Double circulation in mammals

Double circulation occurs in mamamals due to the lungs.The blood passes through the heart in the circuit twice.Blood flows from the main circulation of the body to the heart, then to the lungs and back to the heart again before it is punmped into the main circulation .Veins carry deoxygenated blood from variousparts of the body to theheart. From the heart, the pulmonary arteries carry blood to the lungs. Thge oxygenated blood returns to the heart by the pulmonary veins. Generally, the circulation linking the lungs to the heart is known as the pulmonary circulation. When the oxygenated blood leaves the left side of the heart and is distributed by the arteries to the rest of the body, apart from the lungs. The veins carry the blood from all parts of the body back to the right side of the heart.This circulation is called the systemic circulation. There are many advantages the pulmonary circulation and the systemic circulation allows. Blood entering the lungs is at a low pressure and therefore, it ensures that the blood is well oxygenated before it is returned to the heart. The blood leaving the heart for systemic circulation is at a high pressure. This ensures that the oxygenated blood is well distributed to the parts of the body at a faster rate. Additionally, it helps to maintain a high rate of metalbolic in animals.

Description of the heart

The heart of a mammal is a complicated organ. The size of the heart varies with the animal and in man it is about the size of a clenched fist. It lies in the thorax behind the chest-bone and the two lungs.The heart is surrounded by a two-layed bag known as the pericardium, the inner membrane being in contact with the heart. Right between the two pericardial membranes is the pericardial fluid which helps to reduce friction when the heart is beating.

Generally,the heart heart weighs 0.59% of the total body mass.

More about Coronary artery disease

This happens when most of the heart gets blood it needs through the two coronary arteries. When the arteries are blocked, the heart may die due to the reason of the lack of blood. Coronary artery disease is traceable to atherosclerosis. The arteries changed from being smooth and elastic to rough, inflexible and lastly smaller as compared to before. As a result, being narrow, the volume of blood that can be transported is reduced. Soon, the coronary arteries are clogged by cholesterol and fat deposits and therefore, resulting to the obstruction of the blood flow.During a heart attack, the blood flow to a particular part of the heart that may be blocked, and hence the region of the heart muscle dies. The body can recover if only a small area of muscle dies but extensive muscle damage is fatal.

What causes heart murmurs?

Usually, doctors will call the sound heard with a stethoscope as heart murmurs.They are noises the blood makes as it rushes through the parts of the heart. in some cases, murmurs shows the malfunctioning valves. If a valve does not close properly, it allows some of the blood to leak becomes audible through a stethoscope. Additionally, heart mumurs that are due to disease would occur due to the changes in the mitual valve, a valve that is positioned between the left upper and lower chamber. Babies born with a malfunctioning valve, may have rheumatic fever but these abnormalities can be corrected by surgery.

Parts of the heart

Credits:http://www.biomaterials.org/SIGS/Cardiovascular/images/cv_anatomy_heart.jpg

Chambers of the heart:The heart id divided into 4 chambers; 2 thin-walled atria, Which receive venous blood, and two larger, thick-walled ventricles, which pump blood into the arterial system.

Aortic valve:Blood is pumped through here from the left ventricle into the aorta.

Superior vena cava (SVC):Drains blood from the head, neck and upper body into the right atrium.

Pulmonary veins:One of four veins draining blood from lungs into left atrium.

Pulmonary artery:Carries deoxyenated blood from right ventricle via the pulmonary trunk to the lungs.

Right atrium:Receives deoxygenated blood from the SVC and IVC.

Left atrium:Receives oxygenated blood from the pulmonary veins.

Tricuspid valve:Prevents backflow of blood into right atrium from right ventricle.

Inferior vena cava (IVC):Drains blood from the lower body into the right atrium.

Conus arteriosus:Smooth-walled exit from right ventricle to the pulmonary valve at the root of the pulmonary artery.

Mitral Vave:Prevents backflow of blood into left atrium from left ventricle.

Interventricular septum:Partition between the ventricles; mostly muscular but thin and membranous in its uppermost part.

Chordae tendineae:Anchor valve flaps to papillary muscles in ventricular wall.Apex of heart:Tip of left ventricle.

Credits:
Chambers Of The Heart Pg 74:Name:Handbook Of The Human Body, Author: Professor Peter Abrahams, first published in 2006 by Amber Books Ltd, Bradley's Close, 74-77 White Lion Street, London N1 9PF, United Kingdom

The Circulatory System

Circulatory System:
The heart pumps blood to the lungs. Then it pushes the blood all through the body to deliver oxygen and collect waste. Blood carrying waste from the body cells is drawn through large veins, called the vena cavae, into the right side of the heart. Then the blood is pumped through pulmonary arteries to the lungs. Here it collects oxygen, and is pumped back through pulmonary veins to the left side of the heart.The heart then pumps the oxygen-rich blood out through the main artery, called the aorta. From here, it travels round the body.

Credits:
Circulatory System (page 9), Name: The Human Body (A fascinating see-through view of how our bodies work), Author: Dr. Peter Abrahams, University College London, Text Consultant: Dr. Luisa Dillner, Medical Advisor: Dr. Tom Snow, published in Australia in 1993 by Wishing Well Books, 67 Rushdale Street, Knoxfield, Victoria, 3180.

How does the heart work?

Blood rich in carbon dioxide will enter the right atrium. Blood from the upper parts of the body will drain into the superior vena cave while blood from the lower part of the body will enter through the inferior vena cave. After it enters the right atrium, it wnters the right ventricle through the tricuspid valve. The right ventricle will pump the blood rich in carbon dioxide through the lungs. The blood will then go into the pulmonary arteries to the right lung and the left lung. Gas exchange takes place. The oxygen rich blood flows back into the left atrium through pulmonary veins. Blood from the left atrium flows into the left ventricle through the bicuspid valve. Then, oxygenated blood moves up by the left ventricle though the aortic arch to the rest of the body.