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.
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