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BMS1060 > 8: Epithelial Tissue > Flashcards

8: Epithelial Tissue Flashcards

1
Q

Which acidic dye is used to stain nuclear DNA & RNA, and why is this?

A

Haematoxylin as it binds acidic components of cells

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2
Q

Which dye is used to stain basic components of cells, e.g. proteins in cytoplasm?

A

Eosin

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3
Q

What is epithelial tissue? Where is it found?

A

A continuous layer of closely packed cells that covers the external body surface and lines body cavities (and generally marks off our insides from our outsides)

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4
Q

What are the 2 types of epithelial tissue? Can you describe their function?

A

Epithelia: layers of cells covering internal/external surfaces
Glands: structures that produce secretions

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5
Q

What are the 6 functions of epithelial tissues?

A
  1. Provide physical protection: from abrasion, deconstruction & dehydration
  2. Control permeability: selectively filter biochemical substances; e.g. capillaries & lung alveoli (diffusion of gases)
  3. Provide sensation (sensory epithelium which contains sensory cells - nose, ears, eyes)
  4. Absorbing nutrients from food in digestive tract
  5. Secretion (glandular epithelium - hormones, mucus, etc.)
  6. Transport: ciliated epithelia sweep mucus, cells & other particles along the surface of epithelium
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6
Q

Give 5 characteristics of epithelial tissue

A
  1. Polarity: apical & basal surfaces
  2. Specialised contacts: cell junctions, closely packed cells
  3. Attachment: via basal lamina to underlying connective tissue
  4. Avascularity: no blood vessels as not enough space (but richly innervated)
  5. Regeneration: can replace lost cells by cell division
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7
Q

Describe the apical surface of epithelial tissue

A

Is always free; contains microvilli (increasing SA for increased absorption of nutrients e.g. lining intestine & kidney tubules)
& also contains cilia (helps move materials e.g. mucus, etc, lining trachea)

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8
Q

Describe the basal surface of epithelial tissue

A

In contact with basement membrane

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9
Q

Explain why the characteristic ‘specialised contacts’ is important

A

For strength and impermeability, due to mechanical connections between cells (& not much extracellular space)

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10
Q

Explain the characteristic ‘attachment’, i.e. what is the basement membrane composed of?

A

2 components of the basement membrane:
- Basal lamina :(epithelium side) glycoproteins secreted by epithelial cells; selective filter for molecules between connective tissue & epithelium
- Reticular lamina :(connective tissue side) layer of extracellular material (collagen) produced by connective tissue, provides basement membrane strength

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11
Q

Explain the characteristic ‘avascularity’

A

= no blood vessels (as not enough space): nutrients arrive by diffusion from blood vessels in connective tissue

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12
Q

Explain the characteristic ‘regeneration’

A

Epithelial tissue has a high regenerative capacity (can reproduce rapidly), as these cells are exposed to mechanical friction, disruptive enzymes, toxic chemicals & bacteria. So regeneration is essential to maintain tissue integrity & is achieved via cell division from stem cells.
* Skin = renewed once every 35 days
* stem cells in the basal layer divide & migrate to outer layers

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13
Q

Explain the key features of stem cells

A
  • They are undifferentiated cells (not committed to a specific cell type or function)
  • Self renewable (able to go through cell division while maintaining undifferentiated state)
  • After division each daughter cell can either remain a stem cell or can become a terminally differentiated cell
  • Different tissues have different regenerative capacity: high in epithelial tissue but very low in cardiac & nervous tissue
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14
Q

Explain how epithelial tissue is differentiated (number of cell layers)

A
  • Simple : one layer
  • Stratified : more than one layer
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15
Q

Explain how epithelial tissue is differentiated (cell shape)

A
  • Squamous : flat
  • Cuboidal : cube
  • Columnar : tall/column
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16
Q

Explain the differences between simple & stratified epithelia, in terms of function

A
  • Simple = better for diffusion (shorter distance)
  • Stratified = better for protection (more cells)
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17
Q

Give an example of where simple squamous epithelium is found and describe it’s function

A

Lines many body cavities e.g. found in the lining of alveoli of lung tissue. Also the endothelium (epithelium lining the entire vascular system/blood vessels/capillaries = exchange of nutrients & wastes between blood and tissue)
- Single layer of flat cells with a central disc shaped nuclei
- Allows material to pass by diffusion & filtration in sites where protection is not important

18
Q

Give an example of where simple cuboidal epithelium is found and describe its function

A

e.g. lining kidney tubules, ducts and secretory portions of small glands
- Single layer of cube like cells with large, spherical central nuclei
- Function: secretion & absorption

19
Q

Give an example of where simple columnar epithelium is found and describe its function

A

e.g. non-ciliated lines most of the digestive tract (stomach to rectum) & ducts of some glands; ciliated lines respiratory tract and uterus
- Single layer of tall cells with oval nuclei located near basement membrane. Some cells have cilia or microvilli; may contain mucus secreting unicellular glands (goblet cells)
- Function: (microvilli) absorption of nutrients; secretion of mucus, enzymes & digestive fluids; ciliated type move materials (mucus or eggs) by cilary action

20
Q

Give an example of where stratified squamous epithelium is found and describe its function

A

e.g. lining oesophagus, mouth & vagina; keratinised type in epidermis of skin & outer surface of cervix
- Thick (several layers of flat cells). Basal cells are cuboidal or columnar, metabolically active, divide & produce cells of more superficial layers. In keratinised type, surface cells are full of keratin and dead
- Function: protects underlying tissues against abrasion, pathogens & chemical attack

21
Q

Give an example of where stratified cuboidal epithelium is found and describe its function

A
  • Generally 2 layers of cuboidal cells
  • Location: (rare) : lines lumen of mammary glands and sweat glands
  • Function: secretion
22
Q

Give an example of stratified columnar epithelium and describe its function

A
  • Several layers of cells in which basal cells are cuboidal and superficial cells are columnar
  • Locations (rare): large ducts of mammary glands, salivary gland ducts and urethra
  • Functions: secretion & protection
23
Q

What is the difference between pseudostratified columnar epithelium and transitional epithelium?

A
  • Pseudostratified columnar epithelium appears stratified but is not!
  • Transitional epithelium : surface cells are dome shaped/flat (depending on stretch of bladder). Basal cells are cuboidal/columnar
24
Q

Explain the description, function & location of pseudostratified columnar epithelium

A

Description: single layer of cells (some tall, some short); all in contact with basement membrane; some not reaching the free surface; nuclei seen at different levels; may be ciliated
Function: secrete substances, particularly mucus; movement of mucus by ciliary action (mucus traps dust in trachea)
- Location: lines part of the male reproductive tract & the respiratory system e.g. trachea

25
Q

Explain the description, function & location of transitional epithelium

A

Description: several cell layers. Basal cells cuboidal or columnar; surface cells dome shaped or flat (depending on degree of organ stretch)
Function: stretches to permit extension of urinary bladder
- Location: lines urinary bladder
- Is designed to distend & return to normal size (reduced function with age)
- In empty bladder: epithelium is thick & multilayered, with rounded, dome like cells on luminal surface
- In full bladder: epithelium stretches & thins out (squamous cells)

26
Q

What are glands?

A

Specialised epithelial tissue structures that secrete substances e.g. mucin, hormones, enzymes, electrolytes & waste products

27
Q

Is secretion an active or passive process?

A

Active: glandular cells obtain substances from blood & transform them chemically into secretion product

28
Q

What organelles/structures are most prominent in glandular epithelial cells?

A

ER; Golgi apparatus & secretory granules

29
Q

How are glands classified?

A
  • By site of product release (endocrine: internally secreting into tissues/exocrine: externally secreting inside body cavity e.g. stomach or surface of skin)
  • By relative number of cells forming the gland: unicellular (goblet cell) or multicellular (duct)
30
Q

Describe endocrine glands

A
  • Secrete products hormones directly into extracellular space (by exocytosis)
  • Hormones enter blood or lymphatic fluid & travel to target organs
  • Target organs respond in some characteristic way
  • Ductless glands: secretions not released into a duct
  • e.g. thyroid gland
31
Q

Describe exocrine glands

A
  • Secrete products onto body surfaces (skin) or into body cavities
  • More numerous than endocrine glands
  • Secrete products into ducts (except for goblet cells - unicellular glands)
  • Unicellular or multicellular
  • e.g. sweat and salivary glands, liver (secretes bile), pancreas (secretes digestive enzymes)
32
Q

Describe goblet cells (in unicellular exocrine glands)

A
  • Found in epithelial linings of digestive & respiratory tracts
  • Produce mucin: complex glycoprotein that dissolves in water to form mucus
  • In digestive tract: mucus blocks microorganisms toxins, bacteria, digestive enzymes
    In respiratory tract: mucus traps dust particles, bacteria & other inhaled debris; cilia move the mucus towards the pharynx to be swallowed = protects lungs from infections
33
Q

Explain the composition & function of multicellular exocrine glands

A
  • Are composed of a duct & a secretory unit (secretory cells)
    Formed by invagination of epithelium into underlying connective tissue
  • Formed by invagination of epithelium into underlying connective tissue
  • Connective tissue provides support & nutrients to glands (blood vessels)
  • Classified by mode of secretion…
34
Q

Describe & explain the classifications of exocrine glands by mode of secretion

A
  • Merocrine glands: most - secrete products by exocytosis (sweat glands, salivary glands & pancreas)
  • Apocrine glands: a portion of membrane buds off the cells containing the secretion (mammary glands)
  • Holocene glands: the entire cell disintegrates to secrete its product (sebaceous glands)
35
Q

Describe the process of bone turnover

A
  1. Resorption : osteoclasts break down bone creating a resorption cavity
  2. Reversal
  3. Formation : osteoblasts make new bone matrix which is then mineralised, filling the remodelling space
  4. Resting

Enables bone to :
adapt to mechanical loading
repair damage
regulate circulating Ca levels
contribute to acid/base balance (osteoclasts are sensitive to this)

36
Q

How does bone mass change with ageing?

A
  • up to around age 25 = attainment of peak bone mass
    PBM = up to 35 years old.
  • consolidation period (between age 25-40)
  • age related bone loss from age 40 + menopause
37
Q

What is the homeostatic level of Ca in blood? What factor is important in the absorption of calcium?

A

10mg/100mg of blood

Vit D

38
Q

Explain how measures of bone density (T scores) vary

A

Normal T score = above -1
(normal is measured by no. of SD away from standard healthy adult)
Osteopenia = (low bone mass) -1 to -2.5
Osteoporosis = -2.5 and below

39
Q

What lifestyle advice is to be given to prevent/treat low bone mass?

A

vit D + calcium supplement (when shadow is longer than height, no vit D is made)
Protein (importance of avoiding low intake)

40
Q

What does vitamin D deficiency lead to in children and adults
What is the recommended daily supplement for vitamin D ?

A

children = rickets
adults = osteomalacia (causes bones to become soft and weak) & osteoporosis
* heart disease
* diabetes
* cancer
* TB
* the common cold

10ug Per day supplement

41
Q

What are the main calciotrophic hormones?

A
  • calcitonin = works if Ca levels in blood are too high
  • calcitriol = works together with PTH if Ca levels are too low
42
Q

Give examples of connective tissue diseases

A
  • Rheumatoid arthritis
    (inflammation of the synovial tissue with synovial proliferation. Symmetric involvement of peripheral joints, hands feet and wrists)
  • Systemic lupus Erythematosus
    (Imflammatory autoimmune disorder affecting multiple organ systems)

BMS1060 (10 decks)

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