human muscles

HUMAN MUSCLES

Chapter 10, Marieb Human A and P text, 8th Ed.

MUSCULAR FUNCTION

Muscles pull on bones and act as lever systems. Muscles have an tendinous origin which is immovable, and a tendinous insertion which is movable.

Classes of Levers (review) - see p. 325.

First Class Lever - resembles a see-saw with a fulcrum in the middle of the force and effort. It is diagrammed as E-F-R. An example is the splenius capitis which inserts on the occipital bone of the skull, extending it (the force) and pulling the chin (the resistance). Examine the illustration on p. 325, which joint is the fulcrum?

Second Class Lever - resembles a wheel barrow - the gastrocnemius muscle pulls the heel (calcaneus) upward [like you are lifting the handles of the wheel barrow], this causes the metatarsal/phalange [the wheel] joint to press against the floor. When you stand up on your toes, the resistance is the weight of the body pressing down on the ankles. The second class lever is diagrammed F-R-E.

Third Class Lever - the fulcrum and resistance are at opposite ends, the effort in between. The historical Jesus picked up and shouldered his cross this way. Examples are the adductors of the thigh, tweezers, and lifting a shovel of dirt. The fulcrum is the hip joint, the effort is the adductors' contractions and the resistance is the weight of the leg. The third class lever is diagrammed F-E-R.

ACTIONS

For instance, your biceps will flex your forearm by pulling on its insertion on the radius. The biceps of the anterior muscle compartment is the primary mover or agonist. Opposing the action of the biceps is the triceps of the posterior muscle compartment of the arm - the triceps is the antagonist of the movement. If you extend your forearm, the actions and functions of the two muscles are reversed.

In order to flex or extend a forearm carrying a heavy load, the shoulder (scapula) must be held in place. The rhomboideus muscles would serve as fixators.

Many movements also require that muscles serve as synergists which assist the movement.

SELECTED MUSCLES AND FUNCTIONS

Most of the muscles and their movements will be covered in lab.

Muscle Principal Origin/Insertion ActionHEAD REGIONOccipitalis Occipital/galea aponeurosis draws scalp backwards

Frontalis Frontal/galea aponeurosisdraws scalp forwards, wrinles forehead

Orbicularis oris skin at corners of mouth closes lipsZygomaticus zygomatic process/mouth corner smilingDepressor anguli oris

mandible/mouth corner frowning

Buccinator maxilla/orbicularis oris sucking Risorius parotid fascia/corner of mouth “rage” expressionOrbicularis oculi orbit/orbit closes eyesMasseter zygomatic arch/mandible chewing

Temporalisparietal/coranoid process of mandible

chewing

Label as above. See p. 330.

Digastricmandible + mastoid/hyoid

opens mouth

Mylohyoid inner mandible/hyoidaids swallowing, flattens floor of mouth and elevates the tongue

Label as above. See p. 341

.

Sternocleidomastoidsternum + clavicle/mastoid

turns head R or L, shrug shoulders

Splenius capitis vertebrae/occipital extends head


TRUNKRectus abdominus pubis/rib cartilages tightens mid-line in defecationExternal oblique ribs/linea alba compresses abdomenInternal oblique iliac crest/rib cartilages compresses abdomenTransverse abdominus iliac crest/linea alba compresses abdomen

Thoracic - deep

Diaphragmribs + lumbar vert./central tendon

inhalation, increases volume of the thoracic cavity

External intercostals

adjacent ribs elevates rib cage in inhalation

Internal intercostals

adjacent ribs depresses rib cage

Pectoralis minorribs #3-5 /coracoid of scapula

moves scapula anteriorly, elevates rib cage


Thoracic - superficial

Pectoralis majorsternum and clavicle/greater tubercle of humerus

adducts arm


Serratus anterior ribs/scapula abducts scapula, elevates ribs. What is winged scapula?

Label as above. See pg. 352.

Back

Trapeziusoccipital + vertebrae/clavicle + scapula

upper div. elevates clavicle; for climbing, elevates scapula

Levator scapulae cervical vertebrae/scapula elevates scapulaRhomboideus thoracic vertebrae/scapula adducts and fixates scapulaLatissimus dorsi vertebrae/humerus draws arm back Quadratus lumborum

iliac crest/12th rib and lumbar vertebrae

draws torso R and L inferiorly

(Use the cat terms for the three sections of the trapezius. See the Mareib lab manual.)

Label as above. See p. 354-357

SHOULDER/ARM - See p. 351.

(Back-see above)

Teres major scapula/intertubular groove of humerus adducts armTeres minor inf. border scapula/great.tub.of humerus rotates arm laterally

Deltoid clavicle + scapular spine/deltoid tuberosity of humerus

flexes and abducts arm

Use the cat terms (achromiodeltod, clavodeltoid and spinodeltoid) for the three

sections of the deltoid.

Subscapularis anterior scapula/humerus rotates arm medially

Name this muscle.

Supraspinatusposterior, upper scapula/tubercle of humerus

abducts arm

Infraspinatus inf. angle of scapula/tubercle of humerus rotates arm laterally

ARM - See p. 352-354.

Biceps brachii coracoid + scapula/radiusflexes forearm, flexes arm

Brachialis ant. humerus/ulna flexes forearm Brachioradialis distal humerus/radius flexes forearm

Triceps brachiipost.scapula, glenoid fossa and humerus/olecranon process

extends forearm

Pronator teres med. epicondyle of humerus/radius pronates arm

Supinator lat. epicondyle of humerus/radiussupinates arm and hand


HIP and THIGH - See p. 364.

Iliacus ant.iliac fossa/lesser trochanter via psoas tendon

flexes and rotates thigh laterally

Psoas major lumbar vert./lesser trochanter as above Pectineus pubis/femur flexes, adducts thigh

-

Label as above. See p. 362-369.

Gluteus maximuspost. sacroiliac area/post. femur under greater trochanter

rotates thigh laterally

Gluteus medius Iiium/greater trochanterrotates thigh medially

Tensor fasciae latae Iiiac crest/ant.tibia flexes, abducts thigh

Adductor longus/magnus

pubis/linea aspera of femur adducts thigh

QUADS

Rectus femoris iliac spine/patellaflexes thigh and extends leg

Vastus lateralis, medialis, intermedius

greater trocanter and linea aspera/tibial tuberosity via the patellar tendon

extends leg


HAMSTRINGS

Biceps femorisischial tuberosity + linea aspera/fibula and lat. condyle of tibia

extends thigh and flexes leg

Semitendinosus ischial tuberosity/tibia flexes legSemimembranosus ischial tuberosity/med.condyle of tibia as above

Label as above. See pg. 367.

OTHERS

Gracilis pubis/tibia adducts thigh Sartorius iliac spine/tibia rotates leg laterally Tibialis anterior tibia/ superior first metatarsal dorsiflexes footExtensor digitorum longus

tibia + fibula/phalanges extends toes

Peroneus longusfibula + tibia/inferior first metatarsal

everts foot, plantar flexes foot

Shinsplints is a term for inflammations of the tibial periosteum of tendinitis associated with the tibialis posterior or anterior. It usually results from running on hard surfaces.


Gastrocnemius post.knee/calcaneus plantar flexion, "standing on

toes,” flexes legFlexor digitorum longus

post.tibia/distal phalanges

flexes toes, inverts foot

Questions

1. What is RICE therapy for muscle injuries?

2. Which muscles are the typical ones for arm, hip and thigh injections?

3. Compare the lever classes and explain one example of each.

4. Review the principal actions of the muscles above by making your own table.

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human muscles

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