1.Gluteus maximus and Gluteus minimus
This muscles are classified by their size. Maximus means the largest of the group, which is correct because the others are small and medium sized). Gluteus minimus is the smallest of the group.
2.Frontalis and Temporalis
The frontalis and the temporalis muscles are classified by their location. Frontalis is front of the frontal bone of the skull; It serves for facial expressions, raising eybrows.
Temporalis is located on top of the temporal bone of the skull; Is able to move the tmandible.
3. Orbicularis Oculi and Transverse abdominis:
These muscles are far away from each other but they were named based on the same feature: the direction of fibers.
Orbicularis is because their fibers form a circle.
Transverse because crosses or 'traverses' the abdomen
4.Flexor Carpi Ulnaris and Extensor digitorum longus
These muscles are classified by what they do- their action.
Flexor carpi ulnaris flexes the hand at the wrist while the extensor digitorium longus extends the foot and toes upward.
5. Sternocleidomastoid and Brachioradialis
These muscles are named based on their origin and insertion.
Sternocleidomastoid has two origins, one in the sternum and the other in the collare bone (clavicle). It's insertions is in the mastoid process of the temporal bone.
Brachioradialis has an origin on the brachium of the humerus and it's insertion is on the radius.
6. Biceps Brachii and Triceps Brachii
These muscles, with opposite functions, are named based on their number of origins.
Biceps brachii has two origins on the scapula that join to form a single muscle which is attached to the forearm
Triceps brachii has three origins on the humerus and joint to form one single muscle that attaches to the ulna.
