Lecture 13 & 14 - Bone & Bone Marrow Flashcards
1
Q
What are some bone functions?
A
- Protect important/delicate tissues
- Hemopoiesis
- Mineral storage (Ca and Phosphate)
2
Q
Desc. the structure of cancellous (spongy) and compact bone
A
Cancellous:
- Network of fine bony columns (trabeculae)
- Spaces filled w bone marrow
- Osteocytes trapped within lacunae
Compact:
- Form external surfaces
3
Q
What are the types of ossification?
A
- Endochondral ossification: Formation of long bones from cartilage at epiphyseal plates
[appositional (at edges) growth] - Intra-membranous ossification: Formation of bone from mesenchymal stem cells in centre of cancellous bone (trabecular)
[interstitial (middle) growth]
4
Q
Desc. the bone formation in utero
A
- Flat bone develops directly from mesenchymal tissue by intra-membranous ossification
[Skull, jaw, scapula] - Long bones require cartilage template develop by endochondral ossification
[femur, humerus]
5
Q
Desc. intramembranous ossification in parietal (irregular bone of the skull) bone
A
- Mineral deposits within trabeculae radiate outwards from a central point
6
Q
State function of
- Osteoblasts
- Osteocyte
- Periosteum
- Osteo clasts
A
- Osteoblasts: Synthesise bone, lay down osteoid
- Osteocyte: Osteoblasts trapped in extracellular matrix. Canaliculi supply nutrients
- Periosteum: Attached to bone by collagen fibres known as Sharpey’s fibres. Outer layer contain fibroblasts, inner layer is MSC (diff. to form osteoblasts)
[form most outer layer of bone] - Osteoclasts: Resorption of bone –> initiate bone remodelling
7
Q
How to identify osteoclasts?
A
- Function is bone resorption
- Lie in a depression and has multiple nuclei
8
Q
How does cancellous bone turn into cortical (dense) bone?
*X in ILO
A
- MSC converts into osteoblasts
- Lays down osteoid that is mineralised
- Osteoblasts gets trapped- osteocyte
- Form lamellae
- Central MSC turn into blood vessels, lymph vessels and nerves
9
Q
What is the function of Volkmann’s canals?
A
- Connect osteon to osteon
10
Q
Diff. btw immature and mature bone is?
A
- Immature bone osteocytes is in random arrangement, mature is arranged in lamellae of osteons
11
Q
What are the starting points for bone remodelling?
A
Resorption canal (centre)
12
Q
Diff of mature bone structure in compact and cancellous bone
A
- Compact: Haversian canal (blood vessel, lymph vessel and nerves), Volkmann’s canal (osteon to osteon)
[found in medullary /diaphysis region] - Spongy: No Harversian/Volkmann’s canals, osteoclasts at edge
[found in epiphysis, edge]
13
Q
Where does bone strength come from?
A
- Great tensile strength from cortical bone
lamellae are able to slip to resist fracture
14
Q
What are the steps in bone remodelling (yellow slide) and what triggers it?
A
- Steps:
1. Osteoclasts make wide tunnel (cutting cone)
2. Osteoblasts make small tunnel (closing cone) - Exercise stimulates bone remodelling
15
Q
What is osteoid?
A
- Laid down by osteoblasts
- Unmineralized bone (90% collagen, 10% ground substance)
NOT BONE!!
16
Q
What are the factors that affect bone stability?
A
- Activity of osteocytes:
- Can act like osteoblasts and lay down osteoid in lacunae
- Can act like osteoclasts and degrade bone (osteocytic osteolysis), ⬆️by PTH - Activity of osteoblasts (main):
- Stimulated by calcitonin (via IGF-1), oestrogen, testosterone, thyroid hormone, vit A - Activity of osteoclasts (main):
- ⬆️by PTH, release Ca2+ into bone
- Calcitonin inhibit PTH at PTH receptor - Nutrition:
- Vit D3 produces calcitriol (calcium absorption)
- Vit C: synthesis of collagen
- Vit K and B12: synthesis of bone proteins
17
Q
What is osteogenesis imperfecta? Symptoms? Who does it usually affect?
A
- Mutation in COL1A gene, autosomal dominant
- Abnormal collagen 1 formed
- Symptoms: short stature, weak bones (⬆️fracture), blue sclera
- Mainly affects neonates and children
18
Q
What is rickets? Caused by what? Symptoms?
A
- Mainly affects children
- Vit D deficiency –> poor Ca mobilisation and ineffective mineralisation of collagen 1
- Leads to weakened bone dev., short stature, waddling gait
19
Q
What is osteomalacia? Caused by what? Symptoms?
A
- Rickets in adults
- Vit D deficiency –> lower mineralisation and increase osteoids
- Increased calcium resorption
- Occurs in Vit D & Ca deficiency, women cover up skin, pregnant women, phenytoin (drugs) prevent vit D absorption
20
Q
What are the types of osteoporosis? Caused by what?
A
Primary:
Type 1
- Postmenopausal women (⬇️oestrogen –> ⬇️stimulation of osteoblasts to lay down osteoid, osteoclasts activity greater)
- Due to ⬆️osteoclasts
Type 2
- Older men and women
- Loss of osteoblast func (senile osteo.)
- Loss of oestrogen & androgen
- Incomplete filling of osteoclast resorption
Secondary:
- Due to drug therapy (corticosteroids)
- Due to malnutrition, prolonged immobilisation (affect bone remodelling)
- Due to metabolic bone disease (hyperparathyroidism)
21
Q
Risk factors of osteoporosis are
A
- Insufficient Ca intake (recommended 700mg/day)
- Reduce exercise: maintain bone mass
- Smoking
22
Q
What is achondroplasia? Results in what
A
- Autosomal dominant inheritance in FGF3 (fibroblast growth factor) receptor gene
- FGF promotes collagen formation from cartilage (endochondral ossification affected)
- Results in short stature (normal size head & torso), long bones X lengthen properly
23
Q
Structure, example and function of long bones
A
- Longer than wide
- Eg: Femur, humerus, radius, tibia, metacarpal (hand), metatarsal (feet), phalanges (fingers n toes)
- Located mostly appendicular skeleton
- Func: Support weight of body & facilitate movement
24
Q
Structure, example and function of short bones
A
- Length = width
- Eg: Carpals & tarsals (wrist and ankle joints)
- Provide stability & movement
25
Structure, example and function of flat bones
- Flattened
- Eg: Skull (cranial bones), thoracic cage (sternum and ribs), pelvis, scapula
- Protect internal organs, large area of attachment for muscles
26
Structure, example and function of irregular bones
- Vary in shape and structure
- E.g vertebrae and sacrum (pelvis)
- Protect internal organs, vertebrae protect spinal cord, provide anchor points for muscle
27
Structure, example and function of sesamoid bones
- Embedded in tendon
- E.g patella (develop after birth, when start walking)
- Protect tendon from stress and dmg (wear and tear)
28
Desc 2 types of marrow in spongy bone
Red marrow:
- Rich blood supply
- Hemopoiesis
Yellow marrow:
- Adipocytes (shock absorber, insulation, energy reserve, can convert to red marrow)
- Poor blood supply
29
How do maturing cells leave the bone?
- Through sinusoids: endothelial cell fenestrations
| - Platelets: megakaryocytes released fragments of cells through apocrine secretion directly into blood
30
How is the flow in capillaries controlled? What function?
- Controlled by precapillary sphincters
| - Controls fluid exchange btw capillaries and body tissues, large cells X pass thru
31
Define vein. Desc 3 layers and features
- Vein: Transport blood from body tissue to heart
- Tunica intima (endothelium), media (smooth muscle & elastic fibre), externa (elastic fibrous capsule)
- Has fibroelastic cartilaginous valves
- Pump blood under low pressure and against gravity
32
Desc vein type
1. Pulmonary
2. Systemic
3. Superficial
4. Deep
1. Oxygenated blood from lungs to left atrium
2. De-oxy from body to right atrium
3. Close to surface of skin
4. Deep btw tissue
*venules smallest vein, inferior vena cava biggest
33
Define artery. Desc 3 layers and features
- Blood away from heart
- Tunica intima (elastic membrane, non-fenestrated endothelium), media (thick smooth muscle, elastic fibres), adventitia/externa (collagen and elastic fibres: allow artery to stretch but prevents overexpansion)
- Small lumen
34
What are collateral blood vessels?
| *sometimes referred to as communicating blood vessels
- Arteries formed when there is blockage to provide alternative path for arterial blood
- Generated due to ischaemia (reduced blood flow)
35
What is structure and function of pericyte?
| not in ILO
Structure:
- Immature 'smooth-muscle like' cell
- Key component of capillaries
- Contractile properties
- Blood-brain barrier
Function:
- Differentiate into endothelial cell
- Mantain tight capillaries
36
How long does it take for RBC to mature upon entering general blood circulation?
1-2 days
37
Where would osteoprogenitor cells usually be found?
In periosteum--> diff into osteoblasts at external surface
38
What component of bone impedes distribution of nutrients to osteocytes?
- Extracellular matrix
| - Canaliculi supply
39
Desc hypertension effect on each layer of artery/vein
- Intima: artherosclerotic plaque formation, reduce lumen size
- Media: hypertrophy of smooth muscle cell (become larger)
- Externa: dmg extracellular matrix --> become larger/allow artery to stretch prevent over
