The process of metabolism of food particles occurs in the presence of oxygen, produce carbon dioxide and nitrogenous waste products in the cell. Therefore cell require oxygen, food particles and carbon dioxide, waste products must be eliminated from the cell which takes place by means of Transportation.

In unicellular organism food particles and oxygen reach the cell by Diffusion through the body surface. Carbon dioxide, waste materials and excess of water and salts can also be excreted from the cell through the body surface by Diffusion.

Hydra is a diploblastic animal. The Ectoderm and Endoderm of it are in direct contact with the external and internal environment respectively. That is why all necessary and unnecessary things obtained and eliminated by the process of Diffusion.

Planaria has a flattened body and cells are not very deep from the body wall. That is why by the process of diffusion the gaseous exchange takes place through the surface of body.

For the transportation of food particles, intestine is present. It divides into small branches from which food particles diffused in each cell of the body.

For excretory products, it has an excretory system.

A well developed transportation system and blood circulation is present in the animals of Annelida and other big animals. They have a big structure and cells lie very deep in the body so they need a well developed system.

In Earthworm the circulatory system consists of vessels and is known as Closed Type circulation.

There are three longitudinal vessels present in the whole body of Earthworm which communicated with each other by transverse vessels.

Longitudinal vessels give branches which form capillaries on different parts of the body.

Two types of transverse vessels are present which connect the longitudinal vessels.

1. Heurts: These are four pairs of vessels present in 7^th, 9^th, 12^th and 13^th segments of the body.
2. Anterior Loops: These are two pairs of vessels present in 10^th and 11^th segment of the body

In grasshopper blood is found in the body cavity instead of vessels i.e. vascular system is absent. Hence circulation is of Open Type.

Hemoglobin is absent in the blood, which is necessary for the transportation of gases. So for this, there is another system of Trachae while food particles and waste products are transported through blood.

Its cavity, which contains blood, is known as Haemocoel. The Haemocoel is divided into three parts with the help of two perforated Diaphragms. Due to the presence of pores in the diaphragm, blood can move from one part to the other part of haemoccoel. These diaphragms are known as Dorsal and Ventral Diaphragm.

The portion above the Dorsal diaphragm is called Pericardial Sinus. The portion below the ventral diaphragm called Perineural Sinus while the portion in between the two diaphragm called Perivisceral Sinus.

In pericardial Sinusa tube like structure is present which consists of 6-7 chambers of heart and Aorta. The movement of heart is maintained by Alary Muscles. When blood reach the pericardial sinus, it pumped forward by heart and aorta and regulate the circulation of blood in the body.

In human, transportation of different things takes place by blood circulation. Blood circulation in human is of closed type. The circulatory system consists of a muscular heart and blood vessels.

It is a muscular organ present in the thoracic cavity, slightly on the left side in between the two lungs. It is a hollow organ with conical structure.

The circulation of blood is maintained by the pumping of the heart. Human’s heart in normal condition pumps 72 times/minute. This is called Heart Beat.

Heart consists of four chambers, upper two are Atria and lower two are Ventricles. A longitudinal septum divides the heart into two Right and Left halves. Flowing are the four separate chambers of the heart.

1. Left Atrium
2. Left Ventricle
3. Right Atrium
4. Right Ventricle

A longitudinal section helps in studying the heart internally. The two Atria are separated from each other by means of a septum known as Inter auricular septum. The opening between the atria and ventricles are called Auriculo-ventricular aperture.

The auriculo-ventricular aperture of right Atrium and right ventricle contain three cup like structures called Cusps. So it is called Tricuspid Valve. The opening between left atrium and left ventricle contain two cusps and it is called Bicuspid Valve or Mitral Valve.

The two ventricles are also separated by a longitudinal septum known as Interventricular septum. The walls of the ventricles are thicker than the Atria. Its walls show muscular projections in the cavity of vantricles called Papillary muscles from which fibres (Chordae Tendinae) originated and attached to the lower surface of the cusps of tricuspid and bicuspid valves. They help in the maintenance of position of the cusps which prevent the backward flow of blood during contraction of the ventricles.

Right ventricle opens into the Pulmonary Trunk while left ventricle into Ascending Aorta. Their openings contain Semilunar valves, which prevent the backward flow of blood.

Blood from all parts of the body, which is deoxygenated brought to the right atrium by two large veins, the Superior Vena Cava and Inferior Vena Cava.

Four pulmonary veins carry oxygenated blood from the lungs to the left ventricle of the heart. On contraction of both atria, the blood enters the ventricles of the respective sides. As ventricles contract, the deoxygenated blood from right ventricle pumps into the lungs by pulmonary trunk while oxygenated blood from left ventricle pumps in the different parts of the body through Aorta.

Human’s heart contains two types of blood at a time so it is called Double Circuit Heart. The blood from all parts of the body except lungs enter the right atrium from there it is pumped into the lungs by ventricles. This blood after oxygenation bring back in the left atrium of heart and supplied to the different parts of the body, thus two circuits completed. The circuit between heart and lungs are called Pulmonary Circulation and circuit between heart and different parts of the body called Systemic Circulation.

There are two types of blood vessels:

The walls of the veins are thinner than the arteries. The wall composed of three layers, the outer layer of Collagen fibres, middle of Smooth muscles (less thicker than arteries) and inner layer is made up of Endothelium. Lumen have big diameter than arteries, which minimizes the resistance to flow and blood can flow against the gravity. The valves are also present, which prevent the backward flow of blood.

The smaller branches of artery are called Arterioles, which further divided into fine branches of capillaries. These fine vessels unite again to venules, which turn into veins.

Capillaries are made up of Endothelium. It is the place where exchange of different things takes place. Blood enters the capillaries from arterioles contain large amount of food particles and oxygen.

These things are secreted into the cells and carbon dioxide and excretory materials are reabsorbed from cells into the blood of capillaries, which bring back to the heart.

The blood from the left ventricle pumped into the Aorta. This is oxygenated blood and supplied to the different parts of the body through the branches of Aorta. Aorta is divided into three parts:

After arising from the left ventricle, aorta moves upward and called Ascending Aorta. It gives Right and Left Coronary Arteries initially, which supply blood to the muscles of the heart.

Ascending Aorta moves backward and down ward towards the dorsal side of the heart and forms an arch called Arch of Aorta. It give three branches:

It arises from the right side of the aorta, it is further divided into two branches:

It supplies the right upper limb.

It is the second branch of arch of Aorta and supplies blood to the left side of head, neck and brain.

It supplies the left upper limb.

On the dorsal side of heart, aorta runs down ward and called Descending Aorta. In the region of thorax, it is called Thoracic Aorta and in abdomen it is called Abdominal Aorta.

It gives several branches named intercostal and bronchial arteries, which supply intercostal muscles and lungs respectively.

It gives following branches:

It is the paired branch which arises from the side of aorta and supplies diaphragm.

Coeliac artery arises from the ventral side and divided to supplies liver, stomach, duodenum, pancreas and spleen.

Ventral branch of aorta supplies blood to the small intestine and part of colon.

Renal arteries are the paired branches, which supplies blood to the reproductive organs.

Genital Arteries are paired branches, which supplies blood to the reproductive organs.

Lumber Arteries are 4-5 pairs of branches, which supply blood to the back muscles of the lower region.

Ventral branch supplies the remaining part of colon and rectum.

Dorsal branch supplies the lower region.

Terminal branches of aorta present on both sides and each artery further divided into internal and external branches. Internal Iliac supplies blood to the lower organs while external Iliac supplies blood to the lower limbs.

The Pulmonary Aorta originates from the right ventricle carries deoxygenated blood and divides into right and left pulmonary arteries for both lungs.

Two large veins carry deoxygenated blood from the body to the right atrium of the heart.

It carries the blood from the anterior part of the body and forms by the union of two brachiocephalic veins, bronchial veins and single right-sided Azygos veins.

Right and left brachiocephalic veins from by the union of following veins:

1. Jugular vein carry blood from the head, neck and brain.
2. Subclavian veins carry blood from the upper limbs.

   They carry blood from lungs.

From intercostal muscles and opens in superior vanacava on the right side.

Forms by the union of Iliac veins. It runs upwards and enters the right atrium of heart. It receives following branches:

They are formed by the fusion of External Iliac (from lower limb) and Internal Iliac (from the organs of the pelvis). It receives a paired Ilio-lumber veins, which collect blood from lower part of the back.

These are four pairs collect blood from lower region of back.

They collect blood from reproductive organs.

Renal veins are the veins, which collect blood from kidneys.

These are the veins, which collect blood from liver.

In human, Hepatic Portal System is present which consists of Hepatic Portal Vein forms by the union of small veins of Alimentary canal:

1. Gastric Vein from stomach
2. Splenic Vein from spleen
3. Pancreatic vein from Pancreas
4. Anterior mesenteric vein from small intestine and part of colon.
5. Posterior Mesenteric vein from colon and rectum.

Four pulmonary veins carry oxygenated blood from the lungs to the left atrium of Heart.