Epithelial Tissue PDF

Endothelium = simple squamous cells for blood for places where diffusion happens quickly, or **Simple Squamous**: Flat cells, (e.g. alveoli) vessels...

Endothelium = simple squamous cells for blood for places where diffusion happens quickly, or **Simple Squamous**: Flat cells, (e.g. alveoli) vessels where a smooth lining is needed diffusion Etymology: epi- (upon), thélé (nipple) So the tissue that cover surfaces in places like glands where cells need to both **Simple Cuboidal**: Cube-shaped cells, (e.g. 1. Epithelium tissues that cover the surfaces of organs and Simple Epithelium Lining Epithelia absorb and secrete things kidneys) the body Types: in places like the stomach and intestines where form glands that secrete substances **Simple Columnar**: Tall, rectangular cells (e.g. Glandular Epithelia the cells need to absorb nutrients or secrete (eg:hormones or enzymes) intestines) mucus and enzymes **Stratified Squamous**: Multiple layers, flat top in places that experience wear and tear (mouth) cells (e.g. skin) Ectoderm, outer layer (e.g. skin) Stratified Epithelium 9. Types of Epithelium **Stratified Cuboidal & Columnar**: Multiple 2. Origins of Epithelia Mesoderm, middle layer (e.g. endothelium) layers, rare, found in glands Endoderm, inner layer (e.g. intestine) in the respiratory system, where it’s often Single layer but looks layered because the nuclei Pseudostratified Epithelium ciliated to help move mucus. are at different levels Changes shape: Squamous (full bladder), Lamina rara Rounded (empty bladder) Basal Lamina (closest) Transitional Epithelium (Urothelium) Lamina densa umbrella cells: change shape and have special can stretch and change shape depending on 3. Basement Membrane 2 Layers: Found in the bladder plaques that protect them from the urine whether the bladder is full or empty Reticular Lamina (below) Closely packed cells Epithelial Tissue Tight junctions (Zonula occludens) prevents anything from leaking between them Little intercellular space no (extracellular Help stick the cells together by connecting their material) Adherens junctions (Zonula adherens) cytoskeletons 8. Characteristics of Epithelial Tissue Always Rest on basement membrane 4. Cell Junctions Desmosomes Act like strong rivets that hold cells together Avascular (no blood vessels) They get nutrients Small channels that allow cells to communicate from nearby tissues Gap junctions by passing signals Anchor the cells to the basement membrane Hemidesmosomes below Can move: beat in rhythm to move things across the surface of cells (clearing mucus in the respiratory tract) increase the surface area, helpful for absorption built from Axoneme: a 9+2 microtubule arrangement 7. Cilia and Flagella (Apical Surface) 5. Microvilli (Apical Surface) Structure: Supported by Actin filaments Flagella longer Covered of Glycocalyx (protection) Similar to microvili Long projections (they don't move) 6. Stereocilia (Apical Surface) Found in male reproductive system