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An Introduction to Skeletal System - The Bones and What They Do

human skeleton

The Skeletal System: The skeleton forms the frame for the body and makes up about 1/5th of the body’s weight. It is made up of 206 bones. It also includes cartilage, joints, and ligaments. Besides for forming our body frame, the skeleton has several other jobs. It is the anchor and support for all our muscles and even our organs. It protects our vital organs like our brain, spinal cord, heart and lungs. It allows us to move with muscles attached by tendons using the bones as levers. It is a place for our body to store fat and minerals, like calcium. It is where the body makes most of its new blood cells.

Bones come in many shapes and sizes. The long bones have a long shaft and two bigger ends. These include the bones of the arms and legs. The largest bone in the body, the femur, is a long bone. It is 2 feet long and hollow to make it lighter. It is very strong to support the body’s weight. The short bones are cube-shaped and include the bones of the wrist (carpals) and ankle (tarsals). The flat bones are thin, curved and flattened like the sternum and skull. Lastly, there are irregular bones like the vertebra and pelvis. Each section of the skeleton has a job. Below see all the parts of the skeleton and how they work together to make the body a strong, moving machine.

The Skull: The skull surrounds and protects the brain and the organs of hearing and balance. The facial bones form the structure of the face, hold the eyes, and the organs for taste and smell and anchor the teeth. They have the openings for air and food. The whole skull anchors muscles that hold the head up, allow us to chew, and form facial expressions.


Arms and Hands: Each upper limb includes the humerus (arm), the radius and ulna (forearm) and the bones of the hand: 8 carpals (wrist), 5 metacarpals (palm) and 14 phalanges (fingers and thumb). The arm and forearm bend at the elbow in a hinge joint, which is not as flexible as the shoulder joint, but is much more stable. The hand, with its many joints, is made to be flexible and agile. It can grasp and lift a heavy suitcase or carefully pick up a pin. The upper limb is made to do both and everything in between.

Upper limb

The Pelvis: is formed by 2 hip bones attach to the sacrum of the backbone. On the outside of each side is a deep socket, called the acetabulum, where the head of the leg bones (the femur) sits. The pelvis supports and protects internal organs, attaches the lower limb to the body and with the lower limb supports the weight of the whole upper body. The hip joint is very important for leg movement and is supported by strong muscles and ligaments. Though it is a ball and socket joint like the shoulder, it is more stable and less movable than that joint.


Legs and Feet: The lower limb includes the femur (thigh), the tibia (shinbone) and fibula (leg), and the bones of the foot: 7 tarsals (ankle), 5 metatarsals (foot) and 14 phalanges (toes). The kneecap (patella) sits in front of the knee joint, inside a muscle tendon. The femur is the largest bone in the body and makes up about 1/4th of a person’s height. It forms a ball and socket joint at the hip with the pelvis and a hinge joint at the knee with the tibia. The hip joint is very important for leg movement and is supported by strong muscles and ligaments. Though it is a ball and socket joint like the shoulder, it is more stable and less movable than that joint. The knee, a hinge joint, has less flexibility than the hip but is more stable. However, because the knee carries the bulk of the body’s weight, it is often injured. The entire weight of the body sits on the foot. The foot acts as a lever to move the body forward when we walk or run.

lower LIMB

Recommended Books & Products

Skeletal System Diagram Bundle (High School & College) - Downloadable Only
20 high-resolution, printable diagrams of the skeletal system that are copy-ready* and can be used for teaching and/or study guides for learning the bone names, structure, anatomy and attachment points, and the joints and joint movement, plus a Skeleton Summary. These anatomy diagrams are meant to be used to enhance students' vocabulary and comprehension of the human skeleton.
    1.    The Skeleton Summary
    2.    Full Body Skeleton Diagram
    3.    Skull (Front View) Diagram
    4.    Skull (Side View) Diagram
    5.    Skull (Cranial Cavity) Diagram
    6.    Bones of the Upper Limb Diagram
    7.    Bones of the Pectoral Girdle (Shoulder) Diagram
    8.    Bones of the Rib Cage Diagram
    9.    Bony Features of the Scapula Diagram
    10.    Bony Features of the Humerus Diagram
    11.    Bony Features of the Radius/Ulna Diagram
    12.    Bones of the Hand Diagram
    13.    Bones of the Lower Limb Diagram
    14.    Bony Features of the Vertebral Column Diagram
    15.    Bony Features of the Pelvis Diagram
    16.    Bony Features of the Femur Diagram
    17.    Bony Features of the Tibia/Fibula Diagram
    18.    Bones of the Foot Diagram
    19.    Long Bone Structure Diagram
    20.    Joints of the Body Diagram
    21.    Joints in Motion Diagram

Skeletal System Diagram Bundle (High School & College) - Downloadable Only

National Science Standard Addressed

Grade 6-8 - MS-LS1 From Molecules to Organisms: Structures and Processes

LS1.A: Structure and Function
• All living things are made up of cells, which is the smallest unit that can be said to be alive. An organism may consist of one single cell (unicellular) or many different numbers and types of cells (multicellular). (MS-LS1-1)
• Within cells, special structures are responsible for particular functions, and the cell membrane forms the boundary that controls what enters and leaves the cell. (MS-LS1-2)
• In multicellular organisms, the body is a system of multiple interacting subsystems. These subsystems are groups of cells that work together to form tissues and organs that are specialized for particular body functions. (MS-LS1-3)

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