Principle Skeletal Muscle-1

Principal Skeletal Muscles in Body

Despite the fact that there are over 700 distinct skeletal muscles in the human body, by focusing on the large superficial muscles and muscle groups, it is possible to understand and appreciate skeletal muscles.

Facial Muscles

• Frontalis: Frontal bone is covered. This muscle enters into the skin of the eyebrows after running from the cranial aponeurosis. Raising one's brows and furrowing one's forehead are both possible thanks to the frontalis muscle.
• Orbicularis Oculi: This muscle's fibers wrap around the eyes in a circular pattern. One can close their eyes, squint, blink, and wink because of the existence of this muscle.
•  Orbicularis Oris: Likewise known as the kissing muscle. This spherical muscle surrounds the mouth. This is what causes one's mouth to close and protrude.
• Buccinator: This muscle inserts into the orbicularis oris and travels over the cheek. During chewing, this muscle is crucial. As it squeezes the cheek to keep the food between the teeth while chewing, it is classified as a chewing muscle. This muscle flattens the cheek when a person is whistling or blowing a trumpet.
• Zygomaticus: As it raises the mouth corners upward, this muscle is known as the "smiling muscle."
• Chewing muscles: The masseter and the temporalis are two further chewing muscles in addition to the buccinators mentioned above. The masseter, which is a muscle covering the lower jaw, lifts the mandible when closing the jaw during chewing. The fan-shaped temporalis muscle inserts into the mandible and cooperates with the masseter to close the jaw.
• Neck muscles: The platysma and sternocleidomastoid are two neck muscles. The muscle that covers the neck anteriorly and laterally is called the platysma. It causes a downward sag of the mouth by pulling the corners of the mouth inferiorly. The sternocleidomastoid, another neck muscle, can be found on both sides of the neck.

Two heads make up the sternocleidomastoid muscles. Each muscle has two heads, one of which emerges from the sternum and the other from the clavicle. The neck flexes when the sternocleidomastoid muscles work together. The head will turn to the opposite side if only one sternocleidomastoid muscle contracts.

Trunk Muscles

Anterior Muscles

• Pectoralis major: This muscle has a broad fan-like form and covers the top of the chest. The function of this muscle is the adduction and flexion of the axilla. It creates the axilla's anterior wall.
• Intercostals muscles: These muscles are deep within the ribcage. The rib cage is a crucial part of breathing because the muscles in the external intercostals help lift it to allow air to enter. On the other hand, when a person exhales forcefully, the internal intercostals ribs support the movement of air out of the lungs.
• Muscles of the abdominal girdle: The anterior and posterior abdominal muscles make up the two categories into which the muscles of the abdominal girdle are divided. The body trunk is strengthened by the anterior muscles. These two muscles are capable of holding in and safeguarding the contents of the abdomen.

Anterior Abdominal Muscles

• Rectus abdominis muscle: The most superficial muscle in the abdomen is this pair of strap-like muscles. Flexing the vertebral column is the rectus abdominis muscle's primary job. This muscle contracts to compress the abdominal contents during defecation and childbirth. In addition, it participates in forced breathing.
• External Oblique muscle: The lateral walls of the abdomen are constructed by this pair of muscles. Like the rectus abdominis muscle, its primary job is to flex the spinal column. But they also rotate the trunk and lateralize it..
•  Internal oblique muscle: The purpose of this paired muscle is identical to that of the external oblique muscles.

Posterior Muscles

• Trapezius muscles: These muscles make up the trunk's posterior and most superficial muscles. They act as the sternocleidomastoids' antagonists and have the ability to elevate, depress, adduct, and stabilize the scapula. The trapezius muscles form a diamond- or kite-shaped muscle mass when viewed collectively.
• Latissimus dorsi muscle: This extensive, flat pair of muscles runs the length of the lower back. The humerus is extended and adducted by the latissimus dorsi muscle. When swimming or striking a blow, this muscle is essential for bringing the arm down in a power stroke.
• Erector spinae muscle: This muscle group plays a key role in the expansion of the back. Erector spinae muscles help govern the movement of bending over at the waist in addition to acting as strong back extensors. These muscles spasm as a result of a back injury, which is a common cause of lower back pain. Three muscle columns that span the length of the vertebral column make up each erector spinae muscle. The three muscle columns are the spinalis, longissimus, and iliocostalis.
• Deltoid muscles: These fatty, triangular-shaped muscles give shoulders their rounded contour. They have been the most popular and often used injection sites because they are bulky. The main muscles responsible for arm abduction are the deltoid muscles.

Muscles of the Upper Limb

Three groups make up the muscles in the upper limbs.

• First group: Branches of muscles that originate in the shoulder girdle cross the shoulder joint and enter the humerus. These muscles enable arm motion.
• Second group: Muscles that attach to the forearm bones and envelop the humerus. The elbow joint may move because to these muscles.
• Third group: Includes the forearm muscles responsible for their motion.

Muscles of the Humerus that Act on the forearm

• Biceps brachii: When the elbow is flexed, this muscle enlarges. It works to supinate the forearm and is a strong prime mover for forearm flexion.
• Brachialis: This muscle is crucial for flexing the elbow. It is close to the biceps muscle in depth.
• Brachioradialis: This muscle is not very strong. It starts on the humerus and enters the forearm's distal end.
• Triceps brachii: The posterior humerus is only supported by this muscle. It is the elbow extension's strong prime mover. The "boxer's muscle" is another name for this muscle because it can throw a straight-arm knockout punch. This muscle is the biceps brachii muscle's adversary.