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MBBS 1: Musculoskeletal Anatomy > Epithelial Tissue and Glands > Flashcards

Epithelial Tissue and Glands Flashcards

1
Q

What are the 4 types of primary tissues?

A
  1. epithelial 2. connective 3. neural 4. muscle
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2
Q

Define epithelium?

A

avascular closely packed cells that line the external surface and internal closed cavities

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3
Q

What are the 3 embryonic germ layers?

A
  1. ectoderm 2. mesoderm 3. endoderm
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4
Q

What are the functions of epithelium? PASSST

A
  1. transportation - of substances across the epithelia 2. sensation & detection - olfactory mucosa, taste buds, retina and hair cells in ears 3. protection e.g. skin 4. selective permeability 5. secretion - mucus, hormones, enzymes 6. absorption - materials from lumen
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5
Q

Types of epithelial tissue?

A
  1. surface epithelium 2. glandular epithelium
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6
Q

How is epithelia classified?

A
  1. number of cell layers - simple and strattified 2. shape of cell - squamous, cuboidal, columnar, pseudostratified, transitional
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7
Q

Describe classification of epithelia?

A

A. number of cells : 1. simple - single layer 2. stratified - multiple cell layers B. shape of cell : 1. squamous - flat 2. cuboidal - square/cube shaped 3. columnar - column shaped 4. psuedostratified - one cell layer but looks like multiple because nuclei are at different levels + not all cells reach the cell surface 5. transitional - have a round cap/umbrella shape

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8
Q

Describe special features of epithelia?

A
  1. goblet cells - secrete mucus 2. keratinized layer - layer of dead cells with no nuclei and filled with keratin 3. cilia - movement of substances across the epithelial surface 4. microvilli - increase surface area for absorption 5. stereocilia - specialized long immotile microvilli found in olfactory hair cells of the ear
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9
Q

Describe specialized epithelial cells?

A
  1. goblet cells - secrete mucus 2. myoepithelial cells - contractile, located between epithelia and basement membrane 3. neuroepithelial - auditory hair cells, taste buds, photoreceptors of retina, olfactory epithelia and chemo/osmotic receptor cells
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10
Q

What are the 3 characteristic features of epithelium tissues?

A
  1. cells are polarized 2. cells adhere to each other by cell to cell junctions 3. cells have a basement membrane
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11
Q

What is a polarized cell?

A

cell divided morphologically/functionally to biochemical domains

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12
Q

Name the surface domains?

A
  1. apical 2. lateral 3. basal
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13
Q

What is the apical domain?

A

the side of the cell that faces the external environment/lumen

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14
Q

What is the surface of epithelial cells rich in? Transport + Recognition

A
  1. ion channels and carrier proteins - for the transportation of substances across the epithelia 2. glycocalyx (glyoproteins and glycolipids) - for recognition of cells and substances
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15
Q

Name and describe modifications of the top surface?

A
  1. striated microvilli/brush border - increase surface area 2. keratinized layer - layer of dead cells with no nuclear filled with keratin 3. stereocilia - long immotile finger like extentions required for hearing and balance
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16
Q

Name the cell to cell junctions?

A
  1. zonulae occludens/occluding junctions (tight) 2. anchoring junctions (adhesion) 3. gap junctions (communicating)
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17
Q

How are cells attached at the lateral domain?

A

cell to cell junctions

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18
Q

What are these junction?

A

zonulae occludens/occluding (tight), anchoring (adhesion) and gap (communicating) junctions

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19
Q

3 factors of tight junctions?

A
  1. created by localized sealing of adjacent plasma membranes of epithelial cells 2. are concentrated towards the apical surface 3. they are a permeability barrier
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20
Q

What do they use as the cytoskeletal component?

A

actin filaments

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21
Q

What are they made of?

A

claudins, occludins, and JAM cell adhesion molecules

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22
Q

What are the adapters?

A

ZO-1, ZO2, ZO3, cyngulin, sympleitin

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23
Q

What do pathogenic agents cause?

A

act on ZO1 - causing junction to become permeable e.g. cholera toxins

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24
Q

Mutation of Claudin - 16?

A

Claudin 16 is present in tight junctions of distal kidney tubule - its mutation will affect selective permeability & absorption of Mg2+ into blood stream

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25
Q

Function of Claudin - 1?

A

Claudin 1 is present in epithelial junctions of skin responsible for water proofing/water barrier - keratin comes second in this regard

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26
Q

What is the blood-brain barrier?

A

tight juctions protect neurons from toxins through the Blood-Air barrier

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27
Q

What is function of gap junctions?

A

mediate electrical and chemical coupling between cells (ions, amino acids, etc)

28
Q

What is a gap junction made of and how many?

A

formed from 2 connexons (one on each cell)

29
Q

What is a connexon made of?

A

6 connexin proteins

30
Q

What is gap junction permeability regulated by?

A

by calcium, pH, and phosphorylation of connexins

31
Q

Mutations in Connexin 26 cause?

A

connexin 26 is highly exprssed in cells of the cochlea - causing deafness

32
Q

Mutations in Connexin 50 cause?

A

connexin 50 is associated with congenital cataracts - leading to blindness

33
Q

Function of Connexin 40?

A

spread impulses to the heart

34
Q

What are 4 examples of anchoring junctions?

A
  1. macula adherens/desmosomes 2. zonula adherens 3. hemidesmosomes 4. focal adhesions
35
Q

What is the cytoskeletal component of zonulae adherens?

A

actin filament

36
Q

What is the function of actin filaments?

A

connects the cytoskeleton of one cell to the cytoskeleton of another cell - making the adhesion belt

37
Q

Name the adhesiosn molecules and adapters of the adhesion belt?

A

adapter = E-cadherins and adhesion molecules = Ca2+

38
Q

How is cadherin linked to actin?

A

via catenin and vinculin

39
Q

What are these junctions used in the formation of?

A

neural tube, branching morphogenesis of mammary, salivary glands

40
Q

What anchoring junction is used for tensil strength?

A

macula adherens/desmosomes

41
Q

What is the cytoskeletal component for desmosomes?

A

intermediate filament

42
Q

How does it do this?

A

by using cadherins (desmoglein and desmocollin)

43
Q

What do cadherins use?

A

desmoplakins and plakoglobins adapter proteins

44
Q

What are 2 examples of intermediate filaments of desmosomes?

A
  1. keratin filaments (epithelial cells) 2. desmin filaments (heart muscle)
45
Q

What is pemphigus vulgaris?

A

is an auto-immune disease in which the body produces auto-antibodies against desmosome proteins, binding of the auto-antibodies disrupts cell adhesion - skin integrity is compromised leading to widespread blistering and loss of extracellular fluids

46
Q

What are the cell-to-extracellular matrix junctions?

A
  1. hemidesmosomes 2. focal adhesions
47
Q

What is the function of hemidesmosomes?

A

connect intermediate filaments in the cell to the basal lamina (ECM)

48
Q

What is the function of focal adhesions?

A

create a link between the actin cytoskeleton and extracellular matrix proteins

49
Q

What do they consist of ?

A
  1. cytoplasmic face : where actin binds - vinculin & talin 2. transmebrane region - integrins 3. extracellular face : where extracellular proteins bind e.g. fibronectin, collagen, ephrins, laminin
50
Q

Where are the basal surface located?

A

unberlying epithelial cells

51
Q

What is the basal surface characterised by?

A
  1. basement membrane 2. cell to extracellular matrix junctions 3. plasma membrne
52
Q

What does the basement membrane consist of?

A

1.Basal lamina - secreted by epithelial cells 2. Reticular lamina (lamina reticularis)- secreted by connective tissue cells (collagen type I and type III)

53
Q

What are the functions of basal laminas?

A
  1. support - for overlying epithelium 2. differentiation - via signaling by integrins 3. cell migration 4. filter - for large particles 5. wound response - clotting 6. has a role in cancer metastasis - cells break this barrier to spread
54
Q

What is the reticular lamina?

A

a layer of reticular fibers that underlies the basal lamina secreted by CT cells

55
Q

What are the Structures responsible for attachment of basal lamina to the underlying CT ?

A
  1. anchoring fibrils (type VII collagen) 2. fibrillin microfibrils
56
Q

Definition of glandular epithelium?

A

type of epithelial tissue which cover the glands of the body

57
Q

What are glands?

A

organized arrangements of secretory cells

58
Q

What are the major types of glands?

A
  1. exocrine - glands that secrete their products via ducts or tubes 2. endocrine - glands that release their products basally into the underlying connective tissue and enter the vascular system (no duct systems) 3. paracrine - secretions reach target cells by diffusion through the extracellular space or immediately subjacent connective tissue
59
Q

Classification of glandular epithelia according to the number of secretory cells?

A
  1. unicellular glands - have one cell e.g. goblet cells that secrete mucus 2. multicellular glands - glands have many cells
60
Q

Classification of glandular epithelia according to their nature of secretion?

A
  1. serous - cell-type that produces a thin watery, protein-rich secretion 2. mucous - cell type that secretes viscous hydrophilic glycoproteins called mucins (that have a lubricating or protective function) 3. mixed - these glands have both serous and mucous cells
61
Q

Classification of glandular epithelia according to their mechanism of secretion?

A
  1. merocrine secretion 2. holocrine 3. apocrine
62
Q

Merocrine secretion?

A
  1. the membrane bound secretory granules fuse with the apical membrane 2. the contents of the granule are opened and released by exocytosis 3. the secretory granules leave the cell with no loss of other cellular material. e.g. Pancreatic acinar cells
63
Q

Apocrine secretion?

A
  1. secretory granules gather at the apical region of the cell 2. a portion of the cytoplasm of the cell simply pinches off enclosing the granules 3. within the lumen, secretory vesicle breaks down and releases the gland’s products e.g. lactating mammary glands
64
Q

Holocrine secretion?

A
  1. granules fill the cell until the entire cell becomes “bloated” with secretory products 2. cell undergoes apoptosis 3. secretory product constitutes entire cell and its product e.g. in sebaceous glands of the skin
65
Q

Classification of glandular epithelia according to the shape of secretory units?

A
  1. tubular - elongated group of secretory cells with a tube-shaped lumen e.g gastric glands 2. acinar (or alveolar) - a small grape-like (acinus means “grape”) or sac-like (alveolus means “sac”) group of secretory cells arranged about a small lumen 3. tubulo-alveolar – lumen of secretory units have both of the above listed shapes
66
Q

Classification of glandular epithelia according to arrangement and occurrence of duct system?

A
  1. simple glands - have an unbranched duct into which the cells secrete
  2. compound glands - have branched duct system
67
Q

Describe types of exocrine glands?

A

1 simple tubular glands 2. simple alveolar (acinar) 3. simple branched alveolar 4. simple alveolar glands 5. compund tubular 6. compund alveolar 7. compund tubulo-alveolar

MBBS 1: Musculoskeletal Anatomy (15 decks)

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