22 Flashcards
Three intercostal muscles
- external (superficial)
- internal
- innermost (deep)
Features of the external (superficial) intercostal muscles. (Fibre direction, what do they contract to do?)
- fibre direction (viewed laterally): anteriorly, inferiorly
- contract to lift thoracic cage = inspiration
Features of internal and innermost interconstal muscles (fibre direction, what do they contract to do)
- fibre direction (viewed laterally): psoteriorly, inferiorly
- contract to lower thoracic cage = forced expiration
What is the nervous innervation of the intercostal space
- innervate by intercostal nerves
- accompany blood vessels (intercostal artery, vein) - all run together
- located between internal and innermost
Where do the intercostal nerves branch from
The ventral ramus of spinal nerves
What do the intercostal nerves supply?
Intercostal muscles, skin and parietal pleura
Vasculature of the intercostal space
- intercostal arteries
- intercostal veins
(Have an anterior supply, come off anterior blood vessels and move latterly and come off posterior blood vessels and move laterally at each intercostal space?)
ANASTOMOSE LATERALLY
Anterior and posterior intercostal arteries - where are they derived from, flow list.
Anterior intercostal artery
Subclacian artery —> internal thoracic artery —-> anterior intercostal artery
Posterior intercostal artery
Thoracic aorta —-> posterior intercostal artery
Anterior and posterior intercostal veins, where are they derived from, flow list
Anterior intercostal vein —> internal thoracic vein —> brachiocephalic vein
Posterior intecostal vein —> azygos system (depends on location)
What is the azygous system
- anastomotic pathway to drain blood from body wall to superior vena cava
What is the azygous system
- anastomotic pathway to drain blood from body wall to superior vena cava
Azygous vein?
- manage drainage of the right
- drains into the superior vena cave
Hemiazygous vein
Drains the lower half of the left hand side of the posterior thoracic wall
- this then drains into the azygous vein
Accessory hemiazygous vein?
Manages drainage on the left of the posterior thoracic cavity
- drains into the azygous vein
What is the endothoracic fascia?
- connective tissue (loose) later with variable amounts of adipose
- between intercostal muscles and the parietal pleura
Where is the endothoracic fascia
- lines inner wall of thorax, external to pleura
- extends over cupola of the pleura as “suprapleural membrane”
- thin layer between diaphragm and pleura
The endothoracic fascia can as as a…
Cleavage plane for surgery
Order of structures from skin to visceral pleura
3 surgical approaches to the thoracic cavity
- Intercostal space (lateral approach) “thoracotomy”
- need to be carpal to not go too far and damage pleura
- good cos u dont put stability of whole thoricic cavity at risk but likely to hurt nerves and arteries - Rib bed (lateral approach) - rib transection “costal resection”
- cut out some rib - Sternum (anterior approach) - sternal transection “sternotomy”
- split longnatudianlly through the body of the sternum to approach contents of mediastinum
The diaphragm fills the…
Thoricic aperture
What seperates the thoracic from abdominopelvic cavity
Diaphragm
Muscle fibre of the diaphragm
- radiating muscle fibres radiating out of the central tendon
Central tendon and the diaphragm has attachments to…
Stentum, costal and lumbar
Shape of the diaphragm when relaxed vs contracted
- dome-shapes
- flat
Nervous innervation of the diaphragm
Phrenic nerve (comes from 345 cervical spine)
(345 keeps they diapharm alive)
Blood supple of the diaphragm
Internal thoracic artery
3 apertures of the diaphragm
- aortic hiatus
- vena cabal foramen
- oesophageal hiatus
Where is the aortic hiatus and what passes through it?
- T12
- descending aorta, thoracic duct, azygous vein
(Posterior)
Where is the vena caval foramen located and what passes through it
- T8
- inferior vena cava
(Medial)
What is the oesogeal hiatus and what passes through it
- T10
- oesophagous, vagus nerve
(Interior)
Process of inspiration
- external intercostal muscles contract
- rib cage rises and expands
- diaphragm contracts to become flattened
- thoracic cavity volume increases
- lungs stretch
- lung (intrapulmonary) volume goes up
- intrapulmonary pressure goes down
- airflows down the pressure gradient moving into the lungs
What happens during expiration
- external intercostal muscles relax (Internal intercostal muscles contract during forced expiration only)
- rib cage descends and reduces
- diaphragm relaxes and rises, becomes dome-shaped
- lungs recoil and thoracic cavity volume decreases
- lung (intrapulmonary) volume goes down and intrapulmonary pressure goes up
- air flows down the pressure gradient, which is now higher inside than out, so air moves out of the lungs
What happens during expiration
- external intercostal muscles relax (Internal intercostal muscles contract during forced expiration only)
- rib cage descends and reduces
- diaphragm relaxes and rises, becomes dome-shaped
- lungs recoil and thoracic cavity volume decreases
- lung (intrapulmonary) volume goes down and intrapulmonary pressure goes up
- air flows down the pressure gradient, which is now higher inside than out, so air moves out of the lungs
