Cartilage/Bone Histology Flashcards
Three components of the connective tissue cartilage
Cells, fibers, and matrix
Cells which produce and maintain cartilage
chondrocytes
Precursor to chondrocytes
chondroblasts
Two types of fibers typically found in cartilage
collagen or elastic fibers
Two components of extracellular matrix found around cartilage
hyaluronic acid and glycosaminoglycans (GAGs)
What can be said about the nutrient supply to cartilage?
the tissue is avascular
Three functions of cartilage
1) provides support for soft tissues
2) resists compression, acting as a shock absorber
3) template for bone development
Three types of cartilage
1) hyaline
2) elastic
3) fibrocartilage
Found in the developing skeleton of an embryo. Makes up the epiphysial plate (growth plate) of growing bones. Found in the respiratory tract and also called articular cartilage.
Hyaline cartilage
Type of cartilage found in the ear, epiglottis, and eustachian tube.
Elastic cartilage
Type of cartilage found in intervertebral disks, meniscus of the knee, mandible, sternoclavicular joints, and the pubic symphysis
fibrocartilage
Structure containing capillaries to supply chondrocytes of avascular matrix with nutrients
fibrous perichondrium
What type of connective tissue is the fibrous layer of the perichondrium?
dense irregular connective tissue
Most common type of cartilage
hyaline
Cartilage type with glassy appearance. Features type II collagen, proteoglycans, and water. Resists compression and provides a smooth surface for joints. Has a perichondrium layer.
Hyaline Carilage
What is different about the articular cartilage subtype of hyaline cartilage?
It has no perichondrium (in general, no perichondrium if next to bone/joint)
Types of cartilage growth (2)
1) appositional growth
2) interstitial growth
cartilage growth type where cells from the inner layer of perichondrium differentiate into chondroblasts. Matrix is deposited next to existing matrix.
Appositional growth
cartilage growth type where growth of chondroblasts by mitosis occurs within the cartilage matrix. New territorial matrix is deposited. Forms isogenous (all formed through division of a single progenitor cell) groups
interstitial growth
Cartilage type with fibers which make it much more flexible so it can bend without breaking. The matrix has collagen II and it is surrounded by perichondrium
Elastic cartilage
Cartilage type which has Type I and II collagen in a dense regular pattern. Cells (chondrocytes and fibroblasts) grow in rows. Provides tensile strength to resist compression and stretching. No perichondrium
fibrocartilage
Appearance of cartilage on x-ray
Radiolucent (black)
Functions of bone (5)
1) weight bearing
2) attachments for muscle
3) protection for internal organs
4) site of hematopoiesis
5) reservoir for minerals
unmineralized, organic portion of the bone matrix that forms prior to the maturation of bone tissue
Osteoid
Components of osteoids (3)
1) Type 1 Collagen Fibers
2) proteoglycans
3) Non-collagenous proteins
Non-collagenous proteins in osteoids (4)
1) osteopontin
2) osteocalcin
3) osteonectin
4) bone sialoprotein
Inorganic component of bones
Hydroxyapatite (calcium phosphate)
Proximal and distal ends of the long bones adjacent to physis (growth plate) or physis remnant (epiphyseal line)
epiphysis
Region adjacent to growth plate where bone deposition occurs
metaphysis
Shaft of the bone. Has medullary cavity with marrow.
diaphysis
Dense bone on the outside of long bones. Arrange in lamellae (osteons)
Compact bone
Less dense bone which lines marrow cavities and at the ends of long bones. Arranged in trabeculae (spicules) to create more surface area.
Cancellous (spongy or trabecular) bone
Contains concentric layers of cells (lamellae) and matrix around a central canal. Bone type
compact bone
Contains irregular arrangement of cells and matrix forming trabeculae. Bone type.
Cancellous bone
series of microscopic tubes in the outermost region of bone called cortical bone that allow blood vessels and nerves to travel through them
haversian canal
Composed of the lamellae (rings) surrounding a haversial canal and the canal itself. Maintained by a single capillary in haversian canal.
Osteon (Haversian System)
Osteons run lengthwise of widthwise in a bone?
lengthwise
Found on the outer and inner surface of compact bone
Circumferential lamellae
Partial osteons in the middle of the compact bone. Remnants of former osteons from remodeling process
Interstitial lamellae
Canal that runs transversely across the long axis of the bone (across width). Carry capillaries that interconnect longitudinal haversian capillaries or carry capillaries into the bone from periosteum
Volkmann’s Canal
Stem cells that give rise to osteoblasts.
Osteoprogenitor Cells
Where are osteoprogenitor cells found?
Line the bone in the periosteum and endosteum
Cuboidal epithelial like cells. Form new bone. Secrete osteoid and contribute to mineralization.
Osteoblasts
Osteoblasts that become trapped in osteoid. Reside lacunae. Highly branched cells with processes connected to others (of the same cell type) through canaliculi. Contribute to Ca2+ homeostasis
Osteocytes
Multinucleated osteoclasts are derived from what cell lineage?
monocytes
What reside in Howship’s lacunae (small cavities in degrading bone)
osteoclasts
How do osteoclasts breakdown bones during remodeling?
Create acidic environment that causes demineralization (H+-ATPase). The organic components are degraded enzymatically.
True/False: Osteoclasts are hormone sensitive?
true
Single layer of cells lining inner bony surfaces
endosteum
Two mechanisms of bone formation
1) intramembranous
2) endochondral
Bone formation mechanism where it forms directly in the mesenchyme and drives appositional growth of long bones (widens them). Process used to form skull, parts of mandible and clavicles
intramembranous
Bone formation mechanism in which it forms in a cartilage template. This is the process used to form long bones.
Endochondral
What do both bone formation mechanisms begin with?
Forming trabeculae of spongy bone. Later it’s remodeled into compact bone.
Pluripotent stem cells which can form fibroblasts, chondroblasts, and osteoblasts
Mesenchymal cells
What do aggregates of mesenchymal cells differentiate into in intramembranous ossification
osteoblasts
Intramembranous ossification. Osteoblasts secrete osteoid to form what?
ossification center
In intramembranous ossification, ossification centers enlarge and fuse to form…
trabeculae.
They then continue to enlarge by appositional growth and calcium phosphate is deposited in the osteoid.
Why does the medullary cavity expand in appositional growth?
osteoclasts break down the inside
Bones of the extremities, vertebral column and pelvis grow with which mechanism?
endochondral ossification
What forms first in endochondral ossification?
hyaline cartilage template
[Endochondral Ossification] Chondrocytes at the site of a _____ _____ _____ secrete factors that induce the growth of blood vessels from the perichondrium.
primary ossification center
What happens to chondrocytes as the matrix calcifies in endochondral ossification
apoptosis
Interstitial growth of the cartilage increases…. (Endochondral ossification)
the length of the template
Where does cartilage remain after maturation of bones (2)
1) articular surface
2) epiphyseal plate
First bone formed is immature or _____ bone. Collagen fibers in random orientation, more ground substance, less mineralization.
woven bone
When does dense immature woven bone get remodeled into mature lamellar bone? Here you see formation of lamellae with collage fibers in regular spiral bundles.
Begins after birth and completed by 4 years age.
This type of bone is seen in rapid bone growth (ex: healing fracture), resists forces in all directions and is always pathologic in adults.
woven bone
This type of bone has ordered collagen deposition and is stronger than other types.
lamellar bone
After the ossification of the cartilage template is complete ,all increase in length takes place at the _____ _____
epiphyseal plate
When is the epiphyseal plate sealed and no further increase in length occurs
puberty
Reduced osteoclast activity results in too much bone
osteopetrosis
Too much degradation of bone and not enough deposition causes weakness
osteoporosis
Immediate response to a bone fracture
blood clot
Infiltration of which cells (2) from the periosteum create a bone callus after the blood clots
fibroblasts and osteoprogenitor cells
In bone repair, what do progenitor cells far and near blood vessels differentiate into, respectively.
Far: differentiate into chondroblasts and form cartilage scaffold
Near: osteoblasts and convert cartilage to woven bone. The woven bone later becomes lamellar bone
