Human Skeletal System: Bone Structure & Types Quiz

Skeletal System: Bone Structure and Types

The human skeletal system is a complex network of bones, joints, and muscles that provide support, stability, and movement to the human body. With over 200 bones, the skeletal system is the body's framework, and it plays a crucial role in protecting vital organs, storing minerals, and facilitating movement. In this article, we will explore the structure of bones and the different types of bones that make up the human skeleton.

Bone Structure

Bones are composed of two types of tissue: organic and inorganic. The organic phase consists of cells and the collagen-forming part of the matrix, while the inorganic phase contains hydroxyapatite, calcium salts, and other minerals. The bone essentially works as a reservoir of calcium, which is important for most metabolic functions in the human body.

Microscopically, cortical bone is made up of osteons, which are made up of haversian systems, consisting of concentric lamellae of bone surrounding a central haversian canal. These lamellae are often called by different names, depending on their location.

Types of Bones

The human skeleton consists of five main types of bones: long, short, flat, irregular, and sesamoid bones.

Long Bones

Long bones are the longest and strongest type of bone in the body. They consist of a long shaft with two bulky ends or extremities. Long bones include bones of the thigh, leg, arm, and forearm. They are primarily compact bone but may have a large amount of spongy bone at the ends or extremities. Examples of long bones are the femur (thigh bone), tibia (shin bone), humerus (upper arm bone), and radius (forearm bone).

Short Bones

Short bones are roughly cube shaped with vertical and horizontal dimensions approximately equal. They consist primarily of spongy bone, which is covered by a thin layer of compact bone. Short bones include the bones of the wrist and ankle, such as the carpals and tarsals.

Flat Bones

Flat bones are thin, flattened, and usually curved. Most of the bones of the cranium are flat bones. They consist of two outer layers of compact bone and an inner layer of spongy bone. Examples of flat bones are the skull bones (frontal, parietal, temporal, occipital, sphenoid, and ethmoid), breastbone (sternum), ribs, and shoulder blades (scapulae).

Irregular Bones

Bones that are not in any of the above three categories are classified as irregular bones. They are primarily spongy bone that is covered with a thin layer of compact bone. The vertebrae and some of the bones in the skull are irregular bones.

Sesamoid Bones

Sesamoid bones are embedded in muscles and tendons near the surfaces of joints. They protect tendons from wear and stress. Examples of sesamoid bones are the patella (kneecap) and the small bones in the wrists and ankles.

In summary, the skeletal system is a complex network of bones, joints, and muscles that work together to provide support, stability, and movement to the human body. The different types of bones, including long, short, flat, irregular, and sesamoid bones, each have unique shapes and functions that contribute to the overall structure and function of the skeleton.