mechanics of breathing Flashcards
how many pairs of ribs
12
ribs derived from
paraxial mesoderm/sclerotome of somites
sternum derived from
somatopleure
3 parts of the sternum
manubrium/body/xiphoid
false ribs
share a costal cartilage with the rib above
3 pairs
floating ribs
don’t contribute to the costal margin - rib pairs 11 and 12
2 types posterior costal joints
costovertebral
costotransverse
costovertebral
synovial joint - cartilage on either side with fluid in between
rib head articulates with facet/demifacets
costotrasverse
synovial joint
rib tubercle articulates with transverse facets
facet of true rib
cup shaped - allows ribs to flare superior-laterally
articulates with transverse facet in costotransverse joint
facet of false rib
plane facet (more flat) - allows lower thorax to open out (rotate out)
facet of floating ribs
floating ribs don’t have a costotransverse joint
how many false rib pairs
3
which are false ribs
8, 9 ,10
synovial joints movement
sternocosstal joints 2-7
relatively mobile
can move in all planes, just constrained
synchrondoses
cartilaginous immovable joints
- all ribs with costal cartilages
- 1st stenrocostal joint is not mobile because it formss a fulcrum
- xiphisternal joint
1st sternocostal joint
synchrondoses joinnt
immovable
symphysis joint
cartilaginous movable joint
manubriosternal joint
manubriosternal joint
bends and flexes with respiration
sternal angle becomes more acute with inspiration
the joint bends/flexes more
pump handle movement of the chest wall
ribe 1 lifts the manubrium and pulls sternum forward
moves all true and false ribs
rotations of sternocostal joints 2-7
bucket handle movement of the chest wall
true ribs 1-7 elevate
calliper movement of the chest wall
false ribs 8-10 act on the costal margin, not sternum
widen laterally - widen costal margin
A shape becomes broader
floating ribs action
support diaphragm and spread
lengthen thorax
anchor points for other muscles to attach to
quiet - tidal respiration
inspiration - active
expiration - passive
inspiration in tidal respiration
mostly diaphragm, but also intercostals and scalenes
expiration in tidal breathing
elastic recoil of muscles and lungs, cartilages and ribs
IVC when the diaphragm contracts
widens slightly - blood flow and venous return
aorta passes through
aortic hiatus between the two crura at T 12
oesophagus passes through
muscle of the crus at T10
IVC passes through
central tendon at T8
external intercostals
situated posteriorly, don’t attach to costal cartilages
external intercostal membrane on superficial side
internal intercostals
2 types
2 types of internal intercostals
parasternal and interosseous
innermost intercostals
very similar to internals but more transverse
not continuous throughout the thorax
active during inspiration and expiration
dynamic changes in chest and compliance
intercostal space and contents
neuromuscular bundles in costal groove
deeper respiration
accessory muscles used because tidal muscles alone do not suffice
- elevate upper ribs and spread lower ribs
scalenes and sternocleidomastoid
lift the first rib or prevent depression
serrates posterior
usually very thin
superior - lift upper ribs
inferior - depress lower ribs
quadrates lumborum
holds rib 12 down
postural muscles
maximum lung volume is dependant on posture
scapular retractors and vertebral extensors
scapular retractors
trapezius, rhomboids, latissimus dorsi
vertebral extensors
erector spinal groups
forced exhalation
internal and anterior externals intercostals
abdominal wall muscles - ractus abdomens, external and intercostal oblique, transverses abdominus - flatten the abdomen and organs are pushed into the diaphragm to force it upwards
using limb muscles to breathe
pectoral girdle muscle elevate ribs if upper limbs are fixed to something
residual volume
air you cannot exhale
pluearal pressure
always negative
pleural pressure becomes more negative
during inspiration
mesothelium
is serous secreting
space in the pleura cannot be compressed
cupula recess
slightly above the first rib
1-3cm above clavicular head
costomediastinal recess
either side of the sternum, between the body wall and pericardium
3 pleural recesses
scapula
costomediastinal
costodiaphragmatic
pleural recesses exist because
the lungs cannot fill all the space they have
costodiaphragmatic recess
lungs stop higher than pleura
- lungs extend to rib 8, pleura extends to rib 10
- pleura extends to rib 12 posteriorly
clinical implications of the cupola
vulnerable in babies because of short necks
injury o lower necks may result in puncture or irritation
clinical implications of costodiaphragmatic pleura
implications for abdominal surgery
abdominal incision sites - right infrasternal angle and costovertabral angles - if pierced may cause collapse of the lung or other pathology
thoracentesis/chest tube - to sample fluid, blood or excess fluid from pleural space - need to go into the 9th intercostal space in midaxillary line (without damaging the lung)
clinical implications of costomediastinal pleural recess
pericardiocentesis - sampling/draining pericardial fluid
left infrasternal angle, whilst supine
allows safe sampling of pericardial fluid using a needle without damaging the pleura or the lung
apertures
small superior aperture and large inferior aperture
increasing venous return to the heart
when breathing in
diaphragm contracts and goes down
creates negative pressure in the thorax
helps venous return
external muscles pattern of action
posteror and superior fibres mechanically favour inspiration
anterior and inferior fares mechanically favour expiration
internal parasternal
inspiratory
internal interosseous
expiratory
pelvic floor muscles during forced expiration
pelvic floor muscle must be active and raise
pectoral girdle in inspiration
can elevate ribs if the upper libs are fixed to something
common in COPD patients
