Chapter 11 Muscles

Exam 1 will cover sections 11.1-11.4

Section 1 Fascicle Arrangement

Fascicles: bundles of muscle fibers in skeletal muscle fibers in each fascicle are parallel, but fascicle

arrangement can vary– parallel muscles- fascicles are parallel to long axis of muscle

(biceps brachii), when muscle fibers contract, muscle shortens by 30 %

– convergent muscles- fascicles extend over a broad area & meet (converge) at the attachment site, (pectoralis muscles)

– Pennate muscles- (feather) fascicles form a shared angle w/ tendoncontracted muscle doesn’t move tendon as far

as parallel muscles-fibers pull @ anglecontain more muscle fibers than parallel

muscle, so they produce more tension– Circular muscles- (sphincter) arranged around

openingswhen contracted, diameter decreases

11.2 Classes of Levers

Nature and site of muscle connection determine force, speed, and range of motion– lever (bone) moves when the applied force (AF) is

great enough to overcome the load (L) or resistance (R) that would prevent the movement

– in the body, each joint acts as a fulcrum, and muscles provide the applied force

– the load can vary (weight of limb, object held, or entire body)

– levers can change direction of applied force distance & speed of movement effective strength of applied force

Classes of levers– first class: fulcrum in the middle (teeter totter)– second class: load in the middle (wheel barrow), small

force can move a larger weight, at the expense of speed and distance

– third class: most common in body, force is between the load and the fulcrum, speed and distance traveled are increased at the expense of effective force (muscles must generate 6X the tension to support the load)

11.3 Muscle Origins & Insertions

Ends of skeletal muscle are attached to structures that limit their motion (bone, cartilage, connective tissue)

–origin-the place where fixed end of muscle attaches –insertion-the site where the moveable end attaches to another structure–action- movement produced when muscle contracts

Actions

Actions are described–by bone or region affected (flexion of forearm)–by joint involved (flexion of elbow)–based on functions

agonist (prime mover)- contraction responsible for producing specific movement, ex: biceps brachii muscle produces flexion of elbow antagonist- muscle whose action opposes the action of an agonist, ex: triceps brachii extends the elbow, going against the biceps brachii

synergist- helps a larger agonist work efficiently, may provide pull near insertion or may stabilize near origin; useful in start of motionfixator- a synergist that stabilizes origin of agonist by preventing movement at another joint

11.4 Descriptive terms

Locational terms–regional terms are common; abdominis- abdomen, capitis- head, femoris- femur, etc (PG 342)

Origin and Insertion–first part of name indicates the origin, second part, the insertion ex: sternocleidomastoid originates at sternum, inserts at the clavicle (cleido)

Fascicle organization–Rectus: straight, parallel muscles that run along long axis of body (rectus abdominis)–transverse/oblique: muscles have fibers that run at an angle to long axis of body (external obliques)

Position–externus/superficialis: visible at the body surface–internus/profundus:deeper muscles–Intrinsic: located within an organ

Structural Characteristics

number of tendons (biceps brachii, triceps brachii)shape- muscles named after their shape: trapezius, deltoid(triangle), rhomboid length and size:

– longus (long), longissimus (longest)–teres (long & round), brevis (short)–magnus (large), major (bigger), or maximus (biggest)–minor (small), or minimus (smallest)

Stop! Test 1 will cover 11.1-11.4

11.5 Muscles of facial expression

Orbicularis oculi– Sphincter muscle of eyelid– O: frontal & maxillary bones– I: tissue of eyelid– Action: closes eye– Nerve: facial / CN VII

(11.6)

Muscles of facial expression

Zygomaticus – O: zygomatic bone– I: corners of mouth– Action: smiling– Nerve: facial / CN VII

(11.6)

Major and Minor

Muscles of mastication

Masseter – O: zygomatic arch– I: angle & ramus of

mandible– Action: elevate mandible– Nerve: trigeminal nerve /

CN V (foramen ovale)

(11.7a)

Masseter

Muscles of mastication

Temporalis – O: temporal fossa– I: coronoid process of

mandible– Action: elevate and

retract mandible– Nerve: trigeminal n. /

CN V

(11.7a)

Extrinsic tongue muscles

Styloglossus – O: styloid process of

temporal bone– I: tongue– Action: retract & elevate

tongue– Nerve: hypoglossal n. /

CN XII

(11.7c)

Styloglossus

Extrinsic tongue muscles

Hyoglossus – O: hyoid bone– I: tongue– Action: depresses tongue– Nerve: hypoglossal n. /

CN XII

(11.7c)

Hyoid bone

Muscles of neck & throat

Digastric – two muscle bellies with an

intermediate tendon attached to the hyoid bone

– O: inferior margin of mandible (anterior belly); mastoid process of temporal bone (posterior belly)

– I: hyoid bone– Action: elevate hyoid, stabilize

hyoid, depress mandible– Nerve: trigeminal n. / CN V

(anterior belly), facial n. / CN VII (posterior belly)

(11.8a)Anterior belly Posterior belly

Muscles of neck & throat

Stylohyoid – O: styloid process of

temporal bone– I: hyoid bone– Action: elevate & retract

hyoid, swallow– Nerve: facial n. / CN VII

(11.7c)

Stylohyoid

Muscles of neck & throat

Sternohyoid – O: manubrium &

medial end of clavicle– I: hyoid bone– Action: depress hyoid

(11.8a)

Sternohyoid

Muscles of neck & throat

Pharyngeal constrictors – O: mandible, pterygoid

process, hyoid, laryngeal cartilages

– I: posterior medial raphe of pharynx

– Action: peristaltic contraction / swallow

(11.8b)

Superior

Middle

Inferior

Muscles of neck & throat

Sternocleidomastoid – O: manubrium & medial

clavicle– I: mastoid process of

temporal bone– Action: head & neck

flexion, rotate head contralaterally

– Nerve: accessory n. / CN XI

(11.8a)

Muscles of neck & throat

Sternocleidomastoid

Back muscles

Spinalis – O: spines of upper

lumbar and lower thoracic vertebrae

– I: spines of upper thoracic and cervical vertebrae

– Action: extends vertebral column

(11.9d)

Deep thorax muscles

External & internal intercostals – O&I: inferior & superior

border of ribs – Action: inspiration and

expiration

(11.10a)

Internal

Deep thorax muscles

Diaphragm – O: inferior internal

surface of rib cage & sternum, inferior costal cartilages, lumbar vertebrae

– I: central tendon– Action: flattens on

contraction (inspiration)– Nerve: phrenic nerves (11.10b)

Xiphoid process

Abdominal wall muscles

Rectus abdominis – O: pubic crest & symphysis– I: xiphoid process and

costal cartilages of ribs 5-7– Action: flex & rotate lumbar

vertebrae, fix & depress ribs, stabilize pelvis during walking, increase intraabdominal pressure

– Note: 3 tendinous insertions, aponeurosis & linea alba

(11.11ab)

Superficial thorax muscles

Pectoralis minor – O: anterior surface of

ribs 3-5– I: coracoid process of

scapula– Action: with ribs fixed,

pulls scapula anterior & inferior; with scapula fixed, pulls ribs superiorly

– Nerve: Medial and lateral pectoral nerves (C6-C8)

(11.13a)

Superficial thorax muscles

Superificial thorax muscles

Serratus anterior – O: ribs 1-8– I: vertebral border of

scapula– Action: hold scapula

against chest wall, moves inferior angle of scapula lateral & superior (abduction, pushing, punching)

– Nerve: long thoracic nerve (11.13a,8.1a reversed)

Superificial thorax muscles

Trapezius – O: occipital bone,

ligamentum nuchae, C7-T12 spinous processes

– I: acromion, spine of scapula, lateral third of clavicle

– Action: stabilize, elevate, adduct, depress scapula, extend head

– Nerve: Accessory (CNXI), C3 and C4 (11.13b)

Shoulder muscles

Pectoralis major – O: medial clavicle,

sternum, cartilage of ribs 1-6, aponeurosis of external oblique

– I: greater tubercle of humerus

– Action: arm-flexion, medial rotation, adduction, elevation of rib cage

(11.13a)

-Nerve: Medial and lateral pectoral nerves (C6-C8)

Shoulder muscles

Deltoid – O: lateral clavicle,

acromion & spine of scapula (compare to insertion of trapezius)

– I: deltoid tuberosity of humerus

– Action: arm-abduction, flexion, extension, medial & lateral rotation

– Nerve: Axillary nerve(C5-C-6)

(11.13ab)

Shoulder muscles

Subscapularis – O: subscapular fossa– I: lesser tubercle of

humerus– Action: medial rotate

arm, stabilize shoulder joint

– Nerve: Subscapular nerves (C5-C7)

(11.14d)

Shoulder muscles

Infraspinatus – O: infraspinous fossa– I: greater tubercle of

humerus– Action: lateral rotate

humerus, stabilized shoulder joint

– Nerve: Suprascapular nerve

(11.14b)

Rotator cuff muscles

Act to stabilize head of humerus in glenoid cavity and prevent dislocation

Supraspinatous (Suprascapular nerve) Infraspinatus (Suprascapular nerve) Subscapularis (Subscapular nerve) Teres minor (Axillary nerve)

Elbow muscles

Triceps brachii – O: long head-

infraglenoid tubercle, lat. & med. heads-posterior shaft of humerus

– I: olecranon process of ulna

– Action: extend forearm, assist adduction of arm

– Nerve: Radial nerve (11.14b)

Elbow muscles

Biceps brachii – O: short head-coracoid

process, long head-tubercle above glenoid cavity and lip of glenoid cavity (intertubercular groove)

– I: radial tuberosity– Action: flex elbow, supinate

forearm, weak arm flexor– Nerve: Musculocutaneous

nerve (C5 & C6)

(11.14c)

Forearm muscles

Flexor carpi (radialis & ulnaris) – O: medial epicondyle

of humerus, ulna– I: metacarpals and

carpals– Action: wrist flexion,

abduct & adduct hand– Carpal tunnel (Median

nerve) syndrome p. 184

(11.15a)Anterior view

radialis

ulnaris

Forearm muscles

Extensor carpi– O: lateral epicondyle of

humerus– I: base of metacarpals – Action: extend, abduct,

and adducts wrist– Palpate forearm muscles

Hip & knee muscles

Quadriceps femoris – O: anterior inferior iliac

spine, superior margin of acetabulum, greater trochanter, shaft of femur

– I: patella and tibial tuberosity via patellar tendon

– Action: extend knee, flex thigh

Hip & knee muscles

Gluteus muscles– O: ilium, sacrum, coccyx– I: shaft & greater

trochanter of femur– Action: extend thigh (climb

stairs, running), lateral & medial rotate thigh, abduct thigh, steadies pelvis

Hip & knee muscles

Hamstrings– O: ischial tuberosity, shaft

of femur– I: lateral & medial

condyles and shaft of tibia, head of fibula, lateral condyle femur

– Action: extend thigh, flex knee

– Makes touching toes hard

Leg muscles

Tibialis anterior – O: lateral condyle and

shaft of tibia– I: tarsal and first

metatarsal bones– Action: dorsiflexion

Leg muscles

Gastrocnemius – O: medial & lateral

condyles of femur– I: calcaneus via Achilles

tendon– Action: plantar flexion, flex

knee