Rutgers University Functional Human Anatomy Lecture 18: Axial Musculature Overview

Axial Skeleton

- skull and associated bones

- thoracic cage

- vertebral column

axial musculature

-muscles that position the head and vertebral column

-muscles that move the rib cage

appendicular musculature

- muscles that stabilize or move the appendicular skeleton

muscles are innervated by

nerves

4 groups of axial muscles

- Muscles of the head and neck

- Muscles of the vertebral column

- Oblique and rectus muscles

- Muscles of the pelvic floor

muscles of head and neck

muscles of:

- facial expression

- extra-ocular

- mastication

- tongue

- pharynx

- anterior neck

obicularis oculi (facial expression)

- close eyes

- aids flow of tears

- facial nerve

obicularis oris (facial expression)

- mucus membrane at margin of the lips

- pucker lips

- innervated by facial nerve

• close mouth

Zygomaticus major and minor (facial expression)

- skin & muscles of upper lips (minor)

- angle of mouth (major)

- elevate mouth

- lateral pull of mouth

• SMILE

Buccinator (facial expression)

- pull mouth laterally & tightening cheeks

occipitofrontalis

- attach to cranial aponeurosis

Temporoparietalis

-fascia around external ear

-epicranial aponeurosis

platysma

- originate near clavicle region

medial/lateral rectus muscles (extra-ocular)

- draw gaze medial/laterally

- medial, nerve 3

- lateral, nerve 6

superior/inferior rectus (extra-ocular)

- draws gaze superior/inferior

- nerve 3

superior/inferior oblique (extra-ocular)

superior:

- draws gaze downward and laterally

- nerve 4

inferior:

- draws gaze upward and laterally

- nerve 3

muscles of mastication

- innervated by CN 5

masseter:

- originate on zygomatic arch

- insert in mandible

- pull mandible

• When contraction happens it will elevate mandible

temporalis:

- originate at temporal bone

- insert in coronoid process of mandible

- pull mandible

• Temporalis and masseter are elevating the mandible. This brings the biting surfaces of the teeth close to each other to allow the crushing of food.

pterygoid:

- elevate and laterally move mandible

mylohyoid muscle (Anterior muscles of neck)

- forms floor of mouth

- from mandible to hyoid bone

- innervated by CN5

Geniohyoid (Anterior muscles of neck)

- from mandible to hyoid bone

- draws hyoid forward/depress jaw

- CN 12

Stylohyoid (Anterior muscles of neck)

- from styloid process to hyoid bone

- lift hyoid for swallowing

- CN7

Sternocleidomastoid (Anterior muscles of neck)

- from sternum, clavicle to mastoid process

- lateral flexion of neck

- opposite side rotation

- CN 11

• Origin - sternum of the clavicle

• Insertion - mastoid process 

• When it contracts - laterally flex the neck to the ipsilateral side and turns the head to the contralateral side 

• Innervated by CN XI (11)

omohyoid (Anterior muscles of neck)

- depress hyoid bone

- CN1-3

Sternohyoid (Anterior muscles of neck)

- from sternum to hyoid

- depress larynx for sound

- CN1-3

thyrohyoid (anterior muscles of the neck)

- from thyroid to hyoid

- elevate thyroid, depress hroid

- CN 12

Muscles of the vertebral column

- extension of vertebral column

splenius capitis (Muscles of the vertebral column)

originate:

- lower cervical, upper thoracic spinous processes

insertion:

- mastoid process

- lateral occiput between superior/inferior nuchal line

- extend cervical spine (both side contraction)

- lateral flexion/ rotation (1-sided contraction)

Splenius Cervicis (Muscles of the vertebral column)

originate:

- upper thoracic vertebrae spinous processes

insertion:

- transverse processes of C1-C3

- extend cervical spine (both side contraction)

- lateral flexion/ rotation (1-sided contraction)

erector spinae (Muscles of the vertebral column)

- iliocostalis (lateral)

- longissimus

- spinalis (medial)

- extend spine

- same side rotation

- lateral flexion

- iliocostalis thoracis stabilizes throacic vertebrae in extension

- iliocostalis lumborum, extend vertebral column & depress ribs

- spinalis does no rotation

semispinalis group (Muscles of the vertebral column)

- capitits, cervicis, thoracis

- multifidus

- extension of vertebral column

- lateral flexion

- opposite side rotation

intervertebral muscles (Muscles of the vertebral column)

- rotatores

- intertransversarli

- interspinales (only performs extension)

- extension of vertebral column

- lateral flexion

- opposite side rotation

Quadratus Lumborum (Muscles of the vertebral column)

- from iliac crest & ilium lumbar ligament to last rib and lumbar vertebrae

- flexion of lower vertebral column

- depression of ribs

- lateral flexion

longus capitis/colli (spinous flexors)

- originate on transverse processes c4-c6, insert at base of occiput (capitis)

- originate at transverse process of cervical vertebrae (colli)

- flexion of cervical region

- same-side rotation

scalene (spinous flexors)

- from transverse vertebrae to ribs

- anterior, middle, posterior

- elevate ribs

- flex neck

- opposite side rotation (anterior)

- same side rotation (middles, posterior)

intercostal muscles (oblique & rectus muscles)

external:

- inferior border of rib to superior border of inferior rib

- expansion of rib cage (inhalation)

internal:

- superior border to inferior border of superior rib

- depress ribs (forced exhalation)

obliques (oblique & rectus muscles)

- compress abdomen

- depress ribs

- lateral flexion

external:

- from ribs 5-12 to aponeurosis and linea alba and iliac crest

- opposite side rotation

internal:

- from thoracolumbar fascia and inguinal ligament and iliac crest to ribs 8-12 and linea alba and pubis

- same-side rotation

transverse abdominis (oblique & rectus muscles)

- from ribs 7-12 on cartilage from iliac crest & thoracolumbar fascia

- to linea alba & pubis

- compress abdomen

rectus abdominis (oblique & rectus muscles)

- from pubis to cartilage of ribs 5-7 & xiyphoid process of sternum

- depress ribs

- flex vertebral column

- compress abdomen

Diaphragm

- major muscle for ventilation

- separates thoracic & abdominal cavity

- from xiyphoid process to ribs 7-12 & anterior surface of lumbar vertebrae and insert in central tendon sheath

- curved upward in relaxed position (umbrella) (exhale)

- flatten when contracted

- innervated by phrenic nerve (Cn3-5)

pelvic floor region (muscles of perineal region)

- urogenital & anal triangle

- separated by superficial transverse perineal muscle (stabilizer of central tendon of perineal region)

ischocavernosus (muscles of perineal region)

- contracts to compress & stiffen penis or clitoris

bulbospongiosus (muscles of perineal region)

- compress base of stiffen penis

- helps w/ ejection of urine/semen

- compress & stiffen clitoris

deep transverse perineal muscles (muscles of perineal region)

- muscles stabilizing central tendon

external urethral sphincter (muscles of perineal region)

male:

- compress urethra/prostate and bulb of urethral glands

female:

- closes urethra, compresses vagina & greater vestibular glands to lubrication

coccygeus (muscles of perineal region)

- flexion of coccygeal joint

- elevates pelvic floor

levator ani (muscles of perineal region)

pubo/illio coccygeus muscle:

- tenses pelvic floor

- supports pelvic organs

- elevates & retracts anus

external anal sphincter (muscles of perineal region)

- closes anal opening

Contraction/relaxations of diaphran and respiration 

• During inspiration (breathing in), the diaphragm contracts and it descends to allow for lung expansion.  

• During expiration (breathing out), the diaphragm relaxes and it ascends to allow for lung contraction.

• Weakness of the pelvic floor muscles can lead to urinary incontinence (urinary leakage).