Chapter 9: Muscle Anatomy (part 1)

Periosteum

A layer of connective tissue covering the outer surface of bone.

Tendon

Connective tissue that attaches muscles to bones.

Somatic motor neuron

A nerve cell that sends signals to skeletal muscles.

Muscle fiber

A single muscle cell.

Origin

The muscle attachment to the more stationary bone.

Insertion

The muscle attachment to the bone that moves more.

Muscle belly

The largest part of a muscle between its origin and insertion.

Aponeurosis

A broad, flat tendon that attaches muscles to other structures.

Epicranial aponeurosis

A broad tendon connecting the frontal and occipital bellies of the occipitofrontalis.

Thoracolumbar fascia

Connective tissue in the lower back that helps support the trunk.

Agonist

A muscle that contracts to produce a movement.

Antagonist

A muscle that works against the action of another muscle.

Pennate muscles

Muscles with many fibers arranged at an angle, allowing them to produce strong contractions.

Occipitofrontalis

A muscle that moves the scalp and eyebrows.

Frontalis

The front portion of the occipitofrontalis that raises the eyebrows.

Occipitalis

The back portion of the occipitofrontalis that moves the scalp.

Orbicularis oculi

The muscle that closes the eye.

Orbicularis oris

The muscle that moves the lips for actions such as puckering.

Buccinator

A cheek muscle that compresses the cheek and helps with chewing, sucking and whistling.

Corrugator supercilii

A muscle that draws the eyebrows together.

Zygomaticus major and minor

Muscles that pull the corners of the mouth upward.

Levator labii superioris

A muscle that raises the upper lip.

Mentalis

A chin muscle that helps move the lower lip and create a pouting expression.

Platysma

A superficial neck muscle that moves the corners of the mouth downward and tightens the neck skin.

Extrinsic eye muscles

Six skeletal muscles that move the eyeball.

Rectus eye muscles

Four eye muscles that run parallel to the long axis of the eyeball.

Oblique eye muscles

Two eye muscles that attach at an angle and help move the eyeball.

Masseter

The main chewing muscle that raises the mandible to close the mouth.

Temporalis

A muscle that retracts the mandible.

Pterygoid muscles

Medial and lateral muscles beneath the mandible that help move the jaw during chewing.

Mastication

The process of chewing food.

Intrinsic tongue muscles

Muscles located entirely within the tongue that change its shape.

Extrinsic tongue muscles

Muscles outside the tongue that attach to it and help move it.

Suprahyoid muscles

Four deep muscles that help with swallowing by elevating the hyoid and moving the larynx.

Digastric

A muscle that helps move the mandible and elevates the hyoid during swallowing.

Mylohyoid

A muscle that forms part of the floor of the oral cavity.

Stylohyoid

A muscle involved in elevating the hyoid during swallowing.

Omohyoid

A neck muscle that helps move and stabilize the hyoid bone.

Hyoid bone

A bone that supports tongue movement and helps anchor muscles involved in swallowing and speech.

Larynx

The voice box, whose position is controlled by neck muscles.

Sternocleidomastoid (SCM)

A neck muscle that bends the head sideways and rotates it.

Scalenes

Three deep neck muscles that elevate the first two ribs to assist breathing.

Trapezius

A muscle that elevates the shoulders, pulls the shoulder blades together and tilts the head backward.

Erector spinae

A muscle group that extends the vertebral column and helps maintain the lumbar curve.

External intercostals

Muscles between the ribs that elevate them during inhalation.

Internal intercostals

Muscles between the ribs that help depress them during expiration.

Transversus thoracis

A thoracic muscle that helps depress the ribs during expiration.

Diaphragm

The main muscle of normal breathing; it flattens during contraction to increase thoracic cavity volume.

Intercostal muscles

Muscles between the ribs that change the rib cage's dimensions during breathing.

Rectus abdominis

An abdominal muscle that flexes the vertebral column.

Linea alba

A line of connective tissue running down the center of the abdominal wall.

Rectus sheath

A connective tissue covering surrounding the rectus abdominis.

Tendinous intersections

Bands of connective tissue that divide the rectus abdominis into sections.

External abdominal oblique

An abdominal muscle that helps flex and rotate the trunk.

Internal abdominal oblique

An abdominal muscle that helps flex and rotate the trunk.

Transversus abdominis

An abdominal muscle that compresses the abdominal wall.

Pelvic diaphragm

A group of muscles that forms the pelvic floor and supports the pelvic organs.

Coccygeus

A pelvic floor muscle that helps support the pelvic organs.

Levator ani

A group of pelvic floor muscles that supports the pelvic organs.

Perineum

A diamond-shaped area below the pelvic diaphragm.

Urogenital triangle

The anterior half of the perineum.

Anal triangle

The posterior half of the perineum.