INSIDE!

See how

bones

work

together!

Humerus (long bone) Scapula (flat bone)

Phalanx (short bone)

Vertebra (irregular

bones)

Diaphysis

Epiphysis

Articular cartilage

Periosteum

Medullary cavity

Endosteum

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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

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.

© (5)

6. List and discuss the five homeostatic functions of bones.

The functions of bone(s) are:

1 mechanical support of soft tissues

2 levers for muscle action,

3 protection of the central nervous system,

4 release of calcium and other ions for the maintenance of a constant ionic environment in the extracellular fluid,

5 housing and support of hemopoiesis © (6)

7. Compare and contrast the development of intramembranous and endochondral bone

Intramembranous ossification takes place within a connective tissue membrane. Bones began to take

shape when groups of osteogenic stem cells within the membrane differentiate into osteoblasts called

centers of ossification. The secrete matrix material and collagenous fibrils. The Golgi apparatus in an

osteoblast specializes in synthesizing and secreting carbohydrate compounds of the type called

mucopolysaccarides, and its endoplasmic reticulum makes and secretes collagen, a protein. In time,

large amounts of ground substnce accumulate around each osteoblast. Bundles of collagenous fibers

then become embedded in the ground substance. They combine and make up organic bone matrix.

Most of the bones of the body are formed from cartilage models which bone formation spreading from

the center to the ends. Cartilage model of a typical long bone can be identified early in the embryonic

life. The cartilage model then develops a periosteum that soon enlarges and produces a ring of bone,

which is deposited by the osteoblasts. Soon after the appearance of bone, the cartilage begins to calcify

and a primary ossification center forms when a blood vessel enter the rapidly changing cartilage model

at the midpoint of the diaphysis. Eventually, secondary ossification centers appear in the epiphyses

proceeds from each end. The epiphyseal plate, a layer of cartilage, between the epiphyseal and the

diaphysis which remains until bone reaches full length.©1

8. Describe the steps in bone fracture repair

Vascular damage occurring immediately after a fracture results in hemorrhage and pooling of blood at

the point of injury. The resulting blood clot is called a fracture hematoma. As the hematoma is

reabsorbed the formation of specialized callus tissue occurs which binds the broken ends of the fracture

on the outside and inside. These tissues collar the broken ends and stabilize the fracture so healing can

proceed. If everyone proceeds as it should, the callus tissue will be modeled and replaced with normal

bone as the injury heals completely. ©1

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9. The basic structural units of a bone are that bones are made up of osteoblasts, osteocytes, and osteoclasts and bone lining cells. The cartilage is composed of chondroblasts, chondrocytes, and dense

matrix made up of collagen and elastic fibers.

10. Three types of cartilage:

Hyaline- most common type of cartilage, located in articular surfaces, the trachea and larnx, and ventral ends of ribs. Two different types of hyaline are interstitial and appositional. Interstitial is where the chells

in lacunae grow and are trapped together. Appositional are the cells from the inner edge of perichondrium will produce cartilage.

Elastic- Dense and branching located in larynx, epiglottis, and pinna of ear. Fibrocartilage- Cross between dense connective tissue and hyaline cartilage, form of tissue, located in

intervertebral disks, pubic symphysis, and tendon to bone attachment sites

11. Compare the mechanism of growth in bone and cartilage.

The mechanisms of bone growth are when bones grow longer over time but also gain thickness.

There are also mechanisms that allow bones to grow in both length and width. Cartilage

production on the other hand, is classified by a process called chondrification. This process is

when cartilage is formed from condensed mesenchyme tissue, which differentiates into

chondrocytes and begins secreting the molecules that form the extracellular matrix

12. Compare the classification of joints according to both structure and function.

The primary joint classifications are synarthroses, amphiarthroses, and diarthroses. Each one has

a structural name and a specific degree of movement. For the synarthroses joint, it is considered

a fibrous joint and its permitted movement is in fact immovable, for example the sutures of the

skull. The surfaces of the bones form fibrous tissue joints closely together. Next, there is the

amphiarthroses joint which is considered slightly movable like the pubic symphysis. Its

structural name is the cartilaginous joint due to it being joined together by hyaline cartilage

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.