Thoracic Wall & Lungs - 6 March 2008

Ribs

Costal cartilages

Sternum

· vertebrosternal ribs

· vertebrocostal ribs

· vertebral ribs

Netter, 2003 pl. 178; Netter, 2006 pl. 185

Costovertebral Articulations

Ribs 1-10 articulate with two vertebral bodies at the capitulum and with the transverse process at the tuberculum. These dual articulations determine how the ribs move.

The shape of the Costotransverse joint of T1 - T7 causes rotation of the rib at this joint.

The flat Costotransverse joint of T8 - T10 allows a gliding motion of the tubercle with the transverse process.

Agur & Lee, 1999, Grant's Atlas of Anatomy, 10th ed. Fig. 1.13

See: Netter, 2003 pl. 180; Netter, 2006 pl. 187

This is the basis of the differences in motion of superior versus inferior ribs.

“Pump handle” motion in ribs 2-7

“Bucket handle” motion in ribs 8-10.

Moore & Dalley 2006, Fig. 1.8 & 1.9

The Thoracic Wall has three layers of muscles:

External intercostal

Internal intercostal

Transversus thoracis

Netter ,2003 pl. 182; Netter, 2006 pl. 188

Internal intercostals are further subdivided into Parasternal and Interosseous portions

Netter, 2003 pl. 183; Netter, 2006 pl. 189

Intercostal muscles

· External intercostals

– Only between ossified portions of ribs

· Internal intercostal

– Parasternal - between costal cartilages

– Interosseous - between ossified ribs

· Transversus thoracis

– From ossified portions of ribs 2-6 medially to sternum

– Similar orientation to transversus abdominis

Netter, 2003 pl. 184; Netter, 2006 pl. 191

Abdominal Wall

External abdominal oblique

Internal abdominal oblique

Transversus abdominis

Rectus abdominis enclosed within an aponeurotic sheath.

These layers correspond in position and orientation to the muscle layers of the thorax.

see: Netter, 2006 pl. 249

Muscle fiber patterns in the internal intercostals

· Interosseus portion

· Intercartilagenous (parasternal) portion

Muscle fiber patterns between the two portions of the internal intercostal are the same, but the rigid elements differ. This imparts a different function.

Netter, 2003 pl. 178; Netter, 2006 pl. 185

Intercostal Muscle Function

Muscle fiber orientation

· Rigid element orientation

· Patterns of relative resistance

Costodiaphragmatic recess

Potential space for lung expansion

Netter, 2003 pl. 190 & 191; Netter, 2006 pl. 193

Diaphramic Attachment to the Ribcage

· Note fiber orientation

Netter, 2003 pl. 184;Netter, 2006 pl. 191

Pleura

· Thoracic and abdominal viscera are enclosed in double-layer sacs of membrane

– Pleura of the lungs

– Pericardium of the heart

– Peritoneum of the abdominal organs

· One layer covers the surface of the organ

– The visceral layer (visceral pleura)

· The other layer lines the inside of the body cavity

– The parietal layer (parietal pleura)

· The space between the layers is the pleural cavity

· The two layers are actually a single continuous layer that folds back upon itself

· Neurovascular structures pass through the hilum

· This is the place where the pleura folds back and changes from visceral to parietal

· The parietal pleura has three different area based on position

– Costal parietal pleura

– Mediastinal parietal pleura

– Diaphragmatic parietal pleura

Thoracic Organs insitu

Heart acts as a partition between the lungs

Contained in mediastunum

· Phrenic nerves

· Pericariacophrenoic vessels

Lines of Pleural Reflection

The lines along which the pleura folds from the costal to the mediastinal or diaphragmatic surfaces are called lines of pleural reflection.

Netter, 2003 pl. 207; Netter, 2006 pl. 211

Rosse & Gaddum Rosse, 1997; Fig. 19-15

Diaphragm

Composed of two hemi-domes with a central tendon at the top.

Passages for:

· Superior vena cava (T8)

· Esophagus (T10)

· Aorta (T12)

The diaphragm has four different parts

· Sternal

· Costal

· Lumbar

· Crural

Netter, 2003 pl. 188, 189; Netter, 2006 pl. 194 & 195

Muscles of inspiration

Primary

· Scalenes

· Parasternal (internal) intercostals

· External intercostals

· Diaphragm

Secondary

· Sternocleidomastoid

Expiration is partly by passive recoil, but also by muscular activity at times of increased activity.

· Transversus thoracis

· Internal (interosseous) intercostals

· Internal abdominal oblique

· Transversus abdominis

Netter, 2003 pl. 191; see Netter, 2006 pl. 188, 189

Trachea

Incomplete cartilaginous rings

Bifuracates at about T4 into Mainstem bronchi;

Divides into lobar and segmental Bronchi

Netter, 2003 pl. 198; Netter, 2006 pl. 202

Distribution of arteries, veins and bronchi

The mainstem bronchi, the veins and arteries enter the lung

At the hilum,

· Pulmonary artery superior

· Pulmonary veins anterior & inferior

· Bronchus posterior

Lungs divided into

· bronchopulmonary segments

· the bronchovascular units of the lung.

Netter, 2003 pl. 202; Netter, 2006 pl. 206

Netter 2003 pl. 194; Netter, 2006 pl. 198

Segmental arteries run with the bronchus in a segment.

Pulmonary veins have intrasegmental and intersegmental branches

Rosse & Gaddum Rosse, 1997; Fig. 20-12

See Netter, 2003 pl. 203; Netter, 2006 pl. 207

Lungs Divided into Lobes

Oblique and horizontal fissures divide superior, inferior & middle lobes of right lung.

Left lung has no middle lobe.

Note that the inferiorlobe covers most of the posterior surface of the lung.

Netter, 2003 pl. 195, 197, 199; Netter, 2006 pl. 199, 201, 203

REFERENCES

Rosse and Gaddum-Rosse, 1997. Hollinshead's Textbook of Anatomy. 5th Ed. Lippincott-Raven.

Note that these figures can also be found in the 4th edition of this textbook, available in the anatomy lab.)

Agur & Lee, 1999, Grant's Atlas of Anatomy, 10th ed. Fig. 1.13