Bone Development and Ossification Flashcards
What are the 3 types of lamellae in bone and where are they situated?
Intersistual lamellae on the inside, concentric in the middle and circumferential on the outside.
2 types of bone
Where do you find osteons?
Where do you fine lamellae?
Where do you find hyaline cartilage?
osteons = cortical bone
lamellae = cortical and trabecular
hyaline cartilage = joint/articular, on the epiphyseal growth plate
What immune system cells are found in trabecular bone?
Megakaryocytes
How do bone cells change with age? Where does this fill?
Cells change to make less bone and more fat, lipids fill the bone marrow.
What two things can osteoprogenitor cells make?
Bone and cartilage
What bone cells come from mesenchymal stem cells?
Heamatopoietic stem cells?
M - chondroprogenitor cell, chondrocytes, osteoprogenitor, osteoblasts, osteocytes, lining cells
H - macrophage, osteoclasts
Give some details on osteoclasts?
- only cells to be able to resorb bone
- mulitnucleated
- ruffled border (increase surface area for osteoclasts to function)
How do osteoclasts destroy bone?
Osteoclasts sit in the Howship’s lacuna.
Osteoclasts bind to the bone matrix via integrins on its surface. This close attachments creates a seal to form an environment to resorb bone. The area next to the bone forms the ruffles membrane. The osteoclast then secretes acid and proteases which dissolve the bone mineral and matrix.
What are the two types of ways that bone forms?
- Intramembranous ossification
- Endochondral ossification
How does intramembranous ossification work?
Bone is formed directly from precursor cells. Bone is formed in the membrane. and forms the periosteum.
Osteoblasts secrete the extracellular matrix and deposit calcium to harden the matrix. Osteoids form around blood vessels and form the spongey bone..
Blood vessels then penetrate the bone.
How does endochondral ossification work?
This bone is formed from cartilage. It begins as cartilage surrounded by perichondrium. The perichondrium then transitions into periosteum.
There is an invasion of blood vessels.
The deposition of matrix causes the death of chondrocytes as nutrients can no longer reach them.
The primary ossification centre is found at the periosteal collar and the secondary one is found in epiphysis region of the bone.
Endochondral Ossification = What are the 4 zones of epiphyseal growth plates?
What is the point of this?
- Resting Zone (where chondrocytes are)
- Proliferation Zone
- Hypertrophic Zone (mature cells
- Calcification Zone/ Ossification Zone/ Primary Spongiosa
The point is to form bone from chondrocytes. The cells at the bottom zones die because they are surrounded by calcified cartilage and have no access to nutrients.
What happens in the priamary spongiosa?
What is the secondary spongiosa?
An area in the metaphysis where cartilage is used as a template and bone then forms on top of this cartilage.
SS has more mature bone cells formed by the remodelling of primary spongiosa to form mature trabecular bone (woven bone - trabecular).
What are the two types of bone growth? Which can bone form from and which can cartilage? Give info on each type
Interstitial Growth = matrix deposition from within a matrix. Bone and cartilage can form this way. Interstitial growth is the lengthening of the bone resulting from the growth of cartilage and its replacement with bone tissue. A person grows taller because of interstitial growth. This growth occurs at the epiphyseal plate.
Appositional Growth = matrix deposition upon pre-existing matrix. Only cartilage can form this way. This causes the thickness of the bone to increase. It happens when osteoblasts deposit new bone metric layer onto already formed layers on the outer bone surface.
