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: 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.

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 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

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 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

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 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 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

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 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)

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

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 - 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 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

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 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.