Lecture 1 - Mechanisms Of Breathing

Question 1

Glottis

Answer 1

• the border between upper and lower airways
• functions as a sphincter
• useful for valsava maneuvers

Question 2

Paranasal sinuses

Answer 2

• make head lighter
• acoustic sound when we talk
• filled with fluid
• maxillary sinuses can become blocked - pain because most of the sinuses drain to that one place

Question 3

Airways

Answer 3

• branch dichotomously
• bronchiectasis and bronchitis are diseases of the bronchi
• roughly 30 airway branches
• bronchioles are supported by incomplete, cartilaginous rings
• bronchioles and alveoli both participate in gas exchange

Question 4

Airway organisation

Answer 4

• 27 generation of assymetrically branching airways
• Generation 0 : trachea
• Generation 1: main bronchi
• Generation 2: segmental bronchi
• Generation 3: terminal bronchi

Question 5

Right vs left lobe

Answer 5

• 3 right lobes: upper, middle and lower

- 2 left lobes + Lingula in the upper lobe

Question 6

Intrapulmonary airways

Answer 6

• bronchioles iat generation 14

- then forms acinus, where gas exchange occurs -> forms alveolar ducts

Question 7

Airway epithelial structure

Answer 7

• reticular basement membrane
• has smooth muscle
• over all of these layers is a mucus layer

Question 8

Large airway calibre

Answer 8

• normal tapering - important in clearance of mucus
• abnormal dilatation: bronchiectasis is due to abnormal mechanics during cough and deep breaths and impaired mucous clearance

Question 9

Cross sectional area of the lung

Answer 9

• exposnential increase in Surface are as you go down generatin
• central airway is point of greates resistance in our lung because flow rate is distributed evenly across thousands of bronchioles after that
• PCBV is about a wine glass spread over a tennis court: good exchange

Question 10

Flow in airways

Answer 10

• 1/2 of the total airway resistance is in the upper airway
• flow velocity in the bronchi/large bronchioles is high/turbulent - breath sound generation
• Flow velocity in the small bronchioles is laminar - no sound generation
• flow in the terminal airways occurs by simple diffusion down concentration gradient

Question 11

Clinical significance of flow regime

Answer 11

• deposition of inhaled particles: air pollution particule is very small - goes doen to alveoli whereas dust and pollen is filtrated out by URT
• deposition of inhaled medication - target aerosols to go to specific lung areas
• small airways are known as the silent zone: no symptoms until loose around 2/3 of small airway funciton

Question 12

Collateral ventilation

Answer 12

• can breath through side pores

- right middle lobe dont have much collateral ventilation -> more likely to collapse

Question 13

Mucus

Answer 13

• important protective mechanism
• increased in bronchitis because increased goblet cells, symptoms, recurrent infection, increased decline in lung function
• congenital abnormalities (Mucous motility disorders) -> recurrent LRTI

Question 14

Diaphragm

Answer 14

• central part is fibrous
• all muscle fivers contract and shorten diaphragm -> pulled down on inspiration
• very resistant to fatigue
• if breathe in and abdomen pulls in -> sign of diaphragmatic paralysis

Question 15

Plera

Answer 15

• allows lung to move freely with no friction
• lines outside of lung
• parietal pleura lines chest wall while visceral pleura lines lung
• negative pressure relative to atmosphere - passive breathing

Question 16

Pleural fluid

Answer 16

• secreted by parietal pleura
• resorbed by parietal pleural lymphatics: mediastinum and diaphragm
• turnover 50 ml/day and up to 700 ml/day
• Pain receptors: pleuritic pain