Topic 5 - Tissue Organisation

Question 1

What holds cells together?

Answer 1

• fibres inside and outside cell in communication with each other through signalling

Question 2

Name the 5 lateral cell adhesion systems?

Answer 2

• tight junctions
• adhesion junctions
• desmosome (adhesion plaque)
• gap junctions
• cell adhesion molecules

Question 3

What are the 5 basal cell adherence systems?

Answer 3

• hemi desmosomes
• focal adhesions
• integrins
• proteoglycans
• cell adhesion molecules

Question 4

What is the role of a tight junction?

Answer 4

• to prevent movement of large molecules through the lumen into the deeper tissue layers of the organ (in the gut though it can transiently open to allow small molecules to cross - paracellular transport)

Question 5

Where are adhesion junctions found?

Answer 5

• intercellular space (between cells)

Question 6

What is the strongest of all the cell to cell adhesions?

Answer 6

• desmosome

Question 7

In which type of cell are desmosomes the only cell to cell adhesion?

Answer 7

• epidermal cells (skin cells)

Question 8

What is the function of a gap junction?

Answer 8

• to quickly communicate changes in intercellular molecular composition e.g. electrolyte and energy changes

Question 9

Where are hemi desmosomes found?

Answer 9

• on a layer of extracellular matrix (NOT on cell)

Question 10

Which cell to cell adhesion operates as an alpha, beta dimer pair?

Answer 10

• Integrins

Question 11

Which ion is key to all cell to cell adhesions?

Answer 11

• calcium 2+

Question 12

What is a mucosal membrane?

Answer 12

• lines all moist, hollow organs
• continuous with skin at various openings
• secretes mucus

Question 13

What are rugae?

Answer 13

• folds of gastric mucosa forming longitudinal ridges in stomach

Question 14

What are the 3 main functions of mucosa?

Answer 14

• absorb substances from the lumen
• prevent ingress of pathogens
• move contents and expel waste

Question 15

What are transitional epithelium in the ureter called?

Answer 15

• urothelium

Question 16

Why are there lots of fat cells in the bladder wall?

Answer 16

• provides shock absorption for expanding bladder

Question 17

Why might it be advantageous to have bladder epithelial cells produce mucus?

Answer 17

• protects bladder from damage by acidic urine

Question 18

What are the two sections of the respiratory tract known as?

Answer 18

• conducting portion

- respiratory portion

Question 19

The trachea, primary, secondary and tertiary bronchi are missing what?

Answer 19

• outer layer of smooth muscle

Question 20

Explain the mucociliary elevator.

Answer 20

In the trachea and bronchi, these things are produced:
- mucins and water (forms mucus)
- serum proteins (lubrication)
- lysozyme (destroys bacteria)
Cilia wave moves material to the oral cavity where it can be expelled or swallowed.

Question 21

What is the role of elastin fibres in the alveolus?

Answer 21

• elastic recoil of the lungs

Question 22

Explain the differences between mucous and serous membranes.

Answer 22

• mucous membranes line internal tubes that are open to the outside (e.g. GI tract) whereas serous line closed body cavities and envelop the viscera (e.g. pericardial sac that envelops the heart)
• mucous membranes are 3 layered (epithelium, lamina propria, muscularis mucosae (smooth muscle layer) whereas serous are formed of 2 layers (simple squamous epithelium, thin connective tissue)

Question 23

Explain, using an analogy, how serous membranes envelop body cavities.

Answer 23

• organ invaginates into a cavity like a fist pressing into a balloon giving an inner (visceral) and outer (parietal) membrane with a surrounding serous cavity.

Question 24

What are epithelia?

Answer 24

• sheets of neighbouring cells that cover the external surface of the body and line internal surfaces, including blood vessels.

Question 25

Define these types of epithelial tissue:

Squamous, cuboidal, columnar, transitional.

Answer 25

Squamous = squashed, flaky
Cuboidal = height roughly equals width 
Columnar = height > width 
Transitional = two forms, flits between them (relaxed and stretched)

Question 26

What are pseudostratified epithelia? And where might they be found?

Answer 26

• tissue in which all cells make contact with the basement membrane but not all cells reach the epithelial cell surface.
• nuclei lie at differing levels giving impression of multiple layers
• found in lining of nasal cavity, trachea and bronchi.

Question 27

What do melanocytes in the epidermis do?

Answer 27

• produce melanin, the main pigment that gives skin its colour
• everybody has the same amount of melanocytes but in different humans different amounts of melanin are produced giving different colours (more melanin = darker skin)

Question 28

What do langerhans cells do in the epidermis?

Answer 28

• present antigens to T lymphocytes and mediate immune reactions.

Question 29

Explain what occurs in a person with cystic fibrosis.

Answer 29

• mutation in CFTR (cystic fibrosis transmembrane regulator)
• there is a deficiency of chloride ion release which means water is not released
• leads to very sticky mucous produced

Question 30

What do club cells do on the terminal bronchioles?

Answer 30

• act like “bouncers”, protect bronchiolar epithelium (“you cant come in”)
• detoxify harmful substances inhaled into lungs (“alright buddy you’re coming with me for a little chat.”

Question 31

What are stereocilia and what do they do?

Answer 31

• mechanosensing organelles of hair cells

- respond to fluid motion for hearing and balance

Question 32

Which type of airway epithelium cell will never regenerate once dead?

Answer 32

• club cells (STOP SMOKING)

Question 33

What happens in emphysema?

Answer 33

• destruction of air sacs
• loss of lung elasticity due to tissue becoming scarred and hard
• changes to alveoli size