Thoracic Cage and Diaphragm

Question 1

Bones of the thoracic cage

Answer 1

Sterum
- Manubrium, body, xiphoid process
Ribs (12 pairs) and costal cartilages
- True > ribs 1-7; direct attachment via their own costal cartilage
- False > ribs 8-10; each costal cartilage joins to the costal cartilage superior to it
- Floating > ribs 11 and 12; rudimentary cartilage does not attach to sternum
Thoracic vertebrae and discs

Question 2

Apertures

Answer 2

-Superior thoracic aperture
-Inferior thoracic aperture
-Intercostal cartilages

Question 3

Typical ribs (3rd to 9th)

Answer 3

Head- 2 facets for articulation with 2 adjacent vertebrae
Neck
Tubercle- smooth facet for articulating with corresponding transverse process/ rough & non-articular part for ligament attachment
Shaft- costal angle; costal groove on internal surface

Question 4

Atypical ribs

Answer 4

Rib1- single facet on head for articulation with T1 only
Rib 2- wider, more curved and shorter than typical ribs
Rib 10- single facet on head for articulation with T10
Rib 11 &12- do not attach to costal margin/ single facet

Question 5

Joints of the thoracic cage

Answer 5

Sternal Joint
Manubriosternal Joint
-secondary cartilaginous joint (symphysis)/ slightly mobile
-contributes to transverse thoracic plane
Xiphisternal joint
-primary cartilaginous (synchondrosis)
-slightly mobile until ossifies

Question 6

Between costal cartilages and sternum

Answer 6

Sternocostal joints
-Rib 1 costal cartilage and manubrium (synchondrosis, almost immobile, has costoclavicular ligament support)
-Rib 2-7 costal cartilage and sternum (synovial plane joints, small range of gliding in respiration)

Question 7

Between ribs and costal cartilages

Answer 7

Costocondral joints- synchondrosis, immobile
Interchondral- synovial plane joints between costal cartilages

Question 8

Joints between vertebrae and ribs

Answer 8

Costovertebral Joints
-synovial plane joint
-radiate ligament

Costotransverse joints
-synovial plane joint
-tubercle of rib with transverse process of corresponding vertebra
-costotransverse ligament

Question 9

Intercostal Muscles

Answer 9

1. External Intercostal
   -Oblique fibres running anteroinferiorly from superior rib to inferior rib
   -Anteriorly, muscle fibres replaced by external intercostal membrane
   -Elevate ribs= inspiration
2. Internal Intercostal
   -oblique fibres running posteroinferiorly from superior rib to inferior rib
   -posteriorly, muscle fibres replaced by internal intercostal membrane
   -depress ribs= expiration
3. Innermost intercostals
   N.B- Intercostal muscles have an important role in stabilising the thoracic wall- prevent collapse of intercostal spaces with intrathoracic pressure changes during respiration

Question 10

Diaphragm

Answer 10

-Double dome shaped muscle that seals the inferior thoracic aperture
Attachments:
Vertebral (lumbar vertebrae- left and right crus)
Costal (ribs and costal cartilages 7-12)
Sternal (xiphoid process)
Arcuate ligaments

Question 11

Apertures of the diaphragm

Answer 11

1. Caval opening for inferior vena cava
   T8 vertebral level/ through central tendon
2. Oesophageal hiatus for oesophagus
   T10 vertebral level/ through musculature part
3. Aortic hiatus for abdominal aorta
   T12 vertebral level/ passes posterior to diaphragm

Question 12

Arterial supply of posterior thoracic wall

Answer 12

Posterior intercostal arteries
-Located between internal and innermost intercostal muscles
-Supplies intercostal muscles and overlying skin, parietal pleura
Anterior intercostal arteries
-Supply intercostal spaces
-Branches of internal thoracic arteries
-Supplies intercostal muscles, pectoral muscles, breasts and skin

Question 13

Venous drainage of thoracic wall

Answer 13

Anterior intercostal veins
-Drain into left or right internal thoracic vein  brachiocephalic veins  SVC
Posterior intercostal veins
-Drain into azygous venous system  SVC

Question 14

Innervation of the thoracic wall: intercostal nerves

Answer 14

-Arise from T1 to T11 ventral rami
-In neurovascular bundle between internal and innermost intercostal muscles in costal groove
Motor: intercostal muscles
Sensory: skin and peripheral part of diaphragm