Lab 7: Muscular System II – Forelimb and Axial Muscles
Lab 7: Muscular System II – Forelimb and Axial Muscles
Muscles of the forelimb, trunk, and head; Muscle groups
Learning Objectives
When you are prepared for the Test on Week 6-7 Learning Objectives in Week 8*, you will be able to:
- Identify components of a muscle cell and the neuromuscular junction.
- Identify connective tissues of muscles.
- Identify significant muscles on both human models and cats (listed in the lab activity).
- For the hamstrings, quadriceps and rotator cuff muscle groups: identify the muscles within them, the bony features that act as their attachment sites, and their general functions.
*Muscle dissections will span weeks 6-7. There will be no test in Week 7. In week 8, there will be a test covering all of the above learning objectives.
In last week’s lab, we looked at muscles of the hindlimb. In lab this week, we will look at the skeletal muscles in the forelimb, as well as in the axial region. By the end of these two weeks, you should have a broad understanding of the muscular system and be able to identify the major muscles in the body (Figure 7.1).
Muscles of the Forelimb
Muscles of the shoulder and upper limb can be divided into four groups: muscles that stabilize and position the shoulder girdle, muscles that move the arm, muscles that move the forearm, and muscles that move the wrists, hands, and fingers. The shoulder girdle consists of the lateral ends of the clavicle and scapula, along with the proximal end of the humerus, and the muscles covering these three bones to stabilize the shoulder joint. The girdle creates a base from which the head of the humerus, in its ball-and-socket joint with the glenoid fossa of the scapula, can move the arm in multiple directions.
Muscles That Position the Pectoral Girdle
Muscles that position the pectoral girdle are located either on the anterior thorax or on the posterior thorax (Figure 7.2 and Table 7.1). The anterior muscles include the subclavius, pectoralis minor, and serratus anterior. The posterior muscles include the trapezius, rhomboid major, and rhomboid minor. When the rhomboids are contracted, your scapula moves medially, which can pull the shoulder and upper limb posteriorly.
| Position in the thorax | Movement | Target | Target motion direction | Prime mover | Origin | Insertion |
|---|---|---|---|---|---|---|
| Anterior thorax | Stabilizes clavicle during movement by depressing it | Clavicle | Depression | Subclavius | First rib | Inferior surface of clavicle |
| Anterior thorax | Rotates shoulder anteriorly (throwing motion); assists with inhalation | Scapula; ribs | Scapula: depresses; ribs: elevates | Pectoralis minor | Anterior surfaces of certain ribs (2–4 or 3–5) | Coracoid process of scapula |
| Anterior thorax | Moves arm from side of body to front of body; assists with inhalation | Scapula; ribs | Scapula: protracts; ribs: elevates | Serratus anterior | Muscle slips from certain ribs (1–8 or 1–9) | Anterior surface of vertebral border of scapula |
| Poster