Applied Anatomy


Extra ribs
  1. Cervical ribs

    +) These develop from persistent costal elements of c7
    +) Articulate with the seventh cervical vertebra.
    +) May be bony, cartilaginous or fibrous.
    +) May compress (or overstretch) the subclavian artery and or lower trunk of the brachial plexus


  2. Lumbar ribs

    +) Are more common than cervical ribs.
    +) They articulate with the first lumbar vertebra or are attached to tips of the transverse process.
    +) May confuse the identification of vertebral levels in radiographs.
    +) May be erroneously interpreted be intepreted as a fracture of a lumbar transverse process.

Bifid ribs : Can cause confusion in rib count


Fused ribs are uncommon, and are often associated with a vertebral abnormality e.g. a hemi vertebra

Rib Fractures:

  • Commonest site just anterior to the angle: area of greatest change in curvature

  • Becausef the ribs in infants and children are elastic, they do not often fracture.

  • Broken ends may be driven inwardly and injure the thoracic and or abdominal organs- lungs, spleen and liver

  • The middle ribs are the most commonly fractured. The first two ribs (which are partially protected by the clavicle) and the last two (which are free and movable) are the least commonly injured.

  • Fractured ribs are very painful because of their movements during respiration, coughing and sneezing. Patients experience considerable pain in the region of the fracture, when asked to take a deep breath. Careful palpation along the broken rib often reveals tenderness even when the fracture may not be visible on a radiograph.

  • When a sizeable segment of the anterior or lateral chest wall is freely movable, because of multiple rib fractures; this is called flail chest ( stove in chest' ). The loose segment of the chest wall moves paradoxically i.e. inward in inspiration; and outward in on expiration.

Thoracotomy: This is opening of the thoracic wall   e.g. to remove a collection of pus or fluid in the pleural cavity

Sometimes a piece of rib is used for autogenous bone grafting e.g. for reconstruction of the mandible following excision of a tumor. Following the operation, the rib defect generates from the remaining periosteum

The costal cartilages of young people provide resilience to the thoracic cage, preventing many crushing injuries or direct blows from fracturing the ribs and or sternum. Adults loose this protection, when the cartilage ossifies

Separation of a rib refers to dislocation of the costochondral junction between the rib and its costal cartilage; and not the lack of continuity in the shaft.

 

Sternum :
  1. Fracture of the sternum is uncommon except in automobile accidents, and when drivers' chest is driven into the steering wheel. In this case, the body of the sternum is commonly fractured in the region of the sternal angle and is often a comminuted fracture (broken into pieces). Fortunately, the ligaments coverings confine the fragments in most cases so that compound (open) fractures are prevented. In severe accidents, the body of the sternum seperates from the manubrium at the manubrosternal joint and is driven posteriorly, rupturing the aorta and or injuring the heart and liver. Such injury may kill from excessive loss of blood or damage to the myocardium

  2. Men in their early forties, when they suddenly detect their ossified xiphoid process, may consult the doctor for fear that they developed a cancer in the stomach.

  3. The sternum contains readily accessible bone marrow, which can be obtained by inserting a wide bone needle through the cortex of the sternum and aspirating. The needle goes through the skin , superficial fascia and periosteum of the sternum. This is called sternal puncture and is a potentially dangerous procedure which must be done carefully otherwise the needle may go as far deep and injure the aorta and or the heart

  4. Access to the anterior mediastinum may be gained by splitting the sternum in the median plane. This is called median sternotomy.

  5. The sternum develops as two separate Sternal bauds, which unite in the middle. The union may be incomplete, causing cleft sternum . Extensive cleft sternum may lead to exposure of the heart (which is commonly abnormal). This is called ectopic cordis and is fortunately rare.

  6. More commonly, is a sternal foramen, which care must be taken not to confuse it with a bullet wound. Otherwise such a foramina when small are of no clinical consequence

  7. The sternum may protrude out, like a pigeon chest (pectus carinatum) or project inferiorly and posteriorly like a funnel (pectus escavatum). These abnormalities are usually congenital and by altering the geometry of the chest, may interfere with normal respiratory movement. Pectus carinatum, for example is more subject to trauma.

 

Related to respiratory movements
  1. During respiration, there is considerable movement of the various joints of the thorax (costovertebral; costochondral and sternocostal). Hence any disorder that reduces the mobility of these joints interferes with respiration.

  2. A number of areas of the thoracic cage are affected by age changes, which compromise the normal respiration in the elderly. These include:

    • Partial or complete ossification of the costal cartilages

    • Fusion of the manubriosternal joint

    • Ossification of the xyphoid process and its fusion with the body of the sternum

    • Osteoarthritic changes in the costovertebral joints

  3. The shape of the thorax may be distorted by abnormalities of the chest wall- sternum, ribs or vertebral column e.g. pectus carinatum , pectus cavum , scoliosis , kyphosis. These result in a considerable change in the shape of the thorax.

  4. Congenital or acquired abnormalities of the diaphragm affect breathing movements. Paralysis of half of it does not affect the other half because each half has a separate nerve supply.
 

Lungs
  1. Because the apex of the lung extends into the neck, infections , trauma or wounds in the posterior

    triangle of the neck may involve the lung. In addition, auscultation of the lungs must include the root of the

    neck superior to the medial third of the clavicle, in order that sounds in the apex of the lung may be heard.


  2. Knowledge of the branching of the bronchial tree is necessary to determine the appropriate postures for

    draining infected areas
    of the lung e.g. when a patient with brochiectasis (dilation of bronchi) is positioned

    in bed on his or her left side, secretions from the right lung and bronchi flow towards the carina of the

    trachea. Since this is a sensitive area, the cough reflex is stimulated and the patients brings up purulent

    sputum
    , clearing the right bronchial tree. Alternatively, persons with bronchiectasis of the lingula of the left

    superior lobe, drain into it by lying on the right side. The basal bronchi may be cleared by the patient

    standing on his or her head for several minutes every morning to promote drainage of the lungs.  In the

    prone position (face downwards), the trachea slopes downwards and promotes drainage while the usual

    supine position one assumes in bed with the head slightly elevated by a pillow is poor for lung drainage.


  3. Bronchogenic carcinoma, is one of the most common cancers in men. It is highly positively associated with

    cigarette smoking, and environmental pollution. The arrangement of the lymphatics is such that these

    tumors may metastasise to the pleura; hila of the lungs; the mediastinum and from there to distant sites.

    Involvement of the closely related phrenic nerve by the tumour results in paralysis of half of the diaphragm.

    in the lower neck, involvement of the sympathetic chain and brachial plexus causes Pancoas's syndrome.

    Because of the intimate relationship of the recurrent laryngeal nerve to the apex of the lung, this nerve may

    be involved in apical lung cancers resulting in hoarseness of the voice owing to paralysis of a vocal fold.

    common sites of hematogenous metastasis of cancer cells from a bronchogenic carcinoma are the:


    • Brain

    • Bones

    • Suprarenal glands

  4. Supraclavicular lymph nodes are enlarged and hard when a patient has a carcinoma of the bronchus (or

    of the stomach) owing to metastasis from the primary tumour. The supracavicular lymph nodes are commonly

    referred to as sentinel nodes because enlargement of them alerts the examiner to the possibility of malignant

    changes in the thoracic and or abdominal organs. A tumor may invade the pleura and produce a pleural

    effusion. This exudate may be bloody and contain exfoliated cancer cells.


  5. Pulmonary embolism may occur, for example following fracture or other injury of the lower limb. It is a

    frequent cause of death. Embolic obstruction of a pulmonary artery produces a sector of lung which is

    ventilated but not perfused. A large embolus may occlude the pulmonary trunk or one of its main branches.

    The patient suffers acute respiratory distress, and may die in a few minutes. A medium sized embolus may

    block an artery to a bronchopulmonary segment producing an infarct. In healthy young people, collateral

    circulation may prevent this infarction. But in sick people, with already compromised pulmonary circulation,

    infarction is almost always the result.

    Because an area of visceral pleura is also deprived of blood, it becomes inflamed (pleuritis) and rough

    resulting in pleuritic pain and friction rub.

Pleura


  1. The copolae of pleura, and the apices of the lungs, project superiorly into the neck, posterior to the

    sternocleidomastoid muscles and into the posterior triangle of the neck. Medially, these are related to the

    roofs/trunks of the brachial plexus and the sympathetic chain. Consequently, apical bronchogenic

    carcinoma can compress these structures giving both autonomic and somatic neurological deficits. This is the

    Pancoast's syndrome
    . Additionally, such cancers can also compress the structures in the thoracic inlet,

    leading to the thoracic inlet syndrome. By its extension into the neck, wounds in the posterior triangle of

    the neck can affect the pleural cavity and the lung, and infections may also spread upwards. In “radical”

    block dissection of the neck for tumor, care must always be taken not to open the pleural cavity.

2) The pleurae descend inferior to the costal margin in three regions.

  • The right infrasternal angle.
  • The left costovertebral angle.
  • The right costovertebral angle.

At these sites, an abdominal incision might inadvertently enter a pleural sac. In cases where the 12 th rib is

very short, the pleura lies inferior to the posterior costal margin after crossing the 11 th rib, and is therefore in

surgical danger.

3)Fluid in the pleural cavity

  • Empyema thoracis/pyothorax- pus .
  • Hemothorax - Air occur, a condition known as
  • Haemopneumotorax- blood and air
  • Chylothorax-chyle

4) Fluid can be drained from a pleural cavity by inserting a wide-bore needle through an intercostal space- usually i

n the posterior axillary line in the seventh intercostal space. The procedure of aspirating fluid from the pleural

cavity is called a pleural tap . Sometimes, a canula may be retained in the pleural cavity for continous drainage of

the fluid. The canula is usually connected to an under water seal bottle.

5) Sometimes, to prevent troublesome recurrent spontaneous pneumothorax due to lung disease, the visceral and

parietal layers of pleura may be purposely fused. The surgical procedure of surgically fusing the pleurae is called

pleural poudrage
. In this procedure, adherence of the two layers is induced by covering the opposing pleural

surfaces with a slightly irritating powder.

6) Inflammation of the pleura (pleuritis or pleurisy) causes the pleural surfaces to become thickened and/or

rough. During breathing, a friction rub(pleural tub) may be heard with a stethoscope. Pleuritis, usually leads to

formation of pleural adhesions between the parietal and visceral pleurae. In extreme cases, in chronic

inflammation of the pleurae may cause the adhesion of the two layers, with subsequent thickening . Calcification of

this thickened pleura is known.

7) Irritation of the parietal pleura causes pain, worse on inspiration. The pain is usually referred to the

thoracoabdominal wall due to common innervation by the intercostal nerves; or to the shoulder and the side of

the neck due to shared spinal cord segments with the phrenic nerve(C3,4,5).

 

Bronchopulmonary segments

  • Benign bronchial and pulmonary disorders tend to be localised in individual segments.

  • Each segment is amenable to independent surgical removal except in malignancy and TB

 

 

 

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Chapter 28: The Chest Wall and Pleura