Bone Histopathology Flashcards
What do types of connective tissue have in common?
Made of connective cells with ECM in between
Where can we find hyaline cartilage?
ribs, trachea, joints
What type of collagen is found in hyaline cartilage?
type 2 collagen
What is the function of large GAGs in hyaline cartilage?
attract water and give the stiffness
What is the function of chondronectin
provide attachment for chondrocytes, as healthy cartilage require constant maintenance of chondrocytes
What are the characteristics of elastic cartilage?
mixture of hyaline cartilage and elastin
very flexible, maintains shape
Where can we find elastic cartilage?
the ear and tubular canals
What is fibrocartilage made of?
hyaline cartilage and fibrous tissue
Hybrid of connective tissue and isolated islands of chondrocytes
T/F Perichondrium can be found on fibrocartilage
False, it’s only found in hyaline and elastic cartilages
T/F Fibrocartilage has type I collagen
True
T/F Fibrocartilage will replace the collagen type II centre in annulus fibrosis by the age of 20
False, AF is already made of fibrocartilage. The nucleus pulposus collagen type II will be replaced by fibrocartilage by 20
What are the two types of bone structure?
outer compact bone
inner trabecular bone
Where can we find Haversian systems? What are they?
compact bone. They are long columns of bone surrounding a central blood vessel. It lines parallel to lines of stress
How do osteocytes in the trabecular bone get access to nutrients
they extend out processes into the marrow cavity
Where can we find red marrow in an adult?
Flat bones
What are the two layers of connective tissue on the surface of bone? Which cells can be found there?
periosteum and endosteum
osteoprogenitor cells
What are Sharpey’s fibres?
Tendon collagen penetrating bone surface, and type I collagen becomes continuous with bone collagen
Why is hyaline cartilage ideal for joint surface?
the cartilage is smooth and incompressible
Which part of the bone does the nutrient artery supply?
diaphysis
What is perichondrium?
a layer of dense irregular connective tissue that surrounds the cartilage of developing bone
T/F the periosteum covers the articular surface
False, hence there is a lack of blood supply + problem with repair of damage
What is the synovial space?
fluid filled space that has no epithelium, lined by synovial membrane, providing nutrients/lubricants for the joint
What is synovial fluid made of?
ultrafiltrate of blood + proteoglycan
What is the function of osteoprogenitor cell?
they are usually resting, but when active, they can give rise to new osteoblasts to grow and repair bone
What does the osteoblast make?
osteoid, an organic ECM of bone composed of collagen type I and proteins
What is the function of bone matrix protein?
allows the inorganic compounds to adhere on the bone surface
Where can we find osteocytes? What is the function of osteocyte?
deep in the bone, surrounded by bone
they synthesis material to keep bone healthy
T/F Osteocytes play a role in calcium homeostasis
True, they are capable of destroying local bone to free up Ca
How does an osteoclast cause bone resorption
Osteocyte seals itself to bone around the edge and secrete HCL and proteases to dissolve calcium phosphate
How do we measure osteoclast activity
measure tartrate-resistant acid phosphatase
How are osteoclasts derived?
from hemopoietic stem cells, related to macrophages
What are the two ways of developing bone? What are the processes involved?
intermembranous - directly form bone from mesenchyme
endochondral - cartilage model replaced by bone
Describe the process of replacing cartilage with bone
1) starting with a cartilage model, bone collar is deposited on the surface of diaphysis, denying blood supply, and inner cartilage degenerates, forming an inner cavity
2) blood vessels can invade the primary ossification centre
3) secondary centre forms at epiphysis, with separate blood supply
4) bone continues to grow only at the epiphyseal plates
T/F The growth of epiphyseal plate is symmetrical
False, the diaphysis side usually grows faster
What are the layers of growth plate?
distal normal hyaline cartilage
layer of dividing chondrocyte
layer of mature chondrocyte
layer of dying, hypertrophic chondrocyte
layer of degenerated chondrocyte and bone deposition
What is woven bone? How is it different to adult bone?
woven bone = new bone during development or repair. It is more cellular, has more collagen, and lacks Haversian systems
How does remodelling occur?
osteoclasts dig a cavity in response to stress on bone
blood vessels invade
endosteum is laid down, allowing entry of osteoblasts to lay layers of bone with collagen in alternating directions
Only a small space is left at the end for the blood vessel
What’s the Haversian system also known as?
Osteon
How do woven and lamellar bones differ in terms of collagen
woven: collagen is everywhere. Hence it’s made very quickly
lamellar: collagen laid down in the same direction
What is the lacunae and the canaliculae of an osteocyte?
lacunae - spot where the osteocyte is
canaliculae: network for sucking up blood and nutrients
What do osteocytes mainly respond to?
mechanotransduction, so bones can remodel under stress
How do osteoblasts look when they are 1) inactive 2) active
inactive: flat, like osteoprogenitors
active: big and plump, similar to plasma cells but don’t have dotted nuclei
how are osteoclasts stimulated?
Indirectly by RANK-L and M-CSF from osteoblasts
Which molecule blocks the action of RANK ligand on an osteoblast
OPG
Why does osteoid (from osteoblasts) contain cytokines?
cytokines get laid down along with bone matrix, so osteoblasts can be stimulated where bone has been resorbed
What’s the function of the substance inside the secretory vesicle from osteoblasts?
vesicles contain ALP, pyrophosphatase, and are used to increase local concentration of calcium and phosphate for precipitation
When concentration of mineral is high enough, they crystalise
What’s the most common calcium phosphate?
hydroxyapatite
What’s the difference between a greenstick fracture and a torus fracture
greenstick - incomplete fracture only on one side of cortex
torus - ring of cortical fracture, usually due to compression
T/F Oblique fracture heals faster than spiral fractures
False, spiral heals faster because there are numerous edges of bones in contact with each other
What’s a comminuted fracture?
multiple fragments of fracture
What’s a stress fracture caused by?
repeated low force injury to a normal bone
What’s the composition of granulation tissue
fibroblast, collagen, capillaries
What’s involved in the inflammatory phase of bone healing
How long does this phase last?
haematoma formation - fibrin mesh, platelet + leukocyte infiltration, granulation tissue formation
few days
What’s the composition of soft callus in bone healthing
cartilage from condrocyte activation (hold the bone together) + periosteum on the outside
How is soft callus different to hard callus?
osteoid is deposited in hard callus. The ossification forms woven bone, and cartilaginous soft callus is broken down
What are the four phases of bone healing, and how long is each phase?
hematoma- few days
soft callus - days to weeks
hard callus - weeks to months
remodelling - months to years
What is the crucial factor in helping bone healing
stability
T/F Repairing of bone always undergo endochondral ossification
False, the healing method will depend on the amount of movement and pressure placed on the bone
What’s a pseudo-arthrosis?
a non-union healing of fracture, where fibrous tissue is laid down, and the fracture will not heal
What is mal-union?
healing of a bone in an unacceptable position
What are some possible consequences of inappropriate healing of bone?
infection
osteonecrosis
What is osteoporosis?
reduced mass of otherwise normal bone, leading to increased risk of fracture
What is the difference between osteoporosis and osteomalacia
osteoporosis is a reduction in total bone cell count, whereas osteomalacia has demineralisation of bone and no loss of cells
What’s Paget’s disease
large, overactive osteoclasts, leading to overactive osteoblasts
“inappropriate remodelling”
What are some common sites of cancer that can give rise to bony metastasis
breast bronchus thyroid kidney prostate
