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Anatomy & Physiology Lecture > Block 2: Skeletal System - Lecture 2.4 > Flashcards

Block 2: Skeletal System - Lecture 2.4 Flashcards

1
Q

What is Bone Modeling?

A

Construction of bone by Osteoblasts without prior bone resorption
a. occurs during growth
b. produces changes in bone size and shape

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2
Q

What is Bone Remodeling?

A

Reconstruction of bone that is first resorbed by Osteoclasts and then formed in the same locations by Osteoblasts
a. happens throughout entire life
b. maintains healthy skeletal tissue

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3
Q

What are the 2 major goals of Bone Modeling and Remodeling?

A
  1. Achieve strength for loading
    a. response to mechanical stressors
    b. peak skeletal strength comes from bone modeling
  2. Maintain lightness for mobility
    a. keeps strength in response to life experiences from bone remodeling
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4
Q

What are the 2 types of Bone Modeling?

A

Intramembranous Ossification: in membrane
Endochondral Ossification: from cartilage

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5
Q

What is Osteogenesis?

A

Bone formation throughout the body

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6
Q

Why are newborns born with about 100 more bones that a full grown adult?

A
  • Facilitates brain growth
  • Soft spots (not yet calcified) allow passage through birth canal
  • Growth is not complete when born
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7
Q

What are the major differences between Prenatal and Postnatal Osteogenesis?

A

Prenatal:
a. Intramembranous Ossification: from mesenchyme
b. Endochondral Ossification: hyaline cartilage to bone

Postnatal:
a. Increase length (longitudinal growth)
b. Increase width (appositional growth)

sometimes sesamoid bones form

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8
Q

How does Intramembranous Ossification start?

A

2 ways:
a. with mesenchymal tissue (forms all CT)
b. with underdeveloped fibrous CT

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9
Q

What are some examples of bones that are formed through Intramembranous Ossification?

A

Cranial Bones, most Facial Bones, and parts of Clavicles

Creates layers: compact –> spongy –> compact

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10
Q

What is the first step in Intramembranous Ossification?

A

Mesenchymal cells form many ossification centers
a. mesenchymal cells congergate in areas with lots of blood vessels to increase tissue to bring nutrients signals, etc.

Process:
mesenchymal cells line blood vessels –> differentiation into osteogenic cells –> osteoblasts (can make proteins) –> secreting osteoid (organic: collagen fibers & GAGs)

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11
Q

What is the second step in Intramembranous Ossification?

A

Calcium salts crystallize on osteoid
a. forms spicules

Process:
calcium salts (brought by osteoblasts) crystallize on osteoid –> calcification –> formation of spicules –> some osteoblasts get trapped and differentiate into osteocytes

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12
Q

What is the third step in Intramembranous Ossification?

A

Mesenchyme differentiates
a. forms periosteum (outside of bone)

Process:
mesenchymal differentiation –> formation of periosteum –> all ossification centers meet –> formation of branching plates (trabeculae)

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13
Q

What is the fourth step in Intramembranous Ossification?

A

Osteoblasts form Compact Bone Layers

Process:
osteoblasts within periosteum create outside layers of compact bone –> continuation of remodeling spongy bone by osteoblasts & osteoclasts

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14
Q

What are the four basic steps to Intramembranous Ossification?

A
  1. Mesenchymal cells form many ossification centers
  2. Calcium salts crystallize on osteoid
  3. Mesenchyme differentiates
  4. Osteoblasts form Compact Bone Layers
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15
Q

What disease is a special form of Intramembranous Ossification?

A

Heterotropic Bone Formation
a. abnormal stresses stimulate bones to form where they shouldn’t
b. classified as sesamoid bones

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16
Q

What are the key differences between calcification and ossification?

A

Calcification: depositing of calcium
Ossification: replacement of CT by bone tissue

Calcification is a part of Ossification

17
Q

How does Endochondral Ossification start?

A

Hyaline Cartilage

18
Q

What bones are formed through Endochondral Ossification?

A

Most bones below the skull: humerus, femur, vertebrae, etc.
a. long bones develop diaphysis, epiphyses, and medullary cavity

19
Q

What is the first step to Endochondral Ossification?

A

Mesenchyme differientiates into hyaline cartilage
a. covered by the perichondrium, creating a boundary for the cartilage

20
Q

What is the second step to Endochondral Ossification?

A

Formation of a single primary ossification center
a. in the middle of future diaphysis

Process:
increased vasculature/blood flow –> brings nutrients, chemical signals, and osteogenic cells –> osteoblast formation (before matrix) –> perichondrium –> periosteum –> bony collar formation –> matrix begins to calcify –> chondrocytes at primary ossification center grow in size –> no diffusion of nutrients –> chondrocyte death leaves behind large cavities

21
Q

What occurs as the first portion of step three in Endochondral Ossification?

A

Periosteal bud causes primary medullary formation
a. includes nutrient artery/vein, nerve fibers, osteogenic cells, and osteoclasts

Process:
periosteal bud invades medullary cavity –> cavity remodeling via osteoblasts & osteoclasts –> spongy bone formation –> primary medullary cavity formation

22
Q

What occurs as the second portion of step three in Endochondral Ossification?

A

Secondary ossification center(s) form
a. chondrocytes go through similar process as chondrocytes for the primary ossification center
b. separated by epiphyseal plate

23
Q

What is the fourth step in Endochondral Ossification?

A

Secondary medullary cavities form in epiphyses
a. one secondary center will be delayed
b. most long bones have 2 secondary centers
c. more distal center = faster growth

24
Q

What is the fifth step in Endochondral Ossification?

A

Further growth
a. when growing the epiphyseal plate will ALWAYS be cartilage (no cartilage in adult bones = growth plates!)

Process:
increase cartilage at joints and epiphyseal plate –> ossification

25
Q

What are the key differences between Primary Ossification and Secondary Ossification in Endochondral Ossification?

A

Primary Ossification:
a. marrow cavity formed
b. replaces all cartilage with bone
c. located in diaphysis
d. occurs before birth

Secondary Ossification:
a. no marrow cavity
b. some cartilage left for epiphyseal (growth plates) plates and articular cartilage
c. located in epiphyses
d. occurs around the time of birth

Anatomy & Physiology Lecture (13 decks)

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