Ch 10:Muscular System: Structure, Function, and Head, Neck, and Trunk Muscles

Muscle functions

Movement—move body parts; move body contents in breathing, circulation, and digestion; roles in communication (speech, writing, facial and nonverbal expressions)

Types of muscle tissue

Three kinds of muscle tissue: skeletal, cardiac, smooth

Muscular system

Refers only to the skeletal muscles (about 600 in human body)

Myology

The study of the muscular system

Endomysium

Thin sleeve of loose connective tissue around each fiber; allows room for capillaries and nerve fibers; provides chemical environment for muscle fiber and nerve ending

Perimysium

Thicker layer of connective tissue that wraps fascicles; carries nerves, blood vessels, and stretch receptors

Epimysium

Fibrous sheath surrounding entire muscle; blends with fascia and deeper connective tissues

Fascia

Sheet of connective tissue between muscles or muscle groups

Muscle fascicles

Bundles of muscle fibers wrapped together

Intrinsic muscles

Muscles that are contained within a specific region

Extrinsic muscles

Muscles that are located outside of a specific region but act upon it

Nerve and blood supply to skeletal muscles

Describes the general terms of how nerves and blood vessels supply skeletal muscles

Latin names of muscles

Aid in visualizing and remembering muscles

Muscle-bone attachments

Types of attachments that have shortcomings when referred to as origins and insertions.

Muscle compartmentalization

The organization of muscle groups and their connective tissue components.

Muscle stability

The ability of muscles to maintain posture and stabilize joints.

Thermogenesis

The process of heat production in the body, primarily by skeletal muscles.

Muscle control of body openings

Muscles regulate food intake, material movement, waste elimination, and light admission to the eye.

Fusiform muscles

Thick in the middle with fascicles converging on each tapered end.

Parallel muscles

Uniform width and parallel fascicles.

Triangular (convergent) muscles

Broad at one end with fascicles converging on the other, narrower end.

Pennate muscles

Feather-shaped; fascicles attach obliquely on a tendon that runs full length of muscle.

Unipennate

Fascicles approach tendon from one side.

Bipennate

Fascicles approach tendon from both sides.

Multipennate

Bunches of feathers converge to a single point.

Circular muscles (sphincters)

Fascicles form rings around body openings and passages, constricting the opening when contracted.

Fasciae

Package groups of functionally related muscles into muscle compartments.

Intermuscular septa

Extra thick fasciae between compartments.

Direct (fleshy) attachment to bone

Little separation between muscle and bone.

Indirect attachment to bone

Fibrous cord called a tendon connects muscle to bone.

Aponeurosis

Tendon that is a broad, flat sheet.

Retinaculum

Connective tissue band that tendons from separate muscles pass under.

Intrinsic muscle

Entirely contained within a region.

Extrinsic muscle

Acts on a designated region but arises from another region.

Prime mover

Muscle that produces most of the force of a movement; example: brachialis flexes elbow.

Synergist

Muscle that aids the prime mover; example: biceps brachii assists brachialis.

Antagonist

Muscle that opposes the prime mover; example: triceps brachii extends elbow.

Fixator

Muscle that prevents a bone from moving; example: rhomboid muscles fix scapula when biceps contracts.

Muscle action

Effect produced by a muscle to produce or prevent movement.

Muscle compartments

Contain nerves and blood vessels that supply the muscle group.

Innervation of a muscle

Refers to the identity of the nerve that stimulates it.

Muscle tests

Enable diagnosis of nerve, spinal cord, and brainstem injuries.

Spinal nerves

Arise from the spinal cord, emerge through intervertebral foramina, branch into posterior and anterior rami, and innervate muscles below the neck.

Cranial nerves

Arise from the base of the brain, emerge through skull foramina, and innervate the muscles of the head and neck.

Blood supply to muscular system

Receives about 1.24 L of blood per minute at rest.

Muscular system's blood share during heavy exercise

More than three-quarters (11.6 L/min) of total cardiac output.

Capillaries in muscles

Branch extensively through the endomysium to reach every muscle fiber.

Muscle naming

Latin-based and describes distinctive aspects of the structure, location, or action of a muscle.

Depressor labii inferioris

Muscle that lowers (depresses) the bottom (inferior) lip (labium).

Flexor digiti minimi brevis

Short (brevis) muscle that flexes (flexor) the smallest (minimi) finger (digit).

Learning the muscular system

Involves examining models, cadavers, dissected animals, or a photographic atlas.

Palpation of muscles

Involves feeling muscles on yourself if possible.

Attachments of muscles

Locate attachments on an articulated skeleton.

Derivation of muscle names

Usually describes the muscle's location, appearance, attachments, or action.

Muscle name pronunciation

Say the names aloud to yourself or study partner, and spell them correctly.

Facial expression muscles

Muscles that produce facial expressions.

Chewing and swallowing muscles

Muscles used for chewing and swallowing.

Neck muscles

Muscles that move the head.

Muscle attachments, action, and innervation

Identify the attachments, action, and innervation of these muscles.

Muscles of facial expression

Attach to the dermis and subcutaneous tissues, tense the skin and produce facial expressions, innervated by facial nerve (CN VII), found in scalp, forehead, around the eyes, nose, mouth, and in the neck.

Occipitofrontalis muscle

Has frontal belly and occipital belly connected by aponeurosis called galea aponeurotica.

Frontal belly

Elevates eyebrows and draws scalp forward.

Occipital belly

Retracts scalp.

Orbicularis oculi

Sphincter of the eyelid; encircles and closes the eye.

Levator palpebrae superioris

Opens the eye; deep to orbicularis oculi; elevates upper eyelid.

Orbicularis oris

Complex of muscles in lips encircling mouth; four interlacing muscle quadrants; puckers lips.

Modiolus

A complex cord just lateral to each angle of the lips where several muscles in lower face converge.

Mentalis muscles

Extend from upper margin of mandible to skin of chin; some people have mental cleft (dimple) between them; elevates and protrudes lower lip.

Buccinator

Muscle of the cheek; compresses cheek.

Platysma

Thin, superficial muscle of upper chest and lower face; involved in facial expression.

Muscles of the tongue

Functions include pushing food between molars for chewing (mastication), forcing food into the pharynx for swallowing (deglutition), and crucial importance to speech.

Intrinsic muscles of the tongue

Entirely within tongue; consist of vertical, transverse, and longitudinal fascicles.

Extrinsic muscles of the tongue

Arise from outside the tongue.

Muscles of chewing

Four pairs of muscles involved in chewing: Temporalis, Masseter, and two pairs of pterygoid muscles.

Actions of chewing

Include depression (to open mouth), elevation (for biting and grinding), protraction (so incisors can cut), retraction (to make rear teeth meet), and lateral and medial excursion (to grind food).

Suprahyoid muscles

Group of muscles superior to the hyoid bone that aid in chewing, swallowing, and speaking.

Digastric

A suprahyoid muscle that opens the mouth widely and contains two bellies.

Geniohyoid

A suprahyoid muscle that depresses the mandible.

Mylohyoid

A suprahyoid muscle that elevates the floor of the mouth at the beginning of swallowing.

Stylohyoid

A suprahyoid muscle that elevates the hyoid.

Infrahyoid muscles

Group of muscles inferior to the hyoid bone that fix the hyoid bone from below, allowing suprahyoid muscles to open the mouth.

Omohyoid

An infrahyoid muscle that depresses the hyoid after elevation and has two bellies.

Thyrohyoid

An infrahyoid muscle that depresses the hyoid and elevates the larynx.

Sternohyoid

An infrahyoid muscle that depresses the hyoid after elevation.

Sternothyroid

An infrahyoid muscle that depresses the larynx after elevation.

Pharyngeal constrictors

Three pairs of muscles that encircle the pharynx on its posterior and lateral sides, forming a muscular funnel that drives food into the esophagus during swallowing.

Flexion (head and neck)

Action of tipping the head forward.

Extension (head and neck)

Action of holding the head erect.

Lateral flexion (head and neck)

Action of tipping the head to one side.

Rotation (head and neck)

Action of turning the head to the left and right.

Contralateral movement

Movement toward the opposite side, depending on muscle attachments.

Ipsilateral movement

Movement toward the same side, depending on muscle attachments.

Sternocleidomastoid

Prime mover of neck flexion that extends from the upper chest (sternum, clavicle) to the mastoid process behind the ear.

Scalenes

Three muscles on each side of the neck that assist in neck flexion.

Trapezius

A large, superficial muscle that extends from the nuchal region over the shoulders and halfway down the back, extending and laterally flexing the neck.

Splenius capitis

Region of the splenius muscle in the head that causes ipsilateral flexion of the neck.

Splenius cervicis

Region of the splenius muscle in the neck that causes ipsilateral flexion of the neck.

Semispinalis capitis

Region of deep semispinalis muscle in the head that causes extension and contralateral rotation of the neck.

Semispinalis cervicis

Region of deep semispinalis muscle in the neck that causes extension and contralateral rotation of the neck.

Diaphragm

Muscular dome between thoracic and abdominal cavities; its fibers converge toward a central tendon.