lecture 15 - bone histology Flashcards
What is a lacuna?
A space containing a cell
What is the outer layer of a bone called?
The periosteum
What parts of a bone is absent of periosteum?
Articular surface, points of insertion of tendons/ligaments
What is the periosteum made up of?
Condensed collagen
What layer lines the inner surface of the bony wall?
Endosteum
What is the endosteum?
The layer lining the inside of bones, containing bone cells
What types of cells does the endosteum contain?
Osteoprogenitor cells, osteoblasts, osteoclasts
What is stored in the medullary cavity?
Hemopoietic tissue (marrow), fat
What is the long shaft of a long bone called?
Diaphysis
What are the ends of a long bone called?
Epiphysis
What separates the epihysis and diaphysis of a long bone?
Metaphysis
What are the 2 types of bone?
Compact, trabecular/cancellous
What is the function of compact bone?
Strength/rigidity, resist tensile forces
What is the function of cancellous bone?
Minimising bone weight while resisting compressive forces
What is the alternative name for osteons?
Haversian systems
What are osteons?
Bony tubes that lie parallel to each other along the long axis in compact bone
What are the layers of an osteon called?
Lamellae
What are lamellae made up of?
layers of ossified extracellular matrix
What are the 3 types of lamellae in bone?
Concentric, Interstitial, circumferential
Where are concentric lamellae found?
In layers around the osteons
Where are circumferential lamellae found?
The periphery of bone
Where are interstitial lamellae found?
Between haversian systems/osteons
What are Haversian canals?
Canals that are parallel with the length of an osteon that carry blodo vessels and nerve axons.
What is the contents of a Haversian Canal?
1 or 2 capillaries lined by fenestrated epithelium, and a few unmyelinated axons
What is the nature of capillaries within Haversian canals?
Fenestrated
What canals connect Haversian canals with each other?
Volkmann’s canals
What is contained within each lacunae in an osteon?
An osteocyte
What connects lacunae in an osteon?
Canaliculi
How are nutrients brought to trabecular bone without blood vessels>?
Via canalicular diffusion from marrow vessels
What connects the periosteum to the underlying cortical bone?
Sharpey’s fibres
What are Sharpey’s fibres?
Fibres that connect underlying cortical bone to the periosteum
Why is the periosteum important in fracture healing?
Contains osteoblasts and osteoprogenitor cells that are new-bone forming for remodelling/repair
What does the endosteum line?
Medullary cavity, haversian canals, trabecular bone
What cell types are found in the endosteum?
osteoblasts, osteoclasts, osteocytes
What are the 2 key components of bone extracellular matrix?
collagen, hydroxyapatite microcrystals
What are the biggest type of bone cell viewed histologically?
Osteoclasts
What are the histological features of an osteoclast?
Large, lots of nuclei, folded plasma membrane
What is the function of osteoclasts?
Break down bone matrix
Where in bone are osteoclasts and osteoblasts found?
Lining the endosteum
How can osteoblasts be identified histologically?
The line the endosteum
What is the conditon caused by low osteoclast activity?
Osteopetrosis/marble bone disease
What is the function of osteoblasts?
Synthesis, deposition and mineralisation of bone matrix
What is the shape of osteoblasts?
Cuboidal
How do osteoblasts connect with neighbouring osteoblasts?
Via plasma membrane extensions
What is the shape of osteocytes?
Ellipsoid
What feature of osteocytes help them form gap junctions with neighbouring cells via canaliculi?
Branching processes
Where do osteoclasts sit?
In resoprtion bays - Howship’s lacunae
What is intramembranous bone ossification?
Direct formation of bones from mesenchymal stem cells that develop into osteoprogenitor cells
What is endochondral ossification?
The conversion of a hyaline cartilage model into bone
What are the 2 types of bone formation/ossification?
Intramembranous ossification, endochondral ossification
Where in a hyaline model does endochondral ossification begin?
A primary ossification centre
Where is the primary ossification centre in a developing bone?
The middle - diaphysis
Where are the secondary ossification centres in developing bone?
The ends / epiphyses
What vessel supplies the periosteum?
Periosteal artery
What vessel supplies the diaphysis of a long bone?
A diaphysial artery
What vessel supplies the epiphysis of a long bone?
Epiphyseal artery
What are the histological features of the synovial membrane?
surface with folds/villi, double layered
What are the 2 layers of the synovial membrane?
Intimal layer, sub-intimal layer
What makes up the intimal layer of the synovial membrane?
A discontinuous layer of synovial cells
What makes up the subintimal layer of the synovial membrane?
Connective tissue with collage/elastin fibres, fibroblasts, macrophages
