L4 : Epithelial cells and surface specialisations

Question 1

State the characteristics of serous membranes

Answer 1

• Line certain closed body cavities (not open to exterior)
• envelop internal organs
• thin layer of connective tissue

Question 2

What is the fucntion of serous membrane?

Answer 2

secrete lubricating fluid : promotes friction free movement of structures

Question 3

Give examples of serous membranes

Answer 3

• perinoteum : envelops abdominal organs
• pleural sacs : envelops lungs
• pericardial sac : envelops heart

Question 4

What are the outer and inner walls of serous membrane called?

Answer 4

• outer : parietal serosa
• inner : visceral serosa

Question 5

Define Epithelium

Answer 5

• Sheets of contiguos cells of varied emryonic origin,
• cover the external surface of body and
• line internal surface including blood vessels

Question 6

What are the surfaces with epithelial linings for exterior, interior opened to exterior and interior not opened to exterior?

Answer 6

• Exterior : Skin
• I E : respiratory tract, GI tract, urinary tract
• I x E : peritoneum, pericardial sac, pleural sac

Question 7

What are the classifications of epithelial cell types?

Answer 7

Simple (one cell thick):

• squamous
• cuboidal
• columnar
• pseudostratified

Stratified (more than oct):

• squamous
• cuboidal
• columnar
• transitional

Question 8

State function of simple squamous epithelia

Answer 8

• fast material exchange : respiratory space in lungs
• barrier to fluids : in brain and CNS
• tissue lubrication : serous membrane

Question 9

State function of simple cuboidal epithe.

Answer 9

• Absorbtion and secretion (exocrine glands, thyroid glands, pancreatic duct, collecting duct…)
• Hormone synthesis

Question 10

State function of simple columnar epitheli.

Answer 10

• Absorption of nutrients (small intestine, colon)
• *(some contains microvilli - inc SA)
• Secretion (stomach lining, small intestine, colon)
• Lubrication (small intestine, colon)

Question 11

State the characteristic of pseudostratified epithelia

Answer 11

• All cells make contact with basement membrane
• not all cells reach epithelial surface
• nuclei at different levels

Question 12

State the function of pseudostratified epithelium

Answer 12

• Mucus secretion
• particle trapping and removal

Question 13

Where are pseudostratified epithelium located?

Answer 13

Lining of nasal cavity, trachea and bronchi

(conduction portion)

Question 14

State the function of stratified squamous non-keratinised epithelium

Answer 14

• protection against abrasion
• reduces water loss while remaining moist

Location : oesophagus, vagina, anal canal

Question 15

What is the key feature of stratified squamous keratinised epithelium?

Answer 15

Stratum corneum : consist of outermost cells which are dead, lost their nuclei and cornified.

Question 16

State the function of stratum corneum

Answer 16

• reduces water loss
• protect against abrasion
• barrier towards toxins and microbes

Question 17

Describe the process of keratinocytes maturing from basal layer to stratum corteum

Answer 17

• Stratified squamous keratinised epithelium made up of keratinocytes
• keratinoctyes undergo mitosis at basal layer
• daughter keratinocytes move towards surface, differentiating and losing ability to divide
• keratinocytes synthesis keratins(provide strength for epidermis)
• movement of keratinocytes from basal layer to stratum corteum : 28-40 days

Question 18

What are the other cells of the epidermis?

Answer 18

• Melanocytes
• Langerhans cells

Question 19

What is the function of melanocytes?

Answer 19

• produce melanin - main pigments that give skin its colour
• * darker skin, more melanin but same number of melanocytes

Question 20

What is the function of langerhans cells?

Answer 20

• present antigens to T lymphocytes
• mediate immune reactions

Question 21

How are melanin from Mature melanosomes transferred to neighbouring keratinocytes?

Answer 21

• Pigment donation - involve phagocytosis of tips of dendritic processes

Question 22

What is the function of stratified squamous keratinised epith?

Answer 22

• Protection against abration
• prevent water loss
• shielding against UV light
• prevent microbial ingress

Question 23

Where is transitional epithelium found and state its function

Answer 23

• Urinary tract
• protection of underlying tissue from toxic chemicals

Question 24

List the different types of cell surface specialisations and state each function

Answer 24

• Keratin : protects against abrasion
• Cilia : controls micro-movement of luminal contents
• Goblet cells : secretes mucus
• Clara cells : act as stem cells for respiratory epithelium
• Microfold cells
• Stereocilia

Question 25

What causes Cystic Fibrosis?

Answer 25

• Mutation in CFTR gene
• deficiancy in Cl ions release
• mucous very sticky

Question 26

What are the effects of cystic fibrosis?

Answer 26

• Airways : clogging and infection of bronchial passage, breathing obstructed
• Liver : small bile duct blocked - disrupts digestion

Question 27

State the characteristics and functions of clara cells

Answer 27

Characteristics

• on airway side of terminal bronchioles
• club like apical surfaces
• no cilia, no basal bodies

Function

• Protect bronchiolar epithelium - secrete uteroglobin
• Detoxify harmful substances inhaled into lungs
• Act as stem cells - regenerate bronchiolar epithelium

Question 28

State the characteristic and functions of Microfold cells

Answer 28

Characteristic

• Found only in small intestine, close to lymphatic nodule
• Have folded extensions

Function

• Trap pathogens and present to dendretic cells

*weakness : portal of entry for pathogens

Question 29

State the functions of Stereocilia

Answer 29

Inner ear

• mechanosensing organelles
• respond to fluid motion for hearing and balance

epididymis and vas deferens

• facilitate absorption of residual sperm body

Question 30

What are the cell renewal rates of the airway epithelium?

Answer 30

• Clara cells : never
• Trachea : 1-2 months
• Goblet cells : 10 days
• Alveoli : 8 days

Question 31

What is the effect of smoking on lungs at the early stage?

Answer 31

• mucus layer thickens
• cilia die
• ciliagenesis : 2-4 days

Question 32

What is the effect of smoking on lungs at the chronic stage?

Answer 32

• goblet cells poliferate
• clara cells die
• carcinogens induce mutations
• fibroblast lay down scar tissue

Question 33

What are the common respiratory conditions related to smoking ?

Answer 33

• Acute bronchitis
• Chronic bronchitis
• Emphysema
• COPD
• Asthma

Question 34

Describe some of the common respiratory conditions related to smoking

Answer 34

1. Emphysema :

shortness of breath - permanent widening of airspaces

2. Asthma :

• wheeze, shortness of breath, chest tightness and cough.
• Caused by bronchospasm, obstruction from mucus and narrowing of airways

3. Chronic bronchitis :

• chronic inflammation of bronchi and bronchioles.
• Reduced lung function - excess mucus in the lung passage
• irreparable damage to bronchioles and alveoli

Question 35

Describe the mucocilliary escalator in trachea

Answer 35

• mucous lining trachea traps inhaled particles
• upward beating of cilia drives debris-laden mucus towards the pharyx

Question 36

What is epithelia metaplasia

Answer 36

capacity of epithelial cell to differentiate to another cell

Question 37

What is neoplasia

Answer 37

• Changes that occur in epithelia - give rise to tumour

Question 38

What is adrenocarcinoma?

Answer 38

Tumour of epithelial origin

Question 39

How are cross sections of cuboidal and columnar cells differentiated under slide?

Answer 39

cuboidal : polygonal

columnar : hexagonal