University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

261

Pages:

3
Author:

Mariam A. A.

Describe the structure of a long bone Epiphysis (2 ends) ● At the proximal and distal ends ● Covered with articular/hyaline cartilage ○ The cartilage is avascular and a neural (protects the blood vessels and nerves on the bone from compressive forces) Diaphysis (shaft) ● Weight bearing → distributes weight and compressive forces so that it doesn’t shatter under body weight ● Hollow cavity in the middle of the bone called the medullary cavity that is filled with fatty tissue (yellow bone marrow) ● Nutrient artery or foramen (opening) that goes throughout the shaft Epiphyseal line ● Can be seen on the exterior of the bone in children and adolescents ● Epiphyseal line is like a scar from the cartilage that is seen in the cross section of an adult bone ● Epiphyseal cartilage is in the bone and if the cartilage is still present, the bone can keep on growing (bone cells want to take over the cartilage) Bone coverings: periosteum and endosteum ● Periosteum (external) ○ Connective tissue on the outside like glad wrap around the bone ○ Strong attachment for tendons ○ Protection for the blood vessels to reach its target and reach its nutrient foramen to supply the bone from within ○ There are osteoblasts (located between the periosteum and the bone) ● Endosteum (within) ○ The hollow parts of the bone at the top and bottom of the diaphysis also has connective tissue ○ Maintains bone homeostasis ○ Cells located between the endosteum and bone that is important for the regeneration of bone cells during the bone repair stages (osteoblasts) Blood supply ● Essential for bone healing and growth ● Nutrient artery enters through the nutrient foramen to keep bone alive during life (important in ossification) ● Normally anteriorly or posteriorly on the shaft (and travels longitudinally) ● There can be foramen on the epiphysis as well (result of ossification) Types of bone tissue Compact bone ● ● In the diaphysis (shaft) and perimeter of the long bone Can withstand linear compressive forces through distributing the weight Osteon ● Single circular unit of the bone that takes up the entire length of the bone ● Composed of multiple lamellae (sheets) ● More force = more lamellae in the osteon ● Collagen alternates direction as you go to the next lamellae = resists twisting forces and changes in direction ● There's a central canal → artery, vein and nerve ○ Artery = each osteon gets its own blood supply ○ Vein = gets its own venous drainage ○ Nerves ● Black dots (bottom right image) = lacunae with osteocytes (mature bone cells) that comprises the bone tissue Fractures ● Bone fractured because the force was placed against the longitudinal arrangement of the bones (perpendicular) and the bone can only withstand the pressures that go in the same direction as the osteons [bone cannot withstand perpendicular forces] Spongy bone ● ● ● ● ● ● Not as dense, lots of air spaces No osteons (no longitudinal functional unit) Has osteocytes that can detect when the bone is damaged or subject to stress Distribution of force Same ECM but different bone arrangement Some spongy tissue lines the inside of the medullary cavity Other bone structure ● Bones are like sheets rather than having a shaft and epiphysis Spongy bone is called dipole (Different origin of the