6: Axial and Appendicular Skeleton

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6.1: Introduction to the Skeleton System
The skeletal system forms the rigid internal framework of the body. It consists of the bones, cartilages, and ligaments. Bones support the weight of the body, allow for body movements, and protect internal organs. Each bone of the body serves a particular function, and therefore bones vary in size, shape, and strength based on these functions.
6.2: Divisions of the Skeletal System
The skeleton is subdivided into two major divisions—the axial and appendicular. The axial skeleton forms a vertical axis and the appendicular skeleton includes all of the bones of the upper and lower limbs plus the bones that anchor each limb to the axial skeleton
6.3: The Skull
In the adult, the skull consists of 22 individual bones, 21 of which are immobile and united into a single unit. The skull is the skeletal structure of the head that supports the face and protects the brain. It is subdivided into the facial bones and the brain case.
6.4: The Vertebral Column
The adult vertebral column consists of 24 vertebrae, plus the sacrum and coccyx. The vertebrae are divided into three regions: cervical vertebrae, thoracic vertebrae, and lumbar vertebrae.
6.5: The Thoracic Cage
The thoracic cage (rib cage) forms the thorax (chest) portion of the body. It consists of the 12 pairs of ribs with their costal cartilages and the sternum. The ribs are anchored posteriorly to the 12 thoracic vertebrae (T1–T12). The thoracic cage protects the heart and lungs.
6.6: The Pectoral Girdle
The appendicular skeleton includes all of the limb bones, plus the bones that unite each limb with the axial skeleton. The bones that attach each upper limb to the axial skeleton form the pectoral girdle (shoulder girdle). This consists of two bones, the scapula and clavicle. The clavicle (collarbone) is an S-shaped bone located on the anterior side of the shoulder. It is attached on its medial end to the sternum of the thoracic cage, which is part of the axial skeleton.
6.7: Bones of the Upper Limb
The upper limb is divided into three regions. These consist of the arm, located between the shoulder and elbow joints; the forearm, which is between the elbow and wrist joints; and the hand, which is located distal to the wrist. There are 30 bones in each upper limb. The humerus is the single bone of the upper arm, and the ulna (medially) and the radius (laterally) are the paired bones of the forearm.
6.8: The Pelvic Girdle and Pelvis
The pelvic girdle (hip girdle) is formed by a single bone, the hip bone or coxal bone (coxal = “hip”), which serves as the attachment point for each lower limb. Each hip bone, in turn, is firmly joined to the axial skeleton via its attachment to the sacrum of the vertebral column. The right and left hip bones also converge anteriorly to attach to each other. The bony pelvis is the entire structure formed by the two hip bones, the sacrum, and, attached inferiorly to the sacrum, the coccyx .
6.9: Bones of the Lower Limb
Like the upper limb, the lower limb is divided into three regions. The thigh is that portion of the lower limb located between the hip joint and knee joint. The leg is specifically the region between the knee joint and the ankle joint. Distal to the ankle is the foot. The lower limb contains 30 bones. These are the femur, patella, tibia, fibula, tarsal bones, metatarsal bones, and phalanges.
6.10: Embryonic Development of the Skeleton
The skeleton begins to form during early embryonic development. However, growth, remodeling, and ossification (bone formation) continue for several decades after birth before the adult skeleton is fully formed. Knowledge of the developmental processes that give rise to the skeleton is important for understanding the abnormalities that may arise in skeletal structures.
6.11: Anatomical Atlas - Skeleton
A compendium of anatomical images: slides, models, and/or cadavers.
6.12: Practice Practical - Skeleton
Practical examinations in anatomy ask you to identify structures that you have viewed in the laboratory. For each question you will see an image of a slide, model, specimen, etc. and will be asked to give the name or another piece of information about indicated item(s).