Epithelial Tissue PDF

TISSUES  A collection or groups of similar cells performing a definite function. 4 fundamental tissues in the animal body: 1. Epithelial tissue – forms the covering or lining of body surfaces 2. Connective tissue – forming the principal supporting tissue 3....

TISSUES  A collection or groups of similar cells performing a definite function. 4 fundamental tissues in the animal body: 1. Epithelial tissue – forms the covering or lining of body surfaces 2. Connective tissue – forming the principal supporting tissue 3. Muscular tissue – responsible for body movements 4. Nervous tissue – specialized tissue for the transmission of stimuli EPITHELIAL TISSUE (EPITHELIUM)  Made up of cells that are compactly arranged and rested on a basement membrane.  Lines all free body surfaces, internal and external including body cavities.  Avascular and capable to regenerate Functions: 1. Protection – skin 2. Secretion – salivary glands 3. Absorption – small intestines 4. Excretion – sweat glands 5. Sensation – taste buds 6. Reproduction – ovary and testes Types of epithelium: 1. Covering/ lining epithelium – found in sheets that cover body structures (outer layer of skin) or line body spaces (lining of the stomach). 2. Glandular epithelium – forms the functional portions of the exocrine and endocrine glands. Classifications of epithelial tissue (categorized by its structure) I. According to the # of cell layers 1. Simple – made up of 1 cell layer 2. Stratified – made up of more than 2 layers of cell 3. Pseudostratified – made up of only 1 layer of cell, but with different height 4. Transitional – simple – stratified II. According to the shape of the cell 1. Squamous – flat, scale-like cells with serrated border 2. Cuboidal – cells with an equal height and width 3. Columnar – tall, narrow, prismatic cells, the height is greater than width a. Simple b. Ciliated III. According to functions 1. Protective – guards the body from external injury and infections 2. Sensory – for reception of stimuli 3. Germinal – for production of sex cells 4. Glandular – secretes products for body use 1 SIMPLE EPITHELIAL TISSUE  A mere single layer cell thick  Type of epithelium located where diffusion, filtration, and secretion are principal functions 1. Simple squamous epithelium  Composed of flat, irregularly shaped cells that are tightly bound together  Lines the air sacs of lungs, kidneys(where filtration occurs), blood vessels, body cavities and coverings of viscera 2. Simple cuboidal epithelium  Composed of tightly-fitted cube shaped cells  Found lining small ducts and tubules that have excretory, secretory and absorptive functions  Lines the ovaries, kidneys, ducts of salivary glands and pancreas 3. Simple columnar epithelium  Lines the inside walls of stomach and small intestine  The tissue consists of “goblet cells” (secretes lubricative and protective mucus along the free surfaces of the tissue). 4. Simple ciliated columnar epithelium  Characterized by the presence of “cilia” along the free surface  Lines the female uterine tubes to move the egg cell into uterus 5. Pseudostratified ciliated columnar epithelium  Also known as the “respiratory epithelium”  Consists of numerous goblet cells  Lines the trachea and bronchial tubes, urinary and reproductive tracts in male 2 STRATIFIED EPITHELIAL TISSUE  Consists of 2 or more layers of cells, the cell divides rapidly  Too thick to absorb or secrete  It has a protective function 1. Stratified squamous epithelium  Forming the skin layer, lining the openings of the body – mouth, anus, vagina  Forms the 1st line of defense against the entry of disease causing organisms a. Keratinized stratified squamous epithelium - Contains “keratin”, it makes the epidermis of the skin somewhat waterproof and protects it from bacterial invasion - The outer layers of the skin are dead, but glandular secretions keep them soft. b. Non-keratinized stratified squamous epithelium - Also known as the “mucosa”, which is well adapted to withstand moderate abrasion but not fluid loss - The cells on exposed surface are alive and always moistened - Lines the mouth, throat, nasal cavity, vagina and anal canal. 2. Stratified cuboidal epithelium  It has a limited distribution in the body  Lines the large ducts of sweat glands, salivary glands and pancreas 3. Transitional epithelium  Similar to non keratinized stratified squamous epithelium  Transition between simple and stratified variety  Restricted only to urinary system that lines hollow organs capable of distention – urinary bladder, ureters altor 3