4. 3. Major Constituents of a Bone
The ends of a long bone are called the epiphyses
(singular, epiphysis), which are covered by a layer of
hyaline cartilage called the articular cartilage and articulate with other bones. The internal area of the
epiphyses contains red bone marrow where erythrocytes (red blood cells), leukocytes (white blood
cells), and thrombocytes (platelets) are produced. The shaft of a bone is called the diaphysis. The
diaphysis contains an internal medullary cavity that is lined by the endosteum and usually filled with
yellow marrow, where fat is stored. Except for the articular cartilage, a bone is covered by a tough outer
membrane called the periosteum.
In children, an epiphyseal plate of hyaline cartilage separates the epiphysis and diaphysis. It allows for
growth in length. The epiphyseal plate will eventually ossify, at which point bone growth will stop.
4. Parts of Haversian system
5. Osteon-Is the basic unit of structure of compact bone, comprising a Haversian canal and its
concentrically arranged lamellae.
Osteocyte- an osteoblast that has become embedded within the bone matrix, occupying a bone lacuna
and sending, through the canaliculi, slender cytoplasmic processes that make contact with processes of
other osteocytes.
Canaliculi- Also known as lacrimal ducts, these tube-like structures carry the tears from the eyes to the
lacrimal sac.
Haversian Canal- any of the anastomosing channels of the haversian system in compact bone, containing
blood and lymph vessels and nerves
5. List and describe the function of the three major types of cells found in bones.
Bone is formed by three primary cell types:
Osteoblasts:
Osteoblasts are bone-forming cells that descend from osteoprogenitor cells. They form a protein
mixture known as osteoid, which mineralizes to become bone. Osteoid is primarily composed of
Type I collagen. Osteoblasts also manufacture hormones, such as prostaglandins, to act on the
bone itself. They robustly produce alkaline phosphatase, an enzyme that has a role in the
mineralization of bone, as well as many matrix proteins. Osteoblasts are the immature bone cells,
and eventually become entrapped in the bone matrix to become osteocytes, which are the mature
bone cells. All bone lining cells are osteoblasts.
Osteocytes:
Osteocytes are mature bone cells that originate from osteoblasts, which have migrated into and
become trapped and surrounded by bone matrix, produced by themselves. The spaces they
occupy are known as lacunae. Osteocytes have many processes that reach out to meet osteoblasts
and other osteocytes probably for the purposes of communication. Their functions include
formation of bone, maintenance of matrix and homeostasis of Calcium.
Osteoclasts:
Osteoclasts are the cells responsible for bone resorption and remodelling. They are large,
multinucleated cells located on bone surfaces in what are called Howship’s lacunae or resorption
pits. These lacunae, or resorption pits, are left behind after the breakdown of the bone surface.
Because the osteoclasts are derived from a monocyte stem-cell lineage, they are equipped with
phagocytic-like mechanisms similar to circulating macrophages.
8. and/or fibrocartilage. Finally, for the diarthroses joint, its structural name is the synovial joint,
and it is considered freely movable, just like your shoulder joint. They are the body’s most
mobile joints, most numerous joints, and the most complex joints.
13. Identify the types of movement at synovial joints and give examples of specific joints
where each occurs.
The first type of movement classification is called the uniaxial joint. An example of one is the
elbow joint; it is attached around one axis and in on certain place. Also, the first two cervical
vertebrae of the spine use the rotation method but are still considered uniaxial because our neck
is given the ability to turn side to side, and up and down due to that joint. The second type of
movement classification is the Biaxial joint. This joint in the body can be found in the thumb
joint between the first metacarpal and carpal bone, as well as the joint between the radius and the
carpal bones. The biaxial joint has two axes, and is perpendicular to each other, while being in
two planes. The third movement classification is the multiaxial joint. This joint has multiple
axes, for example the shoulder joint, and the vertebral joints.
Questions to the Editor:
1.) Cancer treatment may generate a need for a bone marrow transplant. Osteoporosis is a
condition characterized by an excessive loss of calcium in bone. These 2 conditions are
disruptions or failures of 2 bone functions. Identify these 2 functions and explain what their
normal function should be.
A: One condition is called Hematopoiesis which is normally responsible for the formation of
blood cells in the bone marrow. Another condition is called Mineral Storage which is normally
responsible for maintaining equilibrium in the amount of calcium in the blood.
2.) Explain why a bone fracture along the epiphyseal plate may have serious implications among
children and young adults.
A: This is the most common fracture due to the location of the epiphyseal plate which is at the
end of the long bone. This area is growing throughout young adult and child years, so because it
is growing throughout these years, the fracture wont harden and heal right away causing serious
symptoms.
3.) During the aging process, adults face the issue of a changing skeletal framework. Describe these
changes and explain how these skeletal framework changes affect the health of older adults.
A: During growth, bones and their connectedness lessen causing a weaker skeletal framework.
Adult need to take nutrients and vitamins in order to strengthen their growing bones and
prevent fractures.
