Review of Trapezius & Sternocleidomastoid Muscle + their Relation to Investing Fascia

Review of Trapezius:

- An extrinsic or superficial muscle of the back.

Functions: Assist in rotating the scapula during the abduction of the humerus above the horizontal; Upper fibres elevate, middle fibres adduct and lower fibres depress scapula.

Sri: The classification of the fibres are based on their structure i.e. upper fibres are descending fibres; middle fibres transverse & lower fibres are ascending.

Origin: Superior nuchal line, external occipital protuberence, ligamentum nuchae, spinous processes of CVII to TXII.

Insertion: Lateral 1/3 of clavicle, acromion, spine of scapula

Innervation: Motor - accessory nerve(CN XI); Proprioception - C3 and C4

Review of Sternocleidomastoid (aka Sternomastoid muscle)

Function: Individually - tilts head towards shoulder on same side; rotates head to turn face to opposite side, Acting together - draw head forwards

Origin: Sternal head- Upper part of anterior surface of manubrium
Clavicular head- Superior surface of medial 1/3 of the clavicle

Insertion: Lateral 1/2 of superior nuchal line, Lateral surface of mastoid process

Innervation: Accessory nerve (CN XI) and branches from anterior rami of C2 to C3 (C4)

Relations to Investing Fascia:

Posteriorly, the investing fascia attaches to the ligamentum nuchae and the spinous process of CVII. As this fascial layer moves anteriorly, it splits to enclose the trapezius muscle, reunites into a single layer to form the roof of the posterior triangle, spilts again to surround the sternocleidomastoid muscle, and reunites again to join its twin from the other side.

Contributed by John Lee

Source: Gray's Anatomy for Students

Atlanto-occipital and Atlanto-axial joint

Atlanto-occipital joint

-(articulation between the atlas and the occipital bone) consists of a pair of condyloid joints.

ligaments connecting the bones are:
1.Two Articular capsules
- synovial joint of condyloid type, loose capsules

2.Posterior atlantoöccipital membrane
broad but relatively weak
extend from anterior arch of atlas to posterior margin of foramen magnum

3.Anterior atlantoöccipital membrane
- broad, densely woven fibre ( strong)
- centrally they are continuous with anterior longitudinal ligament
- extend from anterior arch of atlas to anterior margin of foramen magnum

The movements permitted in this joint are:
1.flexion and extension, which give rise to the ordinary forward and backward nodding of the head
2.slight lateral motion to one or other (tilting of head)

Atlanto-axial articulation

-articulation of the atlas with the axis

three articulation facet:

2 lateral atlanto-axial joint (right and left)
- betweeen inferior facet of lateral mass of atlas and superior facet of axis.
- gliding type synovial joint

1 median atlanto-axial joint
- between den of axis and anterior arch of atlas
- pivot joint

movement permitted at this joint:
1.rotation of head
- cranium and atlas rotate on axis as a unit
- the dens of C2 is the pivot that is held in the socket formed by the tranverse ligament of the atlas

Ligament connecting the bone:
1.Superior and inferior longitudinal ligament (cruciate ligament)
- pass from transverse ligament to occipital bone superiorly and to body of C2 inferiorly
2.Alar ligament
-extend from side of transverse ligament to lateral margin of foramen magnum
3.Tectorial membrane
- strong superior continuation of posterior longitudinal ligament across the median atlanto-axial joint through foramen magnum to the centre floor of cranial cavity.
- run from C2 to internal surface of occipital bone covering alar and transverse ligament
4.Transverse ligament
- extend between the tubercles of the medial aspects of the lateral mass of C1 verterbrae


Contributed by Lawrence Oh

Boundaries and Contents of the Deep Styloid Region

(Pages & figures cited are from Drake et al, Gray's Anatomy for Students, Intl edition 2005)

Boundaries

Lateral: styloid process (pg 907)
Medial: posterolateral wall of pharynx
Anterior: infratemporal region
Posterior: atlas & axis aka C1, C2
Superior: base of skull
Inferior: posterior belly of digastric muscle (pg 907)

Contents

1. Internal carotid artery (pg 911)
2. Internal jugular vein (pg 913 fig. 8.162 & fig. 8.163; same for for following contents)
3. Glossopharyngeal nerve (IX)
4. Vagus nerve (X) & branches
5. accessory nerve (XI)
6. hypoglossal nerve (XII)
7. sympathetic trunk & superior cervical ganglion (pg 932)

Boundaries and Contents of the Orbit

(Legend: inn. - innervation)

Boundaries

• Below the anterior cranial fossa
• Anterior to the middle cranial fossa
• 4 walls (consisting of bones):
• roof (superior wall)
• medial wall
• lateral wall
• floor (inferior wall)

Contents

1. Eyeball
1. Eyelids:
   

   i. Skin, superficial fascia, thin layer of connective tissue, obicularis oculi

   ii. Orbicularis oculi: inn. facial nerve, closes eyelids

   1. palpebral part (in eyelids): medial palpebral ligament; lateral palpebral ligament

   2. orbital part: surrounds orbit

   3. lacrimal part: fibers on the medial border; attach to posterior lacrimal crest

   iii. Orbital septum: deep to palpebral part of orbicularis oculi; attaches to upper eyelid (levator palpebrae superioris) and lower eyelid (tarsus)

iv. Tarsal plates

1. large superior tarsus (upper eyelid)

2. smaller inferior tarsus (lower eyelid)

3. attaches to lateral palpebral ligament & medial palpebral ligament

4. tarsal glands: modified sebaceous glands; secrete oily substance that increase viscosity of tears and decrease rate of evaporation of tears from surface of eyeball

5. levator palpebrae superioris: raises eyelid; inserts into the anterior surface of superior tarsus; inn. oculomotor nerve

6. superior tarsal muscle: inferior surface of levator palpebrae superioris to upper edge of superior tarsus; inn. sympathetic fibres

2. conjuctiva: thin membrane covering posterior surface of each eyelid
3. glands: sebaceous & sweat glands associated with eyelash follicles
4. vessels
5. layers of the eyeball (e.g. sclera etc)
6. innervation:

i. sensory nerves: branches of trigeminal nerve

ii. motor nerves: facial nerve, oculomotor nerve, sympathetic fibers

2. Lacrimal apparatus: production, movement & drainage of fluid from surface of eyeball
1. Lacrimal gland & ducts

i. Position: anterior in the superolateral region of orbit

ii. Larger orbital part: in lacrimal fossa

iii. Smaller palebral part: inferior to levator palpebrae superioris

iv. Two parts are divided by levator palpebrae superioris

v. Ducts empty into lateral part of the superior fornix of conjunctiva (conjunctival sac)

2. Lacrimal lake: fluid then accumulates here
3. Lacrimal canaliculi: fluid drains into here (one canaliculus associated with each eyelid) via lacrimal punctum (opening)
4. Lacrimal sac: canaliculi join together to enter this sac
5. Nasolacrimal duct: each time you blink, lacrimal sac is compressed; fluid flows into this duct
6. Inferior meatus of nasal cavity: fluid ends up here
7. Innervation:

i. Sensory: lacrimal branch of ophthalmic nerve aka lacrimal nerve

ii. Parasympathetic: fibers joins the lacrimal nerve

iii. Sympathetic: follows similar path to parasympathetic except these fibers originate in the superior cervical ganglion; travel along the plexus surrounding the internal carotid artery

3. Innervations: Optic nerve (CN II), frontal nerve, lacrimal & nasociliary (V₁), oculomotor (III), Trochlear (IV), Abducent (VI), sympathetics and parasympathetics (ciliary ganglion)
4. Extraocular muscles
5. Adipose tissue and fascia
6. Specific nerves & vessels associated with each of these structures
1. Ophthalmic artery (10 branches)
2. 2 venous channels: superior & inferior ophthalmic veins
   

Describe the maxillary and mandibular nerves.

Maxillary nerve(V2) has 3 branches:
1)Zygomaticotemporal branch
2)Zygomaticofacial branch
3)Infra-orbital branch

-it exit the skull via foramen rotundum


Zygomaticotemporal
-exit zygomatic bone
-supply small area of anterior temple above the zygomatic arch

Zygomaticotfacial
-exit zygomaticofacial foramen
-supply skin on zygomatic bone

Infra-orbital
-exit maxilla via infra-orbital foramen and immediately divide into multi branch
-supply lower eye lid, side of nose, cheek and upper lip



Mandibular nerve (V3) has 3 branches as well:
1)Auriculotemporal branch
2)Buccal branch
3)Mental branch

-it exit the via foramen ovale


Auricotemporal
-enter the face posterior to the temporalmandibular joint
-passes through the parotid gland
-ascend just anterior to the ear
-supply external acoustic meatus & tympanic membrane & large area if temple

Buccal
-on the surface of buccinator muscle
-supply the cheek

Mental
-exit mandible via mental foramen
-immediately divide into multi branch
-supply skin and mucous membrane of lower lip and skin of chin


Contributed by Lawrence Oh

Anatomy Tasks : The Neck

a. Review the anatomy of the typical and atypical cervical vertebrae. (Shanthini)
b. Review atlanto-occipital and atlanto-axial articulations. (Lawrence)
c. Review trapezius & sternocleidomastoid & their relation to investing fascia (John); Explain how they define the anterior & posterior triangles. (Chris)
d. Explain how anterior triangle is subdivided; describe it's clinical significance. (Madhura)
e. Outline the features of the viscera of the neck - thyroid gland, cervical trachea & cervical oesophagus. (Ji Keon & Vivian)
f. Outline the fascial compartments of the neck & their contents. (Sri)

Please Note!
Special task for Christine: (Deep Fascia Regions) - Demonstrate the surface anatomy of the temporal, infratemporal & deep styloid regions and indicate clinical situations when this knowledge may be useful.

John

Temporal Fossa

The temporal fossa is a fan-shaped space that covers the lateral surface of the skull.

Boundaries:

Superior Margin: Pair of temporal lines (Superior and inferior temporal lines) that arch from the zygomatic process of the frontal bone to the supramastoid crest of the temporal bone
Lateral Margin: Temporal fascia, a fan-shaped aponeurosis overlying the temporalis muscle
Anterior Margin: Posterior surface of the zygomatic process of the frontal bone and the frontal process of the zygomatic bone
Inferior Margin: Zygomatic arch laterally; Infratemporal crest of the greater wing of the sphenoid medially

Contents:

Temporalis muscle:
Fanshaped muscle that orginates from the superior temporal line;
Fibres converge inferiorly to form a tendon which attaches to the anterior surface of the coronoid process of the mandible;
A powerful elevator of the mandible, retracts the mandible as well.
Innervated by the deep temporal nerves and blood supplied by the deep temporal arteries and middle temporal artery

Deep Temporal Nerves:
Usually 2 in number; originates from the anterior branch of the mandibular nerve(V3) in the infratemporal fossa;
Pass superiorly, around the infratemporal crest of the sphenoid bone, deep to the temporalis muscle to innervate it

Zygomaticotemporal Nerve:
Branch of the zygomatic nerve, a branch of the maxillary nerve (V2);
Originates in the pterygopalatine fossa; Penetrates temporal fascia to supply skin of the temple

Deep Temporal Arteries:
Usually 2 in number; Originate from the maxillary artery in the infratemporal fossa;
Travel superiorly with the deep temporal nerves; Anastomoses with Middle temporal arteries

Middle Temporal Artery:
A branch of the superficial temporal artery; Branches out just superior to the root of the zygomatic arch; Penetrates under the temporal fascia and goes deep to temporalis muscle; Supplies temporalis muscle and anastomoses with deep temporal arteries

Source: Gray's Anatomy for Students
Contributed by John Lee