CHAPTER 1 STRUCTURAL ORGANISATION IN ANIMALS INTRODUCTION A. Epithelium Tissue Tissue : A group of cells in which cells are similar in I. Characteristics of epithelial tissue structure , function and origin is called tissue. 1. During embryonic development epithelium orginates first. Group of similar cells along with intercellular 2. Power of regeneration is present in this tissue while substance perform a specific function such power of regeneration is absent or least power is organisation is called tissue. But in a tissue, cells found in nervous tissue . may be dissimilar in structure and function but they are always similar in origin. 3. This tissue faces either a body fluid or outside environment and thus provide a covering or a lining. Organ : Tissues are organised in specific proportion and pattern to form organ. 4. Word epithelium is composed of two words. Organ system: When two or more organ perform A tissue which grows upon another tissue is called common function by their physical &/or chemical Epithelium. 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. 1. Types of Animal Tissue 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. Fig. 1.1 4. Nervous tissue - To generate and conduct nerve Epi - Upon Thelia - growth 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 CORPORATE OFFICE : Motion Education Pvt. Ltd., 394 - Rajeev Gandhi Nagar, Kota 6 | Theory and Exercise Book 5. It always rest upon underlaying connective tissue. (ii) Adhering / Desmosomes - This type of Epithelium is the only tissue in which cells are always (Macula Adherens) Junction consists of arranged in uniform layer. disc - like protein plate with intermediate Epithelium cells are compactly packed with little fibre known as tonofibrils composed of intercellular matrix. keratin like protein. These filaments are 6. Due to absence of intercellular spaces blood vessels, deeply situated in the cytoplasm of lymph vessels & capillaries are unable to pierce respective cell. These structures provide this tissue so blood circulation is absent in epithelium. mechanical support to stratified Hence cells depend for their nutrients on underlying epithelium or performing cementing to connective tissue. keep neighbouring cell together. e.g. 7. Basement membrane : Between epithelium and Stratified epithelium connective tissue, a thin non living acellular basement (iii) Tight Junction - At some places plasma membrane is present which is highly permeable. membrane of adjacent cells become fused Basement membrane consist of 2 layers. to form tight junction to stop substances (a) Basal lamina : Towards epithelium and it from leaking across a tissue. These is made up of glycoprotein, which is structures are mostly found in columnar secreted by epithelium cells. epithelium. (b) Fibrous lamina : Towards connective (iv) Gap Junction - Facillate the cells to tissue, in which collagen and reticular fibres communicate with each other by are suspended in mucopolysaccharide which connecting cytoplasm of adjoining cells for is matrix of connective tissue. rapid transfer of ions, small molecules and Mucopolysaccharide is present in the form sometimes big molecules. of Hyaluronic acid. Fig. 1.2 So basement membrane is secreted by both epithelium III. Modification of plasma membrane of and connective tissue. epithelial tissue : II. Cell Junction: To provide both structural and (i) Microvilli functional link between its individual cell epithelial 1. These are minute process which are non cells modify to form following structures motile, non contractile. They increase (Intercellular Junctions) : surface area by more than 20 times. (i) Interdigitation - Finger like processes of 2. They help in absorption, secretion and plasma membrane which enter into excretion. cytoplasm of adjacent cell. These These are present in the wall of Intestine, structures are mainly found in transitional Gall bladder, Proximal convoluted epithelium. tubule etc. CORPORATE OFFICE : Motion Education Pvt. Ltd., 394 - Rajeev Gandhi Nagar, Kota Structural Organisation in Animals | 7 (ii) Cilia or Kinocilia 4. Lining of brain ventricle & central canal of spinal 1. Long cylindrical process, those are motile cord is lined by :- and contractile. (A) Ependyma epithelium 2. These helps in movement of particles or (B) Endothelium mucus in a specific direction. Mainly (C) Mesothelium present in the inner surface of hollow (D) Neurosensory organs. 5. Desmosomes : 3. These are found in e.g. - Fallopian tube, Uterus (Cilia is only (A) Connect the Epithelial cells present in patches). (B) are types of lysosomes - Trachea and Bronchioles (C) are granules of muscle fibres - Ependymal epithelium: (Inner lining of (D) Found in Bone ventricles of brain and central canal of 6. Ciliated Epithelium found in : spinal cord. Function of cilia is to (A) Oviduct (B) Trachea conduct substances in CSF) (C) Brain ventricles (D) All of these (iii) Steriocilia 7. Gap junctions : (i) Long process those are non motile and non (A) help to stop substances from leaking across a contractile. tissue. (ii) Its plasma membrane is thick and rigid. (B) perform cementing to keep neighbouring cells (iii) They increase surface area and found in together eg. - Epididymis - Vasa deferens (C) provide stretchability to the epithelium Origin of Epithelium Tissue (D) facilitate the cells to communicate with each It is the only tissue which originated from all the other by connecting the cytoplasm of adjoining cells three primordial germinal layers. 8. Condition necessary for the formation of organ eg. (i) Ectodermal- Epidermis (stratified system: squamous Epithelium) (A) presence of all four basic type of tissues (ii) Mesodermal - Mesothelium (simple (B) Chemical interaction squamous Epithelium) (C) Physical interaction (iii) Endodermal - Inner living of gut (simple (D) All of these columnar Epithelium) 9. Tissue which provide support to the body is : CHECK YOUR CONCEPTS-1 (A) Epithelial tissue (B) Connective tissue (C) Muscular tissue (D) Nervous tissue 1. Epithelial tissue origined from :- 10. Intercellular junction which helps in exchange of (A) Ectoderm (B) Endoderm substances is : (C) Mesoderm (D) All of these (A) Tight junction (B) Gap junction 2. Basement membrane is composed of :- (A) Hyaluronic Acid + glycoproteins (C) Interdigitation (D) Desmosome (B) Only mucopolysacharides ANSWERKEY (C) Endodermal cells (D) Epidermal cells 1. D 2. A 3. A 4. A 3. Stereocilia present in :- 5. A 6. D 7. D 8. A (A) Epididymis (B) Seminal vesicle 9. B 10. B (C) Ureter (D) Kidney : [email protected], url : www.motion.ac.in, : 1800-212-179999, 8003899588 8 | Theory and Exercise Book IV. Types of Epithelium Tissue | On the basis of number of cell layers Simple epithelial Tissue Compound epithelial Tissue - Composed of single layer of cells - Consists of 2 or more cell layers - Functions as lining for body cavities, - It has protective function as it ducts and tubes does in our skin On the bssis of shape / structural modifications of cells (1) Simple Squamous (2) Simple Cuboidal (3) Simple Columnar (4) Pseudostratified (a) Simple Epithelium Tissue 1. Simple Squamous epithelium (i) Single layer of flat, scale like cell with irregular boundries. (ii) It is also called pavement epithelium due to its tile like appearance. Fig. 1.3 (iii) It is also called Tesselated to its wavy epithelium due appearance. Functions: Fig. 1.4 eg. It is found in the lining of : - Bowman's capsule (podocyte) CORPORATE OFFICE : Motion Education Pvt. Ltd., 394 - Rajeev Gandhi Nagar, Kota Structural Organisation in Animals | 9 - Tubular part of Nephrons Modifications of simple cuboidal epithelium (i) Brush bordered cuboidal epithelium : When microvilli are present on free end of cuboidal cells then it is called as brush bordered cuboidal epithelium. It is found in PCT of nephron. (ii) Ciliated cuboidal epithelium : When cilia present on free end of cuboidal cells then it is called as ciliated cuboidal epithelium. It Fig. 1.5 is found in neck of the nephron and in - Alveoli of lungs (Pneumocytes) collecting duct. 3. Simple columnar Epithelium (i) Cells are pillar like in shape. (Tall and Slender) (ii) Elongated nucleus is present at the base of cell. Function: It helps in absorption and secretion. eg. Bile Duct, Liver Fig. 1.6 Modifications of Simple Columnar epithelium - Mesothelium - Covering of coelom is called (a) Brush Bordered Columnar epithelium : When as mesothelium.(Tesselated). (Visceral & microvilli are present on free end of columnar Parietal peritonium, Visceral and parietal epithelium. pleura, Visceral and Parietal, (pericardium). e.g. Gall bladder - Endothelium - Inner lining of blood vessels (b) Glandular columnar epithelium : Unicellular and lymph vessels. (Tesselated) mucous secreting goblet cells are also present in - Inner lining of heart wall (Tesselated). between columnar cells. 2. Simple Cuboidal Epithelium eg.