The Certified MA Guide - Musculoskeletal System

Musculoskeletal Anatomy and Physiology for Medical Assistants

The musculoskeletal system is a critical component of the human body, providing structure, protection, and movement. For medical assistants preparing for their certification exams, understanding the basics of anatomy and physiology related to this system is essential. This lesson will focus on the major bones and muscle groups relevant to the field, emphasizing their functions and clinical importance. That being said, this is also my personal favorite and in my opinion one of the easiest and most relatable sections to study. Throughout this section, you should be able to identify all the different structures presented on your person. My recommendation is to point or flex the structure being presented and get used to moving that part of the body when you see the term. It may seem foolish, but no one is watching while you study and if it helps to drill the terms in your head, then go for it! Also, I'll include a special Orthopedics Insider section at the end of this section to help you understand more about why this section is relevant to your work as a medical assistant and how awesome it can be to learn new information and correlate it to in-clinic knowledge. Now, let's dive in!

1. Overview of the Skeletal System

The skeletal system consists of 206 bones that are divided into two main categories: The Axial and Appendicular Skeleton

Exciting, right? Let's break it all down:

A. Axial Skeleton

Skull: Protects the brain and supports the facial features.
- Major bones: Frontal, Parietal, Temporal, Occipital, Sphenoid, Maxilla, Mandible.
Vertebral Column: Protects the spinal cord and provides structural support.
- Divisions: Cervical (7), Thoracic (12), Lumbar (5), Sacrum, Coccyx.
Rib Cage: Protects vital organs such as the heart and lungs.
- Includes: Sternum, True ribs (1-7), False ribs (8-12), Floating ribs (11-12).

B. Appendicular Skeleton - Think appendages / extremities

Upper Extremities:
- Clavicle (AKA Collar Bone), Scapula (AKA Shoulder Blade), Humerus, Radius, Ulna.
  1. The radius and ulna can be distinguished by their heads. The proxima head of the ulna has a C-shaped cup that fits on the olecranon process of the distal humerus and forms the elbow.

- Carpals (wrist bones), Metacarpals (palms), and Phalanges (fingers) for the wrist and hand.

Lower Extremities:
- Pelvis, Femur, Patella, Tibia, Fibula.
- Tarsals, Metatarsals, and Phalanges for the ankle and foot.
  1. Think back to the wrist anatomy, the carpals, metacarpals, and phalanges. It's the same concept with the feet but instead of the term "carpal" we use "tarsal" for foot.

C. Bone Functions

Provide support and structure for the body.
Protection of the internal organs, such as the case with the ribs.
They help to provide movement in conjunction with muscles.
Production of blood cells (hematopoiesis) performed in the bone marrow.
Storage of minerals (e.g., calcium, phosphate).

2. Major Muscle Groups and Their Clinical Relevance

Medical assistants should focus on the larger, more clinically significant muscle groups. These muscles are often used as landmarks for injections or assessed for strength during physical exams. Thankfully, MAs don't have to memorize every muscle in the body and go in the depth that medical students or PA students do, but we should certainly strive to know the major ones as it will become relevant should you do any work in the fields of orthopedics, physical medicine and rehabilitation, physical therapy, etc.

A. Upper Body Muscles

Deltoid

- Location: Shoulder.
- Function: Arm abduction.
- Clinical relevance: Common site for intramuscular (IM) injections.

Pectoralis Major

- Location: Chest.
- Function: Arm flexion and adduction.
- Clinical relevance: Important for chest compressions during CPR.

Trapezius

Location: Upper back and neck.
Function: Moves the scapula and supports neck extension.

Biceps Brachii

Location: Anterior upper arm.
Function: Elbow flexion.

Triceps Brachii

Location: Posterior upper arm.

Function: Elbow extension.

B. Core Muscles

Rectus Abdominis

- Location: Abdomen ("six-pack" muscles).
- Function: Flexes the spine.

External and Internal Obliques

- Location: Sides of the abdomen.
- Function: Trunk rotation and lateral flexion.

C. Lower Body Muscles

Gluteal Muscles (Maximus, Medius, Minimus)

- Location: Buttocks.
- Function: Hip extension, abduction, and rotation.
- Clinical relevance: Common site for IM injections.

Quadriceps Femoris Group

- Includes: Rectus Femoris, Vastus Lateralis, Vastus Medialis, Vastus Intermedius.
- Location: Anterior thigh.
- Function: Knee extension.
- Clinical relevance: Vastus Lateralis is often used for pediatric IM injections.

Hamstrings Group

- Includes: Biceps Femoris, Semitendinosus, Semimembranosus.
- Location: Posterior thigh.
- Function: Knee flexion and hip extension.

Gastrocnemius and Soleus
- Location: Posterior lower leg (calf).
- Function: Plantarflexion of the foot.

3. Joints and Their Functions

Joints are where two or more bones meet, allowing for movement and flexibility. They are categorized based on their structure and function:

A. Types of Joints

Fibrous Joints: Immovable (e.g., sutures of the skull).
Cartilaginous Joints: Slightly movable (e.g., intervertebral discs).
Synovial Joints: Freely movable; most common type.
- Examples:
  - Ball-and-socket (shoulder, hip).
  - Hinge (elbow, knee).
  - Pivot (neck).

B. Synovial Joint Components

Articular cartilage: Reduces friction.
Synovial fluid: Lubricates the joint.
Ligaments: Connect bones and stabilize joints.

4. Clinical Applications

Medical assistants frequently encounter musculoskeletal anatomy in their daily work. Understanding these structures is vital for:

A. Administering Injections

IM injections: Deltoid, Gluteus Medius, Vastus Lateralis.
Subcutaneous injections: Fatty tissue beneath the skin (e.g., abdomen for insulin).

B. Assisting with Orthopedic Procedures

Splinting and casting.
Assisting in joint injections or aspirations.

C. Patient Education

Explaining injury prevention (e.g., lifting techniques).
Explaining results of radiologic exams (as interpreted by your provider)
Teaching exercises for rehabilitation.

Next Lesson

Orthopedics Insider

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