Epithelium DTH24.pdf
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Epithelium & Membranes Julie Watson GDC Learning Outcomes 1.1.1 1.1.3 1.1.5 9.1 9.2 2 Learning Outcomes: Students will be able to: Classify Epithelial tissues Describe the characteristics of Epithelial tissue Name the various types and categories of Epithelial...
Epithelium & Membranes Julie Watson GDC Learning Outcomes 1.1.1 1.1.3 1.1.5 9.1 9.2 2 Learning Outcomes: Students will be able to: Classify Epithelial tissues Describe the characteristics of Epithelial tissue Name the various types and categories of Epithelial tissue and identify where in the body they would be found 3 Activity: with the information you will have gained; Write down the various classifications of Epithelium & how they differ. For each, give 3 examples of where in the body you would find them Whilst doing, this recall the following: Does it have one layer, or two or more layers? What shape do the cells have? Are there any specialisations? * Return work to Mrs Watson to be reviewed. Epithelial Tissue – Epi (on or upon) Epithelial tissue covers the whole surface of the body It is made up of cells closely packed and arranged in one or more layers This tissue is specialised to form the covering or lining of all internal and external body surfaces 5 The epithelial tissue is one of the four main types of tissue structures of the human body, along with muscle tissue, nerve tissue, and connective tissue. Tissues are cellular organizations with similar specializations. Epithelia are formed of cells that line the cavities in the body and also cover flat surfaces. Of the four major tissue types found in the human body epithelial cells are by far the most prolific. 6 Muscle Tissue 7 Connective Tissue 8 Nerve Tissue 9 How Do Epithelial Cells Differ From Other Cells? Avascular Capillaries do not reside within epithelial cell tissues Sensory Endings of neurons are present within epithelial cell tissues Perceive external stimulus (i.e. tactile) Gliding surface layer Epithelial cells slough off and glide in order to replace dead cells This function allows epithelial cells to maintain a closed barrier to the external environment Transitional Multi-layered epithelia are able to stretch Allows the urinary bladder to distended or contracted without compromising it Tight barrier Desmosomes, hemi desmosomes, tight junctions Epithelium is held together more tightly than other cells Aids cells in withstanding mechanical stress Different from endothelial cells Endothelial cells line the insides of structures that aren’t exposed to the “outside” Ex. Blood vessels Cel l cartoons Functions of Epithelium Secretion Sensation Absorption Transport Protection Secretion & Lubrication Selective Absorption Secretion is the movement of The process of a liquid, gas or other material from one point to another. substance being taken in. such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism freepic Protection Transcellular Transport Cover the inner and outer linings of Movement of substances across the bodies cavities and organs. the cell membrane – either in to or out of the cell https://www.youtube.com/watch? v=ufCiGz75DAk Dreamstime.com Sensation Movement Nerve endings provide signals for Some epithelial cells have cilia sensory sensations such as taste, which aid in moving substances. sight and smell. These work by a sweeping motion. In the nose, the sensory transducers are olfactory sensory neurons; in the ear, auditory hair cells; and in the eye, photoreceptors. New York post Science photo library Characteristics of Epithelium The most cellular tissue in the body Forms semi- permeable membranes Avascular – without blood vessels nutrients diffuse in from underlying connective tissue Good nerve supply Cells are tightly packed together Rapid cell division 17 Characteristics Cellularity Polarity Supported by connective tissue Avascular Regenerative 18 Basement Membrane Types & Categories of Epithelium Simple Squamous Stratified Cuboidal Transitional Columnar Pseudostratified Youtube.com/watch?v=18FKDs_x_hU Epithelium song by Study Songz https://www.youtube.com/watch?v=reoEVXvoUmI Types and Categories of Epithelium Classification of Epithelium Simple Epithelium Simple Squamous Epithelium These consist of a single layer of flattened cells. The thinness of these cells facilitates the transfer of materials across the epithelium. 24 Bio.davidson.edu Simple Cuboidal Epithelium These consist of a single layer of cuboidal cells This epithelium is often associated with absorption, secretion or excretion of waste material. 26 Simple Cuboidal Epithelium 27 Simple Columnar Epithelium These consist of a single layer of cells that are taller than they are wide This epithelium is often associated with absorption or secretion. 28 Simple Columnar Epithelium Sites of Simple Columnar Epithelium Bio.davidson.edu Pseudostratified (Pseudo – fake/false) Columnar Epithelium These appear to be stratified because of the nuclei of the epithelial cells are at different levels All cells are in contact with the basement membrane, but not all cells reach the lumen 31 Pseudostratified Columnar Epithelium 32 Stratified Epithelium Stratified Squamous Epithelium These have multiple layers of cells They become flattened as they move from the basal layer to the apical layer They provide protection from abrasion Can be Keratinised or non- Keratinised 34 Non Keratinised V Keratinised Keratinised Stratified Squamous Epithelium 36 Stratified Cuboidal Epithelium These have multiple layers of cells The outermost layer being cuboidal Limited distribution 37 http://www.kumc.edu/instruction/medicine/anatomy/histoweb/epithel/small/Epth017s.JPG Stratified Columnar Epithelium Multiple layers Primary function is protection Topmost layer is made up of columnar epithelial cells 39 http://www.cytochemistry.net/microanatomy/epithelia/salivary8.jpg Transitional Epithelium These have multiple layers of cells The outermost layer has much larger cells, which are pear/dome shaped These cells change shape during contraction Allows for stretching 41 Transitional Epithelium Break Time I would now suggest you have a 10 minute break – then join again to have a look at Membranes. www.zmescience.com Membranes Membranes Membranes are sheets of tissue composed of cells They cover or line internal structures or cavities The main membranes are: Mucous Serous Synovial Cutaneous Mucous Membrane This is an epithelial membrane containing Mucous is produced from the epithelial mucous cells exocrine glands It lines the body cavities that are open to The fluid consists of : the external environment 95% water 05-5% mucins It has a protective function 1% inorganic salts 05-1% proteins It is rich with mucous glands that secrete Trace - lipids and mucopolysaccharides a gel like fluid to help keep the membranes moist Mucous Membrane 47 Serous Membrane Lines the body cavities that are not open to the external environment It is an epithelial membrane composed of mesodermal derived epithelium Composed of two layers: Parietal – outer layer Visceral – inner layer Serous fluid lubricates 48 Serous Membrane Synovial Membrane This lines the cavity of a freely moveable joint Fibroblasts release hyaluronan into the joint cavity Hyaluronan traps available water to form the synovial fluid Nourishes cartilage 50 Synovial Membrane - Knee Joint Cutaneous Membrane It is a stratified squamous epithelial membrane Rests on top of connective tissue Covered with dead keratinized cells that protect the body from pathogens Also known as skin 52 Cutaneous Membrane Reflective Learning Why is it important within dentistry we need to have knowledge on the epithelium? Why is it important within dentistry that we need to have knowledge on the various membranes? What could “go wrong” with these structures. What could affect them. Would you be able to recognise changes. Would you be able to recognise normality. 54 Further Reading https://bio.davidson.edu/people/kabernd/BerndCV/Lab/EpithelialInfoWeb/ www.histologyguide.com>slidebox https://www.kenhub.com/en/library/anatomy/overview-and-types-of-epithelial- tissue https://biologydictionary.net/simple-squamous-epithelium/ https://www.biologyonline.com/dictionary/squamous-epithelium https://study.com/academy/lesson/simple-cuboidal-epithelium-location-structure- function.html Thank you for your attention 56
