1. Christopher Ramnanan, Ph.D. cramnana@uottawa.ca
Lab 6: Thorax and Diaphragm
Thursday March 31st 2016
OBJECTIVES:
- List the parts of the sternum.
- Name the different types of ribs and their parts.
- Name and describe the importance of the inter‐costal muscles.
- Name and describe the location of the inter‐costal nerves, arteries and veins.
- Describe the innervation and vascularization of the diaphragm.
- List the three major hiatuses and the vessels that go through each .
Christopher Ramnanan, Ph.D.

2. Thoracic Cage: Sternum, 12 pairs of Ribs, 12 Thoracic Vertebrae
Focus on The Sternum
Jugular
Notch
Sternum:
Manubrium
Body
Xiphoid Process
Sternal Angle:
2nd Costal CartiIage
T4/T5 IV Disc
Bifurcation of Trachea
Azygos Arch
Aortic Arch (Lig. Arteriosum, L. Recurrent Laryngeal N.)
Sum of 2 Costal Margins: Subcostal/Infrasternal Angle
Note: Sternum articulates with ribs (via costal cartilages, sternocostal joints); manubrium makes up one boundary of the superior thoracic aperture

3. The Thorax of Infants
Before birth, the liver is a major hematopoetic organ. The liver is enlarged (relative to the anatomy of the adult), pushing the diaphragm up, and therefore making the thoracic cavity relatively small
Especially the pulmonary cavities/space occupied by the lungs

4. Thoracic Cage: Focus on Ribs
True Ribs (1-7): articulate w/ sternum via own costal cartilage
False Ribs (8-10): articulate w/ sternum via costal cartilage of rib above it
Floating Ribs (11-12): no articulation with sternum
All ribs articulate with thoracic vertebrae posteriorly

5. Features of a Typical Rib (3rd-9th ribs typical)
Typical Ribs:
-Head (2 articular facets to form joints with 2 thoracic vertebrae bodies)
-Tubercle (1 articular site to form joint with thoracic vertebra transverse process)
-Costal groove to convey intercostal neurovascular bundle

6. Atypical Ribs (Superior Views)
1st rib: shortest; broadest; most sharply curved; grooves for subclavian vessels; one articular facet on head (T1 vertebrae)
2nd rib: short and broad; rough superior tuberosity
Ribs 10-12: only one articular facet on head
Ribs 11 and 12: short; no articulation with sternum

7. Thoracic Cage: Focus on Vertebrae

8. Costovertebral Joints (Example here: 7th rib)

9. Intercostal Muscles
Transversus Thoracis
Innermost Intercostal M. ‘hands on chest’
External Intercostal M. ‘hands in pocket’
Internal Intercostal M. ‘hands on chest’
Note: These muscles are supplied by intercostal nerves, arteries, and drained by intercostal veins

11. Expiration
Inspiration
Quiet breathing
Passive recoil of lungs, rib cage
Secondary
SCM
Scalenes
Primary
External intercostals
Internal intercostals (interchondral part)
Diaphragm
Active breathing
Internal intercostals (interosseous part)
Abdominal muscles

13. Intercostal Arteries and Veins
Posterior Body Wall: Generally, Posterior Intercostal arteries supplied by thoracic aorta; Posterior intercostal veins drain to azygos system
Anterior Thoracic Wall: Anterior intercostal arteries supplied by internal thoracic a.; Anterior intercostal vein drain to internal thoracic v.
Posterior View, Ant. Body Wall

14. Intercostal Nerves Anterior Rami of T1-T11
Motor and Sensory supply to body wall (also supplies sympathetics)
Courses laterally from sympathetic trunk
Intercostal Nerve

15. Intercostal Nerve Dermatomes
Segmental Organization in Thorax T4 T5 T6 T7 T8 T9
T10
T11
T12 L1
Note: T4 and T10 landmarks

16. The Diaphragm
Central tendon
Central tendon
Diaphragm consists of central tendon (derived from cervical region in development) and lateral components (derived from body wall).
Motor: supplied by C3-C5
Sensory: centrally C3-C5; peripherally T6-T12

17. The Diaphragm
Diaphragm consists of central tendon (derived from cervical region in development, supplied by C3-C5) and lateral components (derived from body wall, supplied by T5-T12)
Central tendon
Central tendon
Caval opening (T8) in central tendon: transmits IVC, right phrenic n., liver lymphatics
Esophageal hiatus (T10): transmits esophagus and ant/post vagal trunks
Aortic hiatus (T12): transmits aorta, thoracic duct, and azygos vein

18. Origin: Ribs/Costal Cartilages, Sternum, Lumbar Vertebrae
Insertion: Central Tendon
Esophageal Hiatus
Median Arcuate Ligament: arc over aorta (unpaired)
Medial Arcuate Ligament: arc over psoas major (bilateral); sympathetic chains pass posterior to this ligament
Lateral Arcuate Ligament: arc over quadratus lumborum (bilateral)
R and L Diaphragmatic Crus: both crura form aortic hiatus and median arcuate lig.; right crus forms esophageal hiatus

19. Blood Supply Pericardiacophrenic a/v (courses with phrenic nerves)
Musculophrenic a/v (one terminal branch of the internal thoracic a/v)
Superior and inferior phrenic arteries (off the aorta either above or below the diaphragm)