Lungs Flashcards
Components of Respiratory system
- Lungs
- Conducting airways
- Central Nervous system
- Chest wall
- Muscles of respiration
Lung structure
- Right - 3 lobes (upper/middle/lower) - divided by horizontal and oblique fissures respectively
> 10 bronchopulmonary segments - Left 2 lobes (upper/lower divided by oblique fissure)
> smaller to make room for heart
> middle area = lingula area - allows comparison to right lung
> 8 bronchopulmonary segments (may combine to make 10 for comparison) - Surrounded by pleura - visceral (outer) and parietal (inner) with fluid between to reduce friction
> negative pressure between pleura help keep them together and lungs inflated
Position of the lungs
Superiorly: ~2.5cm above midline of medial 1/3 clavicle
Anteriorly: 6th costal cartilage ~7cm from midline
Laterally: rib 8
Posteriorly: T2-T10
Functions of the lungs
- Gaseous exchange
- produce surfactant (keep alveoli open)
- blood reservoir
- filter (between us + outside world)
- immune system (nose + mouth/mucosal elevator/immune cells)
- pH balance - CO2 levels in body
Upper + Lower respiratory tracts
> Upper - Nose - Mouth - Pharynx (throat) - Larynx (voice box) (Moisten air/ filter particles/ swallowing/voice) > Lower - Trachea - Primary Bronchi - Secondary bronchi - Tertiary bronchi - Bronchioles - Terminal bronchioles - Respiratory Bronchioles - Alveolar ducts - Alveolar sacs
Trachea
> immediately below larynx - C6 > 2.5 cm in diameter, 11cm long > 15-20 C shaped cartilaginous rings (gap posteriorly for oesophagus flexibility) > divides into 2 at CARINA = T5 level Pathologies - floppy - no cartilage - obstruction - cancer
Primary Bronchi
> right and left (separated by carina) > C shaped cartilaginous supports > right = larger + at sharper angle > Access the lungs at HILUM Pathologies - obstruction - cancer
Secondary Bronchi
> Lobar ie right has 3, left has 2
Cartilaginous plates for support
Pathologies
- Pneumonia
Tertiary Bronchi
> Segmental ie. right has 10, left has 8/9
Cartilaginous plates (less than secondary)
more smooth muscle - support but tension increases resistance to airflow
Pathologies
- Infection = bronchitis
Bronchioles
> more smooth muscle than cartilage
Pathologies
- Fibrosing alveolitis
- COPD
Terminal bronchioles
> 0.3 - 0.5 mm in diameter > smooth muscle (regulated by ANS) Pathologies - Asthma - fibrosis
Respiratory bronchioles
> each terminal bronchiole has several respiratory
thin + delicate
no cilia (inflammatory/immune responses only)
Deliver air to gas exchange surfaces
Alveolar ducts
> connect respiratory bronchioles to alveoli
Pathologies
- cystic fibrosis
- pneumonia
Alveolar sacs (300 million
> gas exchange site (type 1 pneumonocyte - aids gases across membrane
surfactant (type 2 pneumonocyte) - hydrophilic head attracted to wall and pushes open + hydrophobic tail provides dry are for gas exchange
mesh like capillary network
Pathologies
- cystic fibrosis
- pneumonia
Collateral Ventilation
> channels between alveoli and respiratory bronchioles
- channel of martin - intrabronchiolar
- channel of Lambert - bronchiole - alveolar
- Pore of kohn - interalveolar
- blockage doesn’t null alveolus
> if alveoli collapse - v.high pressure is needed to re-open which will likely damage other alveoli
RESIDUAL VOLUME - keeps alveoli open with help from collateral channels + surfactant
Zones of respiratory tract
Conducting Zone (generations 0-16) - Trachea - Terminal bronchioles - no gas exchange - gas travels by convection ANATOMICAL DEAD SPACE
Respiratory zone (generations 17-23) - respiratory bronchioles - alveoli - gas exchange (large sa) - gas travels by diffusion PHYSIOLOGICAL DEAD SPACE
Circulatory system of lungs
Pulmonary
- gas exchange
- low pressure - slow speed to maximise exchange
Bronchial
- supplies lung tissue
- low pressure for small vessels (higher than pulmonary)
Mechanics of breathing
IN
> diaphragm contracts + flattens (75% of work)
> external intercostals contract - ribs move up + out
forced inspiration: sternocleidomastoid/scalene/pec minor/serratus anterior
OUT
> diaphragm relaxes - increasing pressure
> ext intercostals relax - ribs move down + in
forced expiration: internal intercostals/Transverse thoracis (depress ribs) / abdominals (compress abdomen)
Normal breathing
> 12-18 breaths per minute
active inspiration (both voluntary + involuntary control)
passive expiration
ratio of inspiration 1:2 expiration (time to move air)
Tidal volume = air moved in one breath
Both intrapulmonary(within airways) and intrapleural (between membranes) pressure decreases with inhalation and increases with exhalation
Compliance
> expandability of lungs
measured as Change in Volume/Change in Pressure
reduced compliance:
- atelectasis - collapse of small airways in an area
- fibrosis - stiffening of lung tissue
- obesity
Resistance
> resistance to flow of air
either airway (80%medium,20 small) or tissue resistance
Factors
- lung volume
- contraction of smooth muscle
- obstructions (tumour/sputum)
- tissue resistance (elastic properties of lungs + chest wall)
- type of airflow (due to different pressures
a) Laminar (small airways) - more organised + slow
b) Turbulent (large) - disorganised + faster
c) transitional (medium, branch points) - mix of 2
Elastic resistance
Elastic recoil
Work of breathing
> Elastic resistance - measure of work exerted by inspiration muscles to expand lungs
Elastic recoil - ability of lungs to rebound
Work of breathing - physical work of muscles of respiration to overcome resistance (elastic + non-elastic)
- increase with respiratory load due to
a) poor compliance
b) increased resistance
c) respiratory capacity
d) more elastic resistance
Ventilation sequence
- respiratory centre sends message to initiate breath
- muscles of inspiration begin to contract
- diaphragm contracts + descends
- rib cage moves up + out - thoracic volume increases
- intrapulmonary pressure drops
- pleural pressure becomes more negative
- intrapulmonary pressure < atmospheric pressure
- air is moved into lungs until equilibrium
- air movement stops
- respiratory centre stops initiation message
- respiratory muscles relax
- diaphragm relaxes + moves up
- rib cage moves down + in
- lungs recoil
- intrapulmonary pressure rises
- intrapleural pressure = less negative
- air leaves lungs
