Diaphragm, mechanisms of respiration and surface projections Flashcards
Describe the diaphragm
Muscular at its periphery and tendious centrally
Thin musculotendinous structure that separates the thoracic and abdominal acivities
What is the does the diaphragm close?
inferior thoracic aperture
What is the shape of the diaphragm?
J-shaped
both saggittal and transverse planes
How many domes does the diaphragm have?
2
What dome of the diaphragm is higher and by how much?
Right
1cm
In full expiration what is the upper border of the diaphragm on the RHS?
4th intervertebral space
In full expiration what is the upper border of the diaphragm on the LHS?
5th intevertebral space
What is the diaphragm attached to laterally and anteriorly?
- xiphoid process of the sternum
- deep surface of the last 6 ribs and costal cartilages (costal margin)
What is the function of the median arcurate ligament?
surrounds aorta and forms aortic hiatus
What is the diaphragm attached to posteriorly?
- Lumbar vertebrae and vertebral discs
- Right crus (L1-3)
- Left crus (L1-2)
- Median acruate ligament - medial borders of crura
- Medial acruate ligament - body to transverse process of L1
- Lateral arcruate ligament - transverse process of L1 - rib 12
Where does the diaphragm insert?
central tendon (centrum tendineum)
What is the level of the central tendon of the diaphragm?
xiphosternal synchondrosis
What sits on the central tendon?
the heart
What is the central tendon fused to and what is its function?
fused to the pericardium and halts its descent during forced inspiration
What ligaments prevent the excessive descent of the diaphragm?
pericardiophrenic ligaments
black = left crus
purple = right crus
blue = median arcruate ligament
red = lateral arcruate ligament
green = medial arcruate ligament
Describe the caval opening
- At the level of T8 through the central tendon
- Inferior vena cava
- right phrenic nerve
Describe the oesphageal opening
- At the T10 level, through the right crus
- oesphagus
- both vagus nerves
- Anterior = left vagus
- Posterior = right vagus
- left gastric vessels
Describe the aortic hiatus
- At T12 level behind the median arcruate ligament
- Aorta
- thoracic duct
- azygous and hemiazygos
What travels through the crura?
- branches of left phrenic nerve
- splanchnic nerves
- azygos and hemiazygos
What travels behind the medial arcruate ligament
sympathetic trunk
green = caval opening
red = oesphageal opening
Black = aortic hiatus
green = inferior phrenic nerve
Where are the three major openings in the diaphragm?
T8 = VENA CAVA T10 = Oesphagus
T12 = Aortic Hiatus
What is the vascular supply of the diaphragm?
- superior phrenic artery - branch of thoracic aorta (superior)
- branches of musculophrenic arteries
- branches of pericardiophrenic arteries
- inferior phrenic artery - branch of abdominal aorta (inferior)
What is the neural supply of the diaphragm?
- Phrenic nerve (efferent and afferent)
- Motor
- Sensory from central tendon, pariteral pleural and pericardium
- Intercostal nerves
- sensory from the periphery of the diaphragm
blue = phrenic nerve afferent
red = phrenic nerve efferent
green = intercostal nerves
what is Boyle-Mariotte’s law?
the absolute pressure exerted by a given mass of an ideal gas is inversely proportional to the volume it occupies if the temperature and amount of gas remain unchanged within a closed system
What is respiration
inspiration + expiration
What occurs during inspiration to the size of the thorax and the pressures within it?
- diameters of the thorax increase
- creates negative intra-thoracic pressure (less than atmopsheric pressure)
- air is sucked into the lungs
How does expiration occur?
by muscle relaxation and elastic recoil of the elastic tissue in the lungs and bronchi
What happens to the diaphrgam during inspiration?
contraction of the diaphragm flattens the domes
- domes descend
- vertical diameter increases
- volume of the thorax increases
- intrathoracic pressure decreases
- air is drawn into the lungs
What is the action of the external intercostal muscles?
as the body of the rib passes obliquely downwards, contraction of the external intercostal muscles to raise the body of the rib towards the one above lifts the sternum and pushes it anteriorly
What happens to the lung due to the external intercostal muscles during inspiration?
- the saggittal diameter increases
- volume of the thorax increases
- intrathroacic pressure decreases
- air is drawn into the lungs
What is responsible for the pump-handle movement?
external intercostal muscles
What is the direction of the costal cartilages of ribs 5 to 10?
pass obliquely upwards to the sternum
How do the external intercostal muscles affect the ribs
lefts the costal cartilages of ribs 5 - 10 lifting them and displacing the rib laterally
What diameter of the lungs are the costal cartilages responsible for increasing during contraction (inspiration)
transverse diameter
What is responsible for the bucket handle movement?
costal cartilages and external intercostals
What makes lateral splay/pump handle action possible?
the costal cartilages of ribs 4-9 lie obliquely
What rib is there no layeral movement of?
first rib
What movement occurs in forced inspiration and what is the purpose of this?
bucket-handle
get as much air into the lungs as possible
Where does the bucket-handle movement occur? And why?
ribs 8-10 that have flat costo-transverse joints that allow gliding
gives a small, additional increase in the lateral thoracic diameter and therefore volume
When are the accessory muscle of respiration used?
when more power is required
What are the major accessory muscles of respiration and what do the help with?
- pectoralis major = inspiration
- latissiums dorsi = expiration and inspiration
- abdominal wall muscles = expiration
- neck and back muscles = help fix ribs
- trapezius
- sternocleidomastoid
- scalene muscles
red = four corners of the hart
green = lungs and fissues
blue = pleura
What is the surface anatomy of the pleura?
- rise to the level of the neck of the 1st rib, 2cm above clavicle
- 2nd CC = lie adjacent in the midline
- 4th left CC = notch for the heart
- 8th rib = the midclavicular lines
- 10th rib = the mid axillary line
- T12 = mid-line
How does the surface anatomy of the lung differ from the pleura?
2 levels up from the pleura
Describe the surface anatomy of the lung
- the apex of the lung projects into the neck
- 2nd CC - lie adjacent in the midline
- 4th left CC - cardiac notch
- 6th CC - deviate laterally
- 6th rib - midclavicular line
- 8th rib = mid axillary line
- 10th rib = midscapular line and midline
What can accumuklate in the pleural recesses?
fluid
What is the costodiaphragmatic recess?
narrow potential space between the periphery of the diaphragm and the ribs
What is the oblique fissure?
curved line that begins between the spinous processes of the vertebrae T3 and T4, crosses the mid-axillary line at 5th intercostal space, and then follows the contour of rib 6
What is the horizontal fissue?
follows the 4th intercostal space from the sternum until it meets the oblique fissure as it crosses rib 5.
When does a pneumothorax occur and how does this affect the lungs?
if air enters the pleural caivty
surface tension and negative pressure are lost and the lung collapses
What occurs in the affected side of a pneumothorax?
- no thoracic movement
- flat hemi-diaphragm
- shift of mediastinum to the unaffected side
Where is the triangle of safety and what is inserted here?
- anterior border of latissimus dorsi
- lateral border of pec major
- horizontal level of the nipple
- apex below the axilla
What occurs during respiration in a frail chest?
the segment freed by fracture is sucked inwards, instead of lifting upwards
paradoxical respiration
