TISSUES I I. CLASSIFICATION OF TISSUESA. Histology : microscopic study of tissuesB. 4 kinds: Epithelia, connective, muscle, and nervous II. EPITHELIAA. Characteristics of Epithelia : covers body/organ surfaces, lines body cavities and forms glands1. very cellular 2. has a free surface (apical surface) 3. bound to underlying tissue by a basement membrane 4. avascular: don’t have blood vessels B. Classification1. Classified by LAYERS:a. Simple Epithelium – one layer thickb. Stratified Epi . – many layers thick 2. Classified by cell SHAPE:a. Squamous – flattened cells b. Cuboidal – cube-shaped cells (height and width are equal)c. Columnar – rectangular-shaped cells (cell is taller than it is wide) III. TYPES OF SIMPLE EPITHELIAA. Simple Squamous Epithelium1. One layer of flattened cells2. Location: lines lumen (cavity) of blood vessels, tiny air sacsof lungs, covers organs, and lines body cavities3. Function: rapid diffusion and filtration B. Simple Cuboidal Epithelium1. One layer of cube-shaped cells2. Location: lines ducts and tubules (e.g., salivary glands and kidneys)3. Function: secretion and absorption C. Simple Columnar Epithelium1. One layer of tall, rectangular-shaped cells. May have microvilli, goblet cells, or cilia.2. Location: lines most of GI (gastrointestinal tract)3. Function: secretion and absorption D. Pseudostratified Columnar Epithelium1. One layer of columnar or irregularly shaped (tall and short) cells. Some kinds have cilia (pseudostratified CILIATED columnar epithelium) and goblet cells2. Location: lines trachea and bronchi3. Function: protection and secretion (secretion here is about mucus) IV. TYPES OF STRATIFIED EPITHELIAA. Stratified Squamous Epithelium: Upper layers of cells are flattened, lower layers appear cuboidal. Deepest layers highly mitotic. Two kinds:1. Keratinized: contains keratin, superficial layers consist of dead cellsa. Location: epidermisb. Function: protection2. Nonkeratinized: superficial cells are alive and kept moista. Location: oral cavity, pharynx, vagina, and the lower part of the anal canalb. Function: protection B. Transitional Epithelium: some cells are binucleated. Surface cellsmay be dome-shaped or flattened.a. Location: found in most of the urinary tract b. Function: withstands distention (stretching) and relaxing V. GLANDULAR EPITHELIA: Specialized epithelial tissues that have excretory functionsA. Exocrine Glands formed from epithelial tissues - they secrete theirmaterials onto a free surface1. Unicellular: Goblet cells.a. Location: respiratory and digestive systems b. Function: secretes mucus2. Multicellular: secrete materials through a duct to a free surfacea. merocrine glands: secretes a watery fluid through the cell membrane. Example-salivary glandsb. apocrine glands: top part of the cell is pinched off, it becomes the secretion. Example - mammary glandsc. holocrine glands: entire cell is released and it ruptures and dies. Example- sebaceous (oil) glands Which of the following epithelial tissues allows for rapid filtration and diffusion?a. Simple squamous ******b. Simple columnarc. Transitionald. Simple cuboidale. Nonkeratinized stratified
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