Editing Chest wall


Made up of 12 thoracic vertebrae, 12 pairs of ribs and costal cartilages and the sternum, along with associated soft tissues.

== '''Surface anatomy''' ==

* Jugular/supra-sternal notch
* Angle of Louis
** Articulation of sternal      angle and 2nd costal cartilage
** Defines upper third of      thoracic cage
** Level of aortic arch and      tracheal carina and T4-T5
* Nipple
** Men - 4th ICS, just lateral      to the mid-clavicular line
* Vertebra prominens - C7     spinous process
* Scapulae
** Medial edge lies from ribs      two to seven
** Spine extends diagonally      upwards from medial edge at T3, to the acromion
** Scapular plane lies on a      plane passing through the inferior angle of the scapula
* Lungs



== '''Muscle layers:''' ==

* '''Anterior     thorax:'''
** '''Pectoralis      major'''
*** Arise from clavicular and       sternocostal fibres
*** Converge into a flat tendon       inserting into the inter-tubercular sulcus of the humerus
*** Lower edge forms the       anterior axillary fold
*** Supplied by medial and       lateral pectoral nerves (brachial plexus)
*** Clavicular function: flex,       adduct, inwardly rotate and elevate the arm
*** Sternocostal function:       Contribute to downward and forward movement of the arm
** '''Pectoralis      minor'''
*** Arise from upper borders       and outer surfaces of ribs 2-5
*** Form a flat tendon       inserting to coracoid process of the scapula
*** Depress and rotate the       shoulders downward
*** Supplied by the medial and       lateral pectoral nerves
** '''Serratus      anterior'''
*** Lie along the anterolateral       aspect of the thoracic wall
*** Originate from ribs 1-8
*** Insert along the anterior       surface and medial border of the scapula
*** Supplied by long thoracic       nerve (anterior rami of 5th, 6th and 7th cervical nerves) - in danger       during thoracic incisions in axilla, although this probably produces       little morbidity
*** Hold the scapula to the       thoracic wall and participate in adduction and elevation of the arms       above the horizontal position
**
* '''Posterior     thorax:'''
** '''Trapezius'''
*** Arise from superior nuchal       line of occiput, the ligamentum nuchae of neck, the spine of C7, and       spines and supraspinous ligaments of all thoracic vertebrae
*** Superior fibres to lateral       third of clavicles; middle fibres to acromion of scapula and spine;       inferior fibres converge near the scapula and end in an aponeurosis
*** Supplied by spinal       accessory nerves and filaments from C3 and C4
*** Elevate, depress or abduct       the scapula
*** Encountered in posterior or       posterolateral thoracic incisions
** '''Latissimus      dorsi'''
*** Arise by broad aponeurotic       origins from spines of lower thoracic vertebrae, lumbodorsal fascia,       iliac crests and some slips from the outer surfaces of the lower three       or four ribs
*** Fibres converge frontward       and spiral upward to insert on the intertubercular groove of the humerus
*** Form the posterior folds of       the axillae
*** Supplied by thoracodorsal       nerve (posterior cord of brachial plexus)
*** Allow arm adduction,       extension and medial rotation
*** Accessory muscles of       respiration
** '''Scapular      muscles'''
*** '''Levator       scapulae'''
**** Thin long muscle located        laterally on each side of the neck
**** Fibres lie diagonally down        to the superior angle of the scapula
*** '''Rhomboid       minor'''
**** Originate from C7 and T1        spines
**** Runs down to base of        scapular spine
*** '''Rhomboid       major'''
**** Starts from T2-T5 spines
**** Extends downwards to        medial border of the scapulae, inferiorly
**** Can be encountered in        posterolateral incisions, depending whether the incision is taken high        up between scapula and vertebral column
*** All supplied by dorsal       scapular nerve
*** Subscapularis
**** Arises from the costal        surface of the scapula and inserts into the lesser tuberosity of the        humerus
**** Supplied by subscapular        nerves
**** Steadies the head of the        humerus against the glenoid cavity and assists in medial rotation of        the humerus
*** Teres major
**** Arises near the inferior        angle of the scapula and inserts to the bicipital groove of the humerus
* '''Outer layer     intercostals'''
** '''External      intercostals'''
*** Fill the 11 intercostal       spaces
*** Arises from lower border of       a rib and inserts to the upper border of the rib below
*** Thicker than internal       intercostals
*** Fibres directed obliquely       downward and lateral on the back, and downward, forward and medial on       the front
*** Conventionally considered       to elevate the ribs
*** Incomplete anteriorly -       replaced by anterior intercostal membrane in the region of the costal       cartilages
** '''Serratus      posterior superior'''
*** Elevates upper ribs in       inspiration
** '''Serratus      posterior inferior'''
*** Depresses lower ribs in       expiration
* '''Middle layer     intercostals'''
** '''Internal      intercostals'''
*** Begin ventrally at sternum       and extend as far laterally as the angles of the ribs, where they       condense into thin aponeuroses called internal intercostal membranes
*** Fibres directed inferiorly       and posteriorly, opposite to external intercostals
*** Conventionally considered       to lower the ribs
* '''Inner layer     intercostals'''
** '''Innermost      intercostals'''
*** Incomplete and variable
*** Fibres pass in the same       direction as internal intercostals
*** Deep to neurovascular       bundle
** '''Transversus      thoracis group'''
*** Arises from the deep       surface of the lower half of the sternum and fans outwards and upwards       to join the costal cartilages of the upper six or so ribs


== '''Neurovascular bundle''' ==

* Posteriorly, lies about     midway in the intercostal space, but from the costal angle onwards comes     to lie in the subcostal groove of the rib above, where it is partially     projected by the downward projection of the lower border of the rib
* Runs between the innermost     and internal intercostal layers.
* Generally ordered vein,     artery and nerve, from cephalad to caudad
* '''Artery'''
** Posterior and anterior      branches anastomosing in each intercostal space. Posterior arteries much      larger.
** Posterior arteries in spaces      1-2 from highest/supreme intercostal branch of costocervical trunk
** Posterior arteries in spaces      3-11 from descending thoracic aorta
** Anterior arteries are      branches of internal thoracic artery (spaces 1-6) and musculophrenic      artery (7-10)
* '''Vein'''
** Generally follow the      arterial distribution, but the posterior intercostal veins drain into the      azygos system on right, and hemiazygos on left
* '''Nerve'''
** Intercostal nerves come from      T3-T12
** Upper six nerves terminate      as anterior cutaneous nerves near the sternum
** Lower five nerves and      subcostal nerve terminate in abdomen
* '''Lymphatics'''
** Sternal glands located at      the anterior ends of the intercostal spaces
** ICS lymphatics receive lymph      from posterolateral chest, including intercostal muscles and parietal      pleura
** Lower 4-5 ICS glands unite      to form a trunk which descends to open into the origin of thoracic duct
** Upper ICS glands drain      directly into thoracic duct

== '''Bony anatomy''' ==

=== '''Ribs''' ===

** 12 ribs (can be 13 with      cervical or lumbar rib)
*** 1-5 are directly attached       by costal cartilages
*** 6-10 coalesce into the       costal arch
*** 11-12 are floating ribs -       no sternal attachment for costal cartilages, ending in muscle of       thoracic wall
** Cervical rib
*** Persistence of a separate       costal element of C7
*** Occurs in 1%, and 10% of       those will have compressive symptoms
***
** Progressively increase in      length to 7th rib then decrease again
** Ribs 3-9 are termed 'typical      ribs' - head, neck, body/shaft. Head interacts with vertebral column via      inferior facet to adjacent vertebral body, and upper facet to body of      vertebra above it. Also interacts with the transverse process of the same      numbered vertebrae, with the costotransverse ligament.
*** The costotransverse       ligament is thick and strong, and this is the landmark for maximum       posterior extent of incision in thoracotomy.
** Cervical rib - cartilaginous      or ossified rib borne by C7, which may be shorter or longer and attached      to the first costal cartilage or to the manubrium. Can compress      subclavian vessels and/or the brachial plexus.

=== '''Sternum''' ===

** 15-20cm long flat bone
** Three portions:
*** Manubrium - top part
*** Body
*** Xiphoid - ends in the       rectus abdominis sheath

=== '''Thoracic     vertebrae''' ===

== '''Cutaneous innervation''' ==

* Supra-clavicular nerves     (terminal branches of spinal nerves C3 and C4) supply the skin above, over     and below the clavicles
* Remainder of anterior     thoracic wall supplied by anterior and lateral cutaneous branches of     thoracic spinal nerves
* Dorsal rami of C4, C5, C8, T1     and T2 supply skin over the back by medial cutaneous branches
* Skin over inferior back is     supplied medial and lateral cutaneous branches of T3-T10

== '''Other features''' ==

=== '''Thoracic     inlet (superior)''' ===

** Uppermost extent of the      thoracic cavity
** Formed by manubrium, 1st      ribs, and T1
** Anterior border lies about      2cm below the posterior border

=== '''Thoracic     outlet (inferior)''' ===

** Bordered by xiphoid process,      fused costal cartilages of ribs 7-10, anterior portions of 11th ribs,      arches of 12th ribs and T12
** Anterior margin at T10;      posterior margin at T12; reaches lowest level laterally (L2)

[[Category:Anatomy]]