Part I: Muscles of the Head and Neck

Part II: Muscles of the Trunk

Nestor T. Hilvano, M.D., M.P.H.(Illustrations Copyright by Frederic H. Martini, Pearson Publication

Inc., and The McGraw-Hill Companies Inc.)

Learning Objectives You should be able to:

1. Describe the various shapes of skeletal muscles and relate this to their functions.

2. Explain what is meant by the origin, insertion, belly, action, and innervation of a muscle.

3. Explain how muscles interact to produce or oppose movements.

4. Identify the major skeletal muscles of the head and neck, and indicate their origins, insertions, actions, and innervation.

5. Discuss common abnormalities and injuries of muscles of the head and neck.

6. Identify and describe the major skeletal muscles of the vertebral column (back).

7. Identify and describe the muscles of the thorax and the diaphragm.

8. Identify and describe the oblique and rectus muscles.

9. Identify and describe the muscles of the pelvic floor.

10. Correlate clinical conditions of the trunk using what you have learned in anatomy and physiology.

Part I: Introduction

• Muscles are named as to location, attachment, relative position, action, size, number, and shape.

• Shapes of skeletal muscle fibers: • Parallel - have parallel fascicles; stronger pull • Convergent - broad at origin and tapering to a narrower

insertion; less pull than parallel muscle• Pennate - fascicles insert obliquely on a tendon; produce

more tension (more muscle fibers) • Circular - ring around body opening

Descriptive Term for Muscle Size: • Longus = long

• Longissimus = longest

• Teres = long and round

• Brevis = short

• Magnus = large

• Major = larger

• Maximus = largest

• Minor = small

• Minimus = smallest

Parts of a Skeletal Muscle: 1. ___ - attachment to stationary end of muscle.2. ___ - thicker, middle region of muscle.3. ___ - attachment to mobile end of muscle. a. insertion b. origin c. belly

Muscle Actions• ___ - produces a particular movement,

prime mover; ex. biceps brachii.

• ___ - aids the prime mover, provide additional pull near the insertion or stabilizes the point of origin (fixators); ex. brachioradialis

• ___ - opposes the prime mover; preventing excessive movement and injury; ex. triceps brachii.

a. antagonist

b. agonist

c. synergist

Skeletal Muscle Innervation

• Cranial nerves arising from the brain– exit the skull through foramina– numbered I to XII

• Spinal nerves arising from the spinal cord– exit the vertebral column through

intervertebral foramina

Muscles of Facial Expression• Origin - surface of the skull• Insertion - superficial fascia and dermis• Innervation – VII C.N. • Action – Movements of facial structures• Paralysis causes face to sag = ________• Include the orbicularis oculi, buccinator,

orbicularis oris, mentalis, depressor labi inferioris, levator labi superioris, rizorius, zygomatic, frontalis, platysma

Figure 11-4b Muscles of Facial Expression

Frontal belly ofoccipitofrontalis

Corrugator supercilii

Temporalis (temporoparietalisremoved)

Orbicularis oculi

Nasalis

Zygomaticus minor

Zygomaticus majorOrbicularis oris

RisoriusPlatysma

Mentalis (cut)

Thyroid cartilageof the larynx

Epicranial aponeurosis

Temporoparietalis(cut and reflected)

Temporalis

Procerus

Levator labii superioris

Levator anguli oris

MasseterBuccinator

Depressor anguli orisDepressor labii inferiorisSternal head ofsternocleidomastoidClavicular head ofsternocleidomastoid

Trapezius

Clavicle

Platysma(cut andreflected)

Anterior viewProcerus- contraction will flare the nostrils

Muscles in Facial Expression• F_____ elevates eyebrow,

wrinkles forehead

• C_____ wrinkles eyebrow

• O_____ closes eyelids

• Z_____ elevates corner of mouth, upper lip (smile)

• R_____ draws corner of mouth to side (smile)

• B_____ compresses cheek, whistling muscle

• O_____ closes lips (purses lips)

• P _____ tightens neck, depresses mandible

• We blink every 2 to 10 seconds. Each blink lasts for 0.3 to 0.4 seconds.

Muscles of Mastication• Arise from skull and

insert on mandible• M_____ and T_____

elevate the mandible • M_____ and L_____

Pterygoids help elevate, but produce lateral excursion of jaw (side to side grinding)

• V CN innervation

B

Extrinsic Eye Muscles

• a. superior rectus b. inferior rectus c. Medial rectus

d. lateral rectus e. inferior oblique f. superior oblique

• Actions- eye movements; CN innervations- III, IV, & VI

___ look up; ___ look down

___ look medially; ___ look laterally

___ look down and laterally; ___ look up and laterally

Muscles of the Tongue• Shifts food onto teeth and pushes

it into pharynx; speech

• Intrinsic Muscle- shape

• Extrinsic Muscles- movement

Palatoglossus- elevate, XI CN

Styloglossus- elevate & retract

Hyoglossus- down & retract

Genioglossus- down & protract

Action: Elevate, retract, & protract tongue

• What is the strongest muscle?

XII CN

Muscles of the Pharynx• Action- Initiating the

swallowing process• Pharyngeal

constrictors

(superior, middle. inferior)

• Laryngeal elevators• Palatal muscles

(tensor veli palatini, levator veli palatini)

• What is dysphagia?

Anterior Muscles of Neck• Digastric and geniohyoid

depress the mandible or elevates larynx

• Mylohyoid provides muscular floor to the mouth

• Stylohyoid elevates larynx• Omohyoid and sternohyoid

depress hyoid bone and larynx

• Sternocleidomastoid – from clavicle and manubrium to mastoid - Action? __________

- Innervation= XI CN

Homework

1. Define key terms: origin, insertion, belly, agonist, synergist, antagonist, dysphagia, bell’s palsy, deglutition.

• Name the action/s of the following: masseter, temporalis, digastric, pterygoids, genioglossus, orbicularis oris, orbicularis oculi, platysma, corrugator supercili, rhizorius, zygomaticus, levator labi superioris, medial rectus, lateral rectus, frontalis, pharyngeal constrictors, and buccinator.

Part II: Muscles of the Trunk

Nestor T. Hilvano, M.D., M.P.H.

Superficial Muscles of Back• Trapezius – elevation and medial rotation, retraction (adduction), and depression of scapula

• Latissimus dorsi – adduction, extension, and medial rotation of humerus

B

A

Muscles of the Back• Erector spinae group

– 3 columns muscle– Iliocostalis, longissimus,

spinalis– Extends ________

• Semispinalis group– vertebrae to vertebrae

in neck– Extends _________

• Multifidis– vertebrae to vertebrae - rotates vertebral column

• Quadratus lumborum– ilium to 12th rib– lateral flexion of vertebral

column

Semispinalis

Erector spinae

Multifidis

Quadratus lumborum

Muscles of the Back• Intervertebral

muscles

- interspinalis

- intertransversalis

- rotatores• Action: slight

extension or

rotation

Diaphragm• Muscular sheet that forms a

wall between thoracic & abdominal cavities

• Muscle fascicles extend to a fibrous central tendon

• Function: major muscle of ____; contraction flattens it during ____; recoils (moves up) during ____.

a. inspiration

b. expiration

c. respiration

Muscles of Thorax• Scalene muscle

(anterior, middle, & posterior)

- action: elevate the first 2 ribs and assist in flexion of neck

• External intercostals

• Internal intercostals

• Transversus thoracis

Intercostals• External intercostals

– pull ribcage up and outward during inspiration

• Internal intercostals

- pull ribcage in and downward during forced expiration

• Transversus thoracis – as above (internal intercostals)

Muscles of the Abdomen• 4 Pairs of sheetlike

muscles– external oblique– internal oblique– transverse abdominis– rectus abdominis

• Functions– support the viscera– stabilize the vertebral

column (flexion of spine)– help in respiration (forced

expiration), urination, defecation and childbirth

Rectus Abdominis and External Oblique• External oblique –superficial,

downward, anteriorly; action: compresses abdomen • Rectus abdominis – vertical, straplike; action: compresses abdomen - fibrous compartment enclosing this muscle is ______. - a median collagenous partition is ______. - separated into segments by transverse lines/bands of collagen fibers named ______. a. linea alba b. tendinous inscriptions c. rectus sheet

Internal Oblique -Transverse Abdominis

• Internal oblique - anteriorly, upwards•Transverse abdominis - horizontal fiber • action – compresses abdomen

Muscles of the Pelvic Floor: Perineum

• The perineum is– diamond-shaped region bounded by pubic symphysis,

coccyx and ischial tuberosities– penetrated by anal canal, urethra and vagina

– anteriorly = urogenital triangle– posteriorly= anal triangle

• Functions - support organs of pelvic cavity- flex sacrum and coccyx- control movement of materials thru

urethra and anus

Superficial Muscles of Urogenital Triangle- support external genitalia

• Ischiocavernosus = arises ischial and pubic ramus• Bulbospongiosus = covers bulb of penis or encloses vagina• Function during intercourse and voiding of urine

Deep Muscles of UG Diaphragm -support pelvic floor and muscles of urethra

* Urogenital diaphragm = 2 muscles 1. deep transverse perineus m. - supports pelvic viscera 2. external urethral sphincter m.- inhibits urination

Muscles of Pelvic Diaphragm- support anal triangle

• Deepest compartment of the perineum • Pelvic diaphragm = 2 muscles - levator ani m. supports viscera and defecation - coccygeus m. supports and elevates pelvic floor

- Pubococcygeus- Iliococcygeus

Hernias• Protrusion of viscera through

muscular wall of abdominopelvic cavity

• Inguinal hernia– most common type of hernia in males– viscera enter inguinal canal or

even the scrotum

• Hiatal hernia– stomach protrudes through

diaphragm into thorax– overweight people over 40

• Umbilical hernia– viscera protrude through the

navel

Homework

1. Define key terms: linea alba, rectus sheath, tendinous transcriptions, hernia

2. Name the action/s of the following: trapezius, latissimus dorsi, diaphragm, levator ani, scalene, external intercostals, internal intercostals, erector spinae, external urethral sphincter, rectus abdominis, transversus thoracis, bulbospongiosus.

3. Compare and contrast inguinal hernia, hiatal hernia, and umbilical hernia.