Problem 27 - Anatomy and Physiology of Animals

Question

Define the two divisions of the skeleton.

Step-by-Step Solution

Answer

The two divisions of the skeleton are the axial skeleton and the appendicular skeleton.

Step 1: Understanding the Skeleton

The skeleton is the framework of bones and cartilage that supports the body and allows for movement. It is divided into two major parts or divisions.

Step 2: Identify the First Division

The first division of the skeleton is the axial skeleton. The axial skeleton includes the bones that form the longitudinal axis of the body, which mainly includes the skull, vertebral column, and the rib cage.

Step 3: Identify the Second Division

The second division of the skeleton is the appendicular skeleton. The appendicular skeleton comprises the bones of the limbs and girdles, such as the shoulder girdle, pelvic girdle, and the bones of the arms and legs.

Key Concepts

Axial Skeleton

The axial skeleton forms the central core of the human skeletal system. It primarily consists of the skull, vertebral column, and rib cage. This part of the skeleton provides the main framework for the support and protection of the brain, spinal cord, and vital organs in the chest.

Here are some key features of the axial skeleton:

• Includes 80 bones in total
• Supports the head and trunk of the body
• Maintains an upright posture
• Plays a crucial role in protecting the central nervous system and organs within the thoracic cavity

Appendicular Skeleton

The appendicular skeleton is composed of the bones that facilitate movement and interaction with the environment. This division includes the bones of the upper and lower limbs, as well as the girdles that attach them to the axial skeleton.

Key functions of the appendicular skeleton include:

• Allowing a wide range of movements
• Providing leverage and support for locomotion and manipulation of objects
• Including 126 bones, forming the appendages
• Connecting to the axial skeleton through the pectoral and pelvic girdles

Skull and Vertebral Column

The skull and vertebral column are critical components of the axial skeleton. The skull houses and safeguards the brain and forms the structure of the face. It is a composite of numerous bones that collectively offer protection and support.

The vertebral column, or spine, is a flexible column made up of individual vertebrae. It protects the spinal cord and supports the head's weight.

• The skull consists of 22 bones, including the cranium and facial bones
• The vertebral column typically has 33 vertebrae, divided into cervical, thoracic, lumbar, sacral, and coccygeal regions

Rib Cage

The rib cage is another fundamental component of the axial skeleton, which encases and shields the heart and lungs within the thoracic cavity. It is formed by 12 pairs of ribs, the sternum, and the thoracic vertebrae.

Key roles of the rib cage include:

• Protecting vital organs such as the heart and lungs
• Supporting the upper body
• Facilitating breathing movements by expanding and contracting
• Attaching muscles involved in respiration, posture, and movement

Limbs and Girdles

The limbs and girdles are essential parts of the appendicular skeleton, designed for mobility and manipulation. The limbs comprise the bones of the arms and legs, while the girdles serve as points of attachment to the axial skeleton.

Important points about limbs and girdles:

• The upper limbs include the humerus, radius, ulna, carpals, metacarpals, and phalanges
• The lower limbs consist of the femur, tibia, fibula, tarsals, metatarsals, and phalanges
• The pectoral girdle consists of the clavicles and scapulae, connecting the arms to the trunk
• The pelvic girdle consists of the hip bones, supporting the attachment of the lower limbs