MidTerms 1 Flashcards
When does the cartilaginous model begin ossifying
8 weeks
How come bone can repair itself
Due to high vascularisation
Is bone made of mostly ECM or mostly cells
ECM
What are the 2 types of extracellular components of bone
- organic
- inorganic
How much of ECM is organic?
⅓
How much of ECM is inorganic?
2/3
What is the organic component of ECM made of?
Collagen embedded in ground substance (proteoglycans)
How are the collagen fibres aligned in organic ECM
aligned in certain ways depending where forces coming from and to resist tension
What’s in the ground substance of the organic component?
Proteoglycans
Function of organic component
Resist tension
What happens if organic component is removed?
Brittle/breaks easily
What is the inorganic component of bone made of
hydroxyapatite (mineral salts)
What gives the bone hardness
Hydroxyapatite
Function of inorganic component of bone
Resist compression
What happens if inorganic component removed
Too flexible = not good for support and movement
Role of OB
Build ECM
Role of OCytes
OB get trapped in ECM and mature into Octets
- mature bone cells
- important for COMMUNICATION in the remodelling process
Role of OC
break down ECM
Characteristics of OC
- multinucleated
- giant
What does compact bone look like at gross level
- outer surfaces seem impenetrable
- foramina/holes: nutrient foramen - provide blood (nutrients) to cells trapped in the compact bone at the microscopic level
- thickest in shaft
thin round head
for load bearing
What is compact bone for
Load bearing
Microscopic structure of compact bone
- osteon
- lamellae
- central canal
- lacunae
- canaliculi
- periosteum
- subperiosteal surface of bone
Function of Osteon
maintain Ocytes by providing nutrients
- need to bring blood from outside the bone in the gross level to Ocytes
Structure of osteon
longitudinal cylinder within compact bone
- foramen on outer surface of bone at gross level which gives opening for blood vessels and nerves to get into osteon systems
Function of lamellae
- resist forces
- resist tensile forces
- can resist tensile forces no matter which direction the force is coming from
Structure of lamellae
Tubes of ECM with collagen fibres aligned to resist forces
- form a series of cylinders running longitudinally down shaft = osteon
- sheaths of lamella = tubes of ECM
⅓ is collagen
- collagen fibres aligned different ways in each concentric tube to resist tensile forces
Central canal
Blood vessel and nerves
Lacunae
Lakes of OCytes
Function of canaliculi
Channels for Octets through ECM
- nutrient get between lakes
- allow cellular chemical communication between the octets, for the ocytes to communicate to OB and OC that remodelling of that osteon needs to occur
- penetrate lamella
Periosteum
Outer surface of bone
Structure of periosteum
Fibrous connective tissue sheath go around all surfaces of bone
- does not cover the ends where bones end to form a joint
- inserted into bone with fibres
- blood vessel goes through periosteum before it goes through the bone and into the osteon system
How is periosteum inserted into bone
with fibres
Subperiosteal surface of bone
where blood vessel penetrates
General overview of remodelling of compact bone (maintenance of normal, mature compact bone)
- osteoclastic front (multinucleate)
- break down ECM
- come through by blood as OCytes has communicated that remodelling needs to occur so OC come in
- OC destroy ECM
- left with void
- OB come and build ECM
- sheets of lamella formed by OB
- OB gets trapped in ECM and between sheets of lamella
sit within lacuna and aided in maintenance and survival by central canal that brings blood and nutrients diffused between lacuna by canaliculi
Where is cancellous bond found
At bone ends
Describe trabeculae
Struts of lamella bone
- sheets of ECM formed together and form honey comb network of trabecular
What fills the cavities in cancellous bone
Marrow
- red marrow fill gaps and form RBC
How are OCytes fed in trabeculae
Through direct communication with blood
- by blood that is formed and blood vessels penetrating the areas at the ends of the bones
Where are OCytes in spongy bone
Housed in lacuna on surfaces of trabeculae
How are OCytes arranged in spongy bone
Not arranged in concentric circles but the lacunae and OCytes are found in a lattice-like network of matrix spikes called trabecular
- each trabecular forms along lines of stress to provide strength to the bone
- the spaces in some spongy bones contain red marrow, protected by the trabecular, where hematopoiesis occurs.
Where are trabeculae found
More shock absorption
How are spongy bone and medullary cavity nourished
Receive nourishment from arteries that pass through the compact bone
- the arteries enter through the nutrient foramen
the OCytes in spongy bone are nourished by blood vessels of the periosteum that penetrate spongy bone and blood that circulates in the marrow cavities.
There are no blood vessels within the matrix of spongy bone, but blood vessels are nearby in the marrow spaces.
- exchange of nutrients, gases etc occurs between the capillaries in the marrow and the interstitial fluid of the marrow.
- the interstitial fluid extends into the canaliculi and thereby supplies the OCytes.
Are there blood vessels within matrix of spongy bone
NO
but blood vessels are nearby in the marrow spaces.
- exchange of nutrients, gases etc occurs between the capillaries in the marrow and the interstitial fluid of the marrow.
- the interstitial fluid extends into the canaliculi and thereby supplies the OCytes.
Organisation of trabeculae
- resist compression nada shock absorption
- trabeculae aligned in certain ways to diffuse those forces.
What is the zone of weakness
On the superior part of neck
- strengthening on inferior of neck to resist forces, but leaves area with less trabeculae
= area where trabecular do not cross at right ankles - less reinforcement by trabeculae = more potential for injury.
Human Tissue Act 2008
- bodies come from bequests, not condemned criminals or unclaimed bodies
- informed consent
- voluntary donation
- deceased person’s wishes can be overridden by objections of surviving spouse or relative
- no referente to how long can keep body parts
- avoid unnecessary mutilation of body
What is the ECM made of
Water
proteins
proteglycans
Do tendons stretch during flexion
no
Does epithelial tissue have lots of or little matrix
Very little
Does connective tissue have lots of or very little matrix
Lots of ECM, containing fibres
- sparse cells
Role of nervous tissue
Conducting and supporting
- communication and coordination between body parts
Why are unicellular organisms limited in the types of environments they can successfully inhabit
Because their immediate surroundings must supply the appropriate nutrients and conditions
Conditions for life (unicellular)
- nutrients
- solute conc
- temperature
- pH
- toxins (including own wastes)
- lack of predators
What is the internal environment
ECF
Difference between ECF and ECM
The ECM comprises a complex system of non-living matter that is important to sustaining the life of the organism.
Extracellular fluid (ECF) bathes cells, and comprises the fluid component of the ECM
What does the external environment provide?
- source of nutrients
- site for waste disposal
- changeable
- pathogens
Proportion of ICF of total body water
2/3
Proportion of ECF of total body water
1/3
How much of ECF is ISF?
4/5
How much of ECF is plasma
1/5
What does ECF supply
Correct temp, pH, route for nutrient delivery and waste disposal etc
What does ECF also contain
Transcellular fluids contained within an epithelial lined spaces
eg synovial fluid in joints, ocular fluid in eye, CSF
Eg of transmembrane fluid
Synovial fluid in joints
Define homeostasis
The maintenance of relatively constant conditions in the internal environment (ECF) in the face of external (or internal) change
4 statements about homeostasis
- In our bodies there are mechanisms that act to maintain constancy
- any tendency toward change automatically meets with factors that resist change
- there are co-operating mechanisms which act simultaneously or successively to maintain homeostasis
- homeostasis does not occur by chance, but is the result of organised self-government
Main extracellular cation
Na+
Main intracellular cation
K+
Function of Na+
- determines ECF vol
- influences BP
- people with high BP shouldn’t eat too much salt as ECM will inc. Part of ECM is plasma.
- important in AP generation in nerve and muscle tissue
- Na+ must come through specific channels
- ECF vol and therefore BP
- AP generation in nerve and muscle tissue
Normal conc of Na+ in ECF
135-145 mmol/L
Function of Ca2+
- impt structural component of bone and teeth
- involved in neurotransmission and muscle contraction
- essential for blood clotting
- regulates enzyme function (Ca2+ as a cofactor)
- muscle contraction
Which ion for AP generation in nerve and muscle tissue
Na+
Which ion for neurotransmission and muscle contraction
Ca2+
Which ion for blood clotting
Ca2+
Which ion as cofactor
Ca2+
Total plasma conc of Ca2+
2.2-2.6mmol/L
Function of glucose
- used by cells (Esp neutrons) to produce ATP. Neurons are particularly affected by low glucose levels
- high blood glucose causes other problems (both acute and chronic)
Fasting glucose conc
3.5-6mmol/L
Non-fasting glucose conc
3.5-8mmol/L
Function of K+
main determinant of RMP
- particularly important in excitable tissue i.e. nerve and muscle
Normal conc in ECF of K+
3.5-5mmol/L
Osmolarity of ECF and ICF
275-300 mosmol/L
normal pH range
7.35-7.45
What pH results in coma
below 6
Acidosis effect
- depresses nervous system
- neuronal function dec
- consciousness dec
Alkalosis effect
- “overexcitability” of nerve and muscle
- pins and needles
- muscle spasms
- convulsions
Core body temp
36 - 37.5°C
What is core body temp
Chest and head
How does oral and axillary temp differ from rectal (core) temp
0.5°C less than rectal
What happens at higher body temps
proteins denature
What happens at lower body temps
Chemical reactions slow down, preventing normal cell function
Body temp vicious cycel
As cells of nervous system become compromised, the ability to thermoregulate is lost -> viscious cycle. Detrimental positive feedback loop
- eg cold = neutrons can’t properly control temp = colder etc
What does diffusion result from
the random movement of individual molecules as a consequence of their thermal energy
Relationship between distance travelled and time for diffusion
Distance travelled is proportional to square root of time
- four times as long to diffuse twice as far
- therefore diffusion is very rapid over short distances within cells and between cells and capillaries
Is diffusion effective within cells
Very rapid over short distances within cells and between cells and capillaries
Substances that can diffuse directly through the lipid bilayer of our cells
O2
CO2
Steroid hormones
Anaesthetic agents
3 types of channels
Leak
Ligand gated
Voltage gated
Example of carrier-mediated passive transport
Glucose entry into cells when insulin present
- glucose too large to get across cell membrane
What type of entry is glucose into cells when insulin is present
Carrier-mediated passive transport
What does the Na+-K+ pump maintain
- ionic gradients
- helps regulate cell volume
Eg of exocytosis
Secretion of insulin by beta cells of pancreas
Eg of endocytosis
Phagocytosis of microbes by neutrophils
When does osmosis stop
when water conc on both sides are equal. No net movement of water
Osmotic pressure
the pressure required to stop osmosis
How does water move in regards to osmotic pressure
Move from low osmotic pressure to a region of high osmotic pressure
What can differences in solute concentration across cell membrane cause
- fluid shifts
- and create pressure that can damage cells
Differences in solute concentrations across cell membranes can cause fluid shifts and create pressure that can damage cells
.
Osmolarity
Measure of the total number of solutes per litre of solution
Units of osmolarity
osmol/L
Osmolarity of ECF and ICF
275-300mosmol/L
Tonicity
the effect that solution has on cell volume
C and C tonicity and osmolarity
Osmolarity is a property of a particular solution (independent of any membrane)
- tonicity is a property of a solution with reference to a specific membrane
Spacial orientation of ICF, ISF and Plasma
ICF
ISF
Plasma
Osmolarity of ICF, ISF and Plasma
275-300mosmol/L
What happens if intravenous = water
Dilute plasma
- set up osmotic grad
- allow water to move into ISF = dilute ISF
- allow water into cells, through aquaporins, until equilibrium reached (osmolarity in all 3 compartments is the same)
Conc of normal saline
0.9%
Assumptions for calculating osmolarity
- NaCl completely dissociates
- particules move in the way we predict
What conc of normal saline is isosmotic and isotonic
0.9%
Is 300mosmol/L urea isosmotic and isotonic
Urea has conc equal to the solute conc inside cell = ISOSMOTIC
- but urea can diffuse across the plasma membrane (via transporters) because there is not much of the substances inside the cell (diffuse down its own conc grad)
- water will follow and enter the cell
- solution = hypotonic because its effect on cells is to cause them to swell
- but ISOTONIC
RMP
- 70mV
- inside of a ell neg charged cf external surface
What does the RMP result from
the sep of a small number of oppositely charged ions across the lipid bilayer
- overall concentrations of ions in ICF and ECF are not significantly affected
- due to different concentrations of ions on each side of the membrane and their respective permeabilities to it.
What ion is the major determinant of RMP
K+
Why is K the major determinant of RMP
as the cell membrane is normally much more permeable to K+ than other ions
When is the RMP established
When the amount of K+ leaving the cell down its conc grad is balanced by that moving back in due to the electrical gradient.
eg start with cell with K+ inside only
- conc grad cause K+ to leave the cell
- electrical grad attracts K+ back in
What must the membrane potential do for excitable tissues (nerve and muscle)
The membrane potential must change in order for them to function
- occurs via opening or closing of specific channels
How does membrane potential change
via opening or closing of specific channels
Two diseases where excitable tissues can’t function normally
- cardiac arrhythmias
- muscle weakness
What is the reference range
values of the regulated variable within acceptable limits
Why a reference range exists
For most physiological variables, body cells are
healthy over a range of values
• Within that range, predominantly gene.c factors determine different set points in different individuals (inter!individual varia%on)
• Varia%on may also occur within an individual (intra! individual varia%on)
“ variables fluctuate around the set point in response to normal ac%vity (within the acceptable range)
- e.g. core body temperature, blood glucose, BP, etc
How is the reference range established
- healthy group of people
- values within 2SD of the mean are considered “normal”
- 95%
- 5% of healthy people may fall outside reference range
Interindividual variation
Genetic factors eg males vs females
age
Intraindividual variation (2)
- in response to normal activity (within the acceptable range)
- eg core body temp, blood glucose, BP
- in response to biological rhythms eg hormones (but blood glucose isn't a biological rhythm)
Components of negative feedback
- Sensor
- Integrator
- Effector
- Communication pathways
Sensor
monitors actual value of the regulated variable
Integrator
- compares actual and set point values
- generates an “error signal” if any discrepancy between these
- determines and controls the response
- sensor and integrator can be the same cell
Effector
produce the responses that restores the regulated variable to its “set point”
Communication pathways
carries signals between components
Two physiological communications pathways
- Neuronal
2. Hormonal
Neuronal Pathway
- involves AP in axons and neurotransmitter release at synapses
- electrical impulse travel down axon and release neurotransmitter at axon terminal. Bind to receptors on target tissues and bring response
- FAST
- SPECIFIC: bring response to a specific group of cells
- good for when conditions are changing rapidly and where an immediate response is required to prevent tissue damage or loss or homeostatic control
- good for brief responses
Hormonal pathway
- endocrine cell = any cell that produces hormones
- hormones released into blood (or ECF)
- targets ANY cells that have receptors specific (bind to receptors) for the particular hormone, so one hormone can potentially affect several tissues or organs
- good for widespread, sustained responses eg fluid volume regulation
Which pathway is good for widespread, sustained responses
Hormonal
What pathway is good for fast and specific responses
Neuronal
Where is the thermoreceptor/integrator
Hypothalamus
Responses for cold
Cold receptors in the skin detect decreased external temperature and then hypothalamus compares predicted value with set point = feed forward
- decreased core temp detached by the hypothalamus in the brain
- nerve impulses to muscles = shivering = generate heat = inc body temp
- nerve impulses to blood vessels in skin = vasoconstriction
- muscle = piloerection = hair follicles stand.
Responses for hot
- vasodilation - bring warm blood to surface = lose heat
- sweat (evaporate)
- conduction
- convection
- radiation
Effective heat loss mechanisms when environmental temp > body temp
Radiation, conduction, convection are NOT effective heat loss mechanisms when environmental temp > body temp
- only method of heat loss is sweating.
Feedforward
Involves detection or anticipation of external (or internal) conditions or situations that COULD alter a regulated variable (or disrupt homeostasis) if some sort of PRE-EMPTIVE ACTION was not taken
- integration center establishes a future “predicted value” for the regulated variable, compares this with the “set-point” and makes anticipatory corrections
eg cold receptors in skin detect decreased external temp and then hypothalamus compares predicted value with set point = feed forward
Two types of feedforward
- behavioural eg putting on a jacket
- physiological eg goosebumps
Positive feedback
- moves controlled variable further away from the “set point”
- vicious cycle
- useful when there is a specific end point or purpose
- must be carefully controlled to prevent inappropriate activation and to limit outcome
Examples of positive feedback
- childbirth: end point when baby born
- blood clotting: platelets sticking = release stuff that attract more platelets. Needs to be very well controlled to not clot bloodstream
- must be carefully controlled to prevent inappropriate activation and to limit outcome
Why does the body lose heat faster to water than air
Water has a much greater specific heat than air, so can absorb far greater quantities of heat.
- heat conductivity in water is very great in comparison with air.
- consequently the body loses heat to water faster than to air AND it is virtually impossible for the body to heat a thin layer of water next to the skin to form an “insulating zone” as occurs in air.
How long can skeletal muscle cells be
up to 40mm
How are muscle cells arranged
- parallel
- cylindrical
- striated - protein arrangement (form a repeated alignment of contractile proteins)
- sheath formed by TYPE 1 COLLAGEN: useful to create huge forces
Properties of muscle cells
Multinuclear
- cells merged
- nuclei pushed aside from the cells otherwise would be in the way of contractile mechanisms.
Structures of muscle
- myofilaments in sarcomere = thick and thin proteins
- myofibril
- myofibre/myocyte
- sarcomere (= protein arrangement)
- sarcolemma
- sarcoplasmic reticulum
- sarcomere
- muscle fibre bundle
- muscle belly
- fascia: summative term for all connectives between muscles. Can be extended to tendons.
- tendons consist of the same type of substructure as fascia
- bone also consist of type I collagen (protein)
Muscle sheaths
- single muscle fibre wrapped by endomysium
- fibre bundle wrapped by perimysium
- epimysium wrap the entire muscle (belly) all the way around
Importance of perimysium
Blood vessels and nerves
Sarcomere
- contractile unit
- 2 µm
- actin and myosin fibres: actin frame each of the sarcomeres, cannot be changed in overall length
- end-on-end along myofibril length
- Z - line
- boundaries of sarcomere
- link actin filaments
2 key proteins of muscle
actin and myosin
- jointly function to enable contraction
2 key metabolites for contraction
ATP and Ca2+
- active sites carry ATP and have small arms
- under the use of ATP, help muscle fibres to contract
Is myosin the thick or thin filament
Thick
Z line I line and A line
Z - connection between one sarcomere and the next
I - in polarised light looks same irrespective of how you look at it. Have actin only
A line - in middle from one end of myosin to another. Consist of end of actin and myosin
Function of muscle
- movement
- heat production: shiver = skeletal muscles 20-30Hz. Create a huge amount of heat for heating up body
- posture
- communication
frequency of muscle shivering
20-30Hz
What happens in muscle shortening
Thin drawn towards each other over thick
- Z lines move closer together (1µm apart)
Important factors for muscle contraction
- actin and myosin interdigitate
- actin and myosin retain their length: shortening come from actin moving relative to myosin
- process consumes energy
- Ca2+ essential
Muscle form determines function (3)
- length of muscle fibres
- number of muscle fibres
- arrangement of muscle fibres
length of muscle fibres
- fibre can shorten up to 50% of resting length
- large ROM required means long muscle fibres needed
- length -> ROM
Number of muscle fibres
- tension (= force) is directly proportional to CSA
- greater number of fibres = greater CSA = grater tension
- origin at proximal
- insertion at distal
Arrangement of muscle fibres
Fibres oblique to muscle tendon
= pennate
- more fibres into same space
- reduced shortening but increased CSA
= FIBRE PACKING
Anatomical vs physiological CSA
- anatomical: cut muscle in standard anatomical plane = not representative of the max force the muscles can exert
- physiological CSA: muscles aligned to oblique = more force due to CSA = contract obliquely
- Anatomical CSA of straight and pennate are the same but physiological is different.
- higher for pennate
Do pennate fibres have more or less shortening and CSA
LESS shortening
MORE CSA
Pennate arrangement
- oblique to line of pull (uni-, bi-, multi-). Multi eg scapula eg rectus abdomens
- PSA for uni and bi and multipennate allows more fore than arranged longitudinally
Muscle tone
Even relaxed muscles are slightly active
- nerve impulses activating muscle fibres
- does NOT produce movement
- without nerves innervating muscles, can become hypertrophic or even atrophic
- synapses release ACh, which helps to depolarise the muscle cell to liberate Ca2+, thereby helping contraction
Function of muscle tone
Keeps muscles firm and healthy
- help stay metabolically active
- eg taking off cast = loss of proteins in muscle.
- become hypertrophic
- helps stabilise joints and maintain posture
Process of Synaptic transmission
- Action potential reaches the end of the motor neuron
- ACh released into the NMJ/synapse, which depolarises the muscle cell
- ACh diffuses across synaptic cleft and binds to ACh receptors on the motor endplate of the muscle fibre
- ACh receptors regenerate action potential (by allowing entry of Na+)
- AP propagates into the T-tubules
- Depolarisation of the T-tubule triggers Ca2+ release from the sarcoplasmic reticulum
2 fibre types
Fibre type I
Fibre type II
Fibre type I
- high enzyme activity
- aerobic, slow twitching: require O2 to stay active at all times
- eg for posture
- marathon runners
Fibre type II
- low enzyme activity
- anaerobic, fast twitching
- many contractions in a short time frame
- sprinters.
When does cartilage being to turn into bone
8 weeks
What is the process of transforming cartilage to bone called
Ossification
What does the cranial vault bones ossify from
Membranes, not cartilage
Where is the primary centre of ossification
Diaphysis
Where is the secondary centre of ossification
Epiphysis
Which centre ossifies first?
Epiphysis
Can there be more than one secondary center
yes
Function of secondary center
Bones meet at the ends at the joints
- those parts undergo different forces as we grow and move
- therefore need to develop separately to the primary centre
Epiphyseal plates
- made of cartilage
- as the bone grows in length, growth plate is continually turned into bone tissue
- at the top of growth plate = purely cartilage
- in the middle towards bottom, cartilage cells being transformed and destroyed by OB as OB’s job is to reproduce bone tissue, so OB form more bone tissue below themselves (At the the bottom of growth plate)
- therefore, at bottom = bone
- as you go up its transforming into bone
- at top = cartilage
- in tibia, growth = upwards
- at distal end = downwards
- in xray, more bone can be seen (As cartilage doesn’t show up)
Process of ossification (known..)
- known rate
- known sequence
- for estimating age
- for seeing if growth is normal
- eg which epiphyses should have been ossified at a certain age
- but difficult for different pop’s due to different growth standards in different countries etc
How does bone grow in length
- occurs through childhood
- through epiphyseal plates
- during adolescence, hormonal surge = growth spurt
- drop in hormonal surge at the end of adolescent support = growth plates transform completely into bone
If bones just grow longer, then bone would be thin so the shafts of the long bones must also grow thicker at the same time they are getting longer -> moulding.
Growth in width/moulding
OB in periosteum inc width
- OB lay down new bone to the outside of the shaft at the sub-periosteal surface (surface under the periosteum)
- on inner layer of periosteum, there are OB -> lay down new bone tissue on outside of shaft
OB from endosteum mood the bone shape and form the medullary cavity
- remove bone where it needs to be removed
- inside of diaphysis
- in endosteum
Dead bone = empty cavity.
- shaft = tube of thick compact bone
- in adults, filled with yellow marrow
- in children = filled with red marrow (entire bone is filled with red marrow) due to rapid and continual growth in length and width and moulding. Need high vascularisation to allow the bone to continue to grow
Epiphyseal fusion
fusion of the epiphyses to diaphyses (After growth is complete)
- occurs at a known rate and sequence
- can use for estimating age in skeletal populations and forensics
- measuring whether growth is normal
Late fusing epiphyses
- medial clavicle
- pelvis (Esp impt for females, into early twenties)
- all growth complete mid-twenties
bone pathology
an imbalance of OB or OC activity
How is bone homeostasis maintained
- diet high in Ca2+
- moderate exercise
- Ca2+ homeostasis maintained by OC and OB etc
Osteoporosis
OC take over OB
- OC take away more bone than OB can produce
Process of osteoporosis
- Compact bone become thinner and porous
- more vulnerable to fracture - Cancellous bone has a loss of volume
- COMPRESSION FRACTURES of vertebrae
- spine hunched as it is anterior
- trabeculae thinner as OC remove bone tissue
- fewer trabeculae
What happens to trabeculae in osteoporosis
- thinner as OC remove bone tissue
- fewer trabeculae
Causes of osteoporosis
- ageing- loss of estrogen, esp post-menopausal women
- lack of exercise: exercise stimulates bone cells to keep remodelling. Lack of exercise = don’t get signals to continue remodelling. Astronauts -> atrophy
- nutritional factors: diet high in Ca2+
- peak bone mass - bone as a bank
Stage 1 fracture healing
Vascular damage initiates the highly regulated process
Lots of bleeding due to high vascularisation
Soft tissue damage
- haematoma (immediately)
hepatoma quickly becomes “organised”, develops a firkin mesh, and transforms into a soft mass of granulation tissue containing inflammatory cells, fibroblasts, bone and cartilage forming cells and new capillaries.
- capillaries invade site and bring phagocytes
- phagocytes clean up debris
Stage 2 fracture healing
Been ends must be spliced so soft callus doesn’t break. Correct alignment
- FB (can differentiate into other cells)
- chondroblasts (differentiated from fibroblasts)
- fibrocartilaginous callus ( pro callus). Helps to anchor the ends of the fractured bone more firmly, but offer no structural rigidity for weight bearing.
- approx 3 weeks
Stage 3 fracture healing
- bony callus. 6 weeks for OB top turn cartilage into bone
- OB invade cartilaginous callus
- bony callus lasts for 3-4 months
How long does it take for OB to turn cartilage into bone
6 weeks
How long does the bony callus last for
3-4 months
How long does the soft callus last for
3-4 weeks
Stage 4 of fracture healing
- remodelling
- back into osteon network of mature bone
- take a few weeks
- 6 months for complete remodelling
Can see bony callus?
Not in children. In adults, process slowed down = can see lump.
Pseudoarthroses
False joint
- ends of bones continue to move on each other if not fixed
Closed, simple
- minimal soft tissue damage
- not a lot of movement of bones on each other
Open, compound
- displacement of bone ends
- bone can penetrate skin = lots of soft tissue damage (muscles, nerves)
- if bone goes outside of skin = prone to infection
Greenstick
- not a complete discontinuation of the bone
- more common in children as their bones not as mineralised
- can get fractures though epiphyseal plate.
Intramembranous ossification
A few flat bones are formed within fibrous membrane, rather than cartilage, in the process of intramembranous ossification
Endochondreal Ossification
- The cartilage model of a typical long bone, such as the tibia, can be identified early in embryonic life
- the cartilage model then develops a periosteum that soon enlarges and produces a ring, or collar, of bone.
- bone is deposited by OB, which differentiate from cells on the inner surface of the covering periosteum.
- soon after appearance of the ring of bone, the cartilage begins to calcify, and a primary ossification centre forms when a blood vessel enters the rapidly changing cartilage model at the midpoint of the diaphysis
- endochondral ossification progresses from the diaphysis toward each epiphysis, and the bone grows in length
- the process is called INTERSTITIAL GROWTH
- eventually, secondary ossification enters appear in the epiphyses, and bone growth proceeds toward the diaphysis from each end.
until bone growth in length is complete, a layer of the cartilage, known as the epiphyseal plate, remains between each epiphysis and the diaphysis.
- during periods of growth, proliferation of epiphyseal cartilage cells brings about a thickening of this layer.
- ossification of the additional cartilage nearest the diaphysis follows, that is, osteoblasts synthesise organic bone matrix, and the matrix undergoes calcification
- as a result, the bone becomes longer.
- it is the epiphyseal plate that allows the diaphysis of a long bone to inc in length.
Epiphyseal plate structure
4 layers:
- cells closest to epiphysis is composed of “resting” cartilage cells. These cells are not proliferating or undergoing change. This layer serves as a point of attachment firmly joining the epiphyses to the shaft
- proliferating zone: composed of cartilage cells that are undergoing active mitosis. As a result to mitotic division and increased cellular activity, the layer thickens and the plate as a whole increases in length.
- zone of hypertrophy: composed of older, enlarged cells that are undergoing degenerative changes associated with calcium deposition
- ossification zone: thin layer composed of dead or dying cartilage cells undergoing rapid calcification. As the process of calcification progresses, this layer becomes fragile and disintegrates. The restyling space is soon filled with new bone tissue, and the bone as a whole grows in length.
Direction of length inc of epiphyseal plate activity
Grows upwards at the proximal end
- grows downwards at distal end.
Process of bone remodelling
- the first osteons formed in lamellar bone are called primary osteons.
- to form a primary osteon, OC in the endosperm that surrounds a blood vessel first demineralise a cone or tube around a blood vessel.
- this leaves a cavelike hollow filled with collagenous fibres and lined with endosperm
- OB in the endosperm then form layer upon layer (lamellae) along the inside wall of the tube, trapping OCytes between the lamellae.
- eventually, the concentric lamella run out of space to mineralise - leaving only the central canal with its tightly packed blood vessels, nerves and lymphatic vessels
- as bone develops, primary osteons are later replaced through the same process with secondary osteons.
Bones grow at their outer margins by the ossification of fibrous tissue by OB
- long bones grow in diameter by the combined action of OB and OC
- OC enlarge the diameter of the medullary cavity by eating away the bone of its walls
- at the same time OB from the periosteum build new bone around the outside of the bone.
- by this dual process, a bone with a larger diameter and larger medullary cavity is produced from a smaller bone with a smaller medullary cavity.
What is important in homeostasis of blood Ca2+ levels
- remodelling activity of OC and OB
What two processes balance each other out
Ossification and reabsorption proceed concurrently.
- these opposing processes balance each other during the early to middle years of adulthood.
- the rate of bone formation equals the rate of bone destruction.
During childhood and adolescence, ossification occurs at a faster rate than bone reabsorption. therefore bone grow larger
Older:
- bone gain occurs slowly at the outer, or periosteal surfaces of bones
- bone loss at endosteal surfaces and takes place at a somewhat faster pace.
Remodelling of trabecula
under mechanical stress, cancellous bone remodels its trabecular in different directions and thicker diameters to better withstand the stress.
Remodelling in compact bone
formation of new (secondary osteons) when bones are stressed.
- the higher the mechanical load on a bone, the narrower the tube hollowed out by OC as they prepare for new osteon.
- thus the bones that bear the greatest weight have the narrowest osteons.
- these narrower osteons also have denser mineralisation
the dense mineralisation along with more numerous, narrower osteons gives the bone great strength to resist the stress.
What is a joint
- hold bones together
- where bones meet = articulation
- involves bone shapes and soft tissues
- allow free movement/or control movement
Soft tissues associated with joints
- have no inorganic component
- cartilage:
1. fibrocartilage
2. hyaline/articular cartilage - find hyaline cartilage between ends ribs and sternum, and cartilage model that the skeleton begins growing from
- growth plate is also hyaline cartilage
What type of cartilage is the cartilaginous model
Hyaline
What type of cartilage is growth plate
Hyaline cartilage
General cartilage composition
- collagen fibres in a ground substance. Collagen = protein. In FIBRES
- chondrocytes (produce ECM) live in lacuna
- nutrients diffused through by matrix by JOINT LOADING- i.e. not vascular
- osteon unit distribute nutrients to bone. Done by vascularisation
- for cartilage, only way nutrients can get diffused to the chondrocytes is by loading into the cartilage -> i.e. by normal movement of the body
- not vascular -> need to push tough tissue to stay alive. Can’t regenerate like bone can.
Which cartilage has amorphous structure
Hyaline
Compare collagen fibre arrangement in hyaline vs fibro
In hyaline - collagen fibres barely visible
In fibrocartilage - collagen fibres form bundles throughout matrix
Which cartilage have more collagen
Hyaline has less collagen than fibrocartilage
How is collagen fibres aligned in fibrocartilage
- orientation of fibres aligns with stresses
Which type of cartilage has high water content in matrix
Hyaline
Function of hyaline cartilage
- resist compression only DUE TO HIGH WATER CONTENT
- resist compression ONLY, not tension (whereas fibrocartilage does resist compression)
- provide frictionless surface for movement of bones in synovial joints
Function of fibrocartilage
- resist compression (due to ground substance)
- resist tension AS WELL
Example of fibrocartilage
Meniscus of knee joint = concave discs of fibrocartilage
- deepens articulation at knee
- can adapt its shape to stresses on joint in movement
how does hyaline cartilage attach
Moulds to surface of the bones where they articulate
How does hyaline cartilage degrade
- degrades with age (lose water content, becomes friable and brittle) -> osteoarthritis
- degrades with trauma
Bony congruence
sum of the bone surfaces that form an articulation
- less BC = more soft tissue support
eg femoral head’s entire head is covered by hip socket = less soft tissue support needed
- eg in shoulder, very shallow bony articulation = less bony congruence cf hip = more vulnerable to injury. Most of the support is from muscles
Meniscus of the knee location
Sit on top of the hyaline cartilage that’s sitting on top of the bone
What is the meniscus
- concave discs of fibrocartilage
- deepen the articulation at the knee joint
- where femur articulates with knee is flat, therefore deepening of the articulation help stabilise knee joint
- can adapt shape to stresses on joint in movement
- anchored to bone on outer surface
- more loose on inside, able to move
Can the meniscus adapt shape to stresses on joint in movement
Yes
Inside of meniscus vs outside
- anchored to bone on outer surface
- more loose on inside, able to move
Force distribution over meniscus
- forces from above, through knee down tibia and into foot
- presence of meniscus = diffuse forces from above over a wider area over the tibia -> resist compression
- if removed = no cushioning, forces come into a smaller area of tibia = articular cartilage more likely to be damaged -> osteoarthritis
Cartilage in intervertebral disc
- cartilaginous joint
- anchored onto bone by a small ligament
- rings show how collagen is aligned = can resist tensile forces from all directions
- nucleus pulposus = fell-like, squishy ball bearing.
- can be compressed and can move with the movement of torso.
What is a slipped disc
Nucleus purposes gets squished out
- if tear is posterior, then impact on spinal cord
- if lateral, can impact on spinal nerves
What are ligaments and tendons made of
DFCT
DFCT
fibres as main matrix element.
- type 1 collagen
- crowded between collagen fibres are rows of fibroblasts that generate fibres.
- form strong, rope-like structures eg tendons and ligaments
How is collagen aligned in DFCT
in one direction
What are the cells that make up DFCT
Fibroblasts(cites) that mature into firbocytes.
- embedded in matrix
Function of ligaments and tendons
resist tension
Is there vascularity in ligaments and tendons
Some vascularity but minimal compared to bone
- therefore very slow healing compared to bone which is highly vascularised
Ligaments
Bone to bone
Function of ligaments
Restrict movement (inside and around joints) - movement is restricted away from itself - eg lateral restricts adduction - eg medial restricts abduction eg ankle: weight through ankle. Don't want ankle to move medially or laterally.
Do ligaments stretch
No.
- placed in such a way that restricts movement
How long for ankle repairmen (of ligament)
3 months to repair 50% of normal strength of ligament
- up to a year for 90%
Tendons
Muscle to bone
Function of tendons
On outside of muscle belly has fibrous sheath. Sheet merges into DCFT of tendon.
- tendon inserts into bone
- contraction of bone -> shortens -> pulls on tendon -> tendon pulls on bone. Occur because made of DFCT which will not lengthen if pulled on as it is to resist tension
Function = facilitates and controls movement
- contraction
Do tendons stretch
No
- it resists tension
How does over adduction affect ligament
Ligament pull away from bone = damage to bone as well
- evulsion fracture.
Another name for fibrous joints
Synarthroses
Another name for cartilaginous joints
Amphiarthroses
Another name for synovial joints
Diarthroses
What tissue makes up fibrous joints
DFCT
- function of DFCT is to resist tension
What tissue makes up cartilaginous joints
Fibrocartilage
- resists compression and tension
What tissue makes up synovial joints
All of the tissues
- hyaline cartilage
- fibrocartilage
- DFCT
What is the structure of fibrous joints
Ligament
- goes directly between 2 bones and articulates them and joins them together
What is the structure of synovial joints
- articular cartilage
- subchondral bone is smooth
Function of fibrous joints
limited movt/stability
Function of cartilaginous joints
Some movement
- special functions and various structures
- find where compressive forces and some movt between the bones
Function of synovial joints
Free-moving
- most limb joints
example of fibrous joints
- cranial suture (principal function is to protect the brain)
- distal tibiofibula joint (weight of body going through ankle -> don’t want tibia and fibula to move apart = more vulnerable to injury
- between roots of teeth and jaw bone
Example of cartilaginous joints
- intervertebral disc = structure
- pubic symphysis = joint. Anterior of pelvic girdle
- need some movement because all forces go through posterior part of pelvic girdle, but still go to the anterior part. If had fibrous joint that does not allow any movement = more vulnerable to injury
Example of synovial joints
hip
knee
Structure of Synovial joints
- complex association of tissues and structures
- facilitation of free movement AND control of movement
- bone ends determine the range of motion at a knee joint
hip vs knee
- hip: lots of bony congruence due to hip socket = stable Less soft tissue support needed
- knee: fibrocartilage meniscus deepen the articulation and make up for lack of bony congruence. Lots of soft tissue support
- articular cartilage covers bone ends where they articulate AND move over each other
- subchondral bone is smooth (cf roughed areas where ligaments and muscles attach)
Capsular ligament/joint capsule function
Hold bones together
- go around and insert into the other bone
Structure of joint capsule
- tight and thick where more support is required
- thickening of capsule where more support is required
- losse and thin on sides where movement is allowed
- collateral ligaments of knee
- eg knee: thick tight ligaments on medial and lateral. Don’t want tibia to move side to side on femur, but thin and loose on posterior and anterior aspects to allow flexion and extension.
- very thin and loose on shoulder joint, therefore support must come from other structures -> muscles
- potential space
- not a real space. If there is a space: due to trauma or synovial fluid being produced in response to trauma.
- synovial membrane lines the inner surface of the capsule and secretes synovial fluid = lubrication of joint
Collateral ligaments of knee
Medial restricts abduction
Lateral restricts adduction
eg phalanges also have collateral ligaments (part of joint capsule)
Function of intracapsular ligaments
- restricts movement between bones
- stop femur from moving anteriorly or posteriorly on the tibia
- eg going up stairs, femur slide off posteriorly tibia
going down, femur slide off anterior off tibia
Eg of intracapsular ligaments
- cruciate ligaments
- arise form tibia and insert into femur
- ACL restricts posterior displacement of femur
- PCL restricts anterior displacement of femur
- can be damaged from external forces: fixation of tibia but rest of body still moves eg skiing
What is meniscus made of
Fibrocartilage
- deepening articulation between femur and tibia
- diffuse compressive forces
Structural difference between fibrous joint and synovial joint
Fibrous joint and cartilaginous joints: tissues glue bones together to either stop movement entirely or allow some movement
Synovial - capsule goes from one bone to another. Leaves bone ends free to move over each other.
What is the reference range
The values of a controlled variable that is within an acceptable range
Where are hormonal signals transmitted
Via the blood stream
Type I diabetes mellitus
When the patient cannot produce insulin in response to stimuli
When does the diaphysis fuse to the epiphyses, hence ceasing vertical growth?
Adolescence
Does fibrocartilage have a high water content to resist compression
NO
hyaline does
Cells of DFCT
Fibrocytes/fibroblasts
Why is there a reference range rather than a single correct value
- within that range, genetic factors can determine different set points in different individuals
- set point may change in a regular way in response to biological rhythm
- body cells are healthy over a range of values
- variables fluctuate around the set point in response to normal activity (within an acceptable range)
NOT because different individuals have different levels of homeostatic strength
How does the hormonal communication systems work
Targeting by expression of specific receptors on target cells
What’s the time frame for soft callus formation
3 days to 2 weeks
- fibroblasts differentiate into chondroblasts to form a fibrocartilaginous callus
What happens in remodelling of bone in middle-aged adult?
Ossification proceeds concurrently with resorption at equal rates.
How do OCytes in cancellous bone receive blood and nutrients
normal blood supply because OCytes are not embedded in a hard matrix
Purpose of menisci
To inc bony congruence in the joint
help with normal movement of the joint
to help stabilise the joint
to distribute weight over a large area
Function of T tubules
To conduct impulses into the muscle cell
In mid swing, the knee starts to extend. It is INITIALLY controlled by
Gravity
During mid stance what MAIN role does the quadriceps femoris play?
Stabilising
When human run, what is it called when both feet are on the ground?
No time when both feet are on the ground
Double stance
when both feet are on the ground
What mainly helps to keep us stable when standing (i.e. not falling over flat on our face)
Soleus
Two factors that determine peripheral skin temperature?
Room temperature and clothing
Muscle structure
- myofilaments in sarcomere (thick and thin)
- myofibrils
- myocyte
- sarcoplasmic reticulum
- sarcolemma
- muscle bundle
- muscle belly
- fascia
Epimysium
around entire muscle
perimysium
around muscle fibre bundles
important of perimysium
key structure to supply vascular supply and nerve supply to muscles
- allowing sliding of the muscle fascicles one relative to the other
- otherwise will have “shear off” phenomena and mechanical muscle destruction whenever contracts.
Endomysium
connect sheath around muscle fibre
Is myosin thicker than actin
yes
What is the human mscuoloskeletal system and its motion mainly based on
proteins - muscle - ligaments - tendons Not all of these proteins are contractile, but allow for locomotion.
What is muscle function largely driven by
nerves
Where do nerves that drive an excitation that causes a contraction sit?
at the ventral root of spinal cord
- must travel axon all the way down
How far does the axon go? (muscle)
only go as far as the proximal insertion of a muscle begins
- as proximal as possible
- to inc velocity of signal transduction
- to save material (to save material of axon)
What is the feedback of the NMJ provided by
- feedback provided by the spinal root and root ganglion (which sits slightly outside spinal cord)
- receives feedback of how the muscle is situated in space
- signals integrated from tendons and muscles are integrated via the nerves that are situated in the spinal root ganglion.
Transformation of signals
Electrical -> chemical -> electrical.
motor endplates
Com from axons of neurons
- for skeletal muscles, those axons are myelinated
Chemical signal diffusion
Diffusion signal takes a long time
- therefore at the outer surface of axon, have an electrical signal (time-saving mechanism)
Transformation of signal
Signal from spinal cord to the terminals of axons electrically
- electrical stimuli transmitted into neurotransmitters -> Ash (also for smooth muscle contractions as well)
- ACH in synaptic cleft can also become the site of neurological diseases -> myasthenia graves
- muscle cells, due to ACH, retransfers the chemical signal back to electrical, to twitch up to 30Hz
Cellular components involved in contraction
NMJ Sarcolemma T tubules (transport Ca2+ and make available in the muscle fibres so they can contract simultaneously) SR Ca2+
Why is Ca2+ so important for contraction?
Ca2+ is responsible for the ends of the myosin to make a movement to allow contraction
- movement of the ends of the myosin proteins (hundreds)
- Ca2+ bound in the ER when not contracting, but released upon contraction.
- tropomyosin between actin strands, which makes available myosin binding sites
- which cannot be attached unless Ca2+ is liberated
What does ATP and Ca2+ do?
Under the influence of ATP and Ca2+, the proteins, without changing length, approach each other, allowing muscle shortening.
What is the motor unit
all the muscle fibres being innervated by a single nerve fibre
- motor neuron
- axon
- branches
- plus ALL the muscle fibres it innervates
- size varies
Precise vs forceful contractions due to motor unit size
Eye muscles
- capable of making small, tiny movements
- tiny movements possible by a few fibres being innervated by a single motor neurone
- max of 30 fibres/motor neuron
- refined
Quadriceps femoris
- huge motor units
- up to 2000 fibres/unit
- forceful and powerful contraction
- huge force to ground and to joints
Myasthenia gravas
Neuromuscular disease
- auto antibodies act against receptors of ACh
- cannot open their eyes properly
- due to the eye of the muscles around the eye (huge number of muscle fibres) are using and wasting ACh within the synaptic cleft
- diplopia - seeing 2 images at the same time
- can’t contract diaphragm -> being unable to breathe by themselves.
Displayed activation of fibres
Motor unit displays ALL or NONE activation of fibres
- different sizes of motor units = graded range of contraction
- how is the force of contraction of whole muscle then graded?
How is the force of contraction of whole muscle graded
- not only by the number of excitations from the nerve fibres
- also come from the number of fibres being excited to get a muscle contracted
What does the force of contraction of whole muscle depend on (3)
- characteristics of muscle fibres: length, number, arrangement
- characteristics of motor units: size, number, rate of firing that the motor neurone in the spinal cord generates
- muscle attachments: size, number, rate of firing
Anatomical lever
bone = lever
- bones do not independently move without muscle
- for arm flexion, the ulna and radius are the bones that act as levers
joint = pivot
load = external or internal eg just your hand
muscle contraction = pull
Type I lever
pivot in middle between force and resistance
Type one lever function
Stabilise joint position
- prevent head drooping
- force of gravity on opposite side compared to muscle contraction
Type 2 lever
Axis -> resistance -> force
Type 2 lever function
effective at overcoming loads
- axis of motion is distant compared to both resistance and force
- resistance between axis and force
eg standing on tip toes
- balls of feet = axis
- achilles tendon = force
- ankle = resistance
Type 3 lever
Axis -> force -> resistance
Type 3 lever function
- large range of movement and speed
- force between resistance and axis
- huge lever
What allows a muscle to be lengthened
An opposing muscle or gravity
eg extension at elbow from a flexed position
- in most cases, an eccentric muscle or a neutralisation of a joint position is taking place by gravity
- eg jaw TMD drops during talking due to gravity, but contract actively back up.
Which muscle action involves the muscle being active and developing tnsion
Concentric
Static/isometric
Eccentric
Which muscle action involves a change in joint position
Concentric and eccentric
isometric does NOT result in a change in joint position
How does muscle length change for each of the muscle actions
Shortened in concentric
No change for isometric
Lengthened for eccentric.
Which type of lever allows for a large range of movement and speed
type 3
Agonist
- exert a certain movement at a certain joint position
eg BB shortens - act concentrically
Antagonist
- opposes agonist
- supported by muscles on the opposite side on the relative joint
- TB -> lengthens
- act eccentrically
Stabiliser
- when a muscle is active to hold a joint STILL
eg holding a heavy book
BB = stabiliser
BB = isometric
no change in the length of BB
eg quads when standing
- do not have to sit on either side of the joint
- guide movement
- save energy
Neutraliser
Muscle eliminates an unwanted movement caused by another muscle
- can eliminate unwanted movement by another muscle (stabilising)
- but can also restore initial joint position without acting on the joint with large force
eg BB - drinking from a glass - flexion - yes - supernation - no "pronator" muscle neutralise supinating effect of BB
Functions of the skeleton
- support
- movement
- protection
- storage
- RBC formation
Where is compact bone found
WHere strength and load bearing needed
Where is cancellous bone found
Where shock absorption is needed
Function of long bones
levers for movt
Function for short bones
weightbearing/shock absorption
Function of flat bones
protection - cranial bones
muscle attachemnt - scapula
Structure of long bone
longer than wide
diaphysis and epiphyses
thicker compact bone in shaft
Structure of short bones
near equal width and length
mostly cancellous bone
Structure of flat bones
thin plates of compact bone - some cancellous
Axial skeleton
Skull:
- cranium: frontal, parietal, occipital, temporal
- facial bone
- mandible
Vertebral column
- cervical (7)
- thoracic (12)
- lumbar (5)
- sacrum (5 fused)
- coccyx (2-5 fused)
Rib cage
- ribs
- sternum
Appendicular skeleton
- limbs
- regions: arm, forearm, thigh, leg
What is the upper limb designed for
Manipulation
What is the lower limb designed for
Stability and locomotion
Structure of limbs
single proximal long bone
two distal long bones
hands and feet
Attachment
pectoral girdle: clavicle and scapula
pelvic girdle: hip bones (2) and sacrum
Bones of forearm
radius and ulna
bones of leg
tibia
fibula
bones of hand
carpals (8)
metacarpals (5)
phalanges (3x 4 + 2)
Bones of foot
tarsals (7)
metatarsals (5)
phalanges (3)
Bursae
Synovial membrane and enclosed products.
if fully enclosed and independent of the joint, but still provides cushioning = bursae
- if it communicates = recess
Homeostasis of glucose
Pancreas: (Receptor/Controller) Receives input (glucose level) and releases appropriate hormone
Liver (also muscle and body cells): (Effector)
Liver and muscle cells store or release glucose as appropriate, other body cells can take up excess glucose for use in respiration but can’t store it
Blood system:
Transports hormones from pancreas, throughout body to liver, muscle and body cells
When we eat food, carbohydrates are digested and broken down into glucose.
This increases our blood glucose level
So the pancreas releases the hormone insulin, which allows the glucose to move from the blood into cells where the glucose is converted into ATP in the mitochondria (respiration), or converted to glycogen in the liver (and muscles) for storage.
Blood glucose drops, insulin production stops, no more glucose leaves the blood.
When we haven’t eaten for a while or exercise, glucose is used up in cellular respiration.
This decreases our blood glucose level
So the pancreas releases the hormone glucagon, which allows to break down of glycogen in the liver and muscle cells into glucose which is released into the blood.
Blood glucose increases, glucagon production stops, no more glucose enters the blood.
What do growth plates allow
Provide a convenient means of allowing growth of a long bone without distorting the intricate shape at the joint surface.
Where does bone thickening and bone removal occur
Thickening of bone occurs at subperiosteal surface
Bone removed/resorbed by OC at the endosteal surface
How is bone removed
OC remove bone by releasing lysosomes and acid
- enzymes break down the organic part of bone tissue, and acid breaks down the inorganic part.
Factors predisposing to osteoporosis
Lack of biomechanical stress (lack of exercise, reduced gravity, paralysis)
Diet lacking in Ca2+
Cigarette smoking
Use of corticosteroids
Interference with oestrogen production
When does stage 1 occur
0 -3 days
When does stage 2 occur
3 days to 2 weeks
What is the soft callus made of
Fibrocartilage
how is the soft callus formed
Fibroblasts enter, produce collagen fibres
- some cells differentiate into chondroblasts
When does stage 3 occur
3-4 weeks
What happens in stage 3
OB transforms the fibrocartilage callus into a bony callus
What bone makes up the bony callus
cancellous bone
When does stage 4 occur
2-3 months
How long may remodelling take
up to 2 years
What influences final shape of bone
quality of “setting”
reduction of fracture
Does the thickness of epiphyseal plate change when bone lengthens
No.
- bottom layer of calcified cartilage becomes bone.
- bone added to diaphysis
Features of quadrupelda standing
Base of support
legs flexed at several joints
energetic expenditure
Features of biepdal standing
Relatively small area of contact
plantar surface of feet
energy efficient
Where is the line of gravity in relationship to hip, ankle and knee
Posterior to hip
anterior to ankle
anterior to knee
What happens to hip joint when standing
Joint pushed into extension
- extension = ligaments are tight = LOCKED
- capsular ligaments of the hip joint are spiral -> don’t need contraction of quads or iliopsoas just when standing = prevent from falling back
Is the hip joint locked when standing
yes
What happens to the knee when standing
Joint pushed into extension
extension = ligaments are tight = LOCKED
IS THE KNEE JOINT LOCKED WHEN STANDING
YES
What happens to the ankle when standing
falls into dorsal extension
NOT LOCKED
plantar flexors stabiliser
energy consumed
Is the ankle joint locked when standing
NO
Is energy consumed at the ankle joint when standing
yes
bipedal stadngin summary
feet form base of support but insufficient size to provide only balance solution
- standing achieved with very little muscle effort - mot at ankle joint
- gait is characteristics
- gait is learnt.
when does primary ossification occur
when a blood vessel enters the cartilage model at the diaphysis
