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STRUCTURAL ORGANISATION IN ANIMALS 111 Jr|11th|I PUC NEET|BIOLOGY:VOL-II ANIMAL TISSUES Tissue : A group of cells in which cells are similar in structure, function and origin is called tissue. Group of similar cells along with intercellular substance perform a specific function such organisation is called tissue. But in a tissue, cells may be dissimilar in structure and function but they are always similar in origin. Organ : Tissues are organised in specific proportion and pattern to form organ. Organ system :When two or more organ perform common function by their physical &/or chemical interaction, they together form organ system. Division of labour : Cell, tissue, organs and organ systems splits up the work in a way that they exhibit division of labour. On the basis of functions & structure tissues are of four types : 1. Epithelium/Epithelial Tissue : Covering & protective tissue. 2. Connective Tissue - To connect structures, provide support to the body and transport substances in the body. 3. Muscular Tissue - Helps in contraction & locomotion. 4. Nervous tissue - To generate and conduct nerve impulses in body. HISTORICAL BACKGROUND Word Epithelium was given by - Ruysch Word animal tissue was coined by - Bichat Plant tissue by - Grew). Study of tissue - Histology. Histology word was given by - Mayer Father of Histology - Bichat Detail study of tissue is called Microscopic anatomy. Founder of microscopic anatomy - Marcello Malpighi EPITHELIUM TISSUE 1. During embryonic development epithelium orginates firStratified 2. Power of regeneration is present in this tissue while power of regeneration is absent or least power is found in nervous tissue. 3. This tissue faces either a body fluid or outside environment and thus provide a covering or a lining. 4. Word epithelium is composed of two words. Epi - Upon Thelia - growth A tissue which grows upon another tissue is called Epithelium. 5. It always rest upon underlaying connective tissue. Epithelium is the only tissue in which cells are always arranged in uniform layer. Epithelium cells are compactly packed with little intercellular matrix. 6. Due to absence of intercellular spaces blood vessels, lymph vessels & capillaries are unable to pierce this tissue so blood circulation is absent in epithelium. Hence cells depend for their nutrients on underlying connective tissue.
112 STRUCTURAL ORGANISATION IN ANIMALS Jr|11th|I PUC NEET|BIOLOGY:VOL-II 7. Basement membrane : Between epithelium and connective tissue, a thin non living acellular basement membrane is present which is highly permeable. Basement membrane consist of 2 layers. a) Basal lamina: Towards epithelium and it is made up of glycoprotein, which is secreted by epithelium cells. b) Fibrous lamina : Towards connective tissue, in which collagen and reticular fibres are suspended in mucopolysaccharide which is matrix of connective tissue. Mucopolysaccharide is present in the form of Hyaluronic acid. So basement membrane is secreted by both epithelium and connective tissue. 8. Intercellular junction : To provide both structural and functional link between its individual cell epithelial cells modify to form following structures (Intercellular Junctions): i) Interdigitation - Finger like processes of plasma membrane which enter into cytoplasm of adjacent cell. These structures are mainly found in transitional epithelium. ii) Adhering / Desmosomes - This type of Macula Adherens) Junction consists of disc - like protein plate with intermediate fibre known as tonofibrils composed of keratin like protein. These filaments are deeply situated in the cytoplasm of respective cell. These structures provide mechanical support to stratified epithelium or performing cementing to keep neighbouring cell together, e.g. Stratified epithelium iii) Tight Junction - At some places plasma membrane of adjacent cells become fused to form tight junction to stop substances from leaking across a tissue. These structures are mostly found in columnar epithelium. iv) Gap Junction - Faciliate the cells to communicate with each other by connecting cytoplasm of adjoining cells for rapid transfer of ions, small molecules and sometimes big molecules. Adjacent plasma membranes Gap between cells Plaque transmembrane glycoproteins Tono filaments Desmosome Adjacent plasma membranes Tight junction Gap between cells Transmembrane proteins
STRUCTURAL ORGANISATION IN ANIMALS 113 Jr|11th|I PUC NEET|BIOLOGY:VOL-II Gap between cells Gap junction Adjacent plasma membranes Connexons 9. Functional modification of plasma membrane of free end : i) Microvilli 1. These are minute process which are non motile, non contractile. They increase surface area by more than 20 times. 2. They help in absorption, secretion and excretion. These are present in the wall of Intestine, Gall bladder, Proximal convoluted tubule etc. ii) Cilia or Kinocilia 1. Long cylindrical process, those are motile and contractile. 2. These helps in movement of particles or mucus in a specific direction. Mainly present in the inner surface of hollow organs. 3. These are found in E.g Fallopian tube. Uterus (Cilia is only present in patches). Trachea and Bronchioles Ependymal epithelium : Inner lining of ventricles of brain and central canal of spinal cord. Function of cilia is to conduct substances in CSF.) iii) Steriocilia i) Long process those are non motile and non contractile. ii)Its plasma membrane is thick and rigid. iii) They increase surface area and found in Eg. Epididymis ; Vasa deferens Origin of Epithelium Tissue It is the only tissue which originated from all the three primordial germinal layers, Eg. i) Ectodermal - Epidermis (stratified squamous Epithelium) ii) Mesodermal - Mesothelium (simple squamous Epithelium) iii) Endodermal -Inner living of gut (simple columnar Epithelium) 1. Epithelial tissue origined from 1) Ectoderm 2) Endoderm 3) Mesoderm 4) All of these 2. Basement membrane is composed of 1) Hyaluronic Acid + glycoproteins 2) Only mucopolysacharides 3) Endodermal cells 4) Epidermal cells 3. Stereocilia present in 1) Epididymis 2) Seminal vesicle 3) Ureter 4) Kidney 4. Lining of brain ventricle & central canal of spinal cord is lined by
114 STRUCTURAL ORGANISATION IN ANIMALS Jr|11th|I PUC NEET|BIOLOGY:VOL-II 1) Ependyma epithelium 2) Endothelium 3) Mesothelium 4) Neurosensory 5. Desmosomes 1) Connect the Epithelial cells 2) are types of lysosomes 3) are granules of muscle fibres 4) Found in Bone 6. Ciliated Epithelium found in 1) Oviduct 2) Trachea 3) Brain ventricles 4) All of these 7. Gap junctions 1) help to stop substances from leaking across a tissue 2) perform cementing to keep neighbouring cells together 3) provide stretchability to the epithelium 4) facilitate the cells to communicate with each other by connecting the cytoplasm of adjoining cells. 8. Condition necessary for the formation of organ system 1) presence of all four basic type of tissues 2) Chemical interaction 3) Physical interaction 4) All of these 9. Tissue which provide support to the body is 1) Epithelial tissue 2) Connective tissue 3) Muscular tissue 4) Nervous tissue 10. Intercellular junction which helps in exchange of substances is 1) Tight junction 2) Gap junction 3) Interdigitation 4) Desmosome 1) 4 2) 1 3) 1 4) 1 5) 1 6) 4 7) 4 8) 1 9) 2 10) 2 Classification of Epithelium tissue Types of Epithelium Tissue One the basis of number of cell layers Simple epithelium - Composed of single layer of cells - Functions as lining for body cavities, ducts and tubes On the basis of shape/structural modifications of cells 1) Simple Squamous 2) Simple cuboidal 3) Simple Columnar 4) Pseudostratified Compound epithelium - Consists of 2 or more cell layers - It has protective function as it does in out skin