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18 epithelium poonam
This document provides an overview of epithelium, including its development, classification, histological appearance, domains, functions, and types of glands. It begins with an introduction and outline, then discusses how epithelium develops from the three germ layers. It describes the four basic types of epithelial tissues and how they are classified based on cell layers and shape. The document outlines the characteristics, domains, junctions, and basement membrane of epithelium. It also covers the classification, structure, functions and locations of simple and stratified epithelia. Finally, it discusses exocrine and endocrine glands as well as the different modes of secretion.
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Introduction to epithelium presentation and overview of topics to be covered.
Introduction to the four basic types of tissues essential for understanding epithelium.
Development stages of epithelium including ectoderm, mesoderm, and endoderm derivatives.
Key features of epithelium including avascularity, cell junctions, and regeneration abilities.
Two main classification types based on layers (simple vs stratified) and cell shape.
Structure, function, and locations of simple squamous epithelium including diffusion sites.
Details on structure and function with locations in glands and kidneys for transport.
Structure, function, and types of columnar epithelium including specializations like goblet cells.
Structure and functions of keratinized and non-keratinized stratified squamous epithelium.
Locations and structural characteristics of stratified cuboidal and columnar epithelium.
Structure and functions, including goblet cells, with locations in respiratory and reproductive tracts.
Unique structure allowing stretching and impermeability, primarily in urinary structures.
Modifications of the apical domain such as microvilli, stereocilia, and cilia types.
Characterization and classification of lateral domains, including CAMs and junctional types.
Details about the basement membrane's structure and functions related to epithelium.
Differences between exocrine and endocrine glands, their classification, and secretion modes.
Wrap-up and discussion of epithelial tissue significance and applications.
18 epithelium poonam
- 1. EPITHELIUM CAPT DR POONAMSINGH DEPT OF ANATOMY
- 2. SEQUENCE OF PPT 1. 2. 3. 4. 5. 6. 7. 8. INTRODUCTION DEVELOPMENT CLASSIFICATION HISTOLOGICALAPPEARANCE APICAL DOMAIN & ITS MODIFICATIONS LATERAL DOMAIN & ITS SPECIALIZATIONS BASAL DOMAIN GLANDS & ITS TYPES
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- 5. 5 – 6DAY
- 6. 6th DAY Implantation ofthe Blastocyst
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- 10. DEVELOPMENT OF EPITHELIUM 1.Ectoderm:- skin, hair follicles, mammary glands, cornea, conjunctiva, some parts of mouth & anal canal. 2. Endoderm:- GIT ( except part of mouth &anal canal), resp tract, glands. 3. Mesoderm:-body cavities (Mesothelium), endothelium.
- 11. EPITHELIUM • Avascular tissuecomposed of cells, 1. Covers the exterior of body surfaces 2. Lines internal body cavities & body tubes 3. Forms parenchyma of glands their ducts 4. Specialized epi cells fxn as receptors for the special senses. • • Nourished by connective tissue Regenerate & repair quickly
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- 13. Characteristics 1. Cell junctions:-specific cell-to-cell adhesion molecules. 2. Exhibit functional & morphological polarity a) Apical domain b) lateral domain c) basal domain 3. Rest on basement membrane - anchors epithelial cells to underlying connective tissue
- 14. CLASSIFICATION • Based on2 factors:1. Simple / Unilaminar 2. Compound / Stratified / Multilaminar
- 15. Based on theshape of surface cells:- W>H W=H H>W
- 16. EPITHELIUM UNILAMINAR/ SIMPLE MULTILAMINAR/ SRTATIFIED SQUAMOUS STRATIFIEDSQUAMOUS CUBOIDAL COLUMNAR KERATINIZED WITHOUT SPECIALIZATION NON-KERATINIZED WITH SPECIALIZATIONS STRATIFIED CUBOIDAL MICROVILLI STRATIFIED COLUMNAR PSEUDOSTRATIFIED NONCILIATED SENSORY CELLS GLANDULAR CELLS CILIATED MYOEPITHELIAL CILIA CILIA TRANSITIONAL STEREOCILIA
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- 18. Simple Squamous Epithelium •Structure – Single Layer of flattened cells • Function – Diffusion and filtration – Not effective protection – single layer of cells. • Location – Endothelium – Mesothelium – Lung alveolus
- 19. Simple Cuboidal Epithelium •Structure – Single layer of cube shaped cells • Function – Secretion and transportation in glands, filtration in kidneys • Location – Glands and ducts (pancreas & salivary), kidney tubules, germinal layer ofovaries
- 20. Simple Columnar Epithelium •Structure – Elongated layer of cells with nuclei at same level • Function -- Absorption, Protection & Secretion • Location -- GIT
- 21. Simple Columnar Epitheliumwith specializations 1. Ciliated columnar epithelium:-cell surface bears cilia. -lines the resp tract, uterus, uterine tubes. 2. Simple columnar epithelium with microvilli:-visible only under EM. -striated border:- small intestine - brush border:- GB - increase surface area & absorption rate
- 22. Simple Columnar Epitheliumwith specializations 3. With secretory function: Goblet cells - scattered in the mucosa of stomach & small intestines - single cell glands, produce protective mucus.
- 23. Stratified Squamous Epithelium •Structure Many layers (usually Cuboidal/columnar at base & squamous at surface) Found in those surfaces subject to friction. • Function – Protection – Keratin (protein) accumulates in older cells near the surface • waterproofs and toughens skin • Keratinized/ Non-keratinized
- 24. Stratified squamous keratinized • Loc:-skin • Superficial cell die & lose their nuclei • Keratin (+)
- 25. Stratified squamous non-keratinised •Loc:Mouth, tongue, pharynx, esophagus, vagina & cornea.
- 26. Stratified squamous epithelium •Eg.. vagina
- 27. Stratified Cuboidal epithelium •Loc:-large ducts of sweat glands, salivary glands, pancreas.
- 28. Stratified columnar epithelium •Loc:- palpebral conjunctiva
- 29. Special classification ofepithelium 1. PSEUDOSTRATIFIED EPITHELIUM • Structure – Irregularly shaped cells with nuclei at different levels – appear stratified, but aren’t. – All cells reach basement membrane • Function – Absorption and Secretion – Goblet cells produce mucus – Cilia (larger than microvilli) sweep mucus • Location – Respiratory Linings & Reproductive tract
- 30. 2. TRANSITIONAL EPITHELIUM • Structure –Many layers / Stratified epithelium – Very specialized • cells at base are cuboidal or columnar, at surface will vary. – Change between stratified & simple as tissue is stretched out. • Function – Allows stretching (change size) – Impermeable to salts • Location – Urinary bladder, ureters & urethra
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- 32. Apical domain andits modifications -exhibits special structural surface modifications to carry out specific fxns.
- 33. 1. Microvilli - fingerlike cytoplasmicprojections - increase surface area for absorption - length= 5 µm - vary a) short, irregular, bleb-like (transepithelial transport is less). b) tall, closely-packed, uniform ( transport fluid & absorb metabolites).
- 34. 2. STEREOCILIA • Extremelylong, immotile microvilli. • length= 5-10 µm Limited to:• Epididymis • Proximal part of ductus deferens • Sensory cells of the inner ear In EM:- hairs of a paint brush
- 35. 3. Cilia - hairlike extensions of apical plasma membrane containing anoxeme. - motile extensions Moves mucus, etc. over epithelial surface 5-10 µm : length 0.2 µm : diameter
- 36. 3 Types ofcilia 1. Motile:- large no. (+)nt on the apical domain of many epithelial cells. 2. Primary / Monocilia:- solitary projections, Immotile - single cilium per cell (+)nt fxn:- Chemosensors mediate light sensation Osmosensors Odorant Mechanosensors sound perception in multiple organs in the body 3. Nodal cilia:-Found in the embryo on the bilaminar germ disc -Concentrated in the area that surrounds the primitive node.
- 38. Lateral domain &its specializations • Characterized by the presence of CAMs
- 39. Classification of cellcontacts • Unspecialized contacts -Cell adhesion molecule - Each CAM is in contact with intermediate protein. -Force is transmitted from cytoskeleton of one cell to another. -TEM:- bead-like
- 40. Specialized junctional structures •Forms the barrier & attachment device junctional complex responsible for joining cell together. • Three types:1. Anchoring jxns 2. Occluding jxns/ tight cell to cell contact: jxns / Zonula occludens (a). Macula adherens (Desmosomes) (b). Zonula adherens 3. communicating jxns/ Gap (Adhesive belts) jxns Cell to extracellular matrix : (a) Focal adhesions / Adhesive strips (b) Hemidesmosomes / Focal spots
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- 51. TYPES OF CELLJUNCTIONS
- 52. TYPES OF CELLJUNCTIONS
- 53. Basal domain BASEMENT MEMBRANE •Amorphous, dense layer of variable thickness at the basal surfaces of epithelia. • Consists of: 1. Basal lamina a). Lamina densa b). Lamina Lucida 2. Reticular lamina • Visible under LM
- 54. BASEMENT MEMBRANE • Functions: 1.Adhesion 2. Act as barriers 3. Cell organization 4. Regeneration of peripheral nerves after injury
- 55. GLANDS EXOCRINE GLANDS ENDOCRINE GLANDS -Consistsof duct - Lacks duct system -Secretes their product into the - Secrete their product into the CT surface directly / thru the duct enter bloodstream reach target cells -Secretion: Unaltered, concentrated -product called as HORMONES - Sweat, Oil glands, Salivary glands, - Thyroid, adrenal and pituitary Mammary glands. glands
- 56. Classification of Exocrineglands 1. Unicellular - simplest, single cell - Unbranched duct 2. Multicellular / compound - > one cell - Branched duct
- 57. 1. Tubular:- tubelike 2. Alveolar/ Acinar:- flask shaped 3. Tubuloalveolar:- tube ends in sac like dilation ** Tubular secretory portions:- straight, branched, coiled ** Alveolar portions:- single / branched
- 59. Modes of Secretion 1.Merocrine Glands:• secretory products del in membrane bounded vesicles apical surface of cells extrude by exocytosis • Eg.. Pancreatic acinar cells, sweat gland, salivary glands
- 60. Modes of Secretion 2.Apocrine Glands:• Secretory product released in apical portion of cell surrounded by a thin layer of cytoplasm within an envelope of plasma membrane. • Eg.. Mammary gland, ceruminous gland of ext auditory meatus
- 61. Modes of Secretion 3.Holocrine Glands:• Secretory product accumulates within the cell programmed cell death • Sec products & cell debris discharged into lumen • Eg.. Sebaceous gland of skin, meibomian glands
- 62. PARACRINE GLANDS • Secretorymaterial reaches the target cells by diffusion through the extracellular space / subjacent CT. ENDOCRINE GLANDS • Eg… Pituitary gland, ovaries, testes, pancreas Thyroid gland, Adrenal gland
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