Connective tissue Flashcards
1
Q
Connective tissue proper
A
loose and dense connective tissue
2
Q
specialized connective tissue
A
cartilage, bone, and blood
3
Q
mesenchymal stem cells
A
precursor than can differentiate into all types of connective tissue
4
Q
Functions of connective tissue
A
3D framework supporting epithelium and other tissues and soft organs, heat regulation, storage, preserve organ structure, protection
5
Q
characteristics of connective tissue
A
sparse cells and extracellular matrix (ECM)
6
Q
extracellular matrix (ECM)
A
bulk of connective tissue, fibers, ground substance, secreted by connective tissue cells, gives the connective tissue its characteristics
7
Q
ground substance
A
matrix between fibers, made of glycosaminoglycans, proteoglycans, and water
8
Q
fibers in ECM
A
combination of collagen and elastin
9
Q
Collagen
A
high tensile strength (especially type I), secreted as procollagen and assembled extracellularly
10
Q
5 most common types of collagen
A
- Skin, vessels, tendon, organ capsule, bone (most common)
- Cartilage
- Reticular Fibers (organs)
- Basement membrane
- hair and placenta
11
Q
which collagen types compose 80-90% of body?
A
Types I, II, and III
12
Q
Type III collagen
A
thinner than other types, stained using silver, provide supporting framework to soft organs
13
Q
Elastin
A
stretch and recoil, proelasted secreted by fibroblasts, assembled extracellularly, need special stain to view
14
Q
Glycosaminoglycans
A
chains of sugars with repeating disaccharide unit
Hyaluronic acid and chondroitin sulfate: cartilage
Dermatan sulfate: skin
Keratan sulfate: bone, cornea
Heparan sulfate: basement membrane
15
Q
proteoglycans
A
GAGs linked to a protein core, can be linked together by a core molecule
16
Q
(resident) cells of connective tissue proper
A
fibroblasts/ fibrocytes, adipocytes, mast cells, macrophages
17
Q
What are the transient cells of connective tissue proper and when is it more common?
A
Lymphocytes/ plasma cells, leukocytes (white blood cells), more common during infection
18
Q
fibroblasts
A
building cells of connective tissue, produce ECM found in proper connective tissue
19
Q
fibrocytes
A
fibers including procollagen and proelastin, less active than fibroblasts but can be further stimulated
20
Q
unilocular adipocytes
A
white fat, one large lipid droplet inside cell, nucleus not always present
21
Q
multilocular adipocytes
A
brown fat, common in young animals and hibernating animals, multiple vacuoles of lipid droplets, color due to mitochondria, metabolically active
22
Q
mast cells
A
ovoid shape, can be quite large, basophilic granules, chemical mediators (histamine)
23
Q
macrophages
A
professional phagocytes, derived from monocytes, , become very large and multinucleated when activated
24
Q
loose connective tissue
A
areolar (air) connective tissue, more common than dense, ground substance is more abundant
25
dense connective tissue
fibers (mostly type I collagen) are more abundant than ground substance, strong, includes dense regular and dense irregular connective tissue
26
dense regular connective tissue
strong in one direction, parallel to orientation of fibers, tendons and ligaments
27
dense irregular connective tissue
strong in many directions, eg. dermis
28
locations of cartilage
fetal skeleton, supporting framework, on articulating surfaces (joints)
29
characteristics of cartilage
strong and pliable connective tissue, no blood vessels or nerves, uses diffusion for nutrients and waste
30
components of cartilage
few cells: chondroblasts and chondrocytes
ECM: 70-80% water
Fibers: 40% dry weight, collagen and sometimes elastin
Ground substance: 60% dry weight, GAGs and proteoglycans
31
chondroblast vs chondrocyte
chondroblast builds cartilage
| chondrocyte maintains ECM
32
Cartilage types
```
hyaline cartilage (most common): articulating surface and trachea
Elastic cartilage: epiglottis and ear canal
Fibrocartilage: intervertebral discs, menisci (in stifle and TMJ)
```
33
cartilage structure
surrounded by perichondrium, chondrocytes in lacunae surrounded by matrix and fibers
34
perichondrium
outer fibrous layer with fibrocytes and collagen and inner cellular layers with rounder "chondroblasts", dense irregular connective tissue, outer layer is structural while inner layer is chondrogenic
35
functions of hyaline cartilage
found in nose, larynx, connects ribs to sternum, tracheal rings and bronchi, articulating surfaces, fetal skeleton and growth plates (helps increase bone length)
36
At what level can chondroblasts and chondrocytes be differentiated?
When cells leave the perichondrium they can be called chondroblasts or chondrocytes
37
Why can't type II collagen be differentiated on the slide?
Type II collagen has the same refractive index as ground substance
38
How do chondroblasts and chondrocytes differ in appearance?
Less ECM around chondroblasts, chondroblasts are slightly rounder
39
Articular cartilage
Hyaline cartilage at movable joints, made of water, collagen, GAGs, and proteoglycans
few cells, lacks a perichondrium so depends on diffusion from synovial fluid, slow remodeling
40
matrix of articular cartilage
type II collagen, hyaluronic acid, proteoglycans, attracts water which is crucial for shock absorption
41
How does the structure of the ECM help absorption of water?
Proteoglycans have have negative charges that repel protein core. Water fills in this space as hydrogen bonds are attracted by negative charge
collagen arrangement pushing against each other helps to contain tissue so it does not expand too much
42
Superficial vs deep articular cartilage
Superficial: more water collagen and cells, arches
deep: less water, collagen, and cell, more proteoglycans help to draw in water
43
Elastic cartilage
similar to hyaline cartilage but with more elastic fibers, type II collagen, lacuna and chondrocytes, visible elastic fibers
44
Fibrocartilage
lacks perichondrium, type I collagen, cells aligned in alternating parallel rows with thick bundles of collagen between,
45
Where is fibrocartilage found?
Where strong tensile forces are present so fibrocartilage resists compression. eg. IVD, menisci, tendon/bone junctions
46
Fibrocartilage vs dense regular connective tissue?
hard to differentiate, fibrocartilage cells are rounder and have lacunae, lined in rows
47
appositional growth of cartilage
addition of cells (chondroblasts) immediately deep to the perichondrium
48
interstitial growth of cartilage
division of chondrocyte in lacuna already surrounded by matrix
49
isogenous group
2-4 daughter cells present after cell division
50
functions of bone
support, protection, hematopoiesis, mineral storage, attachment, lever system
51
bone composition
few cells, very little ground substance, ECM about 10% water, 2/3 inorganic (minerals) and 1/3 organic
52
components of organic material in bone
about 80-90% Type I collagen, GAGs, proteoglycans
53
mineral component of bone
added rigidity
54
osteoprogenitor
gives rise to osteoblasts, derived from mesenchymal stem cells
55
osteoblasts
formation and mineralization of bone matrix
56
osteocytes
mature osteoblasts, maintain bone
57
osteoclasts
breakdown bone matrix and woven bone, differentiated monocytes
58
periosteium
outer covering of bone, outer fibrous layer containing collagen fibers and blood vessels (dense irregular connective tissue)
Inner cellular layer: osteogenic (still not many cells)
59
endosteum
inner lining of bone, single cell layer, simple squamous, marrow, osteoblasts, and osteoclasts
60
Sharpey's fibers
perforating fibers, collagen in periosteium intimately invested in bone collagen
61
compact bone
cortical/ dense bone
62
cancellous bone
spongy/ trabecular bone, more common in epiphysis of long bone
63
epiphysis
enlarged ends of long bones, covered with articular cartilage at joints
compact bone become thinner and spongy bone increases
64
diaphysis
shaft of long bones, hollow containing bone marrow
65
osteon
functional unit of compact bone
| Includes Haversian canal, concentric rings, canaliculi
66
Central canal
Haversian canal, parallel to bone surface, contains blood vessels and nerves
67
lamina of bone
concentric rings of osteocytes in lacunae
68
canaliculi
open into central canal for fluid/waste/nutrient exchange, connect the lamina
Osteocytes project into canaliculi for communication
69
Parathyroid hormone
PTH, causes Ca within fluids surrounding each osteocyte and whithin canaliculi to be pumped into blood
70
Perforating canal
connects central canal, perpendicular to bone surface
71
interstitial lamellae
haphazardly placed between osteons, allowing for a variety of shapes
72
cancellous bone
large open spaces surrounded by thin anastomosing plates of bone, lined by endosteum, organized around stress points, helps decrease weight
73
microscopic structure of spongy bone
no osteons or central canal, lamella organized as trabeculae with osteocytes in lacunae, not as tight within compact bone, canaliculi open at the trabecular surface below the endosteum instead of the central canal and fluid nutrients exchanged
74
why is bone decalcified in slide preparation
to see the osteocytes
75
bone marrow
core of bones, hematopoiesis, part of lymphatic system, 4% of total body weight
76
Red bone marrow
hematopoietically active, present at birth, gradually converted to yellow marrow
77
yellow bone marrow
primarily adipocytes, can revert to red in case of severe blood loss
78
osteogenesis
calcified bone replaces connective tissue
79
intramembranous osteogenesis
ossification of connective tissue membrane, mesenchyme condenses and cells begin to produce collagen fibrils and thicken the matrix between fibrals, osteoblasts differentiate from mesenchymal cells then secrete collagen matrix, osteoblasts are ossification centers, forming trabeculae, adding additional layers, and fusing with other trabeculae, flat bones of skull, fracture repair
80
endochondral osteogenesis
intracartilaginous, bone forms to replace pre-existing cartilage model (hyaline), fracture repair
81
woven bone
remodels itself to make lamellar bone, early bone in both intramembranous and endochondral ossification,
82
Woven vs. lamellar bone
woven bone has irregular arrangement of collagen fibers, formed rapidly, not as strong, replaced by . . .
Lamellar bone: organized matrix, deposited in layers/ stronger
83
endochondral ossification
occurs in long bones in fetal development, mesenchymal cells become chondroblasts, hyaline cartilage model replaced by bone, bone collar forms on the outside of the cartilage model,
chondrocytes in center of model hypertrophy, calcify the matrix, and die
vessels invade the cartilage matrix, osteoblasts invade and begin to make bone, initially on the surface of calcified cartilage spicules
84
growth in length of bone
growth at physis (endochondral ossification),
| interstitial growth of cartilage provides length for ossification
85
physis
cartilage plate between epiphysis and diaphysis
86
which part of the bone is likely to become infected in the case of injury?
Where blood vessels turns within the inner calcified layer
87
Bone remodeling
bone is constantly remodeled throughout lifetime, cause change in shape due to mechanical stress
Facilitates calcium homeostasis, increases in diameter, repair of bone
88
growth in diameter
new bone deposition under periosteum,
| bone reabsorption along the interior edge (under endosteum)
89
reactive phase
fracture, hematoma, and inflammation
| granulation type tissue formation (new connective tissue and blood vessels, fills wound)
90
reparative phase
```
callus formation with woven bone, cartilage, and connective tissue
bone deposition (endochondral and intramembranous ossification
```
91
remodeling phase
converting woven bone to lamellar bone, may continue for years
92
sources of cells for remodeling
chondroblasts and osteoblasts from periosteum and endosteum, mesenchymal stem cells from bone marrow
93
Components of blood
1. Cells: erythrocytes and leukocytes
2. Cell fragments: Platelets
3. Plasma: mostly (91%) water and some proteins, gases, and ions
94
How is the ground substance different in blood?
There is no ground substance because plasma is not produced by the component cells
95
Clotting vs Sedimentation
Sedimentation occurs when clotting is prevented in order to distinguish the blood components
96
3 layer of sedimentation of blood
1. Erythrocytes, used to calculate PCV
2. Buffy coat: leukocytes and thrombocytes (platelets)
3. Plasma
97
Plasma
Fluid component of blood
~55% total blood volume.
Contains water soluble salts/ions and organic molecules like albumins, globulins, and fibrinogen
98
serum
plasma without fibrinogen and other clotting factors
99
Cell fragments in blood
Platelets/ thrombocytes, megakaryocyte fragments
| Function: homeostasis/clotting
100
Are platelets always fragments?
No, in some animals they are complete cells
101
How are platelets formed?
Megakaryocytes in bone marrow project cytoplasm into the blood vessel and fragments break off to become platelets
102
Platelet Activation
mediated by receptors, results in spiky shape,
degranulation: release of granules
aggregation
103
Granulocytes
segmented leukocytes: eosinophils, basophils, neutrophils
104
Agranulocytes
mononuclear leukocytes: monocytes, lymphocytes
105
erythrocytes
non-nucleated in mammals, biconcave disk shape (camelids have elliptical shape)
Hemoglobin rich
106
Neutrophils
granules do not stain, most common WBC in most species
| Early responder to infection, phagocytosis
107
Eosinophils
granules stain red to reddish-orange with eosin
Combat parasites
Can be source of inflammation in allergic reaction,
non-phagocytic
108
Basophil
granules stain blue with basophilic hematoxylin. Rare to find in circulation
Source of inflammation in an allergic reaction (histamine)
NOT related to mast cells
109
Monocyte
```
2-8% of WBC, enter the following tissues:
skin (langerhans cells)
bone (osteoclasts)
brain (microglia)
other tissues (macrophages)
```
110
Lymphocyte
T cells and B cells, second most common type of WBC in most species (most common in pigs and ruminants)
little cytoplasm and a large nucleus, smallest WBC (1.5 x RBC)
Need special stain to differentiate T and B cells
111
Hematopoiesis
formation of blood cells in bone marrow (adults, liver and spleen (young)
112
hematopoietic stem cells
arise from mesenchymal stem cells
| Multipotent myeloid and lymphoid cells are produced from division of pluripotent and are slightly more specialized
113
Does hematopoiesis take place in vascular or extravascular space of bone marrow?
Extravascular. vascular is continuous with blood stream.
114
How do the proportions of red and yellow bone marrow change with age?
Yellow marrow increases and red marrow decreases
115
What bone types have the most hematopoiesis?
Flat bones and epiphyses of long bones
116
Which cells come from common myeloid progenitor?
Everything except lymphocytes, including megakaryocytes
117
erythropoiesis
most active component of hematopoiesis.
Maturation takes 5-7 days or 3-5 when demand is high.
Reticulocytes are released into circulation and complete final maturation in a day. Contain RNA but no nucleus
118
Erythropoietin
(EPO) increases erythrocyte production, secreted by kidney, acts at all stages of erythrocyte maturation
119
Changes to RBC during maturation
size, nuclear size and basophilia decreases, hemoglobin increases
120
Last nuclear stage of erythropoiesis?
metarubricyte
121
Why is a blood smear necessary when we already have the blood count?
The count can include metarubricytes and rubricytes in the WBC rather than red
These progenitors have more cytoplasm than lymphocytes
122
Granulocyte production
developing neutrophils are most numerous in bone marrow. Maturation takes 6-9 days but shorter when needed. Last step is band cell
Some mature cells are stored in bone until they are needed (about 7x those that are in circulation)
123
What is important about the first stages of hematopoiesis?
these allow for the expansion of the cell
124
Monocyte production
allow with granulocytes
do not fully mature until enter tissue and become macrophages
Produces: macrophages, microglia, osteoclasts
125
How are granulocyte and monocyte production related?
directly, they occur alongside each other so if granulocyte production increases, so will monocyte production
126
megakaryocytes
produce platelets
| multinucleated cells
127
hemostasis
the process the causes bleeding to stop
| Includes: endothelial cells, platelets, coagulation factors
128
When does bleeding occur?
when a vessel is damage
129
What are the consequences of too much or too little hemostasis?
Too much: coagulation in vessel
| Too little: blood won't clot
130
Primary hemostasis
Platelet Plug
Contraction of vessel smooth muscle (vasoconstriction)
Platelet activation due to exposed collagen, adhesion/aggregation
endothelial cells and platelets release factors to facilitate plug formation
Granules released by platelets activates more platelets
131
von Willibrandes factor
vWF, increases stickiness of exposed collagen so platelets can stick
132
Secondary hemostasis
coagulation to form a fibrin meshwork
thrombin converts fibrinogen to fibrin (soluble to insoluble)
Fibrin production is the end result of several reaction involving coagulation factors, non enzymatic cofactors, calcium, and phospholipid membranes (mainly platelets)
133
Coagulation cascade
both intrinsic and extrinsic pathways in the animal.
Calcium is important cofactor. EDTA chelates calcium to stop coagulation
Inactive cofactors circulate within blood until they are activated. Pathways activated at point of injury
Many pathways are used to amplify signal to ensure coagulation
134
Which vitamin is a required cofactor for coagulation?
Vitamin K
135
Antithrombin III
inactivates thrombin, makes sure clot doesn't form in areas where it is not needed
136
Endothelial effects
inhibit platelet aggregation with NO, PGI2 and ADP
137
Disseminated Intravascular Coagulation
DIC, caused by endothelial damage (endotoxins from sepsis), platelet activation (some viruses), release of tissue procoagulants (HBC)
