Cavities, Bones, Joints and Muscles of the Thorax

Thorax (General)

houses and protects

• heart

• lungs

conduit/pathway for structures passing between neck+abdomen

role in breathing

Apertures of Thorax

superior throacic aperture→narrow

• open

contain AVNs

• pass over rib 1

• go inferior to/under clavicle

• major A+V+brachial plexus→through axillary inlet

interior thoracic aperture→wider

closed→by diaphragm

Axillary Inlet

lies on each side of superior throacic aperture of thorax

superior to rib 1

inferior to clavicle

gateway to upper limb

margins

• superior margin of scapula

• clavicle

• lateral margin of rib 1

contains

• A

• V

• brachial plexus

Thoracic Cavity Compartments

3 compartments

pleural cavities→2

• contain→lungs

mediastinum

Mediastinum (General)

soft tissue partition→thick but flexible

median sagittal position

separates pleural cavities

extends from

• sternum→vertebral bodies

• superior thoracic aperture→diaphragm

contains

• trachea

• esophagus

• heart

• major Ns

• systemic blood vessels

clinical significance

• can access heart without opening pleural cavities

• abnormalities in one cavity→don’t always affect other cavities

Superior+Inferior Portions of the Mediastinum

horizontal plane

passes thorugh sternal angle+IVD between T4-T5

superior mediastinum (red)

• large vessels of heart

• trachea

inferior mediastinum

subdivided by pericardium:

anterior mediastinum (green)

• between sternum+pericardium

middle mediastinum (yellow)

• pericarium

• heart

posterior mediastinum (blue)

• between pericaridum+thoracic vertebrae

Thoracic Wall

musculoskeletal wall

posteriorly

• 12 thoracic vertebrae

• IVDs

laterally

• ribs

• intercostal muscles

anteriorly

• sternum

Bony Thorax Components

thoracic vertebrae

ribs

sternum

Ribs (General)

12 pairs

all terminate→anteriorly with costal cartilages

all ribs→articulate with vertebral column posteriorly

not all articulate with→sternum

True Ribs vs False Ribs

true ribs

• ribs 1-7

• articulate directly with sternum→through own costal cartilage

false ribs

• ribs 8-12

• do not have own costal cartilage articulating with sternum

two types:

1. ribs 8-10→articulate w sternum via costal cartilages of superior ribs

2. ribs 11-12→no anterior connection to sternum (floating ribs)

General Rib Osteology (Positioning)

head

posterior side

superior+inferior articular facets on head

articulates with vertebrae:

• superior articular facet of rib below

• inferior articular facet of same rib

neck

connects head to angle

tubercle

articular facet on tubercle→articulates with vertebral transverse costal facet

angle

connects neck to body of rib

general components

• internal surface

• external surface

• costal cartilage

Costal Groove

inferior margin on internal surface

contains

• intercostal V

• intercostal A

• intercostal N

• V→superiorly placed

• N→inferiorly placed
  -not protected by bone
  -perforation→often injured

Rib 1 (General)

tubercle

articulates→with transverse costal facet of of T1

head

• only 1 articular surface

• articulates→only with body of T1

scalene tubercle

• I: scalenus anterior

separates 2 grooves:

1. anterior groove→subclavian V

2. posteiror groove→subclavian A

Rib 10 (General)

has tubercle

head

• only 1 articular surface

• articulates→only with body of T10

Ribs 11+12 (General)

short

pointed anteirorly

no tubercles

no necks

articulate→with bodies of own vertebrae

still tipped with costal cartilage

Typical Rib Articulation

articulations→3

• inferior articular facet of head of rib→superior costal facet of body of own vertebra

• superior articular facet of head of rib→inferior costal facet of body of superiorly-placed vertebra

• tubercle→transverse process of own vertebra

Rib 1 Articulation

articulation→2 points

head→single facet→articulates with body of T1

tubercle→articulates with transverse costal facet of T1

Rib 10 Articulation

articulation→2 points

head→single facet→articulates with body of T10

tubercle→articulates with transverse costal facet of T10

Ribs 11+12 Articulation

articulation→1 point

heads→articulate with facets on bodies of own vertebrae

no tubercle

Sternum Components

manubrium

body of sternum

xiphoid process

Manubrium Articulation Points

contains articular facets+notches

clavicular notch→sternal end of clavicle

costal cartilages of rib 1

costal cartilages of rib 2 (with body of sternum)

Body of Sternum Articulation Points

contains articular facets

costal cartilages of rib 2→manubrium+body of sternum

costal cartilages of ribs 3-6→body of sternum

costal cartilages of rib 7→body of sternum+xiphoid process

Xiphoid Process Articulation Points

contains articular facets

costal cartilages of rib→xiphoid process+body of sternum

Rib Articulation Components

thoracic vertebrae

costal cartilages

sternum (some)

Costovertebral Joints

synovial joint

between bodies of adjacent vertebrae+head of one rib

Costotransverse Joint Articulation+Stabilization

between transverse processes of thoracic vertebrae+rib

stabilized by

• costotranverse ligament
  -between neck+transverse process

• lateral costotransverse ligament
  -between tip of transverse process+tubercle

• superior costotransverse ligament
  -betweeen neck+transverse process of vertebra above

Sternocostal Joints

between upper 7 costal cartilages+sternum

sternocostal joint between costal cartilage of rib 1+manubrium

• not a synovial joint

• fibrocartilaginous connection

sternocostal joint between costal cartilage of ribs 2-7

• synovial joints

• thin joint capsules

reinforced by→sternocostal ligaments

Interchondral Joints

synovial joint

between costal cartilages of adjacent ribs

primarily→between ribs 7-10

provide indirect anchorage to sternum

reinforced by→interchondral ligaments

Manubriosternal Joint

between manubrium+body of sternum

slight movements during respiration

Xiphisternal Joint

between body of sternum+xiphoid process

over time→can fuse together

Pectoral Region (General)

external to→anterior thoracic wall

anchors upper limb to trunk

two components

• superficial compartment
  -skin
  -superficial fascia
  -breasts

• deep compartment
  -muscles

Breasts Components

skin

connective tissue

• ligaments

• fascia

• adipose tissue

mammary glands

Mammary Glands

modified sweat glands
-series of ducts+secondary lobules→converge+form 15-20 lactiferous ducts→each open up to nipple
-nipple→surrounded by areola (pigmented skin around nipple)

located in

superficial fascia

anterior to pectoral muscles+anterior thoracic wall

Suspensory Ligaments of Breast

connective tissue→surrounds ducts+lobules→condense→form suspensory ligaments

• continuous with dermis

• support the breast

clinical importance

• breast cancer→causes tension on ligaments→pitting of skin

• orange peel texture (peau d’orange)

Breast (General) Margins

base of breast

• attached to thorax

• vertical/superior extent→ribs 2-6

• lateral extent→midaxillary line

• axillary process

clinical importance (axillary process)

breast pathologies→may present into axilla/along lateral margin of pectoralis major

Lymphatic Drainage

primarily (75%)

drainage from superolateral portions of breast→axillary lymph nodes

can also drain into

• parasternal nodes
  -drainage from medial part

• abdominal nodes
  -drainage from inferior part/portion

• supraclavicular nodes

• lymph nodes associated with opposite breast

clinical importance

can be difficult to contain nodal metastatic breast cancer

Breast Tissue Margins

breast→superficial to deep fascia of pectoral muscles

fascia→just superficial to pectoralis major

retromammary space (additional space separating breast tissue from fascia)

Retromammary Space

additional layer of loose connective tissues

between breast+deep fascia

separates breast+pectoral muscles+fascia

clinical importance

mastectomy→removal of breast tissue to pectoralis major+fascia

Male Breasts

in males→rudimentary

connective tissue

small ducts→usually do not extend beyond areola

clinical importance

breast cancer→can occur in males

Muscles of the Thoracic Wall

fill in+support intercostal spaces

pass between sternum+ribs→cross attachments of ribs

include

• external intercostal

• internal intercostal

• innermost intercostal

• subscostales

• transversus thoracis

Intercostal Muscles

located between adjacent ribs

3 layered muscles (best seen→lateral view between ribs)

• external intercostal
  -will see until costal cartilages→transitions to thin CT aponeurosis (external intercostal membrane)

• internal intercostal
  -deep to external intercostals anterolaterally+laterally
  -runs to→angles of ribs posteriorly→transitions to internal intercostal membrane→vertebrae

• innermost intercostal
  -best viewed inside thorax
  -separated from internal intercostal by→intercostal AVN (key for distinguishing)

Subcostales

same level as innermost intercostals

key to ID→ jump over ribs

best viewed→inside of low thorax→muscles that span more than 1 rib

lower in thorax→more numerous

Transversus Thoracis

internal surface of anterior thoracic wall

over internal thoracic AVN

spider muscles on ribcage

Respiratory Diaphragm

musculotendinous diaphragm

separates thorax from diaphragm

closes inferior thoracic aperture