Deep structures of the neck
Prevertebral Region
Question 1. What are Scalene Muscles?
Answer.
- These are deep muscles on the side of vertebral column of the neck (paravertebral region).
- They extend from transverse processes of cervical vertebrae to the first two ribs.
- They are usually three in number, i.e.:
- Scalenus anterior (key muscle at the root of neck)
- Scalenus medius (largest of the three scalene muscles)
- Scalenus posterior
Question 2. Describe the origin, insertion, nerve supply, actions and relations of Scalenus Anterior Muscle.
Answer.
Scalenus Anterior Muscle Origin
From anterior tubercles of transverse processes of C3 to C6 vertebrae.
Scalenus Anterior Muscle Insertion
Into scalene tubercle on the inner border of 1st rib.
Scalenus Anterior Muscle Nerve supply
By ventral rami of C4 to C6 spinal nerves.
Scalenus Anterior Muscle Actions
- Acting from below, it bends the neck forwards and laterally.
- Acting from above, it elevates the 1st rib and thus acts as an accessory muscle of respiration.
Scalenus Anterior Muscle Relations
It is key muscle at the root of neck because many important structures are related to it.
Scalenus Anterior Muscle Anterior relations:
- Two nerves: Phrenic nerve and descendens cervicalis
- Two arteries: Transverse cervical and suprascapular
- Two veins: Anterior jugular and subclavian
- Two muscles: Inferior belly of omohyoid and sternocleidomastoid
Scalenus Anterior Muscle Posterior relations:
- Branchial plexus (lower trunk)
- Subclavian artery (second part)
- Cervical pleura
- Suprapleural membrane
Scalenus Anterior Muscle Lateral:
Trunks of brachial plexus
Scalenus Anterior Muscle Medial:
Thyrocervical trunk
Scalenus Anterior Muscle Applied anatomy
- Scalene syndrome occurs if roots of brachial plexus and subclavian artery are compressed between scalenus anterior muscle and first rib.
- Cervical rib syndrome occurs when cervical rib passing through a gap between scalenus anterior and scalenus medius muscles compressing lower trunk of brachial plexus and subclavian artery.
- Clinically these syndromes present as:
- Tingling and numbness in the little finger and medial half of ring fingers due to involvement of T8 and T1.
- Absence of radial pulse due to compression of subclavian artery.
Question 3. Describe the Scalenus Medius Muscle in brief.
Answer.
It is the longest and largest scalene muscle.
Scalenus Medius Muscle Origin
From the posterior tubercles of transverse processes of C2 to C6 vertebrae.
Scalenus Medius Muscle Insertion
On the superior surface of 1st rib behind the groove for subclavian artery and in front of tubercle of 1st rib.
Scalenus Medius Muscle Nerve supply
Ventral rami of C3 to C8 spinal nerves.
Scalenus Medius Muscle Actions
Same as scalenus anterior.
Question 4. Describe the boundaries of scalene triangle in brief and enumerate the structures passing through it.
Answer.
Scalene Triangle Location
Root of the neck
Scalene Triangle Boundaries
Scalene Triangle Anterior:
Scalenus anterior
Scalene Triangle Posterior:
Scalenus medius
Scalene Triangle Base:
1st rib
Scalene Triangle Apex:
Meeting point of the scalenus anterior and scalenus medius
Scalene Triangle Structures passing through this triangle
- Subclavian artery
- Brachial plexus (lower trunk)
Scalene Triangle Applied anatomy
- Scalene syndrome: Occurs due to compression of the lower trunk of brachial plexus and subclavian artery in scalene triangle due to (a) spasm of scalene muscles or (b) presence of cervical rib.
- Clinically, it presents as:
- Tingling and numbness in the area of distribution of C8 and T1.
- Progressive wasting of intrinsic muscles of the hand due to involvement of C8 and T1.
- Absence of radial pulse due to compression of the subclavian artery.
Question 5. Describe the boundaries and contents of Scalenovertebral Triangle (triangle of vertebral artery).
Answer.
Scalenovertebral Triangle Location
Deep, at the front of the root of neck.
Scalenovertebral Triangle Boundaries
Scalenovertebral Triangle Medial:
Longus colli
Scalenovertebral Triangle Lateral:
Scalenus anterior
Scalenovertebral Triangle Apex:
Transverse process of C6 vertebrae
Scalenovertebral Triangle Base:
First part of the subclavian artery
Scalenovertebral Triangle Contents
- First part of the vertebral artery
- Thyrocervical trunk and vertebral artery
- Stellate (inferior cervical sympathetic) ganglion
- Thoracic duct (left side only)
- Ansa subclavia
Question 6. What are Subclavian Arteries? List their branches.
Answer.
The right subclavian artery is a branch of brachiocephalic trunk, whereas the left subclavian artery is a direct branch of arch of aorta. On each side, the subclavian artery extends up to the outer border of the 1st rib.
Subclavian Arteries Branches
Each subclavian artery is divided into three parts by scalenus anterior muscle:
- First part (medial to scalenus anterior) gives rise to:
- Thyrocervical trunk
- Vertebral artery
- Internal mammary artery (internal thoracic artery)
- Costocervical trunk (on the left side)
- Second part (behind the scalenus anterior) gives rise to costocervical trunk on the right side.
- Third part (lateral to scalenus anterior): Usually does not give any branch, but sometimes it may give origin to dorsal scapular artery.
Question 7. Describe the Vertebral Artery in brief.
Answer.
Vertebral Artery Definition
- It is the largest branch of subclavian artery and is one of the two main sources of blood supply to the brain.
- It runs upwards to enter the foramen transversarium of C6 vertebra. It then passes successively through the corresponding foramina of other cervical vertebrae above to reach the upper surface of C1 vertebra. Here, it turns medially in the suboccipital triangle to finally enter the cranial cavity through foramen magnum. Here, it joins the vertebral artery of opposite side at the lower border of pons to form the basilar artery.
Vertebral Artery Parts
The vertebral artery is divided into four parts:
- First part: It lies in the triangle of vertebral artery.
- Second part: It passes through the foramina transversaria of C6 to C1 vertebrae.
- Third part: It lies in the suboccipital triangle.
- Fourth part: It lies in the cranial cavity.
Vertebral Artery Branches
- In the neck:
- Spinal branches
- Muscular branches
- In the cranial cavity:
- Meningeal branch
- Anterior spinal branch
- Posterior spinal branch
- Posterior inferior cerebellar artery
- Medullary branches
Question 8. Describe the origin, course and termination of Internal Carotid Artery. List its parts and their branches.
Answer.
Internal Carotid Artery Origin, course and termination
- It begins as one of the two terminal branches of common carotid artery at the upper border of the thyroid cartilage.
- It enters the cranial cavity through the carotid canal and foramen lacerum.
- In the cranial cavity, it traverses through the cavernous sinus and finally terminates at the base of brain by dividing into anterior and middle cerebral arteries.
Internal Carotid Artery Parts and branches
- Cervical part:
- No branch
- Petrous part:
- Caroticotympanic branches to the middle ear
- Pterygoid branch, which enters the pterygoid canal
- Cavernous part:
- Cavernous branches to the wall of cavernous sinus and trigeminal ganglion
- Hypophyseal branches to the hypophysis cerebri
- Meningeal branches
- Cerebral part
Question 9. Describe the Cervical Sympathetic Chain in brief and discuss its applied anatomy.
Answer.
Cervical Sympathetic Chain Location and extent
- It is part of the sympathetic chain that lies in front of the transverse processes of the cervical vertebrae and neck of 1st rib.
- It continues upwards into the carotid canal as internal carotid nerve and downwards as thoracic part of the sympathetic chain.
Cervical Sympathetic Chain Ganglia
The cervical sympathetic chain possesses three ganglia:
- Superior cervical ganglion: It lies in front of the transverse processes of C2 and C3, and represents the fused C1 to C4 primitive ganglia.
- Middle cervical ganglion: It lies in front of the transverse process of C6 and represents the fused C5 and C6 primitive ganglia.
- Inferior cervical ganglion: It lies in front of the transverse process of C7 and neck of 1st rib, and represents the fused ganglia of C7 and C6 primitive ganglia. It often fuses with T1 ganglion to form stellate ganglion.
Cervical Sympathetic Chain Applied anatomy
Horner syndrome:
It occurs due to the lesion of cervical sympathetic chain involving T1 fibres supplying head and neck.
Horner syndrome Clinical features
- Anhydrosis (loss of sweating)
- Partial ptosis (partial drooping of the upper eyelid)
- Myosis (constriction of pupil)
- Enophthalmos (recession of the eyeball)
- Absence of the ciliospinal reflex
Question 10. Write a short note on the Cervical Plexus.
Answer.
Cervical Plexus Formation and location
It is formed by the vertebral rami of C1 to C4 nerves, and lies on levator scapulae and scalenus medius muscles deep to prevertebral layer of deep cervical fascia.
Cervical Plexus Important named branches
- Lesser occipital
- Great auricular
- Transverse cervical
- Supraclavicular
Question 11. Describe the phrenic nerve in brief and discuss its applied anatomy.
Answer.
Phrenic Nerve Origin
It is formed by ventral rami of C3 to C5, with chief contribution being from C4.
Phrenic Nerve Course
It first descends obliquely on the anterior surface of scalenus anterior. Then it runs vertically downwards on the cervical pleura to enter thoracic cavity behind the 1st costal cartilage.
Phrenic Nerve Branches and distribution
- Motor branches to diaphragm
- Sensory branches to central part of the diaphragm, pleura, pericardium and peritoneum (subdiaphragmatic)
Phrenic Nerve Applied anatomy
- Damage of phrenic nerve in the neck leads to paralysis of corresponding half of the diaphragm. The paralysed half of diaphragm becomes relaxed and pushed up into thorax by the positive intra-abdominal pressure. This leads to collapse of the lower lobe of the lung.
- The fibres of C5 instead of joining phrenic nerve at its commencement may join it at the thoracic inlet through a communication received from nerve to subclavius. This communication is referred to as accessory phrenic nerve. In phrenic avulsion, the accessory phrenic nerve if present should be cut, otherwise C5 fibres will escape and diaphragm may continue to function and defeat the whole purpose of phrenic crush.
- In pleurisy, the pain from diaphragmatic pleura may be referred to shoulder region, which receives nerve supply from some spinal segments as that of phrenic nerve, i.e. C3 and C4.
Question 12. Describe the internal jugular vein in brief.
Answer.
Internal Jugular Vein Formation, course and termination
The internal jugular vein begins as direct continuation of the sigmoid sinus at the jugular foramen of skull and terminates by uniting with the subclavian vein behind th Internal Jugular VeinTributaries
- Inferior petrosal sinus
- Common facial vein
- Pharyngeal veins
- Lingual vein
- Superior thyroid vein
- Middle thyroid vein
- Kocher’s vein (if present)
Internal Jugular Vein Applied anatomy
- The internal jugular vein is easily accessible in the lesser supraclavicular fossa and is used for recording jugular venous pulse pressure.
- In congestive heart failure (CHF), it is the most dilated vein.
Question 13. Describe the Atlanto-Occipital joints in brief.
Answer.
These are a pair of joints between the superior articular facets of atlas and condyles of the occipital bone.
Atlanto-Occipital joints Classification
Synovial joint of ellipsoid variety.
Atlanto-Occipital joints Articular surfaces
- Condyle of occipital bone, superiorly.
- Superior articular facet on the lateral mass of atlas, inferiorly.
- The articular surfaces are reciprocally curved.
Atlanto-Occipital joints Ligaments
These are
- Fibrous capsule.
- Anterior and posterior atlanto-occipital membranes.
Atlanto-Occipital joints Movements
Nodding movements, i.e. the flexion and extension of the head that occurs when indicating approval; hence, these movements are also called ‘yes movements’.
Question 14. Describe the Atlantoaxial Joints in brief.
Answer.
Atlantoaxial joints
These are three in number: median atlantoaxial joint and right and left lateral atlantoaxial joints.
Atlantoaxial Joints Classification:
- Median atlantoaxial joint: Pivot type of synovial joint
- Lateral atlantoaxial joint: Plane type of synovial joint
Atlantoaxial Joints Articular surfaces and ligaments
- Median Atlantoaxial Joint: It is formed between the dens of axis and the anterior arch of the atlas. The articular facet on the anterior aspect of dens articulates with the facet on the posterior surface of the anterior arch of atlas. Posteriorly between the base of dens of axis and transverse ligament of atlas lies a synovial bursa. It is a pivot type of synovial joint.
- Lateral Atlanto-axial Joints: It is formed between the superior articular facet of axis and inferior articular facet of atlas. It is a plane type of synovial joint.
Atlantoaxial Joints Movements
The atlanto-occipital joints are responsible for rotation of the head. They permit the head to be turned from side-to-side, e.g. when rotating the head to indicate disapproval. Hence, these movements are also called ‘no movements’.
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