Connective Tissue (T-T) Flashcards

(53 cards)

1
Q

Origins of CT and cells within CT

A

Mesenchymal: Precursors to all of the CT family!

  • Gives rise to Osteoprogenitors, Fibroblasts, Chondrocytes.
  • All of these give rise to cells that make ECM components.
  1. Osteoprogenitors
    - -> Osteoblasts –> Osteocytes
2. Fibroblasts (pre-eminant cell)
gives rise to:
       --> Myofibroblasts
       --> Adipocytes
       --> Smooth muscles
or shifts into:
      --> osteoprogenitor
      --> chondrocytes
needs to be highly regulated or you're Fucked
very diverse secretory machines
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Mesenchymal cells

A

Precursor to all of CT family

Function in embryogenesis and/or stem cells for new CT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Osteoblasts

A

osteoBlasts Build Bone

  • actively secretes osteoid
  • secretes matrix vesicles that contain elements for calcification.
    - -> Enzymes inside vesicles are activated and ppt hydroxyappetite (Ca2+ and PO4). This ruptures the vesicles and activated cascade of mineralization in the matrix.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Osteocytes

A

derived from osteoblasts that are trapped in bone matrix in a lacuna

  • also build bone
  • extends canaliculi
  • form gap junctions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are some cells not made in CT but resides in the ECM?

aka “Immigrant blood derived cells”

A

White blood cells

  1. Lymphocytes
  2. Macrophages
  3. Neutrophils and Eosinophils
  4. Mast cells
  5. Osteoclasts

-migrate from blood into connective tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are white blood cells produced from?

A

Hematopoietic cells in bone marrow

blood cell precursors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Macrophages

A

large engulfing cells that phagocytose cells, ECM, ect

Act as signaling centers:

  1. Stimulates endothelial cells to undergo angiogenesis
  2. remodel damaged/undamaged tissue

-Tumor growth is aided by macrophages: supply blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Mast cells

A

secretory cells, when stimulated, release substances that promote swelling in CT

  • imp. in allergies
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Osteoclasts

A

derived from blood monocytes (which originate from hematopoietic stem cells in BM)

Function in bone resorption and remodeling.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Connective tissue function

A

Very dynamic

  1. Provide mechanical strength/support
  2. Conduct/control exchange of nutrients, metabolites, signaling ligands
  3. Directly control behavior and functions of cells that contact CT matrix (ECM)
    • control epi polarization/shape
    • guide/regulate cell migration through matrix
    • control cell proliferation, diffferentiation
    • tissue formation, organization, modification during disease
    • inflammation and repair
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

ECM

  • What is it?
  • What is the central CT cell type that makes the components of the ECM?
A

extracellular fibers embedded in gel-like mix, “ground substance”

-Fibroblasts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Fibroblasts produce certain components of the ECM, name some.

A

fibrous proteins
proteoglycans
signaling compounds (solutes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Two types of (extracellular) fibers

A
  1. collagens

2. elastins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

3 Types of Collagens

A
  1. Fibrillar collagen
  2. Fibril- associated Collagen
  3. Network-forming collagen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Fibrillar collagen

A

Consists of Collagen Type I and forms long, thick, rope like collagen bundles (fibrils)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Fibril-associated Collagen

A

make thin fibers connecting basal lamina to fibrillar collagen

also links fibrillar collagen to eachother

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Network-forming collagen

A

Consists of Type IV and form very thin fibers and form interlaced networks that form scaffold for basal lamina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Pop quiz!! What causes scurvy?

A

Non hydroxylation of proline residues of collagens

caused by vit C deficiency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Collagen is synthesized ______ and modified ______ and secreted and further modified _____

A
  1. intracellularly
  2. intracellularly
  3. extracellularly
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

N-telo peptides

A

N-terminal fragments cleaved off from collagen outside of the cell

  • clinically important: levels in urine/blood diagnose imp. CT/Bone diseases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Elastins
what are they?
what are they made of?

A

elastic fibers that are highly resilient/distend-able

made of elastin and fibrillin secreted by fibroblasts/smooth muscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

One important role CT has is inflammation and wound repair.

What are the sequences of events that occurs?

A
  1. Inflammation and blood clotting
  2. new tissue formation/proliferation
    - stimulates fibroblasts to release cytokines and growth factors
  3. Tissue remodeling
23
Q

What are Histamines secreted by during an immune response?

A

Mast cells to promote endothelial permeabilization

24
Q

What are bone and cartilage?

A

Specialized connective tissue

25
2 Functions of cartilage
1. provide resilient/pliable support structure 2. direct formation and growth of bone FYI: in the fetus, large amt of cartilage is replaced by bone
26
Chondrocyte - function - where they arise from
-make cartilage matrix and tissue of ECM (which encases them in matrix and come to reside in a LACUNA) - chondrocytes come from perichondrium
27
perichondrium
external layer of CT that surrounds cartilage that contains MSC/fibroblasts that gives rise to chondrocytes (which makes cartilage matrix/tissue)
28
Describe how cartilage grows in fetus and children vs adults
Fetus/Children: cartilage grows dramatically, and serves as template for conversion into bone. = good Adults: only articular surfaces of bones retain cartilage tissue. Limited repair ability. Cartilage still retains capacity to convert to bone = bad
29
3 basic types of cartilage - what are they distinguished by? - what are they?
distinguished by type of matrix they contain 1. Hyaline cartilage (most prominent) 2. Elastic cartilage 3. Fibrocartilage
30
Hyaline cartilage | -what is it made of?
full of thin collagen fibrils, proteoglycans and hyaluronic acid,
31
Elastic cartilage | -what is it made of?
contains thin collagen fibrils, proteoglycans as well -also contains shit ton of elastic fibers and interconnecting lamellae sheets
32
Fibrocartilage | -what is it made of?
contains large bundles of densely packed fibrous collagen for tendons (tough)
33
Cartilage is avascular, how does it overcome this issue?
It contains no blood vessels within its matrix, so all of the nutrients and metabolites it needs must diffuse to and from the perichondrium, facilitated by large amounts of hydrated glycosaminoglycans.
34
Different cell types found in bone
1. osteoprogenitor 2. osteoblasts 3. osteocytes 4. osteoclasts
35
How is bone matrix unique/different from most CT?
It contains lg amts of hydroxyappetite (crystallized Ca2+ and PO4) (meaning matrix is mineralized/calcified)
36
Components of bone ECM
1. Different cell types 2. hydroxyappetite/proteoglycans/glycoproteins 3. Haversian canals 4. Osteon 5. Volkmann's Canal
37
Haversian canals
channels that traverse long bone axis through compact bone -surrounded by lammellae in concentric rings
38
Osteon
"haversian system" Lamellae + haversian canal
39
Volkmann's Canal
Link haversian canals to eachother
40
Osteoid
unmineralized ECM of bone -secreted by osteoblasts
41
2 processes that lead to bone formation
1. Intramembranous ossification - in absence of pre-made cartilage tissue 2. Endochondral ossification - made from cartilage tissue (cartilage model)
42
Describe steps of Intramembranous ossification
1. Condensation: In CT, mesenchymal cells come together 2. Transform into Osteoprogenitors 3. Differentiate into Osteoblasts 4. Islands of Osteoblasts secrete osteoid 5. More islands convert/join 6. Trabecular network of bone forms- BV grow in network 7. Bone matrix calcifies
43
Describe steps of | Endochondral ossification
1. Mesenchymal cells --> Chondrocytes 2. Chondrocytes secrete matrix and encase self in lacuna 3. Cartilage continues to grow via appositional and interstitial growth 4. Diaphysis receives signal telling mesenchymal cells --> osteoprogenitors instead 5. Perichondrium transforms to periosteum 6. Chondrocytes enlarge/cartilage matrix calcify = signalling osteoclasts to degrade 7. Overall, osteoblasts and osteoclasts work together to calcify cartilage and deconstruct chondrocytes (continued endochondral growth promotes lengthwise growth of bone)
44
Appositional growth
growth of cartilage at surface (width/diameter - ONLY BY APPOSITIONAL GROWTH) - In perichondrium at cartilage surface, mesenchymal/fibroblasts --> chondrocytes = more hyaline matrix
45
Interstitial growth
growth of cartilage from within - Chondrocytes embedded in matrix continues to proliferate within their lacuna and secrete ECM = internal growth (because bone cant grow, but cartilage can lengthwise, then bone replaces the cartilage)
46
Epiphyseal plate
growth plate where secondary ossification centers are and where "growth" of long bones occur until full length of bone is achieved -replaced by epiphyseal line in adults
47
Diaphysis
Midshaft of long bone | where primary ossification centers are and where "growth" of long bones occur (bone eating up the cartilage)
48
Sequence of events that occur in bone remodeling
Once bone is already formed: lots of turn over 1. periosteum forms on surface of cartilage (from perichondrium) 2. osteoclasts become activated in specific regions and begin bone resorption 3. osteoclasts lay down new blood vessels and nerve pathways 4. osteoclasts signal osteoblast migration/secretion 5. osteoblasts initiate mineralization of osteoid (bone matrix)
49
Where does most of bone resorptive activity occur?
endosteal surface
50
defects in bone remodeling | -give examples of diseases
1. osteoporosis: defective bone formation = decrease in bone mass 2. osteopetrosis: defective bone resorption = increase bone mass 3. osteomalacia rickets: abnormal increase in uncalcified osteoid = bow legged 4. FOP: bony formation in loose CT where lymphocytes reside
51
What is bone and cartilage regulation mediated by?
1. short-ranged signals 2. long-ranged signals 3. mechanical stress 4. neuronal stimulation
52
short-ranged signals
produced in local bone environment contains Bone Morphogenic Proteins (BMPs), - can stimulate chondrogenesis or osteogenesis - control bone development and remodeling turn over
53
Long range signaling examples Calcitonin PTH Vit D
Calcitonin: increase Ca2+ deposition/uptake, and decrease osteoclast activity Parathyroid hormone: increase Ca2+ resorption in blood, and increase osteoclast activity Vit D: stimulate Ca2+ uptake from intestine