10. Axial Muscles Flashcards
How is muscle nomenclature descriptive?
Based on: bones they attach to, shapes, actions, size, direction of muscle fibers, and multiple origins/number of heads
Groups of muscles of the head
Muscles of facial expressions and muscles of mastication
Characteristics of muscles of facial expression
Over 40 muscles overall
Multiple layers originating on bone and inserting into skin or other muscles
OIA of Orbicularis oculi
Origin: margin of orbit
Insertion: skin surrounding eyelids
Action: closes eyes
OIA of orbicularis oris
Origin: maxilla and mandible
Insertion: skin surrounding mouth
Action: purses lips
OIA of buccinator
Origin: maxilla and mandible
Insertion: orbicularis oris
Action: compresses cheeks, holds food between them
OIA of platysma
Origin: skin of shoulder and chest
Insertion: skin of mandible and cheek
Action: tenses skin of neck
Characteristics and types of muscles of mastication
Move mandible to masticate food
4 muscles (temporalis, masseter, medial & lateral pterygoid muscles)
Buccinator muscle helps manipulate food in the oral cavity but is NOT a muscle of mastication
OIA of masseter
Origin: zygomatic arch
Insertion: lateral surface of mandibular ramus and angle
Action: elevates and protracts mandible
OIA of temporalis
Origin: temporal lines (lateral side of neurocranium)
Insertion: coronoid process of mandible
Action: elevates and retracts mandible
What is the saggital crest?
Origin of temporalis muscle the forms a bony crest
Larger attachment sit for stronger muscles
Not found in humans
Types of muscles of the neck and deep back
Sternocleidomastoid, infrahyoid muscles, suprahyoid muscles, and erector spinae consisting of spinalis, longissimus, and iliocostalis
Types of muscles of facial expression
Orbicularis oculi, orbicularis oris, buccinator, and platysma
OIA of sternocleidomastoid
Origin: manubrium and clavicle
Insertion: mastoid process of temporal bone
Action:
unilaterally: ipsilaterally side bends the neck and contralaterally rotates the head
bilaterally: flexes neck
Bilateral vs unilateral contraction
Bilateral- muscles on both sides contract
Unilateral- muscle on one side contracts
Ipsilateral vs contralateral movement
Ipsilateral- move toward same side
Contralateral- move toward opposite side
Clinical diagnosis of a shortening, spasm, or fibrosis of the sternocleidomastoid that can be congenital or acquired
Torticollis
What is reflected by the action of the sternocleidomastoid
Position of the head
OIA of infrahyoid muscles
Origin: sternum, scapula
Insertion: hyoid bone
Action: depresses or stabilizes the hyoid
OIA of suprahyoid muscles
Origin: mastoid & styloid processes, hyoid
Insertion: mandible
Action: depresses the mandible or elevates the hyoid
How do the infrahyoid and suprahyoid muscles work together
Infrahyoid muscles stabilize the hyoid bone while suprahyoid muscles can only depress the mandible
Movements of the spine
Flexion, extension, side bending, rotation
Muscles of the erector spinal
Spinalis, longissimus, and iliocostalis
OIA of erector spinae
Origin: spinous processes, sacrum, and ilium
Insertion: vertebrae and ribs
Action: Extends the spine (maintain posture)
Muscles of the abdominal wall and their overall action
Rectus abdominis, external oblique, and internal oblique
Action: flexes and rotates the trunk and compressed abdomen
OIA of rectus abdominis
Origin: pubic bone
Insertion: xiphoid process and inferior ribs
Action: flex trunk; compress abdomen
Covered by rectus sheath
OIA and characteristics of external oblique
Origin: inferior ribs
Insertion: linea alba
Action: flex and rotate trunk, compress abdomen
Fibers directed “down and in” or “hands in pockets”
Most superficial muscle layer
OIA and characteristics of internal oblique
Origin: iliac crest
Insertion: linea alba
Action: flex and rotate trunk, compress abdomen
Fibers directed “up and in”
Second muscle layer
Muscles of breathing
Respiratory diaphragm and intercostal muscles
How does breathing occur
Breathing occurs when the thorax increases or decreases its volume
Lungs sit in a vacuum where expanding the chest inhales and compressing the chest exhales
Lungs are manipulated by muscles acting in the ribs
Different muscles work for breathing at rest vs forced breathing
OIA of respiratory diaphragm
Origin: internal surface of ribs, xiphoid process, lumbar vertebrae
Insertion: central tendon
Action: diaphragm flattens for inhalation
Active for breathing at rest and forced breathing
OIA of intercostal muscles
Origin: ribs
Insertion: adjacent rib
Action: assists with respiration
Active during forced inhalation and exhalation
