Diaphragm; mechanisms of respiration, surface projections

complete

what is the diaphragm?

musculotendinous sheet separating thoracic and abdominal cavity

how many cm superior is the right done of the diaphragm above the left?

1cm

when maximally expired, what level does the right and left domes of the diaphragm reach?

right - rib level 5

left - 5th intercostal space

what does the diaphragm attach to?

the margins of the inferior thoracic aperture

• xiphoid process

• deep surfaces of ribs 7-12 and costal cartilages

what vertebral level does the diaphragm attach to the xiphoid process?

T8/9

what are the lumbar attachments of the diaphragm?

• right and left crura

• median arcuate ligament

• medial arcuate ligaments

• lateral arcuate ligaments

what is the median arcuate ligament formed by?

crura

what does the left crura attach to?

Vertebral bodies L1 and 2, anterior longitudinal ligament and intervertebral discs

what does the right crura attach to?

vertebral bodies L1-3, anterior longitudinal ligament and intervertebral discs

what do medial arcuate ligaments span?

L1 vertebral body and transverse processes

what are medial arcuate ligaments formed of?

thickened psoas major fascia

what do lateral arcuate ligaments span?

transverse process of L1 and tip of rib 12

what are lateral arcuate ligaments formed of?

thickened quadratus lumborum fascia

what is the insertion to central tendon?

a diaphragm attachment

what is the insertion to the central tendon continuous with?

fibrous pericardium

where does the anterior portion of the central tendon lie?

the level of xiphisternal synchondrosis

what are the three major openings in the diaphragm?

• caval opening

• oesophageal hiatus

• aortic hiatus

what is the vertebral level of the caval opening?

T8

what passes through the caval opening?

the inferior vena cava and right phrenic nerve (and some lymphatics)

why does the diameter of the inferior vena cava change during action of the diaphragm?

the IVC is connected to the margins of the caval opening

what happens to the diameter of the IVC during contraction?

it widens

what is the vertebral level of the oesophageal hiatus?

T10

what fibres have a sphincter function at the oesophageal hiatus?

fibres of the right crus

what passes through the oesophageal hiatus?

• oesophagus

• anterior and posterior vagal trunks

• oesophageal branches of left gastric vessels

what is the vertebral level of the aortic hiatus?

T12

what is the aortic hiatus posterior to?

the median arcuate ligament

what passes through the aortic hiatus?

• the aorta

• thoracic duct

• sometimes azygous and hemiazygous veins (or sometimes these go through crura)

what smaller structures also cross the diaphragm?

• left phrenic nerve

• sympathetic trunks

• greater, lesser splanchnic nerves through crura

• least splanchnic nerve behind medial arcuate ligament

• intercostal nerves

• superior epigastric vessels and lymphatics

• musculophrenic vessels

what do sympathetic trunks cross the diaphragm posterior to?

medial arcuate ligaments

where do superior epigastric vessels cross the diaphragm?

sternocostal triangle

where do musculophrenic nerves cross the diaphragm?

around 9th CC, anterolateral

what is the superior surface of the diaphragm supplied by (arterial)?

• superior phrenic ← thoracic aorta

• musculophrenic and pericardiophrenic ← internal thoracic

what supplies the inferior surface of the diaphragm (arterial)?

inferior phrenic ← abdominal aorta

what is the venous drainage of the superior surface of the diaphragm?

• superior phrenic

• some superior surface veins drain to azygous/hemiazygous (posteriorly)

what is the venous drainage of the inferior diaphragm?

inferior phrenic vein → suprarenal vein → renal vein

what is the nerve that supplies the diaphragm?

Phrenic nerve

what spinal levels are associated with the phrenic nerve?

C3,4,5

what innervation does the phrenic nerve give to the diaphragm?

• motor

• sensory to central diaphragm

also parietal pleura and pericardium

where is referred pain from the diaphragm felt?

the shoulder

what provides additional peripheral sensory innervation to the diaphragm?

• intercostal nerves (T5-11)

• subcostal nerves (T12)

what is inspiration mostly driven by at rest?

the diaphragm

what does diaphragm contraction do to thoracic volume?

increases it, drawing air into lungs

what is expiration at rest mostly driven by?

elastic recoil (largely passive)

what muscles may become involved in breathing when there is higher O2/CO2 demand?

accessory muscles

what aids smooth movement of breathing?

pleura

what happens to the diaphragm on inspiration?

• the peripheral muscles of the diaphragm contract and the domes descend

• external intercostals move ribs superiorly and laterally

which space is minimised by forced inspiration?

costodiaphragmatic recess

what can accessory muscles change and what can they not change?

• can change - force/speed of inspiration

• can’t change - volume of air inspired

what counts as accessory muscles

• SCM

• scalenes

• serratus

• pectoralis maj. and min.

• latissimus dorsi

• abdominal wall muscles

what accessory muscles act on the ribs?

SCM, scalenes and serratus

what accessory muscles act on inspiration?

pec. major and minor, latissimus dorsi

what accessory muscles act on expiration?

latissimus dorsi and abdominal wall muscles

what is the surface anatomy of the lungs and pleurae?

•Apex – 3cm superior to mid clavicle

•At parasternal line from 2^nd to 6^th CC on right

•Deviation laterally between 4^th to 6^th CC on left

what is the surface anatomy of the lungs?

•Midclavicular line – 6^th rib

•Midaxillary line – 8^th rib

•Scapular line and midline (posteriorly) – 10^th rib

what is the surface anatomy of the pleurae?

•Midclavicular line – 8^th rib

•Midaxillary line – 10^th rib

•Scapular line and midline (posteriorly) – 12^th rib

how many ribs do the pleurae add to the level of the lungs?

2 ribs

what is the surface anatomy of the oblique fissures?

• posteriorly - T3/4

• mid axillary line - 5th intercostal space

• anteriorly - following rib 6

what is the surface anatomy of the horizontal fissure?

• moving lateral from sternum - 4th rib/intercostal space

• merges with oblique fissure at 5th rib

where is the costodiaphragmatic recess?

below the lungs around periphery of diaphragm

what is the needle angled at when removing fluid from the costodiaphragmatic recess?

upwards at 9th intercostal space on midaxillary line during expiration

where is the costomediastinal recess?

behind the manubrium

why is the costomediastinal recess more pronounced on the left hand side?

cardiac notch

what partly occupies the costomediastinal recess during breathing?

the lingula

what two pleuras are involved in the costomediastinal recess?

costal pleura and mediastinal pleura

what holds the lungs in place against the thoracic wall?

surface tension of pleural fluid between visceral and parietal pleura

what happens if air enters the pleural space?

pneumothorax

what is a chest drain used to do?

evacuate air or fluid from pleural space

what could be causes fro fluid in the pleural space?

pleural effusion, haemothorax, chylothorax

what forms the anatomical boundaries of the safety triangle for chest drain?

• Anterior boundary: The lateral border of the pectoralis major muscle.

• Posterior boundary: The anterior border of the latissimus dorsi muscle.

• Inferior boundary: nipple/5th intercostal space

• Superior/Apex boundary: The base of the axilla (armpit).

what can incorrect placement of a chest drain risk?

perforating pericardium/heart/liver

what is hemiparesis of diaphragm?

one phrenic nerve stops higher

what is the cause of hemiparesis of the diaphragm?

• idiopathic

• nerve damage

what happens to the diaphragm on the affected side of hemiparesis?

diaphragm sits higher

what does flail chest occur after?

severe trauma - fracturing 3 or more ribs

what occurs in flail chest?

•“Loose” section of thoracic wall is drawn inwards upon inspiration

•Paradoxical chest wall motion