Axial Muscles

Question 6: Identify Muscle

Naming of Skeletal Muscle

What are the six criteria listed by McKinley and O’Loughlin for the naming of muscles? Action Region Attachment Orientation (of fibers) Shape and Size Head # (tendons of origin)

Axial muscles have both their origins and insertions on parts of the axial skeleton.

Appendicular muscles control the movements of the upper and lower limbs and stabilize and control the movements of the pectoral and pelvic girdles.

A very good study technique is to learn all of the required muscles by palpating them on your own body and visualizing their origins, insertions, and actions.

The epicranius consists of the occipitofrontalis muscle, which has two bellies separated by a broad epicranial aponeurosis called the galea aponeurotica.

The frontal belly of the occipitofrontalis muscle originates on the frontal bone and skin of eyebrows and inserts on the galea aponeurotica. When it contracts it wrinkles the forehead and elevates the eyebrows.

The occipital belly of the occipitofrontalis muscle originates on the superior nuchal line of the occipital bone and inserts onto the galea aponeurotica. When it contracts it moves the scalp slightly posterior (backwards)

When the occipital belly of the occipitofrontalis muscle contracts it moves the scalp slightly posterior.

Obicularis oris muscle consists of muscle fibers that encircle the opening of the mouth. It originates from fascia and fibers overlaying the mandible and maxillae and inserts into the skin and lips surrounding the mouth.

The platysma muscle originates from fascia of the deltoid and pectoralis major muscles and the acromion of the scapula. It inserts into the skin of the cheek and mandible.

The broad platysma muscles stretching the skin of the neck. Its action is to pull the lower lip inferiorly, tense skin of neck, and depress the mandible.

The buccinator muscle is located between the maxillae and the mandible and composes much of the fleshy wall of the cheek.

The buccinator (trumpeter) muscle in action

Read about Bell palsy in the clinical view in your text.

WHICH OF THE FOLLOWING IS NOT USED BY A CHILD IN ORDER TO HOLD A STRAW IN ITS MOUTH AND SUCK UP JUICE THROUGH THE STRAW?

A PLATYSMA

B BUCCINATOR

C OBICULARIS ORIS

D MASSETER

E DIAPHRAGM

Read about the extrinsic muscles of the eye for your own information. We may revisit these with cranial nerves.

Read the clinical view in your text about strabismus

Muscles of mastication

The term mastication refers to the process of chewing and is accomplished by muscles that move the mandible at the temporomandibular joint (TMJ).

The temporalis muscle passes deep to the zygomatic arch and inserts on the coronoid process of the mandible. Its action is to elevate the mandible (close the mouth)

The temporalis muscle originates on the superior and inferior portions of the temporal bone and inserts on the coronoid process of the mandible. When it contracts it elevates and retracts the mandible.

The masseter muscle, which is synergistic to the temporalis, extends from the zygomatic arch to the lateral surface of the coronoid process and the lateral ramus of the mandible. It elevates and protracts the mandible (closes the mouth).

The medial and lateral pterygoid muscles, elevate the mandible, protract the mandible, and move it side to side in a chewing motion.

Pterygoid is Greek for “wing-shaped”.

The pterygoid muscles, along with the masseter, temporalis, and platysma muscles, are the muscles used in chewing (mastication).

Endospore

Lockjaw in tetanus Opisthotonos in tetanus

Read clinical view in text about tetanus and botulism

ACCORDING TO THE CLINICAL VIEW IN YOUR TEXT, WHERE IS BOTULISM TOXIN COMMONLY USED FOR COSMETIC PURPOSES?

A IN PECTORALIS MAJOR MUSCLES TO IMPROVE CHEST SIZE

B IN GLUTEUS MAXIMUS TO REDUCE STRESS AND CLINCHING

C IN EPICRANIUS REGION

D BELOW UMBILICUS TO IMPROVE POSTURE

E IN ORBICULARIS MUSCLE TO PLUMP LIPS

Muscles of the neck

Read about the muscles that move the tongue, the muscles of the pharynx, and the muscles of the anterior neck for your own information if you desire. We do not have time to discuss them in this class.

The sternocleidomastoid muscles have their origin distally on the manubrium and clavicle and their insertion on the mastoid process of the temporal bone. Their action is to turn the head sideways in a direction opposite the side on which the contracting muscle is located.

James Mason

Ava Gardner as Pandora

Note magnificent sternocleidomastoids and suprasternal fossa!

Note external jugular vein is superficial to sternocleidomastoid

The splenius capitus, the semispinalis capitis, and the trapezius (which will be discussed later) extend the head or hyperextend the neck.

The splenius capitis and the semispinalis capitis (along with the trapezius) extend the head and can hyperextend the neck.

Neck extensors/hyperextensors at work

The erector spinae muscles provide support and movement to the vertebral column and torso to resist gravity. Therefore, this group of muscles is stronger than the antagonistic rectus abdominis muscle.

Hyperextending the spine during exercises can strengthen the erector spinae muscles and the transversospinalis muscles (which are deeper) so they can better stabilize the vertebrae and resist back injuries.

Muscles of Respiration

Inhalation relies upon muscles to increase the dimensions of the thoracic cavity.

Exhalation is normally passive and decreases the chest dimensions.

The external intercostals are used in restful breathing. They cause the ribs to move up and out during inhalation thereby increasing the dimensions of the thoracic cavity. Air is pulled in by a partial vacuum.

“bucket handle” movement of the ribs during inhalation and exhalation.

The internal intercostals, which are deep to the external intercostals, draw the ribs together and depress the thorax, thereby diminishing the chest volume during forced exhalation. Forced exhalation may also involve the abdominal muscles.

Internal intercostal muscles and abdominal muscles at work during forced exhalation during exercise.

The diaphragm, which is skeletal muscle attached to the xiphoid process, the costal cartilages of the lower ribs, and the lumbar vertebrae, is dome-shaped and extends superiorly when relaxed and flattens out when contracted.

The diaphragm inserts on the central tendon, which is pulled inferiorly when the diaphragm is contracted during inhalation.

Movements of the diaphragm during muscular inhalation and during relaxed exhalation

During restful inhalation the external intercostal muscles pivot the ribs up and out to increase the dimensions of the thoracic cavity. During this same time period the diaphragm moves downward and flattens.

During restful exhalation the elastic recoil of the lung tissue pulls the ribs down and in and the diaphragm up (becomes dome-shaped) and the internal intercostals are NOT used. However, during forced exhalation the internal intercostals are used and perhaps the abdominal muscles as well!

Fracture/dislocation between C2 and C3 resulted in respirator-dependent quadriplegia. This patient cannot utilize his intercostal muscles nor his diaphragm. Read the clinical view

WHICH OF THE FOLLOWING IS MOST ASSOCIATED WITH EXHALATION?

A FLATTENING OF THE DIAPHRAGM

B NEGATIVE PRESSURE IN THE LUNG SPACES

C CONTRACTION OF EXTERNAL INTERCOSTALS

D INCREASED DIMENSIONS OF THE THORACIC CAVITY

E PULMONARY ELASTICITY

There are 4 pairs of flat, sheet-like muscles in the abdominal wall. Down the midline there is the linea alba while laterally there is the linea semilunaris. Both of these are bands of connective tissue.

Linea alba

Umbilicus

Iliac crest

Serratus anterior muscle

The linea alba is a midline fusion of the abdominal sheaths (aponeuroses). It visibly divides the rectus abdominis muscle. Note that the rectus abdominis muscle is transected by several tendinous intersections which give it a washboard or six-pack appearance in muscular individuals.

Note inguinal ligament

• Uncle Jeb was known for his 12 pack.

Inguinal hernia

Read about hernias in the clinical view in your text.

Note rectus abdominis linea alba and tedinous intersections

Tendinous intersections

Linea alba

Linea alba Linea semilunaris

When it comes time to enter the abdominopelvic cavity surgically, and to minimize damage to abdominal muscles, the linea alba and linea semilunaris are typically selected as entry points. I have noticed this particularly when laproscopic surgery is being performed with specialized tools and fiberoptic cameras.

This type of abdominal exercise primarily strengthens the rectus abdominis muscle.

To strengthen the rectus abdominis muscle, and the other abdominal muscles as well, incorporate lateral twisting to touch olecranon process to distal femoral condyles in an alternating rhythm.

Superior view looking down into female pelvic cavity

The floor of the pelvic cavity is formed by three layers of muscles and associated fasciae, collectively known as the pelvic diaphragm. These muscles collectively form the pelvic floor.

Inferior view of male perineum (note total diamond-shaped area)

Urogenital triangle

Anal triangle

The levator ani is actually a group of muscles which supports the pelvic viscera and functions as a sphincter for the anus, urethra, and vagina in females

Inferior view of female perineum (note total diamond-shaped area)

Urogenital triangle

Anal triangle

One of the muscles that contributes to the levator ani is the pubococcygeus. It was made famous by Dr. Arnold Kegel who advocated exercises to strengthen this muscle (Kegel exercises)

Super Kegal or Kegal Master?

Superior view looking down into female pelvic cavity

The pubococcygeus muscle, which is one of the three levator ani muscles, is strengthened with Kegel exercises to control urinary incontinence (by compressing the urethra) and to compress the vagina to aid in sexual enjoyment during coitus (sexual intercourse).

Read about how an episiotomy is performed on women as the fetus is bulging out of the vaginal opening during parturition in the clinical view in your text.

I just can’t wait to learn about appendicular muscles!

• EVERYTHING PAST THIS POINT IS EXTRA OR FOR EXAMS

Obicularis oris muscle in action

Olympian Misty May

Olympian Misty May

Figure 11.01b

Figure 11.co

The frontalis muscle elevates the eyebrow and wrinkles the forehead

The occipitalis muscle moves the scalp backwards

Figure 11.02ab

Figure 11.02bb

Figure 11.02ba

Figure 11.05b

Before Botox

After Botox

Figure 11.04a

Figure 11.04b

Figure 11.04d

Read Case Study about disease involving the sternocleidomastoids.

Figure 11.09

Figure 11.10a

The erctor spinae muscles, which actually are a collection of back muscles, synergistically extend the spine.

Figure 11.13a

Figure 11.13b

Figure 11.13c

Figure 11.14c

Figure 11.14b

Figure 11.03a

Figure 11.03a

Figure 11.03b

Figure 11.08b

Figure 11.10b

Figure 11.11b

Figure 11.15cb

Figure 11.15bb