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Histology Final > Epithelial tissue > Flashcards

Epithelial tissue Flashcards

1
Q

Tissue

A

System of similar cellular and non-cellular structures with same origin and same specific functions

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2
Q

Non-cellular structures:

A

ECM (fibers + Ground substance)

Symplast (formed by Fusion of myoblasts in striated msucle)

Syncytium (dividing cells that remain connected by cytoplasmic bridges

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3
Q

The four Basic types of tissue

A
  1. Epithelial tissue (covers surfaces, lines cavities and forms Glands)
  2. Connective tissue
  3. Muscle tissue
  4. Nervous tissue
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4
Q

Epithelial tissue origin and function

A

From all three germ layers

Protection, Absorption, Transport, secretion, sensory

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5
Q

Structural characteristics of epithelium

A

cells are connected by intercellular junctions
rest on Basement membrane
is AVASCULAR

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6
Q

Classification of epithelium

A

Simple: squamous, cuboidal, columnar, pseudostratified

Stratified: Squamous keratinized/ non-keratinized, cuboidal, columnar, transitional

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7
Q

Simple squamous epithelium

A

flattened nuclei
Location: Endothelium (blood vessels), Mesothelium (Body cavities), Epithelium (lung alveoli)

Function: Transport of gases or fluids

Embryological origin: Mesoderm and endoderm

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8
Q

Simple cuboidal epithelium

A

round nucleus in Center
Location: ducts and tubules

Function: excretory, secretory or absoptive

Embryological origin: ectoderm, Mesoderm, endoderm

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9
Q

Simple columnar epithelium

A

elongated nuclei at base
microvilli or cilia on apical Surface
Location: gastrointestinal, female reproductive

Function: Absorption, secretion, Transport

Embryological origin: Mesoderm and endoderm

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10
Q

Pseudostratified epithelium

A

nuclei are disposed on different Levels
Location: respiratory System, male reproductive

Function: protection, Transport

Embryological origin: Endoderm and mesoderm

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11
Q

Stratified cuboidal /columnar

A

Location: large excretory ducts

Function: protection

Embryological origin: ectoderm

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12
Q

Stratified squamuos non-keratinized

A

Location: cavities which are mechincally affected –> oral cavity, Pharynx, esophagus, anal canal, vagina

Function: protection

Emrbyological origin: ectoderm, endoderm

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13
Q

Stratified squamous keratinized

A

Location: Skin

Function: protection

Embryological origin: ectoderm

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14
Q

Layers of stratified squamous keratinized Epithelium (thin and thick Skin)

A

Thin Skin: basal, spinous, granular, corneal

Thick Skin: basal, spinous, granular, clear, corneal layer

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15
Q

Transitional Epithelium /urothelium

A

Basal cells–> cuboidal
Intermediate cells –> polygonal
Apical cells –> umbrella/dome cells

Location: Urinary tract

Function: for streching, withstands toxicity of Urine

Embryological origin: Mesoderm and endoderm

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16
Q

Surface specializations on basal, apical and lateral surfaces

A

Basal Surface: Plasma membrane interdigitations, Basement membrane, hemidesmosomes

Apical Surface: Microvilli, cilia, stereocilia

Lateral Surface: intercellular junctions

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17
Q

Plasma membrane interdigitations

A

Infoldings of Plasma membrane
in kidney tubules and striated ducts

Function: increasing the Surface for fluid transport

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18
Q

Basement membrane

A
  • attachment site for overlying epithelial cells and Underlying CT
  • 3 regions:
    1. Lamina lucida
    2. Lamina densa
    3. Lamina fibroreticularis
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19
Q

Lamina lucida

A

Electron lucent

ARTIFACT

20
Q

Lamina densa

A

Electron dense

Type IV Collagen, glycoproteins

21
Q

Lamina fibroreticularis

A

Electron lucent

type III, IV, VII Collagen, elastic fibers

22
Q

Functions of the Basement membrane (5)

A 
structural support
metabolic support
selective permeability barrier
cell Migration
Control of epithelial growth and differentiation
23
Q

Microvilli

A

Finger-like
Have core of actin micofilaments –> stability
Actin microfilaments are Held together by actin binding protein (VILLIN)

Actin microfilaments are connected to Plasma membrane by MYOSIN I

All microvilli in equal size: striated border
Mocrovilli in unequal size: brush border

24
Q

Cilia

A

Long, hair-like

two types: motile and non-motile

25
Q

Motile cilia:

A

Core (AXONEME): 2 microtubules
–> surrounded by 9 peripheral doublets

doublets are linked by NEXIN, connected to core by RADIAL SPOKES

DYNEIN ARMS: motor protein that moves along the Surface of the adjacent microtubule

Location: respiratory and female reproductive

Function: fluid flow and move of oocyte

26
Q

Non-motile cilium

A

called: Primary cilium, monocilium, sensory cilium

Function: sensor for mechanical and chemical Signals

Central doublet is absent!!
Dynein, nexin and radial spokes are absent!!

27
Q

Stereocilia

A

Immotile!!!
in Male reproductive and inner ear

internal bundle of actin Filaments

increase Surface for absoption in epidydimis and exitation in inner ear

28
Q

Functional types of intercellular junctions

A
  1. occluding (tight) junctions: barrier, for Regulation of permeability
  2. Adhering (anchoring) junctions: glue cells together, mechanical stability
  3. Communicating junctions: passage of small molecules
29
Q

Occluding junctions –> Zona occludens

A
  • Most apical Junction
  • blocks passage of laminar Contents
  • sealing Strands: transmembrane proteins of two cells link and acclude
30
Q

Pathways for Transport of substances across epithelia

A

TRANSCELLULAR: across Plasma membrane, active, required Energy dependent channels and proteins

PARACELLULAR: across zonula occludens, dependend on tightness of zonula occludens

31
Q

Types of adhering (anchoring) junctions

A

Zonula adhernes
Macula adherens (desmosomes)
Hemidesmosomes

32
Q

Zonula adherens

A

belt - like and near apical Surface
links cells by transmembrane proteins –> CADHERINS
binds to actin Filament of cell
electron dense Plaque can be seen on the cytoplasmic side of the membrane

33
Q

Macula adherens (desmosomes)

A

spot-like scattered over intercellular surfaces

overlapping Segments of CADHERINS

34
Q

Hemidesmosomes

A
  • on basal Surface of cell
  • connects Plasma membrane to Basement membrane - via INTEGRINS
  • Integrins bind to LAMININS in b.m.
    LAMININS bind to intermediate filaments
35
Q

Communicating Junction (gap or Nexus Junction)

A

patch-like
Accumulation of transmembrane channels or pores
Each channel is formed by two half channels –> CONNEXONS
connexon made of 6 CONNEXIN subunits

36
Q

Exocrine vs Endocrine glands

A

Exocrine: connected to the Surface Epithelium by ducts

Endocrine: lost Connection to Epithelium, NO DUCTS; release secretions (Hormones) into blood

37
Q

Glands by their number of cells

A
  1. Unicellular Glands: goblet cells and cells of DNES

2. Mulitcellular glands

38
Q

Goblet cell

A

Modified columnar cells
in simple Epithelium of intestine and respiratory tract
Aggregation of mucigen granules in apical Region
Nucleus in basal part
Has microvilli

39
Q

Multicellular exocrine gland

A

Secretory comonent (end piece) and duct (cennects secretory component to Surface)

40
Q

Classification of Glands according to shape of secretroy component

A

Tubule - like: TUBULAR

Spherical: ACINAR ( ALVEOLAR)

Branched: BRANCHED (TUBULAR or ACINAR or TUBULE-ACINAR)

41
Q

Classification of Glands according to shape of the duct

A

Unbranched –> SIMPLE GLAND

Branched –> COMPOUND GLAND

42
Q

Classification of Glands according to chemical composition of secretory products

A

Serous (Proteins)
Mucous (rich in carbs)
Mixed (serous and mucous)
Sebaceous (sebum –> oily material)

43
Q

Classification of Glands accrding to the way of secretion

A

Merocrine (eccrine)
Apocrine
Holocrine

44
Q

Merocrine (eccrine) secretion

A

most common

secretory product is delivered in membrane Bound vesicles to apical Surface –> exocytosis

45
Q

Apocrine secretion

A
  • found in lacting mammary Gland
  • product is released in apical Portion of cell
  • apical Portion of the cell is pinched off
46
Q

Holocrine secretion

A
  • in sebaceous Glands of Skin
  • Product accumulates within maturing which then undergoes programmed cell death
  • Product and debris are discharged Tino lumen of gland
47
Q

Epithelial cell renewal

A
  • rate of cell death = rate of cell replacement
  • replacement cells are produced by mitosis of adult stem cells
  • stem cells are located in niches:
  • -> in simple epith: between differentiated cells
  • -> in stratified epith: on b.m.

Histology Final (18 decks)

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