Anatomy of the Thorax
I. Boundaries of the Thorax
1. Upper boundary-
Thoracic inlet separates the thorax from the neck
Formed by sternum, first rib, first thoracic vertebra
2. Lower boundary-
Outlet
Formed by diaphragm
II. Subdivision of the Thoracic Cavity
1. Mediastinum
Superior
Inferior: anterior- little, middle- heart, posterior-
2. Pleural cavities
III. Skin
1. Clinically Important
mid-axillary line, clavicle, mid-clavicular line, costal margins, ribs, sternum, sternal angle
2. Cutaneous Innervation/Dermatones [N.150]
Dermationes are areas of the body surface supplied by a single spinal nerve
Overlap about 50%
Run horizontally at the upper thoracic levels and obliquely at the lower levels
Much of abdominal wall supplied by ant. pri. Rami of thoracic spinal n.
Dermatomes C5 to T1 mainly supply the upper extremity.
T4- nipple
T10-navel
C3 and C4-suprascapular
IV. Female Breast [N.167]
Subcutaneous and feely mobile on thoracic wall
Between ICS 2 and 6
Nipple ICS 4 on midclavicular line
Center of pigmented areola containing avelolar (Montgomery) glands
Five regions: nipple, upper outer, upper inner, lower outer, lower inner
15-20 lobes of glandular tissue each with lactiferous duct opening to nipple
Glandular tissue extends laterally forming “axillary tail”
Connective tissue ligaments (cooper) enlargement of retinacula cutis (traction on these ligaments dimpling of skin)
Sensory and sympathetic nerve supply
75% of lymph drainage to axilla
lymph drainage in all directions: lat- pectoral and central nodes, med- perasternal nodes, superiorly-apial nodes
V. Bones of Thorax [N.170]
1. Sternum
Manubrium with jugular notch & articulations with clavicle, costal cartilages 1 and 2
Sternal angle- 2nd costal cartilage (lat); disk b/t T4 and T5 (post)
Body articulates with costal cart. 2-7
Xiphoid process consists of fibrocartilage
2. Ribs
Classification 1
True ribs 1-7- artic. Directly with sternum
False ribs 8-10- connected to stern. Via costal costal margin
Floating ribs 11-12 -not connected at all
Classification 2
Atypical ribs- 1,2 and 10-12
Typical ribs- heads articulate with vertebral body
Transverse process articulate with tubercles on neck of rib
Body and angle
Upper border is rounded, lower border is sharper and contains costal groove
Body joins costal cartilage anteriorly
Angled inferiorly going post to ant
3. Thoracic vertebrae
Thoracic spinal nerves exit at a level below vertebrae of same number
Bodies have two demifacts to articulate with rib heads andfacets
4. Synovial joints
B/t costal heads and vertebral bodies
Costal tubercles and transverse processes
Sternocostal jints
Interchondral joints
Moves little individ, to/g prod. Sig. Movement for respiration.
VI. Intercostal spaces
1. Intercostal muscles [[N.176+]
External intercostals-run post. To ant. à anterior intercostal membrane
Internal intercostal muscle- run ant. To post à posterior intercostal membrane
Innermost intercostals-found laterally, deficient ant. and post.
Transversus thoracis- anteriorly
Subcostalis- posteriorly
Neurovasular bundle- b/t internal and innermost intercostals m.
Intercostal muscles elevate ribs and keep intercostals spaces rigid
2. Intercostal blood vessels [N.176]
Ant. intercostals vessels are braches of internal thoracic or musculophrenic artery.
Post. Intercostals arteries are branches of descending thoracic aorta or costocervical trunk
3. Intercostal nerves
Ant. primary rami of spinal nerves
Lie inferior to other struc in costal groove
VII. Blood Supply
Internal thoracic vessels
Originate from subclavian and run posterior to costal cartilages, lat. To sternum
Give rise to ant. intercostals art.
Divide into superior epigastric and musculophrenic vessels
Branches of axillary art. and vein also suplly thoracic wall
VIII. Movement of Thorax
Descent of diaphragm is major factor in expansion of thoracic cavity
Movt of ribs 3-6 increase anterior-posterior diameter
Movt of ribs 7-10 increase lateral diameter
Lungs follow movt of chest passively as a result of adhesion between pleurae
|
Rib |
Surface Projection |
|
1 |
Right brachiocephlic trunk bifurcation |
|
2 |
Superior border of scapula Bifurcation of trachea (carina) Beginning and termination of aortic arch Termin. of fibrous pericardium Sternal angle |
|
3 |
Right atrium Medial end of spine of scapula (opposes T3 spinous process) |
|
4 |
Horizontal fissure of right lung |
|
5 |
|
|
6 |
Oblique fissures Part of left inferior margin of heart Level of lung at midclavicular line |
|
7 |
Inferior angle of scapula (@ T7 and 7th intercostals space) |
|
8 |
Entrance of IVC to heart Level of pleura at midclavicular line Level of lung at midaxial line |
|
9 |
|
|
10 |
Level of pleura at midaxial line Level of lung at mid-scapular line |
|
11 |
|
|
12 |
Level of pleura at mid-scapular line |
|
Intercostal Space |
Surface Projection |
|
1 |
|
|
2 |
|
|
3 |
|
|
4 |
Nipple |
|
5 |
Apex of heart Left part of inferior margin of heart |
|
6 |
|
|
7 |
|
|
8 |
|
|
9 |
|
|
10 |
Navel |
|
11 |
|
Tags: axillary tail, Bifurcation of trachea, clavicular, Cutaneous Innervation, Dermatomes, diaphragm, lactiferous duct, lymph drainage, Mediastinum, Oblique fissures, Sternocostal, Synovial, Thorax, Xiphoid process
