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Histology Final > Epithelial tissue > Flashcards

Epithelial tissue Flashcards

(47 cards)

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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

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A

Electron lucent

ARTIFACT

20
Q

Lamina densa

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A

Electron dense

Type IV Collagen, glycoproteins

21
Q

Lamina fibroreticularis

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A

Electron lucent

type III, IV, VII Collagen, elastic fibers

22
Q

Functions of the Basement membrane (5)

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

Microvilli

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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

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A

Long, hair-like

two types: motile and non-motile

25
Motile cilia:
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
Non-motile cilium
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
Stereocilia
Immotile!!! in Male reproductive and inner ear internal bundle of actin Filaments increase Surface for absoption in epidydimis and exitation in inner ear
28
Functional types of intercellular junctions
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
Occluding junctions --> Zona occludens
- Most apical Junction - blocks passage of laminar Contents - sealing Strands: transmembrane proteins of two cells link and acclude
30
Pathways for Transport of substances across epithelia
TRANSCELLULAR: across Plasma membrane, active, required Energy dependent channels and proteins PARACELLULAR: across zonula occludens, dependend on tightness of zonula occludens
31
Types of adhering (anchoring) junctions
Zonula adhernes Macula adherens (desmosomes) Hemidesmosomes
32
Zonula adherens
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
Macula adherens (desmosomes)
spot-like scattered over intercellular surfaces | overlapping Segments of CADHERINS
34
Hemidesmosomes
- 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
Communicating Junction (gap or Nexus Junction)
patch-like Accumulation of transmembrane channels or pores Each channel is formed by two half channels --> CONNEXONS connexon made of 6 CONNEXIN subunits
36
Exocrine vs Endocrine glands
Exocrine: connected to the Surface Epithelium by ducts Endocrine: lost Connection to Epithelium, NO DUCTS; release secretions (Hormones) into blood
37
Glands by their number of cells
1. Unicellular Glands: goblet cells and cells of DNES | 2. Mulitcellular glands
38
Goblet cell
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
Multicellular exocrine gland
Secretory comonent (end piece) and duct (cennects secretory component to Surface)
40
Classification of Glands according to shape of secretroy component
Tubule - like: TUBULAR Spherical: ACINAR ( ALVEOLAR) Branched: BRANCHED (TUBULAR or ACINAR or TUBULE-ACINAR)
41
Classification of Glands according to shape of the duct
Unbranched --> SIMPLE GLAND | Branched --> COMPOUND GLAND
42
Classification of Glands according to chemical composition of secretory products
Serous (Proteins) Mucous (rich in carbs) Mixed (serous and mucous) Sebaceous (sebum --> oily material)
43
Classification of Glands accrding to the way of secretion
Merocrine (eccrine) Apocrine Holocrine
44
Merocrine (eccrine) secretion
most common | secretory product is delivered in membrane Bound vesicles to apical Surface --> exocytosis
45
Apocrine secretion
- found in lacting mammary Gland - product is released in apical Portion of cell - apical Portion of the cell is pinched off
46
Holocrine secretion
- 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
Epithelial cell renewal
- 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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