5C Axial Muscles anatomy PDF

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AXIAL MUSCLES Laboratory V: Component C Objective •

Identify various muscles as belonging to the axial or appendicular region of the body.

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Identify each muscle by name or image, and give its action.

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In addition to identification and action, know the exact bony origin/insertions for the muscles marks “O/I” on the terms list.

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Review muscle actions, and understand which muscles contribute to specific bodily movements.

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Apply the knowledge from the skeleton units to the muscles unit.

Note: Please be advised that there is a Connect assignment due for this unit. If feel you need to review the general muscles terms, please see the video on Canvas from the general muscles unit.

Introduction During the skeletal unit, there was a clear distinction which bones belonged to the axial skeleton or the appendicular skeleton. However, muscles can be extrinsic, meaning that they may have an origin in one region, but produce an action in another. For our purposes, we will classify muscles based on the action(s) that they perform. In this unit, there are additional learning tools for you to utilize. The muscles unit will heavily utilize Anatomy & Physiology Revealed (APR) and cadavers, in addition to models and images from the textbook. Furthermore, you are already familiar with “common terms” for muscle movements, and when learning the muscles and muscle movements, you are encouraged to perform muscle actions, and palpate the muscles performing those actions. Finally, do not forget to utilize the materials from the skeleton unit. When trying to learn origins/insertions, or understand how a specific muscle action is performed, the skeleton will be a vital tool in understanding these concepts. Note: While all of the muscles presented here include the origin and insertion, you are only responsible for knowing the origins and insertions of the muscles marked “O/I” on your terms list. All of the origins and insertions have been included here to provide a better understanding of the muscle’s location.

Muscles of the Head and Neck The muscles of the head support several main functions. They are involved in facial expression, moving the jaw for chewing and talking, and moving the eyeballs for sight. The muscles of facial expression are unique because they insert into the skin or the fascia of other muscles instead of bones. Therefore, they move the skin of the face to enable you to smile, frown, glare, etc. The muscles that move the jaw are attached from bone to bone, providing greater leverage and power. The muscles moving the eyeballs include six extrinsic (located outside of the eyeball) muscles that extend from the inside of the orbit to each eyeball. Although the extrinsic eye muscles are skeletal muscles, they will be studied with the remainder of the eye anatomy, which is covered in Laboratory 7: The Special Senses.

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Many of the muscles of the neck move the head, while others are attached to the hyoid bone to move the throat or tongue for swallowing. The muscles moving the head are quite large, and are mainly lateral or posterior. The muscles associated with the hyoid bone are small anterior muscles.

Muscles of Facial Expression Table 5C.1 Muscles of Facial Expression O: Origin Action

Muscle I: Insertion

Orbicularis oculi

O: Lacrimal bone; adjacent regions of frontal bone and maxilla; medial angle of upper eyelids. I: Upper and lower eyelids; skin around margin of orbit.

Levator palpebrae superioris

O: Lesser wing of sphenoid in posterior wall of orbit.

Sphincter of the eyelids; closes eye in blinking, squinting, and sleep; aids in flow of tears across eye.

Elevates upper eyelid; opens eye.

I: Upper eyelid. O: Modiolus (corner) of mouth Orbicularis oris I: Submucosa and dermis of lips. O: Zygomatic bone. Zygomaticus major I: Superolateral angle of mouth. O: Zygomatic bone. Zygomaticus minor I: muscles of upper lip. O: Fascia of deltoid and pectoralis major. Platysma I: Mandible; skin and subcutaneous tissue of lower face.

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Encircles mouth, closes lips, protrudes lips as in kissing; uniquely developed in humans for speech. Draws angle of mouth upward and laterally in laughing.

Elevates upper lip, exposes upper teeth in smiling or sneering.

Draws lower lip and angle of mouth downward in expressions of horror or surprise; may aid in opening mouth widely.

Figure 5C.1 Muscles of Facial Expression

Images from: Anatomy & Physiology: The Unity of Form and Function by McGraw-Hill Education

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Muscles of Chewing and Swallowing Table 5C.2 Muscles of Mastication

O: Origin Muscle

Action I: Insertion O: Temporal lines and temporal fossa of cranium.

Temporalis I: Coronoid process and anterior border of mandibular ramus. O: Zygomatic arch. Masseter

Digastric

I: Lateral surface of mandibular ramus and angle. O: Mastoid notch of temporal bone; digastric fossa of mandible. I: Hyoid bone via fascial sling. O: Mylohyoid line near inferior margin.

Mylohyoid I: Hyoid bone. O: Styloid process of temporal bone. Stylohyoid I: Hyoid bone.

Elevation, retraction, and lateral and medial excursion of the mandible.

Elevation of the mandible, with smaller roles in protraction, retraction, and lateral and medial excursion. Depresses mandible when hyoid is fixed; opens mouth widely, as when ingesting food or yawning; elevates hyoid when mandible is fixed. Spans mandible from side to side and forms floor of mouth; elevates floor of mouth in initial stage of swallowing. Elevates and retracts hyoid, elongating floor of mouth; roles in speech, chewing, and swallowing are not yet clearly understood.

O: Superior border of scapula. Omohyoid

Depresses hyoid after it has been elevated. I: Hyoid bone.

Sternohyoid

O: Manubrium of sternum; medial end of clavicle.

Depresses hyoid after it has been elevated.

I: Hyoid bone. O: Thyroid cartilage of larynx. Thyrohyoid I: Hyoid bone. O: Manubrium of sternum; costal cartilage. Sternothyroid I: Thyroid cartilage of larynx.

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Depresses hyoid; with hyoid fixed, elevates larynx as in singing high notes. Depresses larynx after it has been elevated in swallowing and vocalization; aids in singing low notes.

Figure 5C.2 Muscles of Chewing and Swallowing

Images from: Anatomy & Physiology: The Unity of Form and Function by McGraw-Hill Education

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Muscles Acting on the Head Table 5C.3 Muscles Acting on the Head

Muscle

Sternocleidomastoid

Anterior, Middle, and Posterior Scalenes

O: Origin I: Insertion

O: Manubrium of sternum; medial onethird of clavicle. I: Mastoid process; lateral half of superior nuchal line.

O: Transverse processes of all cervical vertebrae (C1-C7). I: Ribs 1-2.

Unilateral action tilts head slightly upward and toward the opposite side, as in looking over one’s contralateral shoulder. The most common action is probably rotating the head to the left or right. Bilateral action draws the head straight forward and down, as when eating or reading. Aids in deep breathing when head is fixed. Unilateral contraction causes ipsilateral flexion or contralateral rotation (tilts head toward same shoulder, or rotates face away), depending on action of other muscles. Bilateral contraction flexes neck. If spine is fixed, scalenes elevate ribs 1-2 and aid in breathing.

Trapezius

O: External occipital protuberance; medial one-third of superior nuchal line; nuchal ligament; spinous processes of vertebrae C7-T3 or T4. I: Acromion and spine of scapula; lateral one-third of clavicle.

Extends and laterally flexes neck. Also has role in scapular movement.

Splenius Capitis and Splenius Cervicis

O: Inferior half of nuchal ligament; spinous processes of vertebrae C7-T6. I: Mastoid process and occipital bone just inferior to superior nuchal line; cervical vertebrae C1-C2 or C3.

Acting unilaterally, produce ipsilateral flexion and slight rotation of head; extend head when acting bilaterally.

Figure 5C.3 Muscles of Acting on the Head Image from: Anatomy & Physiology: The Unity of Form and Function by McGraw-Hill Education

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Action

Muscles of Respiration The muscles of respiration are used to draw air into and force air out of the lungs. Along with the bones of the thorax, these muscles help form the thoracic cavity and include the diaphragm, external intercostal muscles, and internal intercostal muscles. The diaphragm is the dome-shaped muscle that divides the thoracic body cavity from the abdominopelvic cavity. The diaphragm muscle is the prime mover of inspiration. When contracting, the diaphragm flattens causing an increase in size of the thoracic cavity. This simultaneously lowers pressure in the lungs, and helps draw air into the lungs. During expiration, the diaphragm relaxing and returns to its dome-like state. This shrinks the size of the thoracic cavity and forces air out of the lungs. The 11 pairs of external intercostal muscles work in conjunction with the diaphragm during inspiration. As their name would imply, these muscles can be found between the ribs. Each external intercostal muscle originates on the lower margin of the superior rib, and inserts onto the upper margin of the inferior rib. When contracting, the external intercostals will pull up on the rib below them, helping to increase the size of the thoracic cavity --much like a handle swinging upward on a bucket. During expiration, the external intercostal muscles relax allowing the thoracic cavity to return to its resting size and forcing air out of the lungs. The 11 pairs of internal intercostal muscles also play a crucial role in ventilation. The intercartilaginous part (found between the costal cartilage) aids the external intercostal muscles in elevating the ribs, and therefore assists in the expansion of the thoracic cavity. However, during forced expiration the interosseous part (found between the bones) depresses the ribs and compresses the thoracic cavity.

Table 5C.4 Muscles Respiration O: Origin

Muscle

Diaphragm

Action I: Insertion

O: Xiphoid process of sternum; ribs and costal cartilages 7-12; lumbar vertebrae. I: Central tendon of diaphragm.

External Intercostals

Internal Intercostals

O: Inferior margins of ribs 1-11. I: Superior margin of next lower rib.

O: Superior margins and costal cartilages of ribs 2-12; margin of sternum. I: Inferior margin of next higher rib.

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Prime mover of inspiration (responsible for about two-thirds of air intake); contracts in preparation for sneezing, coughing, crying, laughing, and weight lifting; contraction compresses abdominal viscera and aids in childbirth and expulsion of urine and feces. When scalenes fix rib 1, external intercostals elevate and protract ribs 2-12, expanding the thoracic cavity and creating a partial vacuum causing inflow of air. In inspiration, the intercartilaginous part aids in elevating the ribs and expanding the thoracic cavity; in expiration, the interosseous part depresses and retracts the ribs, compressing the thoracic cavity and expelling air; the latter occurs only in forceful expiration, not in relaxed breathing.

Figure 5C.4 The Muscles of Respiration

Muscles of the Anterior Abdominal Wall The muscles of the anterior abdominal wall support the abdominal viscera, as the abdominal cavity has little to no bony support. This muscle group is made up of four muscles, each of which have fibers running in different directions. These muscles include rectus abdominis, the external abdominal oblique, the internal abdominal oblique, and the transverse abdominis muscle. Rectus abdominis, commonly known as the “six-pack”, runs from sternum to pubis. It’s fibers run superiorly and inferiorly, and is intersected by various tendinous structures. Along the midline, a tendinous structure known as the linea alba bisects the rectus abdominis muscle. Several tendinous intersections running transversely through the rectus abdominis, giving it its six-pack appearance. From superficial to deep, the remainder of the anterior abdominal muscles are as follows: the external abdominal oblique, the internal abdominal oblique, and the transverse abdominis. The external abdominal oblique muscle fibers run down and towards the midline. The internal abdominal oblique muscle has fibers that run up and towards the midline. Finally, the transverse abdominis muscle has fibers that run across the body towards the midline.

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Table 5C.5 Muscles of the Anterior Abdominal Wall

Muscle Rectus Abdominis

External Abdominal Oblique

Internal Abdominal Oblique

Transverse Abdominis

O: Origin I: Insertion

Action

O: Pubic symphysis and superior margin of pubis. I: Xiphoid process; costal cartilages 5-7.

Flexes waist, as in bending forward or doing sit-ups; stabilizes pelvic region during walking; and compresses abdominal viscera.

O: Ribs 5-12. I: Anterior half of iliac crest; symphysis and superior margin of pubis.

Supports abdominal viscera against pull of gravity; stabilizes vertebral column during heavy lifting; maintains posture; compresses abdominal organs, thus aiding in deep breathing, loud vocalizations such as singing and public speaking, and in expulsion of abdominopelvic contents during childbirth, urination, defecation, and vomiting; unilateral contraction causes contralateral rotation of the spine, as in twisting at the waist.

O: Inguinal ligament; iliac crest; thoracolumbar fascia. I: Ribs 10-12; costal cartilages 7-10; pubis. O: Inguinal ligament; iliac crest; thoracolumbar fascia; costal cartilages 7-12. I: Linea alba; pubis; aponeurosis of internal oblique.

Same as external oblique except that unilateral contraction causes ipsilateral rotation of waist.

Compresses abdominal contents, with same effects as external oblique, but does not contribute to movements of vertebral column.

Figure 5C.5A Muscles of the Anterior Abdominal Wall

Image from: Anatomy & Physiology: The Unity of Form and Function by McGraw-Hill Education

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Figure 5C.5A Muscles of the Anterior Abdominal Wall

Image from: Anatomy & Physiology: The Unity of Form and Function by McGraw-Hill Education

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Muscles of the Back The muscles of the back perform a variety of functions include supporting the trunk and keeping it erect, lateral flexion of the trunk, and rotation. One key muscle involved in these actions is the erector spinae muscle, which is composed of three columns from lateral to medial: the iliocostalis, longissimus, and spinalis. The erector spinae muscle is composed of the aforementioned columns, and run from the cranium to the sacrum. While one of the deeper muscles of the back, the erector spinae can be easily palpated along the vertebral column.

Table 5C.6 Muscles of the Back

Muscle

O: Origin I: Insertion

Action

Erector Spinae

O: Nuchal ligament; ribs 3-12; thoracic and lumbar vertebrae; median and lateral sacral crests; thoracolumbar fascia. I: Mastoid process; cervical and thoracic vertebrae; all ribs.

Aids in sitting and standing erect; straightens back after one bends at waist, and is employed in arching the back; unilateral contraction flexes waist laterally; the longissimus capitis also produces ipsilateral rotation of the head.

O: Transverse processes of C7-T6. I: Occipital bone.

Unilateral flexion results in rotation of head to opposite side; bilateral action results in extension of head and neck.

Iliocostalis part of erector spinae

O: Sacrum and ribs. I: Ribs and transverse processes of cervical vertebrae.

Unilateral action results in lateral flexion of vertebral column; bilateral action results in extension of vertebral column; depresses ribs.

Longissimus part of erector spinae

O: Iliac crest; dorsal sacrum; sacral and lumbar spinous processes. I: Transverse processes (cervical and thoracic), ribs, and mastoid process.

Unilateral action results in lateral flexion of vertebral column and rotation of head to same side; bilateral action results in extension of vertebral column and head; depresses ribs.

Spinalis part of erector spinae

O: Spinous processes and nuchal ligament. I: Spinous processes (cervical and thoracic) and occipital bone.

Unilateral action results in lateral flexion of vertebral column; bilateral action results in extension of vertebral column.

Semispinalis Capitis

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Figure 5C.5 Muscles of the Anterior Abdominal Wall

Images from: Anatomy & Physiology: The Unity of Form and Function by McGraw-Hill Education

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LABORATORY V: COMPONENT C – WORKSHEET Short Answers:

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1.

Identify the muscles involved in respiration (inspiration/expiration). Briefly note their role when they contract and who is the prime mover, synergist (to the prime mover), and antagonist (to the prime mover).

2.

Identify the rotator cuff muscles.

3.

Vanessa, a massage therapist, was giving Mr. Pitt a backrub. What two broad superficial muscles of the back were receiving the bulk of her attention?

4.

What muscles flex the neck? Identify the prime mover. Hint: one paired muscle pulls the head straight down when bilaterally contracted.

Use your lab manual figures and models to locate each muscle given below. Then write the characteristic(s) used in its naming. Since many muscles have more than one word in their names, some have more than one answer. A list of useful Greek and Latin terms is also given. Rectus femoris _________________________________________________________________________________ Thyrohyoid ____________________________________________________________________________________ Adductor longus ________________________________________________________________________________ Triceps brachii _________________________________________________________________________________ Pronator teres _________________________________________________________________________________ External oblique _______________________________________________________________________________ Piriformis _____________________________________________________________________________________ Brachioradialis _________________________________________________________________________________ Extensor carpi ulnaris ___________________________________________________________________________ Pectoralis major ________________________________________________________________________________ Biceps femoris _________________________________________________________________________________ Occipitalis ____________________________________________________________________________________ Trapezius _____________________________________________________________________________________ Rhomboid minor _______________________________________________________________________________ Fibularis brevis ________________________________________________________________________________

Greek and Latin Terms used in Naming Muscles

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Abdominis = abdomen

Bi=two

Brachium= arm