18 epithelium poonam

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18 epithelium poonam

  1. 1. EPITHELIUM CAPT DR POONAM SINGH DEPT OF ANATOMY
  2. 2. SEQUENCE OF PPT 1. 2. 3. 4. 5. 6. 7. 8. INTRODUCTION DEVELOPMENT CLASSIFICATION HISTOLOGICAL APPEARANCE APICAL DOMAIN & ITS MODIFICATIONS LATERAL DOMAIN & ITS SPECIALIZATIONS BASAL DOMAIN GLANDS & ITS TYPES
  3. 3. TISSUES 4 Basic types
  4. 4. DEVELOPMENT
  5. 5. 5 – 6 DAY
  6. 6. 6th DAY Implantation of the Blastocyst
  7. 7. 9TH DAY
  8. 8. DEVELOPMENT
  9. 9. 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.
  10. 10. EPITHELIUM • Avascular tissue composed 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
  11. 11. FUNCTIONS 1. 2. 3. 4. 5. 6. Protection Absorption Secretion lubrication Transportation Receptor fxn ( sensory)
  12. 12. 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
  13. 13. CLASSIFICATION • Based on 2 factors:1. Simple / Unilaminar 2. Compound / Stratified / Multilaminar
  14. 14. Based on the shape of surface cells:- W>H W=H H>W
  15. 15. EPITHELIUM UNILAMINAR/ SIMPLE MULTILAMINAR/ SRTATIFIED SQUAMOUS STRATIFIED SQUAMOUS 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
  16. 16. Classification of Epithelial Tissue
  17. 17. 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
  18. 18. 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
  19. 19. Simple Columnar Epithelium • Structure – Elongated layer of cells with nuclei at same level • Function -- Absorption, Protection & Secretion • Location -- GIT
  20. 20. Simple Columnar Epithelium with 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
  21. 21. Simple Columnar Epithelium with specializations 3. With secretory function: Goblet cells - scattered in the mucosa of stomach & small intestines - single cell glands, produce protective mucus.
  22. 22. 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
  23. 23. Stratified squamous keratinized • Loc:- skin • Superficial cell die & lose their nuclei • Keratin (+)
  24. 24. Stratified squamous non-keratinised • Loc:Mouth, tongue, pharynx, esophagus, vagina & cornea.
  25. 25. Stratified squamous epithelium • Eg.. vagina
  26. 26. Stratified Cuboidal epithelium • Loc:-large ducts of sweat glands, salivary glands, pancreas.
  27. 27. Stratified columnar epithelium • Loc:- palpebral conjunctiva
  28. 28. Special classification of epithelium 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
  29. 29. 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
  30. 30. URINARY BLADDER
  31. 31. Apical domain and its modifications -exhibits special structural surface modifications to carry out specific fxns.
  32. 32. 1. Microvilli - fingerlike cytoplasmic projections - 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).
  33. 33. 2. STEREOCILIA • Extremely long, 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
  34. 34. 3. Cilia - hair like extensions of apical plasma membrane containing anoxeme. - motile extensions  Moves mucus, etc. over epithelial surface  5-10 µm : length  0.2 µm : diameter
  35. 35. 3 Types of cilia 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.
  36. 36. Lateral domain & its specializations • Characterized by the presence of  CAMs
  37. 37. Classification of cell contacts • 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
  38. 38. 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
  39. 39. Desmosomes
  40. 40. Zonula adherens
  41. 41. ANCHORING JUNCTIONS DESMOSOME ZONULA ADHERENS
  42. 42. Fascia adherens
  43. 43. Hemidesmosomes
  44. 44. Occluding junctions
  45. 45. Gap junctions
  46. 46. TYPES OF CELL JUNCTIONS
  47. 47. TYPES OF CELL JUNCTIONS
  48. 48. 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
  49. 49. BASEMENT MEMBRANE • Functions: 1. Adhesion 2. Act as barriers 3. Cell organization 4. Regeneration of peripheral nerves after injury
  50. 50. GLANDS EXOCRINE GLANDS ENDOCRINE GLANDS -Consists of 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
  51. 51. Classification of Exocrine glands 1. Unicellular - simplest, single cell - Unbranched duct 2. Multicellular / compound - > one cell - Branched duct
  52. 52. 1. Tubular:- tube like 2. Alveolar/ Acinar:- flask shaped 3. Tubuloalveolar:- tube ends in sac like dilation ** Tubular secretory portions:- straight, branched, coiled ** Alveolar portions:- single / branched
  53. 53. 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
  54. 54. 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
  55. 55. 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
  56. 56. PARACRINE GLANDS • Secretory material reaches the target cells by diffusion through the extracellular space / subjacent CT. ENDOCRINE GLANDS • Eg… Pituitary gland, ovaries, testes, pancreas Thyroid gland, Adrenal gland
  57. 57. DISCUSSION

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