Muscles: Types, Structure, Action, and Major Muscles of the Body, Lecture notes of Anatomy

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Lecture 3

muscles

Learning objectives

1-know the different types of muscles.

2-know the different types of muscle origins and

insertions.

3- describe the shape and arrangement of

muscle fibers.

4-describe the major muscles of the body.

5- understand the mechanism of muscle action.

6-understand the role of muscles in muscle tone.

General Construction of a Skeletal Muscle The large portion of a muscle is known as its belly or fleshy belly. This muscle is attached to bones by tendons or aponeuroses. Tendons and aponeuroses are similar to each other. However, tendons are cord-like and aponeuroses are broad and flat.

Muscular Nerves, Arteries, Veins,

Lymphatics ( neurovascular bundle)

(1) From the main nerve, artery, vein, lymphatic, there are

branches going to each muscle. These muscular branches

are bound together by a fibrous connective tissue sheath to

form a neurovascular bundle.

(2) The motor point is that specific location on the surface

of the muscle where the neurovascular bundle enters.

(3) A motor unit is the single motor neuron and the

number of striated muscle fibers activated by it

(innervation).

MUSCLE FORMS

This refers to the arrangement of the fibers of the muscles

with reference to the tendons to which they are attached.

(1) parallel

(a) Quadrilateral muscles: the fibers run directly from

their origin to their insertion such as the Thyrohyoid.

(2) Triangular The fibers are convergent; arising by a broad origin, they converge to a narrow or pointed insertion. e.g., the temporalis

(b) bipennate : where oblique fibers converge to both sides of a central tendon; an example is the Rectus femoris. (c) multipennate where oblique fibers converge to both sides of Multiple central tendons ; such as deltoid muscle. (d) circumpennate the fibers are arranged in a circum radial manner around the central tendon an example is flexor policis longus muscle.

(3) From their uses, as Flexors, Extensors, Abductors. (4) From their shape, as the Deltoideus, Rhomboideus. (5) From the number oftheir divisions, as the Biceps and Triceps. (6)From their points of attachment, as the sternocleidomastoideus, Sternohyoideus

Skeletal Muscle Action:

• Prime mover: A muscle is a prime mover when it is the chief

muscle or member of a chief group of muscles responsible

for a particular movement. For example, the quadriceps

femoris is a prime mover in the movement of extending the

knee joint.