Epithelial Cells And Surface Specialistions

Question 1

What are the functions of the simple squamous epithelia

Answer 1

• Fast material exchange and barrier to fluids e.g. vasculature and lymphatic and respiratory space in the lungs.
• Barrier in the brain and CNS

Question 2

Where are simple squamous epithelium found?

Answer 2

Serosa of lungs, heart and viscera - tissue lubrication

In addition to the ones in the other flash card

Question 3

What is the function of simple cuboidal epithelium in the thyroid gland?

Answer 3

• they are bound to the thyroid gland follicles
• each follicle is spherical in shape
• the erpthelial cells synthesise thyroglobulin and store it in the centre of the follicle (colloid)
• this is the only organ that stores product outside of the cells
• reprocess the thyroglobulin to for, thyroxine (hormone) and release that into the blood

Pg18

Question 4

What are the functions of the simple cuboidal epithelium?

Answer 4

• Absorption and conduit (Exocrine glands )
• Absorption and secretion (Kidney tubules)
• Barrier/covering (ovary)
• Hormone synthesis, storage and mobilisation (thyroid)

Question 5

What is the normal transit time of a keratinocytes from basal layer to stratum corneum?

Answer 5

28-40 days

• In diseases such as psoriasis the transit time is greatly reduced about 2-4 days, such that the stratum corneum is produced in abundance as silvery scales

Question 6

What are the different cell surface specialisations?

Answer 6

• Keratin – prevents water loss and protects against abrasion
• Cilia – controls micro-movement of luminal contents
• Goblet cells – mucus secretions, moistens and lubricates
• Club cells – (previously known as Clara cells) protect bronchioles and acts as stem cells for respiratory epithelium
• Microfold cells – allows rapid sampling of gut microflora
• Stereocilia – in the auditory system coverts pressure waves into electrical signals

Question 7

What are important features of Goblet cells?

Answer 7

• lack of cilia on apical surface, they have microvilli instead
• Release of mucin through exocytosis
• water release increased by release of ions

Question 8

What do ciliated cells release and what occurs through the defiance of this release?

Answer 8

• Chloride ions into the lumen, increasing the water in the lumen.
• Deficiency of chloride ion release
  • results in very sticky and immovable mucous
  • characteristic of cystic fibrosis due to mutation in the CTFR gene

Question 9

What are the clinical correlates of cystic fibrosis?

Answer 9

Occurs in all tissues with mucin sand cilia

Airways
• clogging and infection of bronchial passage with thick sticky mucus obstructs breathing, progressively damages lungs – major cause of mortality in CF patients

Liver
• the small bile duct becomes blocked, disrupts digestion in 5% of CF patients

Pancreas
• zymogen secretions not released in 85% of patients

Small intestine
• thick, non-motile stools in 10% of CF neonates - requires surgery

Reproductive tracts
• absence of fine ducts such as vas deferens renders 95% of CF males infertile. Occasionally, a thick mucous plug in cervix prevent semen transit and results in female infertility.

Skin
• malfunctioning of sweat glands results in very salty sweat and crystals on the surface of the skin

Question 10

Where are Club (Clara) Cells found and what are their functions?

Answer 10

Found on the airway side of the terminal bronchioles and have club like apical surfaces as they have no cilia and no basal bodies.

1. Protect bronchiolar epithelium - club cell secretory protein uteroglobin, and a solution similar in composition to pulmonary surfactant ( a solution containing different proteins that allow the efficient gaseous exchange because they bring down surface tension)
2. Detoxify harmful substances inhaled into the lungs - Club cells accomplish this with cytochrome P450 enzymes
   found in their smooth endoplasmic reticulum.
3. Act as stem cells - They multiply and differentiate into ciliated cells to regenerate
   the bronchiolar epithelium.

Question 11

Where are microfolds found ?

Answer 11

Only in the small intestines and very close to lymphatic nodules

Question 12

What occurs in Microfold (M) cells?

Answer 12

1. Trap pathogens and other molecules
2. Present to underlying dendritic cells that process material and
3. Present to lymphocytes and macrophages that reside in a basal ‘pocket’ that is not linked to the basement membrane to raise an immune response or digestions, respectively

Question 13

What is the disadvantage of the M cells?

Answer 13

• Even though they generate important and strong immune response, they also represent a weak point in the intestinal epithelium as many pathogens exploit them as portal of entry

Question 14

Where are stereocilla found and what are their functions in these areas?

Answer 14

• In the inner ear - stereocilia are the mechanosensing organelles of hair cells, which respond to fluid motion for hearing and balance
• In the epididymis and vas deferens - stereocilia facilitate absorption of the residual sperm body after spermiation has completed

Question 15

What do stereocilia contain ?

Answer 15

• Stereocilia contain actin and myosin filaments (just like cilia)

Question 16

What occurs in the early stages of smoking to the airway epithelium?

Answer 16

1. Normal mucus layer thickens (5 microns to 10 microns)
2. Cilia die off
3. Ciliagenesis (regeneration of cilia) - 2 to 4 days

• If someone stops smoking the mucus layer is lost because they coughed it up
• The mucocillary escalator works and cilia is regenerated in 2-4 days

Question 17

What occurs in the chronic stage of smoking to the airway epithelium?

Answer 17

1. Goblet cells and basal cells proliferate - to try to get the mucocillary escalator working again
2. Club cells (metaplasia) or die
3. Carcinogens induce mutations and malignancy
4. Pneumocytes in the alveoli die
   • Remaining type II cells proliferate to make both type I and II pneumocytes
   • Fibroblasts lay down scar tissue - the epithelial cell finds it difficult to repopulate over the scar tissue

Question 18

What are the cell renewal rates in the trachea, alveoli, goblet cells and club cells?

Answer 18

Trachea - 1 to 2 months
Alveoli - 8 days
Goblet cells - 10 days
Club cells - never (once they die or undergo morphogenesis)

Question 19

What are the five common respiratory conditions related to smoking?

Answer 19

1. Acute bronchitis
2. Chronic bronchitis
3. Emphysema
4. COPD
5. Asthma

Question 20

What occurs in Acute bronchitis?

Answer 20

Cough and mucus production, breathlessness < 3 months

Reduced lung function and breathlessness due to inflammation, swelling and narrowing of the lung airways and excess mucus in the lung passages.

Question 21

What occurs in Chronic bronchitis?

Answer 21

Chronic inflammation of the bronchi and bronchioles that produces a cough and mucus production that has at least 2 episodes of cough lasting 3 months or more during a 2 year period (smoker’s cough)

• Reduced lung function and breathlessness due to inflammation, swelling and narrowing of the lung airways and excess mucus in the lung passages
• Start of or irreparable damage to the bronchioles and alveoli

Question 22

What occurs in Emphysema?

Answer 22

Shortness of breath due to permanent widening of the airspaces distal to the terminal bronchiole without fibrosis (i.e. destruction of the air sacs).

•Damage to air sac, loss of elastic recoil and permanent changes to the size of the alveoli (fuse and enlarge).

Question 23

What occurs in COPD

Answer 23

Chronic obstructive pulmonary disease – umbrella condition that includes both emphysema and chronic bronchitis

Question 24

What occurs in Asthma?

Answer 24

• Wheeze, shortness of breath, chest tightness and cough that may vary over time and in intensity, together with variable expiratory airflow limitation (often has a trigger, e.g. cold, exercise, allergens, stress, etc.).
• Caused by bronchospasm (tightening of the smooth muscle layer in the bronchi and bronchioles), obstruction from mucus and narrowing of the conducting airways.