Contents Of Vertebral Canal

Ligamentum Denticulatum

1. Ligamentum Denticulatum Definition: The pia mater on each side forms a narrow vertical ridge, called the ligamentum denticulatum .

2. Ligamentum Denticulatum Features

1. Ligamentum Denticulatum is extension of pia mater to dura mater. It pierces arachnoid mater.
2. Ligamentum Denticulatum is present between the ventral and dorsal nerve roots.
3. Ligamentum Denticulatum gives a series of triangular tooth-like processes which project from its lateral free border.
4. Each ligament has 21 processes;
   1st at the level of the foramen magnum, and
   Last between 12th thoracic and 1st lumbar spinal nerves.
5. The processes suspend the spinal cord in the middle of the subarachnoid space.

Body Fluids	Muscle Physiology	Digestive System
Endocrinology	Face Anatomy	Neck Anatomy
Lower Limb	Upper Limb	Nervous System

Read And Learn More: Face Anatomy Notes And Important Questions

3. Ligamentum Denticulatum Applied anatomy

1. Ligamentum Denticulatum identification helps the surgeon in locating the 1st lumbar nerve during operation.
2. Surgical sectioning of the lateral spinothalamic tract is called anterolateral cordotomy.
   Ligamentum Denticulatum is necessary to relieve intractable pain.
   In ths procedure, th incision is placed in front of the ligamentum denticulatum to access the lateral spinothalamic tract.

Lumbar Puncture

Lumbar Puncture Introduction: It is performed to obtain samples of cerebrospinal fluid for laboratory analysis.

1. Lumbar Puncture Location: Spinal cord ends at lower border of Ll vertebra. Hence, lumbar puncture is done between L3 and L4 spine.

2. Lumbar Puncture Landmark: A-line tangential to the highest points of the iliac crests passes through the lower border of the 4th lumbar vertebra or the interspace between the 4th and 5th lumbar vertebra.

3. Lumbar Puncture Procedure: Local anaesthetic drug is injected in the space between the 4th and 5th lumbar vertebrae and a spinal needle is inserted. Needle passes successively through

1. Skin,
2. Superficial fascia,
3. Supraspinous ligament,
4. Interspinous ligament (between the paired ligamentum flava),
5. Epidural space, and
6. Dura and arachnoid to enter the subarachnoid space.

4. Lumbar Puncture Applied anatomy: Lumbar puncture is done for the

1. Biochemical analysis of cerebrospinal fluid to diagnose type of meningitis.
2. To differentiate extradural and subdural haemorrhage.
3. For epidural and subdural anaesthesia (spinal anaesthesia)

Question: Enumerate the Cranial Nerves

1. Olfactory nerve (1st cranial nerve): It is the smallest cranial nerve.It is a nerve of smell.
It carries smell sensation from upper part of

1. Lateral wall of nose and
2. Nasal septum.

2. Optic nerve (2nd cranial nerve)

1. It is the nerve of vision.
2. It is the thickest cranial nerve, hence whatever you see you rarely forget.
3. It is not a true cranial nerve. It is prolongation of brain since it is covered by meninges.
4. It is not covered by neurolemmal sheath. Hence, it does not regenerate. –
5. It is supplied by central artery of retina which is an end artery. Rupture of this artery results into blindness.

3. Oculomotor (Oculo-eyeball, motor-ovement) (3rd cranial nerve)

1. It is nerve of the muscles of eyeball.
2. It supplies all the following muscles of eyeball except lateral rectus and superior oblique.
   The muscles supplied by oculomotor nerve are

1. Levator palpebrae superioris,
2. Superior rectus,
3. Medial rectus,
4. Inferior rectus, and
5. Inferior oblique.

4. Trochlear (Trochlea-pulley) (4th cranial nerve): It has the longest intracranial course.
It is the motor nerve which supplies the superior oblique muscle.
The superior oblique muscle winds around trochlea and gets inserted into eyeball.
Hence, the nerve is called trochlear.

5. Trigeminal (5th cranial nerve): It is the largest sensory cranial nerve.It has three roots

1. Ophthalmic
2. Maxillary
3. Mandibular
4. Ophthalmic, and
5. Maxillary divisions are purely sensory.
   They are sensory to scalp and area of face excluding lower jaw.
6. Mandibular division is mixed. It carries the sensation of

Skin of

1. Scalp,
2. Lower jaw, and
3. External ear.

General sensations of anterior two-thirds of tongue,

Temporomandibular joint,

Secretomotor fibres to parotid gland.

It supplies the

1. Muscles of mastication
2. Masseter,
3. Temporalis,
4. Medial, and
5. Lateral pterygoid

Tensor tympani,

Tensor palatini,

Anterior belly of digastric, and

Mylohyoid.

6. Abducent (abducent-abduction) (6t cranialnerve) LR6.
It is motor nerve, supplying lateral rectus.
It rotates th eyeball laterally. It is nerve having intradural course.

7. Facial (7th cranial nerve): It has the largest intraosseous course.It is motor to the muscles of

1. Facial expression,
2. Muscles of scalp,
3. Muscles of external ear,
4. Muscle of middle ear, i.e. stapedius,
5. Buccinator,
6. Posterior belly of digastric, and
7. Stylohyoid.
8. It carries special sensation of taste from anterior two-thirds of tongue.
9. It carries secretomotor fibres to

Lacrimal gland

Submandibular, and

Sublingual glands

To recollect the distribution of muscles of facial nerve

1. Slide your palm on the face and say muscles of facial expression
2. Slide on scalp and say muscles of scalp
3. Slide on external ear and say muscles of external ear, i.e. auricularis anterior auricularis posterior, auricularis superior
4. Slide in front of tragus of ear and say muscle of middle ear, i.e. stapedius
5. Slide on the cheek and say buccinator
6. Slide at the base of mandible and say platysma
7. Slide from angle of mandible to styloid process and say posterior belly of digastric
8. Slide from styloid process to hyoid and say stylohyoid

8. Vestibulocochlear (8th cranial nerve): It has two parts.

1. Vestibular nerve is the nerve of balance.
2. Cochlear nerve is the nerve of hearing.

9. Glossopharyngeal (9th cranial nerve): It is

Sensory part: It is sensory of

1. Posterior one-third of tongue,
2. Middle ear cavity,
3. Carotid body,
4. Carotid sinus, and
5. Palatine tonsil

It carries special sensation from posterior one-third of tongue

Motor nerve of muscle of pharynx, i.e. stylopharyngeus.

It is secretomotor to parotid gland.

10. Vagus (10th cranial nerve). Cranial nerve having largest extracranial course.

It is motor nerve of the

1. Muscles of larynx,
2. Soft palate, and
3. Pharynx.

It is sensory nerve of

1. Most posterior part of tongue, and
2. Mucous membrane of larynx.

11. Accessory (11th cranial nerve): It has spinal part and cranial part.

1. The spinal part is motor to muscles of neck, i.e. trapezius and sternocleidomastoid.
2. The cranial part takes part in the pharyngeal plexus which supplies muscles of pharynx and soft palate.

12. Hypoglossal (12th cranial nerve): It is motor nerve to the muscles of tongue.

Trapezius

1. Trapezius Proximal attachments

1. Medial one-third of superior nuchal line
2. External occipital protuberance
3. Ligamentum nuchae
4. Spines of 7th cervical to 12th thoracic vertebrae
5. Corresponding supraspinous ligaments

2. Trapezius Distal attachments: It is inserted into

1. Upper fibres into the posterior border of lateral one-third of clavicle.
2. Middle fibres into the medial margin of the acromion and upper lip of the crest of spine of the scapula.
3. Lower fibres on the apex of triangular area at the medial end of the spine, with a bursa intervening.

3 Trapezius Nerve supply

Trapezius Motor: Spinal root of accessory nerve (Xlth cranial nerve)
Trapezius Sensory: Proprioceptive by C3 and C4
Trapezius Actions:

1. The principal action of the trapezius is to rotate the scapula during abduction of the arm beyond 90°.
2. Upper fibres act with levator scapulae and elevate the scapula as in shrugging.
3. Middle fibres with rhomboids retract the scapula.
4. Upper and lower fibres with serratus anterior rotate the scapula forwards round the chest wall and play an important role in abduction of the arm beyond 90°.

Testing the muscle: Clinically, the muscle is tested by asking the patient to shrug his shoulder against resistance.

Important events taking place at C6 vertebra

1. Structures end

1. Larynx
   Laryngopharynx

2. Structures begin

1. Trachea
2. Oesophagus

3. Structures present

1. Carotid tubercle (anterior tubercle of transverse process of C6 vertebra).
2. Middle cervical sympathetic ganglion.
3. Superior parathyroid gland.
4. Ansa cervicalis
5. Widest breadth of spinal cord

4. Structure enters: Vertebral artery enters foramen transversarium of C6.

5. Apex of triangle

1. Scalenovertebral triangle (longus colli and scalenus anterior meet).

6. Inferior thyroid artery loops medially

7. Meeting of two bellies of omohyoid