Epithelium Study Guide PDF

**[Epithelium ]** **[Learning outcomes ]** **1. Classify Epithelial Tissues:** Epithelial tissues are classified based on: - **Number of cell layers**: - **Simple Epithelium**: One layer of cells. - **Stratified Epithelium**: Multiple layers of cells. - **Pseudostratified...

**[Epithelium ]** **[Learning outcomes ]** **1. Classify Epithelial Tissues:** Epithelial tissues are classified based on: - **Number of cell layers**: - **Simple Epithelium**: One layer of cells. - **Stratified Epithelium**: Multiple layers of cells. - **Pseudostratified Epithelium**: Appears layered due to varying cell heights but is actually a single layer with all cells in contact with the basement membrane. - **Cell shape**: - **Squamous**: Flat, thin cells. - **Cuboidal**: Cube-shaped cells. - **Columnar**: Taller than they are wide, resembling columns. - **Transitional**: Specialized for stretching, found in organs like the bladder. **2. Describe the Characteristics of Epithelial Tissue:** Epithelial tissues have several key characteristics: - **Cellularity**: Epithelial tissue is made up of tightly packed cells with minimal extracellular material. - **Polarity**: Epithelial cells have an apical (top) surface exposed to the body's exterior or cavity and a basal (bottom) surface attached to the underlying tissue. - **Avascular**: Epithelial tissues do not have blood vessels and rely on diffusion from nearby tissues for nutrients. - **Innervated**: They have a good nerve supply and are involved in sensation. - **Regenerative**: These tissues have a high capacity for regeneration, frequently replacing damaged or dead cells. **3. Name the Various Types and Categories of Epithelial Tissue and Identify Where in the Body They are Found:** **Simple Epithelium:** 1. **Simple Squamous Epithelium**: - **Structure**: Single layer of flat cells. - **Function**: Facilitates diffusion and filtration. - **Location**: Found in alveoli of lungs, blood vessels (endothelium), and glomeruli of kidneys. 2. **Simple Cuboidal Epithelium**: - **Structure**: Single layer of cube-shaped cells. - **Function**: Secretion and absorption. - **Location**: Found in kidney tubules, glandular ducts, and the surface of ovaries. 3. **Simple Columnar Epithelium**: - **Structure**: Single layer of tall, column-like cells. - **Function**: Absorption and secretion of mucus and enzymes. - **Location**: Found in the digestive tract (stomach, intestines), gallbladder, and certain glands. **Stratified Epithelium:** 1. **Stratified Squamous Epithelium**: - **Structure**: Multiple layers of cells with flattened cells at the surface. - **Function**: Protection against abrasion and pathogens. - **Location**: Found in the skin (keratinized), mouth, esophagus, and vagina (non-keratinized). 2. **Stratified Cuboidal Epithelium**: - **Structure**: Multiple layers of cube-shaped cells. - **Function**: Provides protection. - **Location**: Found in sweat glands, mammary glands, and salivary glands. 3. **Stratified Columnar Epithelium**: - **Structure**: Several layers with column-shaped cells at the surface. - **Function**: Protection and secretion. - **Location**: Found in parts of the male urethra and large ducts of some glands. **Transitional Epithelium:** - **Structure**: Multiple layers of cells that can stretch and change shape. - **Function**: Allows for expansion and contraction. - **Location**: Found in the urinary bladder and ureters. **Additional Functions of Epithelial Tissues:** - **Secretion**: Epithelial tissues in glands secrete substances like enzymes, hormones, and mucus (e.g., goblet cells in the respiratory and digestive tracts). - **Absorption**: Certain epithelial tissues, especially in the intestines, absorb nutrients from the environment. - **Protection**: Epithelial layers protect underlying tissues from mechanical injury, pathogens, and dehydration (e.g., skin). - **Transcellular Transport**: Movement of substances across epithelial cells, such as ions or nutrients (e.g., in the kidneys and intestines). - **Sensation**: Nerve endings in epithelial tissues are involved in sensory functions like taste, touch, smell, and sight. - **Movement**: Some epithelial cells have cilia that aid in moving substances along surfaces (e.g., respiratory tract cilia moving mucus).