Learn: Bone development, histology, structure and remodeling

Bone

What is the largest organ by weight

Axial and appendicular

What are the two divisions of the skeleton

Skull, auditory ossicles (ear bones), hyoid bones, ribs, sternum, bones of the vertebral column, and sacrum

What are the seven bones in the axial skeleton division

80

How many bones are in the axial skeleton

Bones of the upper and lower limbs and the bones forming the girdles (clavicle, ilium) that connect the limbs to the axial skeleton

What are the bones in the appendicular skeleton division

126

How many bones are in the appendicular skeleton

206;270

How many total bones are in an adult? At birth?

Long bone, short bone, irregular bone, sesamoid bone, flat bone

What are the 5 categories of bones based on shape

Maxilla and mandible

What are the two jaw bones

-50% organic: collagen, NCPs, proteoglycans, predominantly type 1 collagen

-50% inorganic mineral: hydroxyapatite

What is the chemical composition of bones

Minerals/hydroxyapatite crystals

What composition of the bone provides hardness/rigidity

Organic components/collagen

What composition of the bone gives the bone elasticity

-support

-protection

-movement

-mineral homeostasis

-blood cell production = hematopoietis (red bone marrow)

-triglyceride storage (yellow bone marrow)

-atypical endocrine organ

What are the 7 functions of the bone

Bones of the legs, pelvis, and vertebral column

What 3 bones hold up the body

Jaw bones

What bones support the teeth

Muscles

What do nearly all bones provide support for?

Soft organs

What can be directly or indirectly supported by nearby bones

Brain, spinal cord, lungs, heart, bone marrow

What 5 things do the bones enclose and protect

Eyes, ear organs, oral organs, pelvic organs

What other 4 things do the bones protect

The rigid attachment and leverage provided by bones

Skeletal muscle would serve no useful purpose if not for what?

Leg and arm movements

What are the most obvious examples of the movement function of bone

Movement of the ribs by skeletal muscles

What does ventilation of the lungs depend on

Red bone marrow

The major producer of blood cells in the bone

Red blood cells, most cells of immune system, and platelets

What three blood cells do the red bone marrow produce

Hematopoietic cells

What are the blood cells of the red bone marrow

Adipocytes

What are the fat cells of the red bone marrow

Megakaryocytes

What are the multinuclear cells that release platelets to stop bleeding

Bones

What is the body's main mineral reservoir

Calcium and phosphate

What do bones store and release according to the body's physiological needs

By absorbing or releasing alkaline mineral salts (calcium, phosphate)

How do bones buffer the blood against excessive pH changes in the blood

Triglycerides

What does yellow bone marrow store

Aged individuals

In which type of individuals does bone marrow contain more adipocytes/fat cells

The regulation and maintenance of the homeostasis of the whole body

In their endocrine organ role, bone cells synthesize and secrete proteins that act as growth factors/hormones that participate in what

Mesoderm

What do cells forming long bones originate from

Neural crest calls/ectomesenchyme

What do cells forming the jaw bones originate from

Ossification; intramembranous and endochondral

What is the term for bone development/formation? What are the two methods

Process of formation/ossification

What is the only difference between bones

Mesenchymal cells in dense connective tissue —> osteoblasts —> osteocytes/osteoid—> mineralized bone

What is the process of intramembranous ossification

intramembranous ossification

What type of ossification is the maxilla and major portion of the mandible

Woven bone consisting of trabeculae; lamellar bone replaces woven bone; forms cortical plate, red marrow appears

What type of bone is formed after blood vessels enter in intramembranous ossification? What replaces that? What does it form and what appears?

the formation of an ossification center containing osteoblasts in the fibrous connective tissue (not cartilage)

What does intramembranous ossification begin with

Osteoid matrix

What do osteoblasts deposit in intramembranous ossification

mature into osteocytes and become embedded in the osteoid, while mineral is deposited, forming bone (mineralized tissue).

What do osteoblasts mature into and what happens to them in intramembranous ossification

A random framework of bone (woven or immature bone)

What is formed surrounding embryonic blood vessels in intramembranous ossification

Periosteum on the outer surface

What forms from condensed fibrous connective tissue in intramembranous ossification

Lamellae

What organized sheets is bone formed into before they become mature lamellar bone

2 or more; fuse

How many ossification centers can be in one bone? What will they eventually do

Flat bones

What type of bones does intramembranous ossification occur in

Endochondral ossification

the formation of the osteoid within a hyaline cartilage model that subsequently becomes mineralized and dies

Mesenchymal cells —> chondrocytes producing cartilage model (template) —> blood vessels

grow into the model, inducing

osteoblast differentiation -> osteoblasts -> osteoid -> mineralized bone (bone replaces cartilage)

What are the steps of endochondral ossicfication

Formation of a cartilaginous model: mesenchymal cells differentiate into chondrocytes, which produce a cartilaginous model

What does endochondral ossification begin with? What is it?

Blood vessels penetrate the perichondrium, stimulating bone formation (osteoblasts -> osteoid -> mineralized bone)

During endochondral ossification what do the blood vessels penetrate? What does this stimulate

blood vessels grow into the model, inducing osteoblast differentiation, initiating formation of the primary ossification center

What initiates the formation of the primary ossification center

In epiphyseal ends via the same process as primary

Where do secondary ossification centers form

by hypertrophy and proliferation of chondrocytes under the metaphysis

How do long bones grow in length

Long bones

What type of bones form from endochondral ossification

Periosteal ridges

In endochondral ossification, from what does the growth in width come from

Growth plate/epiphyseal plate

What is essential for the lengthening of long bones

Ridges in periosteum create groove for

periosteal blood vessel -> periosteum ridges

fuse to become endosteum, forming an

endosteum-lined tunnel -> osteoblasts in

endosteum build new concentric lamellae

inward toward center of tunnel, forming a new

osteon -> bone grows outward as osteoblasts

in periosteum build new outer circumferential

lamellae

What are the steps of growth in width of bones

New osteon

What forms when new periosteal ridges fold in the growth in width of bones

Both endochondral and intramembranous ossification

What type of ossification is the growth in width used for

Woven/immature bone

What type of bone is primary bone

Lamellar/mature bone

What type of bone is secondary bone

Primary/immature/woven bone

What bone is initially produced by

either method of ossification

the

lamellae are indistinct because

of the irregular arrangement of

the collagen fibers and lamellae

Within primary bone, what are indistinct? Why?

Primary bone

What is the temporary tissue that is replaced by more mature secondary bone

secondarybone has a well-organizedarrangement ofcollagen fibers and distinct lamellae

What is the arrangement of collagen fibers and lamellae of the secondary bone

endochondral ossification

What type of ossification forms the head of the mandibular condyle

Multidirectional

What type of growth capacity does the head of the mandibular condyle

Intramembranous

What type of ossification is the body of the mandible

Bone

the hard and rigid form of connective tissue that constitutes most of the mature skeleton

soft tissue and as an attachment mechanism for skeletal muscles and other tissues

Bone serves as protective and structural support for what

Movement, manufactures blood cells

What does bone aid in through its red bone marrow

Is an energy bank

What is the bone do through its yellow marrow

Calcium and other minerals

What is bone a storehouse for

Alveolus as the alveolar bone proper

What does bone create when surrounding roots of a tooth

Epiphysis

Regions of long bone that is 'on top of/end'

metaphysis

Regions of long bone that is 'post'

Diaphysis

Regions of long bone that is 'passing through (shaft)/middle'

Growth

What does physis mean

Medullary

Region of long bone that is the 'innermost part/internal cavity'

Endosteum

Region of long bone that is the 'inside/inside surface of bone'

Periosteum

Region of long bone that is 'around, enclosing/outer surface'

Vascularized with its own blood supply

Why does bone repair quickly

it does not consist of an

inanimate inner rod being moved by the

skeletal muscles. Instead, it is a living and

functioning tissue in the body.

Even though bone is rigid, what is important to remember

Bone

What undergoes the most developmental differentiation of all connective tissue

Periosteum

The outer part of the bone is covered by what

Periosteum

a double-layered, dense

connective tissue sheath.

blood vessels, nerves and fibroblasts.

What does the outer layer of the periosteum contain

a single layer of cells that give rise to bone-forming cells, the osteoblasts.

What does the inner layer of the periosteum contain

Compact bone

A dense layer deep to the periosteum

Spongy/cancellous/trabecular bone

What is deep to the compact bone

same cellular components, but each has a different arrangement of those components.

Compact and cancellous bone have the same what? Different what?

the relative amount of solid bone and the size and number of soft tissue spaces in each

What are two differences between compact and cancellous bone

No

Is there a sharp boundary between compact and cancellous bone

Endosteum

What lines the medullary cavity of bone on the inside of the layers of compact bone and cancellous bone

Periosteum but is thinner

What does the Endosteum have the same composition as?

Bone marrow

What is on the innermost part of the bone in the medullary cavity

the stem cells of the blood are located, lymphocytes are created, and B cells mature.

What 3 things happen in the bone marrow

calcium hydroxyapatite ( Ca10(PO4)6(OH)2 )

-in differing percentages in the hard dental tissue, such as enamel, dentin, and cementum.

What inorganic substance in a crystalline formation gives bone its hardness? Where else is it found?