© Many football players are able to name their long bones (like the

humerus) because of incidents that they may have experienced in a game.

For those of us who have not broken or fractured enough bones to have memorized what they

are, here is a list of the four different types of bones…

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1) Types of bones- all bones contain two types of bone tissue (compact and

spongy)

Long bones

o The name really says it all

o Name is based off of the shape and length of the bones

o Examples: femur and humerus

Short bones

o Not long bones

o Are small, “box shaped” (1)

o Length is about = to the width

o Examples: wrist and ankle bones

Flat bones

o Are usually quite large

o “Generally broad and thin with a flattened and often curved surface” (1)

o Examples: shoulder blades, ribs, and breastbone

Irregular bones

o “various sizes and shapes” (1)

o Examples: spine and facial bones

o Sesamoid- kneecap/patella

2)Structure of Long Bone

o Diaphyis- shaft, cylinder shape, provides support

o Epiphyses- top and bottom, bulbous shape, mainly spongy bone

o Articular cartilage- covers joint surfaces

o Periostereum- “dense, white fibrous membrane that covers bone except at joint surfaces”

(1)

o Medullary- hollow tube space, in the diaphysis, necessary for survival of the bone

o Endosteum- lines the medullary cavity, epithelial membrane

o (1)

3)Bone Tissue

-“Consists of cells, fibers, and extracellular material, or matrix” (1)

o Inorganic Salts- hydroxyapatite calcium crystals give the bone structure by being

hardened in a process known as calcification in order to give the bones their

strength (the crystals are hardened) (1).

o Measuring density- Osteoporosis is a disease that forms over time where the

bones lose density.

o Organic matrix- made up of “collagenous fibers… protein and polysaccharides

called ground substance” (1), adds to strength and flexibility of bones.

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Haversian systems

Lamelle: concentric, cylinder-shaped layers of calcified matrix Lasunae: small spaces containing tissue fluid in which bone cells lie imprisoned between

the hard layers of the lamellae Canaliculi: ultrasmall canals radiating in all directions from the lacunae and connecting

them to each other and into a larger canal, the Haversian canal Haversian canal: extends lengthwise through the center of each Haversian system;

contains blood vessels, lymphatic vessels, and nerves from the Harversian canal; nutrients and oxygen move through canaliculi to the lacunae and their bone cells—a short distance of about 0.1 mm or less

Bone Cells

Osteoblasts: small cells that synthesize and secrete a specialized organic matrix, called osteoid

Osteoclasts: giant multinucleate cells that are responsible for the active erosion of bone minerals

Osteocytes: mature, nondividing osteoblasts that have become surrounded by matrix and now lie within lacunae

Five homeostatic functions of bones:

1. Mechanical support of soft tissues2. Levers for muscle action3. Protection of the central nervous system4. Release of calcium and other ions for the maintenance of a constant ionic environment in

the extracellular fluid5. Housing and support of hemopoiesis

(2)

Intramembranous vs. Endochondral bone

Intramembranous bones are always flat bones

Endochondral bones include the long, short, and irregular bones (3)

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Describe steps involved in bone fracture repair.

“How fracture healing happensBone fracture healing is a complex process with four steps. All bone fractures must go through this process.” (4)

“Step 1: Inflammation

When a bone

fractures, white

blood cells move

in to the area to

clean up debris

created by the

break. This creates

inflammation,

which triggers the

growth of new

blood cells — the

first stage of

healing.” (4)

“Step 2: Soft callus

As blood cells

divide and

multiply near

the break, new

blood vessels

develop to fuel

the repair

process. The

body also

begins to create

cartilage around

the bone

fracture to

bridge the gap

in the bone.

Called the soft

callus, this

cartilage is

simply fibrous

tissue.” (4)

“Step 3: Hard callus

Eventually, the

body replaces the

soft callus with a

hard callus,

connecting the

bone fragments

more solidly. This

stronger callus,

which creates a

bulge at the site of

“Step 4: Remodeling

In the final

stage of bone

fracture healing,

the body

replaces old

bone with new

bone in a

continual

process called

remodeling.

© (4)© (4)

© (4)

the fracture, can

generally be seen

in X-rays just a

few weeks after

the bone fracture

occurs.” (4)

Remodeling

makes bones

stronger and

more compact

and blood

circulation in

the bone

improves.” (4)

“When a patient breaks a bone, doctors take measures to encourage strong, quick repair. These measures include:

Setting and immobilizing the break. If necessary, a physician will move bone segments

back into place before immobilizing the fracture using a cast or brace.

Surgery. Some patients may need surgery to set and stabilize a fracture — a process that

can involve metal plates, screws or nails. If fractures do not show signs of healing,

additional intervention is necessary. Some doctors choose to perform additional surgeries;

others turn to devices like EXOGEN.

Bone growth stimulation. To help heal fractures, many doctors prescribe a device like

EXOGEN — the only stimulator that uses ultrasound waves to stimulate the body’s natural

healing process, helping boost bone growth.

Therapy. If a patient is in a cast for a long period of time, he or she may benefit from

physical therapy to regain full use of stiff or weak muscles.” (4)

Compare the basic structural units of bone and cartilage.

1.Cartilage: Collagenous fibers embedded in a rubbery ground-substance called Chondrin, which is a protein-carbohydrate complex. The chondron is secreted by chondrocytes.

2.Bone: mineralized connective tissue. Cells called osteocytes deposit a matrix of collagen and calcium-phosphate which harden to form crystals of a substance called hydroxyapatite. Mammalian bone is constructed from repeated units called Haversian Units.The process of making new bone is called ossification.

Identify the three specialized types of cartilage, give

examples of each, and summarize the structural and functional differences among them.

Cartilage is a specialized form of connective tissue containing chondrocytes which secrete, and are surrounded by, an extensive intercellular matrix. Chondrocytes occur singly or in isogenous groups, composed of 2-8 cells derived by mitosis from a single chondrocyte. The cells are in the lacunae (cavities) within the matrix. Matrix stains more intensely immediately adjacent to the lacunae and the dark staining zone is called the capsule. The strength and durability of cartilage are properties of the matrix, which is an interlaced network of collagenous and/or elastic fibers in a ground substance, a gel of complex proteoglycans. The collagen is mostly Type II. How does this differ from dense C.T.?

There are three types of cartilage characterized by the composition of the intercellular matrix.

(1) hyaline, (2) elastic and (3) fibrocartilage.

Hyaline cartilage is found lining articular surfaces, and in the nasal septum, tracheal rings, costal cartilages, and the epiphyseal cartilage of growing bone. Study the trachea on slide #72 (trachea). Even numbered boxes usually contain slides stained for elastic tissues, odd numbered boxes have slides stained with hematoxylin and eosin. The former will have a brown coloration, the latter, the pink and blue you are familiar with. In this slide considerable fading has occurred, and the normal basophilia of freshly stained cartilage is almost absent. The trachea is a large open tube, with cartilage constituting the principal component of its wall.

Using the scanning lens, locate the cartilage rings. At higher power, identify single chondrocytes and locate isogenous groups. There are clear areas between many of the chondrocytes and the walls of their lacunae because of shrinkage of the cells brought about by fixation, and because some chondrocytes had lipid droplets which dissolved during histological preparation.

Identify the perichondrium. Note the gradation of cell shape changes from fibroblast-like in the outer layer to the round cell shape within the cartilage. The perichondrium is acidophilic due to the preponderance of collagen fibers. At the interface between perichondrium and cartilage, transitional cells can be seen which are still elongated but are beginning to be surrounded by matrix.

The cartilage matrix contains collagen fibers, but these are very difficult or impossible to see. Some areas may show some dark-staining material which could be indicative of elastic fibers, but these are best seen in a later slide. Note that the cartilage matrix should be slightly basophilic, especially around the chondrocytes, due to anionic properties of proteoglycans.

Elastic cartilage is found in the ear and epiglottis, where it provides a rigid but elastic, framework. Its principal components are elastic fibers but type II collagen is also present. Some elastic fibers may be present in the tracheal cartilage. Examine a section through infant ear, slide #11 (even boxes only), which has been stained for elastin with resorcin fuchsin. The purple staining interlaced fibers run in all directions, and appear as dots when cut transversely. The nuclei and cytoplasm of the cells are not stained well. The cartilage in this section is immature and therefore richer in cells than adult cartilage. Compare this arrangement of cells and fibers of elastic cartilage with that of hyaline cartilage of the trachea.

Fibrocartilage is found in intervertebral discs, the pubic symphysis, in menisci of joints, and often occurs where tendon and ligament are joined to bones. It resembles a dense C.T. which contains islands of chondrocytes embedded in cartilage matrix. Its appearance varies with its location. The major and characteristic intercellular component of this tissue consists of thick, interlaced collagenous fibers. The ground substance is much less abundant than in hyaline cartilage due to the preponderance of fibers.

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Bone Growth-During development, there are two patterns of bone formation:

intramembranous and endochondral ossification. Intramembranous bones originate between sheet-like layers of connective tissues, and endochondral bones begin as masses of hyaline cartilage that bone tissue later replaces.

Cartilage Growth- cartilage is formed from condensed mesenchyme tissue, which

differentiates into chondrocytes and begins secreting the molecules that form the extracellular matrix

· Ball-&-socket joint: allows freedom to rotate in a back-and-forth movement

· Condyloid joint: this allows the bones to move in any direction, but they cannot

rotate

· Plane joint: this allows them to move in all directions and rotate.

· Hinge joint: allows back and forth movement. (no twisting or side to side. For example

your elbow)

· Pivot joint: this allows one bone to spin around another

· Saddle joint: both of the bones that meet have odd shapes, but they are totally

complementary to one another.