MS System - Bones Flashcards
Describe the functional anatomy of a long bone
Epiphysis - Top/End of the bone - mainly made of trabecular bone
Metaphysis - connects the epiphysis and diaphysis at the neck of the bone, region of growth during
development
Diaphysis - Shaft of the bone, mainly made of cortical bone
Bone marrow is contained in the diaphysis
Periosteum - fibrous connective tissue sheath covering cortical bone
Name some types of long bone
Humerus, Tibia, Femur, Fibula, Ulna, Radius, Metacarpals and Phalanges
What is the structure of cancellous bone ?
Spongy trabecular bone
Give supporting strength to weight bearing ends of bone
The trabeculae are laid down along lines of stress
The gaps in the trabecular bone contain, osteocytes, osteoclasts, osteoblasts, lacuna etc.
What is the structure of compact bone ?
Cortical, strong bone
On the outside of the bone, forms the shaft of long bones
Provides stiffness and strength
Haematopoiesis
Blood cell formation in bone marrow
What is cartilage ?
Strong connective tissue that supports the body and is softer and more flexible than bone (NOT CALCIFIED)
What is bone ?
Flexible cartilage hardened by minerals
What would happen to bones without
- Collagen ?
- Minerals ?
- Shatter
- Become bendy
Epiphysis
Flared end of the long bone
Articular Surface
Covered in hyaline cartilage
Diaphysis
Shaft of the long bone
Hollow cylinder
Contains bone marrow
Porous
Nutrient Foramen
Small opening in the middle of the external surface of the diaphysis, through which an artery enters the bone to provide nourishment (via blood supply)
Periosteum
Fibrous connective tissue sheath, covering external bone surfaces that supplies blood, nerves and cells
What 3 cell types are present in the periosteum ?
- Fibroblasts
- Mesenchymal cells
- Osteoclasts
Fibroblasts
Cells that synthesise collagen
Mesenchymal cells
Able to differentiate into osteoblasts and chondroblasts
Metaphysis
Growth zone between the epiphysis and diaphysis during growth in childhood.
What are the 2 major types of bone ?
- Trabecullar
- Cortical
Are all bone cells in contact with blood vessels ?
No, for example osteocytes
In what formation do cortical bones arrange themselves ?
Concentric circles
Haversian canals
Carry blood vertically
Volkman’s canals
Carry blood perpendicularly through bone.
What is the anatomical unit of cortical bone ?
Osteon
What type of fibres are located inside of cortical bone ?
Collagen
What characteristic do network fibres provide to cortical bone ?
Flexibility and strength
Which compound adds strength and hardens cortical bone ?
Calcium hydroxyapatite
What is the anatomical unit of trabecular bone ?
Trabecula
How is collagen arranged in the bone matrix ?
Highly organised in parallel arrangement.
Vitamin D function
Regulates the amount of calcium and phosphate in the body
Rickets
Vit D deficiency
Vitamin C function
A nutrient the body needs for blood vessels, cartilage, muscle and collagen.
Scurvy
Vit C deficiency
Osteoblasts
Bone forming cells
- Single nucleus
- Covers the surface of the bone
- Forms an osseous matrix and becomes enclosed as an osteocyte
Osteoclasts
Chew bone matrix by demineralisation
- Multinucleated cells derived from haematopoietic cells
- Respond to mechanical stress and physiological demands
Osteocytes
Mature bone cells
- Relatively inactive
- Maintains bone matrix via cell-cell communication
Osteoprogenitor cells
Bone stem cells
Life cycle of osteoblasts
Derived from osteoprogenitor cells
Stimulated to form bone at specific sites
Deposition of organic matrix (collagen) then hydroxyapatite
Eventually become entombed in mineral to form osteocytes
What 2 things regulate osteoclasts ?
Hormones
Osteoblasts
What is the function of osteoclasts releasing H+ and hydrolytic enzymes ?
Dissolve minerals
Liberate calcium
Break down the extracellular matrix
Where are osteocytes found ?
Embedded in the bone matrix (lacunae)
Lacunae
small cavities in the bone that contain osteocytes
How do osteocytes communicate ?
Finger like projections in canaliculi
GAP junctions
How is the equilibrium between osteoblast and osteoclast activity controlled ?
Signalling between different cells in bone
Hormone signalling
Calcitonin
Lowers activity of osteoclasts and blood calcium levels
Parathyroid hormone
Increases activity of osteoclasts and blood calcium levels
4 stages of TRABECULAR bone remodelling
- Quiescence
- Resorption by osteoclasts
(burrowing into bone structure) - Osteoprogenator cells triggered (differentiate into osteoblasts)
- Osteoblasts lay down new bone
3 stages of CORTICAL bone remodelling
- Osteoclasts reabsorb bone
- Osteoblasts lay down a new matrix
- Osteoblasts become embedded and become osteocytes
Wolf’s Law
Bone ADAPTS to the load under which it is placed
“Use it or Lose it”
Causes of bone mass and density increase (1)
Excessive mechanical simulation
Causes of bone mass density decrease (3)
Non weight bearing (Immobilisation)
Sex hormone deficiency (Menopause)
Endocrine and nutritional disorders
Osteoporosis
A pathological condition where chewing outweighs the building
Where does bone growth begin during fetal life ?
Diaphysis
Name the 5 zones in bone lengthening
Resting zone - chondroblasts
Growth zone - mitosis of chondroblasts, forming columns
Hypertrophic zone - chondroblasts become chondrocytes
Calcification zone - chondrocytes deposit minerals between the columns. This destroys the chondrocytes.
Ossification zone - columns break down, osteoblasts lay down new disorganised bone which is eventually remodelled by osteoclasts and blasts.
