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135 Cards in this Set

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  • Back
Bone's unique architecture provides what?
Optimally arranged to provide maximum strength for the least weight.
Dependent on the stresses placed on the bone.
What tissue is bone and cartilage derived from?
Bone and cartilage are connective tissues and are therefore mesenchymal in origin.
Does cartilage have perfusion?

Cartilage is an avascular tissue whose cells are nourished by diffusion from capillaries in the perichondrium or synovial fluid (joints).
Due to the low levels of oxygen in cartilage, what is a result?
Because of the low O2 tension, anaerobic glycolysis is favored and the metabolic rate is low, which has significant consequences with respect to injury and repair.
What is the perichondrium?
Layer on outside of most cartilage.

Dense connective tissue.
What are the two types of cells present in cartilage?
chondroblasts and chondrocytes
Describe chondroblasts:
Chondroblasts actively synthesize and deposit extracellular matrix components and fibers, but are not yet trapped by this matrix.
Describe chondrocytes:
Chondrocytes are the mature cells of cartilage and are completely surrounded by cartilage matrix, and they reside in small spaces called lacunae. Usually, several cells occupy one lacuna as a result of cell divisions.
What are lacunae?
Space where chondrocytes reside.
Name a few components chondrocytes and chondroblasts secrete:
Collagen (Type II), hyaluronic acid, proteoglycans, and glycoproteins are the principal components of the extracellular matrix.

Elastic cartilage also contains elastin.

In fibrocartilage there are also collagen type I fibers present in the matrix.
Describe ground substance:
Anything in ECM excluding the collagen and elastic fibers.

This is a highly hydrated gel composed of various proteoglycans, and it is the association of these proteoglycans with water and collagen that imparts to cartilage its characteristic firmness and resiliency.
Describe the proteoglycans of cartilage:
polypeptide chains glycosidically-linked with glycosaminoglycans (primarily chondroitin sulfates and keratan sulfates). Several proteoglycans bound to a hyaluronic acid core form a proteoglycan aggregate.
What is the most widespread form of cartilage in the body?
Hyaline cartilage
How are most bones formed?
Most bones are formed by replacing a hyaline cartilage model (endochondral bone formation).
Where in the adult is hyaline cartilage found?
In the adult, hyaline cartilage is found in the larynx, trachea, bronchi, ribs, and on the articular surface of bones.
How does elastic cartilage differ from hyaline cartilage?
Elastic cartilage differs from hyaline cartilage primarily in its high content of elastic fibers which impart flexibility and resiliency.
Where is elastic cartilage found?
It can be found in the external ear, auditory or Eustachian tube, and epiglottis.
Describe fibrocartilage and where is it found?
fibrocartilage possesses prominent bundles of collagen fibers (type I) which give it tensile strength.

It is found in areas that are subjected to frictional forces, such as in the intervertebral discs, pubic symphysis and the temporomandibular joint.
How is bone distinguished from cartilage?
Bone contains inorganic calcium salts in its ground substance, thus making the matrix rigid.

What does the sequested Calcium in bone do?
Creates the rigid matrix and serves as a store for the body.
Does bone have perfusion.
Yes, via:

bone is highly vascularized and contains nerves, blood vessels and a lymphatic system.
What are the (3) types of cells within bone?
osteoblasts, osteocytes, and osteoclasts
Describe osteoblasts:
Osteoblasts produce the collagen (Type I) and ground substance of bone.

They are found at the surfaces of bone (both at the outside and inside), and they arise from the periosteum and endosteum.
Where on the bone do onsteoblasts arise from?
Periosteum and endosteum
What do osteoblasts produce?
Collagen (Type 1) and ground substance of bone
What are osteocytes?
Osteocytes are derived from osteoblasts, and the term refers to cells trapped within the bone matrix.
What are the channels that connect osteocytes and what are they for?
have long cytoplasmic processes that "travel" through canaliculi (small canals) and thereby contact the processes of other osteocytes, thus providing a means of communication.
What are osteoclasts?
Osteoclasts are large multi-nucleated cells which arise from the fusion of bone marrow-derived precursors. They play an important role in bone remodeling, and they resorb both the mineral and organic components of bone.
How many nucleus' do osteoclasts have?
What is the outer layer of bone called? Do they have any special abilities?

They form osteoblasts and are called osteoprogenitor cells.
What are osteoprogenitor cells?
The periosteum cells have the capability to differentiate into osteoblasts and are called osteoprogenitors cells.
What is the inner surface of bone called?

Usually one layer

Similar to periosteum
How much of bone is inorganic and organic?
65-70%: Inorganic Salts
30-35%: Organic matrix
What makes up a majority (90%) of the organic matrix in bone?
collagenous fibers

Predominantly Type I
What are some bone specific proteins found in the bone matrix?
sialoproteins, ostenectin and osteocalcin

These proteins are thought to play a role in the promotion of bone matrix calcification and in calcium deposition.
What is the chief inorganic component of bone?
crystallized Hydroxyapetite
Describe primary bone:
first bone formed in the fetus and is also found as repair bone formed after breakage.

It is sometimes called immature or woven bone. It is temporary and marked by irregular arrays of collagen fibers and a lower inorganic content than mature bone.
Where does primary bone persist in the adult?
It persists in the adult in tooth sockets and some tendon insertions.
Describe spongy bone:
Spongy (cancellous) bone is made up of interconnected trabeculae which form a meshwork of bone with marrow spaces.
Describe compact bone:
compact (dense) bone is solid bone which results from the remodeling of primary bone into secondary (or mature) bone. In the adult, bone tissue usually consists of spongy and compact bone. The compact bone has a defined organization, lamellae, which bone are organized in a concentric way (concentric lamellae)around the nutrient blood supply.
What are lamellae?
Concentric circles in the osteon
What are volkmann's canals?
enclose blood vessels coming from outside the bone or from the marrow cavity into the bone and between osteons
What are haversian canals?
Haversian canals, on the other hand, enclose blood vessels which have branched from those in Volkmann's canals. Nerves and lymphatics can also penetrate these canals.
What are present at the boundary of each lamellae?
spaces which contain the cell bodies of the osteocytes, called lacunae.
What are canaliculli?
________________ surround the long cellular processes of the osteocytes and provide a network of narrow passageways for nutrient passage from the Haversian canal to the outermost osteocytes in their lacunae. They also connect processes of individual osteocytes.
circumferential lamellae
________________________ are formed by osteoblasts derived from the periosteum. These lamellae form an outer ring on the surface of a long bone.
What is the functional unit of bone?
Haversian systems (osteon)
Within one osteon, how many concentric lamellae?
What are interstitial lamellae?
remnants of incompletely resorbed Haversian systems.
What (2) ways can bone formation occur?
Intramembrous Ossification
Endochondral Ossification
Where does intramembrous ossification take place?
_____________ occurs mostly in the bones of the skull and face
Describe the steps in intramembrous ossification:
Mesenchymal cells develop into osteoblasts and begin to lay down matrix and collagen type I fibers between cells until the cells are surrounded by it.

The deposition of minerals within the matrix turns this into bone.

Appositional growth occurs at the outer edges, and remodeling by osteoclasts and osteoblasts allow shape changes of the bones to occur with growth of the body.

Appositional growth is also responsible for the increase in width of long bones.
What is the main premise of endochonral ossification?
Endochondral ossification occurs when hyaline cartilage is replaced with bone.

It is also responsible for the longitudinal growth of the long bones.
Describe intramembrous ossification as seen in development of long bones:
Mesenchyme cell in the membrane become osteochondral progenitor cell
osteochondral progenitor cell specialized to become osteoblast
Osteoblast produce bone matrix and surrounded collagen fiber and become osteocyte
As the result process trabeculae will develop
Osteoblast will trap trabeculae to produce bone
Trabeculae will join together to produce spongy cell
Cells in the spongy cell will specialize to produce red bone marrow
Cells surrounding the developing bone will produce periosteum
Osteoblasts from the Periosteum on the bone matrix will produce compact bone
How does bone growth occur in increasing thickness and length?
The increase in thickness occurs through an intramembranous bone formation (apposition), whereas the growth of long bones in length occurs through endochondral bone formation at the epiphyseal plate.
What are the (5) zones within the epiphyseal plate?
Resting zone: cartilage cells, no mitosis.
Proliferative zone: cartilage cells are actively proliferating.
Hypertrophic cartilage zone: the chondrocytes undergo hypertrophy.
Calcified cartilage zone: the cartilage matrix becomes calcified.
Ossification zone: the calcified matrix is remodeled, and bone is laid down.
Bone increases in length on the diaphyseal side until closure of the plate occurs, usually in the teen years.
On what side of the epiphyseal plate does bone grow?
Diaphysial side
Describe bone repair:
Bone repair recapitulates to some extent bone formation. Thus, mesenchymal cells will undergo differentiation into chondroblasts and osteoblasts. In the repair of long bones, cartilage formation will be combined with bone differentiation and the cartilage matrix will be replaced by bone matrix. Deposited bone will be resorbed and properly replaced by the combined activities of osteoblasts and osteoclasts.
What is the most abundant type of cartilage in the body?
Hyaline cartilage

Contains collagen type II
How are most bones in the body created?
Endochondral Ossification
In the adult, where is Hyaline Cartilage found?
In the adult, hyaline cartilage is found in the larynx, trachea, bronchi, ribs, and on the articular surface of bones.
Where in the body is fibrocartilage found?
Type I fibers

It is found in areas that are subjected to frictional forces, such as in the intervertebral discs, pubic symphysis and the temporomandibular joint.
What collagen type is the most important in cartilage?
Collagen Type II is the hallmark of cartilage.

Fibrocartilage contains Type II and a bit of Type I to increase its tensile strength substantially.
How does cartilage gets its nourishment?
Via diffusion from the synovial fluid or perichondrium (if not an articulating surface)
On the articulating surface of cartilage, what is missing in comparison to other cartilage tissues?
Perichondrium is absent
What do chondroblasts and chondrocytes secrete?
Chondroblasts and chondrocytes secrete a variety of components: Collagen (Type II), hyaluronic acid, proteoglycans, and glycoproteins are the principal components of the extracellular matrix.
What is ground substance heavily loaded with?
Heavily loaded with proteoglycans. The key property being it's hihgly charged state that attracks a substantial amount of water.
Does cartilage have nerves?
No, no nerves are present.
Describe the cross section of a cilia:
composed of microtubules, 9 pairs and a doublet in the middle.
What type of cartilage is the precursor for the skeleton in the fetus?
Hyaline Cartilage
Where does most cartilage growth occur?
As an embryo
What two ways can cartilage grow?
Why is hematopoeisis not considered a function of bone?
It happens to occur within the bone cavity...not actually the bone.
What hormone causes release of calcium?
Parathyroid hormone
What hormone cause deposition of calcium?
What are the (5) ways of classifying bones?
Long: hand

Short: wrist

Flat bones: skull

Irregular: vertebrae

Sesamoid: knee (bone within a tendon)
What two methods can bone be formed?
Endochondral (cartilage model)


Intramembrous (flat bones, within a membrane, osteoblast from bone matrix was derived directly from mesenchymal cells)
How can you classify the bones based upon region of body?
Axial: Cranial and Vertebral Column

Appendicular: Appendiges including clavicle and shoulder girdle
Within spongy bone, the arrangement of bone tissue is in 'pillars'. What are these pillars called?
What is cancellous bone?
aka Spongy, Trabecular Bone
How do long bones grow in length?
Endochondral ossification at the epiphyseal plate
What is the primary inorganic component of bone?
the primary inorganic component of bone are crystals of a highly substituted hydroxyapatite [Ca10 (PO4)6 (OH)2].
How does bone grow?
Bone can only grow via appositional growth. Can not grow from the inside.
What type of collagen is in bone?
Collagen Type I is in bone
Before mineralization, what is the organic matrix called?
As osteoclasts eat away bone, they create depressions called _____________?
Howship's lacunae
What are osteoblasts derived from?
Mesenchymal Cells
What are osteoclasts derived from?
Monocyte blood cells -> macrophages -> osteoclasts
What is the first kind of bone made in the fetus?
Primary bone
What type of bone is formed during repair?
Primary bone
What is primary bone?
aka: woven bone, immature bone

temporary and marked by irregular arrays of collagen fibers and a lower inorganic content than mature bone.
Where does primary bone exist in adults?
Tooth sockets and tendon based bones
What do volkman's canals contain?
Blood vessels that enter the bone or originate in the marrow
What are the circumferential lamellae and where are they formed?
circumferential lamellae are formed by osteoblasts derived from the periosteum. These lamellae form an outer ring on the surface of a long bone.
What are the (3) types of joints?
What is synarthroidal?
Immovable Joint
What is amphiarthroidal?
Partially moveable
What is diarthroidal?
Completely moveable
What is a gomphosis joint?
Tooth socket joint
What is a suture joint?
Cranial vault joint
What is a syndesmosis?
are found between long bones of the body, such as the radius and ulna in forearm and the fibula and tibia in leg.
What is synchondrosis?
Boint joint connected by hyalin cartilage
What is a symphysis?
Fibrocartilage between bones. Vertebral, pubic
What type of joint provides the greatest ROM?
Ball and Socket
You should probably study more...
Name the content:
Name the joints and type:
No joints in dental school though
Name the parts of the osteon
Osteon parts are for sissies
What is the turnover of bones?
Every 7 years or so.
What is responsible for the increase in width of long bones?
appositional growth
How does mesenchymal cells know which type of connective tissue to become?
Local signaling environment
What is the major protein of bone?
Type I collagen, it's secreted by osteoblasts
What major protein does an osteoblast secrete?
Type I collagen
In terms of bone growth, what is the major hormone?
the major hormone is growth hormone from the hypophysis, and stimulates the liver to produce insulin-like growth factor.
What vitamin can have an impact on bone growth and remodeling?
Vitamin D allows Ca absorption in the gut and difficiencies of the former result in deficiency of the latter (rickets and osteomalacia)
How many nuclei are in osteoclasts?
Osteoclasts are multinucleated
How do osteoclasts resorb bone?
Secrete low pH (HCl) which leads to diffusion of minerals out of the bone.

The organic matter is degraded via endocytosis and fusion with lysosomes.
What does calcitonin do to osteoclats?
Calcitonin directly inhibits the activity of osteoclasts (limits Ca release)
What does parathyroid hormone do to osteoclasts?
Activates osteoclast activity (increases Ca release)
In endochondral ossification, _______________ replaces ______________.
Endochondral ossification occurs when hyaline cartilage is replaced with bone
State the (5) steps of endochondral ossification.
1. A hyaline cartilage "model" is formed.
2. Intramembranous bone is formed around the center of the diaphysis or shaft of the bone, and as a result the cartilage cells begin to hypertrophy and the cartilage matrix calcifies.
3. The center of the diaphysis is invaded by blood vessels and mesenchymal cells which differentiate into osteoprogenitor cells, and then osteoblasts.
4. Simultaneously with the resorption of the calcified cartilage matrix by osteoclasts, bone matrix is secreted by osteoblasts along other surfaces of the calcified cartilage matrix.
5. At both sides of the diaphysis, secondary ossification centers develop in the epiphyses (ends) of long bones. In between the diaphysis and the epiphysis is the epiphyseal plates (metaphysis), which is responsible for the longitudinal growth of the bone.
6. When bone ceases to grow in length, the epiphyseal plates "close" and disappear.
Endochondral bone formation is different from growth of a long bone. Describe the basic (3) steps of bone formation:
Endochondral bone formation is exclusively in terms of three steps:
Formation of the cartilage model
Calcify the cartilage
Form bone on the calcified cartilage
What takes place at the epiphyseal plate?
Osteoblasts differentiate on the surface of calcified cartilage and start making osteoid with colalgen type I and other noncallogenous proteins, and eventually osteoclasts eat it all up and its all replaced with new bone.

Osteoblasts line up on the cartilage and begin to make bone. The entire cartilage gets surrounded by a layer of bone. Cartilage is avascular, but when surrounded, they cannot undergo diffusion. Chondrocytes are killed off when surrounded by bone, and secrete a growth factor which causes blood vessels to grow into the cartilage. Marrow precursors come in with blood vessels, along with mesenchymal stem cells.

In a long bone, the pink is the layer of bone, and becomes the shaft (diaphysis), where osteoblasts differentiate. Perichondrium differentiates into periosteum. This starves out the inner purple region, and then blood vessels enter into this region. Calcified cartilage is replaced by bone. Between diaphysis and epiphysis, is the epiphyeal plate. Endochondral bone formation is the replacement of cartilage by bone.
Eventually bone growth will stop and there wont be an epiphysial plate

Growth of the bone afterward, depends on cartilage, and is interstitial growth of cartilage that occurs at the epiphysial plate, which is then replaced with bone.
What is intramembrous bone growth also called?
Appositional growth
How does increase in thickness of bone occur?
How does increase in length of long bones occur?
Via endochondral formation at the epiphyseal plate
What are the (6) zones that can be distinguished at the epiphysial plate?
Resting zone: cartilage cells, no mitosis.
Proliferative zone: cartilage cells are actively proliferating.
Maturation zone: cell division has ceased and the chondrocytes increase in size
Hypertrophy and calcification zone: the chondrocytes undergo hypertrophy and cartilage matrix becomes calcified
Cartilage degeneration: chondrocytes degenerate and the lacunae are invaded by osteogenic cells
Osteogenic zone: osteogenic cells differentiate inot osteoblasts , at metaphysis.
What side of the epiphyseal plate does bone growth occur?
The diaphesis side
How are most irregular bones formed?
Cortical via Appositional
How is cortical bone formed?
Appositional Growth
How is trabecular bone formed?
Endochondral Growth
What is osteoprotegrin?
Osteoclasts are controlled by osteoprotegerin, a non collagenous protein made by osteoblasts
Describe intramembrous ossification (picture):
What are the basic interactions between osteoclast and osteoblast?
What are the advanced interactions between bone, osteoclast, and osteoblasts?