1.) Specific anatomical characteristics of typical cervical, thoracic, and lumbar vertebrae:
- Cervical vertebrae: There are seven cervical vertebrae in the human spine, located in the neck region. They are smaller and more delicate than the thoracic and lumbar vertebrae. Cervical vertebrae have a bifid (split) spinous process and transverse foramina, which allow passage of the vertebral arteries and veins that supply blood to the brain. They also have small, oval-shaped vertebral bodies and relatively large vertebral arches.
- Thoracic vertebrae: There are twelve thoracic vertebrae in the human spine, located in the upper back region. They are larger and more robust than the cervical vertebrae. Thoracic vertebrae have long, downward-pointing spinous processes and costal facets for articulation with the ribs. They also have heart-shaped vertebral bodies that are larger than those of the cervical vertebrae, but smaller than those of the lumbar vertebrae.
- Lumbar vertebrae: There are five lumbar vertebrae in the human spine, located in the lower back region. They are the largest and strongest of the vertebrae. Lumbar vertebrae have short, thick spinous processes and large, kidney-shaped vertebral bodies. They also have broad, flat transverse processes and no costal facets, as they do not articulate with the ribs.
2.) Structure of an osteon:
An osteon (also called a Haversian system) is a cylindrical unit of compact bone tissue that forms the basic structural and functional unit of bone. It consists of concentric layers of bone tissue called lamellae, which are arranged around a central canal called the Haversian canal. The Haversian canal contains blood vessels and nerves that supply nutrients and oxygen to the bone cells (osteocytes) and remove waste products. The osteocytes are located in small spaces called lacunae, which are connected by tiny channels called canaliculi. The canaliculi allow the osteocytes to exchange nutrients and waste products with each other and with the blood vessels in the Haversian canal. The osteons are interconnected by perforating canals called Volkmann's canals, which allow blood vessels and nerves to penetrate the bone tissue and connect adjacent osteons. Together, the osteons form a strong and flexible matrix that gives bone its characteristic strength and resilience.