Bone biology Flashcards
How many bones in the human body?
206
Types of bones in the body 5
Long Short Irregular Flat Sesamoid
Describe long bones
Shaft with two enlarged ends to form joints
Describe flat bones
Two flat surfaces and trabecular bone in middle
Examples of long bones(2)
Femur
Humerus
Example of flat bones(2)
Clavicle
Sternum
Describe short bones
Three equal dimensions
Example of short bones(2)
Bones in wrist
Bones in the ankle
Describe irregular bones
Highly irregular in shape.
Example of irregualr bones
Vertebrae
Describe sesamoid bones
Very small like a sesame seed
Where do you find sesamoid bones
In places where there is tension and friction
Examples of sesamoid bones
Patella in the kneecap
What is the bone matrix made up of? What are they made up of?
Balance of inorganic and organic bone
Organic- collagen and proteoglycans and osteocalcin, growth factors, cytokines, sialoprotein
Inorganic- mineral made up of hydroxyapatite and calcium phosphate
What does collagen do to bone
The more collagen the more flexible
What does mineral do to bone
The more mineral the more brittle compressive
What disease affects bone and how? 4
Rickets in children- lack of minerals makes them unable to support load properly
Osteomalacia -too much organic matrix
Osteogenesis imperfecta, commonly known as brittle bone disease- not sufficient amount of organic matrix and not enough collagen
Marble disease- lack of reabdorption of bone
What are the classification of bone cells 5
Osteochondral Progenitor Cells Osteoblasts Osteocytes Osteoclasts Bone-Lining Cells
What are Osteochondral Progenitor Cells
They are undifferentiated stem cells which can differentiate into any of the other cell types
What are Osteoblasts
They are the main bone forming cells that lay down osteoids that are mineralised in the bone
What are Osteocytes? Function?
mature osteoblast bone cells in lacunae. They maintain the bone in a healthy condition by releasing enzymes. They also regulate chemicals such as calcium
What are Osteoclasts
Main bone resorbing (remove) cells
What is the function of Bone-Lining Cells
regulate movement of Ca2+ and PO4- ions
What happens to osteoblasts after they have done their role?
They either die or become osteocytes or bone lining cells
Types of bone
Cortical/Compact
Cancellous/ Trabeular
How is cortical bone formed?
Haversian systems- osteon
How is cancellous bone formed?
Trabeculae connect together to form trabecular with cavities
What do Haversian system contain?
- https://training.seer.cancer.gov/images/anatomy/skeletal/bone_tissue.jpg
Haversian system:
Haversian canal- central canal
Concentric Lamellae- Concentric layer of bone matrix
Interstitial lamellae-bone matrix between osteons
Circumferential lamellae- bone matrix round the surface
Volkmanns channel- This is where blood vessels travel across to other osteons
-Periosteum- Periosto (highly vascularised- these blood vessels connect with volkmans canal)membrane surrounding bone
-Osteocytes that sit in a space of fine bone matrix
-Canniculi- passage through hard bone so osteocyte recieve nutrition
What is the cancellous bone made of?
Plates/ bars form the cavities which are filled with red bone marrow
On the surface Osteoblasts, osteoclasts(look bigger because of the multuple nuclei) osteocytes in the middle of lamellae
Canniculus- Passage through lamellae (bone matrix) to cavities where there is red bone marrow to recieve nutrients.
What is also known as bone development?
Ossification
What is ossification?
bone development
What are the two types of ossification
Intramembranous
Endochondral
What is osteogenesis?
Bone development
Process of intramembranous ossification ?
Bone condenses to form a connective tissue membrane. The cells in here then transform into osteoblasts which lay down bone. From a cartilage template which forms a shape of what the bone will make. Cartildage plate is ossified slowly into bone
What bones are made by intramembranous ossification
Flat bones in the body: skull bone, sternum, clavicle
When does endochondral ossification take place?
Teens to early 20s
What bone is made by endochondral ossification
All bones other than flat bones
Why type of growth makes bone grow wider
Appositional growth
Why type of growth makes bone grow longer
Endochondral growth
What type of growth can bone not do?
Interstitial growth
What two ways do bone grow?
Endochondral
Appositional
Describe the appositional growth
Osteoblasts in periosteum secrete matrix become trapped as osteocytes
Osteoclasts increase diameter of medullary cavity
Increases diameter of bones until skeletal maturity
Describe the Endochondral growth
Requires interstitial growth from cartilage first
Occurs at epiphysial growth plates- this is where the cartiladge plate would be
Stops when growth plates ossify
What is woven bone?
Newly laid down bone
What is refered to as newly laid down bone?
Woven bone
What is the collagen like in woven bone?
Randomly placed
What is bone remodelling?
This is where osteoblasts lay down bone and osteoclasts resorb (remove) bone and in its place is lamellar(ordered) bone
What is lamellar bone
Ordered bone
What happens to bone over time?
Bone shape changes in response to changing responses
Factors influencing bone growth and remodelling 6
Mechanical Factors Genes Hormones Aging Diseases Diet (not to the same extent)
What does Wolfs law state?
Bone can adapt to peak strain to normalise deformation
How does stress affect osteoblast activity?
More stress increases osteoblast activity which increases bone whereas less stress decreases osteoblast activity which means less bone
What happens to bone for people who excersie regularly?
They have helathy bones, as more stress increase bone density making their bones strong
What happens to bone for people who
don’t excersie regularly?
Dont put enough stress on skeloton so leads to mchanically poor bone
What happens to people who cant walk for a long time?
They will lose bone density
Bones will be extremly weak/ flexible so unable to support weight. Treatment and physical therapy restore bone density until they have a higher bone strength/density
How do genes affect bone?
They determine the size and shape of bone.
Not one gene determines it, height and bone mass is multifactoral
Influence growth hormone release
Influence hormone receptors on bone cells
Ability to absorb nutrients (calcium) from gut
Genetic disorders influence bone growth e.g dwarfism this is the gene growth factor receptor 3 is defective, it’s needed for providing transformation of the chondroblast in the growth plate, with this defect they don’t proliferate properly and they end up with abnormally normally short limbs
How does hormones affect bone growth?
Growth, sex and thyroid hormones influence cell differentiation and metabolism
Overactivity of pituitary gland which causes excess growth hormone making them extremely tall but can lead to organ failure
How does ageing affect bones?
- Osteoblast matrix production slows in comparison to osteoclast matrix resorption.
- Decreased collagen deposition results in more brittle bone (less flexible strength)
- bone mass peaks at 25-30 yrs then falls
What risk factors that cause osteoporosis?
- bone mass is reduced particularly in women
after menopause ( less oestrogen production)
Other factors affecting oestrogen levels
What factors reduce osetrogen levels? 4
removal of ovaries
extreme exercise
anorexia nervosa
smoking
What is mostly affected by oesteoporosis?
-cancellous bone is most affected as it is severely weakened if as connections between trabecullae are lost
What are types of cartiladge?
Fibrocartiladge
Elastic
Hyaline
What two ways do cartiladge grow?
Interstitial
Appositional
What is the outer area of hyaline cartiladge called? What kind of layer is it? What are they made of?
Perichondrium- Double layer
Outer layer- denser irregular connective tissue woth fibroblasts
Innerlayer- Fewer fibres wth chondroblasts
Where do you find chondroblasts?
In the inner layer of Perichondrium
What is Interstitial growth in cartildge?
Where chondrocytes cells divide by mitosis and cartilage matrix from inside
What is appositional growth in cartildge and where?
Cells in the innerlay divide and produce cartiladge-
Chrondroblasts divide and make the tissue
What is articular cartiladge
Type of hyaline cartiladge
Where do you find articular cartiladge
On articular surfaces of bones
What makes articular cartiladge different from hyaline
Nor perichondrium
How do articular cartiladge grow
Similiar to groeth plate
Column of cells form from mitosis, these gradually calcify and become bone.
Type 2 Collagen fibrils anchor proteoglycan to bone
Growth stopos at similiar time but never ossifies like growth plate
What is the structure and for that its Function of Articular Cartilage 4
Smooth- reduces friction so reduces heat so less protrein damage
Low wear surface
Deformable and elastic, Distributes load evenly-Increases surface area, reduces force (peak contact stress)
Creep also increase surface area during sustained loading
Has high stiffness to compression & resilience
How do you describe adult articulate cartiladge
Hypocellular
Aneural
Avascular
Cartiladge metabolism and how it is maintained?
Balance between Matrix synthesis and matrix degredation
Maintained by group of cytokines and growth factors
Factors influencing cartilage metabolism
Mechanical factors
Injury
Aging
Diseases
How do mechanical factors affect cartilage metabolism? 3
What is this called?
High strain -> matrix deposition -> increases matrix stiffness
Low strain -> Matrix resorption -> Reduced matrix stiffness
Anabolic & catabolic processes adjusted to adapt matrix to mechanical demands
Adaptive remodeling
How is the adaptive remodeling adapted in terms of load?
Load below 1 MPa may be catabolic while load above 1 MPa may be a anabolic stimulus Mega pascals (MPa)
What is best at adapting to environment, bone or cartilage or muscle?
Muscle
How is cartiladge affected by injury?
Because articular cartiladge is avascular injury means it cannot repair
Cumalitive injuries lead to musculoskeltal conditions
What does avascular mean
Lack of blood vessels
How does ageing and diseases affect cartilage
With age, decresae in PG & collagen turnover- collagen disriupted- Loss of proteoglycan (PG)- Water lost on compression which leads to tissue damage
Increased non-enzymatic glycation (NEG)
Ageing leads to impaired joint lubrication.Without lubrication increased heat/ friction -> cracks in cartilage-> osteoarthritis
