Anatoy of the thorax Flashcards
What are your body cavities lined with?
Serous membranes
What is the serous membrane?
A layer of epithelial cells that secrete a watery fluid
* Double layer of secretory
tissue with fluid between
layers
Parts of the serous mem
- Visceral layer on the
organ - Parietal layer on body
wall
What cavities does the thoracic cavity have?
The 2 pleura + pericardium in the mediastinum
What cavity is in the abdominopelvic area
Peritoneum
What are the boundaries of the thoracic cavity?
- Anterior: Sternum
- Posterior: Thoracic
vertebrae - Lateral: Ribs
- Superior: base of neck
- Inferior: diaphragm
What is everything below the diaphragm a part of
Peritoneum
What is the parietal pleura connected to?
The thoracic wall
What is ventilation driven by?
Pressure changes
Relationship between P and V
Inverse relationship aka Boyles law
Boyles law
- Pressure measured by
collisions: - smaller space = more
collisions = increased
pressure - bigger space = less
collisions = decreased
pressure
Where will air move
To the area with low pressure
Boyles law
*Between breaths: P inside = P outside so no gradient
* Increase volume (therefore
decrease pressure) – air
flows in
* Decrease volume (therefore
increase pressure) - air
flows out
How are the ribs connected to the sternum?
Through the costal cartilage
- Hyaline cartilage
- Either synovial or cartilaginous jointsS
Sternocostal joints
- 3 joints
All Synovial
- Except 1st = cartilaginous
Why is the 1st sternocostal joint cartilaginous
To provide stability at the base of the neck under the clavicle
Costochondral joints are:
Cartilaginous joints
Interchondral joints
Joints between cartilage
- Synovial that allows for movement of the ribs
Articulations between the ribs and vertebrae are:
Synovial joints
Costotransverse
between rib and transverse
process of vertebrae
Costovertebral
between rib and body of vertebrae
1º muscles of respiration
Diaphragm and the intercostals
When are accessory muscles active
Only when needed
The diaphragm
- Sheet of skeletal muscle
- Separates thorax from
abdomen - Dome-shaped when relaxed
- Flattens when contracted
- Contraction expands thoracic
cavity, compresses
abdominopelvic cavity
1º muscle of inspiration
Intercostal muscles
Attach diagonally
between neighbouring
ribs
* External intercostals
* Lift ribcage and
expand cavity
* Inspiration- quiet and
forced
Internal intercostals
* Depress ribcage and
decrease cavity i.e lowers ribcage
* Expiration- forced only
Accessory muscles
- Several muscles i.e a group that
attach to the thoracic cage - Some accessory muscles
increase cavity volume for
forced inspiration - Other accessory muscles
decrease cavity volume for
forced expiration
What happens during inspiration
- During normal ‘quiet’
inspiration - Diaphragm contracts =
flattens - External intercostals
contract = lifts ribs - During active ‘forced’
inspiration - As above, plus
accessory muscles
contract to further
expand thoracic cavityW
What happens during expiration?
- During normal ‘quiet’
expiration - Passive process
- Diaphragm relaxes = dome
shaped - External intercostals relax =
ribs no longer lifted - During active ‘forced’
expiration - As above plus:
- Internal intercostals contract =
depress ribs - Accessory muscles contract
to further decrease cavity
volume
How do the lungs expand as the
cavity does?
- Lung tissue is elastic and
always trying to recoil - The pleura make the
lungs ‘stick’ to the thoracic
wall - Lungs expand during
inspiration - Lungs contract during
expiration
Thoracic Movement: Pleura
Visceral pleura on lungs
* Parietal pleura on thoracic wall
* Pleural fluid in between
– Slippery surface for frictionless movement against other structures
– Fluid bond causes lungs to ‘stick’ to thoracic wall
* Therefore, thoracic wall movement results in lung movement
– Increase volume of thorax increase volume of lung decrease
pressure in lung air flows in
M
Pneumothorax
- Air collects in pleural
space - The collapse of part or
the entire lung - Physical trauma or as
spontaneous response
to lung disease
