Download 5.2.3 Activity

Activity 5.2.3
Healing of Bone
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Step 1 – Hematoma Formation Blood vessels that are ruptured during the break swell to form a
mass called a hematoma. This mass forms between the broken bones.
Step 2 – Fibrocartilage Callus Formation New capillaries begin to form into the clotted blood in
the damaged area. Connective tissues cells form a mass of repair tissue called a fibrocartilage
callus. This callus contains some cartilage, some bone and collagen fibers and the combined
mass closes the gap between the broken bones.
Step 3 – Bony Callus Formation The fibrocartilage callus is gradually replaced by one made of
spongy bone. This new mass is referred to as the bony callus. Osteoclasts and osteoblasts move
to the area and multiply.
Step 4 – Bone Remodeling Over the weeks and months to come, the callus is remodeled with
the help of osteoclasts and osteoblasts. The shape of the bones will gradually return to normal
and there will eventually be little evidence of the fracture
Calcium Homeostasis
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The hormones parathyroid hormone (PTH) and calcitonin help regulate blood calcium levels.
Calcitonin, secreted by the thyroid gland inhibits osteoclasts and stimulates osteoblasts, thus
decreasing blood calcium levels. Parathyroid hormone is secreted by the parathyroid glands,
which are on the posterior side of the thyroid. Parathyroid hormone inhibits osteoblasts,
stimulates osteoclasts, reduces the output of calcium by the kidneys and promotes the
absorption of calcium by the small intestines, thus increasing blood calcium levels.
Types of Bone Fractures
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Comminuted-A comminuted fracture is a break or splinter of the bone into more than two
fragments. Since considerable force and energy is required to fragment bone, fractures of this
degree occur after high-impact trauma such as in vehicular accidents.
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Depression- A depressed skull fracture is a break in a cranial bone (or "crushed" portion of skull)
with depression of the bone in toward the brain.
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Compression- Occurs when one or more bones in the spine weaken and crumple.
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Transverse-A fracture of a bone is the same as a break in the bone. A fracture of a transverse
process is a break of a part of one of the bones in the spine. This part extends out from the side
of the main body of the bone (called the vertebral body). A transverse process is shaped like a
wing.
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Oblique-An oblique fracture is a relatively common fracture in which the bone breaks
diagonally. Oblique fractures can vary in severity, depending on what bone is affected and how
large the break is. Oblique fractures tend to occur on longer bones like the femur or tibia.
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Spiral-A spiral fracture (a.k.a. torsion fracture) is a bone fracture occurring when torque (a
rotating force) is applied along the axis of a bone. Spiral fractures often occur when the body is
in motion while one extremity is planted.
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Greenstick- a fracture of the bone, occurring typically in children, in which one side of the bone
is broken and the other only bent.
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Open vs. closed- If the bone breaks in such a way that bone fragments stick out through the skin
or a wound penetrates down to the broken bone, the fracture is called an "open" or compound
fracture (Kevin Ware). A closed fracture is a break or crack in the bone that does not come
through the skin but sometimes causes injury to tissues in the area. A closed fracture can vary in
severity, depending on what bone is affected and how large the crack or break is.
Osteoblasts/clasts
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Osteoblasts- A cell that makes bone. It does so by producing a matrix that then becomes
mineralized. Bone mass is maintained by a balance between the activity of osteoblasts that form
bone and other cells called osteoclasts that break it down.
Osteoclasts- A cell that nibbles at and breaks down bone and is responsible for bone resorption.
Functions of Calcium
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It’s essential for blood clotting.
It stabilizes blood pressure.
It contributes to normal brain function.
It’s critical for communicating essential information among cells.
Helps insulin open cells to glucose
Is needed for the release of chemicals that transmit a signal from a nerve cell to a target cell (for
example, when a nerve tells a muscle to move)
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Facilitates the actual process of contraction of the muscle cell
Assists the movement of sperm into an egg to fertilize the egg
Helps with bone strength