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Tuesday, March 6, 2012

Structure And The Functions Of The Blood Circulatory System

The blood circulatory system has a special place as the main transport system of the body. There are 3 main characteristics common to all blood circulatory systems.
  • Activity of a circulating fluid or blood.
  • Activity of an organ to pressurize the liquid to flow.
  • Activity of vessels for the blood circulation.
The heart of man is shaped like a very young coconut and the size is just similar to your first and the circulatory system consists of arteries and veins. A closed blood circulatory system has the following features.
  • Blood flows inside the vessels.
  • Blood has no direct contact with the organs.
  • Heart pumps out the blood throughout the body and it comes back to the heart.
  • Blood is supplied to the organs, tissues as required by them.
  • Substances are exchanged through the walls of the blood vessels.
There are two types of blood vessels according to the structure and the functions they perform.
  1. The vessels that carry away blood from the heart are called Arteries  - except Pulmonary Arteries.
  2. The vessels that bring the blood back to the heart are called veins - except Pulmonary Veins 
Have you seen the veins raised up in hands and legs of some people? A vein is used to denote a type of blood vessel. Think of an instance when your pulse has been checked. You can find out the speed of the flow of blood in a vessel by testing your pulse. You can test your pulse at the following places. Inner side of the elbow, under the arm pit, on both sides of your neck, inner side of the ankle and the wrist.

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Wednesday, February 29, 2012

How Blood Helps for the Functions of the Human Body

If you have a cut, a wound or a bruise on your body, blood flows out of the wound. Blood flows within the body in blood vessels. Although blood appears to be a homogenous fluid as you take it out of the body it gets separated into two if you leave it in a test tube. The dark red gelatinous part and the yellow colored fluid are the two parts. A normal person has about 5.5 liters of blood in his body.

Components of Blood

You can see the components of it by preparing a slide of blood and looking through a microscope. You will see a large amount of cells floating in a fluid. Most of them are red in color. You may see other cells of different sizes and a very small type of bodies. Cover the smear of blood with a cover slip and add a small drop of dilute acetic acid. If you look at the slide now, you will find that the red cells are not seen, but some other cells are seen. These cells are white in color. Let us now discuss these various components in detail.

Red Blood Cells - Erythrocytes

The red cells seen in blood are called erythrocytes or red blood corpuscles. The red color of blood is due to these cells. These cells have bi-concave shape and move singly or in a group within the blood vessels. As a result the exchange of gases through their surfaces is more efficient. Red cells are large and they cannot pass through capillary tubes easily. As a result there is more time for the exchange of gases.

The red color of erythrocytes comes from hemoglobin. This is made from a pigment named haematin which has iron and a protein named globin. The life time of an erythrocyte is about 3 months. These are broken down in the liver and the spleen. The proteins and the iron in hemoglobin is absorbed then. Erythrocytes are formed in the bone marrow.

White Blood Cells - Leukocytes

These are larger than erythrocytes but less in number. The number of leukocytes is just about one per 600 erythrocytes. The white blood cells are known as leukocytes have a nucleus and are colorless. There are about 4000 - 11000 white blood cells in 1ml of human blood. The white blood cells are divided into two categories depending on the availability of granules in the cytoplasm. Lymphocytes are round in shape and the nucleus is so large that it almost fills up the entire cell. These are also produced in the bone marrow.

Platelets

In addition to the above cells, there is another type of cells. These cells are very small and have no nuclei. They have granules and are known as platelets. Platelets too are produced within the bone marrow. All blood cells are inside a yellow fluid. This fluid is known as blood plasma. The blood plasma is about 55% of the blood. 92% of the plasma is water. A lot of substances necessary for the body are in the plasma.

Functions of Erythrocytes

Oxygen combines with the hemoglobin in the red cells and forms oxy-hemoglobin. Blood  turns bright red as a result. When blood goes to the cells through the blood vessels, the oxy-hemoglobin breaks up and releases oxygen. This oxygen diffuses into the cell.

Functions of Leukocytes

Some leukocytes show amoeboid movements and engulf bacteria and virus that enter the body. This is know as Phagocytosis. Some leukocytes produce antibodies against disease causing bacteria.

Functions of Platelets

Blood flows out of a wound if you injure yourself. Continuous flow of blood is prevented by blood clotting on the wound. A number of substances take part in this process. This action is made quicker by platelets.

Functions of Blood Plasma

The fluid nature of blood is due to the plasma. It also transport all substances throughout the body. Blood plasma transports blood cells, hormones, nutrients and the excretory substances throughout the body. Another important function of blood is the regulation of body temperature.

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Tuesday, February 28, 2012

How Transpiration Influences the Survival of the Plants

In the end of my previous post I brought a word called transpiration, But I didn't explained it. So this post will do that task.

You have the experience that a wilted plant revitalizes if water is supplied to it. You can assume that main reason for the wilting of plants is the non-availability of water. Why do plants face a dearth of water?

You can use this method to test how water goes away from a plant. Select a plant and cover a twig with polythene bag around it. Then keep it for some time. Now take it away and put some anhydrous copper sulphate into the polythene bag.

There are droplets of a liquid formed on the inner walls of the polythene bag. These droplets turn anhydrous copper sulphate blue, indicating that the droplets  are water. Hence, you can conclude that plants give out water. You cannot see the water coming out. In which case water should have come out in the form of vapor. This vapor has condensed and got deposited on the inner walls of the bag.

Loss of water from a plant in the form of vapor is known as Transpiration. The main way in which transpiration takes place is through the stomata. Hence this is called stomatal transpiration. If transpiration takes place through the cuticle of the leaf or any other part of the plant it is known as cuticular transpiration. Transpiration can occur through the air pores available in the roots and the stem of the plant. This is known as airpore transpiration.

The amount of water that goes out of the plant in the form of vapor is very large. This water has not taken part in any metabolic process. This quantity amounts to 95% of the total amount of water taken in by the plant.

Factors Affecting Transpiration

As transpiration is the process of water going out in the form of vapor, the factors that given evaporation affects transpiration too. Environmental factors that affect the evaporation of water are:
  • Environmental temperature.
  • Humidity of the atmosphere.
  • Speed of wind.
  • Intensity of light.
  • Atmospheric pressure.
These factors affect transpiration too. In addition the supply of soil, water too has an affect. To test the effect of these factors on transpiration, You should be able to measure the rate of transpiration. A potometer is used to measure the rate of transpiration in the laboratory.

The twig used in the potometer should be cut and fitted inside the water. This is done in order to prevent any air particles entering the twig. The twig should cut using a sharp knife. A small air bubble should be allowed to enter the capillary tube.

When water evaporates through the leaves, the bubble of air moves towards the twig. A the capillary tube is graduated, the distance moved by the air bubble can be measured. You can use this apparatus to measure the rate of transpiration of a plant under different environmental situations.

Effects of the environmental temperature

The rate of evaporation of water increases with temperature. The amount of water vapor that can remain in the atmosphere too increases with temperature. Therefore more water can go out of the leaves with the increase of temperature.

Relative humidity of air

The decrease in humidity of the atmosphere means decrease of the water vapor in the atmosphere. Water molecules can enter the atmosphere easily as a result. The diffusion rate of water from the leaf to the atmosphere decreases with the increase of the percentage of water in the atmosphere.

The effect of the wind speed

The water particles around the leaf will get blown away when there is wind. As a result more and more water particles can join the atmosphere. The rate of diffusion of water increases with the speed of the wind. Hence the rate of transpiration increases when the speed of wind increases.

Effects of the atmospheric pressure

The evaporation rate of a liquid increases in a vacuum. Th rate of evaporation decreases with the increase in pressure. Hence the rate of transpiration increases with the decrease of atmospheric pressure.

The Adaptations in Plants to Reduce the Rate of Transpiration


Plants absorb water from the soil when water leaves the plant by transpiration. But the plants on land will not get enough water. The xerophytes face the lack of water severely. Hence the plants show adaptations to reduce transpiration.

1.) Dropping of leaves, leaves turning into thorns and having fleshy stems.

A very small number of leaves appear in certain plants like cactus and euphorbia. These leaves also drop off when young. Some of the leaves and auxiliary buds modify into thorns. The transpiration reduces as there are no leaves. In addition the stem is fleshy and a milky white thick liquid is formed. This liquid keeps behind the water. The leaves of aloe are fleshy.

2.) Sunken stomata.

The stomata in plants like cycas and oleander are at a lower level than the cells of the epidermis. As they are sunk, the sotmata do not make a direct contact with the atmospheric air. Hence, the effect of the environmental factors is less and the transpiration is less.

3.) Bristles on the leaf surface.

There are hair like bristles on the surface of some leaves. These are formed by the cells of the epidermis. There is a wet, air strata between these bristles. Hence the loss of water is less and transpiration is less. eg: Pumpkin, Nettle

4.) Formation of a thick cuticle.

The cuticle of some leaves is very thick. As it has a wax on the surface of the leaf blade, the blade is shiny. Transpiration reduces as a result. eg: margosa, plumeria

5.) Rolling of leaves.

The leaves of certain grass types roll in and close down the stomata when there is a dry climate. As there are more stomata on the upper surface, these get closed down due to the rolling. Therefore transpiration reduces.

6.) Deciduousness (Dropping of leaves during certain times of the year)

The leaves of certain trees drop during the dry season. The transpiration reduces as there are no leaves. eg: rubber, terminelia

The effect of transpiration on plants

The following advantages are gained by plants due to transpiration.
  1. Certain substances are conducted to upper regions of the plant.
  2. The damage caused to plant leaves is reduced because of evaporation.
  3. Water is distributed within the plant body.
  4. The osmotic pressure inside the cells is maintained as a large amount of water is absorbed.
  5. More water enters to the plant.
  6. Plant is cooled.

Guttation

On certain days in the morning even though there is no rain, you can see small droplets of water at the tips of leaf blades such as grass, alocasia and paddy. This water has come out of the plant leaves.

There are some holes known as hydathodes at the tip of the small veins. The water pushed up by root pressure comes out of these holes. This is called as guttation. It has been found out that the function of hydathodes is only guttation. As root pressure cannot push water to a great height guttation occurs in plants that grow short. Guttation occurs in alocasia, amorph phallus and grass.

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Monday, February 27, 2012

Transportation System for the Continuation of Living Organisms Part II

This post is the part two of previous post. in the previous post I wrote about Dormant Transportation or passive transportation. This post is about Active Transportation.

Active Transportation

You know that diffusion is due to a concentration gradient. Water enters living cells against to the concentration gradient too at certain times. Look at an example. There are more sodium ions than iodine ions in sea water. In certain marine plants there are less sodium ions than iodine ions. Sodium ions do not enter the plant though iodine ions enter. The number of potassium ions in the cells of the fresh water plant nitella is thousand times greater than the number of ions in the surrounding water. If the potassium ions enter the cell by diffusion from the surrounding medium, it can occur only till the concentrations of potassium ions inside and outside are equal. (For the ions of a lesser concentration to enter the cells, ions should move from a region with a higher concentration.) Therefore the sodium or iodine ions enter the cells against the diffusion process.

The passage of particles of matter through a plasma membrane into a cell or out of cell against the natural diffusion process is known as Active Transportation. Energy of metabolism is used up for this purpose.

This process occurs through carrier molecules. Carrier molecules are a type of molecules in the plasma. The mineral ions which are attached to these molecules enter the cytoplasm. Hence the plants have the ability of absorbing the required minerals only.

The water and the minerals absorbed by the root hairs are conducted to the various parts of the plant through the xylem cells in the roots and the stem. This occurs by the movement of substances from cell to cell by osmosis and active transportation.

The structure of a tender root

There are two types of plants. They are the dicotyledonous and the monocotyledonous. You can see some structural differences between them. The external layer called the epidermis is a layer of single cells. Some of these cells have protrusions coming out. These are known as root hairs. The cortex, which consists of circular cells is the inner layer next to the epidermis. There are inter cellular spaces between these two layers. There is a single layer of barrel-shaped cells next to the cortex and it is known as the endodermis. These cells are arranged close together. There are no intercellular spaces between them. Next to the endodermis, the pericycle is made out of a single layer of cells. The vascular system is underneath this layer. The xylem layer is in the form of a star and the phloem cells are in between the xylem layers. The cambium is in between the xylem and the phloem. The pith is in the center. This is a very small layer. The structure changes when the dicotyledonous plants undergo secondary thickening as they mature. The roots thicken with age.

The structure of tender root of a monocotyledonous plant too is similar to the root of a dicotyledonous plant. But there is no cambium and no secondary thickening. Hence roots do not thicken with age.

Adaptation of roots for the absorption of water and minerals

  • The roots of dicotyledonous plants are divided into many lateral roots.
  • The monocotyledonous plants have a large number of fibrous roots.
  • Presence of root hairs.
  • Presence of a fairly thin epidermis at the tip of the root.

Ascent of sap

    A column of water rises up from the roots of a plant to the leaves through the xylem vessels. This is a continuous column of water. There are no air bubbles inside this air column of water. Xylem vessels are similar to pipes. There are two reasons for continuity of this column of water.
    • The water particles are attracted to each other - Cohesion.
    • The water particles are tightly attached to the walls of the xylem vessels - Adhesion. 
    When water goes out from the leaves of a plant by transpiration, water flows up along the xylem vessels under the conditions. The flow of water from the roots to the leaves due to transpiration is known as transpiration pull.

    In the soil the minerals are dissolved in water as their salts. The roots absorb this water and the root system of a plant exerts a push on it and sends it up along the xylem tube. This push is known as the root pressure. It has been found out that the maximum height of water that can be pushed due to the root pressure is about 18m. The water rises up beyond this height only due to the transpiration pull. The process of transporting water and minerals dissolved in it through the xylem cells from roots up to the leaves is known as the transpiration of nutrients.

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    Wednesday, February 22, 2012

    Transportation System for the Continuation of Living Organisms Part I

    The water and minerals absorbed by the roots should be transported to all the cells of the plant. Transportation in plants occurs in two ways

    Dormant Transportation

    The transportation that occurs without spending metabolism energy called dormant transportation. This occurs by
    • Mass flow
    • Diffusion
    • Osmosis
    • Evaporation

    Mass Flow

    When water and minerals are able to flow due to the difference of pressure at two points. water flows along xylem conducting tissue and through the cell wall in this manner. The cell wall is made up of tiny fibers. There are small spaces in between these fibers. Water flows along these spaces by this process. The dissolved salts in water are also carried with it.

    Diffusion

    When nyctanthes flowers bloom at night and when a joss stick is lit or a bottle of perfume is opened in a small room you get the pleasant smell spread all over the room. The smell spreads in particles. Matter is made up of particles and these particles continuously vibrate. When the particles are clustered together, each particle is surrounded by other particles, and they tend to get released from the other particles around. The process of spreading particles from a place with a higher particle concentration to a place with lower particle concentration is known as Diffusion. The particles of perfume spread into the air particles. The air particles as well as perfume particles are both vibrating. The gases can spread through liquid particles, solid particles and through gas particles.

    As a example take a small bottle which filled with some color and release it under a water bath. Then the color spreads to the water outside from the small bottle. This is due to diffusion of the color particles in the water. After some time - a longer time the color of the water in the vessel and the small bottle will be the same. The concentration of the particles of the colored solution in the bottle decreases while the concentration of particles in the vessel of water increases. At one stage the spreading of particles inside the water is even. Then you can say that the system is balanced. When water enters a plant, diffusion takes place.

    Osmosis

    Osmosis is a process of diffusion taking place through tissues. If a certain substance can pass through a tissue, you can call it a permeable tissue for that substance. Some tissues are permeable to certain substances and non-permeable to others. Such tissues are known as selectively permeable membranes. The process of water flowing from a place with a lesser concentration to a place with high particle concentration through selectively permeable membrane - Permeable only to water is known as Osmosis.

    Root Hairs

    A special structure formed by a cell on the epidermis of the absorbing region of the root is called root hairs. Root hairs are inside the soil. The concentration of the cell liquid of the root hair is higher than the concentration of the water outside. Hence water diffuses into the root hairs. Then the water particles move into the xylem cells through the other cells in contact and move through the entire plant. Some particles can enter through the plasma membrane. Some mineral particles too enter through the root hairs.

    Evaporation

    Water boils at its boiling point. Then water particles enter the vapor state from the liquid state. Water can get evaporated without reaching its boiling point. But the rate of evaporation is less than the evaporation at its boiling point. The entering of water particles into the vapor state from the liquid state without reaching its boiling point is known as evaporation. A cloth hanging on a clothes line or a wet floor dries up due to evaporation. The water passing to the central cells of the leaf along the xylem cells of the leaf veins enter the intercellular spaces by evaporation.

    I'll meet you up in the next post about Active Transportation which is part II of this post.
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    Tuesday, February 21, 2012

    The Factors Needed for the Process of Photosynthesis

    Now I think you what are the products and byproducts of photosynthesis process. Now I'm going to let you now some tests that will lead you to find what are the factors needed for this photosynthesis. Firstly these are the factors needed for the process.
    1. Carbon Dioxide.
    2. Sunlight.
    3. Water.
    4. Chlorophyll. 

    Carbon Dioxide test for Photosynthesis


    Carbon dioxide is absorbed by potassium hydroxide. Take two similar, transparent polythene bags and put some potassium hydroxide pellets into one bag. Insert some leaves of a potted plant which has kept in the dark for two days into this bag and tie the mouth well. Insert some leaves into the other bag and tie the mouth of this bag too. Allow them to receive sunlight for some time and then test these for starch. I'll tell you late how to test for the starch.

    *There is no starch produced in the leaves in the bag containing potassium hydroxide.
    *Starch is available in the leaves of the bag without potassium hydroxide.
    *This shows that carbon dioxide is necessary for photosynthesis.

    Light Energy test for Photosynthesis


    Select a leaf from a potted plant kept in the dark for two days. Cover the leaf with two pieces of black paper on either side. Allow the plant to get sunlight for a few hours. Test the leaf for starch.

    You will notice that the covered part of the leaves will not turn blue. But the uncovered leaves turn blue. this experiment shows you that sunlight is necessary for photosynthesis.

    **If you want to show that water is necessary for photosynthesis you should have green leaves without water. If you remove water from leaves they will die. Therefore you can't design an experiment to show that water is necessary for photosynthesis.

    Chlorophyll test for Photosynthesis


    Select a leaf that does not contain chlorophyll for this experiment. Multicolour leaves like hibiscus, colacasia or choleas may be used. Let the leaf remain in sunlight for a few hours and pick it up. Draw a diagram of the leaf and mark the shite spots that do not contain chlorophyll. Next test the leaf for starch and compare it with the diagram drawn. you will see that the portions which were green in color have turned into blue. This shows that chlorophyll is necessary for photosynthesis.

    Ok this is the time for starch test!

    First you should remove chlorophyll of the leaf by dipping the leaves in alcohol heat bath. Then put some iodine to chlorophyll removed leaf. That's it!

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    Monday, February 20, 2012

    The Most Wanted Process of Photosynthesis

    You know that photosynthesis is a process that must happen. Because If it loose it's process, our world won't be like this. So You also need to contribute to maintain that Most Wanted process. Most people don't know about this and they put all of us in risks by making down this photosynthesis.

    Concept of Photosynthesis


    Scientists believe that the earth was formed about 4.5 billion years ago and that it had a high temperature and and an atmosphere which had simple molecules such as hydrogen, nitrogen, carbon dioxide and water. As the atmosphere cooled gradually the water vapour condensed and formed the oceans. Scientists believe that amino acid and other simple molecules dissolved in this water to form the"Primitive Soup" and life originated as chemosynthetic organisms inside this primitive soup. The chemosynthetic organisms use the energy released by the oxidation of iron to produce food in the form shown below.

                        energy
    C02 + H20 -----------> Simple Sugars.

    As time passed by, after another 12 million years the evolution of a complex molecule named chlorophyll took place. This molecule had the ability of obtaining energy from sunlight. hence the process,

                                Sunlight
    6CO2 + 6H2O + ------------------> C6H12O6 + 6O2
                                Chlorophyll

    Started. This action, which involves light energy is known as photosynthesis.

    Importance of Photosynthesis


    The chemosynthetic bacteria which lived for over the last 27 million years exist as unicellular organisms even today. The unicellular photosynthetic organisms evolved to be multicellular and could change into trees on land and marine plants which are hundreds of metres long. This shows the importance and the environmental suitability of photosynthesis. In addition to the food production, oxygen is released as a byproduct. This created an environment for the living organisms to have an efficient aerobic respiration. The oxygen that rose to the higher levels changed to ozone and formed a layer which protects the earth from destructive sun's rays such as ultra-violet rays. As carbon dioxide which is considered to be a green house gas is needed as raw material in photosynthesis. The atmosphere provides a friendly environment for life.

    The first stage of any food chain is a green plant which is the producer. The green plants are producers because of chlorophyll. There will be no living organisms on earth if not for this process. Now you may realize that the origin of man - Who has developed the ability to control the environment is also due to photosynthesis.

    Products of Photosynthesis


    Carbon dioxide and water react in the presence of sunlight to produce a simple sugar named glucose while giving out oxygen as the byproduct. This process is know as photosynthesis.

                                                    Sunlight
    Carbon Dioxide + Water +  ----------------> Glucose + Oxygen
                                                    Chlorophyll

                                 Sunlight
    6CO2 + 6H20 + ---------------> C6H12O6 + 6O2
                                 Chlorophyll


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    Sunday, February 19, 2012

    The Organizing Pattern of the Bodies of Living Organisms

    Every living cell performs a number of activities in it. Exchanging the materials efficiently through the surfaces is an inevitable activity. When a cell increases quantitatively the increased area is less than the amount of volume increased. Exchanging material through the surface of large cells are not sufficient to pursue the vital activities efficiently. Therefore when the growth comes up to a limit the cell divides. The multicellulars originate like this. Now you have already learn that cell division forms the tissues and tissues organize to form the body of multicellular organisms.

    The systems in plants occur by uniting a few tissues. The examples are the system of xylem tissues and the system of phloem tissues. But in animals, the tissues unite and are organized as functional units. These functional units are identified as systems. The examples could be given as skin, eye, tongue, stomach for the systems in the body.

    The life is the organization of vital activities performed by the organisms. There are systems formed by uniting a number of organs to perform special activities in the bodies of organisms. The digestive system and the respiratory system are the example for this. An organism forms by uniting many systems.

    The Necessity of Systems for the Activities of the Body

    The organisms grow for their existence. They reproduce for the existence of their kind. They respire to earn the necessary energy to perform all the vital activities including growth and reproduction. The raw materials are supplied by nutrients. The excretory substances are produced while doing the activities. The organisms excrete some substances and for that they have the excretory systems. To do most of these activities organisms should move and respond stimuli. There is a struggle for existence among the organisms for a successful life.

    The organisms succeed when they perform these vital activities efficiently and suitably to the environment. When an organism increase in size and complexity, the intake amount of material increases. So is the amount of material it excretes. Although the diffusion is an efficient method of exchanging materials in the unicellular organisms, it is not efficient for multicellulars. The flowing of particles from one place to another in the body along with a pressure difference is know as the Mass Flow.  It is an efficient method of exchanging materials in multicellular organisms. The mass flow occurs in the blood circulatory, respiratory and excretory systems. Through systems, the organisms perform their vital activities efficiently and survive successfully in the environment.

    Summary
    • Systems pursue a diligent work to perform the vital activities efficiently in higher multicellular organisms.
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    Saturday, February 18, 2012

    Exploration of Structure and Functions of the Animal Tissues

    I said I'll talk about Animal tissues in my previous post. As I said then here's the Animal tissue post with much details.

    Introduction

    The cells of muticellular animals are organized as tissues. Blood is a liquid tissue. 40% of the weight of an animal is muscle tissue. It is composed of specialized cells having the ability of contraction. The covering layer of all the external and internal surface of an organism is called the epithelial tissue. These are arranged in single or mutilayered sheets. Single layered tissues are called simple epithelium and the multilayered tissues are called compound epithelium. The nerve tissues are made by nerve cells or nerves. These cells are specially adapted to carry the nervous impulses.

    Blood Tissues

    The blood tissues consist of a few types of cells and it is in a packing tissue called plasma. The cells in the blood are red and white cells. Plasma is a pale straw-colored liquid. It consist of 90% of water and 10% of the various substances as suspension. The water is important in the plasma to translocate the substances all over the body. These substances are globulin, prothombin, fibrinogen, plasma protein and mineral salts. Prothombin is an important material in blood clotting.

    The red cells give red color to blood. There are 5million - 5,000,000 red cells in 1mm3.One drop of blood has a volume of 50mm3.Having such a big amount shows the value of red cells. Obtaining oxygen from the lungs and carrying them to the tissues is done by the red blood cells. A red color pigment called haemoglobin is dissolved in the plasma and it gives red color. The lack of nucleus makes more room for haemoglobin in these cells. Red blood cells are originated from bone marrow and destroyed in the spleen. There are five types if white blood cells in structure and function. But the main two types are granulocytes and agranulocytes.

    Platelets are the third constituent of blood which covered by membranes. They are fragments of cells and lack of nuclei. They help in the process of blood clotting. There are about 250,000 of platelets in 1mm3 of human blood. It is originated in the bone marrowand destroyed in the spleen as red blood cells.

    Blood Constituent Function
    1.)Granulocytes
    1. Nutrophils
    2. Eosinophils
    3. Basophils
    Engulf germs and bacteria. Allergic responses.
    1. Produce heparine(Anti-Clotting protein)
    2. Produce hisstamine(Chemical stimulates the repair of damaged tissues)
    2.)Agranulocytes
    1. Monocytes
    2. Lymphocytes
    Engulf bacteria production of antibodies.

    Muscle Tissue

    Three distinct types of muscles can be identified. Muscle tissues have the ability of contraction. The movements of one part of the body could be done relatively to the other parts with the muscles.

    Striated Muscles

    These muscles are identified as voluntary muscles or skeletal muscles. The dark miofibril bands and light miofibril bands are seen with the naked eye in the cell plasma. The muscles attached to the skeleton are therefore called skeletal muscles. The movements of these muscles can be done voluntarily. They are called voluntary muscles. The muscle made up of muscle fibers. The bundles of muscle fibers are connected by perimysium fibers and surrounded by epimysium connective tissues. Once the stimulus understood the contraction occurs rapidly and fatigue quickly.

    Unstriated Muscles

    These muscles are identified as smooth muscles or unvoluntary muscles. It is introduced as unstriated as there is no strips. The muscles have elongated cells and a nucleus. Nucleus is surrounded by a small sarcoplasm. The rest of the cell is made up of flexible fibers. The fibers run along the cells and connect lightly. The wall of the organs like intestine and bladder are made up of unstriated muscles. These muscles help to pass the material through the systems. it is slowly contracted and slowly fatigued. It shows longitudinal contraction.

    Cardiac Muscles

    The heart is composed of cardiac muscles. The muscles have important properties as the other two types of muscles. They are not separated as uninucleus cells. Around the fibers there is a sarcolemma and cross striations. The fibers are not long as the skeletal muscles but the strips can be seen. The dark bands known as intercalated discs are situated individually. Cardiac muscles can contract and even be removed from the body and do not fatigue easily.

    Epithelial Tissues

    Simple Epithelium Tissues of Animals
    Simple Epithelium Tissues of Animals
    Epithelial tissues cover the internal and external surfaces of the body of an organism. The bottom layer of cells rest on a basement membrane composed of a collagen fiber network. The basement membrane is thin and soft. Epithelial cells are not supplied with blood. There are five types of epithelial tissues.

    Simple Epithelium

    Squamous Epithelium

    Squamous epithelium occurs in areas such as renal capsules of the kidney, the alveoli of lungs and the blood capillary walls. The thickness of the tissue permits the diffusion of materials through it.

    Cuboidal Epithelium

    It forms a lining of many ducts such as salivary, thyroid, sweat and urinary collecting ducts of the kidney. The spherical nucleus is in the center of the cell. It performs the functions of secretory  glands.

    Columnar Epithelium

    These cells are tall and quite narrow. Each cell possesses a nucleus situated in various places. These cells are lined from the stomach to rectum. It performs the absorptive and secretory functions.

    Ciliated Epithelium

    Cells of these tissues bear numerous cilia at their free surfaces and always cilia show a movement. Ciliated epithelium lies inside the respiratory passages like nostrils, trachea and tracheoles. Cilia can trap the particles while passing through it.

    Pseudostratified Epithelium

    This layer of cells is attached to the basement membrane. But not all the cells reach the free surface. This epithelium is found lining in urinary track, trachea and trachedes.

    Compound Epithelium

    Stratified Epithelium

    This tissue is made up of a number of cell layers and it is thick, rough and can resist the friction. The innermost cell layer is identified as germinal layer. The outer layer is transformed into a dead layer and flakes away. These cell layers are found in external skin surfaces, esophagus and buccal cavity.

    Transitional Epithelium

    All cells in this epithelium are able to modify their shape as they can be stretched and elongated. It consists of 3-4 of males and the urinary bladder
    Summary

    • A tissue can be defined as a group of cells specialized for a particular function or functions.
    • There is a number of different types of tissues according to the structure and function in plant and animal bodies.
    • The tissues do an innumerable service in labor division in the muticellular organisms. 
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    Tuesday, February 14, 2012

    The Huge Exploration of Tissues of Plants According to the Structure and Functions

    After very long time I'm again going to keep SmartSciencePro active. I was busy wit my life. Ok then here I'm going to the post.

    Introduction

    Now you know about the organization of organelles in a cell. The organelles in the cell vary according to the functions they accomplish. the cells of similar structure compact together, can be seen in multicellular organisms to accomplish a particular function. A group of cells showing similarities in growth and origin, and adapted to fulfill very special matters, is known as a tissue. There are a number of various tissues in muticellular organisms for division of labour and their structures are adapted according to the functions.

    Plant Tissues

    There are two types of tissues.
    1. Meristematic Tissues.
    2. Permanent Tissues.
    Meristematic tissues are composed of cells with the ability of dividing. It's present in the apex of the stems and the roots. Later these tissues modify into permanent tissues.

    There are two types of permanent tissues.

    1. Simple Permanent Tissues.
    • Parenchyma.
    • Collenchyma.
    • Sclerenchyma.
    2. Complex Permanent Tissues.
    • Xylem.
    • Phloem

    1. Parenchyma Tissue

    These are living cells elongated or spherical in shape. The cell wall is made up of cellulose, hemicellulose and  pectin. Intercellular air spaces are present within the tissues. These cells act as a packing tissue like in the central pith and outer cortex of young stem and roots. The osmotic properties of parenchyma cells are important, when turgid they become tightly packed and provide support. These tissues are seen in stem tuber of potato as food storage tissues. Specialized parenchymatous tissues are epidermal cells, guard cells, parenchyma in the leaf blade, endodermic cells, pericycle and companion cells.

    2. Collenchymatous Tissue

    Collenchymatous tissues are composed of living cells of polygonal in shape. The corners of the cell walls are thickened with cellulose. Therefore these cells are modified to supply the mechanical energy and give support.

    3. Sclerenchymatous Tissue

    Sclerenchymatous tissues have elongated cells with thickened cell walls by lignin. These tissues provide support and strength for the plant because they are heavily thickened with deposits of lignin. Some areas where lignin is not deposited are called simple pits, The neighbouring cells are interconnected through these minute pits. These cells are arranged as sheets to make tissues. The fibers are found in the shells of coconut and in the stem, some fibers are formed into solid rods. All are formed by sclerenchyma cells.

    There are some other types of sclerenchyma cells called stone cells which are thickened by lignin. In the flesh of a pear fruit, they occur in small groups and are responsible for the'grittiness' of these fruits.
    Sectional Views of Simple Plant Tissues
    Sectional Views of Simple Plant Tissues

    4. Xylem Tissue

    The major function of the xylem tissue is the conduction of water and mineral salts. It consists of four cell types, namely tracheids, vessel elements, parenchyma and sclerenchyma.

    Tracheids and Vessels

    Trachieds are single cells that are elongated and lignified. Structures called simple pits appear in the walls where lignin is not thickened. Water passes to tracheid through the pits membranes continuously. The walls of tracheids are lignified as annular or spiral. The cells of vessels are long and cylindrical. The cell walls are lignified as annular, spiral, scalariform or reticulate. Water can pass through vessels with minimal obstruction as cross walls are absent. The length of a vessel may be a few centimeters, some time it may be a few meters. The walls of the cell have high tensile strength which is another important feature.

    Xylem Parenchyma and Xylem Sclerenchyma

    These cells are similar to parenchyma an sclerenchyma and situated mixed with tracheid and vessels. Xylem fibers provide extra energy to the xylem. They form a radial sheet of tissue called medullary ray which maintains a living link through the wood between the pith and the cortex.

    5. Phloem Tissue

    There arr five cell types in the phloem namely, sieve tubes, companion cells, parenchyma, fibers and sclereidons. Sieve tubes are long, tube like structures that translocate the solutions of food throughout the plant,

    They are formed by end to end fusion of sieve tube elements. The sieve cells have no nuclei and the cytoplasm becomes confined to this layer around periphery of the cell. The sieve tube cell with the adjacent companion cells from a functional unit. The two adjoining sieve tube cells form a sieve plate. The phloem parenchyma cells which form the medullary rays are similar to xylem parenchyma Phloem fibers and stone cells help to maintain the strength.

    I think the post is very long, but the information is much. In the next article I'll bring you about Animal Tissues with a great coverage.How about this one? Great! Awesome! Or Nice Then just share with your friends and Comment your Idea Below. Appreciate it!

    Sunday, February 5, 2012

    Immunity Which Fight With Disease Causing Viruses And Bacteria

    The mechanism which prevents the entry of micro-organisms to the body and prevents them getting settled in the body is Immunity.  The body has the ability reducing the invasion and the strength of the micro-organisms. As a result you do not get diseases. This ability of the body is called Immunity. There are two forms of immunity. They are Specific Immunity and Non-Specific Immunity.

    Specific Immunity

    A definite protein in blood causes the production of antibodies which provide immunity against the different molecules in micro-organisms. This is specific for certain diseases.
    Example: Chicken Pox, Mumps, Measles

    The immunity caused may end up after some time or may last till death. This immunity is caused within the body in 2 manners.
    • The immunity caused by contracting the disease once.
    • Causing immunity by artificial methods. The triple injection given to infants at birth is an example.
    The infant receives some antibodies from the mother during the pregnancy. The breast milk of a mother has cholestrum. This is an substance which gives antibodies to infants. This too is a specific immunity.

    Non-Specific Immunity

    This is the natural mechanism of protection. This immunity is caused by several means.
    • Skin and the mucous membrane.
    • Antibiotics in the body fluid.
    • Phagocytosis.
    • Responses to inflammations.
    The outer layer of the skin prevents the entry of micro-organisms into the skin. The sweat, sebaceous gland secretions and anti-micro-organic substances prevent the growth of disease causing micro-organisms.

    The mucous membrane in the respiratory system secretes mucous. The micro-organisms entering the respiratory system stick to the mucous and is sent to the stomach. They get destroyed by the hydrochloric acid in the stomach.

    The lysome bacteria in sputum and tears break down the walls of the bacteria. Iron helps in the growth of disease causing bacteria. Some chemicals in the body react with iron and limit the growth of such bacteria.

    A chemical named lactosheryne is available in tears, breast milk and bile. If micro-organisms enter the blood stream, various cells in the blood system and the lymphatic system destroy them by phagocytosis.

    Coagulation of Blood

    Some of the substances connected with coagulation blood are calcium ions, fibrinogen and thromboplastine and prothombine which is an anti-enzyme. These are available in the blood plasma. A gelatinous fiber is produced by the chemicals in them. When blood cells go in between them the blood coagulates. Platelets increase the coagulation process. Vitamin K also helps the coagulation of blood in addition to the platelets.

    Blood Groups and Blood Transfusion

    Austrian doctors, Carl and Landsteiner in 1901 found out that there are 4 blood groups which they named as A,B, AB and O. They are formed by special proteins and antibody generators. you have heard of blood donation and the blood bank. For whom do you donate blood?

    Blood constituents can be supplied artificially to a person after detecting his deficiency. This process is called blood transfusion. The national blood bank performs this function. the blood from a donor is centrifuged and separated into erythrocytes, leukocytes, platelets and plasma. These are stored under appropriate temperatures until they are made use of.

    There are 2 important factors to be considered in blood transfusion.
    • The compatibility of the blood groups of the donor and the recipient.
    • The donor's blood to be free of disease causing organisms.
    A Donor Should :
    1. Be within the age group of 18-60 years.
    2. Have a mass exceeding 50kg.
    3. Be free from HIV.
    4. Be free from sexually transmitted diseases.
    5. Not have been subjected to diseases such as hepatitis, typhoid, measles, chickenpox. 
    Some patients have died on transfusion even after being transfused the correct blood group. After conducting tests on these transfusions, some special proteins available in erythrocytes have been identified. This is named the Rh factor. Rh factor is present in some people in which care he will be Rh+ - Positive. There are 8 blood groups accordingly.

    A+                         A-
    B+                         B-
    AB+                      AB-
    O+                        O-

    It is good for a person to know his blood group.!

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    Sunday, January 1, 2012

    Great Features of Little Organelles in the Cell

    Today is the first day of 2012. So I thought to write about a short post. It's about organelles.

    Organelles

    The various structures adapted for doing various purposes in a cell are known as organelles. Let me tell you more details about organelles and their features. Here we go..!

    There are number of organelles in the cell. I'm going to explain one by one. so the first one is nucleus.

    Nucleus

    Organelles of a Cell
    Organelles of a Cell
    Nucleus is the structure which controls all the activities of the cell. The largest organelle in the cell is the nucleus. Nucleus is covered within two membranes. Inside the nucleus there is a nucleolus and chromatin fiber. Chromatin fiber is responsible for carrying hereditary characteristics.

    Chloroplast

    Chloroplasts are present only in plant cells. The grana present in chloroplasts contain pigment called chlorophyll. In addition there is some other pigment called carotene and santhophyll. DNA and starch grains are present in chloroplast. It is the organelle in which photosynthesis takes place producing food using light energy trapped by chlorophyll.

    Mitochondria

    It is covered by two membranes, the inner being folded to form cristae to increase the surface are. The reactions occur in mitochondria supply energy for all the activities in the cell.

    Golgi Bodies

    It is present in every nucleate cell. It is a flattened, membrane -Bounded sac. It is formed at one end of the stack, endoplasmic reticulum and budded off as vesicles at the other end. This is an internal process and a transport system, the Golgi vesicles transport the materials to other parts of the cell. For example, the Golgi bodies of the cells in pancreas produce trypginogen enzyme by allowing to react the protein with carbohydrates.

    Endoplasmic Reticulum

    It is present in every nucleate cell. It is tubular structure bounded by two membranes. It is bounded with outer membrane of the nuclear envelope. The ribosomes are found on the outer membrane. R.N.A on the endoplasmic reticulum is important in the synthesis of protein. It also helps to transport nuclear material from cell to cell.

    See you soon with another long post about Plant Tissues. Very long one and very explained one. And of course there is a post about Animal Tissues too. That's the biggest one. Wait for it!

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