Anatomy of Human Muscles

Anatomy of Human Muscles

PURPOSE: To develop skill in identifying muscle names and locations relative to other regional structures. To determine origin, insertion and principle action of muscles through analysis of muscle location, shape and arrangement.

PROCEDURE

Skeletal muscles, mainly under voluntary control are the muscles of most interest in gross anatomy for many reasons (muscle building, body contouring, sports training to name a few). They are attached at each end ? either to bone or connective tissue ? mostly via tendons (cordlike dense regular connective tissue) and aponeuroses (wide thin tendons). The origin is the attachment to the stationary bone which serves as the stronghold. The insertion is the attachment to the movable bone where the force applied by muscle contraction causes a specific movement. Each muscle attachment is relative with respect to body movements. In two different muscles, these attachments may be reversed.

Muscle names are generally descriptive using one or more of seven criteria: 1. the location of the muscle 2. the relative size of the muscle 3. the shape of the muscle 4. the muscle origin and insertion 5. the direction of the muscle fascicles (bundles of muscle fibers), i.e. rectus (along a longitudinal axis), transverse (perpendicular to a longitudinal axis), oblique (across a longitudinal axis at an angle different than perpendicular) 6. the arrangement of fascicles within the muscle (pennate, orbicularis) 7. the principle action of the muscle

The action of a muscle is the movement caused by that muscles contraction. Generally the movements possible are the following (16 mostly paired opposites):

flexion or extension adduction or abduction medial rotation or lateral rotation supination or pronation inversion or eversion elevation or depression protrusion (protraction) or retrusion (retraction) opposition

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 circumduction Review these actions from your Anatomy 35 text and notes.

Using Gilroy's Atlas of Anatomy and Clemente's Anatomy Dissector as your 1st references, and your Anatomy 35 Human Anatomy text as your 2nd reference, you will describe the position of each muscle listed in the following tables relative to other regional structures. Other references will be available in the cadaver lab to assist you in this research. Each student will fill in the following characteristics found in the heading of each table: origin, insertion, (Principle) Action, and Primary Nerve. By following each muscle to its attachments on a prosected cadaver, you will also see the origin and insertion. The principle action of the muscle can be determined by looking at the position, shape, angle, and attachments. Verify all of your findings with your references. Students will also be expected to determine the major blood vessels supplying the muscles listed. Prompts for this information can be found following the data tables.

I. MUSCLES OF THE HEAD AND NECK

1. Muscles of Facial Expression

Muscle Occipitofrontalis (frontal belly)

Origin

Insertion

Action

Primary Nerve

Occipitofrontalis (occipital belly)

Orbicularis oculi Levator labii superioris Zygomaticus major/minor Buccinator Orbicularis oris Levator anguli oris Depressor anguli oris Depressor labii inferioris Mentalis Platysma

Risorius

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Describe the major blood vessels that both supply and drain the muscles described above. Details should at least include secondary branches from the aorta and major tributaries to the internal and/or external jugular vein.

2. Muscles of Mastication

Muscle Temporalis Masseter

Origin

Insertion

Action

Primary Nerve

3. Muscles of the Submandibular Region

Muscle Digastric ? anterior belly

Digastric ? posterior belly

Stylohyoid Mylohyoid Geniohyoid

Origin

Insertion

Action

Primary Nerve

Describe the major blood vessels that both supply and drain the muscles described above. Details should at least include secondary branches from the aorta and major tributaries to the internal and/or external jugular vein.

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4. Muscles of the Anterior Neck

Muscle Sternocleidomastoid Omohyoid (superior belly) Omohyoid (inferior belly) Sternohyoid

Origin

Insertion

Action

Primary Nerve

Sternothyroid

Thyrohyoid

NOTE: 1. The anterior triangle of the neck has several subdivisions. What are these subdivisions? Identify the muscles from the previous tables that are found in each of these subdivisions. What other important structures are found in these subdivisions?

Describe the major blood vessels that both supply and drain the muscles described above. Details should at least include secondary branches from the aorta and major tributaries to the internal and/or external jugular vein.

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II. Muscles of the Trunk

1. Muscles of the Thoracic Wall

Muscle Anterior Scalene Posterior Scalene Middle Scalene External intercostal Internal intercostal

Origin

Insertion

Action

Primary Nerve

Describe the major blood vessels that both supply and drain the muscles described above. Details should at least include secondary branches from the aorta and major tributaries to the azygous vein and/or superior vena cava.

2. Intrinsic Back Muscles

Muscle Splenius capitus Erector Spinae: a. Iliocostalis b. Longissimus c. Spinalis

Origin

Insertion

Action

Primary Nerve

NOTE: What are the 3 portions of the semispinalis muscle?

Describe the major blood vessels that both supply and drain the muscles described above. Details should at least include secondary branches from the aorta and major tributaries to the azygous vein.

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