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/ 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

▫Circular muscles- (sphincter) arranged around openings when 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)

Section 11.6 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 neck*reaches the base of the skull *inserts on the clavicles and spines of the scapulae *regions can contract independently so the action varies*superficial

Superificial thorax muscles

•Trapezius ▫I: spine of scapula,

clavicle▫Action: stabilize,

elevate, adduct, depress scapula, extend head

(11.13b)

B. Rhomobid*adducts (retracts) scapula* attaches to cervical and thoracic vertebrae*inserts at the scapula*deep

C. Levator scapulae*elevates scapula* deep

Superficial thorax muscles

D. Serratus anterior- on the chest*fan shaped*originates on chest side of ribs*inserts on the scapula*protracts scapula, swings shoulder forward (pushing)*superficial

E. Subclavius*deep chest muscle* originates on rib 1*inserts on inferior border of clavicle* depresses & protracts clavicle & shoulder

F. Pectoralis Minor* originates on ribs 3-5*inserts on coracoid process of scapulae*complements contraction of subclavius, downward rotation of shoulder

Superficial thorax muscles• Pectoralis minor

▫O: anterior surface of ribs 3-5

▫I: coracoid process of scapula

▫Action: pulls scapula anterior & inferior

(11.13a)

B. Muscles that move the arm1. deltoid*originates on clavicle & scapulae*inserts on humerus*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

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