3.5 Bone Structure Flashcards
What is the axial skeleton
The bones along the body’s lengthways axis such as the skull, vertebral column and rib cage
What is the appendicular skeleton
The bones attached to the axial skeleton such as limbs and girdles
What are the 5 bone shape classifications
-flat
-long
-short
-irregular
-sesamoid
What are the functions of flat bone
-to protect internal organs
-points of attachment for muscles
What is the structure of flat bone
It is thin and curved. It has a layer of spongey bone lined on either side by layers of compact bone
Give some examples of flat bone
sternum
ribs
cranial bones
What is the function of long bone
To provide leverage
What are the 3 areas of long bone
diaphysis
epiphysis
metaphysis
What is the diaphysis in long bone?
A tubular shaft running between the proximal and distal ends of the bone with a medullary cavity in it containing yellow marrow. The diaphysis wall is made of compact bone
What is the epiphysis in long bone
The wider section at the each end of the bone made of spongy bone.
What is the metaphysis in long bone
Where the diaphysis and epiphysis meet. It has the epiphyseal (growth) plate
What is the endosteum
The membranous lining of the medullar cavity. Its involved in bone growth, repair and remodelling
What is the periosteum
The fibrous membrane covering the outer surface of the bone. It is rich in blood vessels, lymphatic vessels and nerves.
What are long bone fossa
The point of attachment for muscles, ligaments, tendons or joints
Describe how bone is vascularised
Blood enters through the nutrient foramen in the periosteum and nourishes the spongy bone and marrow cavities. The blood then exits through other foramen.
What else follows the same foramen pathway as blood in bone
Nerves
What are the two components of bone matrix and what are their proportions
-35% organic portion (made of collagen fibres and proteoglycans)
-65% inorganic portion (made of calcium and phosphate salts)
What are the functions of the organic and inorganic parts of bone matrix
-inorganic part gives strength
-organic part gives flexibility
What can deficiencies in the organic and inorganic parts of bone matrix give you
inorganic defficiency - rickets
organic deficiency - brittle bones
What are osteogenic cells (aka osteoprogenitors)
The only bone cells that divide. Immature osteogenic cells are found in the periosteum and marrow. Osteogenic cells differentiate into osteoblasts.
What are osteoblasts
The primary bone forming cells, synthesising and secreting the collagen matrix and calcium salts
How are osteocytes formed
As osteoblasts secrete bone matrix, they get trapped in it which changes their structure to osteocytes
What are osteocytes
The primary cell of mature bone. they maintain the mineral concentration of the matrix via secreting enzymes and responding to mechanical strain.
How are osteocytes connected
They are interconnected by long cytoplasmic processes that extend through canaliculi channels to form a network.
What are osteoclasts
Multinucleated phagocytic cells that come from monocytes and macrophages (and their production is regulated by cytokines and sex hormones). They remove bone tissue
Why is the balance of osteoclasts and osteoblasts important
So there can be rapid release and rapid reabsorption of calcium ions
Describe the 2 classifications of bone according to the organisation of the collagen fibres in the matrix
Woven bone:
The collagen fibres are randomly distributed. Is formed for foetal development and for bone fracture repair
Lamellar bone:
Collagen fibres are organised in parallel and perpendicular lamella. Osteocytes are found in the lacuna between the lamella. Mature bone is lamellar.
What are 2 classifications of bone according to the amount of space in the bone matrix
-compact (aka cortical) bone
-spongy (aka cancellous or trabecular) bone
What is compact bone
Dense and vascular, mostly found on outside of the bone. Its basic unit is an osteon. Its defined as 80-90% of the bone volume being mineralised. Most bone in the body is compact
What is spongy bone
It is made of interconnecting trabeculae (groups of lamallae) which provide strength despite its light weight. In between the trabeculae are spaces with bone marrow, osteocytes and blood vessels. The trabecular surface is covered with a single layer of cells.
