The vertebral column of humans is composed of 26 vertebrae which are divided into different regions. The lumbar region of the vertebral column consists of five vertebrae. These five lumbar vertebrae are located in the lower back area of the vertebral column, below the thoracic vertebrae and above the sacral vertebrae. The lumbar vertebrae are larger in size and stronger than the other vertebrae in the vertebral column, and are responsible for supporting the weight of the upper body. The spinal nerves that exit from the vertebral column in the lumbar region supply the lower limbs, pelvic organs, and some of the muscles of the lower back.

The rib cage is a skeletal structure composed of three main components, namely the vertebral column, the ribs, and the sternum. The vertebral column forms the posterior aspect of the rib cage and provides a bony framework for the attachment of the ribs. The ribs are a series of curved bones that attach to the thoracic vertebrae and curve around the chest to connect to the sternum in the front. The sternum is a flat bone located in the center of the chest that serves as the attachment point for the ribs. The spinal cord, on the other hand, is a part of the central nervous system that runs through the vertebral column but is not a component of the rib cage.

The vertebral column, also known as the spine, has several important functions such as providing support to the head, protecting the spinal cord, and serving as a point of attachment for ribs. However, it does not protect all vital organs in the body. The vital organs, such as the heart and lungs, are protected by other structures in the body such as the rib cage and sternum.

The matrix of cartilages is made up of chondrocytes and a gel-like extracellular matrix. This matrix is composed of water, collagen fibers, and proteoglycans, including chondroitin sulfate. The chondroitin sulfate gives cartilage its resistance to compression and its slightly pliable nature.

Cartilage is a type of connective tissue. The skeletal system is made up of bones and cartilages, which are both specialised connective tissues. Cartilages have a slightly pliable matrix, unlike bones, which possess a hard matrix. Cartilage is found in many parts of the body, including the ears, nose, and joints, where it acts as a cushion between bones.

The adult human body has a total of 206 bones. However, the number of bones in a human body changes over time. At birth, the human body has about 270 bones, which eventually fuse together as we grow up, resulting in the adult number of 206 bones. The skeletal system serves several functions, including support, protection, and movement.

The human body has 12 pairs of ribs, which articulate with the vertebral column dorsally and with the sternum ventrally with the help of hyaline cartilage. Hyaline cartilage is a precursor of bone.

The occipital condyles are two rounded processes located on the inferior surface of the occipital bone. The atlas, which is the first cervical vertebra of the vertebral column, articulates with the occipital condyles to support the weight of the skull and allow for its movement. This joint is known as the atlanto-occipital joint and is responsible for the nodding and shaking movements of the head. The atlas is unique among the vertebrae in that it has no body or spinous process, but instead consists of an anterior and posterior arch and two lateral masses.

The sternum, also known as the breast bone, is a flat bone located in the midline of the thorax or chest. It is present ventrally in the body and serves as the point of attachment for the ribs. The thoracic region of the spine is located between the cervical region (neck) and the lumbar region (lower back). Therefore, option C is the correct answer.

Each limb of the human body has 30 bones. These bones along with their respective girdles constitute the appendicular skeleton. The appendicular skeleton is one of the two major divisions of the skeletal system, with the axial skeleton being the other. The axial skeleton is composed of the bones of the skull, vertebral column, and rib cage, while the appendicular skeleton comprises the bones of the upper and lower limbs, as well as the pectoral and pelvic girdles.