lecture 4 - bone tissue Flashcards
What are the percentages of organic and inorganic components of the extracellular matrix of bone?
33% organic, 67% inorganic
What is the main organic component of bone tissue?
Collagen
What is the purpose of collagen in bone tissue?
To make it slightly flexible, preventing shattering of the bone
How is collagen structured in bone tissue?
Long fibres of collagen sit in a ground substance called proteoglycans
What is the ground substances that collagen sits in?
Proteoglycans
What are the inorganic components of bones?
Mineral salts
What is the main mineral salt in bone?
Hydroxyapatite
What type of substance is hydroxyapatite?
A calcium phosphate mineral
What is the function of the inorganic component of bone tissue?
Makes the bone hard and resistant to compression
What percentage of bone mass is given by cells?
2%
What are the types of bone cells? (4)
Osteogenic cells, Osteoblasts, Osteoclasts, Osteocytes
What is the role of osteogenic cells?
They are stem cells that produce osteoblasts
What is the function of osteoblasts?
They produce/build new bone matrix in a process called ossification.
Process of bone growth?
Ossification
What is the function of osteocytes?
They maintain the bone matrix by recycling proteins and minerals and controlling the production/destruction of bone by directing the osteoblasts and osteoclasts.
What is the function of Osteoclasts?
They remove bone matrix in a process called osteolysis.
Process of bone destruction?
Osteolysis
What are the macroscopic features of compact bone?
Dense and inpenetrable outer surface (periosteum) with small holes/foramina for the blood supply.
What is the outer surface of bone called?
Periosteum
What is the outermost layer of compact bone tissue called?
Cirfumferential lamellae
What fills the gap between osteons in the compact bone matrix?
Interstitial lamellae
What is the main unit/component of compact bone?
Osteon
What are the components of an osteon? (4)
Central canal, lamellae, lacunae, canaliculi
What is the function of the central canal of an osteon?
It is a tube that contains nerves and blood vessels which carry nutrients to cells within the matrix.
What is the structure and function of the lamellae in compact bone?
The lamellae form rigid rings around the central canal, and contain collagen to resist forces.
What is the structure and function of lacunae in bone tissue?
They are ‘lakes’ that hold the osteocytes which maintain the bone and control its growth.
What is the structure and function of canaliculi?
They are the channels that lead from the central canal, through the extracellular matrix, to the lacunae to provide the osteocytes with nutrients.
What are the struts found in cancellous bone?
Trabeculae
What is the structure of trabeculae?
Multidirectional struts of lamella bone.
How does cancellous bone resist force?
The multidirectional trabeculae struts resist forces around a joint from several directions, before channeling down the diaphysis of a long bone or outwards through a short bone.
What is the structure of trabeculae?
Made up of lamellae with Lacuna filled osteocytes. The canaculi flow straight to the trabeculae surface, without the need for a central canal as nutrients can be absorbed from within the lattice.
How is weight force channeled in the cancellous bone of the pelvis?
Weight is channelled around the ilia into the femur.
What is the term for an increase in bone diameter?
Appositional growth
What is the process of appositional growth?
Osteoblasts add layers of circumferential lamellae to the outer layer of the bone, while osteoclasts remove bone from the medullary cavity.
What is bone homeostasis?
The balance of osteoclast and osteoblast activity, so that bone mass remains constant.
Why might the body break down bone?
To mobilise minerals such as calcium and phosphate
How is bone structure ‘plastic’?
Remodelling allows bones to change shape to withstand repeated stress.
What is osteopenia?
When bone mass decreases as Osteoclast activity exceeds osteoblast activity
What is the diagnosis of clinically significant osteopenia?
Osteoporosis
What are the symptoms of osteoporosis?
Compression fractures (e.g. of the vertebrae) or breaks due to the weakening of bones caused by the thinning of trabeculae in cancellous bone.
At what age does bone mass peak?
25-30
Why are women more prone to osteoporosis?
They lose oestrogen after menopause.
How does excercise prevent osteoporosis?
it stimulates osteoblastic activity
Where are osteogenic cells found in the bone?
In the inner layer of the periosteum and in the endosteum
What is the name of the cellular layer that lines medullary cavities and blood vessel passage ways in bone?
Endosteum
