Musculoskeletal Flashcards
1
Q
How many bones in the adult human body?
A
206 bones
2
Q
How many bones are we born with?
A
- 300 bones at birth.
- These eventually fuse to form the 206 bones that adults have
3
Q
Purposes of the skeleton
8 points
A
1) Raises us from the ground against gravity
2) Determines basic body shape
3) Transmits body weight
4) Forms jointed lever system for movement
5) Protects vital structures from damage
6) Houses bone marrow
7) Hematopoiesis
8) Mineral storage
4
Q
What minerals are stored by the skeleton?
A
calcium, phosphorus, magnesium
5
Q
The skeleton is divided into two types of skeleton, what are they?
A
1) AXIAL
2) APPENDICULAR
6
Q
Describe the axial skeleton
A
1) 80 bones
2) Forms the central axis of the body
3) Consists of the skull, vertebral column, and thoracic cage
7
Q
Describe the appendicular skeleton
A
1) 126 bones
2) the part of the skeleton consisting of the limbs and the supporting pectoral and pelvic girdles.
8
Q
Bone Classification by shape
5 points
A
1) Long bone
2) Short bone
3) Flat bone
4) Irregular bone
5) Sesamoid bone
9
Q
Long bones
- describe this type
- purpose
- examples
A
1) tubular shape with hallow shaft and ends expanded
2) For articulation with other bones
3) LOWER LIMB BONES: tibia, fibula, femur, metatarsals, and phalanges
UPPER LIMB BONES : the humerus, radius, ulna, metacarpals, and phalanges, clavicle
10
Q
Short bones
- describe this type
- purpose
- examples
A
1) Cuboid in shape
2) to provide support and stability with little to no movement
3) Carpals in wrists, tarsals in ankles
11
Q
Flat bones
- describe this type
- purpose
- examples
A
1) Plates of bone, often curved
2) Protective function
3) Sternum, scapula, ribs, cranial
12
Q
Irregular bones
- describe this type
- purpose
- examples
A
1) various shapes
2) protection, attachment, support
3) vertebrae, sacrum, coccyx, temporal, sphenoid, ethmoid, zygomatic, maxilla, mandible, palatine, inferior nasal concha, and hyoid
13
Q
How many irregular bones in the spine?
A
33 bones
14
Q
Sesamoid bones
- describe this type
- purpose
- examples
A
1) round, oval nodules in a tendon
2) modify pressure, to diminish friction, alter the direction of a muscle pull.
3) patella, in the hand next to metacarpals
15
Q
Type of bone structure
Macro
A
1) Cortical
2) Trabecular
16
Q
Describe cortical bones
A
- Compact
- Dense
- Solid
- Only spaces are for cells and blood vessels
17
Q
Describe Trabecular bones
A
- Cancellous
- Spongy
- Network of bony struts (trabeculae)
- Looks like a sponge
- Many holes filled with bone marrow
- Cells reside in trabeculae and blood vessels in holes
18
Q
Type of bone structure
micro
A
1) woven bone
these are then rearranged into
2) Lamellar bone
19
Q
Describe woven bones
4 points
A
- made quickly
- disorganised
- no clear structure
- immature bone
20
Q
Describe lamellar bone
3 points
A
- made slowly
- organised
- layered structure
21
Q
How does each one of these structures contribute to the function of the whole bone:
a) Hollow long bone
b) Trabecular bone
c) Wide ends
d) Flat bones
A
a)
- keeps mass away from neutral axis
- minimises deformation
b)
- gives structural support
- whilst minimising mass
c)
- spreads load over weak low friction surface
d)
- protective
22
Q
Bone composition of the adult mammalian bone:
(3 points) + Percentage of each
A
1) 50- 70% = BONE MINERAL
2) 20-40% = ORGANIC MATRIX
3) 5- 10% = WATER
23
Q
what is bone mineral composed of?
A
Hydroxyapatite, a crystalline form of Calcium Phosphate
24
Q
what is the organic matrix of bone composed of?
A
1) Collagen (type 1)
90% of all protein
2) Non-collagenous proteins 10% of all protein
25
What is the intercation between collagen and minerals in bone?
The collagen assembles in fibrils with mineral crystals situated in ‘gap’ regions between them.
SEE PICTURE IN NOTES
26
Why is bone described as a composite?
You have a mix of collagen and mineral
27
How does bone micro structure contribute to function?
1) Bone is a composite
2) You have collagen and minerals
3) Collagen provides elasticity
4) Mineral provides stiffness
28
State the cells of the bone
1) Osteoclast
2) Osteoblast
3) Osteocyte
4) Bone lining cell
29
which type of bone cell is most abundant?
Osteocyte
30
SEE histology picture of cells of bone and identify each
1) Osteoclast
2) Osteoblast
3) Osteocyte
4) Bone lining cell
31
Describe Osteoclast
1) How to distinguish
2) Origin
1) Multi nucleated
| 2) Hematopoietic stem cell
32
Function of osteoCLASTS
| 4 points
1) Resorb Bone (break down)
2) Dissolve the mineralised matrix (acid)
3) Breakdown the collagen in bone (enzymatic)
4) High expression of TRAP and Cathepsin K
33
Describe Osteoblasts
1) how to distinguish
2) origin
1) plump, cuboidal
| 2) Mesenchymal stem cell
34
Function of osteoBLASTS
| 6 points
1) Form Bone - in form of osteoid
2) Produce Type I collagen
3) Mineralize the extracellular matrix by depositing hydroxyapatite crystal within collagen Fibrils
4) High Alkaline Phosphatase activity
5) Make non-collagenous proteins
6) Secrete factors that regulate osteoclasts ie RANKL
35
describe Osteocytes
1) how to distinguish
2) origin
3) function
1) Stellate (arranged like stars), Entombed in bone
2) Derived from osteoblasts
3) Coordinate our bones
36
Describe Bone Lining Cell
1) how to distinguish
2) origin
3) function
1) Flattened
2) previously active osteoblasts that have entered a quiescent phase
3)
- They regulate passage of calcium into and out of the bone
- They respond to hormones by making special proteins that activate the osteoclasts
37
What is modelling of bone?
Gross shape is altered, bone added or taken away
38
What is remodelling of bone?
All of the bone is altered, new bone replaces old bone
39
describe how age changes modelling/remodelling of bone
0-20 yrs = development stage so modelling
20-50 = maintenance stage so remodelling
50+= Accquired pathology
40
Describe resting phase to activation of bone to formation of bone.
1) Activation from breakage from either defect in bone or pregnant
2) The osteoclasts resolve the bone to a set level, as tightly coordinated
3) Osteoblasts fill the bone with new bone
41
how do osteoblasts work with osteoclasts?
1) Osteoblasts ----------> new woven bone
2) Osteoclasts ---------->mop up dead bone
remodel strong bone
3) Osteoblasts --------->lay down lamella bone
42
Reason for bone remodelling
| 6 points
1) Form bone shape
2) Replace woven bone with lamellar bone
3) Reorientate fibrils and trabeculae in favourable direction for mechanical strength
4) Response to loading (exercise)
5) Repair damage
6) Obtain calcium
43
What does Dysregulated remodelling lead to?
Dysregulated remodelling = disease!
44
What is the actual term for brittle bones? what is it a defect in?
Osteogenesis imperfecta - collagen defect
45
What happens in osteoporosis?
- Resorption exceeding formation
- You can see the vertebral trabeculae when 80 is much thinner
- Some parts are broken down
46
Osteopetrosis
- no osteoclasts
| - dense bones
47
Paget's disease
overactive osteoclasts
| focal bone turnover
48
Primary bone cancer
- name
- symptoms
- Osteosarcoma
Primary bone cancer symptoms
- Bone pain especially at night
- Pathological fracture
- bone/soft tissue swelling
49
Anti- catabolic treatment
They stop the osteoclasts from breaking the bones down
50
Anabolic treatment
They stimulate the osteoblasts to make more
51
How often is the skeleton replaced?
every 10 years
52
what are osteocytes?
when osteoid is mineralised with crystals of hydroxyapetite, the osteoblasts are trapped within the bone and become less synthetically active osteocytes
53
what are osteoclasts?
Large and multinucleated bone resorbing cells. They contain large amounts of lysosomes.
54
Name 2 types of enzymes that are important in bone remodelling.
1) collagenases
| 2) Matrix metalloproteinases
55
what type of bone does endochondral ossification produce?
Long bone
56
what type of bone does intramembranous ossification produce?
Flat bones
57
what type of bone formation uses a cartilaginous pro-former?
endochondral ossification
58
Briefly describe process of endochondral ossification
1) begins with the creation of hyaline cartilage proformers
2) a bony collar is then established around the diaphysis
3) Blood vessels penetrate the bony collar and bring in osteoprogenitor cells.
4) A primary centre of ossification is established. Osteoblasts lay down primary bone
5) A secondary centre of ossification is established in the epiphyses.
6) the amount of cartilage present decreases and is restricted to just to the growth plates
59
Briefly describe the process of intramembranous ossification.
1. Bone is directly deposited into mesenchymal tissue.
2. Osteoblasts deposit isolated islands of bone until a plate of primary bone has been created.
3. This primary bone is then replaced with denser, lamellar, secondary bone.
60
Describe primary/ woven bone
- newly formed
- poorly organised
- calcium is in an amorphous form
- this bone is heavy and weak
61
Describe secondary bone
- organised collagen
- calcium is in a crystalline form (hydroxyapatite).
- This bone is lighter and stronger and replaces primary bone.
62
In the blood approximately how much calcium is bound to plasma proteins?
about 50%, notably albumin
63
in the blood approximately how much calcium is ionised?
just less than half
64
in the blood approx how much calcium is complexed? to what?
A very small amount is complexed, bound to citrate/phosphate etc.
65
What are the 3 ways in which the calcium in the blood is distributed?
1) IONISED= metabolically active and is the most important for cellular function
2) BOUND TO PLASMA PROTEINS- non metabolically active
3) COMPLEXED- e.g citrate, phosphate
66
What is the affect of alkalosis on ionised calcium?
1) Alkalosis increases the pH
2) This increases the negative charge on albumin
3) So affects ionisation as MORE calcium binds to albumin and LESS IS IONISED
67
Give 4 sources of calcium
1. Dairy products.
2. Oily fish.
3. Cereal.
4. Broccoli.
68
Where in the intestine is calcium actively absorbed?
Duodenum and jejunum.
69
Where in the intestine is calcium passively absorbed?
Ileum and colon
70
Where in the intestine is calcium passively absorbed?
PCT
71
Where does active Ca2+ reabsorption happen in the kidney?
DCT - this is where PTH will act
72
Where in the body can Calcium come from to enter the blood?
1. Absorbed from the intestine.
2. Resorbed from bone.
3. Reabsorbed at the kidney.
73
What stimulates the release of PTH?
Low serum Ca2+ detected by receptors in the parathyroid.
74
Briefly describe the action of PTH.
1. It causes bone resorption: increased Ca2+ and phosphate.
2. It acts on the kidneys causing increased Ca2+ reabsorption and decreased phosphate reabsorption.
3. It stimulates 1-hydroxylase which increases formation of 1,25-(OH)2-vitD and so increases the absorption of Ca2+ and phosphate from the intestine.
75
Where in the kidney does PTH act?
On the DCT where active reabsorption of Ca2+ takes place.
76
What do C-cells release?
calcitonin
77
What triggers the release of calcitonin?
High Ca2+.
78
What is the action of calcitonin?
It reduces bone resorption and so lowers Ca2. It is the antagonist to PTH.
79
What is the affect of low phosphate levels in the body?
Poor mineralisation of bone which can result in rickets, osteomalacia, pain and fractures etc.
80
Give 3 dietary sources of phosphate.
1. Protein.
2. Dairy.
3. Seeds and nuts.
81
Give 3 regulators of phosphate.
1. PTH.
2. 1,25-(OH)2-vitD.
3. FGF-23 = major regulator!
82
What is the action of PTH with regards to phosphate homeostasis?
It increases phosphate absorption at the intestine and decreases phosphate reabsorption at the kidney.
83
What triggers the release of FGF-23?
1. High phosphate levels.
2. PTH.
3. 1,25-(OH)2-vitD.
84
What is the action of FGF-23?
It acts to decrease phosphate levels!
1. It increases phosphate excretion at the kidneys.
2. It decreases 1-hydroxylase meaning less 1,25-(OH)2-vitD is produced and so less phosphate will be absorbed from the intestine.
85
What is the function of PHEX?
It breaks down FGF-23 when phosphate levels have decreased.
86
What could happen if there was a dysfunction of PHEX?
FGF-23 wouldn't be broken down and so serum phosphate would be very low and urinary phosphate would be high. You would be unable to mineralise bone - osteomalacia.
87
What is klotho and what is its function?
Klotho is a transmembrane protein that modifies FGF receptors making them specific for FGF-23.
88
What would be the affect on FGF-23 if you were vitamin D deficient?
1) You would have low phosphate levels as less will be absorbed from the intestine
2) So FGF-23 would be low as its trigger is high phosphate levels.
--
89
Define coupling
Bone formation occurs at sites of previous resorption
90
Define balance in osteoblast/osteoclast communication.
The amount of bone removed by osteoclasts should be replaced by osteoblastic activity.
91
What cell releases RANK ligand?
Osteoblasts.
92
Function of RANK- ligand?
It is essential for osteoclast formation, activation and survival.
93
What is OPG?
OPG inhibits osteoclast formation, function and survival.
94
How does OPG work?
It has a similar binding site as the RANK receptor and so binds RANK ligands which prevents them from stimulating osteoclasts.
95
Name 2 things that regulate the balance between OPG and RANK?
Cytokines and hormones.
96
What would be the affect on bone if you had unopposed RANK ligands?
1) lack of OPG
2) more osteoclasts stimulated
3) increased bone loss
97
What is the affect of increased activity (load) on bone?
Increased activity means there are higher than customary strains on the bone and so you get bone formation.
98
Increased activity means there are higher than customary strains on the bone and so you get bone formation.
Decreased activity means there are lower than customary strains on the bone and so you get bone loss.
99
What is the role of UV light in vitamin D metabolism?
It converts 7-dehydrocholesterol into cholecalciferol.
100
What converts 7-dehydrocholesterol into cholecalciferol?
UV light.
101
What is osteomalacia?
an inability to mineralise bone
102
What is the usual cause of osteomalacia?
Vitamin D deficiency.
103
What is the DEXA T score range for osteopenia?
-1.5 -> -2.5.
104
What is the DEXA T score range for osteoporosis?
-2.5 or lower
105
Name 4 risk factors FRAX uses in determining the 10-year probability of osteoporotic fracture.
1. Family history of parental hip fracture.
2. Smoking status.
3. Use of glucocorticosteroids.
4. Diagnosis of rheumatoid arthritis.
106
In osteoporosis what would the blood tests of bone profile look like?
Everything would be normal! Normal calcium, phosphate, PTH, alkaline phosphate etc. Osteoporosis is a problem with bone density not mineralisation.
107
What compound is a marker of increased bone turnover?
Alkaline phosphatase.
108
What type of muscle fibres are slow twitch?
type 1
109
By what process do type 1 muscle fibres get energy?
Oxidative processes and so have lots of mitochondria.
110
What type of muscle fibres very sensitive to fatigue?
type 2b
111
What type of muscle fibres would be found in postural muscles?
type 1
112
By what process do type 2a muscle fibres get energy?
Oxidative and glycolytic energy processes.
113
By what process do type 2b muscle fibres get energy?
glycolytic energy processes.
114
What type of muscle fibres are fast twitch?
Type 2a and 2b.
115
When muscle fibres are stained to demonstrate the presence of fibrillar ATPase, which muscle fibres appear darker stained?
Type 1 muscle fibres, they have lots of fibrillar ATPase for oxidative energy processes and lots of mitochondria.
