Histology

1. Epithelial Tissues
Lector – professor Boronikhina Tatiana Vladimirovna

2. Tissues are aggregates of cells and extracellular material
organized to perform distinctive functions
Tissue groups:
 Epithelial tissues
 Internal medium tissues
(blood, lymph, and all types of connective tissues)
 Muscular tissues
 Nervous tissue
Tongue ⇒

3. Epithelial tissue localization
 Covering epithelia ⇒
- cover or line body surface,
body cavities, and hollow organs
 Glandular epithelia ⇒
- form glands

4. Epithelial tissue functions
 barrier
 protection (mechanical and chemical)
 outer exchange
 secretion
 reception
(neuroepithelial cells)
 contraction
(myoepithelial cells)

5. Epithelial tissue morphologic characteristics
 occupy boundary position
 consist of cells, lack extracellular substance
 rest on the basement membrane
 are polarized
 are avascular
 possess a high capacity for regeneration

6. Epithelial tissue cells - epitheliocytes
 cell shape – flat (squamous), cuboidal, columnar
 nucleus shape – flat, round, oval

7. Epitheliocyte cytoskeleton
 microtubules
 actin microfilaments
 keratin filaments
cytokeratins are immunocytochemical markers of epithelial cells
⇑

8. Epithelial cell junctions
 Simple contacts
 Interdigitations
 Zonula adherens
 Macula adherens (desmosome)
 Tight junctions
 Gap junctions (nexuses)

9. Desmosomes
 principal epithelial cell adhesive (adherent) junctions
⇔

10. Tight junctions (z. occludens)
 close intercellular gaps (occluding junctions)
⇔

11. Gap junctions (nexuses)
 provide cell to cell communications

12. Epithelia rest on the basement membrane
 layer of intercellular material
 is jointly manufactured by epithelium and underlying connective tissue
Functions
- attachment
- separation
- nutrition

13. Basement membrane ultrastructure
 consists of lamina lucida and lamina densa
Lamina densa composition
- proteins: laminin, type IV collagen
- glycoproteins
- proteoglycans
Lamina lucida composition
- integrin receptors

14. Epitheliocyte attachment to the basement membrane
 adhesive molecules
(integrin, fibronectin, laminin 5)
 hemidesmosomes
⇑
⇐

15. Basement membrane attachment to the underlying
connective tissue
 layer of reticular fibers (type III collagen)
 anchoring fibrils ( type VII collagen)
⇔

16. Polarity of epithelia
 apical pole (domain) and basal pole (domain)
 polarity depends on epithelium boundary position
stratified epithelium polarity
⇑

17. Epithelial cell specializations on the apical surface -
microvilli
 amplify the plasmalemma surface for transport
Striated epithelia (with brush border)
- intestine
- gallbladder

18. Epithelial cell specializations on the apical surface - cilia
 cilia move mucous
Ciliated epithelium of
- air passages
- uterus
- oviducts

19. Epithelial cell specializations on the basal surface
 hemidesmosomes
plasma membrane infoldings
⇐ (basal striations)
⇑

20. Epithelia lack blood vessels (avascular tissues)
 epithelia are supplied by diffusion
⇐ from the underlying connective tissue
⇑ through the basement membrane

21. Epithelial tissue embryonic origins
 Epithelial tissues arise from three germ layers
- ectoderm
- endoderm
- mesoderm

22. Ectodermal epithelia
 are stratified or pseudostratified
cornea
skin
sebaceous gland
sweat gland ⇒
esophagus

23. Endodermal epithelia
 are simple
small intestine
gallbladder
stomach
⇐ pancreas

24. Mesodermal epithelia
 are simple
kidney
mesothelium

25. Epithelial tissue morphological classification
 simple epithelia  stratified epithelia

26. In simple epithelia all cells rest on the basement membrane
 isomorphic epithelia
 anisomorphic (pseudostratified)
epithelium ⇒
- squamous
- cuboidal
- columnar

27. Simple squamous epithelium - mesothelium
total preparation ⇒
section ⇒

28. Mesothelium lines serous cavities
(the pericardial, pleural, and peritoneal ones)
 Functions
- passage of fluid into and out of serous cavities
parietal and visceral peritoneum

29. Simple cuboidal epithelium
 - gland ducts ⇒
 - kidney tubules ⇑
parotid gland striated duct
Functions
- transport water and ions

30. Simple columnar epithelium
 - small intestine ⇒
 - large intestine
 - gallbladder

31. Simple columnar striated epithelium of
the small intestine
 covers the villi and forms crypts

32. Brush border consists of microvilli
on the epithelial cell apical surface
 amplifies plasma membrane surface for
– absorption
– membrane digestion
glycocalyx of microvilli
⇔

33. Goblet cells
 unicellular endoepithelial glands
 secrete mucous

34. Villus – crypt complex
 crypts contain cambial cells
 crypts provide villus epithelium regeneration
local cambium

35. Simple columnar glandular epithelium of the stomach
 each epithelial cell secretes mucous
 mucous provide mechanical and chemical protection of gastric epithelium
gastric mucosa
secretory granules
in the epithelial cell

36. Simple columnar ciliated epithelium
 - uterus
 - oviducts
scanning EM of cilia
⇓
⇑

37. Simple pseudostratified epithelium of the air passages
 Cell types
- ciliated
- goblet
- short and high intercalated
(cambial cells)
cells are different in shape
(anisomorphic epithelium)

38. Mucociliary escalator (transport)
 cilia move mucous and foreign particles towards the pharynx

39. Stratified epithelia
 only cells of the basal layer are in contact with the basement membrane
 cambial cells are positioned in lower layers
 vertical anisomorphism ⇒ ⇑
epithelium shape depends
on superficial cell layer

40. Stratified cuboidal and columnar epithelia
 line ducts of some glands
(sweat, salivary, mammary glands)
sweat gland
⇔

41. Stratified squamous nonkeratinized epithelium
 - cornea
 - vagina - oral cavity
 - esophagus

42. Corneal epithelium
 Layers
- basal
- spinulate
- superficial (squamous)
 superficial layer is bathed by tears
afferent innervation of epithelium
⇑

43. Keratinization of stratified epithelia
 accompanies epithelial cell differentiation
 cells (keratinocytes) accumulate proteins (keratin),
lose nuclei and organelles converting into squamas ⇒
(scales)
tongue

44. Significance of keratinization
 mechanical and chemical protection
 corneous layer is impermeable to water, bacteria, and toxins
corneous layer ⇒

45. Stratified squamous keratinized epithelium of the thick skin
 - skin of the palms and soles
sinuous basement membrane
amplifies surface of
- contact with underling LCT
- cambium localization
⇐

46. Thick skin epithelium layers
 Stratum basale
 Stratum spinosum
 Stratum granulosum
 Stratum lucidum
 Stratum corneum
stratum spinosum cells
Cambial layers
- Stratum basale
- Stratum spinosum

47. Thin skin epithelium
 - skin with hair follicles
Layers
- Stratum basale
- Stratum spinosum
- Stratum granulosum (poor-developed)
- Stratum corneum (thin)
⇔

48. Stratified transitional epithelium
 lines urinary passages
(ureters, urinary bladder, urethra)
ureter
⇔

49. Transitional epithelium layers
 basal
 intermediate
 superficial (dome-shaped cells)

50. Transitional epithelium changes the number of its layers
 depending on the degree of stretching
empty urinary bladder
full urinary bladder

51. Covering epithelium is renewing population
 cell regeneration (renewal) ⇒ cambium is well-developed and active
Cambium localization
 in simple epithelia
- diffuse
- local (intestine epithelium)
 in stratified epithelia
- in basal layers
⇐

52. Glandular epithelium
 forms exocrine glands and some endocrine glands
consist of
secretory portions and ducts
are ductless
⇓ ⇓

53. Embryonic gland development from covering epithelia

54. Exocrine gland classification
 simple
 nonbranched, branched
 tubular, alveolar
 compound
 branched
 tubular, alveolar,
tubuloalveolar

55. Gastric glands
 simple tubular
slightly branched
⇔

56. Sweat gland
 simple nonbranched tubular coiled
⇔

57. Sebaceous gland
opens into the hair follicle
 simple
branched
alveolar
⇓

58. Compound branched glands
 glandular tissue (parenchyma) forms lobules
connective tissue
forms trabeculae
(stroma)
⇐
⇒
salivary gland
mammary gland

59. Secretory portion types (type of secretion produced)
 serous
 mucous
 mixed

60. Sebaceous and salt secretory portions
 sebaceous gland
 sweat gland
⇐
 lacrimal gland
⇒

61. Secretory portion cells (glandulocytes)
In cytoplasm
 rER
 sER
 Golgi apparatus
 secretory granules
serous secretory granules
mucous secretory granules
⇓
⇓

62. Glandulocyte polarity
 secretory granules in the apical cell portion ⇒
 nucleus and organelles in the basal cell portion
rER
⇒
pancreas acini

63. Endocrine cell polarity
 secretory granules are in the basal cell portion
⇔

64. Glandulocyte secretory cycle
 uptake of substances
 synthesis of secretory product
 packing of secretory granules
 accumulation of secretory granules
 release of secretion (extrusion)
⇔
pancreas acinus cell

65. Glandulocyte modes of secretion (extrusion)
merocrine apocrine holocrine

66. Apocrine mode of secretion
 inheres in
- some sweat glands
- mammary glands

67. Holocrine mode of secretion
 inheres in only the sebaceous glands
⇔

68. Some ducts take part in secretory product formation
 pancreatic intercalated duct
 salivary gland striated duct
⇓
⇑

69. Myoepithelial cells
 are contractile epitheliocytes
 contain myosin and actin microfilaments
 reside in secretory portions and small ducts
 lie between the basement membrane and glandulocytes
possess processes
provide the secretion discharge

70. Myoepithelial cells exist in ectodermal glands
 sweat gland
 mammary gland
 salivary gland ⇒
⇓
⇓
⇐

71. Hormonal regulation of secretion
 mammary glands
⇐ prolactin
oxytocin ⇒

72. Nervous regulation of secretion
 secretory nerve endings
 are formed by autonomic motor neuron axon

73. Glandular epithelium is stable (growing) population
 long-living cells ⇒ intracellular regeneration (renewal)
 cellular regeneration is possible
 cambium
- reside in small ducts
- is not active
gastric glands
⇐
exception – sebaceous
holocrine glands ⇒

74. Спасибо за внимание !Thank you for attention!