Connective tissue 3

Question 1

What is special about the matrix of bone cells?

Does bone have an outer fibrous periosteum?

Answer 1

It is infiltrated w/ inorganic salts to make it rigid and inflexible.

Yes it has a periosteum and it is HIGH VASCULAR

Question 2

What are functions of bone?

Answer 2

Leverage, Attachment, Mineral storage, Protection, Support

Mneumonic: LAMPS

Question 3

What is inside the marrow cavity?

Answer 3

Blood (red), Fat (yellow and is in older ppl), and spongy bone (aka cancellous bone)

Question 4

What are caniculi?

Answer 4

Cytoplasmic extensions that traverse the matrix from one osteocyte to others.

Question 5

Osteoprogenitor cells are derived from ____.

Answer 5

Primitive mesenchymal cells.

Question 6

How is the matrix (aka osteoid) produced?

Answer 6

Osteoblasts produce the osteoid, but when they become ‘imprisoned’ by the matrix they are called OSTEOCYTES, which are responsible for maintaining the matrix composition.

Question 7

What are osteoclasts?

Answer 7

They are multinucleated macrophages that remodel bone. They are derived from phagocytic monocytes.

Question 8

What is the osteoid (ie bone matrix) made of?

Answer 8

Organic material: Type I collagen (95% of organic portion), GAGs, and glycoproteins.

Inorganic material: Hydroxyapatite crytals: calcium (99% of body’s store of calcium), and others

Question 9

What is an osteon?

Answer 9

AKA Haversian system, it is the fundamental functional unit of much compact bone.

(Looks like a tree trunk)

Question 10

How is compact bone formed?

Answer 10

Formed by appostional growth (ie thickening of the bone).

It is surrounded by a CT layer aka PERIOSTEUM, and the inner layer of cells are aka OSTEOprogenitor

Question 11

What increases and decreases osteoclast activity (which is to remodel bones)?

Answer 11

Osteoclast activity is increased by Parathyroid Hormone (PTH) and decreased by Calcitonin action

Question 12

What type of CT is the periosteum made from?

Answer 12

Dense irregular CT

Question 13

What is the difference b/w appositional growth and endochondral growth?

Answer 13

Appositional growth from the periosteum increases in DIAMETER,

Endochondral growth increases in LENGTH

Question 14

Where does intramemranous bone formation occur?

How does the process go?

Answer 14

In the fetus, from mesenchymal tissue.

Osteoprogenitor cells develop, form osteoblasts which lay down osteoid which calcifies.

Question 15

What are the 3 parts of a long bone?

Answer 15

Epiphysis (outer), metaphysis(in b/w outer and middle of bone), and diaphysis (middle of bone)

Question 16

Describe the process of endochondral bone formation

Answer 16

The fetal cartilage primordium already has the general shape of the bone to be formed (long bones and ribs). Bone begins to replace cartilage in DIAPHYSIS region.

Osteoprogenitor cells>osteoblasts>osteoid>bony collar around cartilage model>perichondrium becomes periosteum

Question 17

Where are the primary and secondary ossification centers?

Answer 17

Primary ossification center is in diaphysis part,

Secondary ossification center is in epiphysis.

Question 18

Where and what is the epiphyseal plate?

Answer 18

It is a hyaline cartilage plate in the metaphysis of each long bone.

There is cartilage there to allow for further growth.

Question 19

What are the 5 zones of a growing bone?

Which of the 5 is the only one that’s not cartilaginous?

Answer 19

1. Resting (Quiescent) zone
2. Proliferative zone
3. Zone of hypertrophy
4. Zone of cartilage calcification
5. Zone of ossification (only one that’s not cartilaginous)

Question 20

What are the major distinguishing characteristics of the 5 zones of a growing bone?

Answer 20

1. Resting: no mitosis (ie few cells)
2. Proliferative: high mitotic rate(looks like coin stacks)
3. Hypertrophy: cells and lacunae enlarge
4. calcification:cartilage becomes calcified (usually dark purple or black color appears)
5. Ossification: Osteoblasts align spicules of calcified cartilage and lay down osteoid around osteoblasts forming osteocytes

Question 21

When does endochondral growth occur? and how?

Answer 21

It occurs during youth, throughout childhood w/ an even growth of cartilage and bone.

During puberty, increased levels of sex hormone induce more bone growth. At age 19-20, bone growth on either side of epiphyseal plate meets leaving the EPIPHYSEAL LINE or SYNOSTOSIS) and growth stops.

Question 22

Describe the differences b/w:

1. Intramembranous ossification
2. Endochondral ossification
3. Endochondral bown growth

Answer 22

1. converts mesenchyme to bone in pre- and perinatal period (primary ossification centers) NOTE: Cartilage is NOT involved (bones in skull, ribs, jaw)
2. Converts cartilage to bone in pre/perinatal period (primary and secondary ossification centers)
3. Occurs after birth, lengthening of long bones, requiring epiphyseal plate, ceasing at adulthood.