Epithelial cells 4

Question 1

What is the main difference between mucous and serous membranes?

Answer 1

Mucous - line certain internal tubes that open to the exterior e.g. GI tract, respiratory tract, urinary tract
Serous - thin, two part membranes which line certain closed body cavities and envelop the viscera e.g. peritoneum, pleural sacs, pericardial sac

Question 2

What envelops the heart?

Answer 2

Pericardial sac

Question 3

What envelops the lungs?

Answer 3

Pleural sacs

Question 4

What the peritoneum?

Answer 4

It is a serous membrane which envelops many abdominal organs

Question 5

What is the difference in the histological structure between a mucous membrane and a serous membrane?

Answer 5

Mucous - different types of epithelial cells depending on site, lamina propria, muscularis mucosae
Serous - simple squamous epithelium (mesothelium), thin layer of connective tissue

Question 6

What are the two layers of the serosa called?

Answer 6

Parietal (outer edge) and visceral (inner/close to organs)

Has lubricating fluid secreted by the serosa between them (serum)

Question 7

How is the plurae of the lungs attached?

Answer 7

Visceral to parenchyma, parietal to ribcage

Question 8

What is a pneumothorax?

Answer 8

The plurae of the lungs fill with air or blood

Question 9

What is the epithelium?

Answer 9

Sheets of cells which are derived from all the embryological germ layers (ectoderm, mesoderm, endoderm) which cover the external surface of the body and line internal surfaces, including the body’s vessels

Question 10

What is the only organ that stores its product outside the cells?

Answer 10

Epithelial, eg. they synthesise thyroglobulin (one of biggest proteins in humans) and store it in the centre of the follicle (colloid)

Question 11

What are the different types of epithelium?

Answer 11

Simple squamous (vasculature, lymphatics, respiratory space in lung, CNS, serosa)
Simple cuboidal (ducts, absorption, secretion, barrier)
Simple columnar (absorption, secretion, lubrication, small intestine, stomach) 
Pseudostratified (upper respiratory tract, cilia, goblet cells which secrete mucus) 
Stratified squamous (vagina, oesophagus, other areas that are moist and subject to abrasion) 
Transitional (urinary tract)

Question 12

What are pseudostratified epithelia?

Answer 12

Epithelia in which all cells make contact with the basal lamina but not all reach the cell surface. Can be multinucleate

Question 13

What does ‘keratinised’ mean?

Answer 13

Cells which have lost their nuclei and so are dead. These cells are collectively called the stratum corneum

Question 14

What is the dermis?

Answer 14

Dense irregular connective tissue, has collagen and elastin bundles going in all directions

Question 15

What is the epidermis?

Answer 15

Stratified squamous keratinised epithelium which consists mainly of keratinocytes. They make keratins (fibrous proteins) which contribute to the strength of the epidermis

Question 16

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

Answer 16

28-40 days

In eg. psoriasis it is 2-4 days so the stratum corneum is produced in abundance

Question 17

What cells are in the epidermis?

Answer 17

Mainly keratinocytes, also melanocytes (long dendritic structures, produce melanin, on basal layer, have to use special stain, all humans have the same number of melanocytes but the amount of melanin they produce determines skin colour) and Langerhans cells (use special stain, present antigens to T lymohocytes, mediate immune reactions eg. allergic contact dermatitis, on lateral side)

Question 18

What does keratin do?

Answer 18

Prevents water loss and protects against abrasion

Question 19

Where are goblet cells found?

Answer 19

Upper RT and intestines
Don’t have cilia, have microvilli
Release mucins through exocytosis

Question 20

Where are clara cells found?

Answer 20

On the airway side of terminal bronchioles
Have club like apical surfaces, no cilia, no basal bodies
Protect bronchiolar apithelium (eg by secreting uteroglobin)
Detoxify harmful substances eg CO
Act as stem cell, can turn into ciliated cells to regenerate bronchiolar epithelium

Question 21

Where are microfold cells found?

Answer 21

Small intestine, close to lymohatic nodules
AreTrap pathogens, present to underlying dendritic cells which present to lymphocytes that reside in basal pocket that is not linked to the basal lamina to reise an immune response
Have lots of folds, sample the lumen by endocytosis
Often exploited by pathogens as point of entry

Question 22

Where are stereocilia found?

Answer 22

In inner ear, they’re the mechanosensing organelles of hair cells which respond to fluid motion for hearing and balance
Also in vas deferens, help absorb the residual sperm body

Question 23

What do the cilia and stereocilia contain?

Answer 23

Actin and myosin filaments

Question 24

What happens to your airway epithelium if you smoke?

Answer 24

First - mucus layer thickens, cilia die off (2-4 days to renew)
Chronic - goblet and basal cells proliferate, clara die, carcinogens induce mutations, fibroblasts lay down scar tissue

Question 25

How long do respiratory epithelial cells take to grow back?

Answer 25

Clara - never
Cilia - 2-4 days 
Alveoli - 8 days 
Goblet - 10 days 
Trachea - 1-2 months

Question 26

What are some common respiratory conditions linked to smoking?

Answer 26

Acute bronchitis - cough, mucus increased, breathlessness due to inflammation, swelling, narrowing of lung airways, excess mucus in passages
Chronic bronchitis - same as acute but with irreparable damage, 2 episodes of 3 months of cough in 2 years
Emphysema - shortness of breath, airspaces widen, damage to alveoli
COPD - emphysema and chronic bronchitis
Asthma - wheeze, short breath, tight chest, cough, expiratory airflow limitation, caused by bronchospasm