Muscles of The Neck

Question 1

What are the muscles in the face?

Answer 1

skeletal muscles
* collectively known as muscles of facial expression or Mimetic Muscles
* Not all muscles of expression are in the face e.g. Platysma muscle
* Branchial Arch Origins
* Have a common cranial nerve source for motor supply-Motor division of Cranial Nerve VII/facial nerve

Question 2

What are muscles in the neck?

Answer 2

• skeletal muscles
  
  • One of the muscles of the neck is classified as a muscle of facial expression
  • Divisible into 4 sets depending on their actions
  • Muscles that move the head
  • Muscles that stabilise the hyoid
  • Muscles that maintain vertebral column
  • Muscle of Facial expression
  • Originate from somite
  • Innervated by spinal nerves

Question 3

What are the differences between muscles if the face and muscles of the neck?

Answer 3

• The neck has skin, superficial facia, platysma muscle, deep fascia (investing, pre-tracheal and pre-vertebral) then has bones/organs as the deepest
  
  • Superficial fascia is the connective tissue that connects the skin to the rest of the body and also has fat rejoins inside - in the neck it is fused with the platysma
  • Investing layer of deep fascia = surrounds all structures but we don’t know if it is present in the face .
  • Face has: skin, we assume that it has deep facial (investing, pre-tracheal and pre-vertebral) and bones/organs
  • In the face there is a matrix of connective tissue which we assume is the remnants of the degraded platysma muscle (called the SMAS)

Question 4

Name some of the muscles in the neck

Answer 4

• Trapezius Muscle
  
  • Sternocleidomastoid Muscle
  • Platysma Muscle
  • Strap Muscles
  • Spinal Muscles
  • Muscles of the neck are divisible into 4 sub-groups
    ○ Muscles that maintain the vertebral column
    § Paraspinal Muscles
    § Spinal Muscles
    ○ Muscles that move the head
    § These also form Triangles of the neck
    ○ Muscles that stabilise the hyoid bone
    ○ 1 Muscle of Facial Expression
    § Platysma influences facial expression

Question 5

What are the muscles that move the head?

Answer 5

• Trapezius Muscle-Primarily a muscle of the shoulder girdle and It also displaces the head
  
  • Sternocleidomastoid Muscle-main muscles that moves the head
  • They form the triangular boundaries
  • Move head and implications thus moving the sensory organs e.g. eyes and nose
  • Their attachments allow for the neck to be divisible into anatomical triangles
  • Triangles of the neck
    ○ form a tidy basis for visualising demarcations between important structures of the region
    ○ have clinical importance in systematic examination and surgery in the neck

Question 6

What muscles form triangles on the neck?

Answer 6

• Trapezius Muscle-Primarily a muscle of the shoulder girdle and It also displaces the head
  
  • Sternocleidomastoid Muscle-main muscles that moves the head
  • They form the triangular boundaries

Question 7

Where are sternocleidomastoid muscles attached?

Answer 7

• Has 2 in the neck (one on each side)
  
  • Has attached to the sternal head and clavicle head
  • Attaches to the superior nouche line of the Occiptal bone
  • The attachment of at the mastered muscles causes the prudence of the master muscles
  • Supplied accessory nerve (spinal division on CN XI)

Question 8

How do the sternocleidomastoid muscles work?

Answer 8

• When active, it displaces the head in different direction depending on:
  ○ Which head is acting unilaterally
  § Actions of the Sternal Head
  § dictions of Clavicular Head
  § Both heads acting together
  ○ Both muscles acting bilaterally
  
  • Causes lateral head flex (tile to the side) and to rotate head to the side if only one at hinge on its own
  • When both act together it can flex the head (move the head to look down)

Question 9

Where are trapezius muscles attached?

Answer 9

• Attaches to may vertebrae and anterior aspect of the clavicle
  
  • Has different parts: ascending head, transverse head and descending head
  • Acts together with its counter opposites

Question 10

How do the trapezius muscles work?

Answer 10

• Tilts head to the side and causes the head to raise
  
  • The Trapezius muscle also flexes the head
  • It is supplied by the Accessory Nerve (C3-C4)
  • Acting Unilaterally
    ○ It flexes the head ipsilaterally/On the same side of the body as the part being contracted
  • Acting bilaterally
    ○ The two muscles raise the head together with the vertebral column
    ○ This actions is known as dorsal flexion of the head (look up and down)

Question 11

What forms the triangles of the neck?

Answer 11

• Trapezius Muscle-Primarily a muscle of the shoulder girdle and It also displaces the head
  
  • Sternocleidomastoid Muscle-main muscles that moves the head
  • They form the triangular boundaries
  • Omohyoid muscles is the one running inbetweener which attaches the hyoid bone

Question 12

What muscles stabilise the hyoid bone?

Answer 12

• Muscles that attach to it above are called the suprahyoid and bellow are celled the infrahyoid
  
  • Infrahyoid depress the hyoid and suprahyoid raise the hold
  • These are also known/called strap muscles
  • Suprahyoid muscles
    ○ Digastric
    ○ Mylohyoid
    ○ Stylohyoid
    ○ Geniohyoid
    ○ Need to be able to identify
    ○ Form part of the floor of the mouth
    ○ Elevate hyoid and larynx Durning swallowing
  • Infrahyoid muscles
    ○ Strap Muscles
    ○ All supplied by the Ansa Cervicalis
    ○ Root values C1 to C3
    ○ Together, they act to depress the larynx during swallowing and speech
    ○ Sternothyroid
    ○ Sternohyoid
    ○ Omohyoid
    ○ Thyrohyoid
    ○ Need to be able to identify

Question 13

What is the platysma muscle?

Answer 13

• Develops From 2nd mesenchymal arch
  
  • Supplied by facial nerves and shares the nerve with other tissues
  • Could be the thinnest Muscle in the body
  • it covers most of the anterior and lateral aspect of the neck
  • It is a broad muscle which arises from the fascia that covers:
    ○ Upper segments of deltoid
    ○ Upper segments of pectoralis muscles
  • Its thin muscle fibres cross over the clavicle and proceed obliquely superiorly, laterally and medially over the neck
  • Disintegration if the platysma gives rise to the connective tissue in the head
  • Some of its fibres attach to the mandible Others fibres merge in the subcutaneous tissues of the lower head
  • Most of the platysma muscle fibres start to thin out as they cross into the superior aspect of the lower face to merge or blend in with the muscles around the angle and lower part of the oral cavity

Question 14

What is that SMAS?

Answer 14

• superficial musculoaponeurotic system
  
  • The platysma degenerates ad forms a connective tissue matric in the face called the SMAS
  • SMAS is often described as an organized fibrous network composed of the platysma
    muscle, parotid fascia, and fibromuscular layer covering the cheek
  • divides the deep and superficial adipose tissue of the face and has region-specific morphology
  • SMAS lies inferior to the zygomatic arch and superior to the muscular belly of the platysma
  • fibromuscular layer of the SMAS integrates with the superficial temporal fascia and frontalis muscle superiorly and with the platysma muscle inferiorly