Bone-Alex Flashcards
What type of CT is bone?
specialized
Bone can be _ or _
compact or spongy
What is compact and spongy bone made up of?
Compact: made of osteons
Spongy: trabeculae
What is bone covered by?
Periosteum> dense irregular CT
Mineralied matrix is made up of what?
Calcium phosphate (hydroxyapatite crystals)
KNOW BOTH TERMS
What are the matrix components?
- Calcium phosphate (hydroxypatite crystals)
- Type I collagen> produced by osteoblasts
- Ground substance= PG+GAGs (keratin/chondroitin sulfate)+glycoproteins (laminin and fibronectin
- What is the end of the long bones called?
- What are they made up of?
- What do they contain
- Epiphysis
- Made up of spongy bone
- Contains red marrow> produce RBCs
- What is the epiphyseal line?
- What is it made up of ?
- Growth plate
- made up of hyaline cart> replaced with compact bone
- What is the shaft of long bones?
- What is it made up of?
- What does it contain?
- The shaft of long bones
- made up of compact bone
- contain the medullary cavity=site of BM
What type of tissue is periosteum?
dense irregular CT
Bone marrow can be _ or _
red or yellow
Red: RBCs
Yellow: adipose cells-> only in adults
What is the layers of the bone from outer to inner?
- Periosteum
- Compact bone
- Endosterum
- Bone Marrow
Compact bone is made up of what?
lamellae=rings of thin bone
* Outer circumferential lamellae
* Haversian systems
* inner circumferential lamellae
- What is the haversian system?
- What is it made up of?
- What cells does it contain?
- Lamellae around a central canal
- Made up of osteons=lamellae around haverian canal
- Contains osteoblasts (or osteoclasts if remodeling)
What is haversian cannals and volkmann canals
- Haversian: run parallel to the axis of bone
- Volk: runs perpendicular to connect systems
- What is endosteum?
- What cell does it contain?
- inner CT lining the medularry cavity
- Contain osteoblasts
What is the basic unit of compact bone?
- osteons=lamellae (rings of thin bone) around a central (haverian) canal
What are canaliculi?
What is the purpose?
- Small tunnels in the bone matrix
- Connect neighboring cells in lacunae for cell-cell communication via gap junctions
How do we end up with partial lamellae ?
- As bone remodels, parts of the haversian system get resorbed+replaced so it results in partial lamelaae (w/o haversian canal)
- What does osteoblasts secrete?
- Mitoically active?
- type one collagen fibers
- yes, further divide to form osteocytes and more osteoblasts
- What is osteocytes housed in?
- What is their fxn?
- Mitotically active?
- Lacunae surrounded by matrix
- Maintain bone matrix and help resorb Ca2+ into the blood with PTH
- NO because they are fully differentiated
- What is the fxn of osteoclasts?
- What is it housed in?
- Bone remodeling cells
- Housed in Howship’s lacunae with enzymes to digest bone
clasts are fully differentiated
- What activates and inhibits osteoclasts?
- What happens to the Ca2+?
- PTH activates clasts-> increases Ca2+
- Calcitonin inhibits clasts->decreases blood Ca2+
Osteoclasts digest bony matrix of an area->
resorption bay
What follows behind clasts?
What does it deposit?
- Osteoblasts
- deposit new bony matrix
Where does intramembranous bone formation happen?
- occurs in mesenchyme (embryonic CT)> mesenchymal cells turn into osteoblasts
Explain the intramembranous bone formation?
- 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
Where does endochondral bone formation occurs?
hyaline cartilage-> mesenchymals cells turn into osteoblasts
Explain endochondral bone formation
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
explain endochondral ossification
- Perichondrium gets vascularized-> periosteum
- Mesenchymal cells surrounding hyaline cartilage differentiate into osteoblasts
- Ostroblasts (near diaphysis) cover cartilage w/bony matrix (osteoid)->forms bony collar
- Chondrocytes hypertrophy-> secrete alkaline phosphate-> calcifies cartilage-cells dies
- Osteoclasts erode the calcified cartilage-> produce holes where vessels invade-> forms periosteal bud
- Osteoblasts secrete bony matrix (osteoid) around remaining cartilage-> forms traceculae
- Clasts resorb bone (breakdown trabeculae)-> leaves an enlarged cavity for marrow
- Final stage is marked by the appearance of secondary ossification centers @epiphysis
Explain fracture healing
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
