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BIOL 3326 Exam 2 > Mineralized Tissues > Flashcards

Flashcards in Mineralized Tissues Deck (34):
1

Background on connective tissue

Cells + extracellular matrix

Matrix: can be gel-like, hard, fluid; usually protein
-supports and binds cells
-exchange medium
-"rigid" connective tissue with
A. Glycosaminoglycans (usually chondroitin sulfate), GAGs
B. proteoglycans (core protein with attached GAG chain)

2

Mineralization

Deposition of minerals (Ca and P salts) in connective tissue matrix

3

Advantages of mineralization

Mechanical strength/support

Storage for later use

4

If mineralized, cells in matrix may become isolated from blood...

=entombment

O2, CO2, nutrients

5

Mineralized examples

Bone, cartilage, dentin, enamel (or enameloid)

6

Common themes regarding mineralized tissue

A. Collagen is present
Collagen bundles form network for mineral deposition in connective tissue

B. hydroxyapatite is abundant in dentin and bone

7

Mineralization processes

1. Calcification
2. Dentin formation
3. Ossification

8

Calcification (calcified cartilage)

major cartilage components:
-fibroblast: collagen matrix
-chondroblast: sulfated GAGs and proteoglycans in matrix

chondroblasts entombed in lacunae = chondrocytes (cartilage cell) with reduced mitotic ability

diffusion supplies lacunar cells; poor vascular supply

repair of bone quicker than cartilage

9

compared to bone, cartilage...

-has a lower metabolic rate; avascular
-has different cellular and extracellular components (thus different structural properties)
-cells are chondrocytes suspended in semi-rigid matrix
-matrix with collagen and/or "fibrous proteins" (collagen absent in some lampreys and hagfishes, present in others)
-matrix is rich in polysaccharides

10

hyaline cartilage

least differentiated; translucent; often converted to bone

Ex, "growth plate" in limb bones, tracheal rings, articular surfaces of joints, larynx, nose

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fibrocartilage

intervertebral discs and pelvic girdle symphyses

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elastic cartilage

pinna, epiglottis

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calcified cartilage

Ca salts released into/form in matrix; usually hyaline or elastic; often appears bone-like

14

calcification

=calcium salts entomb chondrocytes; lacunar cell death

Ex:
-jaws of chondrichthyes
-endochondral bone formation before replacement by osseous tissue
-atypical - joint damage in osteoarthritis patients (calcium pyrophosphate dihydrate and calcium phosphate)

15

Dentin Formation

mineralization: cell vitality retained

forms only in dermis, usually near epidermal border

odontoblasts reside near dermal blood vessels

cytoplasmic extensions of ondontoblasts deposit dentin - odontoblastic process
-30% organic (collagen and GAGs)
-70% inorganic (hydroxyapatite)
-extensions project away from blood vessel

odontoblast "retreat" toward blood vessel; cell extenstions become embedded in dentin

odontoblastic processes become surrounded by dentin matrix

microscopic "tunnels" through mineralized tissue - canaliculi or dentin tubules

odontoblasts aggregate; dental pulp

dentin is usually covered by epidermal enameloid (enamel, ganoin)

enameloid produced by ameloblasts in epidermis

enameloid applied to surface of dentin teeth, fish scales

16

Ossification

not restricted to dermis

bone: always with collagen fiber matrix

spaces between fibers filled with hydroxyapatite

crystals bound to collagen by cementing substance (water and mucopolysaccharides)

hydroxyapatite hardens, cells extensions surrounded

microscopic tunnels though mineralized tissue = canaliculi

clusters of 2-4 osteoblasts reside in lacunae with interstitial fluid

cells retain direct/indirect access to vascular supply via canaliculi

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cementing substance similar to dentin, but...

-cells (osteoblasts) with cytoplasmic extensions in several directions
-osteoblasts are perivascular regarding vascular supply
-extensions contact other osteoblasts
-usually no cell retreat as hydroxyapatite produced

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bone: similar composition as dentin

30% organic (collagen and GAGs)
70% inorganic (hydroxyapatite)

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enamel

96% inorganic hydroxyapatite; acellular

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ameloblasts

enamelin and amelogenin, epidermis

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types of bone cells

osteoprogenitor
osteoblasts
osteocytes
osteoclasts

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osteoprogenitor cells

unspecialized; mesodermal mesenchyme origin; mitotic

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osteoblasts

bone-forming cells; osteogenesis; not mitotic

24

osteocytes

"mature" osteoblast; maintenance; not mitotic

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osteoclasts

derived from monocytes

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all bone ultimately derived from...

mesodermal mesenchyme

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Types of Bone

Presence/Absence of Cells:
-cellular bone
-acellular bone - common in fishes

Appearance:
-compact
-cancellous - spongy or trabecular bone (trabecular spaces and trabeculae)

Orientation of collagen:
-lamellar bone - regular arrangement of collagen and bone cells (think osteon)
-non-lamellar bone (spongy bone, dermal bone)

Formation:
-membrane bone
-endochondral bone

28

Haversian bone (osteonic bone)

=lamellar bone

mineralized collagen bundles surrounding haversian/osteonic canal; lamellae

Each canal: arteriole, venule, lymph vessel, neurons

Canal and surrounding lamellae with lacunae = osteon

blood vessels in osteon connected to blood vessels outside bone

29

Volkmann's canal

perforating canal - nutrient foramen

30

spongy bone (=cancellous bone)

porous, trabeculae

trabeculae = beams/bars, architectural trusses

trabeculae with irregular lamellae, no organized osteonic systems

31

red marrow

red marrow in spaces between trabeculae = hemopoietic/hemapoietic tissue

compare yellow marrow (in medullary cavity)

abundant in flat bones (roofing bones of skull, ribs, scapulae)

32

membrane bone

no cartilage precursor

mesodermal mesenchyme cells arrange in layers (sheet-like "membranes"; membranous blastema)

these cells become osteoblasts

33

types of membrane bone

1. dermal bone
2. perichondral/periosteal bone
3. heterotopic bones

34

heterotopic bones

usually respond to mechanical stress

-sesamoid bones
-os cordis (fibrous connective tissue between A&V, interventricular septum)
-baculum (in fibrous connective tissue above urethra; bats, rodents, dogs, some primates, otter, walrus, raccoon)
-rostral bone