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The cephalic vein drains into the axillary vein.

The blood in the cephalic vein is drained to the axillary vein by 2 routes:

• Directly after piercing clavipectoral fascia i.e., Cephalic vein ⇒ Axillary vein
• Some amount of venous blood is drained into the basilic vein through the median cubital vein i.e., Cephalic vein ⇒ Median cubital vein ⇒ Basilic vein ⇒ Axillary vein

The cephalic vein is a preaxial vein.

The pre-axial and post-axial borders are decided on the basis of their placement, with respect to the axis of the limb.

In the upper limb, the pre-axial vein of the dorsal venous arch becomes the cephalic vein and the postaxial vein becomes the basilic vein.

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Pre-axial border

Cranially-placed limb border

Upper limb:Outerborder (rad ial aspect)•Cephalic veinLowe r limb: Inner border• Greater saphenous vein

Post-axial border

Caudally-placed limb border

Upper limb:Innerborder (uln ar aspect)•Basilic veinLower l imb: Outer border• Lesser sa phenous vein

The apical group of lymph nodes receives lymphatic drainage from the rest of the axillary lymph node groups. Hence, they are known as terminal axillary lymph nodes.

The lymphatic drainage of axillary nodes is given below:

Anterior, posterior and lateral groups ⇒ Central group ⇒ Apical group The apical group then drains into the supraclavicular lymph nodes.

The lateral group of axillary nodes lies posteromedial to the axillary vein. The anterior group of axillary nodes lies near the lateral thoracic vessels.

Axillary lymph nodes collectively drain the entire upper limb, breast, and trunk above the umbilicus.

Axillary nodes can be divided into 5 groups namely:

• Lateral/ humeral
• Anterior/ pectoral
• Posterior/ subscapular
• Central
• Apical

Humeral/ Lateral group

Pectoral/ Anterior group

Subscapular/ Posterior g roup

Central group

Location

Posteromedial toaxillary vein

Alonglateral thoracic vess els

Along thesubscapular ves sels

Embedded in theaxillary pad of fat

Afferents

Whole limb except vessel s accompanying cephalic veins

Skin and muscles of supr a-umbilical anterolateral body wall and breast

Skin and muscles of the i nferior posterior region o f the neck, dorsal aspect of the trunk up to iliac cr est

All preceding groups

Efferents

• Central nodes• Apical n odes• Inferior deep cervic al nodes
• Central nodes• Apical n odes
• Central nodes• Apical n odes
• Apical group

Location Afferents Efferents

Apical group

Deep to clavipectoral fasc ia, along theaxillary vesse ls

Those accompanying cep halic vein

Unite as subclavian trunk, right trunk drains into J ugulo-subclavian venous j unction and left trunk en ds in thoracic duct

The 8th rib is the false rib because it does not articulate with the sternum anteriorly.

• First 7 ribs are true ribs as they are attached anteriorly to the sternum by costal cartilages.
• Ribs 8-10 are false ribs as they join the superjacent costal cartilage.
• Ribs 11 and 12 are floating ribs as they float freely without costal attachment.

The costosternal joint is not formed by direct articulation with ribs. The costosternal joint is formed by the articulation of the lateral sternal border with the costal cartilages of the ribs.

The first sternocostal joint is a type of synarthrosis. Joints are classified in 2 ways:

Classification 1 is based on the type of motion (functional):

• Synarthrosis - no movement (first sternocostal joint)
• Amphiarthrosis - some movement (pubic symphysis)
• Diarthrosis - full movement (elbow/shoulder/ankle)

Classification 2 is based on the structure of joint:

1. Fibrous

• Sutures (joints between skull bones)
• Syndesmoses (distal tibiofibular joint)
• Gomphose (joint between teeth and teeth sockets in mandibular/maxillary bone)

2. Cartilaginous

• Synchondrosis - primary cartilaginous (costochondral joints)
• Symphysis - secondary cartilaginous (manubriosternal and xiphisternal joints)

3. Synovial (elbow, knee, hip etc.)

• the presence of these help the thoracic cavity expand during inspiration. E.g.:
• Interchondral joint
• Sternocostal joint
• Costovertebral joint
• Costotransverse joint

The spinous processes of vertebrae do not provide articulation to ribs. Note:

Two facets on head of the ribs are separated by a transverse crest which is attached to the intervertebral disc above it.

1st rib is an atypical rib and does not articulate at 3 sites with a vertebra. It has 2 articulations as follows:

• Circular facet on the head of the rib with the body of the first thoracic vertebra
• Tubercle of the rib to the transverse process of the corresponding vertebra
• Ribs are divided based on anatomical features as typical and atypical.
• Typical ribs:

Ribs 3 to 9 are typical. A typical rib is curved, and has a shaft with anterior and posterior ends:

• The anterior end has costal cartilage
• The posterior end has a head, neck, and a tubercle and articulates with the vertebra at 3 sites as follows:
• The head has 2 facets and articulates with the vertebra at 2 sites
• The tubercle has articular and nonarticular surfaces. The articular surface articulates with the transverse process

Atypical ribs:

Ribs 1, 2, 10, 11, and 12 are atypical.

• 1st rib - it is flat. The head has only a single articular facet. The superior surface has a
• scalene tubercle.
• 2nd rib - the external surface of the shaft has a rough area, where the serratus anterior
• attaches.
• 10th rib - the head has a single facet.
• 11th and 12th ribs - the head has 1 large facet. They don't have necks or tubercles.

The given case scenario and chest X-ray features are suggestive of a tumor at the apex of the right lung, also called Pancoast tumor. The thoracic duct does not lie between the 1st rib and the apex of the lung, so it will not be compressed. The thoracic duct crosses from right to left in the mediastinum at the level of T5 and ascends upwards to drain into the venous system.

The structures present between the 1st rib and apex of the lung (medial to lateral) can be remembered using the mnemonic SVAN:

• Sympathetic trunk
• Vein - Posterior intercostal
• Artery - Superior intercostal
• Nerve - T1 nerve

Clinical significance:

Pancoast tumors can cause destruction of the first rib by mass effect. Given below is an X-ray image of a Pancoast tumor (marked as P).

The marked area is the groove anterior to the scalene tubercle on the first rib. The subclavian vein passes through this.

It is structures passing through the grooves around the scalene tubercle are:

• Anterior groove - Subclavian vein.
• Posterior groove - Subclavian artery and lower trunk of brachial plexus.
• The image below shows the relations of the first rib

The structure marked A is the scalenus anterior. It attaches on the first rib on its scalene tubercle.

The scalene tubercle is a small projection on the medial (inner) border of the 1st rib, between two grooves.

Structures passing through these grooves are

• Anterior groove - Subclavian vein.
• Posterior groove - Subclavian artery and lower trunk of brachial plexus.

Option B: The tuberculum sellae is a part of the sphenoid bone and is present within the sella turcica

Option D: The Chassaignac tubercle or carotid tubercle is present on the transverse process of C6. The carotid pulsations are palpated by pressing against this.

In the given image, the scalenus posterior marked as C has no attachment on the first rib. It attaches to the second rib.

Other structures marked are:

A - Scalenus anterior

B - Subclavius

D - Scalenus medius

The attachments on the 1st rib are:

• Subclavius
• Scalenus anterior
• Scalenus medius
• First digitation of serratus anterior
• Suprapleural membrane
• Costoclavicular ligament

The arrangement of the components of the neurovascular bundle in the intercostal space from below upwards is nerve-artery-vein.

The arrangement can be remembered from above downwards with the mnemonic VAN: vein-artery-nerve.

The tip of the T3 spinous process corresponds to the root of the spine of the scapula Other important surface markings of scapula:

• Superior angle of scapula: at the level of 2nd rib and vertebra T2.
• Inferior angle of scapula: opposite the T7 vertebral spinous process.

The stab injury penetrated the apex of the lung. It is covered by Sibson's fascia, also known as the suprapleural membrane. Attachment of Sibson's fascia is at vertebra C7.

Sibson's fascia is attached:

• Anteriorly to the inner border of the first rib
• Posteriorly to the anterior border of the transverse process of the C7 vertebra.

The intercostal nerve is a branch of ventral rami (anterior) of thoracic spinal nerves. Intercostal nerves are distributed primarily to the thoracic and abdominal walls:

• The 1st thoracic nerve with a variable proportion of the 2nd passes into the brachial plexus.
• The 3rd,4th,5th,6th supply only the thoracic wall,
• The 7th,8th,9th,10,11th supply both thoracic and abdominal walls.
• The subcostal nerve supplies the abdominal wall and the gluteal skin.

Thoracic spinal nerve, T6 is involved here as it supplies the skin over the xiphoid process.

The anterior chest wall is innervated by the lateral and anterior cutaneous branches of the intercostal nerves.

Intercostal nerves T7 to T11 and the subcostal nerve T12 supply the skin and muscle of the abdominal wall. In addition, T5 and T6 supply the upper parts of the external oblique muscle of the abdominal wall. The highest thoracic dermatome on the anterior chest wall is T2.

The structure marked A is the intercostal nerve. It doesn't lie between external and internal intercostal muscles, but lies between the internal and innermost intercostal muscles.

Intercostal nerves are derived from the ventral rami of the thoracic vertebrae - T1 to T11. They lie between the internal intercostal and innermost intercostal muscles.

Typical intercostal nerves are those that only supply only the thoracic wall, e.g, 3rd to 6th intercostal nerves. All the other intercostal nerves supply other regions as follows:

• Upper two intercostal nerves - supply upper limb
• 1st intercostal nerve - does not have the lateral and anterior cutaneous branches.
• 2nd intercostal nerve - gives off the intercostobrachial nerve
• 7th to 11th intercostal nerves - supply abdominal wall, hence they are called thoracoabdominal nerves.

In each intercostal space, the arrangement of the structures superior to inferior is vein, artery, nerve (VAN). In the 1st intercostal space, the neurovascular bundle lies superiorly, and the arrangement from medial to lateral is the Sympathetic trunk, intercostal Vein, superior intercostal Artery, intercostal Nerve. (SVAN).

The subcostal nerve is formed by the ventral ramus of T12.

It supplies the abdominal wall and gluteal skin and gives a branch to pyramidalis.

The given case scenario is suggestive of iatrogenic injury to the intercostobrachial nerve. It is a branch of the 2nd intercostal nerve.

It is the lateral cutaneous branch of the 2nd intercostal nerve and supplies the skin of the axilla and upper part of the medial aspect of the arm.

Clinical significance:

• Common site of injury during surgeries such as mastectomy, axillary nerve blocks, and other axillary surgeries.
• Source of referred cardiac pain.

Intercostal drainage tubes are placed in the mid-axillary line, and transversus thoracis is not pierced as it lies anteriorly, not in the mid-axillary line.

Transversus thoracis muscle:

• Also known as triangularis sternae or sternocostalis.
• Origin - lower third of the posterior surface of the sternum, xiphoid process, and costal
• cartilages of lower 3-4 true ribs.
• Insertion - into the cartilage of the 2nd to 6th ribs.

The innermost muscular plane has three named muscles:

• Innermost intercostals are at the sides of the rib cage.
• Subcostalis are at the back
• Transversus thoracis at the anterior part of the thoracic rib cage.

The left phrenic nerve supplies sensory fibers to the parietal peritoneum covering the diaphragm, and the mediastinal and diaphragmatic pleura on the left side.

The phrenic nerve is a mixed nerve derived mostly from the C4 ramus and also receives contributions from the C3 and C5 ventral rami. It is formed at the lateral border of scalenus anterior.

It descends anterior to the pulmonary hilum and lies between the mediastinal pleura and fibrous pericardium. It passes through the muscular part of the diaphragm just anterior to the central tendon. The right phrenic nerve passes through the vena caval opening.

Both right and left phrenic nerves supply:

• Motor fibers to the muscular diaphragm - respective crura of the diaphragm
• Sensory fibers to the mediastinal pleura, fibrous and serous pericardium, and diaphragmatic peritoneum.

The pain of pericarditis is carried by the phrenic nerve.

The somatic sensation from the pericardium is carried by the somatic afferent fibres of the phrenic nerve. The pericardial pain may be referred to the supraclavicular region of the shoulder or lateral neck area (dermatomes C3, C4, and C5).

The right phrenic nerve is involved by the tumor as it passes anterior to the hilum of the lung.

The phrenic nerve provides the sole motor supply to the diaphragm. Normally, the diaphragm flattens when it contracts. Involvement of the phrenic nerve causes elevation of the respective dome of the diaphragm.

Options A, C - Vagus nerve passes posterior to the hilum of the lung. The recurrent laryngeal nerve arises from the vagus nerve before this.

Option B - The intercostal nerve lies in the intercostal space and is not related to the hilum of the lungs.