organized for those purposes.

Supplied to every cell in the body the materials needed for consumption and free of waste products. Blood is the transport vehicle to carry this process besides hormones and other substances. The heart serves as a pump to move blood to all tissues, and reaches through these arteries, arterioles and capillaries. Once the mission to collect the waste products of biochemical reactions of the cells are taken back to the heart through veins.


It consists of various corpuscles: erythrocytes (5,000,000 per cubic millimeter of blood), whose main function is to carry oxygen, WBC (7000 per mm3), involved in the body's defense mechanisms, platelets (300,000 / mm3), allow the process of blood clotting. Besides these there are other components such as proteins (7 per 100), mineral salts (1 per 100) and substances such as urea, glucose, cholesterol, vitamins, hormones, etc.. The total blood volume in the adult male is about 5 liters, or 7 per 100 by weight.

Blood clotting and blood groups

This phenomenon occurs through a protein found in plasma fibrinogen. This is converted to fibrin, and this forms a spongy network that holds the plasma and its components. Blood coagulability is insurance against losses to hemorrhage.

The major blood groups are A, B, AB and O. These react with each other because some protein components of red cells behave as antigens to other individuals and react with these antibodies. Agglutinogens called antigens and antibodies in plasma agglutinins. With this in mind the universal donor group O is not having agglutinogens and group AB is universal recipient having no agglutinins.

The heart

It consists of a special contractile tissue: the heart muscle or myocardium. The heart has four chambers with as many valves. The right atrium receives venous blood from the superior and inferior vena cava and sends the right ventricle through the tricuspid valve. Hence by the contraction of blood passes through the pulmonary valve and goes into the lungs through the pulmonary artery to be oxygenated. Back from the lung enters the left atrium through the pulmonary veins and reaches the left ventricle after mitral valve crossing. Here because of myocardial contraction oxygenated blood out through the aortic valve into the aorta and oxygenated blood is distributed throughout the body. Entire myocardium is dominated by sinus node activity handset thanks to its rate of self-generation transmits these impulses to the entire heart.

Cardiac cycle and
Each comes in 0.8 seconds an impulse cardiac SA node. The atria contract and force blood into the ventricles. When the impulse reaches the AV node causes the contraction of the ventricles (systole). Reversed the momentum to the ventricles relax (diastole) and ventricular pressure and pressure falls. The changes in electrical potential in different regions of the heart is measured by an electrocardiogram. Normally a ventricle ejects about 70 ml of blood with each beat, and as the number of beats per minute is about 70, it launches each ventricle circulation about five liters of blood per minute. This is cardiac output. Cardiac output accommodates the needs of the organism. For example, exercise can make the spending increase to 30-40 liters per minute. The mechanisms that come into play to regulate the heart's work are two: one's own heart and the nervous mechanism, regulated by the sympathetic and parasympathetic whose origin is at the center cardiorregulador located in the medulla.

Vascular circulation and blood pressure

Blood is distributed throughout the system so that as branch arteries and arterioles decreases the diameter of the vessels, but the area is growing capillaries. Although the area of the capillary region is greater, the capillaries contain only 4 per 100 of the blood. The blood velocity is inversely proportional to the cross-sectional area. So the speed in the capillaries is minimal. Moreover, the pressure in the arteries varies between a maximum value, corresponding to ventricular systole and a minimum or diastolic. The difference is known as pulse pressure and normal young people is 40 mm. Hg (120-80). If the arteries become stiff due to illness or age, systolic pressure rise.

The determining factors including the value of blood pressure are cardiac activity and peripheral resistance, and the latter is related to the caliber of the arterioles. The arithmetic mean of systolic and diastolic pressure is 100 mm. Hg. If the individual's needs call for more blood supply, or in the case of increased flow resistance, it is necessary a readjustment of the system. An increase in blood pressure solves. But when the hypertension is chronic is a pathological process. Furthermore, vasodilation, although local, causes a decrease in blood pressure.

Lymphatic system
Is estimated at 3,500,000,000 over the number of capillaries. Due to its structure the components of blood plasma are filtered through them with the exception of large protein molecules. The exchange of substances between plasma and tissue fluid is performed by the difference between hydrostatic pressure and osmotic pressure of plasma proteins. It also has the pressure of tissue fluid and proteins of this, but on a much smaller percentage. When hydrostatic pressure decreases and increases the bulk protein concentration of these, allowing the return of plasma components into the capillaries and the circular system.

But there is a second system-the lymphatic drainage, whose main function is to remove the tissue spaces in excess proteins. This system has its own lymphatic capillaries and is equipped with valves that carry lymph in one direction. This leads to the junction of the right subclavian and jugular veins and enters the general circulatory system.

Related Topics
* Locomotor
* Respiratory
* Sensory apparatus
* Urinary
* Nervous System
* Gastrointestinal

*Automatic Translation