Difference Between Axial and Appendicular Skeleton

The main difference between axial and appendicular skeleton is that the axial skeleton makes up the central axis of the body whereas the appendicular skeleton connects the appendages to the axial skeleton. Furthermore, the axial skeleton consists of six parts: the skull, the ossicles of the middle ear, the vertebral column, hyoid, rib cage, and the sternum while the appendicular skeleton consists of limbs and girdles.  

Axial and appendicular skeleton are the two main parts of the endoskeleton of vertebrates including humans.  

Key Areas Covered 

1. What is the Axial Skeleton
     – Definition, Components, Function
2. What is the Appendicular Skeleton
     – Definition, Components, Function
3. What are the Similarities Between Axial and Appendicular Skeleton
     – Outline of Common Features
4. What is the Difference Between Axial and Appendicular Skeleton
     – Comparison of Key Differences

Key Terms

Appendicular Skeleton, Axial Skeleton, Muscle Attachment, Support, Types of Bones 

What is the Axial Skeleton 

The axial skeleton is the central core of the vertebrate skeleton. Human axial skeleton contains 80 bones. The six components of the axial skeleton are; 

1. The skull – Consists of 8 cranial and 14 facial bones 
2. Hyoid bone – A horseshoe-shaped bone in the anterior midline of the neck 
3. Auditory ossicles – The three bones in the middle ear 
4. Vertebral column – The 26 bones that make up the backbone 
5. Sternum 
6. Ribs – The 24 ribs and the sternum collectively form the thorax 

Figure 1: Axial Skeleton

The main function of the axial bone is to support the upright position of the body. Apart from that, it protects the internal organs of the body, especially by the thorax. Also, the axial skeleton provides sites for the attachment of muscles. 

What is the Appendicular Skeleton 

The appendicular skeleton is the structure that supports appendages. It consists of 126 bones in humans. The six components of the appendicular skeleton are; 

1. Pectoral gridles – Left and right clavicle and 2 scapulae 
2. Arms and forearms – Left and right humerus in the arms and 2 ulna and 2 radii in the forearm 
3. Hands – The 16 carpals (16) in the wrist, 10 metacarpals, 10 proximal phalange, 8 intermediate phalanges and 10 distal phalanges 
4. Pelvis – Left and right hip bone 
5. Legs – Left and right femur in the thighs, 2 patellae in the knee, 2 tibias and2 fibula in the leg 
6. Feet and ankles – The 14 tarsals in the ankle, 10 metatarsals, 10 proximal phalanges, 8 intermediate phalanges, and 10 distant phalanges 
   

   Figure 2: Appendicular Skeleton

The main function of the appendicular skeleton is to support the appendages while providing sites for the attachment of bones. 

Similarities Between Axial and Appendicular Skeleton 

• Axial and appendicular skeleton are the two parts of the skeleton of vertebrates including humans. 
• Both are made up of bones, cartilage, and ligaments. 
• They provide sites for the attachment of muscles.  
• Both aid in the movement of the body. 

Difference Between Axial and Appendicular Skeleton 

Definition 

The axial skeleton refers to the part of the skeleton that consists of the bones of the head and trunk of a vertebrate while the appendicular skeleton is the portion of the skeleton of vertebrates consisting of the bones that support the appendages.  

Significance 

The axial skeleton is the central axis of the human skeleton while the appendicular skeleton consists of appendages connected to the axial skeleton. 

Components 

The axial skeleton is composed of the skull, the ossicles of the middle ear, the vertebral column consisting of a total of 80 bones, hyoid, rib cage, and sternum while the appendicular skeleton is composed of pectoral girdles, arms, forearms, hands, pelvis, legs, feet, and ankles. 

Number of Bones 

The axial skeleton is made up of 80 bones while the appendicular skeleton is made up of 126 bones in humans. 

Function 

Axial skeleton supports the upright position and protects the internal organs while the appendicular skeleton aid in the movement of the body.  

Conclusion 

The axial skeleton is the core of the vertebrate’s skeleton, mainly containing the skull and the vertebrae. On the other hand, appendicular skeleton is the support system for the appendages. The main difference between axial and appendicular skeleton is the structure and function. 

Reference:

1. “Axial Skeleton | Learn Skeleton Anatomy.” Visible Body – Virtual Anatomy to See Inside the Human Body, Available Here   
2. “Biology for Majors II.” Lumen, Open SUNY Textbooks, Available Here    

Image Courtesy:

1. “Axial skeleton diagram” By LadyofHats Mariana Ruiz Villarreal – i did it myself (Public Domain) via Commons Wikimedia    
2. “Appendicular skeleton diagram” By LadyofHats Mariana Ruiz Villarreal – i did it myself (Public Domain) via Commons Wikimedia