Muscular System: Muscles of the Body - I

Flashcards covering the muscles of the head, neck, and trunk based on the lecture notes.

Muscle Actions and Interactions

A muscle cannot reverse the movement it produces; another muscle must undo the action, and muscles with opposite actions lie on opposite sides of a joint.

Muscles of Facial Expression

Thin and variable in shape muscles that lie in the face and scalp, often inserting into the skin and innervated by CN VII, the facial nerve.

Epicranius (Occipitofrontalis)

A bipartite muscle consisting of frontal and occipital bellies connected by the epicranial aponeurosis; the frontal belly raises eyebrows and wrinkles the forehead horizontally.

Corrugator supercilii

The 'angry eyebrows' muscle that draws eyebrows medially and inferiorly and wrinkles the forehead skin vertically.

Orbicularis oculi

A thin, flat sphincter muscle of the eyelid that closes the eye and is used for blinking and squinting.

Zygomaticus major

The 'smiling muscle' that extends diagonally from the cheekbone to the corner of the mouth and raises the lateral corners of the mouth.

Orbicularis oris

The 'kissing and whistling' muscle that closes, purses, and protrudes the lips with fibers running circularly around the mouth.

Buccinator

Latin for 'trumpeter', this horizontal cheek muscle compresses the check as in whistling and sucking and holds food between the teeth during chewing.

Mentalis

The 'pouty lip' muscle that forms a V-shaped mass on the chin, wrinkles the chin, and protrudes the lower lip.

Platysma

An unpaired, thin, sheetlike superficial neck muscle that tenses the skin of the neck and helps depress the mandible.

Depressor anguli oris

The 'frown' muscle that draws the corners of the mouth inferiorly and laterally.

Masseter and Temporalis

The prime movers of jaw closure used in mastication.

Pterygoid muscles

Muscles responsible for side-to-side movement and grinding during chewing.

Genioglossus

A fan-shaped extrinsic tongue muscle that protracts the tongue and prevents it from falling backward to obstruct respiration; innervated by the hypoglossal nerve (cranial XII).

Styloglossus

A slender extrinsic muscle that retracts and elevates the tongue; innervated by the hypoglossal nerve.

Hyoglossus

A flat, quadrilateral extrinsic muscle that depresses the tongue; innervated by the hypoglossal nerve.

Suprahyoid muscles

A group of muscles that participates in swallowing by elevating the hyoid bone and lifting the larynx superiorly and anteriorly.

Infrahyoid muscles

A group of muscles that participates in swallowing by depressing the larynx and hyoid bone.

Pharyngeal constrictors

Muscles that squeeze food into the esophagus.

Sternocleidomastoid

A key muscular landmark of the neck that flexes the head, laterally flexes the neck, and rotates the head; it inserts on the mastoid process.

Trapezius

A superficial muscle of the posterior neck and back that stabilizes the pectoral girdle and elevates, depresses, retracts, and rotates the scapula.

Splenius muscles

Muscles (capitis and cervicis) that extend, rotate, and laterally flex the head and neck.

Rhomboid muscles (major and minor)

Parallel bands that retract, elevate, and rotate the scapula while stabilizing it against the thoracic wall.

Latissimus dorsi

A muscle that extends, adducts, and medially rotates the humerus, drawing the arm inferiorly and posteriorly.

Erector spinae group

The main extensor of the vertebrae consisting of the Iliocostalis, Longissimus, and Spinalis; it maintains normal curvatures of the spine.

Pectoralis major

A muscle of the thorax that adducts and medially rotates the humerus and can flex or extend the humerus depending on the head used.

Serratus anterior

A powerful protractor of the scapula originating from the lateral surfaces of ribs 1-8.

External intercostal muscles

11 pairs of muscles that elevate the rib cage and are most active during inspiration.

Internal intercostal muscles

11 pairs of muscles deep to the external intercostals that depress the rib cage and aid in expiration during heavy breathing.

Rectus abdominis

Commonly known as the 'six-pack', this muscle flexes the trunk and compresses abdominal viscera; it is divided by tendinous inscriptions.

Linea alba

A fibrous band of connective tissue that runs down the midline of the abdomen.

Rectus sheath

A fibrous compartment formed by the aponeuroses of the internal and external obliques and the transversus abdominis.