201 L7 Flashcards
Tissues under load
Name the types of bone cells.
Osteoprogenitor cells
Osteoblasts
Osteocytes
Osteoclasts
What is the bone ECM mainly composed of?
Type 1 collagen fibres
Hydroxyapatite
low levels of proteoglycans
What are the types of adult bone?
Compact bone
Trabecular bone
——— bone is organsied in ——— lamellae around ——- — forming ———-.
——– fibres are arranged in a —- —- fashion in each —– providing strength and —– to ———–.
Compact bone is organsied in concentric lamellae around blood vessels forming osteons.
collagen fibres are arranged in a criss cross fashion in each osteon providing strength and resistance to tension.
——— bone have ——- lamellae that align in a particular way according to ———- that are put on it.
The bone remodels over time.
Trabecular bone have parallel lamellae that align in a particular way according to stresses that are put on it.
The bone remodels over time.
Compact and trabecular bone have the same ————- organisation but different ———— organisation
Compact and trabecular bone have the same microscopical organisation but different macroscopical organisation
In compact bone the ——- of each osteon within bone are —— and aligned ——– to the long axis of bone.
In compact bone the lamellae of each osteon within bone are cylindrical and aligned -parallel to the long axis of bone.
What force do collagen fibres and the calcified ECM withstand?
Collagen = tension ECM = compression
Compact bone is found in regions of —- loads.
Spongy bone is found in regions of —– loads
Compact bone is found in regions of high loads.
Spongy bone is found in regions of low loads
What forces does compact bone withstand?
Compression
Tension
What forces does trabecular bone withstand?
Tension
Compression
In equal amounts
What bone type provides the biggest strength?
Compact bone
What is the composition of humans bone?
Water 25-30%
Mineral 60-70% - compression
Protein (collagen) 5%-15% - tension
Describe Wolff’s law
Bone adapts to the loads under which it is placed.
The more you load the bone the stronger it gets (vice versa)
Bone is highly adaptive
Bone is anisotropic: the ———– properties of bone are different when —— is applied in different ———–.
e.g The ——– strength of the bone is greater if loaded in the longitudinal axis than perpendicular to the longitudinal axis. Therefore cortical bone is —— in tension and ——- in compression.
Bone is viscoelastic: the ————- properties are different when ——— are applied at different ——–. More energy can be absorbed by bone at ——- loading rates. Therefore, the more strenuous the activity, the ——— the bone.
Bone is anisotropic (it’s not a homogenous equal loading): the mechanical properties of bone are different when load is applied in different directions. e.g the tensile strength of the bone is greater if loaded in the longitudinal axis than perpendicular to the longitudinal axis. Therefore cortical bone is weak in tension and tough in compression.
Bone is viscoelastic (an element of elasticity): the mechanical properties are different when loads are applied at different rates. More energy can be absorbed by bone at higher loading rates. Therefore, the more strenuous the activity, the stronger the bone.
What is osteoporosis?
Bone resorption, osteoclast activity, is greater than bone formation, osteoblast activity, resulting in decreased bone mass.
What are the effects of osteoporosis?
The density and quality of bone are reduced leading to weakness of the skeleton and increased risk of fracture.
Loss of mineral content
Why are post-menopausal women at risk of developing osteoporosis?
Estrogen has a positive metabolic effect on bone so when this decreases there is an imbalance in osteoclast and osteoblast activity
What are some risk factors of osteoporosis?
Aging Sedentary lifestyle Post-menopausal women Smoking Oral contraceptive Low calcium diet Thin build Excessive alcohol and caffeine
What are some treatments for osteoporosis?
High calcium diets
Bisphosphonates - anti-resorptive (slows down the osteoclast activity)
Exercise - loading the bones is good to stimulate the osteoblasts
Hormone replacement therapy - progesterone or estrogen
What attaches muscle to bone?
Tendon
Structure of ligaments and tendons:
Closely packed parallel bundles of ——– fibres,
Rows of ————,
——– network.
Some ——– fibres, more prominent in ————.
In some ligaments (e.g. ligamentum flava) —– fibres predominate.
Gliding and sliding of tendons is facilitated by tendon sheaths, an inner epitendineum
attached to the surface of the ———- and an outer parietal layer attached to surrounding
——–.
The intervening space is filled with synovial fluid rich in ——— ———.
Closely packed parallel bundles of collagen fibres,
Rows of fibroblasts,
Capillary network.
Some elastic fibres, more prominent in ligaments.
In some ligaments (e.g. ligamentum flava) elastic fibres predominate.
Gliding and sliding of tendons is facilitated by tendon sheaths, an inner epitendineum
attached to the surface of the tendon and an outer parietal layer attached to surrounding
tissue.
The intervening space is filled with synovial fluid rich in hyaluronic acid.
If there is loss of —— in tendons and ligaments it leads to rapid ———–.
If there is loss of tension in tendons and ligaments it leads to rapid remodelling.
What causes muscle wastage, bone thinning and loss of cartilage matrix?
Cause - Lack of loading stimuli
under use or immobilisation
Long distance running causes site-specific reduction in ———— content in ——– cartilage which can lead to early onset of ———-.
long distance running causes site-specific reduction in proteoglycan content in articular cartilage which can lead to early onset of osteoarthritis
Excessive use
Why do we need tissue engineering?
Articular cartilage doesn’t repair well.
Avascular
Aneural
No lymphatics
Tissue engineering is for —— replacement.
Cell replacement is for —— replacement.
Tissue engineering is for mechanical replacement.
Cell replacement is for biochemical replacement.
Tissue engineering technique = ——— + ———- + ————
Tissue engineering technique = cells + biocompatible scaffold + mechanical stimuli
Name the sources of cells used for tissue engineering.
Autologous
Allogenic
Xenogenic
Name source of cell used for tissue engineering described below:
From the person who is having the replacement
No rejection issues but sometimes a slow growth process
Autologous
Name source of cell used for tissue engineering described below:
Donor from the same species
Allogenic
Name source of cell used for tissue engineering described below:
Donor from a different species
Xenogenic
Scaffold for tissue engineering;
Allows cells to ——-
Allows ——–/—— delivery
Can apply ——— loads
Allows cells to attach
Allows nutrient/waste delivery
Can apply mechanical loads
What are the types of scaffold for tissue engineering?
Collagens
Alginate (gels)
Hydropolymer
