the muscular system

The Muscular System

Muscles in the Body

There are over 650 muscles in the human body.

They are named due to many factors.

Naming Skeletal Muscles (1) Location of muscle

Bone or body region associated with the muscle

Shape of muscle Ex: deltoid (triangular)

Relative size Ex: maximus (large), minimus

(small), longus (long) Direction of fibers

Ex: rectus (fibers run straight), transversus, oblique (fibers run at angles to an imaginary defined axis.

Naming Skeletal Muscles (2)

Number of origins Ex: biceps (2 origins) and triceps

(3 origins) Location of attachments

Named according to point of origin or insertion.

Action Ex: flexor or extensor, as in the

names of muscles that flex or extend.

Muscles of the Scalp

Epicranius 2 part muscle consisting of the following:Frontalis

Primary function is to raise the eyebrows.Occipitalis

Works with the frontalis

Temporalis Located on the

side of your forehead.

One of the major muscles of mastication (chewing) Allows you to raise

your cheeks

Sternocleidomastoid Muscles

Anterior muscles of the neck that act to flex and rotate the head.

Trapezius Large muscle that

extends from the neck to a person’s back.

Responsible for: Shrugging Turn head side to side. Drawing the shoulder

bones toward the midline. Pulling the shoulder

blades down. Elevate the scapula Rotate the scapula

Deltoid Muscle forming the

round contour of the shoulder.

Responsible for:Shoulder abductionLifts the arm from to

the side of the body.

Flexion Extension

Biceps Brachii

Muscles in the upper arm Have several functions:

Flex the elbowRotate the forearm

Triceps

Found in the upper arm. An extensor muscle,

unlike the biceps which act as flexors.

Allows for elbow extension, which allows for pressing activities.

Pectoralis Major

Also known as the “pecs.” Thick, fan-shaped muscle

at the upper front of the chest wall.

Actions: Flexes the humerus (upper

arm) Draws the scapula

anteriorly (back) and inferiorly (down)

Rectus Abdominis

Paired muscle running vertically on each side of the anterior wall of the human abdomen.

Commonly known as the “abs” Functions

Key postural muscle Responsible for flexing the lumbar spine as when

doing a “crunch.”Can play a role in respiration

Oblique Muscles

Located on the sides of the abdomen. Allow you to twist.

Latissimus

Large flat dorso-lateral muscle of the trunk.

Also known as the “lat.” Responsible for:

Extension, adduction, transverse extension, and internal rotation of the shoulder joint.

It also has a synergistic role in extension and lateral flexion of the lumbar spine.

Gluteus Maximus

It is a large muscle in the butt. One of the strongest muscles in your

body. Responsible for:

Extends the femurKeeps body upright when motion is occurring

and when motion stops.

Rectus fermoris

One of the four quadriceps muscles

Located in the middle, front of the thigh.

Functions:Hip flexionKnee extension

Sartorius

A long, thin muscle that runs down the length of the thigh.

Longest muscle in the human body.

Responsible for: Abduction, flexion, and

lateral rotation of the hip Medial rotation of the

knee

Hamstrings

Located in the back of your leg.

Responsible for:Flexion of the kneeWalking, running,

jumping, and controlling some movement of the trunk.

Gastrocnemius

Located in the back part of the lower leg.

Also called the calf. Involved in:

Standing, walking, running, and jumping.

Tibialis anterior

Muscle in the shin that spans the length of the tibia.

Functions to stabilize the ankle and foot.