The Respiratory System

Question 1

Give 3 special features of the trachea

Answer 1

The presence of large C shaped plates of cartilage

A distinct band of smooth muscle bridging the open end of the C shaped cartilage at the posterior trachea.

Abundance of mixed sero- mucous glands in the connective tissue below the epithelium with ducts linking the gland lumina to the tracheal surface
These glands help humidify the air and trap particles from inspired air

Question 2

Where is the opening of the C shaped cartilage in the trachea

Answer 2

This opposes the trachea to allow its expansion during swallowing

Question 3

What is the mechanism of coughing

Answer 3

The contraction of smooth muscle narrows the trachea by both pulling the end of the cartilage plates together and pushing soft tissue out into the lumen

This increases expired airflow to dislodge and remove any irritant particle or mucous

Question 4

What kind of cartilage is the C shaped cartilage in the trachea

What are the small cavities in the cartilage matrix

Answer 4

Hyaline

Chondrocytes

Question 5

How can you identify a bronchus

Answer 5

3 distinctive features:

• The epithelium is pseudostratified and columnar but less tall and with fewer goblet cells
• serous- mucous glands become sparse
• the bronchial cartilage framework is arranged in interconnected plates rather than C shaped rings

Question 6

How does the epithelium change down the bronchi

Answer 6

As the bronchi diameter decreases the epithelium becomes columnar with little pseudostratification

Question 7

How does the cartilage framework change as the bronchi become smaller

Answer 7

It is reduced to irregular plates and a layer of smooth muscle which separates the lamina propria from the submucosa becomes prominent

Question 8

What is the diameter of the bronchiole

Answer 8

<1mm

Question 9

How does the epithelium of the bronchioles change

Answer 9

From ciliated pseudo stratified columnar in large bronchioles to simple ciliated columnar or cuboidal epithelium in terminal and respiratory bronchioles with few/ no goblet cells

Question 10

What do the epithelia of terminal bronchioles contain

Answer 10

Non ciliated Clara cells

Question 11

Describe a Clara cell

What do they do

Answer 11

Have a round apical surface and contain dense cytoplasmic granules

Secrete a component of sufactant to cover the surface of the bronchiolar epithelium

Question 12

What is the main feature of a bronchiole

Answer 12

Smooth-muscle layer

Question 13

What happens to the smooth muscle layer of bronchioles during pathology

Answer 13

It can contract excessively in asthma causing affective collapse of the bronchioles which can seriously compromise airflow

Question 14

Do bronchioles have cartilage

Answer 14

No

Question 15

What is the alveolar septum

What is it covered by on either side

Answer 15

The thin layer between adjacent alveoli

Long respiratory epithelium
It is penetrated by a comprehensive network of blood vessels

Question 16

How can you spot the a) lung respiratory epithelium and b) blood vessels in the alveolar septum

Answer 16

a) look for nuclei

b) Look for spaces in the thickness of the wall or for trapped red blood cells

Question 17

Most of the surface of an alveolus is covered by what kind of cell

What do these look like

Answer 17

Pneumocyte type 1

Flattened cells with very thin cytoplasm that is not visible with the light microscope ( must be detected by their nuclei)

Question 18

What proportion of the epithelium is pneumocyte type 1 covering alveoli

What is the rest

Answer 18

40% but they line 90% of the alveolar surface

The other 60% is pneumocyte type 2 but these only line 10% of the alveolar surface

Question 19

Describe pneumocyte type 2

Answer 19

Larger cells with a substantial amount of cytoplasm around the nucleus.

They secrete surfactant

Question 20

Other than pneumocytes what else might be present on the alveolar surface

Answer 20

Scavenging macrophages (dust cells)

Question 21

What does surfactant do

Answer 21

Reduces the surface tension of the film of fluid which lines the alveoli, without it the alveoli would collapse and considerably increase the work of breathing

It also helps stabilise alveoli of different sizes

Question 22

What is the axoneme?

Answer 22

A central microtubular structure in cilia which is capable of generating movement independently from the rest of the cell

It consists of a peripheral rings of nine doublet microtubules and two singlet microtubules in the centre of the ring

Question 23

Other than axoneme, what else in the respiratory system has a distinct microtubular arrangement

Answer 23

Basal bodies

They have nine triplets of microtubules forming a short cylinder with no central pair

Question 24

Which pneumocyte produces surfactant

When does it begin

Answer 24

Type 2

24-28 weeks of gestation
It plays an important role in the rapid expansion of lungs at birth

Question 25

What happens to babies with insufficient surfactant quantity

How can this be treated

Answer 25

The respiratory distress syndrome develops

Surfactant administration into the lungs decreases the mortality rate

Question 26

What is surfactant

Answer 26

A mixture of lipids and protein

Its major constituent is dipalmitoyl phosphatidylcholine, a phospholipid with detergent properties

Question 27

Discuss alveolar macrophages

Answer 27

Commonly found free within the alveoli space where they play a central role in the immune processes of the lung

They engulf inhaled particulate material in the alveoli after which they usually migrate to the airways. From the airways they move up by the mucociliary escalator

Pseudopodia (extensions of the cell membrane and cytoplasm) May be present