Epithelial Tissue

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Chapter 4

• Epithelial Tissue

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I. General Characteristics

• A. Functions
• 1. covering and lining surfaces skin
• 2. absorption intestine
• 3. secretion glands
• sensation sensory receptors

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I. General Characteristics

• B. Structure
• 1. little intercellular substance
• 2. cells attached to each other
• 3. cells form sheets
• 4. cell shapes squamous, cuboidal, columnar
• 5. nuclei shapes flattened, spherical, elongated

4-11
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I. General Characteristics

• B. Structure (4.1)
• 6. lamina propria loose CT deep to basal lamina
• 7. polarity apical basal surfaces
• 8. no blood vessels nutrients diffuse through
  basal lamina
• 9. often plentiful nerve supply
• 10. high regenerative capacity mitosis in basal
  layer e.g.,
• intestine replaced every 2-3 days cornea
  repaired within 24 hrs (look for mitoses)

4-11
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II. Basal Lamina

• A. Structure (4.12,4.1)
• 1. basal surface of all epithelia on basal lamina
• BL connective tissue, 20-100 nm thick, seen only
  with EM
• regulates flow of material to from epithelium
• 2. BL attached to underlying CT anchoring
  function

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III. Intercellular Junctions

• A. Tight junctions (4.5,15.33)
• EM outer leaflets of adjacent PM fused
• function prevent flow of material between cells

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III. Intercellular Junctions

• A. Tight junctions
• FF technique similar to ziploc bag attachments,
  ridges/grooves
• (4.6,2.3)

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III. Intercellular Junctions

• Zonula Adherens (4-4,4-5) (intermediate junction)
• band of cell attachments

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III. Intercellular Junctions

• C. Terminal Bar see in lab? (4-5, 4-11C)
• LM observation tight junctions zonula adherens

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III. Intercellular Junctions

• D. Gap Junctions
• FF aggregates of integral proteins
• TEM uniform intercellular junction
• (2-3,4-7)

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III. Intercellular Junctions

• D. Gap Junctions (4.7A)
• connexon gap junction integral protein subunits
  arranged in hexagonal shape with central pore
  aligned with central pore in adjacent cell
• function allows flow of 1500 MW or smaller
  molecules between cells, e.g. ions

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III. Intercellular Junctions

• E. Desmosomes (macula adherens) (4.5)
• attachment plaques
• intermediate filaments associated with attachment
  plaques
• See also stratum spinosum in skin

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IV. Surface Specializations

• A. Microvilli finger like projections of
  PM(15.21,15.22,4.8)
• 1 ?m long, 0.08 ?m diameter
• seen as brush border with LM
• nonmotile
• stereocilia long microvilli

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IV. Surface Specializations

• B. Cilia Flagella
• motile (4.10)
• 5-10 ?m long, 0.2 ?m diam
• internal MT structure 92
• capable of coordinated movement over epithelial
  surface
• uses ATP
• loc resp sys, repro sys

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V. Covering Lining Epithelia

• A. Simple(4.11)
• 1. squamous blood vessels
• 2. cuboidal kidney tubules
• 3. columnar intestines

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V. Covering Lining Epithelia

• B. Stratified (classify by superficial layer)
• 1. squamous (4.12)
• a. keratinized skin
• b.nonkeratinized cornea
• transitional ureter, urinary bladder
• very rare
• Stratified cuboidal
• 2. Stratified columnar

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V. Covering Lining Epithelia

• C. Pseudostratified ciliated columnar resp tract
  (4.12)

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VI. Glandular Epithelium

• A. Types
• 1. exocrine secretes into ducts
• endocrine ductless, secretes into extracellular
  space
• unicellular secretes onto epith surf

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VI. Glandular Epithelium

• B. Structural types of exocrine glands(4.22)
• 1. simple 1 duct
• a. tubular
• b. acinar
• 2. branched
• a. tubular
• b. acinar
• 3. compound
• a. tubular
• b. acinar
• 4. Unicellular
• XS view?