The obliquus externus (external oblique) muscle is the outermost muscle covering the side of the abdomen. It is broad, flat, and irregularly quadrilateral.

The obliquus internus (internal oblique) muscle is triangularly shaped and is smaller and thinner than the external oblique muscle that overlies it.

The transversus abdominis muscle is flat and triangular, with its fibers running horizontally. It lies between the internal oblique and the underlying transversalis fascia. The rectus abdominis muscles are long and flat. The muscle is crossed by three tendinous intersections called the linae transversae.

The rectus abdominis is enclosed in a thick sheath formed, as described above, by fibers from each of the three muscles of the lateral abdominal wall.

The pyramidalis muscle is small and triangular. It is located in the lower abdomen in front of the rectus abdominis.

The muscles of mastication originate on the skull and insert into the mandible There are four muscles of mastication: masseter, temporalis, medial pterygoid and lateral pterygoid. Each of these primary muscles of mastication is paired, with each side of the mandible possessing one of the four. While these four muscles are the primary participants in mastication, other muscles are usually helping the process, such as those of the tongue and the cheeks.

The Sternocleidomastoideus (Sternomastoid muscle) passes obliquely across the side of the neck and it acts to flex and rotate the head. It also acts as an accessory muscle of inspiration along with scalene muscles of the neck. The Sternocleidomastoideus varies much in the extent of its origin from the clavicle: in some cases the clavicular head may be as narrow as the sternal; in others it may be as much as 7.5 cm. in breadth. When the clavicular origin is broad, it is occasionally subdivided into several slips, separated by narrow intervals.

Fibrous joints are immovable and they occur in bones which are connected by dense connective tissue, consisting mainly of collagen.

The fibrous joints are divided into three types:

• Sutures are found between bones of the skull. In fetal skulls the sutures are wide to allow slight movement during birth. They later become rigid (synarthrodial).
• Syndesmosis are found between long bones of the body, such as the radius and ulna in forearm and the inferior tibio-fibular joint in leg. Unlike other fibrous joints, syndesmoses are moveable (amphiarthrodial).
• Gomphosis is a peg and socket joint between the root of a tooth and the sockets in the maxilla or mandible.

The human body has five types of bones:

• Long bones are consisting of a long shaft (the diaphysis) plus two articular (joint) surfaces, called epiphyses. They are comprised mostly of compact bone, but are generally thick enough to contain considerable spongy bone and marrow in the hollow centre (the medullary cavity). Most bones of the limbs (including the three bones of the fingers) are long bones, except for the kneecap (patella), and the carpal, metacarpal, tarsal and metatarsal bones of the wrist and ankle.
• Short bones are roughly cube-shaped, and have only a thin layer of compact bone surrounding a spongy interior. The bones of the wrist and ankle are short bones, as are the sesamoid bones.
• Flat bones are thin and generally curved, with two parallel layers of compact bones sandwiching a layer of spongy bone. Most of the bones of the skull are flat bones, as is the sternum.
• Irregular bones do not fit into the above categories. They consist of thin layers of compact bone surrounding a spongy interior. As implied by the name, their shapes are irregular and complicated. The bones of the spine and hips are irregular bones.
• Sesamoid bones are bones embedded in tendons. Since they act to hold the tendon further away from the joint, the angle of the tendon is increased and thus the force of the muscle is increased. Patella is the example of sesamoid bone.

The buccinator is a thin quadrilateral muscle, occupying the interval between the maxilla and the mandible at the side of the face. It is forming the wall of the cheek. The buccinator originates from the alveolar processes of the maxillary bone and mandible, pterygomandibular raphe and the insertion point is in the fibres of the orbicularis oris.

The orbicularis oris muscle is the sphincter muscle around the mouth. This muscle is not a simple sphincter muscle like the Orbicularis oculi, it consists of numerous strata of muscular fibers surrounding the orifice of the mouth but having different direction.

There are two temporal bones and they are situated at both sides at the base of the skull. The temporal bone supports that part of the face known as the temple.

Each temporal bone consists of five parts:

Squama temporalis, Mastoid portion, Petrous portion, Tympanic part, Styloid process (temporal).

Extension is an action where there is an increase in the angle of a joint. For example, extension is produced by extending the flexed elbow. The arm has now been straighten, hence it has been extended. When the head is tilted all the way back, it is said to be extended.