HUMAN MUSCLES
Superficial human muscles anterior supinated view








Chapter 10, Marieb Human A and P text, 9th 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 pg. 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 page 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 Action
HEAD REGION
Occipitalis Occipital/galea aponeurosis draws scalp backwards
Frontalis Frontal/galea aponeurosis draws scalp forwards, wrinles forehead
Orbicularis oris skin at corners of mouth  closes lips
Zygomaticus zygomatic process/mouth corner smiling
Depressor anguli oris mandible/mouth corner frowning 
Buccinator maxilla/orbicularis oris sucking 
Risorius parotid fascia/corner of mouth “rage” expression
Orbicularis oculi  orbit/orbit closes eyes
Masseter  zygomatic arch/mandible chewing
Temporalis parietal/coranoid process of  mandible  chewing

 

Human head anterior muscles
Label as above. See p. 333.

 

Digastric mandible + mastoid/hyoid opens mouth 
Mylohyoid  inner mandible/hyoid aids swallowing, flattens floor of mouth and elevates the tongue

-

Anterior neck muscles
Label as above. See p. 335.
.

Sternocleidomastoid sternum + clavicle/mastoid turns head R or L, shrug shoulders
Splenius capitis vertebrae/occipital extends head 

 
 

Left lateral neck muscles
Label as above. See p. 337.


TRUNK
Rectus abdominus pubis/rib cartilages tightens mid-line in defecation
External oblique  ribs/linea alba  compresses abdomen
Internal oblique iliac crest/rib cartilages compresses abdomen
Transverse abdominus iliac crest/linea alba compresses abdomen 

 
 
 
Thoracic - deep
Diaphragm ribs + 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 minor ribs #3-5 /coracoid of scapula moves scapula anteriorly, elevates rib cage
-

Sternum and rib cage muscles
Label as above. See p. 341.
Thoracic - superficial
Pectoralis major sternum and clavicle/greater tubercle of humerus adducts arm 

 

Superficial muscles of thorax and abdomen
Label as above. See pg. 341-344.



 
 
 
 
Serratus anterior ribs/scapula  abducts scapula, elevates ribs. 
What is winged scapula?
See http://freespace.virgin.net/steven.fromm/index.htm

Serratus anterior and external intercostals
 Label as above. See pg. 347.


Back
Trapezius occipital + vertebrae/clavicle + scapula upper div. elevates clavicle; for climbing, elevates scapula 
Levator scapulae cervical vertebrae/scapula elevates scapula
Rhomboideus thoracic vertebrae/scapula adducts and fixates scapula
Latissimus 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.)
 
 

Superficial muscles of back
Label as above. See p. 439.

SHOULDER/ARM - See p. 351

(Back-see above)
Teres major scapula/intertubular groove of humerus adducts arm
Teres minor inf. border scapula/great.tub.of humerus rotates arm laterally
Deltoid  clavicle + scapular spine/deltoid 
      tuberosity of humerus 
flexes and abducts arm

 
 

Deltoid
Use the cat terms ( achromiodeltod, clavodeltoid and spinodeltoid) for the three sections of the deltoid.

 

Subscapularis  anterior scapula/humerus  rotates arm medially

Supraspinatus and infraspinatus
Name this muscle.

 

Supraspinatus posterior, upper scapula/tubercle 
          of humerus 
abducts arm 
Infraspinatus inf. angle of scapula/tubercle of humerus rotates arm laterally

 

ARM - See page 355.
 
Biceps brachii coracoid + scapula/radius flexes forearm, flexes arm
Brachialis ant. humerus/ulna flexes forearm 
Brachioradialis distal humerus/radius flexes forearm
Triceps brachii post.scapula, glenoid fossa and humerus/olecranon process extends  forearm
Pronator teres med. epicondyle of humerus/radius pronates arm
Supinator lat. epicondyle of humerus/radius supinates arm and hand

 
 

Superficial muscles of anterior armBrachialis and coracobrachialis
Label as above. See p. 355-358.

Biceps brachilais and brachioradialisSuperficial muscles of medial arm and anterior forearm
Label as above. See p. 357.

HIP and THIGH - See p. 367-371
 
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

-

Iliacus, psoas major, diaphragm and anterior superficial thigh muscles
Label as above. See pg. 364.
Gluteus maximus post. sacroiliac area/post. femur under greater trochanter rotates thigh laterally
Gluteus medius Iiium/greater trochanter rotates thigh medially
Tensor fasciae latae  Iiiac crest/ant.tibia  flexes, abducts thigh
Adductor longus/magnus pubis/linea aspera of femur adducts thigh 

 
 
 
 

Rectus femoris, patellar ligament and medial adductors of thigh
 Label as above. See p. 367.



QUADS
 
Rectus femoris iliac spine/patella flexes thigh and extends leg
Vastus lateralis, medialis, intermedius  greater trocanter and linea aspera/tibial tuberosity via the patellar tendon extends leg 

 

Anterior superficial muscles of the thigh
Label as above. See p. 368.

HAMSTRINGS
 
 
Biceps femoris ischial tuberosity + linea aspera/fibula and lat. condyle of tibia  extends thigh and flexes leg
Semitendinosus ischial tuberosity/tibia  flexes leg
Semimembranosus ischial tuberosity/med.condyle of tibia as above 

 
 

Posterior superficial muscles of thigh
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 foot
Extensor digitorum longus tibia + fibula/phalanges  extends toes
Peroneus longus fibula + 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.
 
 

Laterial muscles of leg
Label as above. See p. 371.


 
Gastrocnemius post.knee/calcaneus  plantar flexion,”standing on toes,” flexes leg
Flexor 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.