Lecture 6 Flashcards
Why is bone a living tissue (what type) and what functions can it perform as a result?
Bone tissue is a living connective tissue because it contains cells embedded within a large amount of extacellular matrix. As a result of being a living tissue it is able to grow, remodel itself and repair itself.
What extracellular components does bone primarily consist of? What are the relative amounts?
Organic, which makes up 33% of the matrix contains collagen (a protein), ground substance (proteoglycans).
Inorganic, which makes up 67% of the matrix contains hydroxyapatite (mineral salts which contain lots of calcium).
What functions to the extracellular components of bone do? What happens if they are removed?
Organic functions to resist tension, if removed the bone becomes brittle and easy to break.
Inorganic functions to resist compression and without it the bone becomes very bendy.
What cells are found in bone tissue and what do they do?
Osteoblast: Secrete the extracellular matrix.
Osteocytes: mature osteoblasts which have surrounded themselves in extracellular matrix.
Osteoclasts: break down ECM.
What is the gross structure and microscopic structure of compact bone?
At the gross level the compact bone looks impenetrable, but actually contains small holes (foramina) which allow nutrients and blood to enter or leave the bone.
At a microscopic level the compact bone consists of many osteons (a longitudinal cylinder within the compact bone), these osteons are formed from lamellae (lamella) which are tubes of ECM, these lamellae form a series of cylinders with each layer winding in a the opposite direction to the previous one to increase strength. In the centre of this osteon is a central canal which contains blood vessels and nerves. Osteocytes live in small lake like structures within the lamellae known as lacunae and from these come channels which lead into the central canal which allow for cytoplasmic extensions of the osteocytes to recieve nutrients.
What is the periosteum and subperiosteal surface?
The periosteum is a dense layer of connective tissue which coats the bone, the subperiosteal surface is the internal surfact of the periosteum.
What is the structure of cancellous bone?
A primarily empty space bone type which is joined together by trabecullae (struts of lamella bone). In the empty space (cavities) is bone marrow and osteocytes are found in lacuna on the surfaces of the trabeculae. The trabeculae are organised in such a way as to resist the mechanical stresses typically applied to them.
