Week 1: Functions of the Skeletal System Flashcards
1
Q
How much calcium, on average, is found within the skeletal system?
A
99%
2
Q
Calvaria
A
Top of the skull / upper part of neurocranium.
3
Q
What does the Calvaria cover?
A
The cranial cavity containing the brain.
4
Q
What bones are the Calvaria made of?
i.e. frontal, temporal, occipital, parietal, Ethmoid, Sphenoid
A
Frontal,
Occipital,
Parietal.
5
Q
List two main structural frameworks that protect internal organs.
A
Calvaria for the brain,
Thorax for the lungs and heart.
6
Q
Hemopoiesis
A
Production of blood cells and platelets, which occurs in red bone marrow.
7
Q
Do Juveniles or Adults have more red marrow within their Trabecular bone?
A
Juveniles
8
Q
Do Juveniles or Adults have more yellow marrow within their Trabecular bone?
A
Adults - yellow bone marrow consists of triglycerides.
9
Q
Main 4 functions of the Skeletal System.
A
Structural framework,
Support,
Muscle attachment points to allow for movement of antagonistic pairs.
10
Q
Approximate % water in the extracellular matrix?
A
15%
11
Q
Approximate % collagen fibres in the extracellular matrix?
A
30%
12
Q
What type of material are collagen fibres considered to be in the extracellular matrix? (i.e. organic / inorganic)
A
Organic
13
Q
What cells secrete collagen into the extracellular matrix?
A
Osteoblasts
14
Q
What is the meaning of the suffix -blast in “osteoblast”?
A
Secretion
15
Q
Why is collagen secreted into the extracellular matrix?
A
To prevent against tensile pressures that would normally shatter/break bones.
For flexibility.
16
Q
Approximate % crystallised mineral salts in the extracellular matrix?
A
55%
17
Q
Hydroxyapatite
A
crystallised inorganic mineral salts.
18
Q
Cells in Osseous Tissue of bones? Name the 4 types.
A
Osteogenic Cells,
Osteoblasts,
Osteocytes,
Osteoclasts.
19
Q
What are Osteogenic cells also known as?
A
Osteoprogenitor stem cells.
20
Q
What do Osteogenic cells/Osteoprogenitor stem cells differentiate into?
A
Osteoblasts.
21
Q
Where are Osteogenic cells/Osteoprogenitor stem cells found in bone?
A
Outer surfaces of bone (within the inner cellular layer of the periosteum), and in the medullary cavity (endosteum and lining the Haversion canals).
22
Q
Function of Osteoblasts?
A
Secretes collagen to build the extracellular matrix, which will ossify/calcify to create harder bone.
23
Q
What remains when osteoblasts finish building the extracellular matrix?
A
Osteocytes (mature bone cells)
24
Q
Function of Osteocytes?
A
Osteocyte processes to other osteocyte processes (projections) communication - cell to cell communication - for upkeep of metabolism in bone tissue.
25
Suffix meaning of Osteoclasts?
"-clast" meaning resorption/breakdown.
26
Function of Osteoclasts?
Breakdown of older bone tissue to allow for the creation of new bone tissue.
27
Function of the "ruffled border" of osteoclasts?
| Ruffled border = highly infolded plasma membrane edge.
Secretion of lysosomal enzymes.
| High acid content due to breakdown of bone.
28
Order of presence in bone tissue of: osteoblasts, osteocytes, osteogenic cells/osteoprogenitor stem cells.
1. Osteogenic cells/osteoprogenitor stem cells (same thing): differentiates into osteoblasts).
2. Osteoblasts: forms bone extracellular matrix.
3. Osteocytes: maintains bone tissue (metabolism).
29
How are osteoclasts formed?
coagulation of monocytes.
30
Compact bone AKA? (2 other names)
Cortical bone, Dense bone
31
Cortical bone AKA? (2 other names)
Compact bone, Dense bone
32
Dense bone AKA? (2 other names)
Compact bone, Cortical bone
33
Spongy bone AKA? (2 other names)
Trabecular bone, Cancellous bone
34
Trabecular bone AKA? (2 other names)
Spongy bone, Cancellous bone
35
Cancellous bone AKA? (2 other names)
Spongy bone, Trabecular bone
36
Compact/Dense/Cortical bone: strength.
More solid, bend-resistant
37
Location of Compact/Dense/Cortical bone
Forms external layer of all bones & bulk of diaphysis.
38
Weight of Compact/Dense/Cortical bone
Heavier due to higher density than trabecular bone.
39
Spongy/Trabecular/Cancellous bone: strength.
Strength for compression. Present at joints - predominantly trabecular bone with a cortical bone layer.
40
Location of Spongy/Trabecular/Cancellous bone
```
Forms the majority of short bones (i.e. carpals),
flat bones (i.e. calvaria - skull),
irregular bones (i.e. vertebrate / spinal column),
ends of long bones).
```
41
Structure/Description of Spongy/Trabecular/Cancellous bone.
Contains larger spaces - reduces the overall bone weight, protects yellow and red bone.
42
Abundance of Spongy/Trabecular/Cancellous bone?
More abundant, lighter weight allows movement.
43
Abundance of Compact/Dense/Cortical bone.
Less abundant, heavier.
44
Diaphyses AKA?
Shaft
45
Location of diaphyses?
Main/mid-section of long bone.
46
Diaphyses structure?
Made of cortical bone and contains bone marrow and adipose tissue (fat).
47
Components of Compact/Cortical bone. What is an osteon also referred to as, and what is consisted within it?
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Osteons = Haversian Systems.
Concentric Lamellae (ringed portion),
Central Canal (Haversian canal),
Lacunae (latin: lake),
Canaliculi (extensions of lacunae),
Interstitial Lamellae,
Perforating/Volkmann's canals,
Circumferential lamellae.
```
48
How are Osteons organised?
```
Haversian Systems (AKA Osteons):
Aligned in the same direction along lines of stress to the bone,
Well organised,
Dynamic structural units - formation of new osteons and breakdown of old.
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49
Description of Concentric lamellae (incl. function).
Ringed portion of a cross-section of bone,
circular plates of mineralised/calcified extracellular matrix,
they fit within one another to make an osteon.
50
Structural and Function of central canal (Haversian canal)
Passageway for neurovasculature & lymphatics,
| Contains blood vessels, nerves and lymph channels.
51
Structure and Function of Lacunae (latin: lake)
Small spaces between concentric lamellae,
| Osteocytes sit within lacunae.
52
Structure and Function of Canaliculi (extensions of lacunae)
Allows for extracellular fluid and osteocyte processes to sit within them.
53
Interstitial Lamellae
Fragments of old osteons sit here, as they are broken down and removed.
54
Perforating/Volkmann's canals
Canals penetrate periosteum and compact bone to allow neurovasculature to enter bone.
55
Circumferential Lamellae
Found on the inner and outer edges (circumference) of bone,
The periosteum, outer connective tissue layer, closely adheres to the circumferential lamellae,
Circumferential Lamellae is important for appositional growth (growth of the width of the bone).
56
Part's of Long Bone (labels only): 10 features.
```
Epiphyses,
Diaphyses,
Metaphyses,
Articular Cartilage,
Periosteum,
Osteoblasts,
Osteoclasts,
Sharpey's fibres (AKA Perforating fibres),
Medullary Cavity,
Endosteum.
```
57
What are Epiphyses?
ends of long bone
58
What is the Diaphysis?
middle section (long) of long bone
59
Where are Metaphyses located?
Between an epiphysis and diaphysis section.
60
What does the Metaphysis consist of in a juvenile/growing individual?
A block of Hyaline cartilage.
61
In a juvenile/growing individual, what is the block of Hyaline cartilage known as?
an Epiphyseal plate
62
Explain the role of Hyaline cartilage.
In a growing individual/juvenile, the metaphysis of long bone consists of Hyaline cartilage and is instead known by the term "Epiphyseal plate" (as the cartilage grows into part of the diaphysis).
Hyaline cartilage grows and is replaced by bone. The growth increases the length of the diaphysis/shaft of long bone.
63
At what approximate age, in each of males and females, are the epiphyseal plates replaced completely by bone and, thus, stop growing?
18 in females,
| 21 in males.
64
Where is Articular cartilage found?
At the Epiphyses of long bone.
65
What is the function of Articular cartilage?
It resides at the epiphyses of long bones (joints) for shock absorption.
66
What are some features relating to why articular cartilage is located at the epiphyses of long bones and why we experience joint pain?
Cartilage has a very low blood supply.
| A low blood supply = tissues don't heal well, thus joint pain as bone slides along bone.
67
Location of the Periosteum
It is connective tissue surrounding the outer layers of bone, except where articular cartilage is.
68
Structure of the periosteum.
Two layers:
1. Tough, fibrous outer layer - for protection.
2. Inner osteogenic layer.
69
Osteoblasts and osteoclasts are found where?
They sit between the bone and periosteum layers.
70
Structure and Function of Sharpey's fibres (or perforating fibres).
Enters the bony matrix to allow close adherence between compact bone and the periosteum.
71
Location of the Medullary Cavity.
Within the bony cavity (within the region that the periosteum surrounds).
72
Features of the Medullary cavity.
Dry, non-living bone: hollow medullary cavity (no vasculature),
Bones of living individuals: triglyceride storage, filled with yellow marrow (in adults and red marrow in juveniles) and abundant vasculature.
73
Location comparison of Endosteum vs Periosteum.
Lines the inner edges of the medullary cavity (inside the MC), whilst Periosteum lines the outer surface of bones (except where articular cartilage is found) - outside the MC.
74
Define "Ossification".
Bone development.
75
Describe features of embryonic development.
Approx. week 6: Mesenchymal 'skeleton' forms.
Mesenchymal skeleton breaks up into 2 ossification types - Intramembranous ossification (replaces mesenchymal skeleton with bone) & endochondral ossification (mesenchymal skeleton develops into a cartilage model which is then replaced by bone).
Root "-chondr-" indicates cartilage.
76
What is the 'Mesenchymal' phase of embryonic development?
Embryonic connective tissue breaks up into different body features.
77
In which areas does intramembranous ossification occur? (4 points).
Fontanels (flat bones of skulls),
Most facial bones,
Mandible,
Medial portion of clavicle.
78
Intramembranous Ossification process (4 points).
1. Development of Ossification Centre.
2. Calcification.
3. Development of trabeculae (spongy bone).
4. Development of periosteum.
79
Intramembranous Ossification process: stage 1.
Development of Ossification Centre:
Mesenchymal stem cells cluster to form Osteogenic cells, which then form osteoblasts, etc.
Requires a blood supply.
80
Intramembranous Ossification process: stage 2.
Calcification:
| Osteoblasts from the ossification centre secrete extracellular matrix, trapping osteocytes within the bone.
81
Intramembranous Ossification process: stage 3.
Development of trabeculae:
| Red bone marrow filling the medullary cavity and producing red blood cells.
82
Intramembranous Ossification process: stage 4.
Layer of osteoblasts still present between bone and periosteum.
83
Which bones undergo endochondrial ossification?
| Is endochondrial ossification more or less complex than intramembranous ossification?
Most bones form this way.
| More complex than intramembranous ossification.
84
Name the 6 steps of the endochondrial ossification process.
1. Development of the cartilage model.
2. Growth of the cartilage model.
3. Development of Primary Ossification Centre.
4. Development of the Medullary Cavity.
5. Development of a Secondary Ossification Centre.
6. Formation of Articular Cartilage and Epiphyseal Plate.
85
Endochondrial Ossification process: stage 1.
Development of the Cartilage Model:
Cartilage model develops and replaces mesenchymal model.
Chondroblasts and perichondrium develop.
Bony collar forms during intramembranous ossification and is used as a structural support for the cartilage model - bones present on the sides of the cartilage model maintain it's structural integrity and allow growth (of the cartilage model).
86
Endochondrial Ossification process: stage 2.
Growth of the Cartilage Model:
Blood vessels move to the bone collar (where spongy bone is forming) to maintain good blood supply for further development/differentiation and growth - forms the "primary ossification centre" (typically in the middle of the cartilage model).
87
Endochondrial Ossification process: stage 3.
Development of the Primary Ossification Centre:
As bone replacement occurs (where temporary structures are replaced with more permanent bone fixtures), associated vasculature moves to such regions through the nutrient foramina.
AKA bone replaces the cartilage model.
88
Endochondrial Ossification process: stage 4.
Development of the Medullary Cavity:
Osteoblasts secrete osseous tissue.
Osteoclasts break down the cartilage model and any other bone previously formed with the primary ossification centre.
89
Endochondrial Ossification process: stage 5.
Development of the Secondary Ossification Centre:
Occurs at approx. birth.
Vasculature moves towards the bone's extremities (epiphyseal vasculature) - found in the proximal and distal ends of bones, generally no ossification of bone in the extremities of bones until after birth.
90
Endochondrial Ossification process: stage 6.
Formation of the articular cartilage & epiphyseal plate.
91
Define calcification.
Hardening of bone.
Used to indicate pathological bone hardening.
Often used interchangeably with ossification as calcification is a section of the ossification process.
92
Chondroblasts vs. Osteoblasts.
"-blast" means "secrete"
Osteoblasts:
Present in diaphysis & during intramembranous ossification process of bones.
Secretes extracellular matrix.
Chondroblasts:
"Chondro-" meaning "cartilage".
Present during endochondrial ossification process.
Secretes cartilage for the cartilage matrix, especially at the epiphyses regions.
93
Describe length & width growth during Ossification of bones.
Length: interstitial growth.
Width: appositional growth.
94
Explain Nutrient Foramina.
Small holes typically amongst the middle of the shaft/trabeculae.
Indicative of where the primary ossification centre lied previously during the endochondrial ossification.
95
2 features of bone associated with ageing.
Loss of bone mass (more than the increased brittleness) - by demineralisation.
Brittleness due to the slowing of collagen production - osteoblasts secrete extracellular matrix at a lesser rate.
96
Explain how an individual can slow down the effect of ageing on the skeletal system. (1 point)
Weight-bearing exercises:
Pull on muscle results in pull on bone which increases osteoblast activity.
Bone can alter strength with increased/decreased mechanical stress.
Increased deposition of mineral salts and collagen allows mineral salts to calcify and add structural integrity to bone.
97
Explain Osteoporosis.
Osteoclast activity remains the same.
Osteoblast activity slows:
The rate of secretion of extracellular matrix and ossification is less than the rate of osteoclast activity whereby the bone is broken down (causing it to become porous).
98
Symptoms of Osteoporosis (2 points).
Higher incidence of fractures - stress fractures are most common but then leads to worse fracture types (thus, pain).
Shrinkage of vertebrae - height loss, kyphosis (hunched back).
- kyphosis as a result of multiple stress fractures in the body of the vertebrae. The vertebrae is almost exclusively trabeculae bone and when stress fractures come, it leads to the collapse of the vertebrae body.
99
In which individuals is osteoporosis most common?
Middle-aged and elderly individuals.
Higher incidence in women: due to smaller body build and oestrogen production slowing but for men testosterone doesn't.
Other risk factors - family Hx, ancestry (European & Asian), small body builds, inactive lifestyle.
100
Name 5 minerals that have an effect on bone growth and remodelling, in order of greatest to least effect.
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Calcium,
Phosphorus,
Magnesium,
Manganese,
Fluoride.
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101
Effect on bone growth & remodelling: Vitamin C. (2 points)
Synthesis of collagen.
| Allows for bone flexibility.
102
Effect on bone growth & remodelling: Vitamin D.
The vitamin D precursor, already present in the skin, affects the kidneys:
The last by-product to the active form of Vitamin D, Calcitriol, will be formed by the kidneys and plays a role in the release of Calcium.
103
Effect on bone growth & remodelling: Calcitonin. (4 points)
Released by thyroid gland.
Increases osteoblast (bone secretion) activity.
Decreases Calcium uptake in intestines.
Decreases Calcium reabsorption in kidneys.
104
Effect on bone growth & remodelling: Parathyroid Hormone (PTH). (4 points)
Released by parathyroid gland.
Increases Osteoclast activity.
Decreases Calcium uptake in intestines.
Increases Calcium reabsorption in kidneys.
105
Effect on bone growth & remodelling: Oestrogen & Testosterone. (1 point)
Estrogen production slows earlier in women, whereas testosterone does not in men.
106
Effect on bone growth & remodelling: Human Growth Hormone (hGH). (2 points)
Secreted by the Pituitary Gland.
| Plays a role in bone development: Overproduction causes gigantism, underproduction causes dwarfism.
107
What role do Osteoblasts play in bone growth & remodelling functions? (1 point)
Fracture repair.
108
What role do Osteoclasts play in bone growth & remodelling functions? (1 point)
Reabsorbs portions of bone that need to be replaced.
109
Name the 4 types of fractures.
Complete,
Comminuted,
Impacted,
Greenstick.
110
Which of the 4 fracture types is the most extreme.
Comminuted fractures.
111
Why are Comminuted fractures the most extreme/severe type? (2 points)
Dispersed bone fragments.
Healing of comminuted fractures does not return the bones structural integrity, resulting in large bony calluses at the healed spot.
112
Which fracture type is the second most severe?
Complete fractures.
113
Where, in bones, do Complete fractures usually occur?
Can be seen anywhere but:
| Typically in Shafts of long bones and Anatomical Necks of long bones.
114
What are the two types of complete fractures?
Open complete fractures,
| Closed complete fractures.
115
Describe Open Complete fractures. (3 points)
More severe than closed complete fractures,
One fragment of bone extends outside of the skin,
Longer recovery time than with closed fractures.
116
Describe Closed Complete fractures. (2 points)
The two fragments of bone stay under the skin (no open wounds),
Shorter recovery time than open complete fractures.
117
Describe Impacted fractures. (4 points)
Typically occur in accidents with extreme force (i.e. car accident).
One fragment of bone is pushed with high velocity into the second fragment of bone.
This fracture heals easier as the two fragments of bone are touching, as opposed to complete fractures for example.
Immediate immobilisation is required to prevent impacted fractures becoming comminuted fractures.
118
Describe Greenstick fractures. (2 points)
Almost a complete fracture (complete on one side), with the other side as a bended bone.
Collagen causes portions of the bone to bend instead of breaking.
119
Which age range do Greenstick fractures typically present in? Juveniles or adults? Why? (2 points)
Juveniles.
Occurs in individuals where bone development is still occurring (juveniles) due to the characteristic break on one side and bend of bone on the other.
120
What is the etymology/reason for the name "Greenstick" of Greenstick fractures? (2 point)
"Greenstick" comes from the similarities of trying to break a "green"/fresh branch or stick.
Also termed a "partial fracture".
121
What are the most frequent fracture locations? Name of fracture in location?
Distal radius: distal forearm or carpal bones which articulate with radius - Colles' fracture.
Ankle or distal ends of lower limb bones (involving fibula) - Pott's fracture.
122
Describe Colles' fracture. (3 points)
Always involves fracture to distal end of radius - distal forearm or carpal bones which articulate with radius or both).
Can happen at any age, but more prevalent in osteoporotic individuals.
Usually from fall injuries (hands first to protect oneself).
123
Describe Pott's fracture. (2 points)
Fractures to fibula (always) and/or ankle & distal ends of lower limb bones (aka lateral malleolus).
More severe Pott's fractures: extreme torsion of ankle region, including avulsion or complete break off distal end of tibia/"medial malleolus".
124
Healing of fractures. Reference to dynamic ness & vascularisation. (2 points)
Highly dynamic.
| Highly vascularised.
125
Healing of fractures: break of bone. (3 points)
Break of bone causes break of blood vessels.
Blood will rush and fill area of fracture.
Blood won't move beyond the periosteum, so it remains in the fractured region - causing the characteristic "Hematoma" resulting in swelling, discolouration and inflammation.
126
Healing of fractures: role of Osteoblasts. (2 points)
Osteoblasts start secreting extracellular matrix.
| In order to maintain bone integrity, you don't want to speed osteoblast process up.
127
Healing of fractures: intermediate portion "Fibrocartilaginous Callus". (3 points)
Instead of a complete bone replacement, this Fibrocartilaginous Callus intermediate is formed.
Building up of cartilage in the fracture region keeps the two portions of bone closely associated with each other: This allows the osteoblasts to secrete fully formed extracellular matrix and for osteoclasts to break down portions of bone that don't need to be there anymore.
Fibrocartilaginous Callus can form within hours or up to weeks depending on the severity of the fracture.
128
Healing of fractures: Bone will eventually replace cartilage in the Fibrocartilaginous Callus region. (2 points)
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Osteoblasts accreting (accumulating) while osteoclasts break down bone fragments.
Remodelling can continue for years depending on severity of the fracture.
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