histology and pathology of bone and other connective tissue Flashcards
(127 cards)
0
Q
what does the ECM of hyaline cartilage consist of
A
- collagen type 2
- aggrecans
- hyaluronic acid
- chondronectin
1
Q
what are the types of connective tissue
A
connective tissue proper
cartilage
bone
2
Q
what is chondronectin
A
a glycoprotein that binds together the collagen, aggrecans, and integrins together
3
Q
what are the 2 main aggrecans of hyaline cartilage
A
chondroitin sulphate
heparin sulphate
4
Q
where is hyaline cartilage found
A
ribs, trachea, joints
5
Q
what is elastic cartilage
A
modified hyaline cartilage
hyaline cartilage with elastin fibres
6
Q
where is elastic cartilage found
A
ears, ear canal, epiglottis and larynx
7
Q
what is the added benefit of elastic cartilage over hyaline cartilage
A
flexible, but maintains shape
8
Q
where is fibrocartilage found
A
- binds solid joints
- intervertebral discs
- minisci
9
Q
what is fibrocartilage
A
mixture of dense fibrous CT made of type 1 collagen, and isolate islands of cartilage
10
Q
describe the structure of intervertebral discs as you age
A
initially: fibrocartilage around the periphery (type 1 collagen), surrounding gelatinous nucleus pulposis (type 2 collagen)
as you age: the nucleus pulposis becomes replaced with fibrocartilage until you have a solid disc of fibrocartilage
11
Q
explain the different parts of a long bone
A
diaphysis = shaft
metaphysis
epiphysis
12
Q
where is compact bone found
A
forms the outside of bone
13
Q
where is trabecular bone found
A
in the centre of long bones
14
Q
what fills the gaps in the trabecular bone
A
yellow/red marrow and blood vessels
15
Q
what are special about the blood vessels in the bone
A
they include sinusoids - Large diameter and can have pores
16
Q
explain the inner and outer layers of periosteum
A
outer fibrous (fibroblasts, blood vessels and collagen) inner layer cellular (osteoprogenitor cells)
17
Q
is the periosteum or endosteum thicker
A
periosteum
18
Q
what are sharpey’s fibres
A
collagen fibres of a tendon that penetrate into the bone for connection, –> the collagen of the tendon and bone become continuous
19
Q
what are the branches of blood vessels that supply the long bones
A
epiphyseal artery
metaphyseal artery
nutrient artery (to supply diaphyses)
periosteal arteries
20
Q
in what two places is there no periosteum on the bones
A
- articular surface
- where tendon inserts into bone
21
Q
explain the type of cell of the synovial membrane
A
- very leaky cells (lack BM, tight junctions, desmosomes) - NOT epithelium
22
Q
explain the intima of the synovial membrane
A
2-3 layers thick - mix of fibroblast-like cells and macrophage-like cells
23
Q
explain the sub-intimal layer of the synovial membrane
A
fibrous CT
24
what is synovial fluid
an ultrafiltrate of synovial blood plus proteoglycan
25
explain the histological structure of dense bone
organised into Haversion systems (organised along the lines of stress)
- centre has the blood vessels
26
where are osteoprogenitor cells found
in periosteum and endosteum
27
function of osteoprogenitor cells
can give rise to new osteoblasts to grow or repair bone
28
what is the origin of osteoprogenitor cells
from mesenchymal stem cells in bone marrow
29
function of osteoblasts
makes osteoid
30
what is osteoid
the organic ECM of bone (collagen type 1 and bone matrix proteins)
31
function of osteocyte
- maintain bone in its vicinity in response to loading
| - mechanotransduction (can tell where the stresses are)
32
loss of osteocytes leads to
bone resorption and release of free calcium
33
function of osteoclasts
destroys/remodels bone in growth, repair and normal turnover
34
explain the "look" of osteoclasts
giant multinuclear cells
35
explain the steps in how osteoclasts destroy bone
1. seals itself to bone
2. secretes H+, Cl- from H2CO3 breakdown to dissolve CaP
3. secretes proteases to destroy to collagen
36
what molecule is a marker of osteoclast activity
tartrate-resistant acid phosphatase
37
origin of osteoclasts
related to granulocytes/macrophages
| not related to osteoblasts
38
which hormones affect osteoclast activity
parathyroid hormone - increases activity
calcitonin - decreases activity
(opposite for osteoblasts)
39
what happens to osteoclasts when not required
they apoptose
40
during the development of bone.. what two types of bone can be made
membrane bone
| endochondral bone
41
how does membrane bone form
forms directly from mesenchyme
42
where does membrane bone form
the skull and flat bones of the face, the mandible and clavicles
43
which bones form by endochondral ossification
weight bearing bones and bones of the extremities
44
what is the endochondral ossification method of making bone
a cartilage model of the bone is produced and then the cartilage is replaced by bone
45
what are the 5 steps in endochondral ossification
1. bone collar forms around the diaphysis
2. the cartilage beneath the collar degenerates
3. BVs invade, and bring in bone cell progenitors
4. a second nucleus of ossification appears in each epiphysis
5. zones of ossification grow together, but leave a thin zone of cartilage, the growth plate
46
what are the 5 zones of the growth plate in bones
```
resting zone
proliferation zone
maturation zone
hypertrophic zone
ossification zone
```
47
what is the resting zone of the growth plate in bones
zone of normal hyaline cartilage
48
what is the proliferation zone of the growth plate in bones
zone of dividing chondrocytes
49
what is the maturation zone of the growth plate in bones
a zone of mature chondrocytes
50
what is the hypertrophic zone of the growth plate in bones
a zone of hypertrophic (dying chondrocytes)
51
what is the ossification zone of the growth plate in bones
zone of bone laid down
52
when is woven bone made
during development or repair
53
what is different about woven bone
it is more cellular, has more collagen and has no Haversian systems
54
how is woven bone made into lamellar bone
remodelled by osteoclasts and osteoblasts
55
explain the layering of the bone in Haversian canals
the collagen alternate in different directions in each layer and is laid down from outside inside, leaving only a small narrow space around the blood vessel (Haversian canal)
56
where do osteocytes live
in lacunae within the Haversian systems
57
how do osteocytes receive/gain nutrients
via their canaliculae
58
explain the "look" of osteoblasts
amphophilic cytoplasm
perinuclear hoff
(either resting - thin, or active - fat)
59
are osteoblasts or osteoclasts faster
osteoclasts
60
how does PTH cause an increased activity of osteoclasts
PTH causes an increase in the expression of RANKL and a decrease in the expression of osteoprotegrin on the osteoclast progenitor--> differentiation to osteoclast
61
where does the RANKL ligand come from
ligand on osteoblast
| receptor on osteoclast
62
what is the action of osteoprotgrin
blocks the RANK receptor
63
what are the steps in normal osteoid mineralisation
1. osteoblasts secrete collage and secretory vesicles
| 2. increase in conc of Ca and PO locally causes precipitation around the vesicles
64
what do the vesicles contain which the osteoblasts secrete
alkaline phosphatase and pyrophosphatase
65
what are the two types of "incomplete" fractures
greenstick - break only part way through
| torus - compression fracture
66
what is the normal annual bone turnover in adults?
5-10%
67
what is a comminuted fracture
a fracture where there are more than 2 fragments
68
what is a butterfly fracture
where the fracture is triangular shaped (3 fragments)
69
what causes a stress fracture
repeated low force injury to a normal bone
70
what causes a pathological fracture
a normal amount of force on an abnormal bone
71
what are the 3 stages of healing bone
inflammatory phase
reparative phase
remodelling phase
72
what occurs in the inflammatory phase of bone healing
- haematoma formation and granulation tissue (fibrin creates framework, platelets and leukocytes release inflammatory cytokines and bone cells activated to start repair)
- granulation tissue formation
73
what is the time frame for the inflammatory phase of bone healing
first few days
74
what are the two subphases of the reparative phase of bone healing
soft callus formation
| hard callus formation
75
at what time frame is the soft callus formation of bone healing
days-weeks
76
what occurs during the soft callus formation of bone healing
- cartilage formation to hold the fractured ends together
| - periosteum repairs itself over the outside due to osteoporgenitor cells
77
at what time frame is the hard callus formation of bone healing
weeks-months
78
what occurs during the hard callus formation of bone healing
osteoid formation and ossification (firstly woven bone or endochondral ossification)
79
at what time frame is the remodelling phase of bone healing
months-years
80
what occurs during the remodelling phase of bone healing
bone remodelling of woven bone to lamellar bone along the lines of stress
81
which type of fracture may not need a soft callus to form in the healing process of bone
if the ends are closely apposed
82
what is the advantage and disadvantage of not having to form a soft callus during bone fracture healing
healing will be faster
| but not as strong
83
what is the goal of fracture management
union of the broken bone to allow healing as fast as possible and without complications
84
how is 'union' of fractures performed
- reduction - minimize the gap
- fixation - minimize the strain or movement (cast)
- minimize any other factors that slow healing
85
what are the factors that slow fracture healing
- advanced age
- multiple medical comorbidities
- NSAIDs, corticosteroids
- smoking
- poor nutrition
- open fracture with poor blood supply
- multiple traumatic injuries
- local infetion
86
what are the complications of bone fracture
- non-union
- delayed union
- mal-union
- infection
- osteonecrosis/AVN
87
most upper limb fractures in adults repair completely in ...
6-8 weeks
88
most lower limb fractures in adults repair completely in...
12-16 weeks
89
what is mal-union
healing of a bone in anunacceptable position
90
what are the potential problems of mal-union
- disability
- post-traumatic osteoarthritis
- cosmetic
91
what is the most common cause of osteomyelitis
staph aureus
92
what are the common sites of osteonecrosis after fracture
neck of femur (blood supply is via neck)
| scaphoid (blood supply is via distal end)
93
why can osteonecrosis occur after bone fracture
because fractures can interrupt the blood supply and leave part of the bone ischaemic
94
what is osteoporosis
reduced mass of otherwise normal bone
95
how can menopause lead to osteoporosis
decreased serum oestrogen and increased IL-1, IL-6 and TNF levels leads to increased expression of RANK and RANKL --> increased osteoclast activity
96
how can aging lead to osteoporosis
- decreased replicative activity of osteoprogenitor cells
- decreased synthetic activity of osteoblasts
- decreased biological activity of matrix-bound growth factors
- reduced physical activity
97
what causes Paget's disease
large, overactive osteoclasts and osteoblasts that produce more bone
98
what is the result of Paget's disease
- thick soft cortex
- coarse trabeculae
- easily fractured
- can compress nerves
99
what are the 3 stages of Paget's disease
osteolytic - osteoclasts
mixed - osteoclasts and osteoblasts
osteosclerotic - osteoblasts
100
what are the primary and secondary causes of hyperparathyroidism
primary - parathyroid hyperplasia or tumour
| secondary - prolonged hypocalcaemia or hyperphosphataemia
101
what are the effects of hyperparathyroidism
- increased osteoclastic activity (RANK-L) with associated compensatory increase in osteoblastic activity
- -> dissecting osteitis
- -> osteitis fibros cystica
102
what histological features do you see in dissecting osteitis
osteoclasts in trabeculae
103
what do you see in osteitis fibrosa cystica
microfractures and granulation tissue
104
what are the presenting symptoms of bony mets
- pathological fractures
- hypercalcaemia
- bone marrow failure
- bone pain
105
how do the malignant cells influence bone
they produce RANK-L an PTHrP
| they dont influence bone directly
106
which primary tumours can lead to bony metastases
```
breast
lung
thyroid
kidney
prostate
bowel
```
107
what are the disorders of bone metabolism
```
hypocalcaemia
hypercalcaemia
hypophosphataemia
hyperphosphataemia
osteoporosis
```
108
what causes hyperphosphataemia
renal failure
109
what percentage of trabecular bone and cortical bone is remodelled per year
trabecular - 25%
| cortical - 3%
110
which bones in particular are affected by bone remodelling
femoral neck and vertebral bodies (trabecular bone)
111
what things affect bone remodelling
ageing
physical factors (exercise, loaing)
hormones (oestrogen)
drugs
112
what causes the expression of RANKL by osteoblasts
active vitamin D (calcitriol) and PTH
113
what are the components of synovium
- macrophage like cells
- fibroblast like cells
- blood vessels and lymphatics
114
from what is synovial fluid derived
- a transudate of plasma from synovial capillaries
| - hyaluronic acid produced by synovial cells
115
what is in the ECM of hyaline cartilage
- collagen type 2
- hyaluronic acid produced by chondrocytes
- proteoglycans - aggrecan
- glycosaminoglycans such as chondroitin sulphate
- water
116
what is in the Haversian canal
blood vessels, nerves, lymphatics and connective tissue
117
what structures link the lacunae of Haversian systems
canaliculi
118
what are the 2 main types of ossification
endochondral
| intramembranous
119
what causes osteophytes in a joint with OA
calcification of periarticular cartilage and synovium
120
what causes subchondral cysts in a joint with OA
synovial fluid entering bone through microfractures
121
what causes subchondral sclerosis in a joint with OA
thickening of subchondral bone and trabeculae
122
what causes a loss of joint space in a joint with OA
fibrillation and sloughing of articular cartilage
123
what is the precursor protein of the amyloid deposition that occurs in rheumatoid arthritis
serum amyloid associated protein
124
what other diseases are associated with serum amyloid associated protein
TB
IBD
bronchiectasis
chronic osteomyelitis
125
which cytokines are involved in fracture healing and what do they do
TGF-b, PGDF, FGF - activate osteoprogenitor cells in the periosteum and activate OB and OC
126
what does the haematoma provide during fracture healing
- stops the bleeding
| - provides a framework for fibroblasts and inflammatory cells
