Lecture 4: Bone tissue and microscopic structure Flashcards
How many extracellular compartments does bone have?
Two. Organic and Inorganic
What percentages of the ECM are organic and inorganic
33% Organic
67% Inorganic
What is Organic ECM made of
Collagen (protein)
Ground substance (proteoglycans)
What is the function of organic ECM in the bone
It resists tension
What happens when collagen is removed from the bone?
It becomes brittle and breaks easily
What makes up the inorganic ECM in the bone
Hydroxyapalite + other Calcium minerals, mineral salts
What purpose do mineral components serve in the bone. What happens in their absence
THey make the bone hard and resistant to compression. Without them the bone is too flexible and cant hold shape
What are the four types of bone cells
Osteogenic cells
Osteoblasts
Osteocytes
Osteoclasts
Which of the four bone cells are mature boon cells
Osteocytes
What % of bone weight is made up of the cellular component
2%
What is the purpose of the 4 types of bone cells
To maintain homeostasis in the bone and balance the destruction and formation of bone.
What is the function of of the type of bone cells do?
Osteogenic cells - Stem cells that produce osteoblasts
Osteoblasts - make new bone matrix
Osteocytes - Maintainers that recycle protein and minerals from the matrix
Osteoclasts - destroy cell matrix
What bone structure makes up compact bones?
Osteon structure
What bone structure makes up cancellous bones?
Trabecular structure
What is an osteon?
circular units that make up compact bone structure (osteon structure)
What is the function of osteons
They provide a pathway for nutrients to get to cells in the ECM
What part of the Osteon is the central canal? What does it do?
The large hole in the middle that contains blood vessels and nerves
What are lamellae? What do they do?
a series of cylinders
formed of ECM around the central
canal. They form the shape of the osteon
What is within lamellae made of and what function does this serve?
They are made of collagen fibers that serve the purpose of resisting forces.
What are Lacunae?
Lakes for osteocytes
What are canaliculi
channels for nutrients
to travel to osteocytes through the
ECM
What are Trabeculae
Struts of lamella bone
What fills the cavities between trabeculae
Bone marrow
Why does the Trabeculae bone structure not have a central canal?
Because it is thin and nutrient rich marrow is superficial to the ECM so it the bone can directly diffuse nutrients.
What does trabecular bone do?
Spreads force distally. Trabeculae channel weight into the compact bone
What is appositional growth?
Appositional growth is the process by which bones increase in diameter. It occurs when bone tissue is added to the surface of bones.
What facilitates appositional growth?
Osteoblasts and Osteoclasts by destroying and forming bone
What is the process of bone formation called and what does it help with?
Remodelling. THis allows the body to mobilise calcium, phosphate and other minerals from the bone matrix.
Also allows bone to respond plastically and change shape to resist strain and adapt.
What condition will a person have when there is a failure to maintain bone homeostasis?
Osteopenia
What does osteopenia lead to?
Loss of cortical bone
Compression fractures
Trabeculae become thinner
Compact bone is composed of units called _____
Osteons
What is the extracellular component
of bone made of?
Hydroxyapatite (mineral) and collagen
(organic)
How do bones grow wider
(appositionally)?
Osteoclasts hollow out bone from the
medullary cavity.
Osteoblasts add bone to the outer
surface
