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Gross Anatomy of Skeletal Muscles - Coggle Diagram
Gross Anatomy of Skeletal Muscles
Head and Neck Muscles
The head muscles have many specific functions but are usually grouped into two large categories- facial muscles and chewing muscles. Facial Muscles are unique because they insert into soft tissues, such as other muscles or skin. When they pull on the skin of the face, they permit us to express ourselves by frowing, smiling and so forth. The chewing muscles being to break down food for the body.
Facial Muscles
Frontalis and Occipitals:
The frontalis which cover the frontal bone, runs from the cranial aponeurosis to the skin of the eyebrows, where it inserts. This muscle allows you to raise your eyebrows, and to wrinkle your forehead.
At the posterior end of the cranial aponeurosis is the small occipital muscle, which covers the posterior aspect of the skull and pulls the scalp posteriorly.
Orbicularis Oculi:
The fibres of the orbicularis oculi run in circles around the eyes. It allows you to close your eyes, squint, blink, and wink.
Orbicularis Oris:
The orbicularis oris is the circular muscle of the lips. Often called the "kissing" muscle, it closed the mouth and protrudes the lips.
Buccinator:
The fleshy buccinator muscle runs horizontally across the cheek and inserts into the orbicularis oris. It flattens the cheek (as in whistling or blowing a trumpet). It is also listed as a chewing muscle because it compresses the cheek to hold food between the teeth during chewing.
Zygomaticus:
The zygomaticus extends from the corner of the mouth to the cheek bone. It is often referred to as the smiling muscle because it raises the corners of the mouth.
Masseter:
As it runs from the zygomatic process of the temporal bone to the mandible, the masseter covers the angle of the lower jaw. This muscle elevates the mandible to close the jaw.
Temporalis:
The temporalis is a fan-shaped muscle overlying the temporal bone. It inserts into the mandible and acts as a synergist of the masseter in closing the jaw.
Neck Muscles
Platysma:
The platysma is a single sheetlike muscle that covers the anterolateral neck. It originates from the connective tissue covering of the chest muscles and inserts into the area around the mouth. Its actions is to pull the corner of the mouth inferiorly producing a downward sag of the mouth.
Sternocleidomastoid: The paired sternocleidomastoid muscles are two headed muscles, one found on each side of the neck. Of the two heads of each muscle, one arises from the sternum and the other arises from the clavicle. The heads fuse before inserting into the mastoid process of the temporal bone. When both sternocleidomastoid muscles contract together they flex your neck. If just one muscle contracts, the face is rotated towards the shoulder on the opposite side and tilts the head to its own side.
Trunk Muscles
The trunk muscles include muscles that move the vertebral column (most of which are posterior anti-gravity muscles); (2) anterior thorax muscles, which move the ribs, head and arms and (3) muscles of the abdominal wall, which "holds your guts in" by forming a natural girdle and help to move the vertebral column.
Anterior Muscles
Pectoralis Major:
The pectoralis major is a large fan-shaped muscle covering the upper part of the chest. Its origin is from the sternum, shoulder girdle and the first six ribs. It inserts on the proximal end of the humerus. This muscle forms the anterior wall of the axilla (armpit) and acts to adduct and flex the arm.
Intercostal Muscles:
The intercostal muscles are deep muscles found between the ribs. The external intercostal, which lie toward the lateral edge of the rib cage, are important in breathing because they help to raise the rib cage when you inhale. The internal intercostals, which lie deep and medial to the external intercostals, depress the rib cage, helping to move air out of the lungs when you exhale forcibly.
Muscles of the Abdominal Girdle
The anterior abdominal muscles (rectus abdominis, external and internal obliques and transversus abdominis) form a natural "girdle" that reinforces the body trunk. Taken together, they resemble the structure of plywood because the fibres of each muscle or muscle pair run in a different direction. Just as plywood is exceptionally strong for its thickness, the abdominal muscles form a muscular wall that is well suited for its job of containing and protecting the abdominal contents.
Rectus abdominis:
The paired straplike rectus abdominis muscles are the most superficial muscles of the abdomen. They run from the pubis to the rib cage, enclosed in an aponeurosis. Their main function is to flex the vertebral column. They also compress the abdominal contents during defecation and childbirth (they help you "push") and are involved in forced breathing.
External Oblique:
The external oblique muscles are paired with superficial muscles that make up the lateral walls of the abdomen. Their fibres run downwards and medially from the last eight ribs and insert into the ilium. Like the rectus abdominis, together they flex the vertebral column, but individually they also rotate the trunk and bend it laterally.
Internal Oblique:
The internal oblique muscles are paired muscles deep to the external obliques. Their fibres run at right angle to those of the external obliques. They arise from the iliac crest and insert into the last three ribs. Their functions are the same as those of the external obliques.
Transversus abdominis:
The deepest muscle of the abdominal wall, the transversus abdominis has fibres that run horizontally across the abdomen. It arises from the lower ribs and iliac crest and inserts into the pubis. This muscle compresses the abdominal contents like a wide belt.
Posterior Muscles
Trapezius:
The trapezius muscles are the most superficial muscles of the posterior neck and upper trunk. When seen together, they form a diamond or kite-shaped muscle mass. Each muscle runs from the occipital bone of the skull down the vertebral column to the end of the thoracic vertebrae. They then flare laterally to insert on the scapular spine and clavicle. The trapezius muscles extend the head (thus they are antagonists of the sternocleidomastoids). They also can elevate, depress, adduct and stabilise the scapula.
Latissimus Dorsi:
The latissimus dorsi muscle are the two large, flat muscles that cover the lower back. They originate on the lower spine and illium and then sweep superiorly to insert into the proximal end of the humerus.