1. 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.)

2. Learning Objectives You should be able to:
Describe the various shapes of skeletal muscles and relate this to their functions.
Explain what is meant by the origin, insertion, belly, action, and innervation of a muscle.
Explain how muscles interact to produce or oppose movements.
Identify the major skeletal muscles of the head and neck, and indicate their origins, insertions, actions, and innervation.
Discuss common abnormalities and injuries of muscles of the head and neck.
Identify and describe the major skeletal muscles of the vertebral column (back).
Identify and describe the muscles of the thorax and the diaphragm.
Identify and describe the oblique and rectus muscles.
Identify and describe the muscles of the pelvic floor.
Correlate clinical conditions of the trunk using what you have learned in anatomy and physiology.

3. 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

4. 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

5. 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

6. 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

7. 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

8. Figure 11-4b Muscles of Facial Expression
Epicranial aponeurosis
Frontal belly of
occipitofrontalis
Temporoparietalis
(cut and reflected)
Corrugator supercilii
Temporalis
Temporalis (temporoparietalis
removed)
Orbicularis oculi
Procerus
Nasalis
Levator labii superioris
Zygomaticus minor
Levator anguli oris
Zygomaticus major
Orbicularis oris
Masseter
Risorius
Buccinator
Platysma
Depressor anguli oris
Depressor labii inferioris
Mentalis (cut)
Sternal head of
sternocleidomastoid
Thyroid cartilage
of the larynx
Clavicular head of
sternocleidomastoid
Trapezius
Clavicle
Platysma
(cut and
reflected)
Procerus- contraction will flare the nostrils
Anterior view

9. 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.

10. 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

11. 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

12. Muscles of the Tongue Styloglossus- elevate & retract
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

13. 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?

14. 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

15. Homework
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.

16. Part II: Muscles of the Trunk
Nestor T. Hilvano, M.D., M.P.H.

17. 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

18. Muscles of the Back Erector spinae group Semispinalis group Multifidis
3 columns muscle
Iliocostalis, longissimus, spinalis
Extends ________
Semispinalis group
vertebrae to vertebrae
in neck
Extends _________
Multifidis
- rotates vertebral column
Quadratus lumborum
ilium to 12th rib
lateral flexion of vertebral column
Semispinalis
Erector spinae
Multifidis
Quadratus lumborum

19. Muscles of the Back Intervertebral muscles - interspinalis
- intertransversalis
- rotatores
Action: slight
extension or
rotation

20. 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

21. 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

22. Intercostals External intercostals Internal intercostals
pull ribcage up and outward during inspiration
Internal intercostals
- pull ribcage in and downward during forced expiration
Transversus thoracis – as above (internal intercostals)

23. Muscles of the Abdomen 4 Pairs of sheetlike muscles Functions
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

24. 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

25. Internal Oblique -Transverse Abdominis
- anteriorly, upwards
Transverse abdominis
- horizontal fiber
action – compresses
abdomen

26. 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

27. 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

28. 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

29. Muscles of Pelvic Diaphragm- support anal triangle
Pubococcygeus
Iliococcygeus
Deepest compartment of the perineum
Pelvic diaphragm = 2 muscles
- levator ani m. supports viscera and defecation
- coccygeus m. supports and elevates pelvic floor

30. 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

31. Homework
Define key terms: linea alba, rectus sheath, tendinous transcriptions, hernia
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.
Compare and contrast inguinal hernia, hiatal hernia, and umbilical hernia.