Transportation

"Transportation whether in plants or animals is the key to the efficient assimilation of the nutrients that the organisms synthesize, get from their environment or digest".

1.0Introduction

In unicellular organisms, a single cell carries out all the life processes as the cell itself is the organism. In advanced form like the few-celled algae, protozoa, sponges, etc., the size of the organism ensures that all the cells are not very far from each other. The uptake of materials from the environment is through the general body surface and the transport within the cells is by diffusion. However, more advanced multicellular forms need a transportation mechanism. The sites of absorption and synthesis are very specific and are separated by a greater distance from the other parts of the body.

The actual movement of materials into the individual cells is by diffusion, osmosis or active transport.

2.0Transportation in Human

The process of transporting the absorbed food, gases, water, waste products etc., from one place to another in the body is called circulation.

In human beings, the circulatory (transport) system is divided into two systems :

• (i) Blood Circulatory System (a) Blood (b) Blood vessels (c) Heart
• (ii) Lymphatic System (a) Lymph (b) Lymph vessels (c) Lymph nodes (d) Lymphatic organs

3.0Blood circulatory system:

The circulatory system is the main transportation system of the human body. The body has about 5 liters of blood continuously travelling through it by the way of the circulatory system.

Blood

Blood is an important fluid connective tissue which transports the materials to different body parts.

Composition of blood

Consists of two parts, each with its own job in the body. (i) Plasma (ii) Cellular components

Blood and its components and Blood cells

Functions of blood

• Transportation of oxygen from lungs to tissues.
• Transportation of carbon dioxide from the tissues to the lungs.
• Transportation of excretory materials from the tissues to the kidneys.
• Transportation of digested food from the small intestine to the tissues.
• Distribution of hormones and enzymes.
• Formation of clots to prevent blood loss.
• Distribution of heat and temperature control. Prevention from infections and helps in wound healing.

Blood clotting or Coagulation

When we are injured and start bleeding, the loss of blood from the system has to be minimized. In addition, leakage would lead to a loss of pressure which would reduce the efficiency of the pumping system. To avoid this, the blood has platelets which circulate around the body and plug these leaks by helping to clot the blood at these points of injury.

Blood clot:

Injured tissue + blood platelets releases thrombokinase. Prothrombin $\underset{{\mathrm{Ca}}^{++}}{\overset{\text{thrombokinase }}{\to }}$ Thrombin Fibrinogen $\stackrel{\text{ Thrombin }}{\to }$ Fibrin Fibrin + Dead RBC, WBC and Platelets $\to$ Blood clot Prothrombin and fibrinogen are plasma protein synthesized in liver and are present in plasma.

Why blood does not clot inside a blood vessel?

In the blood plasma, the basophil cells (type of WBC) secrete heparin, which is an anticoagulant. Heparin prevents the blood from clotting within the blood vessels.

4.0Blood Vessels:

In humans, three types of blood vessels are present.

(i) Arteries

These vessels carry blood from the heart to various organs of the body. The walls of the arteries are thick and elastic.

(ii) Veins

They collect the blood from different parts of the body and pour it into the heart. The walls of veins are thin and less elastic. They do not need thick walls because the blood is no longer under pressure, instead they have valves that ensure that the blood flows only in one direction.

(iii) Capillaries

These are smallest blood vessels and one-cell thick. The walls of capillaries are very thin. Exchange of materials between the blood and tissue cells take place at capillaries. Capillaries lack muscular wall and is lined by simple squamous epithelium (endothelium).

The major differences between various blood vessels have been given in Table.

Comparative Study of Blood Vessels

5.0Heart

Size -5 inches length $\times 3.5$ inches wide $\times 2.5$ inches thickness Colour - Reddish brown Shape - Conical Weight - 250-300 gm. The heart is a muscular cone-shaped organ about the size of a clenched fist of the same person. It is located in the upper body (chest area) between the lungs, and with its broad base facing upward and backward and narrow apex directed downwards, forwards and slightly towards the left.

Structure of heart

The heart is enclosed in tough, two layered sac, the pericardium. It is divided into separate right and left sections by the septum or septa. Each of these (right and left) sections is also divided into upper and lower compartments known as atrium or auricle and ventricle, respectively.

The four main chambers of the heart are: (i) Right Atrium (ii) Right Ventricle (iii) Left Atrium (iv) Left Ventricle

It is essential that blood flows in the correct direction through the heart so that the structure of the heart includes a series of valves which ensures that blood does not flow backwards when the atria or ventricles contract.

The Tricuspid valve (Atrioventricular valve) separates the right atrium from the right ventricle. The Pulmonary valve (Semilunar valve) separates the right ventricle from the pulmonary artery.

The Mitral (also known as the Bicuspid) valve is the atrioventricular valve which separates the left atrium from the left ventricle.

The Aortic valve (Semilunar valve) separates the left ventricle from the aorta.

• Coronary circulation is the circulation of blood in the blood vessels that supply the heart muscles. The food and oxygen requirement of heart wall are high in view of its constant beating.
  
  Structure of heart

Working of Heart

The heart functions as a pump in the circulatory system. The right atrium collects deoxygenated blood from two large veins, superior and inferior vena cava. When the atrium contracts, the blood is pumped through the tricuspid valve into the right ventricle. As the right ventricle contracts, the tricuspid valve closes and the blood is pumped into the pulmonary artery through the pulmonary valve. Pulmonary artery carries the blood to the lungs where carbon dioxide is exchanged for oxygen. The left atrium receives oxygenated blood via pulmonary veins. When left atrium contract blood enters into the left ventricle through bicuspid (mitral) valve. Then left ventricle contracts and blood is pumped into aorta through aortic valve. During contraction of left ventricles mitral valve get closed to prevent backward flow into atrium. Valves ensure that blood does not flow backwards when the ventricles contract. \underset{\text { Inferior vena cava }}{\text { Superior vena cava }} \underset{\begin{tabular}{c} \text { Right } \ \text { atrium } \end{tabular}}{\text { Tricuspid }} \underset{\text { Valve }}{\text { Right }} \underset{\text { ventricle }}{\text { Pulmonary }} \xrightarrow[\text { Valve }]{\text { Pulmonary }}\begin{tabular}{c} artery \end{tabular}

Why do ventricles have thicker muscular walls than the atria?

Since ventricles have to pump blood to various organs of the body therefore, they have thicker muscular wall than atria.

Double circulation

In double circulation, the blood passes twice through the heart to supply once to the body. (i) Systemic circulation

In this, blood completes its circulation from left ventricle to right auricle through the body organs.

Oxygenated blood from lungs $\to$ heart $\to$ Systemic arteries $\to$ Body parts $\to$ Systemic veins $\to$ heart (ii) Pulmonary circulation

In this, blood completes its circulation from right ventricle to left auricle through the lungs.

Deoxygenated blood from body $\to$ heart $\to$ Pulmonary arteries $\to$ lungs $\to$ Pulmonary veins $\to$ heart

The right portion of heart is known as pulmonary heart and it has deoxygenated blood. The left portion of heart is known as systemic heart and it has oxygenated blood. Blood vascular system is of two types - open and closed.

• Open - The blood comes in direct contact with the tissue cells. Blood vessels arising from the heart pour the blood into tissue spaces called sinuses. e.g. Arthropods and molluscs.
• Closed - The blood remains in blood vessels during its entire trip round the body and never comes in direct contact with the tissue cells. E.g. Annelids, All vertebrates.

Difference between pulmonary and systemic circulation

6.0Difference between single and double circulation

Single circulation in fishes

Double circulation in mammals and birds In animals that do not use energy for maintaining their body temperature, their body temperature depends on the temperature in the environment. Such animals, like amphibians or many reptiles have three-chambered hearts and tolerate some mixing of the oxygenated and de-oxygenated blood streams.

7.0Blood Pressure:

The force that blood exerts against the wall of vessel is called blood pressure. Blood pressure is of two types. (i) Systolic blood pressure (ii) Diastolic blood pressure

Blood pressure is measured with an instrument called sphygmomanometer. High blood pressure is also called hypertension and is caused by constriction of arterioles which results in increased resistance to blood flow. It can lead to rupture of an artery and internal bleeding. The instrument used to listen to the heartbeat is known as a stethoscope.

8.0Lymphatic System

The Lymphatic system is an open circulatory system. It consists of lymphatic capillaries, lymphatic vessels, lymph nodes and lymphatic organs. Lymph flows in one direction only i.e. from tissues to heart. Lymph is also called white vascular connective tissue.

Capillaries have very fine pores through which blood plasma filters out and starts flowing into the inter cellular spaces. This fluid is called extracellular fluid. A part of this fluid enters into the lymph capillaries. The fluid inside the lymph capillaries is called lymph. Lymph is a transparent fluid which contains blood plasma except blood proteins, RBC and platelets. Lymph enters into lymph capillaries which join together to form large lymph vessels. The lymph vessels finally drain lymph into large veins. The lymphatic nodes occur at intervals in the course of lymphatic vessels. It contains lymphocytes, plasma cells and macrophages. The lymph/tissue fluid filters through the lymphatic nodes. The macrophages remove microorganisms, cellular debris and foreign particles.

Functions of lymph (i) It takes up excess fluid that has diffused out from the blood capillaries and puts it into blood. (ii) It has lymphocytes which fight against germs and bacteria and produce antibodies to fight against infections. (iii) It absorbs and carries digested fats from the intestine. Serve as a middle-man between blood and body.

9.0Transportation in plants

Plants take in ${\mathrm{CO}}_2$, photosynthesize and store energy in leaves. Besides ${\mathrm{CO}}_2$ plants need other raw materials for growth. These raw materials like nitrogen, phosphorous etc., they get from the soil by the roots. These raw materials need to be transported to each and every part of the plant, mainly to the leaves. If the distance between roots and leaves is small, then these raw materials can reach to the leaves easily by the process of diffusion. In case the distance between roots and leaves is more, then proper system of transportation is required.

In plants, transportation is done by a specialized vascular system which is present in the root, stem and leaves.

The vascular system is made up of two types of vascular tissues.

• Xylem
• Phloem

In plants the transport of materials can be divided into two parts. (1) Transport of water and minerals through xylem tissue. (2) Transport of food and other substances through phloem tissue.

(1) Transport of water and minerals [Ascent of Sap]

The plants require water and minerals for making food and performing other functions.

Plants absorb water from the soil through the roots. Thus, water has to be transported upwards to the other parts of the plant. This upward movement of water is called ascent of sap. It is called the sap as it contains many dissolved minerals. Ascent of sap involves root pressure and transpiration pull.

• Ascent of sap is carried out by xylem tissue which consists of - Xylem vessels (2) Xylem tracheids (3) Xylem fibers (4) Xylem parenchyma

In flowering plants, xylem vessels and tracheids both conduct water and minerals upwards. In non-flowering plants, vessels are absent, tracheids are the only conducting cells. In xylem tissue, vessels and tracheids of the roots, stems and leaves are interconnected to form a continuous system of water conducting channels reaching all parts of the plant.

• Absorption of water and minerals The water and minerals are absorbed by land plants from the soil where it is present in the form of soil solution.
  

The main water and minerals absorbing organs are root hairs. The root hairs are directly in contact with the film of water in between the soil particles. Water gets into the root hairs by the process of osmosis. At the roots, cells in contact with soil actively take up ions (actively means by energy expenditure). This creates a difference in concentration of these ions between the root and the soil. Water, therefore, moves into the root from the soil. Hence, there is steady movement of water into root xylem, creating a column of water that is steadily pushed upwards, from cortex to endodermis and from endodermis to xylem vessels and tracheids. This is called lateral transportation. Finally, the water and minerals from the vessel and tracheids move upward by the process called ascent of sap.

• Root pressure The pressure with which the water is pushed up by the xylem of the roots is called the root pressure that is developed in the xylem due to metabolic activity of the root cells. Root pressure explains the transport of water to the leaves and other parts in the case of short plants like the herbaceous plants. However, in tall trees the root pressure is not sufficient to send the water up to the leaves. In these trees, transpirational pull transports water.
• Transpiration pulls and cohesion-tension theory: The main force responsible for upward movement of water is transpiration pull generated in the leaves which pulls the water column filled in the xylem tracheids and vessels. During the day period cohesion force (attractive force between water molecules) and transpiration pull helps in the upward movement of sap from roots to leaves. The effect of root pressure in transport of water is more important at night. During the day when the stomata are open, the transpiration pull becomes the major driving force in the movement of water in xylem.
• Transpiration The loss of water in the form of water vapours from the aerial parts of a plant is known as transpiration. Transpiration mainly occurs through stomata (about 80% to 90%) but it may also occur through cuticle (9%) and lenticels (1%).

Functions of transpiration:

• It helps in absorption and upward movement of water.
• It helps in temperature regulation. The plants are protected from the burning due to transpiration. - Evaporation of water from leaves produces cooling effect.

Plants have low energy needs as compared to animals. Explain

Plants are anchored and do not move. Most of their body is made of dead cells and cell walls. Therefore, their requirements of energy are quite low as compared to animals.

Transportation of Food and Other Substances

Sugar, amino acid and other substances are translocated from site of synthesis to the site of storage through the phloem. The transport of food from leaves to different parts of plants is termed as translocation.

Translocation may be in an upward or downward direction depending on the need of the plant. Translocation of food takes place in the sieve tubes with the help of adjacent companion cells of phloem tissue.

• Phloem tissue consists of four components. (1) Sieve tubes (2) Companion cells (3) Phloem parenchyma (4) Phloem fibers
  
  Parts of the phloem tissue

Mechanism of translocation

Translocation takes place with energy consumption in the form of ATP. Sugar (sucrose) made in leaves are loaded into the sieve tubes of phloem by using energy from ATP.

It increases the osmotic pressure of the sieve tubes. Water now enters into sieve tubes containing sugar by the process of osmosis. Soluble material is then transferred from phloem tissue to other tissues which have less pressure than in the phloem.

Thus, according to plants requirement, the material is translocated from higher osmotic pressure to lower osmotic pressure areas. For example, in the spring, sugar stored in root or stem tissue would be transported to the buds which need energy to grow.

10.0Biology Diagrams made Easy

11.0Chapter At a Glance

12.0SOME BASIC TERMS

• Cluster : Group
• Specific : Exact
• Clenched : To close or hold tightly.
• Rupture : Bursting or breaking.
• Constriction : To become narrower.
• Efficient : Function in a best possible manner.
• Osmosis : Movement of a solvent (such as water) through a semipermeable membrane (as of a living cell) into a solution of higher solute concentration.
• Aerial : In the air.
• Fist : A hand with the fingers and thumb closed together tightly.
• Evaporation : Is the process in which a substance in a liquid state change to a gaseous state due to an increase in temperature and pressure.
• Condensation : Water which collects as droplets on a cold surface when humid air is in contact with it.
• Adjacent : Next to or touching.
• Metabolic activity : The sum of the chemical reaction that take place within each cell of a living organism and that provide energy.
• Steadily : In a regular and even manner.
• Suction : Is the force that a partial vacuum exerts upon a solid, liquid and gas.