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Hey kids! I'm Marty Muscle, and today I'm 

going to tell you about some muscles used in 

everyday movement!

Before we begin let's go over some basic vocabulary!

Origin: The origin is a point where the muscle attaches to bone, 

the origin is usually on a less movable bone.

Insertion: The insertion is another point where the muscle attaches 

to bone or skin, however the insertion is usually on the more 

movable bone. 

Pectoralis Major 

Some of you may know this part of the body as the chest, but do you know any of the muscles in the chest? One 

important muscle in the chest is the Pectoralis Major. Pectoralis comes from the word pectoral which means 

chest, and Major means that this muscle is important to the body. The origins, or attachment points, of the 

Pectoralis are at the Sternum (breast bone), clavicle (collar bone), and the first to sixth ribs. The muscle's 

insertion, another attachment point, is at the humerus, which is your upper arm bone. 

The Pectoralis Major acts on the Humerus, Clavicle, Scapula (shoulder blade), and the Shoulder joint. The job of 

the Pectoralis Major is to assist in moving the arm, across the body, up and down, etc. The type of movements the 

Pectoralis Major performs include flexion, extension, rotation and adduction of the arm at the shoulder. 

Adduction is moving the limb, in our case the arm, towards the middle of the body (midline). This muscle is known 

as a prime mover, because it is responsible for the major action of the arm. The Pectoralis Major is used in every 

day movement like throwing and climbing.

The Muscular System. Retrieved from 

http://faculty.ncwc.edu/ddaley/B231%20

muscular%20sys.htm . 

Pectoralis Major Muscle. Retrieved from 

http://www.getbodysmart.com/ap/muscu

larsystem/armmuscles/anteriormuscles/p

ectoralismajor/tutorial.html.

Abductor Pollicis Brevis

One important muscle in your hand is the Abductor Pollicis Brevis. Abductor means that this muscle moves a body 

part, in this case the thumb, away from the midline of the hand. Pollicis means thumb, and Brevis means short, so 

the Abductor Pollicis Brevis is a short thumb muscle that pulls the thumb away from the hand. Its origin is the 

Carpal bones (wrist), more specifically the Scaphoid and Trapezium bones. The insertion is on the phalange in the 

thumb closest to the wrist bones (the proximal phalange). 

This muscle acts on the phalanges in the thumb and carpal bones closest to the thumb, they are know as the 

Scaphoid and Trapezium, and proximal phalange in the thumb. It also acts on the carpometacarpal joint and the 

metacarpophalangeal joint. It is an abductor muscle, so it moves the thumb away from the from the hand. The 

Abductor Pollicis Brevis is a prime mover because it is responsible for the action of the thumb. You kids use this 

muscle every day when you text your friends! 

Loyola University Medicanl Education 

Network. Abductor Pollicis Brevis. Retrieved 

from 

http://www.lumen.luc.edu/lumen/meded/gr

ossanatomy/dissector/mml/abpb.htm

Tibialis Anterior

Tibialis comes from tibial meaning located near the tibia (inner and larger leg bone). Anterior tells us that 

it is located on the front side of the body.   It originates at the tibia, and inserts on the first tarsal and 

metatarsal in the foot. It acts on the tibia, metatarsals, and tarsals. This muscle inverts the foot, and 

dorsiflexes the foot. Dorsiflexion is when your foot is flexed, for example standing on your heels. The 

tibialis is a prime mover, but an antagonist to the Gastrocnemius. You use this muscle every day when you 

walk or kick a ball! 

Next we are going to talk about a pair of antagonistic leg muscle, the Tibialis Anterior and 

the Gastrocnemius! Antagonistic means that these 2 muscles oppose the action of the other 

to perform a movement. 

Contracted Tibialis 

Anterior -->

Gastrocnemius

The Gastrocnemius is just the fancy name for the calf muscle. Gastrocnemius 

means "stomach of the leg". Its origin is on the lower end of the femur, and its insertion is on the calcaneus 

bone, which is your heel bone. It acts on the patella (knee cap), and the bones in the foot (metatarsals and 

tarsals). It also acts on the knee joint, and ankle joint. This muscle plantar flexes the foot, which is 

movements like pointing your toes, or standing on your toes. The Gastrocnemius also flexes the knee (bends 

the knee). This muscle is a prime mover, but an antagonist to the Tibialis Anterior. It points the foot/toes, 

and the Tibialis Anterior flexes the foot. This muscle is commonly used in dancing, jumping, walking, and 

standing on toes to reach things in tall places. 

<-- Contracted 

Gastrocnemius

(relaxed Tibialis Anterior)

Rectus Abdominus 

We have a special treat for you kids today! Here's some information about an additional muscle you may 

know as "six pack" or "abs". One specific abdomen muscle is the Rectus Abdominis.   Rectus refers to the 

straight muscles in the abdomen or the eye, and Abdominis means that it is located in the abdomen. It 

originates at the Pubis bone, which is part of your pelvic bone. Its insertion is on the Sternum (breast bone) 

and fifth to seventh ribs. 

The Rectus Abdominus acts on the ribs and the spine (vertebrael column), and assists in flexing the spine 

and front trunk in movements such as bending over, and side to side. This muscle is a   flexion muscle, and a 

prime mover. A common use of the Rectus Abdominus is bending over to pick something up, and breathing. 

Another fun muscle we're studying is the Flexor Digitorum in the foot.   It's 

full name is flexor digitorum brevis which means short posterior digits.   It's 

origin is on the calcaneus and it inserts on toe phalanges 2-5.   It interacts 

with the calcaneus and the phalanges of toes 2-5.   It is responsible for 

flexion of the four last toes.   It is a prime mover of the toes.   It helps you 

leave your stride of your back leg while walking.

Source: Anatomyexpert. (n.d.). Retrieved from 

http://www.anatomyexpert.com/structure_detail/5854/22213/

The muscle relaxed 

(left) and flexed 

(right).

Next is a pair of Antagonistic arm muscles!

First up is the biceps, or scientifically speaking, musculus biceps 

brachii (meaning biceps muscle of the arm).   The biceps orginate at 

the Scapula (shoulder blade) and inserts eventually on the proximal 

side of the radius.   It acts on the scapula, humerus, ulna, and radius; 

and affects the shoulder and elbow joints.   The biceps help flex the 

forearm and supinate (twist) it too!   The biceps muscle is a prime 

mover.   An everyday use for this muscle is to lift your backpack off 

the floor as the bell rings.

The biceps flexed (or the 

triceps extended)

<---

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