9.5: Activity 4

List of Skeletal Muscles for Identification

To effectively study the human body in a laboratory setting, it’s essential to have a solid grasp of the major skeletal muscles, as they play crucial roles in movement, stability, and overall function.

Below is a structured overview of the selected muscle groups:

1. Muscles That Move the Lower Jaw (Mastication) - These muscles are responsible for chewing and include:

• Masseter: Elevates the mandible (jaw).
• Temporalis: Assists in closing the jaw and retracting it.

2. Muscles That Move and Stabilize the Head - These muscles help maintain head posture and facilitate movement:

• Sternocleidomastoid: Rotates and flexes the neck.
• Trapezius: Elevates, retracts, and rotates the scapula, also stabilizing the head.

3. Muscles That Position the Pectoral Girdle (stabilize and move the shoulders):

• Pectoralis Major: Helps in flexing and adducting the arm.
• Serratus Anterior: Protracts and stabilizes the scapula.

4. Muscles of the Back (Key for posture and movement):

• Latissimus Dorsi: Extends, adducts, and rotates the arm.
• Rhomboids: Retracts the scapula, helping with shoulder stability.

5. Abdominal Wall Muscles (support for the trunk):

• Rectus Abdominis: Flexes the vertebral column.
• External and Internal Obliques: Rotate and flex the torso.

6. Muscles involved in breathing (ventilation):

• Diaphragm
• External intercostals
• External intercostals

7. Muscles That Move the Humerus (vital for arm movement):

• Deltoid: Abducts the arm.
• Rotator Cuff Muscles: Stabilize the shoulder joint and allow for a wide range of motion.
• Four muscles (SITS): Supraspinatus, Infraspinatus, Teres minor, Subscapularis

8. Muscles of the upper limb (movements of the elbow, wrist and fingers):

• Biceps Brachii: Located in the front of the upper arm, this muscle flexes (bends) the elbow and also helps to supinate the forearm (turn the palm up).
• Brachialis: A deep muscle under the biceps that also flexes the elbow.
• Triceps Brachii: Located on the back of the upper arm, it extends (straightens) the elbow.
• Brachioradialis: Originates on the humerus and inserts on the radius; it's a primary elbow flexor, especially when the forearm is half-pronated.
• Flexor Carpi Radialis: Flexes and radially deviates (abducts) the wrist.
• Flexor Carpi Ulnaris: Flexes and ulnarly deviates (adducts) the wrist.
• Palmaris Longus: A superficial muscle that weakly flexes the wrist.
• Extensor Carpi Radialis Longus: Extends and abducts the wrist.
• Extensor Carpi Ulnaris: Extends and adducts (ulnar deviates) the wrist.
• Extensor Digitorum: Extends the fingers.

9. Gluteal Region Muscles That Move the Thigh (essential for hip movement):

• Gluteus Maximus: Extends and laterally rotates the thigh.
• Gluteus Medius and Minimus: Abduct the thigh and stabilize the pelvis.
• Quadriceps group: Extends leg at the knee joint
  • Rectus femoris: A straight muscle that extends from the pelvis to the patella.
  • Vastus lateralis: A large muscle on the outer side of the thigh.
  • Vastus medialis: A large muscle on the inner side of the thigh.
  • Vastus intermedius: A deep muscle located between the rectus femoris and vastus lateralis.
• Hamstring group: Flexes leg at the knee joint
  • Semitendinosus: Originates from the ischial tuberosity and inserts into the medial side of the upper tibia.
  • Semimembranosus:.Originates from the ischial tuberosity and inserts into the posterior medial side of the upper tibia.
  • Biceps femoris:. Has two heads (long and short) that originate from the ischial tuberosity and insert into the lateral side of the upper tibia (long head) and the head of the fibula (short head).

10. Muscles of the Lower Leg (facilitate movement of the ankle and foot):

• Gastrocnemius: Plantar flexes the foot and flexes the knee.
• Soleus: Plantar flexes foot.
• Tibialis Anterior: Dorsiflexes the foot.

Understanding these muscle groups will enhance your comprehension of human anatomy and physiology, crucial for effectively conducting laboratory work.
Note - Mnemonics help students remember origins, insertions, or actions. For example:

• For rotator cuff muscles: SITS (Supraspinatus, Infraspinatus, Teres Minor, Subscapularis).
• Muscles involved in elbow flexion: “Three Bs Bend the Elbow” : Biceps brachii, Brachialis, Brachioradialis

For an effective in-person lab activity focused on identifying skeletal muscles, students can showcase their work. Each group can capture photographs of laboratory models, with muscles clearly labeled using blue tape. This visual documentation should cover at least two anatomical regions, such as the upper limb, lower limb, or posterior torso. However, all students are responsible for all the selected muscles.

• Label Clearly: Use blue tape to label each muscle on the model, ensuring the text is legible in photographs.
• Capture Quality Photos: Ensure good lighting and focus in photographs to clearly show the labeled muscles and their placements.
• Organize and Submit: Compile the images into a digital format for easy submission and review by instructors.

Instructions

• The list of selected skeletal muscles is provided, each group will be assigned a set of tables to research and complete required information.
  • Muscle Name: The name of the muscle.
  • Origin: Where the muscle begins, typically the stationary bone.
  • Insertion: Where the muscle attaches to the bone that moves.
  • Action: The primary movement the muscle performs when it contracts.
• Students will work collaboratively, discussing their findings and ensuring accuracy.
• Once the tables are completed, one group will pair up with another group to review each other’s work.
• Each pair should check for accuracy and clarity, providing constructive feedback.
• Class Discussion
  • Which muscle was the most interesting to research?
  • How do the origins and insertions relate to muscle actions?