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Tissues and Supporting Systems

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All arthropods have a segmented body enclosed in a tough, jointed exoskeleton made of chitin which gives structural rigidity to the body and points of muscle attachment.

Cartilages consist of cells embedded in a hard organic matrix known as chondrin. The embedded cells are the chondroblasts. Complex cartilages, like those of intervertebral discs and pinna of the car, have their matrix strengthened with connective tissue fibers.

Bone is much harder than the cartilage in that its organic matrix is impregnated with calcium salts of mainly calcium phosphate. The organic matrix of bone is secreted by osteoblasts which arrange themselves in concentric rings around nerves and blood vessels, giving rise to what is known as the Haversian system. This arrangement shown in lamlad biology pdf gives compactness to the bone (i.c. compact bone) and is found in the shafts of long bones (humerus, femur, tibia and fibula, ulna, and radius), while spongy bone, which is less compact and harder than the Haversian bone is found at the ends (epiphyses) of such bones.

Types of supporting Systems

Hydrostatic skeleton

This is found in soft-bodied invertebrates like sea anemones and earthworms. This is not a skeleton in the classical sense, but its place is taken over by a fluid under pressure. This Guide functions as a hydrostatic skeleton, being surrounded by muscles that act against it; in the earthworm, circular and longitudinal muscles in the body wall contract against the coelomic fluid in the body cavity.


This is the hard cuticle found in arthropods (insects, lobsters, etc.), and here it performs the function of a skeleton which, as it lies outside the muscles, is called an exoskeleton. The exoskeleton, which is tough and jointed, is made of chitin. Growth or increase in size in such animals is by periodical shedding of the exoskeleton by the process of ecdysis or molting.


This is so-called because the skeletal elements, bones or cartilage, are internal to the muscles which are attached to them. Examples are found in all vertebrate animals. Endoskeletal animals grow by the continuous increase in size and not by ecdysis.

Functions of the Skeleton

  • Support: The rigid skeletal support raises the body from the ground, supports some vital organs, and maintains the shape of the body.
  • Protection: The skull protects the brain and houses the inner structures of the ear and eyeball.
  • The vertebral column protects the spinal cord, and the rib cage protects the heart and lungs.
  • The pelvic girdle also protects the abdominal organs.
  • Movement: The several pieces of bones making up the skeleton allow free movement of the body and limbs.
  • Skeleton also serves as a point of attachment to muscles responsible for movement through tendons.
  • Contraction and relaxation of muscles exert pressure on bones to effect movement.
  • Respiration: The rib cage moves during inspiration and expiration.
  • Production of blood cells: The long bones produce blood cells in their marrow before sending them into the circulatory system.


A Joint is where two or more bones meet. The bones are connected to one another by tough connective tissue ligaments, which are elastic; bones are moved relative to one another by an elaborate system of muscles. Joint muscles are attached to the bones by tendons. All muscles have their origin on one bone and their insertion on another situated further away from the center of the body.

Ball and socket joints are found in the shoulder and hip (the head of the humerus fits into the glenoid cavity of the pectoral girdle, and the head of the femur fits into the acetabulum of the pelvic girdle). The ball and socket joint allows movement in several directions.

The hinge joint allows movement in only one plane or direction, as found at the elbow and knee.

Gliding or Sliding joint allows bones to slide over one another, as found at the wrist and ankle.

The Pivot joint allows rotation of one part of the body on another, as found between the atlas and axis, where the odontoid process of the axis acts as a pivot that allows rotation of the head on the vertebral column.

Supporting Tissues in Plants

  • Parenchyma - A packing tissue made up of thin-walled cells with a central vacuole each. The cells have intercellular air spaces. Provides flexibility.
  • Collenchyma - The cells have thick walls that are pronounced at the comers. They provide mechanical support for the plant.
  • Sclerenchyma - The walls of these cells are very thick and are built up in a uniform layer around the entire margin of the cell. Hence they provide rigidity, resilience, and hardness.

Transport System

The movement of materials from one part of the body to another in a living organism is known as transport, translocation, or conduction. The transport system connects different parts of the body with one another and transports food materials to all cells, tissues, and storage organs. It also serves to distribute water, transport waste products to excretory organs, and transport raw materials to food-synthesizing tissues.

Mammalian Circulatory System

The heart, which is located roughly at the center of the chest (thorax) cavity, is surrounded by a protective membrane called the pericardium. The thoracic and abdominal cavities are separated by the diaphragm. The heart is divided into four chambers, with the two upper chambers, known as the atria or auricles being relatively thin-walled. The atria receive blood from the veins. The two lower chambers, known as ventricles, are more muscular than the atria, and the left ventricle is more muscular than the right ventricle because it sends blood to all parts of the body except the lungs. The tricuspid valve separates the right auricle from the right ventricle, while the bicuspid valve separates the left auricle from the left ventricle.

Arteries, Veins, and Capillaries

Arteries are the blood vessels that carry blood away from the heart. They are thick-walled, muscular, and elastic so as to withstand high pressure caused by heartbeat. Arteries divide into smaller arterioles which further subdivide several times to form a dense network of highly microscopic vessels permeating every cell of the body known as capillaries.

Capillaries are tiny vessels whose walls are one cell thick so that water and dissolved substances diffuse freely in and out. The capillaries unite into larger vessels which join to form veins that return blood to the heart.

Veins are the blood vessels that take the blood back to the heart. They are wider and have thinner walls than the arteries. They have valves along their length that prevent the back Now of the blood. All veins carry deoxygenated blood except the pulmonary vein, and all arteries carry oxygenated blood except the pulmonary artery.


It is a liquid tissue containing cells suspended freely in a watery medium called plasma, and it is the means of transporting dissolved nutrients. The cells and cell fragments make up the "formed" elements of the blood. Erythrocytes are the most numerous of the cells, which are disc-shaped, biconcave, and non-nucleated when mature. In an adult, they are produced in the marrow of bones, especially in the ribs, sternum, and vertebrae.

The red color of the blood is due to the presence of an iron-containing pigment called hemoglobin which helps in the transportation of oxygen around the body. Aged erythrocytes are destroyed in the liver and spleen when the rate of erythrocyte loss from the body exceeds the rate of erythrocyte formation anemia results.


Neutrophils and monocytes are phagocytic in action through the ingestion of foreign particles by endocytosis. Lymphocytes function in the production of antibodies that combat antigens. Eosinophils and Basophils, whose numbers are very low in the blood, also play a role in combating diseases. Leukocytes are synthesized in the bone marrow. When a precursor cell in the bone marrow becomes cancerous, the number of leucocyte cells becomes far greater than normal, leading to a condition known as leukemia.


They are much less numerous than the erythrocytes, amoeboid in shape, and nucleated. There are five distinct types, i.e., neutrophils, eosinophils, basophils, monocytes, and Platelets. They are cell fragments produced by large cells in the bone marrow. They are also known as thrombocytes. Platelets are disc-shaped and much smaller than the erythrocytes and much less numerous. Leucocytes play an important role in the clotting of blood.


The straw-colored fluid in which the blood cells are suspended. The major component of the plasma is water, in which dissolved glucose, amino acids, waste products of cell metabolism, hormones, vitamins, and fat droplets, with sodium and chloride ions being the most abundant. 7% of the plasma consists of plasma proteins like fibrinogen, albumin, and globulins.

This is the water and dissolved substances that diffuse from blood capillaries to bathe the tissues of the body as a result of blood pressure and osmotic pressure of the tissues. Living cells absorb food and oxygen from plasma, and their waste products diffuse into it. Lymph is carried away by the lymphatic vessels.

Transportation in Higher Plants

This is achieved by the process of transpiration because transpiration accompanies photosynthesis. Continuous loss of water from the leaves causes suction or transpiration pull or stream by which more water is drawn from the veins in a leaf, from the stem, and finally from the roots and soil. Mineral Salts (dilute solution) used in the synthesis of carbohydrates, protein, etc., are drawn up along with water.

The transpiration stream transports dissolved salts to the leaves from the roots through xylem vessels. The leafy shoot is cut underwater to prevent air bubbles from entering the xylem vessels and blocking them. When placed near a window, the mercury will rise up as the water evaporates from the leaves showing that a pull is being exerted.

The xylem vessels of a freshly dug-up seedling will be strained red when the roots are placed in water containing eosin (which is red in color) for about an hour. Sections of the leaf stalk, stem, and parts of the roots not in the solutions when cut and examined under the microscope will show that the red parts correspond to the xylem vessels. Hence xylem vessels transport water from the roots to the leaves.

The base of the potted plant la covered with a polythene sheet to prevent the evaporation of water from the pot into the bell jar. The rim of the dry bell jar is sealed up with vaseline after the potted plant has been placed under it to prevent the escape of water vapor. A control experiment in which the plant is devoid of leaves and flowers is also set up.

After some time, drops of liquid will be found on the inside of the first bell jar but not in the control experiment. The liquid will turn anhydrous copper sulfate blue or turn blue cobalt chloride paper pink.

Respiratory System

Gas exchange in aquatic organisms

In fishes, gas exchange organs are the gills that present a large surface to water in which they are in contact so that oxygen present in the water diffuses into the cells of the gills. Gills are richly supplied with blood (vascularised) which transports oxygen to the inner tissues of the body. Blood again transports carbon dioxide from the inner tissues to the gills, and from the gills, carbon dioxide passes out by diffusion.

Gas exchange in roots and stems

Gaseous exchange in woody stems and mature roots, whose barks are protected by layers of dead cork cells that are impregnated with suberin, takes place through lenticels. Lenticels are non-suberised pores that perforate mature roots and wood stems, thus enabling oxygen to reach the intercellular spaces of the interior tissues and similarly allowing COy to be released to the atmosphere.

Gas exchange in the leaf

The exchange of gases in the leaves and young green stems takes place through pores called stomata. During photosynthesis, CO diffuses from the outside air through the stomata into the air spaces of the spongy layer and from here into the air spaces between the palisade layer cells and then into the cells. Oxygen produced as a by-product of photosynthesis diffuses out of the stomata in the same way.

Stomata open when light strikes the leaf so that the guard cells become turgid, and at night when the guard cells lose turgor, the stomata close as a result of the cells returning to their original shape.

Gas exchange in Terrestrial animals

Organs of gaseous exchange are located within the body cavity, where they are protected from mechanical damage and excessive loss of moisture. Among insects and some other terrestrial invertebrates, gaseous exchange takes place through an extensive network of air-filled tubes called Trachea, which opens outside through small holes in the exoskeleton called spiracles.

Lungs are the organs of gaseous exchange among the air-breathing land vertebrates. The surface area of the lungs is increased by alveoli which are highly vascularised. In amphibians, the skin and buccal cavity form supplementary organs of gaseous exchange. An efficient respiratory surface must be well protected from damage, exposed to a source air, have a large surface area, be richly supplied with blood, be very thin and moist, and be highly ventilated.

In mammals, the efficiency of lung ventilation is improved by the presence of a muscular diaphragm.

During inspiration (inhaling), the external intercostal muscles contract, fifing the ribs upwards and outwards. This motion increases the volume of the thoracic cavity, and air moves into the lungs as a result of low pressure. During expiration (exhaling), the external intercostal muscles draw the ribs down and inwards, thus reducing the volume of the thoracic cavity, and hence the air is forced out of the lungs.

Excretory Systems

Among terrestrial plants, waste products of metabolism, such as salts and organic acids, are simply stored in the plant either in the form of crystals or, as in perennial plants, the wastes are deposited in non-living heartwood and are also eliminated when the leaves are shed.

In Platyhelminthes, like Fasciola and tapeworms, the excretory organs are the Name cells. In earthworms and many other invertebrates, the excretory structures are called nephridia. In terrestrial arthropods, like the insect, the excretory system is made up of malpighian tubules, which lie in the hemocoel and are bathed by blood. The waste product is uric acid which passes outside along with feces.


The most important excretory organs of vertebrates are the Kidneys which receive blood from the dorsal aorta through the right and left renal arteries and send out blood through the right and left renal veins.

Trinsvenection of the kidney shows an outer cortex, beneath which is the medulla, and beneath the medulla, the hollow pelvis of the kidney. The cortex and the medulla consist of thousands of nephrons which are the structural and functional units of the kidney. Each nephron consists of a Bowman's capsule, also called renal corpuscle or malpighian corpuscle, with a network of blood capillaries called glomerulus within it.

The remaining part of a nephron is a tubule consisting of three distinct portions, i.e., the proximal convoluted tubule, the U-shaped loop of Henle, and a distal convoluted tubule.

The tubule then leads into the pelvis of the kidney via the collecting tubules. The cortex contains only the renal corpuscle and the convoluted tubules, while the medulla contains the loop of Henle and the collecting ducts.

Ultrafiltration of the blood takes place in the Bowman's capsules, and glucose, amino acids, and large amounts of inorganic ions are reabsorbed at the proximal convoluted end from the glomerular filtrate.

The sodium salt is actively transported out of the fluid as it passes through the loop of Henle, and finally, water is reabsorbed from the fluid at the distal convoluted tubule and the collecting ducts.

From here, the filtrate passes through the pelvis into the urinary bladder via the ureter. When the bidder becomes full, the urethral sphincter guarding the outlet relaxes so that urine Nows out through the urethra. Urine contains urea, water, and sodium chloride in addition to other compounds. In the presence of antidiuretic hormone, dilute urine is produced. Kidney stones are solid particles formed in the kidneys that can block kidney tubules.

Diuresis is a condition of the kidney which causes an increased secretion of urine.


The liver regulates blood sugar by the conversion of excess blood sugar into glycogen. It produces bile for bile salts and pigments after the decomposition of aged erythrocytes and stores excess iron from such decomposition.

The liver carries out the deamination of excess amino acids that leads to the formation of urea, ammonia, etc., which are excreted by the kidneys. The liver Carries out detoxification of poisonous compounds produced in the large intestine by bacterial action and renders them harmless. The liver produces fibrinogen which is essential for blood clotting. Infective hepatitis is a viral infection of the liver, causing inflammation and jaundice. Gallstones are solid particles formed within the gallbladder and can block the bile duct.


It is made up of an outer epidermis and an inner dermis. The epidermis has an outer cornified layer (stratum corneum of dead flat cells middle layer called the granular layer (stratum granulosum), which contains living cells, and an innermost malpighian layer (stratum Malpighi) which is a continuous layer of cells that are actively dividing and so produce new epidermis.

The epidermis contains the pigment melanin, which determines the skin color and protection against harmful ultraviolet rays. The dermis is a layer of connective tissue fibers, blood capillary, nerve ending, sweat glands, hair follicles, and lymphatics with many glands, hair follicles, and lymphatics. Below the dermis is a layer of subcutaneous fat. An increase in the width of blood vessels at high temperatures is known as vasodilation, and a decrease in the width is known as vasoconstriction.

The pigment melanin protects the body from the ultraviolet rays of the sun. Sebum produced by the sebaceous glands of the skin acts as a mild antiseptic, apart from keeping the skin supple and waterproof.

It is a sense organ because of the presence of nerve endings.

The sweat produced by sweat glands contains water, urea, and sodium chloride, which makes the skin an excretory organ. In birds and mammals, the skin helps in the maintenance of a constant body temperature (homeothermy) and insulation of the body.

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