KNES 2600 Lecture 10 Axial Musculature

Axial Musculature Grouping

Organized based on their location; muscles of the:

- head & neck

- vertebral column [superficial, intermediate, & deep]

- Respiration

- Abdominal wall

Muscles groups of the head and neck

- mouth region

- eye region

- scalp region

- neck region

- muscles of mastication

- muscles of head/neck movement

Mouth region muscles

[the majority of these muscles have a right & left]

- Orbicularis oris m.

compresses and purses lips

- Zygomaticus minor m.

retracts and elevates upper lip

- Zygomaticus major m.

retracts and elevates the corner of mouth e.g., laughing

- Buccinator m.

compresses cheeks

- Risorius m.

- Mentalis m.

orbicularis oris muscle

Flat band of muscle around the upper and lower lips

action: compresses and purses lips

Risorius muscle

a slender muscle on either side of the mouth that connects to the corners of the mouth

action: draws corner of the mouth laterally

zygomaticus minor muscle

Muscles on both sides of the face that extend from the zygomatic bone to the upper lips. [superior to the the major]

action: retracts and elevates upper lip [like when smiling]

zygomaticus major muscle

Muscles on both sides of the face that extend from the zygomatic bone to the angle of the mouth.

action: retracts and elevates the corners of mouth [like when laughing]

Mentalis muscle

triangular-shaped muscle located in the chin. It originates from the alveolar process of the mandible and inserts into the skin of the chin

action: protrude and evert the lower lip

buccinator muscle

Thin, flat muscle of the cheek between the upper and lower jaw

action: compresses cheeks

Muscles of the eye region

- orbicularis oculi m.

- corrugator supercilii m.

orbicularis oculi muscle

Ring muscle of the eye socket

action: closes the eyes

corrugator supercilii muscle

The small obliquely oriented muscle which lies between the frontal belly of the epicranius muscle and the orbicularis oculi muscle

action: pulls skin inferiorly and medially; wrinkles brow

Muscles of the nose region

- Procerus m.

- Nasalis m.

Procerus muscle

Covers the bridge of the nose

action: wrinkles the nose

Nasalis muscle

Two-part muscle which covers the sides of the nose

action: compresses bridge, depresses tip of nose, elevates corner of nostrils

Muscles of the scalp region

- occipito frontalis m.

+ frontal belly of occipitofrontalis m.

+ occipital belly of occipitofrontalis m.

+ epicranial aponeurosis

- Superior Auricularis m.

- Anterior Auricularis m.

- Posterior Auricularis m.

frontal belly of occipitofrontalis muscle

muscle on the forehead

action: raises eyebrows, wrinkles skin of forehead

occipital belly of occipitofrontalis muscle

back of the head

action: tenses and retracts scalp

epicranial aponeurosis

the long flat tendon that connects the frontal & occipital bellies of the occipitofrontalis m.

Superior Auricularis muscle

highest muscle connected to the ear

Anterior Auricularis muscle

furthest forward muscle connected to the ear

Posterior Auricularis muscle

furthest back muscle connected to the ear

Muscles of the Neck region

- platysma m.

- sternocleidomastoid m.

platysma muscle

Broad muscle extending from the chest and shoulder muscles to the side of the chin

action: tenses the skin of neck; pulls lower lip inferiorly

sternocleidomastoid muscle origin [2], insertion [1], & action

Origin:

manubrium; sternal end of clavicle

Insertion:

Mastoid process of temporal bone

action:

- unilateral: laterally flexes head to same side; rotates head opposite side

- bilateral: flexes neck; protracts head; aids in inhalation

Muscles of mastication

- masseter m.

- temporalis m.

masseter muscle

Insertion: Mandible

Origin: Zygomatic arch

action: closes jaw; assists in protraction, retraction, and side to side movement of the mandible

Temporalis muscle

muscles connecting to the sides of the head

action: close the jaw; assists in retracting and moving the mandible from side to side

Muscles that move the head and neck

- sternocleidomastoid m.

- scalenes mm.

+ anterior scalene m.

+ middle scalene m.

+ posterior scalene m.

scalene muscles: origin, insertion, and action

Origin:

transverse processes C2-C7

Insertion:

- anterior and middle - 1st rib

- posterior - 2nd rib

Action:

flexes and side bends the neck; elevates ribs 1 & 2 [aids in inhalation]

anterior scalene m.

middle scalene m.

posterior scalene m.

Scalene hiatus

opening formed by the anterior and middle scalene muscles

it allows for the passage of the subclavian artery & nerve bundles.

Thoracic outlet syndrome

Compression syndrome of upper limb neurovascular bundle at the level of scalene muscles and first rib. [the scalene hiatus is too small & compressed]

can be tested using the Adson Maneuver

Layers of the Muscles of the vertebral column

- Superficial layer [extrinsic back muscles]

- Intermediate layer [extrinsic back muscles]

- Deep layer [intrinsic or true back muscles]

All muscles of the vertebral column divided into layers

Muscles of respiration

- serratus posterior superior m.

- serratus posterior inferior m.

serratus posterior superior muscle origin, insertion & action

Origin:

Spinous processes of C7-T3

Insertion:

superior border of ribs 2-5

Action:

elevates ribs, aids in inhalation

serratus posterior inferior muscle origin, insertion & action

Origin:

spinous processes T10-L3

Insertion:

inferior border of ribs 9-12

Action:

depresses ribs, aids in inhalation

Superficial intrinsic back muscles

- Splenius muscle:

splenius cervicis & splenius capitis m.

splenius cervicis muscle origin [2] & insertion[1]

Origin:

ligamentum nuchae; spinous processes T3-6

Insertion:

Transverse process C1-3

Splenius capitis m. origin[2] & insertion

Origin:

ligamentum nuchae; spinous processes C7-T4

Insertion:

mastoid process & occipital bone

Intermediate intrinsic back muscles

- Erector Spinae muscles

consists of 3 columns [lateral to medial]

+ iliocostalis thoracis m.

+ longissimus thoracis m.

+ spinalis group

Erector Spinae muscles collective origin [4], insertion [3], and action

aka. iliocostalis, longissimus & spinalis groups [columns] of the Spinae muscles

Origin:

iliac crest, sacral crest, lumbar spinous processes, and thoracodorsal fascia

Insertion:

vertebral transverse processes, ribs, & mastoid process

iliocostalis thoracis m.

most lateral erector spinae muscle

goes from the ilium of the pelvis all the way to the 1st rib

longissimus thoracis m.

longest erector spinae muscle sitting in-between the others.

goes from the lumbar region to the back of the head.

Deep intrinsic back muscles

- Semispinalis capitis m.

- Multifidus m.

- Rotatores m. [brevis & longus]

- interspinales

- intertransversarii m.

collective actions of all deep intrinsic back muscles

- stabilizes and provides delicate adjustment of vertebrae; slightly extends and rotates vertebrae

(- Semispinalis m.

- Multifidus m.

- Rotatores [brevis & longus]

- interspinales

- intertransversarii )

semispinalis capitis muscle origin [1] & insertion [2]

Origin:

Transverse processes T1-10

Insertion:

Occipital bone and spinous processes C2-T5

multifidus muscle origin [2] & insertion [1]

Origin:

sacrum and transverse processes of each vertebra

Insertion:

spinous process of the 3rd or 4th more superior vertebra

rotatores muscle [brevis & longus] origin [1] & insertion [1]

origin:

T.P. of vertebra

Insertion:

S.P. of superior vertebra

interspinales origin & insertion

origin:

S.P. of vertebra

Insertion:

S.P. of superior vertabra

intertransversarii muscle origin and insertion

Origin:

TP of vertebra

Insertion

TP of superior vertebra

Spinal flexors

- Quadratus lumborum muscle

Quadratus lumborum muscle origin [1], insertion [2] & action

Origin:

iliac crest

Insertion:

12th rib and T.P. of lumbar vertebrae

action:

- unilateral: laterally flexes vertebral column

- bilateral: depresses ribs during forced exhalation; stabilizes diaphragm during inhalation

Muscles of respiration

- external intercostals m.

- internal intercostals m.

- transversus thoracis m.

- diaphragm m.

external intercostals m. origin, insertion & action

origin:

inferior border of rib

insertion:

superior border of rib

action:

elevates ribs

internal intercostals m. origin, insertion & action

origin:

superior border of rib

insertion:

inferior border of superior rib

action: depresses ribs

external incrcostals vs. internal intercostals

They have different fiber directions

internal intercostals domino fall towards the midline.

external intercostals domino laterally.

Transversus thoracis m. origin, insertion & action

origin:

posterior surface of sternum

insertion:

cartilage of ribs 2-6

action:

minimal significance, depresses ribs

diaphragm m. origin [3], insertion [1] & action

origin:

xiphoid process, ribs 7-12 [associated costal cartilage], & anterior surface of lumbar vertebrae

insertion:

central tendinous sheet

action:

contraction expands thoracic cavity & compresses abdominopelvic cavity

All muscles of respiration

Key abdominal structures

- Rectus sheath

- Inguinal ligament

- Linea Alba ["white line"]

- Thoracolumbar fascia

Rectus sheath

aponeurotic extensions of 3 flat abdominal muscles

aponeurosis = flattened tendon

Thoracolumbar fascia

the deep membrane throughout the posterior thorax

Linea Alba ["white line"]

Fibrous structure that runs down the midline of the abdomen

Xiphoid process to pubic bone

Inguinal ligament

a ligament [fibrous band] extending from the pubic tubercle to the anterior superior iliac spine

- forming lower border of abdomen

Muscles of the abdominal wall

- rectus abdominis m.

- pyramidalis m.

- external oblique m.

- internal oblique m.

- transversus abdominus m.

Muscles of the abdominal wall collective function

- supports & protect abdominal organs

- contract to increase abdominal pressure

Muscles of the abdominal wall superior view

Rectus Abdominus m. origin [1], insertion [2], & action

origin:

pubis

insertion:

cartilage of ribs 5-7 & xiphoid process

action:

flexes vertebral column; acts to resist vertebral motion; forced exhalation

Pyramidalis m. origin , insertion, & action

- small triangular muscle anterior to the rectus and contained within the rectus sheath

- absent in ~20% of the population

origin:

pubic crest and symphysis

insertion linea alba

action: tenses linea alba

External oblique m. origin [1], insertion [2], & action

Origin:

ribs 5-12

Insertion:

linea alba and iliac crest

action:

depresses ribs; flexes and laterally rotates vertebral column to the opposite side

External oblique m. lateral view

clearly shows its extension from ribs 5-12 to insert into the linea alba and iliac crest

Internal oblique muscle origin[3], insertion [3], & action [2]

Origin:

thoracolumbar fascia; inguinal ligament; iliac crest

Insertion:

inferior surfaces of ribs 7-12 ; linea alba; pubis

Action:

depresses ribs; flexes and laterally rotates vertebral column to the same side

Transversus abdominis muscle origin [3], insertion [2], & action

Origin:

thoracolumbar fascia; iliac crest; ribs 7-12

Insertion:

Pubis & linea alba

action:

compresses abdomen; forced exhalation