MICHAEL JOSEPH JACKSON

DOUBLE CIRCULATION OF BLOOD IN HEART

ANIMATION OF THE CIRCULATION OF THE BLOOD

Double Circulation of the Blood refers to the passage of the blood firstly through the lungs (the pulmonary circulation - where it picks up oxygen and releases carbon dioxide) and then through the body (the systemic circulation) where it delivers its cargo of oxygen and picks up carbon dioxide. These two circuits are powered by different sides of the heart. The right side of the heart pushes the blood at relatively low pressure through the lungs. The left side of the heart pushes the blood at relatively high pressure through the whole body.

The circulation has been unravelled and the two sides of the heart have been separated. This makes it clear that there is really only one circulation but that it happens in two stages (in series). The right side of the heart (at left of graphic) pushes the blood through the lungs (at top of graphic). The passage of carbon dioxide is illustrated as a flow of blue particles from the body and out through the lungs. The intake of oxygen through the lungs and to the body is illustrated as a flow of yellow particles. The vascular system (blood vessels) is illustrated as a tube connecting the right heart to the lungs, the lungs to the left heart, the left heart to the body and the body back to the right heart. The red blood cells can be glimpsed moving within this tube.

The system of vessels and the heart is known as the cardiovascular system. The heart is really a highly specialised segment of vessel that is muscular and supplied with valves (heart valves) to create the one way flow of blood. In the heart, the two sides are joined and the complex plumbing of vessels makes the flow rather difficult to understand.

BLOOD FLOW THROUGH THE HEART

1. Deoxygenated blood returning from the body enters the heart through the superior vena cava and inferior vena cava.

2. Blood passes into the right atrium and right ventricle

3. Right ventricle pushes the blood through the pulmonary arteries

4. Blood passes through the lungs where it loses carbon dioxide and picks up oxgen

5. This oxygenated blood returns to the heart via the pulmonary veins

6. Blood enters the left atrium and left ventricle

7. The left ventricle pushes the blood out through the main artery, the aorta

8. Blood travels to all parts of the body where it delivers oxygen and picks up carbon dioxide

THE CORONARY ARTERIES branch from the aorta as soon as it emerges from the heart (please see diagram of the heart at left). They deliver oxygenated blood the the heart muscle. Coronary artery disease (or coronary heart disease) involves the build up of deposits in these crucial vessels. This reduces and sometimes completely blocks the flow of blood resulting in a heart attack.

• ARTERIES: are vessels that take blood away from the heart
• VEINS: are vessels that bring blood towards the heart
• ATRIUM: smaller chamber of the heart through which blood enters the heart
• VENTRICLE: larger chamber of the heart which pushes blood away from the heart
• AORTA: major artery carrying blood away from the left ventricle
• VENA CAVA: main vein returning blood to the right atrium
• CORONARY ARTERIES: the first vessels to branch from the aorta; they supply blood to the heart muscle

SOURCE: www.rkm.com

LYMPHATIC SYSTEM

ENTIRE LYMPHATIC SYSTEM

The lymphatic system is a complex network of lymphoid organs, lymph nodes, lymph ducts, lymphatic tissues, lymph capillaries and lymph vessels that produce and transport lymph fluid from tissues to the circulatory system. The lymphatic system is a major part of the immune system.

The lymphatic system has three interrelated functions: (1) removal of excess fluids from body tissues, (2) absorption of fatty acids and subsequent transport of fat, as chyle, to the circulatory system and, (3) production of immune cells such as lymphocytes (e.g. antibody producing plasma cells) and monocytes.

Lymphatic circulation

Unlike the blood system, the lymphatic system is not closed and has no central pump. Lymph movement occurs slowly with low pressure due to peristalsis, valves, and the milking action of skeletal muscles. Like veins, lymph travels through vessels in one way only, due to semilunar valves. This depends mainly on the movement of skeletal muscles to squeeze fluid through them, especially near the joints. Rhythmic contraction of the vessel walls through movements may also help draw fluid into the smallest lymphatic vessels, capillaries. Tight clothing can restrict this, thus reducing the removal of wastes and allowing them to accumulate. If tissue fluid builds up the tissue will swell; this is called edema. As the circular path through the body's system continues, the fluid is then transported to progressively larger lymphatic vessels culminating in the right lymphatic duct (for lymph from the right upper body) and the thoracic duct (for the rest of the body); both ducts drain into the circulatory system at the right and left subclavian veins. The system collaborates with white blood cells in lymph nodes to protect the body from being infected by cancer cells, fungi, viruses or bacteria. This is known as a secondary circulatory system.

Development of Lymphatic Tissues

Lymphatic tissues begin to develop by the end of the fifth week of embryonic life. Lymphatic vessels develop from lymph sacs that arise from developing veins, which are derived from mesoderm.

The first lymph sacs to appear are the paired jugular lymph sacs at the junction of the internal jugular and subclavian veins. From the jugular lymph sacs, lymphatic capillary plexuses spread to the thorax, upper limbs, neck and head. Some of the plexuses enlarge and form lymphatic vessels in their respective regions. Each jugular lymph sac retains at least one connection with its jugular vein, the left one developing into the superior portion of the thoracic duct.

The next lymph sac to appear is the unpaired retroperitoneal lymph sac at the root of the mesentery of the intestine. It develops from the primitive vena cava and mesonephric veins. Capillary plexuses and lymphatic vessels spread form the retroperitoneal lymph sac to the abdominal viscera and diaphragm. The sac establishes connections with the cisterna chyli but loses its connections with neighboring veins.

The last of the lymph sacs, the paired posterior lymph sacs, develop from the iliac veins. The posterior lymph sacs produce capillary plexuses and lymphatic vessels of the abdominal wall, pelvic region, and lower limbs. The posterior lymph sacs join the cisterna chyli and lose their connections with adjacent veins.

With the exception of the anterior part of the sac from which the cisterna chyli develops, all lymph sacs become invaded by mesenchymal cells and are converted into groups of lymph nodes.

The spleen develops from mesenchymal cells between layers of the dorsal mesentery of the stomach. The thymus arises as an outgrowth of the third pharyngeal pouch.

SOURCE: WIKIPEDIA