The ilium

The ilium is the largest and most superior of the three bones that join to form the hipbone, or os coxa. It is a wide, flat bone that provides many attachment points for muscles of the trunk and hip. You can find the crest of your ilium by placing your hands on your hips. The superficial location of the ilium makes it a common site for extracting bone tissue for grafting and bone marrow for transplants.

The sacrum

The sacrum is a large wedge shaped vertebra at the inferior end of the spine. It forms the solid base of the spinal column where it intersects with the hip bones to form the pelvis. The sacrum is a very strong bone that supports the weight of the upper body as it is spread across the pelvis and into the legs. Developmentally, the sacrum forms from five individual vertebrae that start to join during late adolescence and early adulthood to form a single bone by around the age of thirty. A ridge of tubercles along the posterior surface of the sacrum represents the spinous processes of these fused bones.

The bones of the pelvis and lower back

The bones of the pelvis and lower back work together to support the body’s weight, anchor the abdominal and hip muscles, and protect the delicate vital organs of the vertebral and abdominopelvic cavities.

The vertebral column of the lower back includes the five lumbar vertebrae, the sacrum, and the coccyx. These bones work together to provide flexibility to the trunk, support the muscles of the trunk, and protect the spinal cord and spinal nerves of the back. Lumbar vertebrae support much more body weight than the other vertebrae in the body and are therefore the largest and most robust vertebrae in the body. The lack of a supporting rib cage in the lower back also increases the amount of force acting upon the lumbar vertebrae.

The sternum

The sternum, commonly known as the breastbone, is a long, narrow flat bone that serves as the keystone of the rib cage and stabilizes the thoracic skeleton. Several muscles that move the arms, head, and neck have their origins on the sternum. It also protects several vital organs of the chest, such as the heart, aorta, vena cava, and thymus gland that are located just deep to the sternum.

The sternum is located along the body’s midline in the anterior thoracic region just deep to the skin. It is a flat bone about six inches in length, around an inch wide, and only a fraction of an inch thick. The sternum develops as three distinct parts: the manubrium, the body of the sternum (sometimes called the gladiolus), and the xiphoid process. The shape of the sternum looks somewhat like a sword pointing downwards, with the manubrium forming the handle, the body forming the blade, and the xiphoid process forming the tip. In fact, the name manubrium means “handle,” gladiolus means “sword,” and xiphoid means “sword-shaped.”

The costal cartilage

The costal cartilage is a set of hyaline cartilage bands that attach the medial end of the seven true ribs to the lateral border of the sternum (breastbone). Costal (cost- = rib) cartilage also connects the three superior false ribs to the sternum, but these false ribs are attached indirectly by way of the seventh true rib’s cartilage band.

The spine

Stretching down the midline of the trunk from the base of the skull to the coccyx, the spine plays an extremely important role in our bodies as it supports the upper body’s weight; provides posture while allowing for movement and flexibility; and protects the spinal cord.

The spine, also known as the vertebral column or spinal column, is a column of 26 bones in an adult body – 24 separate vertebrae interspaced with cartilage, and then additionally the sacrum and coccyx. Prior to adolescence, the spine consists of 33 bones because the sacrum’s five bones and the coccyx’s four do not fuse together until adolescence.

The bones of the chest and upper back

The bones of the chest and upper back

The bones of the chest and upper back combine to form the strong, protective rib cage around the vital thoracic organs such as the heart and lungs. The rib cage also anchors the bones of the head, neck, shoulders, and arms to the trunk of the body. Powerful muscles that move the head and arms attach to these bones as well. The bones of the chest and their joints also support the upper body’s weight.

The skull

A collection of 22 bones, the skull protects the all-important brain and supports the other soft tissues of the head. During fetal development, the bones of the skull form within tough, fibrous membranes in a fetus’ head. As these bones grow throughout fetal and childhood development, they begin to fuse together, forming a single skull. The only bone that remains separate from the rest of the skull is the mandible, or jaw bone. Early separation of the bones provides the fetal skull with the flexibility necessary to pass through the tight confines of the birth canal. During childhood development, the skull bones remain somewhat separated, allowing for growth of the brain and skull. Upon reaching maturity, our skull bones fuse to produce a rigid protective shell for the soft nervous tissue of our brain.

The bones of the head and neck

The bones of the head and neck play the vital role of supporting the brain, sensory organs, nerves, and blood vessels of the head and protecting these structures from mechanical damage. Movements of these bones by the attached muscles of the head provide for facial expressions, eating, speech, and head movement.

The skull consists of 22 cranial and facial bones, which, with the exception of the mandible, are tightly fused together. The skull encases and protects the brain as well as the special sense organs of vision, hearing, balance, taste and smell. Attachment points for the muscles of the head and neck are located on the exterior surfaces of the skull and allow for important movement like chewing, speech, and facial expressions. Teeth are rooted into deep sockets in the mandible and maxillary bones. The upper portions of the digestive and respiratory tracts are also housed within the hollow oral and nasal cavities of the skull.

Myology (MYOLOGIA) - the science of muscles

Myology (MYOLOGIA) - the science of muscles

Development of the muscles

The muscles and fascia develop from myotomes, including from the dorsal part of myotomes develop deep back muscles, from the ventral part of myotomes - the muscles of the front and literal surface of the body (muscles of the chest, abdomen, neck). The diaphragm develops from the sixth cervical myotome. At the end of 4-th week of fetal development, muscles of limbs develop from buds of limbs. From buds of mesoderm the anterior of 4 lower cervical and first thoracic myotomes develop muscles of the upper limbs. Chewing and mimic muscles, some muscles of the neck, the muscles of the soft palate, throat, larynx develop from the mesoderm of gill arches.