Chapter 11 Muscles

I. Fascicle arrangement

A. Fascicles: bundles of muscle fibers in skeletal muscle 1. fibers in each fascicle are parallel, but fascicle arrangement can vary

a. parallel muscles- fascicles are parallel to long axis of muscle, when muscle fibers contract, muscle shortens by 30 % (biceps)

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

c. Pennate muscles- (feather) fascicles form a shared angle w/ tendon

contracted muscle doesn’t move tendon as far as parallel muscles-fibers pull @ angle

contain more muscle fibers than parallel muscle, so they produce more tension

d. Circular muscles- (sphincter) arranged around openings

when contracted, diameter decreases

B. Classes of Levers1. Nature and site of muscle connection determine force, speed, and range of motion

a. lever (bone) moves when the applied force (AF) is great enough to overcome the load (L) or resistance (R) that would prevent the movementb. joint acts as a fulcrum, and muscles provide the applied forcec. load can vary (weight of limb, object held, or entire body)

d. levers can change the following: direction of applied force distance & speed of movement effective strength of applied force

2. Classes of leversa. first class: fulcrum in the middle (teeter totter)b. second class: load in the middle (wheel barrow), small force can move a large weight, at the expense of speed and distance

c. 3rd 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)

C. Muscle Origins & Insertions1. Ends of muscle are attached to structures that limit their motion (bone, cartilage, connective tissue)

a. origin-the place where fixed end of muscle attaches b. insertion-the site where the moveable end attaches to another structurec. action- movement produced when muscle

contracts

2. Actions are describeda. by bone or region affected (flexion of forearm)b. by joint involved (flexion of elbow)c. 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 motion

fixator- a synergist that stabilizes origin of agonist by preventing movement at another joint

D. Naming muscles- descriptive 1. Locational terms

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

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

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

4. Positiona. externus/superficialis: visible at the body surfaceb. internus/profundus:deeper musclesc. Intrinsic: located within an organ

E. Naming muscles-Structural Characteristics

1. number of tendons (biceps brachii, triceps brachii)2. shape- muscles named after their shape: trapezius, deltoid(triangle), rhomboid 2. length and size:

a. longus (long), longissimus (longest)b. teres (long & round), brevis (short)c. magnus (large), major (bigger), or maximus (biggest)d. minor (small), or minimus (smallest)

II. Individual MusclesA. Muscles of facial expression

1. Orbicularis oculi▫Sphincter muscle of eyelid▫O: frontal & maxillary bones▫I: tissue of eyelid▫Action: closes eye▫Nerve: facial

(11.6)

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

(11.6)

Major and Minor

B. Muscles of mastication1.Masseter

▫O: zygomatic arch▫I: angle & ramus of

mandible▫Action: elevate

mandible▫Nerve: trigeminal

nerve / CN V

(11.7a)Masseter

2. Temporalis ▫O: temporal fossa▫I: coronoid process

of mandible▫Action: elevate and

retract mandible▫Nerve: trigeminal

n. / CN V

(11.7a)

C. Extrinsic tongue muscles1. Styloglossus

▫O: styloid process of temporal bone

▫I: tongue▫Action: retract &

elevate tongue▫Nerve: hypoglossal n.

/ CN XII

(11.7c)Styloglossus

2. Hyoglossus ▫O: hyoid bone▫I: tongue▫Action: depresses

tongue▫Nerve: hypoglossal n.

/ CN XII

(11.7c)

Hyoid bone

D. Muscles of neck & throat1. 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. (anterior

belly), facial n. (posterior belly)

(11.8a)Anterior belly Posterior belly

2. Stylohyoid ▫O: styloid process of

temporal bone▫I: hyoid bone▫Action: elevate &

retract hyoid, swallow

▫Nerve: facial n. / CN VII

(11.7c)

Stylohyoid

3. Sternohyoid ▫O: manubrium &

medial end of clavicle

▫I: hyoid bone▫Action: depress

hyoid

(11.8a)

Sternohyoid

4. Pharyngeal constrictors

▫O: mandible, pterygoid process, hyoid, laryngeal cartilages

▫I: posterior medial raphe of pharynx

▫Action: peristaltic contraction / swallow

(11.8b)

Superior

Middle

Inferior

5. 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

E. Muscles of the Back1. Errector spinae (extensor) muscles- include superficial & deep layers

a. superficial layer: spinalis, longissimus, and iliocostalis groups

-when contracting together, extend the spine, when contracting on one side, laterally flex the spine

i. Spinalis group ▫O: spines of upper

lumbar and lower thoracic vertebrae

▫I: spines of upper thoracic and cervical vertebrae

▫Action: extends vertebral column

ii. Longissumus groupO: tranverse processes of vertebraeI: tranverse processes of vertebrae

above originA: extends neck and vertebral column,

lateral flexion of spine or neck

iii. Iliocostalis groupO: superior borders of ribs, iliac crest,

sacral crestI: transverse processes of cervical

vertebrae,inferior surfaces of ribsA: extends neck, elevates ribs,

stabilizes thoracic vertebrae, extends vertebral column

b. Deep layer of back musclesi. semispinalis group (multifudus,

interspinales, intertransversarii, and rotatores)

- smaller muscles, interconnect and stabilize the vertebrae

-produce slight rotations, and adjust positions of individual vertebrae

c. Flexor muscles of the back –most muscles on the back are extensors due to the large trunk muscles that flex the vertebral column but there are a few flexorsi. longus capitis & longus colli-rotate or flex the neckii. Quadratus lumborum- large trunk flexors on l &r side of vertebral columnO: iliac crestI: last rib, trans. Process of lumbar vertebraeA. together, depress the ribs, alone, laterally flexes vertebral column

F. Deep thorax muscles1. External & internal intercostals

▫O & I: inferior & superior border of ribs

▫Action: inspiration and expiration

(11.10a)

Internal

2.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

G. Abdominal wall muscles1. Rectus abdominis

▫O: near pubic symphysis▫I: xiphoid process ▫Action: flex & rotate

lumbar vertebrae, fix & depress ribs, stabilize pelvis during walking, increase intra-abdominal pressure

* 3 tendinous insertions, aponeurosis & linea alba

(11.11ab)

2. Other muscles to know:a. Internal and external Obliquesb. Transversus abdominis

Look at diagram a onPg 355

(11.11ab)

Part 2:Appendicular Muscles

•Position & stabilize pectoral & pelvic girdles

•Move upper & lower limbs

•Split into 2 major groups:

▫Muscles of shoulder & upper limb

▫Muscles of pelvis & lower limb

•Differences in function:

▫Pectoral girdle has muscular connections with axial skeleton, acts as a shock absorber Example: can use hands when you run

▫Pelvic girdle transfers weight from axial muscles to appendicular skeleton, needs more bony support

I. Shoulder & Upper LimbA. Muscles that position the pectoral girdle

1.Trapezius- covers back & parts of the neckreaches the base of the skull O: Occipital bone, ligamentum nuche & spinous processes of vertebrae I: spine of scapula, clavicleA: stabilize, elevate, retract, adduct, depress scapula, extend neck (lift head)

-regions can contract independently so the action varies-superficial muscle (close to surface of body)

(11.13b)

2. RhomboidO: attaches to cervical and thoracic vertebraeI: inserts at the vertebral border of the scapulaA: adducts (retracts) scapula, downward rotation- is a deep muscle, under trapezius, and is split into major and minor

3. Levator scapulaeO: transverse process of c1-4I: vertebral border of each scapulaA: elevates scapula-is also a deep muscle

4. Serratus anterior- on the chest, fan shaped O: on anterior side of ribsI: anterior margin of vertebral border of the scapulaA: protracts scapula, swings shoulder forward -superficial

5. SubclaviusO: 1st rib I: inferior border of clavicleA: depresses & protracts clavicle & shoulder

6. Pectoralis MinorO: anterior surface of ribs 3-5I: coracoid process of scapulaeA: complements action of subclavius, also produces downward rotation of shoulder

B. Muscles that move the arm1. deltoidO:on clavicle & scapulaeI: humerusA: major abductor of arm (away from body)2. supraspinatus* superior to posterior portion of deltoid (under trapezius)*helps w/start of abduction movement

3. Subscapularis*located on anterior side of scapula* rotates arm medially

4. Teres major*helps rotate arm medially

5. Infraspinatus*located on the posterior side

of the scapula, deep to deltoid*located below the

scapular spine* rotates arm laterally

(away from body)

6. Teres minor*aides in lateral rotation

7. Rotator cuff muscles•Act to stabilize head of humerus in

glenoid cavity and prevent dislocation, can be a frequent site of sports injuiries

•Supraspinatus•Infraspinatus •Teres minor•Subscapularis

Remember SITS

8.Coracobrachialis* small muscle* only muscle attached to scapula that flexes & adducts humerus

9. Pectoralis major* originates on ribs 2-6 cartilage,body of sternum, and inferior portion of clavicle* inserts on greater tubercle of humerus* flexes, adducts, and medially rotates humerus

10. Latisumus dorsi*extends between the thoracic vertebrae & lesser tubercle of humerus* extends arm

C. Muscles that move the forearm & hand(move the elbow & wrist)

•Most muscles that insert on the forearm originate on the humerus▫2 exceptions: biceps brachii & long

head of triceps brachii1. Biceps brachii

* on anterior side of body* short & long head* originate on scapula, insert on

radius* flexes & supinates arm (bends

elbow)

2. Triceps brachii*lateral, long, & median heads, all

insert on olecranon process of ulna* located on posterior side of humerus* extends forearm (straightens elbow)

3. Brachialis* deep muscle, located on anterior

side of elbow* flexes the elbow*originates on humerus, inserts on

ulna

4. Brachioradialis* superficial, located along anterior

thumb side of forearm* originates on humerus, inserts on

radius* flexes elbow

5. Anconeus* extends elbow (assists triceps)* located on posterior side of elbow

6. Flexor carpi radialis Flexor carpi ulnaris Palmaris longus

* all contribute to flexion at wrist

* anterior side* radials abducts*ulnaris adducts

(11.15a)Anterior view

radialisulnaris

7. Extensor carpi radialis Extensor carpi ulnaris

*extends wrist*on posterior side* radials abducts* ulnaris adducts

D. Muscles that move the hand and fingers1. Muscles of forearm end before reaching the wrist, only tendons cross to ensure mobilitya. Tendons of wrist pass through synovial tendon sheaths to reduce friction2. Fine control of hand involves small intrinsic muscles that originate on the carpal & metacarpalsa. only tendons extend across distal joints of fingersb. extensor & flexor retinaculum-bands of connective tissue that hold tendons in place

Video 4II. Muscles of the Pelvis & lower limb A. muscles that move the thigh 1. gluteus maximus *largest, most posterior, superficial*originates at sacrum & coccyx *shares insertion w/ tensor fasciae latae muscle, both insert on iliotibial tract - band of collagen fibers extending from thigh to tibia, acts as brace *produces extension & lateral rotation of hip

2. Gluteus medius gluteus minimus

*deep to maximus*medius originates on crest of illium*minimus originates below crest of

illium* both insert on greater trochanter of

femur* adbuct and medially rotate hip

3. Lateral rotators* deep posterior muscles* 6 muscles in all, piriformis &

obturator are dominant* all aid in lateral rotation at hip

4. Adductors*all originate on ramus of pubis*most insert on femur*include adductor magnus, longus, brevis, pectineus & gracilis* most perform hip flexion & adduction (use these when riding horse)* pulled groin refers to tear in one of these muscles

5. Iliopsoas muscle* made of psoas major & iliacus

muscle*locate on anterior interior side of

pelvis* Are powerful hip flexor muscles

B. Muscles that bend the knee*Extensors (straighten knee)-on anterior & lateral surface of thigh*Flexors (bend knee)- on posterior & medial surface of thigh* Connective tissue divides muscles into compartments

Flexors of the knee (located on posterior thigh) 1. Hamstrings: (from lateral to medial)*biceps femoris*semitendinous*semimembranous-originate on edges of pelvis-insert on tibia and fibula2. sartorius* cross front of thigh from lateral to medial side* originates on anterior iliac*inserts at medial surface tibia* flexes knee & laterally rotates hip (cross legs)

3. Popliteus* muscle on back of knee* flexes knee to “unlock”

Extensors of the knee (on anterior side of thigh)4. Quadriceps femoris (“quads”)

*vastus muscles (three)*rectus femoris (1)

-originate at shaft of femur-insert at patella-extend/straighten knee

C. Muscles that move the ankle and toes

-Most of the muscles that move the ankle produce ankle extension- This extension is involved in

walking and running movements1. Gastrocnemius*posterior side, calf muscle*important extensor*2 heads, originate on epicondyles of femur*inserts on calcaneus via calcaneal tendon

2. Soleus*deep to gastrocnemius*Slow fibers better suited for postural adjustments*produces extension*inserts via calcaneal tendon (“Achilles”)

3. Fibularis longus & fibularis brevis (peroneus)*Produce extension of ankle & eversion*Seen on lateral side of leg

4. Tibialis anterior*large flexor, located on anterior side*opposes gastrocnemeus

5. Extensor digitorum longus & extensor hallicus longus*Digital muscles, tendons cross ankle, not muscles*tendon sheaths are stablized by extensor retinacula