Muscles of the Body

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http://www.rad.washington.edu/academics/academic-sections/msk/muscle-atlas

"Copyright 2003-2004 University of Washington. All rights reserved including all photographs and images. No re-use, re-distribution or commercial use without prior written permission of the authors and the University of Washington." "Musculoskeletal Images are from the University of Washington "Musculoskeletal Atlas: A Musculoskeletal Atlas of the Human Body" by Carol Teitz, M.D. and Dan Graney, Ph.D."

Other copies materials from Marieb, 5th ed., Martini, 6th ed. or online with reference

Fascicles

Bundles of fibers

*

Skeletal muscle

Epimysium: surrounds whole muscle

Perimysium is around fascicle

Endomysium is around each muscle fiber

Different arrangements

of fascicles

Arrangement of fascicles influences movement and power

Skeletal muscles can shorten by about 1/3 of their resting length The more nearly parallel to the axis, the more

they can shorten This results in a larger distance of movement

The power depends on the total number of fibers Stocky muscles (like bipennate vs parallel)

have more fibers, therefore more powerful even though shorten very little

Interactions of Skeletal Muscles

Muscles can only pull, they can’t push Actions must be “undone” by a different

muscle Muscles that produce opposite movements

usually lie on opposite sides of a given joint

Interactions, continued

Agonist: prime mover, major responsibility for producing a specific movement

Antagonist: oppose or reverse a particular movement Usually contract a little to prevent overshooting the

mark or slow the agonist’s action near the end Are being stretched or can remain relaxed when

agonist works Antagonists for one movement can be agonists

for another

Synergists help prime movers Add a little extra force to the same movement

Or reduce undesirable extra movements (e.g.

making a fist without flexing at wrist)

Fixators: hold a bone firmly so agonist has a stable base on which to move a body part (e.g. fixing scapula when arm moves)

Compartments Contain muscles of similar developmental origin and function

Dense fibrous connective tissue separates

Upper limb: 2 compartments Lower limb: 3 compartments

Naming skeletal muscles (examples)

Location: brachialis is in arm (brachium = arm) Shape: deltoid is triangular (delta = triangle) Size: minimus (smallest), longus (long), brevis

(short) Direction of fascicles and fibers: rectus (straight);

transversus (right angle) and oblique (oblique) to midline

Number of origins: biceps (“two heads”), triceps (“three heads”), quadriceps (“four heads”)

Action: “flexor,” “extensor,” “adductor” or “abductor” appear in the name

Combinations of the above, e.g. extensor carpi radialis longus

Axial muscles Lie anterior and posterior to body axis

(vertebral column) Move trunk; maintain posture Skeletal muscles of thorax, abdomen, and

pelvis Many muscles of neck A few muscles in head

Limb muscles

Arise from ventral region as limb buds Muscles develop from lateral parts of myotomes In general: dorsal (posterior) muscles become

extensors and ventral (anterior) become flexors Lower limb rotates during embryonic

development: Extensors on anterior (ventral) side: extend leg at

knee, dorsiflex foot at ankle and extend toes Flexors on posterior (dorsal) side: flex leg at knee,

plantarflex foot at ankle, flex toes

anterior

Text Text

to use for studying...

posterior

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Muscles of the Head and Neck Scalp Muscle: epicranius frontal belly occipital belly gala aponeurotica

Muscles of Facial Expression: insert on skin or another muscle Muscles of Mastication (chewing): all have

insertions on the mandible Anterior Neck Muscles Posterior Neck Muscles

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“glossus” = tongue

Mastication: •Jaw closure: masseter and temporalis •Side to side grinding: pterygoids •Buccinator: compresses cheek

Deep chewing muscles

Extrinsic tongue muscles Pharyngeal constrictors

Tongue itself (instrinsic muscles): digestive tract section

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Muscles of the Anterior Neck

Above hyoid (suprahyoid): form floor of oral cavity, anchor tongue, elevate hyoid, move larynx superiorly during swallowing Below hyoid (infrahyoid): depress hyoid and larynx during swallowing and speaking Right side (of

slide) is deeper than left

Sternocleodomastoid

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Neck

Anterolateral neck Scalenes elevate first 2 ribs

Posterior neck Splenius’ (capitis and cervicis) extend head

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Deep muscles of back

Erector spinae (extend back):

Iliocostalis Longissimus Spinalis

Quadratus lumborum (lateral flexion)

Labeled cervicis, thoracics, lumborum depending on where they are

Right side: deeper

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Per Marieb… (worthwhile to know) “During full flexion (i.e. when touching fingertips

to floor), erector spinae are relaxed and strain is borne entirely by ligaments of back; on reversal of the movement, these muscles are initially inactive, and extension is initiated by hamstring muscles of thighs and gluteus maximus muscles of buttocks. As a result of this peculiarity, lifting a load or moving suddenly from a bent over position is potentially injurious to muscles and ligaments of back and intervertebral discs; erector spinae muscles readily go into painful spasms following injury to back structures.”

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Deep muscles of the thorax: breathing

Intercostals Short: rib to rib

Diaphragm prime mover of inspiration

Lift rib cage: inspiratory

Depress rib cage: in forced expiration

Floor of thoracic cavity: when flattens, air moves in

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Anterior Chest Muscles

Deeper: pectoralis minor serratus anterior subclavius

Superficial: sternocleidomastoid pectoralis major

Muscles of the abdominal wall

Note inguinal ligament- from anterior superior iliac spine to pubic symphysis: lower border of external oblique rolls up on itself to form it

From more superficial to deep: External oblique Internal oblique Transversus abdominis Nearer midline: Rectus abdominis

The rectus abdominis is the medial pair of muscles; it is ensheathed by the aponeurosis of the lateral muscles, which don’t come to the midline

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Muscles of the abdominal wall from the side

Muscles moving the scapula trapezius levator scapulae rhomboids

posterior

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9 Muscles crossing shoulder joint: movement of arm (humerus)

Three most powerful of the nine and prime movers: pectoralis major latissimus dorsi deltoid

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Rotator cuff supraspinatus, infraspinatus, subscapularis, teres minor

remaining 2muscles : teres major and coracobrachialis

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Forearm extensors (posterior)

Triceps brachii Anconeus helps

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Forearm flexors (anterior) Brachioradialis

Biceps brachii

Brachialis

3 muscle on right from this site: http://www.rad.washington.edu/atlas/

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Retinaculae (retinaculum, singular)

“retainers,” “wrist bands”, “ankle bracelets”

Bands of fascia holding tendons of wrist and ankle in place (prevent “bow-stringing”)

Tendons covered by slippery tendon sheets

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Forearm muscles: movement of wrist, hand and fingers

Many arise from distal humerus Cross elbow, wrist and finger joints Minimal action at elbow At wrist joint: flexion, extension, abduction and

adduction of the hand At finger joints: mostly just flex and extend (other

movements- by small muscles in the hand itself)

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Forearm muscles, continued Two compartments (each with superficial and

deep muscle layers) Anterior = flexor compartment ( except includes 2 pronators)

Most originate from a common tendon on the medial epicondyle of humerus

Posterior = extensor compartment (except includes supinator and brachioradialis)

Many arise from a common tendon from lateral epicondyle of humerus

Most muscles that move the palm and fingers are located in the forearm, not the hand itself They operate by tendons like strings with puppets There are some small muscles in the hand itself

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Anterior wrist pronator and flexors Origin on medial epicondle of humerus: pronator teres, flexor carpi

radialis, palmaris longus, flexor carpi ulnaris, flexor digitorum superficialis

Pronator teres

Palmaris longus

http://www.rad.washington.edu/academics/academic-sections/msk/muscle-atlas

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Deep anterior hand muscles

(some) Flexor pollicis

longus Flexor digitorum

profundus (only muscle that flexes DIPs)

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Individually (this is right arm, anterior)

Flexor digitorum superficialis

Flexor digitorum profundus Flexor pollicis longus

Pronator quadratus

http://www.rad.washington.edu/academics/academic-sections/msk/muscle-atlas

origin on lateral epicondyl of humerus Extensor carpi radialis

(longus & brevis)

Extensor digitorum

Extensor carpi ulnaris

See individually in next slide

Superficial extensors

Extensor carpi radialis brevis

Extensor carpi radialis longus

Extensor digitorum

Extensor carpi ulnaris

http://www.rad.washington.edu/academics/academic-sections/msk/musc

Deep posterior muscles Extensor pollicis longus & brevis

Abductor pollicis longus

Supinator Extensor indicis

http://www.rad.washington.edu/academics/academic-sections/msk/muscle-atlas

Hand Thenar Hypothenar Midpalmar Lumbricals Interossei

Te

Thenar and hypothenar muscles

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Right forearm, anterior view, from superficial to deep

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Right forearm, posterior, from superficial to deep

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Muscles crossing the hip and knee joints

Three groups separated by fascia; all three enclosed by deep fascia of thigh (fascia lata)

1. Anterior Flex femur at hip; extend leg at knee (e.g. foreswing

phase of walking) 2. Posterior Mostly extend thigh and flex leg (backswing phase of

walking) 3. Adductor (medial) Move thigh only, not leg

Muscles that flex thigh at hip

Sartorius Iliopsoas Tensor fasciae lata Rectus femoris (only

quad with origin on pelvis)

Pectineus (medial compartment)

Originate from vertebral column and pelvis and pass anterior to hip joint

Muscles that flex thigh at hip: individually (go between last slide and this one)

Tensor fascia lata Iliopsoas

Sartorius Rectus femoris

Pectineus

Inserts on tibial tuberosity via patellar tendon

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Thigh extensors (posterior)

Arise posterior to hip joint Gluteus maximus Hamstrings (cross hip

and knee joints: extend thigh & flex knee) Biceps femoris Semitendinosus Semimembranosus

(antagonists of quads)

_______

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Hamstrings Biceps femoris

long head

Biceps femoris short head

Semitendinosus Semimembranosus

cross hip and knee joints: extend thigh and flex knee

http://www.rad.washington.edu/academics/academic-sections/msk/muscle-atlas

Abductors of thigh

Buttocks muscles that lie lateral to hip joint

Gluteus medius

Gluteus minimus (under medius)

Tensor fascia lata

Thigh abductors

Gluteus medius

Gluteus minimus

Buttocks muscles that lie lateral to the hip joint

http://www.rad.washington.edu/academics/academic-sections/msk/muscle-atlas

Lateral rotators Piriformis Also shown are other

rotators and the gluteus muscles

Piriformis laterally rotates hip; also helps abduct hip if

it is flexed

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Adduction of thigh

Muscles originate medial to hip joint

Gracilis Adductor magnus Adductor longus Adductor brevis Pectineus

Thigh adductors (originate medial to hip joint) Adductor magnus

Adductor longus

Pectineus Adductor brevis Gracilis

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Knee extensors Quadraceps femoris – the only extensors of the leg (lower leg) at the knee

Rectus femoris (only

quad with origin on pelvis) Vastus lateralis Vastus intermedius Vastus medialis

Antagonized by hamstrings

Rectus femoris

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Vastus lateralis, intermedius, and medialis Note “o” and

“i”

Rectus femoris (only quad with origin on the pelvis)

Quadriceps

_________ Insert: tibial tuberosity via patellar ligament

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Leg (lower leg) 3 compartments Anterior Posterior Lateral

Movements at joints: Ankle

Dorsiflex Plantarflex

Intertarsal Inversion of foot Eversion of foot

Toes Flex (point) Extend

Posterior compartment of leg

Superficial: these plantarflex foot Gastrocnemius

Soleus

Plantaris

Posterior leg

Soleus

Gastrocnemius

Plantaris

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Posterior leg continued

Deep Popliteus

Flexor digitorum longus

Flexor hallucis longus

Tibilialis posterior

Flexor hallucis longus

Flexor digitorum longus

Tibialis posterior

Popliteus Deep posterior leg

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Anterior leg extensors

Mainly extend toes and dorsiflex foot

Tibialis anterior

Extensor digitorum longus

Extensor hallucis longus

More pics

Tibialis anterior

Extensor digitorum longus

Extensor hallucis longus

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Lateral compartment of leg

Fibularis (peroneus) longus: to first metatarsal

and cuneiform Fibularis (peroneus)

brevis: to fifth metatarsal

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Sole – third (deepest) layer

Addendum: some rotator cuff tests (FYI)

FIGURE 2. Apley scratch test. The patient attempts to touch the opposite scapula to test range of motion of the shoulder. (Left) Testing abduction and external rotation. (Right) Testing adduction and internal rotation.

FIGURE 3. Supraspinatus examination ("empty can" test). The patient attempts to elevate the arms against resistance while the elbows are extended, the arms are abducted and the thumbs are pointing downward.

http://www.aafp.org/afp/20000515/3079.html

FIGURE 4. Infraspinatus/teres minor examination. The patient attempts to externally rotate the arms against resistance while the arms are at the sides and the elbows are flexed to 90 degrees.

FIGURE 6. Hawkins' test for subacromial impingement or rotator cuff tendonitis. The arm is forward elevated to 90 degrees, then forcibly internally rotated.

FIGURE 5. Neer's test for impingement of the rotator cuff tendons under the coracoacromial arch. The arm is fully pronated and placed in forced flexion.