Pleura and Lungs Flashcards
3 cavities of thorax
Left Pleural cavity - left lung
Right pleural cavity - right lung
Mediastinum - between the 2 pleural cavities
What’s in the mediastinum
Trachea, heart, oesophagus, blood vessels, nerves
Development of lungs and pleura
development begins in 4-6 week old embryos from the endoderm layer
Endoderm continues to divide into out-pouches called lung buds that push out
Rapid division of the airways
Lungs push out into the primitive thoracic cavity and take visceral pleura with them
pericardioperitoneal cavity
primitive thoracic cavity
2 layers of pleura
Visceral - covers the lungs
Parietal pleura
Between pleura
Pleural cavity
Visceral Pleura
Sticks to lungs and fissures
Creates smooth surface
Connects parietal pleura and the hilum of the lung
Primary bronchus enters here
Parietal Pleura
Divided into 4 parts
- Costal (internal rib cage)
- Mediastinal (lateral wall of mediastinum)
- Diaphragmatic ( superior diaphragm)
- Cervical (cervical region)
Pleural Cavity
There is a thin layer of serous fluid which allows the pleura to slide against each other
Surface tension of the serous fluid = cohesion to help the lungs be held against the thoracic wall
Recess
Costomediastinal recess - where the heart sits so parietal pleura goes over the visceral pleura
Costodiaphragmatic recess - natural recess at the inferior end of the pleural cavity
Pleural Innervation:
Parietal
Cervical - 1st intercostal nerve
Costal - intercostal nerves
Mediastinal - phrenic nerve
Diaphragmatic - lower intercostal and phrenic nerves
Pain sensitive
Pleural innervation:
Visceral
Autonomic nervous system - from pulmonary plexuses
No pain sensitivity cos don’t have any sensation nerves
What’s in the lungs?
Apex
Base - in contact with the diaphragm
lobes created by fissures (pulmonary ligament holds up the lower lobe)
Surfaces on the lung
Costal - in contact with rib
Mediastinal
Diaphragmatic
Borders of the lung
Anterior, inferior, posterior
Right lung
3 lobes: Superior, middle, inferior
2 fissures: Horizontal, oblique (inferior superior split)
Is the larger, heavier, shorter and wider than left
Shorter cos liver is encroaching onto the inferior aspect
Left lung
2 lobes: superior and inferior 1 fissure: oblique Cardiac notch Lingula - drapes over heart 2 lobular bronchi
Hilum
Formed by structures from mediastinum entering the lungs:
Main bronchus
Pulmonary artery (superior)
Bronchial arteries and veins - supply lung tissue
Pulmonary plexus of nerves - plexus of nerves from autonomic nervous system
Lymph vessels and nodes
Pulmonary circulation
De-oxygenated blood from right ventricle enters lung via right pulmonary artery
Oxygenated blood returns to left atrium via left or right superior or inferior pulmonary veins
Bronchial circulation
Bronchial arteries supply O2/nutrients to lungs and visceral pleura
Left arteries branch from descending aorta
Right arteries branch from intercostal arteries
Bronchial veins terminate in the azygous veins
Respiratory tree
Trachea –> primary bronchi –> secondary bronchi (lobar) –> tertiary bronchi (segmental) –> Bronchioles –> alveolar sacs –> alveoli
Trachea
Flexible tube that rubs from larynx, runs from C6 to T4/5
Composed of c-shaped cartilage rings
Has trachealis muscle posteriorly to allow expansion
Lined by a mucus membrane and cilia - moistens and warms air as it comes in and wafts excess mucus
Bifurcates at sternal angle
Internal point of bifurcation - carina
Primary Bronchi
One for each lung, passing into lung at hilum
Right main bronchus is wider, shorter and runs more vertically
Contains cartilage
Secondary bronchi
lobar supplies one lobe each so 3 in the right lung and 2 in the left lung
Tertiary Bronchi
Each tertiary bronchus supplies a bronchopulmonary segement (aka segmental bronchi)
Bronchopulmonary segments
Usually 10 in right lung
8-10 in left lung Each one is the largest subdivision of a lobe
Supplied by a single tertiary bronchus
Receives a single branch of the pulmonary artery
Separated by connective tissue - surgically resectable/ removable in isolation
layer of connective tissue
Bronchioles
20-23 generations of conducting bronchioles
No cartilage in walls
Terminal bronchiole gives rise to several generations of respiratory bronchioles
Respiratory bronchioles characterised by out pockets of alveoli
Alveoli
Alveolar ducts are elongated airways lined by alveoli which leads to common spaces - Alveolar sacs
Surrounded by capillaries
2 cell types of alveoli
Type 1 pneumocytes (95%)
Type 2 pneumocytes (5%) secrete pulmonary surfactant - secreted into interior of alveolus - provides cohesive ability to bring walls together
Innervation of lung:
Sympathetic:
From sympathetic trunk: fight or flight so smooth muscle dilates to let more air in
Bronchial musculature -dilates
Pulmonary vasculature -constricts
Innervation of lung: Parasympathetic
From vagus: rest and digest
Bronchial musculature -constricts cos don’t need as much air
Pulmonary vasculature -Dilates
Lymph drainage
Drains towards the hilum via bronchopulmonary nodes
3 Groups: drainage of lymph from periphery of lungs all the way up
1. Bronchial pulmonary lymph nodes
2. Where trachea splits into bronchi - bronchial tracheal lymph nodes
3. Travels up to the paratracheal lymph nodes - either side of trachea
Eventually drain into venous system of subclavian veins
Anything pathological may flow through the lymph nodes going up
