Lecture 19: The respiratory tract

Question 1

What does the respirtory system compromise of?

Answer 1

The upper airways, The lower airways, The conducting zone, The respiratory zone

Question 1

What does the upper airways compromise of?

Answer 1

The mouth, nose, pharynx and larynx comprise the upper airways

Question 2

The lower airways…

Answer 2

The mouth, nose, pharynx and larynx comprise the upper airways

Question 3

The conducting zone…

Answer 3

The conducting zone runs from the mouth and nostrils to terminal bronchioles

Question 4

Does gas exchange occur in the conducting zone?

Answer 4

No. Only air is conducted here

Question 5

Is it true that the lower respiratory tract (lungs) causes fatal dsieases becaause gas exchange is affected?

Answer 5

Yes

Question 6

Describe the conducting zone…

Answer 6

• The conducting zone moistens
  the air and protects the lungs
• Provides a low-resistance pathway for airflow
• Does NOT contribute to gas exchange in the lung
• Warms (or cools) and moistens the air
• Defends against microbes, toxic chemicals and other foreign matter.
• The conducting zone divides significantly
  as you move down the respiratory tract

Question 7

The conducting zone extends from the trachea to the terminal bronchioles

Answer 7

The conducting zone extends from the trachea to the terminal bronchioles

Question 8

What is airway resistance in the conducting zone determined by?

Answer 8

• the total cross-sectional area
• The bronchioles have a larger cross-sectional area than the trachea

Question 9

What are the 4 levels of defence of the ariway?

Answer 9

• Constriction of bronchioles via smooth muscle
• Cilia
• Mucus
• Macrophages

Question 10

What are the cillia immobilised by?

Answer 10

Noxious agents

Question 11

Mucus works in conjunction with cilia
to provide a escalator to remove toxins

Answer 11

Mucus works in conjunction with cilia
to provide a escalator to remove toxins

Question 12

Mucus is moved from the lung to the
stomach where toxins can be neutralised

Answer 12

Mucus is moved from the lung to the
stomach where toxins can be neutralised

Question 13

What are the cillia surrounded by?

Answer 13

Proteins and sugars

Question 14

What in the alveoli acts as a last line fo defence for the lungs?

Answer 14

Macrophages in alveoli provide
a last line of defence for the lung

Question 15

Macrophages in the alveoli…

Answer 15

• Phagocytic cells that are present in the airways and the alveoli
• Engulf and destroy inhaled particles and bacteria
• Injured by noxious agents, e.g. air pollutants and cigarette smoke

Question 16

Is it true that the cillia become weaker as we get older?

Answer 16

Yes, and we struggle to beat the mucus away

Question 17

Can the macrophages in the lungs be killed by cigarette smoke and other noxious agents?

Answer 17

Yes

Question 18

Describe asthma

Answer 18

• Disorder of the conducting zone
• Causes chronic inflammation
• Reversible by using short-acting b2 adrenergic agonists
• Have a narrower lumen and thicker muscular layer in airways + overproduction of mucus in airways

Question 19

Why is their increased airway ressitance in asthma?

Answer 19

• Due to muscle constriction and mucus production

Question 20

Describe bronchitis

Answer 20

• A conducting zone disorder
• Causes persistant inflammation of the bronchia lwalls
• Excess mucus is produced
• Obstruction of the airways

Question 21

What zone is the site of gas exchange?

Answer 21

The respiratory zone

Question 22

Is it true that the respiratory zone has a large surface area?

Answer 22

Yes

Question 23

What is the role of the alveolar pores/ pores of Kohn?

Answer 23

• Pores are required to stop alveolar colapse
• The pores crosslink all the alveoli, making inflation easier

Question 24

Apart from gas exchange, what are the other roles of the respiratory zone?

Answer 24

- Provides oxygen - Eliminates carbon dioxide - Regulates the blood’s pH in coordination with the kidneys - Influences arterial concentrations of chemical messengers e.g. conversion of angiotensin I to the potent vasoconstrictor angiotensin II - Traps and dissolves blood clots arising from systemic veins

Question 25

Why are the alveoli covered in blood vessels?

Answer 25

To facilitate efficient gas exchange

Question 26

What is gas exchange in the alveoli optimised by?

Answer 26

- Thinness of barrier between blood and the air within the alveolus. - The vast surface area of alveoli in contact with capillaries. - The moist surface of the alveolar cells.

Question 27

What law is gas exchange in the alveoli determined by?

Answer 27

Fick's law

Question 28

describe Fick's law

Answer 28

- Fick’s law says that the rate of gas diffusion across a surface (like the alveoli) is proportional to: - The surface area. The difference in gas concentration (partial pressure difference). Inversely proportional to the thickness of the gas exchange surface

Question 29

Gas exchange in the lungs is highly efficient because of the large surface area, thin barrier, and strong concentration gradients, which together maximize the rate of diffusion as described by Fick’s law.

Answer 29

Gas exchange in the lungs is highly efficient because of the large surface area, thin barrier, and strong concentration gradients, which together maximize the rate of diffusion as described by Fick’s law.

Question 31

What alters ventilation and perfusion?

Answer 31

Altered by hypoxia sensing cells that constrict vessels to stop blood supplying areas with poor gas exchange

Question 32

Is it true that the pressures within the lung act to reduce ventilation-perfusion mismatching?

Answer 32

Yes

Question 33

Describe Emphysema

Answer 33

- Emphysema is a disorder of the respiratory zone - Lungs undergo self-destruction by proteolytic enzymes secreted by leukocytes - Adjacent alveoli fuse to form fewer but larger alveoli. - Reduces surface area available for gas exchange - Destruction of alveolar walls and collapse of lower airways - Increased airway resistance due to inflammation greatly increases the work of breathing.

Question 34

What is Chronic Obstructive Pulmonary Disease?

Answer 34

A combination of bronchitis and emphysema

Question 35

Is it true that COPD rates are rising?

Answer 35

Yes

Question 36

Is it true that COPD is high in areas of carbon dioxide production?

Answer 36

Yes

Question 37

To summarise, this lecture has considered: The steps of respiration Internal to external Divisions of the respiratory system and their functions Upper and lower Conducting and respiratory Defence of the airways Mucus and macrophages Disorders of the respiratory system Asthma, bronchitis, emphysema, COPD Pulmonary circulation The alveoli

Answer 37

To summarise, this lecture has considered: The steps of respiration Internal to external Divisions of the respiratory system and their functions Upper and lower Conducting and respiratory Defence of the airways Mucus and macrophages Disorders of the respiratory system Asthma, bronchitis, emphysema, COPD Pulmonary circulation The alveoli