Histology: Bone (Exam 2) Flashcards
How is the connective tissue of bone characterized by
mineralized extracellular matrix
What is the ECM of bone composed of
Hydroxyapatite crystals
Collagen I
Glycoproteins
What glycoproteins are found in bone
osteocalcin
osteonectin
osteopontin
What cells is bone composed of
osteocyte
osteoblast
osteoprogenitor cells
osteoclast
What is the function of bone
support
protect
storage for calcium and phosphate
What are the histological components of bone
bone tissue hemopoeitic tissue fat tissue Dense CT vessels nerves endosteum
Where is hemopoeitic tissue found
in the red bone marrow in the epiphysis
Where is fat tissue found
yellow bone marrow of the shaft
Where is dense connective tissue found
outer fibrous layer of periosteum
What are the fibers of the periosteum that extend into the bone called
Sharpey’s fibers
What is the endosteum
covers the inner surface of the marrow cavity
What cells are found in the endosteum
osteoprogenitor or endosteal cells
What is the function of osteoprogenitor cells
differentiate into osteocytes
What are the two types of bone
compact bone
spongy bone
Where is compact bone found
within the shaft
Where is spongy bone found
forming trabeculae
What are the different classifications of bone, based on shape
long bone
short bone
flat bone
irregular bone
What is a haversian lamellae
concentric lamellae surrounding a haversian canal
What do the concentric lamellae surrounding a haversian canal form
cylindrical units called osteon or haversian systems
What is the axis of the haversian system parallel with
the shaft
What is contained within a haversian canal
vessels and nerves
What is a Volkmann’s canal
horizontal canal leading from one haverian canal to another
Where are osteocytes found
in lacunae between the lamellae
What are canaliculi
hair like canals that connect lacunae to each other and the central canal
What are canaliculi formed from
osteocytes
What is interstitial lamellae
old haversian systems found between osteons and fill the space
What is the outer circumferential lamellae
lining on the outer surface of bone under periosteum
What is the inner circumferential lamellae
lining on inner sruface of bone under the endosteum
Where is immature bone found
skeleton of developing fetus, adult alveolar sockets, and tendon attachments
What is immature bone composed of
nonlamellar bone composed of interlacing collagen fibers
Describe the appearance of immature bone
more cell rich than mature bone
cells randomly arranged
What is the matrix of immature bone compared to mature bone
less mineralized with more ground substance than mature bone
What does immature bone stain and why
basophilic due to more ground substance
What type of bone will lack osteons
immature bone
What is the periosteum
collagenous membrane on the outer surface of bone
What does the periosteum contain
vessels, nerves, and nociceptors
What are the two layers the periosteum is composed of
fibrous outer layer
inner osteogenic layer
What composes the fibrous outer layer of the periosteum
Dense irregular CT
What composes inner osteogenic layer of the periosteum
osteoprogenitor cells
What does the endosteum cover
covers the marrow cavity
What does the endosteum contain
osteoprogenitor cells
What is the structure/appearance of osteoprogenitor cells
flattened cells that resemble fibroblasts
What type of staining of the cytoplasm do osteoprogenitor cells stain
basophilic
What is the location of osteoprogenitor cells
inner layer of periosteum
endosteum
lining haversian and volkmann’s canals
What will osteoprogenitor cells differentiate into
osteoblasts
What is the function of osteoblasts
form chondroblasts, adipocytes, and fibroblasts
appositional bone formation
What do osteoblasts eventually become
osteocytes
What do osteoblasts secrete
collagen and ground substance that forms the initial unmineralized bone
What is the initial unmineralized bone called
osteoid
What is an osteocyte
bone cell
How are osteocytes formed
when an osteoblast becomes embedded in the matrix it has secreted
Where are osteoblasts found
form a single cuboidal cell layer on the surface of the growing bone, sitting on a light band of osteoid
What do osteoblast cytoplasm stain
basophilic due to rER
How is the calcification process of bone initiated
osteoblasts secreting vesicles containing alkaline phosphatase
What is the function of osteocytes
maintain the bone matrix
The death of an osteocyte results in what
reabsorption of bone
How do osteocytes communicate
via gap junction
Where are the gap junctions in osteocytes
canaliculi connect lacunae in which the osteocytes sit
What are the different types of osteocytes
Inactive (quiescent)
Formative
Resorptive
What type of organelles does an inactive osteocyte have
few organelles
What type of organelles does a formative osteocyte have
rER
What type of organelles does a resorptive osteocyte have
lysosomes
What is the structure of osteoclasts
large multinucleated acidophilic cells, nuclei sitting on the side of the cells further away from the bony trabecula
Where in the bone can you find osteoclasts
sitting on the ruffled border, contacting the bone
What is the function of osteoclassts
resorb bone matrix, releasing minerals back into the blood
What do osteoclasts release to aid in their function
lysosomal hydrolases and organic acids that digest organic components and decalcify the underlying bone
What is the name for where osteoclasts are found
Howship’s lacunae: resorption bay
What disease can result in increased osteoclast activity
hyperparathyroidism
How does hyperparathyroidism result in increases osteoclast activity
increases PTH increases osteoclast activity
What decreases osteoclast activity
calcitonin
What occurs during intramembraneous ossificiation
Mesenchymal cells aggregate–turn into osteoblasts and secrete osteoid
Osteoid will minerlize and osteoblasts will be surrounded by lacunae and become osteocytes
Is cartilage involved in intramembraneous ossification
nope
Where does intramembranous ossification occur
embryo skull bone and in fractures where the broken ends are very closely aligned
What is the process of endochondral ossification
Hyaline cartilage models of bone
perichondrium forms a bony collar around the cartilage model (appositional growth)–> periosteum
Primary ossification center develops
Capillary roots break into the bone carrying osteoprogenitor cells that settle on the surface of the remaining calcified cartilage trabecules and turn into osteoblasts
Osteoblasts build up the bone
secondary ossification centers: capillary loops break into the epiphysis
remaining epiphyseal plate forms bone towards the opposite directions lengthening the bone
What are primary ossification centers
chondrocytes in the middle of the model become hypertrophic, secrete alkaline phosphatase, and the surrounding matrix undergoes calcification
calcified matrix inhibits diffusion of nutriets–death of the suicidal cells
death of chondrocytes the matrix breaks down forming a cavity
When does bone via endochondral ossification untimately calcify
age in the 20s
What is the epiphyseal plate
flat plate of hyaline cartilage seen in young, growing bone
What are the layers of endochondral ossification
- Zone of reserve cartilage
- zone of proliferation
- zone of hypertrophy
- zone of calcified cartilage
- zone or resportion
What is the zone of proliferation look like
cartilage cells are arranged into rows
What type of growth will increase diameter of bone
appositional growth
Where does appositional growth occur
periosteum
