Section 7.2 Bone Structure

The patella is an example of a sesamoid bone.

Long bones are classified by having longitudinal axes and expanded ends. This means that these bones are longer than they are wide, and they have distinct ends that are wider and often have a different shape than the shaft of the bone. This classification helps to distinguish long bones from other types of bones, such as cubelike bones, platelike bones, or bones with various shapes that are connected to multiple other bones.

Spongy bone, also known as cancellous bone, is a type of bone that is composed of bars and plates separated by irregular spaces. It is called spongy bone due to its porous and honeycomb-like structure. This type of bone is found at the ends of long bones, in the vertebrae, and in the flat bones of the skull. Spongy bone provides structural support while also allowing for the passage of blood vessels and bone marrow. It is less dense and more flexible than compact bone, which makes it better suited for shock absorption and weight distribution.

Flat bones are classified as platelike structures with broad surfaces. These bones have a relatively flat shape and provide protection to underlying organs and tissues. Examples of flat bones include the skull, sternum, and scapula. They do not have a cubelike shape with equal lengths and widths, nor do they have longitudinal axes and expanded ends. Therefore, the correct answer is platelike structures with broad surfaces.

The correct answer is epiphysis. The epiphysis is the expanded portion at each end of a bone. It contains red bone marrow, which produces blood cells, and is covered by a layer of hyaline cartilage called articular cartilage. The epiphysis plays a crucial role in the growth and development of bones, as well as in the formation of joints. It also provides attachment points for ligaments and tendons.

The wall of the diaphysis, which is the shaft of a long bone, is mainly composed of tightly packed tissue called compact bone. Compact bone is dense and provides strength and support to the bone. It contains osteons, which are cylindrical structures that house blood vessels, nerves, and bone cells. The compact bone also helps in protecting the inner spongy bone and bone marrow.

Trabeculae is the correct answer because spongy bone is composed of a network of thin, branching bony plates called trabeculae. These trabeculae form a lattice-like structure that provides strength and support to the bone while also allowing for the passage of blood vessels and bone marrow. The other options, such as osteons (which are found in compact bone), periosteum (a fibrous membrane that covers the outer surface of bones), and epiphyses (the ends of long bones), are not specific to the structure of spongy bone.

Bone cells are called osteocytes. Osteocytes are mature bone cells that are responsible for maintaining and regulating the mineral content of the bone. They are found within small spaces called lacunae and are connected to each other and the blood supply through tiny channels called canaliculi. Osteocytes play a crucial role in the repair and remodeling of bone tissue, as well as in the regulation of bone density and strength.

An osteon is a cylinder-shaped unit that is found in compact bone tissue. It consists of concentric rings of bone called lamellae, which surround a central canal called the Haversian canal. The central canal contains blood vessels, nerves, and connective tissue. Within the lamellae are small spaces called lacunae, which house mature bone cells called osteocytes. These osteocytes maintain the health and integrity of the bone tissue. Therefore, the option "cylinder-shaped unit containing bone cells that surround a central canal" accurately describes an osteon.

The medullary cavity is a cavity within the diaphysis (shaft) of a long bone that contains marrow. It is responsible for producing and storing blood cells.

The articulating portion of the epiphysis is coated with a layer of hyaline cartilage called articular cartilage. This cartilage helps to reduce friction and absorb shock between bones during movement. It also provides a smooth surface for the bones to glide against each other. The term "articular" refers to its location at the joint, where two bones meet.

Short bones are classified as cubelike, with roughly equal lengths and widths. This means that short bones have a shape that resembles a cube, with similar dimensions for length, width, and height. They are not elongated like long bones or irregular like irregular bones. Short bones are typically found in the wrists and ankles and provide stability and support to the body.

The correct answer is "sesamoid bones, sesamoid bone, sesamoid, sesamoids". Sesamoid bones are a fifth group of bones that some authorities recognize. These bones are small and round, and they are usually found near joints, where they act as a pulley to help tendons move smoothly. They are named after the sesame seed because of their small size and shape.

The periosteum is a tough, vascular covering of fibrous tissue that surrounds bones. It provides protection and support to the bone, as well as a surface for the attachment of muscles and tendons. The periosteum also contains blood vessels that supply nutrients to the bone cells, helping in their growth and repair.

The endosteum is a thin membrane that lines the inner surface of bones and contains bone-forming cells. It plays a crucial role in bone growth, repair, and remodeling by providing a surface for osteoblasts (bone-forming cells) to attach and deposit new bone tissue. The endosteum also contains osteoclasts, which are responsible for bone resorption. Overall, the endosteum is essential for maintaining the integrity and strength of bones.

The extracellular matrix of bone tissue is composed of collagen, which provides strength and flexibility to the bones, and inorganic salts, such as calcium phosphate, which give the bones their hardness and rigidity. These two components work together to make the bone tissue strong, yet flexible, and able to withstand mechanical stress.