MUSCLES OF HEAD, NECK, TRUNK

I.   NAMING OF MUSCLES
-- read pp. 312-313

II.  MUSCLES OF FACIAL EXPRESSION

A.  Epicranius: occipitofrontalis muscle and an epicranial aponeurosis

1.  Frontal belly of occipitofrontalis: elevates eyebrows and wrinkles skin of forehead

2.  Occipital belly of occipitofrontalis: retracts scalp slightly

B.  Orbicularis Oculi: closes eyes

C.  Orbicularis Oris: closes mouth and purses lips

D.  Zygomaticus Major: elevates corner of mouth    

                                
E.  Depressor Anguli Oris: depresses corner of mouth

F.  Buccinator: pulls cheeks against teeth when chewing

G.  Platysma: tenses skin of neck, and depresses lower lip

III. MUSCLES OF MASTICATION

-- Definition of mastication: chewing
-- all elevate the mandible, some perform additional functions:

A.  Masseter:  elevates and protracts mandible

B.  Temporalis: elevates and retracts mandible

C.  Medial Pterygoid: elevates mandible and moves mandible side to side

D.  Lateral Pterygoid: same as medial pterygoid

IV.  MUSCLES OF THE TONGUE    
1.  Genioglossus: protracts (protrudes) tongue

                             
2.  Styloglossus: retracts tongue

3.  Hyoglossus: depresses tongue

V.   NECK MUSCLES
A.  Posterior Neck Muscles

1.  Sternocleidomastoid: each rotates head to one side, together: flex the head/neck

2.  Splenius Capitis: each rotates head to one side, together: extend the head/neck

B.  Anterior Neck Muscles

1.  Suprahyoid muscles

a.  Digastric: elevates hyoid and depresses mandible

b.  Stylohyoid: elevates hyoid bone

c.  Mylohyoid: elevates hyoid and raises floor of mouth

d.  Geniohyoid: elevates hyoid bone

 

2.  Infrahyoid muscles

a.  Sternohyoid: depresses hyoid

b.  Omohyoid: depresses hyoid

c.  Sternothyroid: depresses thyroid cartilage

d.  Thyrohyoid: depresses hyoid bone and raises thyroid cartilage

VI.  BACK MUSCLES
A.  Superficial Back Muscles

B.  Deep Back Muscles (Muscles of the vertebral column)

1.  Quadratus Lumborum: together: extend lumbar vertebral column, unilaterally: each laterally flexes vert column

2.  Erector Spinae group of muscles

-- extend the vertebral column
-- consists of:

a.  Iliocostalis:

b.  Longissimus:

c.  Spinalis:

VII. THORAX MUSCLES
A.  Superficial Thorax Muscles

B.  Deep Thorax Muscles

1.  Diaphragm: contraction pulls the central portion down, increasing vertical dimensions of thorax

2.  External Intercostals: elevate ribs during inhalation

3.  Internal Intercostals: depress ribs during exhalation

VIII. ABDOMINAL MUSCLES
A.  External Abdominal Oblique:

B.  Internal Abdominal Oblique:

C.  Transversus Abdominis:

For muscles A,B, C:
*unilaterally: laterally flex vertebral column
* together: flex vertebral column and compress abdominal wall

D.  Rectus Abdominis:
* flex vertebral column and compress abdominal wall

IX.  MUSCLES OF THE PELVIC FLOOR AND PERINEUM

–  functions include:
1)  close inferior opening of pelvis

2)  support the pelvic organs

This muscle depresses the mandible:

a. masseter

b. digastric

c. temporalis

d. lateral pterygoid

e. obicularis oris