Anatomy Lecture 12 Axial Musculature

Front 1

What is axial musculature?

Back 1

muscles that are associated with the axial skeleton.

Front 2

Muscles of facial expression

Back 2

frontalis, orbicularis oculi, orbicularis oris, zygomaticus major, depressor anguli oris, platysma. The two orbicularis are sphincters. All these recieve motor innervation from branches of the facial nerve (CN VII).

Front 3

Muscles of mastication

Back 3

Temporalis, masseter, lateral and medial pterygoid. These four muscles act directly on the mandible for chewing. They are all innervated by the 3rd branch of the trigeminal nerve (CN-V)-V3.

Front 4

Muscles of the oral cavity

Back 4

Genioglossus. Cranial nerve 12, hypoglossal nerve

Front 5

Extraocular muscles

Back 5

rectus muscles: lateral rectus, medial rectus, superior rectus, inferior rectus. Superior oblique, inferior oblique. These muscles act on the eyeball, moving it around within the bony orbit. Their innervation can be summarized by this pneumonic-LR6[SO4]^3. The lateral rectus is innervated by the 6th cranial nerve(abducens), the superior oblique is innervated by the 4th cranial nerve(trochlear) and the other extraocular muscles are innervated by the 3rd cranial nerve(occulomotor).

Front 6

Muscles of the Neck

Back 6

The key muscle of the neck is the sternocleidomastoid. It is innervated by the 11th cranial nerve(CN XI)-the accessory. It rotates and orients the face craninally. Divides the neck into two triangles. The anterior is an upside down triangle. The attachments(as in the name) are the sternum, the clavicle and the mastoid process

Front 7

More muscles of the neck

Back 7

The hyoid bone is a bony landmark of the neck. Muscles attached are thin, flat, and strap-like in shape. Divided into suprahyoids(above hyoid) and infrahyoids(below hyoid). These muscles aid in swallowing and can also move the larynx superiorly. They do this by elevating and depressing the hyoid.

Front 8

More muscles of the neck

Back 8

Ansa cervicalis: a loop of cervical nerves

Front 9

Muscles of the thoracic wall

Back 9

The thoracic wall is composed of 3 layers superficial to deep: external intercoastals, internal intercoastals and innermost intercoastals. These are found between the ribs. Their innervation is directly from the ventral ramus of the spinal nerve at each level. They function in elevating the ribs during respiration.

Front 10

The muscles of the anterolateral abdominal wall

Back 10

external oblique, internal oblique, transversus abdominis. Anteriorly, one straight muscle on each side of the midline of the abdomen, the rectus abdominis. These muscles are also innervated by the ventral rami of spinal nerves. Function in compressing the abdominal viscera.

Front 11

Superficial muscles of the back

Back 11

Splenius capitus, levator scapulae, rhomboids, trapezius.

Front 12

Deep muscles of the back

Back 12

These are collectively referred to as erector spinae muscle mass. They are postural muscles for flexing/extending the spine. The serratus posterior superior and inferior act as fascial retinacula holding this deeper muscle group in place. These muscles are also innervated segmentally by the dorsal ramus of each spinal nerve they cross.