TISSUES. Permanent Tissues. Parenchyma

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1 TISSUES BASIC CONCEPTS: 1) Group of cells having a common origin and similar in structure and function is known as tissue. 2) Plant tissues are primarily classified into two groups: (i) Meristematic and (ii) Permanent tissues. 3) Meristematic cells are capable of dividing continuously to produce new cells. The meristematic tissues are present only at the growing regions such as shoot tip, root tip and cambium. 4) Depending on the region where they are present, meristematic tissue is classified as apical, lateral and intercalary. 5) The cells of meristematic tissue are very active, have dense cytoplasm, thin cellulose walls and prominent nuclei. 6) Permanent tissues are those which have lost their power of division. They have differentiated and attained a permanent shape suitable for their function/s. 7) Permanent tissues may be simple or complex. Simple Parenchyma Permanent Tissues Collenchymas Xylem Complex Phloem Selerenchyma 8) Simple plant Tissues: Parenchyma and collenchymas cells are living and thin walled cells. Collenchymas cells have thickened corners due to deposition of cellulose and pectin. Sclerenchyma tissue cells are lignified, dead and do not contain protoplasm. 9) The epidermis of leaves have small pores, called stomata. Stomata are enclosed by two kidney shapped cells called guard cells. Stomata are useful for exchange of gases and transpiration. 10) Complex plant Tissues: these are mainly conducting tissues and are of two types: Xylem and phloem. (i) Xylem consists of tracheids, vessels(tracheae), xylem parenchyma and xylem sclerenchyma. Xylem conducts water and dissolve minerals to different parts of the plant, especially to leaves, from roots. Xylem consists of dead cells such as tracheids vessels and xylem sclerenchyma. (ii) Phloem is conducts prepared food from the green leaves/parts to other parts of the body. It is composed of four elements-sieve tubes, companion cells, phloem parenchyma and phloem fibres. It is a living conductive tissue. 11) The secondary meristem produces the cork or the bark of the tree. Cells of cork are dead, compactly arranged without intercellular spaces. Cork cells have deposition of suberin on the walls that makes them impervious to gases and water. 12) Animal Tissues are of four types in higher animals including human being. (i) Epithelial tissues: it is the covering tissue. On the basis of their shape and functions they are classified as given below: a. Squamous(flattened) b. Cuboidal (cubical) c. Columnar (tall or pillar like) d. Ciliated (cells having cilia) e. Glandular (with secretary function) (ii) Muscular Tissues: They are made up of muscle cells, called muscle fibres. There are three types of muscle fibres: a. Striated muscle are long cylindrical un branched and multinucleated E SUDAMA NAGAR RING ROAD NEAR PHOOTI KOTHI SQUARE , Page 1

2 b. Un striated muscle (smooth muscle or involuntary muscle) are long, pointed at ends and uninucleated. c. Cardiac muscle cells are cylindrical, branched and uninucleated. (iii)connective Tissues: Their functions are binding, supporting and packaging together with different organs of the body. The different types of connective tissues in our body are: Bone, cartilage, tendon, ligament and blood. (iv) Nervous Tissues: They are composed of nerve cells called neurons. They are specialized to conduct nerve impulses(i.e. stimulus and its response from nervous tissues). Brain, spinal cord and nerves are composed of nervous tissue. IMPORTANT TERMS: 1) Division of labour in multi cellular organisms: In multi cellular organisms cells are differentiated into different group of cells, called tissues, to perform different functions i.e. division labour in carrying out life processes. While in unicellular organism a single cell performs all the life processes. 2) Cell differentiation: The process by which cells are specialised to do specific function and form permanent tissues is called cell differentiation. 3) Pits: Oblique thin areas found in the walls of sclerenchyma cells and tracheids and vessels of xylem are called pits. 4) Corpuscles: The cells found in the blood plasma are called corpuscles. These are red blood corpuscles (RBC) and white blood corpuscles (WBC). 5) Matrix: Matrix means medium in which cells are dispersed. It may be solid as in bone or cartilage and fluid as in blood. 6) Cyton: The cell body of a neutron which has a nucleus and cytoplasm. 7) Dendrites: The fine fibres arising cell body of a neutron. 8) Axon: The single elongated fibre, also called fibre, arising from the cell body of a neuron. QUESTIONS: 1) How many types of meristems are present in plants, on the basis of position? On the basis of location of meristem, it is classified into three types: (i) Apical meristem is present at the tip of stem, root and their branches. (ii) Intercalary meristem is found at the leaf base, leaf sheaths of monocots (e.g. grasses), above the nodes (i.e. below the base of internodes as in grasses) or below the nodes (i.e. at the upper most region of internodes as in mint.) (iii)lateral meristem is found in vascular bundles and known as cambium. The meristematic tissue, which may appear in most of dicot plants, is known as cork cambium. Both of these cause increase in girth of plants. 2) What are plant permanent tissues? Plant permanent tissues are group of cells which are produced by meristematic tissue. But they lose the ability to divide. Permanent tissues get differentiated after their formation into specialised to perform particular function/functions. They have vacuolated cytoplasm. Permanent tissues may be living e.g. parenchyma or dead e.g. sclerenchyma. 3) With help of only schematic line diagram shows classification of main permanent tissues. Permanent Tissues Simple Parenchym Collenchyma Selerenchym Xylem Comple Phloem 2327 E SUDAMA NAGAR RING ROAD NEAR PHOOTI KOTHI SQUARE , Page 2

3 4) Explain the structure of parenchyma. What are its major types? Parenchyma: It is the basic or fybdamental tissue found in plants. These are thin walled, circular or polygonal cells. They are living and consists of cytoplasm and a nucleus. There are many small or a single big central vacuole. When may not have intercellular space or may have intercellular spaces. They may have colourless leucoplasts. Some parenchymatous cell have pigmented chromoplats. The most important are the cells which contain a number of chloroplasts and the tissue is green, it is known as chlorenchyma. Some non-green chromoplasts provide different colours to flowers and fruits. Sometimes the cells contain big air spaces in between them. Such tissue is known as aerenchyma. On the other hand some tissues are green, containing many air spaces then it is called spongy tissue. (iii)parenchymatous cells also store waste products such as tannin, gum, crystals of chemicals etc. (iv) Chlorenchyma containing chlotoplasts prepare food through photosynthesis. (v) Parenchymatous cells containing non-green chromoplasts provide characteristic colour to flowers(e.g. petals) and fruits. 6) What are collenchymas cells? Explain their structure with the help of labelled diagram. What is its major function. The cells in this type of tissue are living thick walled. The thickening of the walls are due to cellulose and pectin which develops more in the corners of the polygonal cells. These cells are also living and may contain chlotoplasts. The cell walls may have pits on them. These cells are found mostly in the stems in hypodermal region. 7) What are the main functions of collenchymas? The main functions of collenchymas are to provide mechanical support, tensile strength and elasticity and especially to herbaceous plants, flexibility to the organ in which they are present. The chollenchymatous cells when contain chloroplasts, help in manugacture of sugars and starch. It is generally found in peripheral portions of stem and leaves. Parenchyma cells are mostly iodiametric, i.e. having similar sides. Parenchyma acts as a packing tissue and therefore, it is found in between other tissues. Parenchyma tissue cells store starch, proteins, minerals etc. 5) Write the main functions of parenchyma. Functions of parenchyma: (i) They store and assimilate food. (ii) They provide mechanical support as they maintain the turgidity of cells. 8) Describe the structure of sclerenchyma. Write its major functions. sclerenchyma (scleras-hard) is the chief mechanical tissue of plants. The cells are 2327 E SUDAMA NAGAR RING ROAD NEAR PHOOTI KOTHI SQUARE , Page 3

4 usually long, narrow, pointed at both ends uniformly thickened by the deposition of lignin. The walls are often very highly thickened so that the lumen or dell cavity is nearly obliterated. They are usually provided with simple pits which may be oblique or straight. The sclerenvhyma cells are also known as fibres or sclerenchyma fibres, since they are elongated thread-like. Their average length is 1 to 3mm. In angiosperms and 2 to 8mm. In gymnosperms. However, in some cases the fibres are much longer up to 550mm. (e.g. cannabis-hemp; linum-flax, etc). They are dead cells and their main function is to provide strength and rigidity to the plant. Sclerenchyma is very widely distributed, occurs in the formof distinct layers or patches and forms the chief constituent of hard parts of the plants. Sometimes the sclerenchyma cells are not much longer than they are board and are almost is diametric without pointed ends. Their walls are very heavily thickened so that lumen is almost obliterated. Such special types of sclerenchyma cells are known as stone cells or sclereids or sclerotic cells. The stone cells may be loosely arranged or closely packed and make the plant part hard and firm. They are found in hard seeds, nuts, stony fruits and also in stems and leaves. Functions: Sclerenchyma cells both sclenchyma fibres and sclereids are dead cells and purely mechanical tissue. Sclerenchyma fibres gives necessary strength, rigidity and flexibility to the plant body. Fibres are thick walled and excellent textile fibres of commercial importance such as jute,sunn hemp. Sclereids form the major part of hard shells walnut, almond nut and other kinds of nuts. Sclereids also make the pulp of fruits such as guava, pear, etc. 9) What are protective tissues? Protective tissues: The primary axis of plant consists of a single outermost layer called epidermis. Epidermis extends over the entire surface e.g. leaves, flowers, stem and root of the plant body. It consists of rectangular, closely fitted thin walled parenchymatous cells. The cell lack intercellular spaces. This outermost layer is one cell in thickness and is covered with cut in. These tissues protect internal tissues of the plant body. Generally, in old dicot plant roots and stem, secondary meristem is formed which develops cork cells. Cork cells do not have intercellular spaces and are dead cells. The wall of cork cell are heavily thickened by the deposition of suberin. Function of cork: Cork is protective in function. It is light, insulative and nonpermeable to water and does not catch fire 2327 E SUDAMA NAGAR RING ROAD NEAR PHOOTI KOTHI SQUARE , Page 4

5 easily. Cork is used as shock absorbers in linoleum and sports goods. 10) Does the outer most protective layer is throughout continuous? If not, what interruptions are usually found on leaves and herbaceous parts of the plant? The outermost layer of cells i.e. usually the epidermis is not continuous at some places e.g. on the surface of leaves or green herbaceous stems. The epidermis of the young shoot and leaves contains numerous minute pores called stomata. Each stomata opening is surrounded by two semi lunar cells known as the guard cells. The term stoma (plural-stomata) is applied to the stomatal opening plus the guard cells. The guard cells are living and contain chloroplasts. Their inner walls (wall towards opening) are thicker and outer walls thinner. The guard cells regulate the opening and closing of the stomatal pore. openings. The process is called Transpiration. (iii)when there is shortage of water, stomatal openings get closed. Thus, reduce water lose. Stomatal openings also close down during night. Thus, stomata regulate water lose from plants i.e. they regulate transpiration. 12) What is the difference between: (i) Meristematic cells and permanent cells. (ii) Parenchyma and collenchymas. (i) Meristematic cells Permanent cells 1 They have dense cytoplasm and a large centrally placed nucleus. 2 These cells are capable of dividing cells. They have large central vacuole, and normal nucleus. They attain permanent shape and are not capable to produce new cells. Fig: A. Open stomata, B. Closed stomata 11) Write major functions of stomata present in the epidermis. Major functions of stomata: (i) Stomata are essential for exchange of gases between the plant and the atmosphereoxygen and carbon dioxide. (ii) Normally, plants eliminate excessive water in the form of vapour through stomatal (ii) Parenchyma 1 It is living and mainly storage tissue. Its cells store may store waste products such as tannin, resins, crystals etc. 2 Parencymatous cells may or may not have intercellular shape. Their walls do not have thickening at the corners. Collenchymas It is living and mainly provides tensile strength the organ in which they are present. Collenchymatous cells, usually do not have intercellular spaces. They have thickening at the corners of cell walls due to deposition of cellulose and pectin E SUDAMA NAGAR RING ROAD NEAR PHOOTI KOTHI SQUARE , Page 5

6 1) Differentiate between collenchymas and sclerenchyma. Collenchymas Sclerenchyma wish stand various strains. and hardness to the plant part in which they are present e.g. shells of nuts. 1 The cells of collenchymas are living and have the cytoplasm and the nucleus. 2 The collenchymas cells have thickening of cellulose and pectin at the corner of its cells. 3 They provide mechanical support and elasticity to the plant organ. The cells are dead. They do not have the cytoplasm and the nucleus. The sclerenchymatous cells do not have such thickenings. They mainly provide mechanical support to plant and seed coat of plants such as nuts. It provides stiffness to the organ. 4 Collenchymas cells They do not contain may contain chlorophyll in any chlorophyll and can condition as they are also help in the dead cells manufacture of starch and sugar. 2) What are the difference between sclerenchyma fibres and sclereiods? Sclerenchyma fibres 1 They are dead sclerechmatous cells which are long, pointed at both end and have lignified cells. 2 Their main function is to give mechanical support to plants to Sclerenchyma Sclereiods They are dead sclerenchymatous cells which are isodymatric and do not have definite shape. They provide local mechanical needs. They provide firmness 3) What is xylem? Explain its structure. Which one of its component is very important and why? xylem is a complex plant tissue or vascular tissue. Structure: Xylem consists of four kinds of cells (also known as elements). (i) Tracheids: A tracheid is an elongated hollow cell with its both ends tapering. The walls of these cells are thick by the deposition of lignin. At certain spots lignin is not present. These spots are termed as pits. These cells are arranged in such a fashion so as to form a system of long tubes and channels in which water can move readily. The tracheids are dead cells. The walls show various kinds of thickenings. (ii) Vessels: vessels are tube like structures formed by a number of cells placed end to end with their transverse walls dissolved or absorbed. The side walls of these tubes also have deposition of lignin. The thickening of the walls show various kinds of patterns. They are also dead cells. (iii)wood (xylem) parenchyma: These are parenchyma, thin walled living cells. They help in short term conduction of materials. They also store starch and fatty materials. (iv) Wood fibres: Xylem sclerenchyma consists of lignified dead fibres. They provide mechanical support. The most important element of xylem is vessel because they conduct most part of water and mineral salts upward from roots to different parts of shoots E SUDAMA NAGAR RING ROAD NEAR PHOOTI KOTHI SQUARE , Page 6

7 A. Phloem also contains phloem fibres, also known as Bast Fibres. They provide mechanical support. B. 4) Describe the structure of phloem. The main conducting part of phloem is sieve tube which is formed of elongated cylindrical cells arranged in vertical rows. The terminal walls of each sieve tube member has many minute pores through which food material passes very easily. The entire porous plate is termed as sieve plate. Each sieve tube member is supported by a long parenchymatous cell called the companion cell which helps the sieve tubes in the conduction of food material. Fig: cross section of phloem showing sieve plate Phloem parenchyma formed of parenchymatous cells. They store the food material. 5) Differentiate between: (i) Xylem and phloem (ii) Vessel and sieve tube (iii)tracheid and vessel. (i) Xylem Phloem 1 It is dead tissue (except xylem parenchyma). 2 It is composed of tracheids vessels, xylem parenchyma and xylem fibre. (in stems) It is a living tissue(except phloem fibre) It is composed of sieve tube, sieve plates, companion cell, phloem parenchyma and phloem fibre. Fig: longitudinal section of phloem 3 It transports water and mineral from roots to other parts of the plant. (ii) Vessel 1 It is long distance channel made up of a It transports prepared food from leaves to the other plant parts. Sieve Tube It is a long distance channel made up of a 2327 E SUDAMA NAGAR RING ROAD NEAR PHOOTI KOTHI SQUARE , Page 7

8 number of dead cells with hollow lumen. 2 Vessel conducts water and mineral salts. number of living cells with vacuolated cytoplasm. Sieve tube conducts organic nutrients. 3 The wall is lignified. The wall is unlignified. 4 The wall is thick The wall is thin. 5 The end walls are commonly dissolved completely. 6 Besides conduction of sap, a vessel provides mechanical strength. (iii) Vessel 1 A vessel consists of a large number of cells fused together in a single file. 2 The ends are rounded. 3 The septa between adjacent cells of a vessel are usually absent. 4 The vessel is quite long (1-6 metres). 5 The wall is less thickened. The end walls are perforated to form sieves plate. It does not provide any mechanical strength. Tracheid A tracheid consists of a single cell. The ends are pointed. The walls between adjacent tracheids, remain intact. The tracheid is comparatively short (generally 1mm). The wall is more thickened. 6 The lumen is wide. The lumen is narrow. 6) What are epithelial tissues? Epithelial tissues from a covering on an external or internal surfaces of the animals. Epithelial tissue also called protective tissue in animal body. The cells are closely associated and arranged on a very thin gelatinous basement membrane. An epithelial tissue may be composed of one (simple epithelium) or more layers of cells (compound epithelium). The skin, surface layers of mouth, alimentary canal, lungs etc. Are made of epithelial tissues. it also forms a barrier to keep different body system separate. The cells contain cytoplasm and nucleus bounded by plasma membrane. 7) What are the five main functions of simple epithelial tissues? The five main functions of simple epithelial tissues are: (i) The cells from the outer layer of skin. They protect the underlying cells from drying, injury, bacterial and chemical effects. (ii) They from lining of the mouth and alimentary canal other internal organs and protect these organs. (iii)they help in absorption of water and other nutrients, especially in alimentary canal. (iv) They help in the elimination of waste products. (v) Some of them are greatly specialized (glandular cells) and perform secretary function. 8) What are the various forms of cells of epithelial tissue? Describe briefly. Simple epithelial tissue: (i) Squamous epithelium: The cells of this tissue are broad, flat forming a pavement like appearance. It is found in the alveoli of the lungs. Bowman s capsule, membranous labyrinth of internal ear, peritoneum of coelom and blood vessels. (ii) Cuboidal epithelium: The cells of this tissue are cube like in appearance. It is 2327 E SUDAMA NAGAR RING ROAD NEAR PHOOTI KOTHI SQUARE , Page 8

9 found in kidney tubules and salivery glands etc. (iii)columnar epithelium: The cells of this tissue are more tall than wide, placed side by side. Their nuclei are situated near the bases. They may have on their free surfaces finger like projections- the microvilli. This tissue usually lines the internal surfaces of stomach and intestine. (iv) Ciliated epithelium: The cells of this tissue are modifications of columnar epithelial cells. They have on their free ends many small, vibratile cilia. These are found in kidney tubules, trachea oviduct etc. (v) Striated squamous epithelium: Cells of this tissue are squamous epithelial cells which are arranged in many layers to prevent wear and tear of parts. Tounge, oesophagus and lining of mouth are also made of striated squamous epithelium. (vi) Glandular epithelium: Sometimes the cells aggregate to form masses of cells, the glands. These glands secrete juices helpful to the organism. We have a number of such glands in our body, viz. Sweat glands which secrete sweat; oil glands which secrete oily substance. Both these glands are present in the skin. Salivery glands present in the mouth secrete saliva. (vii) Sensory epithelium: At certain places the cells of columnar epithelium gets modified into sensory cells. These cells are innervated at their bases by sensory nerve fibres. Such cells are found in sense organs. (viii) Germinal epithelium: They are found in gonads i.e. testes and ovaries. They produces gametes i.e. sperms and ova. 9) What are muscular tissue. What is their function? This is composed of contractile, fibre-like cells. Intercellular substance is very little. The cells of muscular tissue remain enclosed or surrounded by connective tissue. Functions: Being elongated in structure they are also called muscle fibres. The movement of the body or limbs is brought about by contraction and relaxation of contractile proteins present in muscle cells. The movements of the internal organs such as heart and alimentary canal are all caused by muscle tissues; even when body remains stationary. 10) Es. Also explain the three types of muscle fibres. Also write the location where they are found in the body. (i) Unstriped: (Also known as smooth, involuntary or plain muscles). This type of muscular tissue consists of spindleshaped, long fibre-like cell with a nucleus at the centre. The ends are undivided. This type of muscles is present in alimentary canal, muscular coat of blood vessels etc. (ii) Striated muscles: (Also known as striped or voluntary muscles because of their function being in our control or will). This type of muscular tissue cells are very long fibres, enclosed in a membrane known as sarcolemma. The cells are multi-nucleated. Each fibre has several longitudinal 2327 E SUDAMA NAGAR RING ROAD NEAR PHOOTI KOTHI SQUARE , Page 9

10 myofibrils embedded in cytoplasm. On these myofibrils are present characteristic light and dark bands which give it a striated appearance. These muscles are attached to the skeleton; so are also called skeletal muscles. (iii)cardiac muscles: These muscles are found in heart. They are not under the control of the will. They contract rhythmically and involuntarily throughout life without the sign of fatigue. Structurally they show the characters of both unstriated and striated muscles. They are made up of branched fibres. These fibres are multinucleated and show alternate light and dark bands (striation). Fig: A. Unstriped, B. Striped, C. Cardiac 11) What are the various functions of all types of epithelial tissues? Epithelial tissues help in 1. Protection 2. Absorption 3.Excretion 4.respiration 5. Conduction 6.sensation 7.regeneration 8.pigmentation 9. Secretion 10.formation of exoskeleton and 11. Production of gametes. 12) Write main characteristic features of skeletal, smooth and cardiac muscles. Characte r Skeletal (striated) Smooth muscles Cardiac muscles muscles 1 Shape of Cells are cells long cylindrical, nontapering and unbranche d 2 Nucleus Many nuclei which are situated towards the periphery of muscle fibre. 3 Striatation Transverse alternate light and dark bands (stritations ) are present 4 Mode of Voluntary contractio (work n upon our will) contract rapidly but soon undergo fatigue. Cells are long with tapering ends (spindle shape) and unbranche d The cells have only one nucleus (uninuclea -ted) situated in the centre. Stritations or stripes are absent. Involuntar y not under our will. Contract comparati- Vely slow but do not fatigue. Cells are nontapering, cylindrical and branched Each cell contains one or two nuclei situated in the centre. Cells have faint stritations. Involuntar y ; they rythnically contract and relax throughout life with out fatigue under normal conditions. 5 Example Hands, Wall of Present in of legs and stomach, heart. location other intestine, skeletal muscles. ureter, bronchi etc. 13) What are three main categories of connective tissue? Categories of connective tissue 2327 E SUDAMA NAGAR RING ROAD NEAR PHOOTI KOTHI SQUARE , Page 10

11 (i) Connective tissue proper: There is a matrix in which generally two types (white and yellow) fibres are present. In between these fibres some other cells are present in the matrix. (ii) Skeletal tissue: This type of tissue forms the skeleton of an organism. It may consist of notochord, cartilage and bone. A cartilage has a matrix, called chondrin, in which a network of collagen fibres is present. There are present cells known as chondrocytes. There may be present empty spaces filled with fluid known as lacunae. In bones, matrix is formed of a protein called ossein impregnated with phosphate and carbonates of calcium and magnesium. (iii)fluid tissue: Blood and lymph tissues are called fluid tissue. These are specialized connective tissue. It consists of liquid matrix with no fibres. In this liquid matrixplasma there are corpuscles. Blood transports food material, gases and other substances to the various parts of the body of an animal. 14) What are fibrous connective tissues? It is of two types: (i) The white fibrous connective tissue has white, nonelastic, unbranched fibres which are united into bundles. This sort of tissue is very tough and forms the tendons, ligaments and covering of muscles. Tendons are strong, tough and smooth, rope like structures which serve to attach muscles with the bones. The ligaments are elastic fibres which connect two bones together. (ii) The yellow fibrous connective tissue: Its fibres are fine thread like structures. These fibres are quite elastic. The kind of tissue is found in the walls of arteries and lungs and binds the skin with the underlying muscles. 15) Describe the structure of cartilage and bone. It is a solid but semi-rigid and flexible connective tissue. It has large, bluntly angular cartilage cells called chondriocytes. They occur in clusters of 2 or 3 in small spaces scattered in the matrix. The cartilage is bounded externally by a sheath and eustachin tube. Bone: Bone is solid, rigid and strong connective tissue. Its matrix become hard due to the deposition of salts of calcium and phosphorous. Osteocytes or bone cells are present in irregular spaces-lacunae in the matrix, interconnected by fine canals called canaliculi. The matrix occurs as layers-the lamellae arranged in concentric rings around narrow longitudinal cavities called haversian canals. This canal carries blood vessels and nerves. The haversian canals are inter-connected by transverse channels called Volkmann s canals. The long bones have central cavity filled with bone marrow and is called marrow cavity. The bone marrow is formed of blood vessels, nerve fibres and adipose tissue. Blood cells are produced in bone marrow. The bone is bounded externally by a tough sheath called periosteum. Fig: T.S. of Cartilage 2327 E SUDAMA NAGAR RING ROAD NEAR PHOOTI KOTHI SQUARE , Page 11

12 man about 7500 of them are present. They are devoid of haemoglobin. These are subdivided into following categories: WBC Granulocytes Agranulocytes Fig: T.S. of bone 16) Explain the structure of a fluid connective tissue. blood is a fluid connective tissue like lymph. Blood consists of (i) Blood plasma: It forms generally fluid matrix which contains 85 to 90% water, 7% different types of proteins, 0.9% of salts, about 0.1% glucose and a very small amount of hormones, wastes, etc. In the plasma. These are: (a) Red Blood Corpuscles (Erythrocytes) or RBC: The red blood corpuscles of man and other mammals are biconcave disc-like structures devoid of nuclei. Throughout the cell a network of protein and gat-like compounds is present. They are yellowish in colour and extremely small. They measure 4.5 μ in length and 7.0 μ in width (μ=1/1000 of a mm). The RBC of frog on the other hand are nucleated. The number of RBC in various vertebrates differs. In men and women the number is about 5,400,000 per cubic mm respectively. The number decreases or increases under pathogenic conditions. The most important function of RBC are transport of oxygen, aiding the transport of CO 2 and the prevention of excess of acidity in the blood. (b) White Blood Corpuscles (Leucocytes) or WBC: These are comparatively smaller in size, semi-transparent, colourless, irregular in appearance. In one cubic mm of blood of Basophiles Eosinophils Neutrophils Lymphocytes Monocytes Granulocyte: These are irregular amoeboid leucocytes. Their cytoplasm contains many small granules hence the name granulocytes. They are about 70% of the total leucocytes present in the blood. Basophiles: These are small, 8-10μ in diameter. Their nucleus is usually multilobed often S-shaped. Their function is unknown. They are easily strained with basic dyes. Eosinophils: Their size varies from μ. They have a bilobed nucleus. They are quite active and their functions are phagocytic. In man, if the percentage of these eosinophils increases, a disease called eosinophilia results. They can be stained with acid dyes. Neutrophils: They have a diameter of about 9-12 μ. Their nucleus is multi-lobed. They are very active and phagocytic. Agranulocytes: As the name suggests their cytoplasm does not contain granules. They have a large nucleus and are of two types. Lymphocytes: Size 7-8, μ. They are round, slow moving and phagocytic in functions. Monocytes: They have kidney shaped nucleus. They are slow moving and phagocytic E SUDAMA NAGAR RING ROAD NEAR PHOOTI KOTHI SQUARE , Page 12

13 (c) Blood platelets: These are small, 2-4 μ in diameter. They are without nucleus. Their main function is to liberate thromboplastin which causes blood clotting. 17) Give two differences between striated and unstriated muscles. Striated muscles Unstriated muscles contains a distinct nucleus and has a special kind of granule, called Nissel s granule in the cytoplasm. In some nerve cells the axon has a thick while covering called non-medullary sheath. These are called medullated fibres. When this sheath is absent, it is called nonmedullated fibres. In the medullated fibres, the sheath is not continuous- there are gaps along the entire length. Each gap is called nodes of ranvier. The terminals end of axon is without sheath and branched. The axon of one neuron remains in contact with the branches of dendrites from another neuron. The region of contact is called synapse. Each nerve cell receives message through the dendrites and sends message through the axon. 1 These are cylindrical, with non-tapering ends. These are spindle shaped and have pointed tapering ends. 2 Transverse alternate light and dark bands or striatation can be seen. 3 There are many nuclei (multinucleated), these nuclei are situated towards the periphery of the muscle fibre. No light and dark bands or striatations are seen. The cell has only one nucleus ( uninucleated) situated in the centre. 18) What is nervous tissue? Nervous tissue is made up of nerve cells or neurons. Each nerve cell is spider shaped and a number of processes arise from the cell. Most of the processes are small and branched and known as dendrites. One process is unbranched and long. This is called axon. The cell body 19) Why do blood and lymph called as connective tissues? The fluid tissue (blood and lymph) connects various parts (cells) of the body. It supplies nutritive materials, oxygen and hormones collected from different organs to the body tissues. It also collects waste materials from different body tissues and delivers to excretory organs. It also plays protective role. 20) Differentiate between tendon and ligament. Tendon Ligament 1 It is the strong extensible attachment of a skeletal muscle It is the band of dense connective fibres which connects a 2327 E SUDAMA NAGAR RING ROAD NEAR PHOOTI KOTHI SQUARE , Page 13

14 to a bone. bone with another bone. 2 It contains thick parallel bundles of white collagen fibres. It contains both white collagen and yellow elastic fibres running in different direction. 3 It is non-elastic band. It is elastic band. 4 Fibroblasts lie in Fibroblasts almost continuous scattered. rows. 21) Differentiate between bone and cartilage. Bone Cartilage 1 Bone is inflexible and hard. 2 It matrix contains protein ossein and calcium phosphate. 3 Matrix of bone is impregnated with abundant quantity of calcium salts. 4 Osteoblasts (bone forming cells) are quite distinct from osteocytes (bone cells). lie Cartilage is usually flexible or elastic and soft. The matrix of the cartilage contains protein chondrin. Calcium is rarely present in the matrix of cartilage. There is little differentiation between chondroblasts (cartilage forming cells) and chondrocytes (cartilage cells). outgrowths. 6 The lacunae (cavities or spaces) are provided with numerous fine branches called canaliculi. 7 Its matrix shows concentric lamellae. 8 Bone has Haversian canals and marrow cavity. 22) Complete the table : Simple Simple tissue Parenchyma Collenchymas The canaliculi are absent. Matrix homogeneous. is Cartilage is devoid of such structures. Permanent tissue Collenchymas Xylem Permanent tissue Simple Complex tissue Xylem Selerenchyma Phloem 5 Bone cell (i.e. osteocytes) have irregular outline due to the presence of a number of protoplasmic The cells of cartilage, chondrocytes, are oval in outline E SUDAMA NAGAR RING ROAD NEAR PHOOTI KOTHI SQUARE , Page 14