Anatomy 6: Muscles of the Head, Neck, and Back

PSK 4U

S. Kelly - North Grenville DHS

Muscle Functions

•Movement: contraction moves bones through ROM

•Support: muscles provide support and body shape

•Temperature regulation: involuntary contraction (shivering) provides heat (for control indicators, see nervous system slides… when they are available…)

Muscle Terminology

•Origin: the least moveable part of the muscle; usually the proximal attachment

•Insertion: the most moveable part; usually the distal attachment

•Action: function performed by the muscle when activated

•Innervation: nerve responsible for message transmission

Properties of muscle cells

• Irritability

•Contractability

•Elasticity

•Extensibility

•Conductivity

** Basics and review (?)

Muscle nomenclature (review)

•Action/function: flexor, adductor

•Shape: deltoid, trapezius

• Location: tibialis anterior, biceps femoris

•Number of heads or divisions: biceps, triceps

•Direction of fibres: transversus

•Points of attachment: sternocleidomastoid

Muscle Facts

•Each fibre is thinner than a human hair and can support up to 1,000x its own weight

•No two muscles have exactly the same function

•Muscles use energy: an extra 1lb of muscle means your body requires an extra 50 calories of energy per day (approx)

•There are over 650 muscles in the human body

Frontalis

•Originates on the cranial aponeurosis

• Inserts on the orbicularis oculi muscle (no bony attachments)

•Raises eyebrows and wrinkles forehead

•Facial nerve

Temporalis and Occipitalis

•Temporalis

•Originates on temporal and sphenoid bones

•Inserts on the coronoid process of the mandible

•Elevates and retracts the mandible (mastication)

•Innervation: deep temporal

•Occipitalis

•Originates superior nuchal line and mastoid process

•Inserts cranial aponeurosis

•Moves scalp back (posteriorly)

•Posterior facial nerve

Orbicularis Muscles

•Occuli

•Originates frontal bone, lacrimal bone

•Inserts on a muscle at the lateral corner of eye responsible for spontaneous blinking

•Action: closing eyelids

•Temporal and zygomatic facial nerves

•Oris

•Origin maxilla, mandible

•Inserts: skin around lips

•Is actually 4 separate quadrants that appear to be one circular muscle.

•Puckers lips, referred to as “kissing muscle”

Platysma

•Origin: Subcutaneous tissue near clavicle

• Insertion: Base of mandible, skin of cheek, orbicularis oris

•Action: moves corners of mouth down as in frowning (see: it really does take more effort to frown than smile!) AND moves skin of neck superiorly when clenching teeth

• Inervation: cervical branch of facial nerve

Masseter

•Superficial head (larger)

•Origin: zygomatic process

• Insertion: Mandible

•Action: mastication (chewing)

• Innervation: mandibular division of trigeminal nerve

Sternocleidomastoid

•Origin: manubrium of sternum and clavicle

•Insertion: mastoid process

•Action: flexion and rotation of the head

•1 = anterior fibres

•2 = posterior fibres

•Innervation: ipsilateral accessory nerve (motor)

•Also, dorsal primary rami of C2, C3 (proprioception, sensation)

Splenius Capitis

•Origin: spinous processes of C7, T1-3 or 4

• Insertion: mastoid process and occipital bone

•Action: head/neck extension

• Innervation: dorsal rami of C3, C4

Rhomboid major

•Origin: spinous processes T2-T5, supraspinous ligament• Insertion: medial

border of scapula•Action: retraction,

elevation of scapula• Innervation: dorsal

scapular nerve

Rhomboid minor

•Origin: nuchal ligament, spinous processes of C7, T1

• Insertion: medial border of scapula

•Action: elevation, retraction of scapula

• Innervation: dorsal scapular nerve (C5)

Semispinalis Capitis

• Deep muscle (below trapezius

• Origin: C4-C7, and T1-T6

• Insertion: nuchal line, upper cervical vertebrae

• Innervation: dorsal rami of spinal nerves

• Action: head and neck rotation

• Whiplash muscle

Erector Spinae Group

•3 muscles: iliocostalis (1), spinalis (3), longissimus (2)

•Action: extension, lateral flexion, and support of the spine

Latissimus Dorsi

• Origin: lumbar and thoracic vertebrae, iliac crest, sacrum

• Insertion: proximalhumerus

• Action: adduction, extension, internal rotation of arm

• Innervation: long scapular nerve

• **Actually 6 groups of independently coordinated fibres

Trapezius

• Origin: occipital bone, thoracic and cervical vertebrae, supraspinal ligament

• Insertion: Spine of scapula, clavicle

• Action: scapular elevation, retraction, depression

• Innervation: Vent. Rami of C3, C4 (sens); accessory