Get a free home demo of LearnNext

Available for CBSE, ICSE and State Board syllabus.
Call our LearnNext Expert on 1800 419 1234 (tollfree)
OR submit details below for a call back


Transportation in Animals

Have a doubt? Clear it now.
live_help Have a doubt, Ask our Expert Ask Now
format_list_bulleted Take this Lesson Test Start Test

Transportation in Animals - Lesson Summary

Circulatory system
The system which pumps the fluid tissue to transport it throughout the body is called the circulatory system. Human circulatory system comprises of heart, blood and a network of blood vessels. The system transports oxygenated blood from lungs and the heart throughout the body via arteries. The oxygenated blood is supplied to all the organs by arteries branching out as capillaries. The deoxygenated blood is returned to veins through capillaries. These veins carry deoxygenated blood to the heart and the lungs.

Human heart

The heart is the central organ for pumping the blood throughout the body.  Heart is made up of strong cardiac muscles. It is located in the chest cavity with its lower part pointing towards the left. Its size is that of the person’s fist. It pumps blood rich in carbon dioxide to the lungs and oxygen-rich blood to other parts of the body. 

  • The heart consists of four chambers namely auricles and ventricles. The two upper chambers of the heart are known as the auricles.
  • The two lower chambers of the heart are the ventricles. Left and right parts of the heart are separated by a muscular partition called as septum.
  • Heart has number of valves which allow the blood to flow in one direction. These prevent the oxygenated blood mixing with de-oxygenated blood. 
  • SA node, the natural and primary pace maker of the heart is located in the upper wall of the right atrium in the heart.
  • AV node, the secondary pace maker is located in the bundles of tissues on the border between right atrium and right ventricle of the heart.

Blood vessels
Blood vessels are tube like structures which form an intricate network to transport blood to various parts of the body. They are classified as arteries, veins and capillaries. 
a) Arteries are the blood vessels which carry pure oxygenated blood from the heart to different tissues in the body. Arteries are with thick walls as the heart pumps blood with greater pressure into the arteries. Inturn arteries also offer some pressure on the blood. This is called as peripheral resistance. Pulmonary artery carries impure blood to the lungs from heart 

b) Veins arise from the bodily tissues. Thus deoxygenated blood is carried by veins and is returned to heart. All the veins carry impure blood to the heart except for pulmonary veins which carry pure blood from lungs to the heart. Veins have wider inner diameters and valves to prevent the back flow of blood. Blood is just allowed to go towards the heart and not in any other way. The walls of veins are thinner when compared to the walls of the artery.  Pulmonary veins carry pure blood from lungs to the heart. Pulmonary veins need not have thicker walls as such as blood is not pumped by the heart in to these veins. They carry pure blood from lungs. They have valves in them so as to prevent backward flow of the blood. There are totally four pulmonary veins and all of them are connected to left atrium of our heart.

c) Blood capillaries are the structures which branch out form arteries on entering the tissues. Blood capillaries supply pure blood to inner parts of the tissue. These capillaries in turn collectively form a single vein from the tissue. The heart pumps deoxygenated blood into the lungs through pulmonary arteries.
Pulmonary artery carries impure blood to the lungs from heart . Blood gets purified in the lungs.  Pulmonary veins carry pure oxygenated blood from lungs to the heart. 

Functions of the heart

  • All parts of our body require oxygen to carry out life processes. We take in oxygen by the process of respiration. But this oxygen should be carried over to all parts of the body.The oxygen in the lungs binds to  hemoglobin present in the blood. This oxygenated blood is taken to heart. This oxygen carrying blood should be transported to all the parts of our body. To pump this blood with pressure we need a central pumping organ called as heart. This is the reason why our heart pumps continuously.  
  • It is a central pumping organ of the circulatory system which pumps oxygenated (pure) blood into the blood vessels to be carried over to different parts of the body.
  • It receives deoxygenated (impure) blood from different parts of the body and sends it to the lungs for purification.

Blood and lymph are the important modes of transport in the circulatory system. Blood is a fluid tissue made from plasma and formed elements.

  • Plasma is a pale yellowish fluid that contains albumin (the chief protein constituent), fibrinogen (responsible, in part, for the clotting of blood) and globulins (including antibodies). Plasma is obtained by separating the liquid portion of blood from the cells. Plasma serves a variety of functions like maintaining a satisfactory blood pressure and volume, serving as the medium for exchange of vital minerals, maintaining a proper pH in the body. It also helps in transporting gases, nutrients and nitrogenous waste.
  • Red blood cells in the blood are flattened disc like structures responsible of transporting oxygen and carbon dioxide gases. Red blood cells consist of red iron-containing pigment called as haemoglobin. Haemoglobin is a respiratory pigment that carries oxygen through red blood cells. Oxygenated blood is carried to tissues. 
  • White blood cells are otherwise known as leukocytes. WBCs help the body in fighting against the diseases. Different types of WBCs are Granulocytes, Monocytes and Lymphocytes. Granulocytes are further divided into Neutrophils, Eosinophils and Basophils. Monocytes can transform themselves into two types of cells namely, Dendritic cells and Macrophages. Lymphocytes can be of two types namely B-lymphocytes and T-lymphocytes.
  •  Platelets are the non nucleated, irregular cells which bring about clotting of the blood.These are also called as thrombocytes as they release thromboplastin which plays an important role in clotting of blood. Platelets immediately come to the place of injury and lyse themselves to release thromboplastin. The remnants aggregate in large amounts to form a plug on the injury preventing the blood loss.

Functions of blood
Blood plays a vital role in transporting many substances to all parts of the body.

  • As the blood contains RBCs, it transports oxygen from lungs to cells and in turn carries carbon dioxide in the opposite direction.
  • Urea , the main excretory product formed in the liver is carried away by the blood to kidneys.
  • Blood transports soluble digested food materials which are absorbed in the small intestine.
  • Blood provides a medium of transport for the hormones secreted by different endocrine glands to reach their   target organs.
  • Blood also transports water required by the cells to perform various biochemical reactions.

Lymph is a clear fluid sometimes white in colour comprises of white blood cells mainly lymphocytes. Lymph is a colourless fluid that contains less protein than plasma, and lacks RBC. These cells also attack bacteria entering the cells. Lymph also contains the fluid from the intestine containing proteins and fats.  Lymph helps in carrying absorbed fat molecules from the intestine to different parts of the body.The composition of lymph varies with that of blood plasma.  When the lymph is produced from the intestine, it is thick milky white solution rich in triglycerides.   

Types of circulation
The two types of circulation are single circulation and double circulation. 

  • Single circulation is the type of circulation in which blood passes through the heart only once through the heart. For example, it is seen in fishes. Fish is a lower vertebrate with a two chambered heart. Fish has a two chambered heart comprising of one atrium and one ventricle. Gills help in purifying the deoxygenated blood. This two chambered heart exhibits single mode of circulation. Impure blood is pumped to gills for oxygenation. This oxygenated blood from gills is supplied directly to the body tissues without sending to the heart. 
  • Incomplete double circulation is observed in amphibians and reptiles which have three-chambered hearts with two atria and one ventricle. 
  • Double circulation is the type of circulation during which blood passes twice through the heart. Higher vertebrates like birds and mammals exhibit double circulation. 

Blood pressure

Blood pressure is the pressure exerted by the blood on the walls of the arteries.

  • The pressure can be systolic pressure during contraction and diastolic pressure at relaxed state.
  • The pressure exerted by blood against the wall of an artery during ventricular contraction or systole is called systolic pressure, and that exerted during ventricular expansion or diastole is called diastolic pressure. 
  • Normal blood pressure is 120/80mmHg. If the blood pressure is less than 100/50 then it is termed to be low blood pressure or hypotension. If it exceeds 140/90, it is termed to be high blood pressure or hypertension.
  • An instrument called the sphygmomanometer is used to measure blood pressure. The normal systolic pressure is about 120 mm of Hg, and diastolic pressure is 80 mm of Hg.

Transport of gases
We take in oxygen during inhalation and it reaches lungs through respiratory tract. Hemoglobin, an intracellular protein is the primary vehicle for transporting 97% of oxygen in the blood. 3% of Oxygen is carried by plasma. Hemoglobin is contained in erythrocytes. 

  • The amount of oxygen bound to the hemoglobin at any time is related to the partial pressure of oxygen to which the hemoglobin is exposed. In the lungs, at the alveolar-capillary interface, the partial pressure of oxygen is high, and therefore the oxygen binds readily to hemoglobin. As the blood circulates to other body tissue in which the partial pressure of oxygen is less, the hemoglobin releases the oxygen into the tissue because the hemoglobin cannot maintain its full bound capacity of oxygen in the presence of lower oxygen partial pressures.
  • Red blood cells in the blood are flattened disc like structures responsible of transporting oxygen and carbon dioxide gases. Red blood cells consist of red iron-containing pigment called as haemoglobin. Haemoglobin is a respiratory pigment that carries oxygen through red blood cells. Oxygenated blood is carried to tissues. 
  • The exchange of gases at tissue level is called as peripheral gas exchange. The capillaries of circulatory system deliver the oxygen rich blood to the tissues of the body. This oxygen diffuses across the walls of the capillaries into tissues. In turn carbon dioxide diffuses into the blood from tissues. The carbon dioxide diffused into the blood binds to haemoglobin present in the blood to form carboxyhaemoglobin. This de-oxygenated blood is carried to lungs for purification. In the lungs, carbon dioxide from carboxyhaemoglobin dissociates leaving behind haemoglobin. The cycle continues to cary oxygen from lungs to tissues and carbon dioxide from tissues to lungs by haemoglobin. 


Feel the LearnNext Experience on App

Download app, watch sample animated video lessons and get a free trial.

Desktop Download Now
Try LearnNext at home

Get a free home demo. Book an appointment now!