Exercise 7: Axial Muscular System

Figure 7.1. Muscles of the head and neck drawn to show their relative positions and muscle fiber orientation.

Exercise 7 Learning Goals 

After completing this lab, students should be able to: 

• Describe and define the origin, insertion, and action of select muscles:
  • Involved in facial expression
  • Muscles that move the eye
  • Muscles of mastication
  • Muscles that move the head
  • Muscles of the abdomen
  • Muscles involved in breathing

Pre-Lab Activities for Exercise 7

Pre-Lab Activity 7.1: Muscle names their & Origin, Insertion and Action (O.I.A.)

Before lab begins, please make sure you research and write down the origins, insertions and actions for the muscles listed in the table below. Use the required textbook as a guide.

Exercise 7 Activities: The Axial Muscular System

There are over seven hundred different muscles associated with the human body. As we learned from the previous lab, skeletal muscle contractions cause the muscle to shorten. This shortening leads to movement of the skeleton. Movement of bones can only take place at joints. Therefore, each muscle always crosses a joint and attaches to the bones that form the joint. Each muscle has an origin attachment and an insertion attachment. The origin is where a muscle attaches to the stationary bone during an action and the insertion is where a muscle attaches to the bone that moves during action. The action of a muscle is a particular movement of the skeleton when the muscle has contracted. Therefore, by looking at the origin and insertion of each muscle, we can infer the action of the muscle.

Lab Activity 7.1: Naming of Skeletal Muscles

There are several ways to determine names of muscles. In general, muscles are named by one or more of the following criteria:

1. Shape of muscle
2. Size of the muscle compared to other muscles in the area (relative size)
3. Location of muscle in the body
4. Location of muscle’s origins and insertions
5. Number of origins
6. Principal action of the muscle
7. Direction of the fascicles

Using Figure 7.2, the anatomical models in lab, and/or your textbook, give an example of two muscles named based on the following criteria for each category.

1. Shape of muscle:
2. Size of the muscle compared to other muscles in the area (relative size):
3. Location of muscle in the body:
4. Location of muscle’s origin and insertion:
5. Number of muscle origins:
6. Principal action of the muscle:
7. Direction of the muscle’s fibers:

Figure 7.2 Overview of anterior and posterior muscles.

Activity 7.2: Origins, Insertions, Actions and Fascicular arrangements of axial muscles

For each of the following groups of muscles, use the anatomical models in the lab and the figures in this chapter to exam the individual muscle’s origins, insertions, and fascicle arrangement. Fill out the table after completing your examination of the anatomical models and figures.

Muscles of facial expression

The origins of the muscles of facial expression are on the surface of the skull (remember, the origin of a muscle does not move). The insertions of these muscles are connected to the dermis of the skin. Because the muscles insert in skin rather than bone, when they contract, the skin moves to create facial expression.

Figure 7.3 Muscles of Facial Expression

Complete the table for Facial Muscles

Anatomy in Clay® Instructions

To demonstrate your understanding of origins, insertions, and fascicle arrangement of the muscles, you will use an oil-based clay to form select muscles on the Manikin®. Please follow the instructions below. If you are unsure of what to do, ask your instructor.

• Keep your space clean and organized.
• Keep track of your tools and supplies.
• Feel free to stand or sit when working on your model.
• Move your model around so it is easy to build on but be careful!
• Use dry paper towels to remove clay from hands and tools (DO NOT USE SOAP OR WATER).
• Use red/ terra cotta clay to build muscles.
• Always keep the clay on the green mats.

Clean Up at the end of lab period

1. Take all clay off the model!

2. Roll into balls NO BIGGER than image below and organize into plastic bags.

3. Use dry paper towels to wipe off as much clay as possible from the model and tools used.

4. Return your model to its original place.

Muscles that Move the Eye

It takes six extraocular muscles to create the fine tandem movements of the eyes. These muscles originate behind the eye and insert on the sclera (the white of the eye). Like the muscles of facial expression, the muscles that move the eye are a rare example of skeletal muscle inserting into non-bony attachments.

Figure 7.4: Muscles that Move the Eye

Complete the table for Eye Muscles

Muscles of Mastication

These muscles close the mandible. This movement is especially important when we chew food, hence the name muscles of mastication (chewing).

Figure 7.5 Muscles of Mastication

Complete the table for Muscles of Mastication

Muscles that Move the Head

The head pivots on the vertebral column and as such can flex, extend, and rotate. The head muscles perform flexion, extension and rotation depending on the contraction coordination. For example, if only one sternocleidomastoid contracts (unilaterally), the head will rotate but if both sternocleidomastoids contract (bilaterally), the head will flex.

Figure 7.6 Muscles that Move the Head

Activity 7.3: Anatomy in Clay® - Muscles that move the Head

On your model, place the sternocleidomastoid and semispinalis capitis muscles and include the fascicle orientation.

Muscles of the Anterior Abdominal Wall

These muscles are important to human locomotion as they stabilize our core, help with posture, and protect the abdominal organs. There are four pairs of abdominal muscles that cover the anterior and lateral abdominal region and meet at the midline of the body anteriorly. The muscles of the anterolateral abdominal wall can be divided into four groups: the external obliques, the internal obliques, the transversus abdominis, and the rectus abdominis.

Figure 7.7 Muscles of the Anterior Abdominal Wall

Activity 7.4: Anatomy in Clay® - Muscles of the Anterior Abdominal Wall

On your model, place the rectus abdominis and transverse abdominis muscles and include the fascicle orientation.

Diaphragm: the primary muscle of Breathing.

The volume and pressure within the thoracic cavity changes during breathing and is due to the alternating contraction and relaxation of the diaphragm. Additionally, it serves as a physical barrier between the thoracic and abdominal cavities. The superior surface of the diaphragm is convex, creating the elevated floor of the thoracic cavity. The inferior surface is concave, creating the curved roof of the abdominal cavity.

Figure 7.8 Muscles used in Breathing

Post-Lab 7 Review

Post Lab Activity 7.1: Identify the Axial muscle

On the diagram below identify the muscle using the appropriate letter.

1. Orbicularis oris
2. Orbicularis oculi
3. Frontalis
4. Occipitalis
5. Buccinator
6. Epicranial aponeurosis

Figure 7.9: Unlabeled facial muscles.

Post Lab Activity 7.2: Identify the Axial Muscle

On the diagram below identify the muscle using the appropriate letter.

1. Inferior oblique
2. Medial rectus
3. Superior oblique
4. Lateral rectus
5. Superior rectus
6. Inferior rectus

Figure 7.10: Unlabeled muscles of the eye.

Post Lab Activity 7.3: Identify the Axial Muscle

On the diagram below identify the muscle using the appropriate letter.

1. Lateral pterygoid
2. Medial pterygoid
3. Temporalis
4. Masseter

Figure 7.11: Unlabeled muscles of the jaw.

Post Lab Activity 7.4: Axial Muscle OIA

Match the axial muscle to its origin, insertion, or action