a. Long Bones: These bones are longer than they are wide and have a shaft (diaphysis) with expanded ends (epiphyses). Examples include the femur (thigh bone), humerus (upper arm bone), and tibia (shin bone). b. Short Bones: Short bones are roughly equal in length and width, providing stability and support. They are found at the end of long bones in the upper and lower limbs, where the tendons cross. Examples include the bones of the wrist (carpals) and ankle (tarsals). The main function of the short bone is to protect the tendons from excess stress and wear by reducing friction. c. Flat Bones: In flat bones, the two layers of compact bone cover both spongy bone and bone marrow space. They grow by replacing connective tissue. Fibrocartilage covers their articular surfaces. This group includes the following bones: The skull bones The ribs The sternum The scapulae The prime function of flat bones is to protect internal organs such as the brain, heart, and pelvic organs. Also, due to their flat shape, these bones provide large areas for muscle attachments. d. Irregular Bones: Irregular bones have complex shapes that do not fit into the above catehttps://jdmanursingschool.com/product/anatomy-physiology-bundle-with-flashcards-and-stickers-anatomy-study-guide-nursing-school-notes-medical-notes-instant-download-pdf/gories. The complex shape of these bones help them to protect internal structures. For example, the irregular pelvic bones protect the contents of the pelvis. Some examples of these types of bones include: The bones of the spine (i.e. vertebrae) The bones of the pelvis (ilium, ischium and pubis)
Four Major Layers Of Bone
Bones, which are the primary components of the skeletal system, have several layers that contribute to their structure and function. The major layers of a bone are as follows:
Periosteum: The periosteum is the outermost layer of a bone. It is a dense, fibrous connective tissue membrane that covers the entire bone surface, except for the articular surfaces found at joints. The periosteum contains blood vessels, nerves, and cells involved in bone growth and repair. It plays a crucial role in providing nourishment and aiding in the attachment of tendons and ligaments to the bone.
Compact Bone: Beneath the periosteum lies the compact bone, also known as cortical bone. It forms the dense, hard outer layer of the bone. Compact bone is composed of tightly packed cylindrical units called osteons or Haversian systems. Each osteon consists of concentric layers of mineralized extracellular matrix called lamellae, which surround a central canal containing blood vessels and nerves. Compact bone provides strength, support, and protection to the bone.
Spongy Bone: It is also known as cancellous or trabecular bone, spongy bone is found in the interior of bones, beneath the compact bone. It consists of a network of thin, branching bony struts called trabeculae, which create a honeycomb-like structure. The spaces between the trabeculae are filled with red bone marrow, where blood cells are produced. Spongy bone provides structural support while being lighter and more flexible than compact bone.
Bone marrow: It is a soft, gelatinous tissue found within the cavities of certain bones, such as the femur, humerus, and pelvis. It is divided into two types: a. Red Bone Marrow: Red bone marrow, also known as myeloid tissue, is responsible for the production of blood cells. It contains hematopoietic stem cells, which give rise to red blood cells, white blood cells, and platelets. Red bone marrow is primarily found in the spongy bone of long bones and flat bones in adults.
