The femur forms the ball and socket hip joint with the hip bone and forms the knee joint with the tibia and patella. The femur is the largest bone in the body and the only bone of the thigh (femoral) region. Pelvic Girdle and Lower Limbįormed by the left and right hip bones, the pelvic girdle connects the lower limb (leg) bones to the axial skeleton. Each finger has three bones known as phalanges, except for the thumb, which only has two phalanges. The carpals are connected to the five metacarpals that form the bones of the hand and connect to each of the fingers. The lower arm bones form the wrist joint with the carpals, a group of eight small bones that give added flexibility to the wrist. The radius allows the forearm and hand to turn over at the wrist joint. The ulna is on the medial side of the forearm and forms a hinge joint with the humerus at the elbow. The radius and ulna are the two bones of the forearm. It forms the ball and socket joint of the shoulder with the scapula and forms the elbow joint with the lower arm bones. The humerus is the bone of the upper arm. The pectoral girdle connects the upper limb (arm) bones to the axial skeleton and consists of the left and right clavicles and left and right scapulae. Ribs 8, 9, and 10 all connect to the sternum through cartilage that is connected to the cartilage of the seventh rib, so we consider these to be “false ribs.” Ribs 11 and 12 are also false ribs, but are also considered to be “floating ribs” because they do not have any cartilage attachment to the sternum at all. The first seven ribs are known as “true ribs” because they connect the thoracic vertebrae directly to the sternum through their own band of costal cartilage. There are 12 pairs of ribs that together with the sternum form the ribcage of the thoracic region. The sternum connects to the ribs by thin bands of cartilage called the costal cartilage. The sternum, or breastbone, is a thin, knife-shaped bone located along the midline of the anterior side of the thoracic region of the skeleton. For example, the most superior thoracic vertebra is called T1 and the most inferior is called T12. With the exception of the singular sacrum and coccyx, each vertebra is named for the first letter of its region and its position along the superior-inferior axis. Twenty-six vertebrae form the vertebral column of the human body. Found in a small cavity inside of the temporal bone, they serve to transmit and amplify sound from the eardrum to the inner ear. The malleus, incus, and stapes-known collectively as the auditory ossicles-are the smallest bones in the body. The hyoid’s function is to help hold the trachea open and to form a bony connection for the tongue muscles. The hyoid is the only bone in the body that does not form a joint with any other bone-it is a floating bone. The hyoid is a small, U-shaped bone found just inferior to the mandible. The bones of the inferior and anterior portion of the skull are known as facial bones and support the eyes, nose, and mouth. The bones of the superior portion of the skull are known as the cranium and protect the brain from damage. The mandible remains as a movable jaw bone and forms the only movable joint in the skull with the temporal bone. These 21 fused bones are separate in children to allow the skull and brain to grow, but fuse to give added strength and protection as an adult. The skull is composed of 22 bones that are fused together except for the mandible. The appendicular skeleton is made up of 126 bones in the folowing regions: The axial skeleton runs along the body’s midline axis and is made up of 80 bones in the following regions:
These bones are arranged into two major divisions: the axial skeleton and the appendicular skeleton. The skeletal system in an adult body is made up of 206 individual bones.
Finally, the skeleton grows throughout childhood and provides a framework for the rest of the body to grow along with it. Calcium, iron, and energy in the form of fat.
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