Cellular structure of bone Flashcards
(36 cards)
What are the functions of bone?
- Support and movement:attachment site for muscles
- Protection for internal organs
- Provides home for bone marrow
- Act as a mineral reservoir
- Endocrine function as it is a source of some non-classical hormones
What is the composition of bone?
- Protein:organic osteoid matrix(25%)
- Minerals(75%)
- Cells
What type of collagen does the organic protein matrix have and what does that give?
Mainly type 1 collagen
-Gives both flexibility and tensile strength
What is bone mineral mainly made up of?
Mainly hydroxyapatite
What is bone minerals composed of?
Composed of both calcium and phosphate
What qualities does bone mineral have and what does this give?
Its rigid and brittle:
-Gives high compressive strength
What cells are present in the bone?
- Osteoblasts
- Osteoclasts
- Osteocytes
What cells are present in the bone marrow?
- Mesenchymal stem cells
- Haematopoietic cells
What are osteoblasts ?
They are bone forming cells
What are osteoblasts derived from?
Derived from mesenchymal stem cells
What do osteoblasts secrete?
Secrete osteoid collagen matrix of bone
What do osteoblasts promote?
Promote mineralization of osteoid
What are osteoclasts?
They are bone reabsorbing cells
What are osteoclasts derived from?
Derived from haematopoietic stem cells
Structure of osteoclasts?
Large and multinucleate
What do osteoclasts secrete?
Secrete acid to dissolve bone mineral enzymes to digest organic matrix
What is the life cycle of the osteoclasts controlled by?
Controlled by apoptosis
Where do osteocytes come from?
Come from terminally differentiated osteoblasts
What are osteocytes encased in?
Encased in bone mineral matrix
What do osteocytes extend?
Extend multiple dendrites via minute canals in bone matrix
What does the lacuno canalicular system maintain?
Maintains communication with bone surface and blood vessels
How does bone remodelling occur in cortical bone?
- There is a longitudinal system of canals and spaces
- There will be a leading edge, where cells differentiate into osteoclasts and start to digest the bone
- Osteoblasts differentiate and lay down new bone here
How does bone remodeling occur in trabecular bone?
- Osteoclasts will eat away at the bone and osteoblasts will form new bone
- The lining cells on the surface of the bone detach underneath it and form a basic multicellular unit
What are the stages in bone remodelling?
- Activation
- Promotion of the differentiation of new osteoclasts - Resorption
- Duration of the osteoclast activity
- Removing old bone and creating the pits - Reversal
- Osteoclast apoptosis, terminating osteoclast activity and overlapping with osteoblast differentiation - Formation
- Osteoblasts line the surface, leading to . the formation of osteoid which eventually become mineralised
