Bone-Alex

Question 1

What type of CT is bone?

Answer 1

specialized

Question 2

Bone can be _ or _

Answer 2

compact or spongy

Question 3

What is compact and spongy bone made up of?

Answer 3

Compact: made of osteons
Spongy: trabeculae

Question 4

What is bone covered by?

Answer 4

Periosteum> dense irregular CT

Question 5

Mineralied matrix is made up of what?

Answer 5

Calcium phosphate (hydroxyapatite crystals)

KNOW BOTH TERMS

Question 6

What are the matrix components?

Answer 6

• Calcium phosphate (hydroxypatite crystals)
• Type I collagen> produced by osteoblasts
• Ground substance= PG+GAGs (keratin/chondroitin sulfate)+glycoproteins (laminin and fibronectin

Question 7

• What is the end of the long bones called?
• What are they made up of?
• What do they contain

Answer 7

• Epiphysis
• Made up of spongy bone
• Contains red marrow> produce RBCs

Question 8

• What is the epiphyseal line?
• What is it made up of ?

Answer 8

• Growth plate
• made up of hyaline cart> replaced with compact bone

Question 9

• What is the shaft of long bones?
• What is it made up of?
• What does it contain?

Answer 9

• The shaft of long bones
• made up of compact bone
• contain the medullary cavity=site of BM

Question 10

What type of tissue is periosteum?

Answer 10

dense irregular CT

Question 11

Bone marrow can be _ or _

Answer 11

red or yellow

Red: RBCs
Yellow: adipose cells-> only in adults

Question 12

What is the layers of the bone from outer to inner?

Answer 12

1. Periosteum
2. Compact bone
3. Endosterum
4. Bone Marrow

Question 13

Compact bone is made up of what?

Answer 13

lamellae=rings of thin bone
* Outer circumferential lamellae
* Haversian systems
* inner circumferential lamellae

Question 14

• What is the haversian system?
• What is it made up of?
• What cells does it contain?

Answer 14

• Lamellae around a central canal
• Made up of osteons=lamellae around haverian canal
• Contains osteoblasts (or osteoclasts if remodeling)

Question 15

What is haversian cannals and volkmann canals

Answer 15

• Haversian: run parallel to the axis of bone
• Volk: runs perpendicular to connect systems

Question 16

• What is endosteum?
• What cell does it contain?

Answer 16

• inner CT lining the medularry cavity
• Contain osteoblasts

Question 17

What is the basic unit of compact bone?

Answer 17

• osteons=lamellae (rings of thin bone) around a central (haverian) canal

Question 18

What are canaliculi?
What is the purpose?

Answer 18

• Small tunnels in the bone matrix
• Connect neighboring cells in lacunae for cell-cell communication via gap junctions

Question 19

How do we end up with partial lamellae ?

Answer 19

• As bone remodels, parts of the haversian system get resorbed+replaced so it results in partial lamelaae (w/o haversian canal)

Question 20

• What does osteoblasts secrete?
• Mitoically active?

Answer 20

• type one collagen fibers
• yes, further divide to form osteocytes and more osteoblasts

Question 21

• What is osteocytes housed in?
• What is their fxn?
• Mitotically active?

Answer 21

• Lacunae surrounded by matrix
• Maintain bone matrix and help resorb Ca2+ into the blood with PTH
• NO because they are fully differentiated

Question 22

• What is the fxn of osteoclasts?
• What is it housed in?

Answer 22

• Bone remodeling cells
• Housed in Howship’s lacunae with enzymes to digest bone

clasts are fully differentiated

Question 23

• What activates and inhibits osteoclasts?
• What happens to the Ca2+?

Answer 23

• PTH activates clasts-> increases Ca2+
• Calcitonin inhibits clasts->decreases blood Ca2+

Question 24

Osteoclasts digest bony matrix of an area->

Answer 24

resorption bay

Question 25

What follows behind clasts? What does it deposit?

Answer 25

* Osteoblasts * deposit new bony matrix

Question 26

Where does intramembranous bone formation happen?

Answer 26

* occurs in mesenchyme (embryonic CT)> mesenchymal cells turn into osteoblasts

Question 27

Explain the intramembranous bone formation?

Answer 27

* Osteoblasts secrete boney matrix (=**osteoid**)-> creates bony spicules * As boney spicyles enlarge, they become interconnected-> forming **trabeculae** * The newly developed bone expands by appostitional growth (i.e. mediated bone growth)-> bone is added to the surface; this is the only way bone grow

Question 28

Where does endochondral bone formation occurs?

Answer 28

hyaline cartilage-> mesenchymals cells turn into osteoblasts

Question 29

Explain endochondral bone formation

Answer 29

**hyaline cartilage-> mesenchymals cells turn into osteoblasts @ bony collar near diaphysis** * The bony collar is formed by intramembranous bone formation via osteoblasts * The bony collar cuts off supply to the cartilage, thus the chondrocytes die **Chondrocytes within the cartilage hypertrophy-> secrete alkaline phoshate-> then calcify** **Osteoblasts cover the calcified cartilage w/its own unclacifed bony matrix (=osteoid)** * Calcified cartilage stains purple * osteoid stains pink

Question 30

explain endochondral ossification

Answer 30

1. Perichondrium gets vascularized-> periosteum 2. Mesenchymal cells surrounding hyaline cartilage differentiate into osteoblasts 3. Ostroblasts (near diaphysis) cover cartilage w/bony matrix (osteoid)->forms bony collar 4. Chondrocytes hypertrophy-> secrete alkaline phosphate-> calcifies cartilage-cells dies 5. Osteoclasts erode the calcified cartilage-> produce holes where vessels invade-> forms periosteal bud 6. Osteoblasts secrete bony matrix (osteoid) around remaining cartilage-> forms traceculae 7. Clasts resorb bone (breakdown trabeculae)-> leaves an enlarged cavity for marrow 8. Final stage is marked by the appearance of secondary ossification centers @epiphysis

Question 31

Explain fracture healing

Answer 31

Step 1: Hematoma formation * Blood clot forms+ cells deprived of nutrients die Step 2: fibrocartilage callus formation * capillaries form+deliver fibroblasts to the area * Collagen fibers close the fractured bone * Fibroblasts turn into chondrocytes-> produces cartilage * cartilage undergoes bone formation process Step 3: bony callus formation * Osteoblasts create trabeculae-> forms spongy bone Step 4: bone remodeling * Osteoclasts+ blasts replace spongy bone with compact bone