CARIOVASCULAR SYSTEM

Cardiovascular System

Cardiovascular System

Introduction

The heart weighs 300 grams and is shaped like a grapefruit and has two atria, two ventricles, and four valves receive blood from both venae cavae and the four pulmonary veins, and throw it into the aorta and pulmonary trunk. The heart pumps blood to 9 liters per day, making from 60 to 160 beats per minute.

The heart is covered with a dense fibrous membrane - the pericardium, forming serous cavity filled with liquid, which prevents friction when it decreases. The heart consists of two pairs of chambers - the atria and ventricles, which act as separate pumps. The right half of the heart "pumps" venous-rich carbon dioxide blood through the lungs, it is - a small circulation. The left half throws oxygenated blood that is passed from the lungs into the systemic circulation. Venous blood from the upper and lower hollow vein enters the right atrium. Four pulmonary veins deliver arterial blood to the left atrium (Aronson & Ward, 2007).

Atrioventricular valves are of special thin papillary muscles and tendinous filaments attached to the ends of the sharp edges of valves. These structures are fixed valves and prevent them from "falling through" (prolapse) back into the atrium during ventricular systole. The left ventricle is formed by thick muscle fibers than the right because he is opposed to higher pressure of blood in the systemic circulation and should make greater efforts to overcome it during systole. Between the ventricles and extending from them aorta and pulmonary trunk are semilunar valves. The heart is located in the chest behind the breastbone and in front of the descending part of the aortic arch and esophagus. It is fixed to the central muscle bundle diaphragm. Both sides are located in one lung. At the top are the major blood vessels, and place the division into two main tracheal bronchus.

Contraction of the Heart

During diastole atrial, blood flows from the upper and lower hollow vein into the right atrium, and the four pulmonary veins into the left atrium. Flow increases during inspiration, when the negative pressure inside the chest helps to "suction" of blood to the heart, as the air in the lungs. Normally, it can manifest respiratory (sinus) arrhythmias.

Atrial systole ends, when the excitation reaches the atrioventricular node and extends along the branches of bundle branch block, causing ventricular systole. Atrioventricular valves quickly slammed shut, tendon fiber and ventricular papillary muscles prevent them from screw driving (prolapse) into the atrium. The venous blood fills the atria during diastole and ventricular systole (Levick, 2010).

Distribution and Blood Flow

Blood in the vessels is not distributed evenly throughout the circulatory system. At any given time, approximately 12% of the blood in the arteries and veins that carry blood to the lungs and from the lungs. About 59% of the blood is in the veins, 15% - in the arteries, 5% - in the capillaries and the remaining 9% - in the heart. The rate of blood flow is not uniform across all parts of the ...