Musculoskeletal System and Anatomy - NCLEX-PN

The most superior vertebra of the spine is the atlas, or C1. This bone sits on the axis, or C2, over a bony process called the dens. The coccyx, or "tailbone," is part of the sacrum.

There are 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae. The mnemonic for this is "breakfast at 7, lunch at 12, dinner at 5."

The bone that forms the lower part of the jaw is the mandible. It is the largest and most inferior bone in the face, and articulates with the temporal bones at the temporomandibular joints. The maxilla forms the upper jaw, while the zygomatic bone forms the cheek and part of the orbit.

The occiput is the inferior and posterior bone of the skull. It wraps under the bottom of the skull and forms the base on which the head articulates with the spine. The ethmoid bone and sphenoid bone are housed primarily within the skull, and the maxilla forms the upper jaw and part of the orbit.

The cheek bones are formed by the zygomatic arches, which are part of the temporal bones of the face. The mental protuberance forms the chin, the styloid processes are just under the ears and serve as an attachment point for several muscles of the mouth and throat, and the pterion is the suture where the frontal, parietal, temporal, and sphenoid bones come together.

The bony protuberance(s) at which the occipital bone articulates with the atlas (C1) are the occipital condyles. The external occipital protuberance, external occipital crest, and inion are all part of the occipital bone and serve as the attachment points for various muscles and ligaments.

The orbit is formed by the following bones: the maxilla, the zygomatic bone, the frontal bone, the lacrimal bone, the ethmoid, the sphenoid, and the palatine bone. The temporal bone meets the zygomatic and sphenoid but does not form part of the orbit.

The suture that joins the frontal bone to the parietal bones is the coronal suture. The sagittal suture joins the two parietal bones together along the sagittal plane of the skull. There are no sutures named after the frontal or parietal bones themselves.

The inferior alveolar nerve exits through the mental foramina of the chin. This nerve is a branch of the mandibular nerve and supplies sensory innervation to the lower teeth. The foramen rotundum transmits the maxillary nerve. The supraorbital foramina transmit the supraorbital artery, vein, and nerve. The greater palatine foramen is located in the palatine bone and transmits the greater palatine nerve, artery, and vein.

The falx cerebri, the dura that separates the two hemispheres of the brain, attaches to a bony projection of the ethmoid bone called the crista galli, or "crest of the rooster." This projection is a distinct landmark that arises from the cribiform plate. The ethmoidal labyrinth and orbital plate do not form any attachments to the dura of the brain.

The scapula has multiple fossa that serve as attachment points of various bones and muscles of the shoulder. Among these are the glenoid fossa, where the head of the humerus articulates with the scapula, the subscapular fossa, which is an attachment for the subscapularis muscle, the infraspinous fossa, to which the infraspinatus attaches, and the supraspinous fossa, to which the supraspinatus muscle attaches. There is no suprascapular fossa on the scapula.

The supraspinatus tendon passes under the acromion, a bony hook-like process at the end of the scapular spine. Inflammation of the supraspinatus muscle or tendon can quickly lead to entrapment of this muscle under the acromion, causing pain and reduced mobility. The coracoid process, another projection from the anterior scapula, is an attachment point for several muscles and ligaments, including the pectoralis minor and the short head of the biceps brachii.

The pelvis is formed by the sacrum and coccyx and the three bones that come together to form the innominate: the ilium, ischium, and the pubis. The ileum is a part of the small intestine.

The large, fan-like ridge of bone that can be felt just under the waist is the iliac crest. The anterior superior iliac spine and the anterior inferior iliac spine are smaller protuberances on the ilium that are important landmarks for assessing malpositions of the bones of the sacroiliac joint. The greater sciatic notch is in the posterior ilium and serves as a passage for several muscles and nerves of the pelvic girdle.

The head of the femur rests in the acetabulum, a bony socket on the lateral pelvis that is formed by all three bones of the innominate (the ischium, ilium, and the pubis). The pubic symphysis is a midline cartilaginous joint between the pubic bones. The obturator foramen is an opening in the innominate through which multiple nerves and vessels pass. The pubic tubercle is a bony projection on the pubis that serves as an attachment point for inguinal ligament.

All of the bones listed form the posterior portion of the foot. The largest bone in the foot is the calcaneus. It forms the heel and articulates with the bones of the ankle.

The bones that form the anterior half of the foot (but not the toes) are the metatarsals. These are mirrored in the metacarpal bones of the hand. The carpal bones form the wrist, and the phalanges form the toes and the fingers.

Long bones are lengthened during childhood and adolescence via a process referred to as endochondral ossification. In this process, chondrocytes of the growth plate hypertrophy and eventual die, leaving cavities that are then colonized by osteoprogenitor cells. These osteoprogenitor cells then differentiate into osteoblasts, which mineralize the newly forming bone. None of the other answers are actual processes in bone formation or physiology.

There are five distinct zones in regions of endochondral ossification. These are the resting zone, the zone of proliferation, the zone of maturation, the zone of calcification, and the zone of ossification.

The behavior of cells in the zones of endochondral ossification is as follows:

• The resting zone: normal resting chondrocytes within hyaline cartilage
• The zone of proliferation: rapid mitosis of chondrocytes
• The zone of maturation: hypertrophy of chondrocytes
• The zone of calcification: the death of chondrocytes due to lack of nutrients and inability to eliminate cellular wastes
• The zone of ossification: migration of osteoprogenitor cells into the cavities left behind by dead chondrocytes and mineralization of newly formed bone