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Microscopic Anatomy Unit 1 > Cartilage and Bone > Flashcards

Cartilage and Bone Flashcards

1
Q

Supporting CT

A

bone and cartilage

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2
Q

cartilage distribution

A
  • nose
  • articular cartilage
  • costal cartilage
  • intervertebral discs
  • pubic symphysis
  • external ear
  • epiglottis
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3
Q

functions of cartilage

A
  • support the soft tissues
  • forms articular surfaces of long bones
  • growth in length of long bones
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4
Q

Collagen in cart

A

maintains tissue shape and produces tensile strength

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5
Q

proteoglycan aggregates in cart

A

provide resilience

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6
Q

molecular organization in cartilage matrix

A

fiber reenforced gel

-permits cart to bear mechanical stress without permanent distortion

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7
Q

Proteoglycan aggregate synthesis

A
  • protein core and GAGs

- bind proteoglycan to a core of hyaluronic acid with link proteins to make aggregates

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8
Q

principle GAGs in cart

A
  • chondroitin 4-sulfate
  • chondriotin 6- sulfate
  • Keratan sulfate
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9
Q

Protein secreting cell-chondrocyte

A
  • round diffuse nucleus
  • prominent nucleolus
  • rich in RER
  • well developed Gogli
  • enough mitochondria
  • synthesizes collagens and other matrix components
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10
Q

ECM

A
  • proteoglycan aggregates

- type II collagen-fibrillar scaffold

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11
Q

Perochondrium

A
  • formed from mesenchyme surrounding center of chondrification
  • composed of two layers
  • outer, fibrous layer made of type I collagen and fibroblasts
  • inner, chondrogenic later made of chondroblasts
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12
Q

Appositional growth

A
  • mitosis of chondroblasts,
  • differentiation into chondroctyes, which produce and secrete ECM.
  • chondrocytes live in lacunae
  • adds new cells and ECM to surface
  • persists but latent in adult
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13
Q

Interstitial growth

A
  • growth from within
  • chondrocytes are capable of mitosis
  • daughter cells produce ECM
  • produce clusters of cells called isogenous groups
  • diminishes with age
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14
Q

Avascular consequences

A
  • size limitation
  • low MR
  • poor potential for repair (slow and often incomplete except for children)
  • systemic drug treatment is difficult
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15
Q

Types of cartilage

A
  • differ mainly in matrix composition

- hyaline, elastic, fibro cartilage

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16
Q

Hyaline cartilage

A
  • most common, found in ribs, trachea, larynx, bronchi, joints, epiphyseal plate, nose
  • fill lacunae
  • subjected to degenerative process-calcification
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17
Q

Hyaline cartilage matrix

A
  • proteoglycan aggregates and type II collagen
  • basophilic
  • capsular matrix around each lacuna that is more basophilic (richer in sulfated GAGs)
  • interterritorial matrix is less basophilic
  • type II collagen
  • produced by chondrocytes
  • nutrition of chondrocytes
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18
Q

type II collagen in hyaline ECM

A
  • 10-20 nm diameter fibrils

- lack 64 nm periodicity

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19
Q

Elastic cartilage

A
  • located where flexible support is needed- ear, epiglottis, eustachian tube, larynx
  • chondrocytes-same as in hyaline
  • less susceptible to degenerative or age related changes
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20
Q

Elastic cartilage matrix

A
  • more flexible than hyaline
  • less homogenous in appearance than hyaline
  • contains elastic fibers which stain specially with orcein dyes
21
Q

Fibrocartilage

A
  • annulus fibrosus, pubic symphysis, a few tendons, menisci of the joint
  • chondrocytes
22
Q

Fibrocartilage ECM

A
  • reduced amount of ground substance
  • increased amount of collagen, which causes matrix to be eosinophilic
  • usually type I collagen
23
Q

Vertebrae

A
  • nucleus palposus derived from notochord
  • end plate made of hyaline cartilage
  • annulus fibrosus is fibrocartilage
24
Q

fibrocartilage vs dense regular CT

A
  • irregular fiber distribution
  • fewer cells per unit area
  • rounder chondrocytes
25
Q

Functions of bone

A
  • supports fleshy structures
  • protect vital organs
  • harbors bone marrow
  • reservoir of calcium, phosphate, etc
  • movement
26
Q

similarities between bone and cartilage

A
  • supporting CT
  • mostly consists of ECM
  • oseocytes reside in lacunae
  • surrounded by periosteum-specialzed CT with osteogenic potential
  • appositional growth
27
Q

differences between bone and cartilage

A
  • no interstitial growth in bone
  • more regular arrangement of cells and fibers in bone
  • bone is vascularized and has nerves
  • ECM is normal for calcification
28
Q

spongy bone

A
  • cancellous, trabecular
  • consists of 3D lattice of branching trabeculae
  • form system of interconnecting spaces which are filled with bone marrow
29
Q

compact bone

A
  • more solid in appearance

- spaces only seen under microscope

30
Q

long bone

A
  • diaphysis- cylindrical part–thick outer layer of compact bone with thin narrow cavity containing spongy bone
  • epiphysis- bulbous ends–spongy bone covered by a layer of compact bone
31
Q

Compact bone micro

A

A.
- ECM laid down in lamellae
-within each lamella collagen fibers are oriented parallel to one another, but perpendicular to fibers in adjacent lamella-lacunae in concentric patterns in ECM
B.
-lacunae distributed in concentric patterns throughout ECM
-lacuna contains osteocyte which has cytoplasmic processes
-canaliculi radiate out from each lacuna
C.
-has specific lamellar patterns

32
Q

canaliculi

A

small channels that radiate in all directions through ECM from each lacuna, connect to adjacent lacunae and open to extracellular fluid

  • essential for nutrition of osteocytes
  • filopodial processes from osteocytes extend into canaliculi
  • processes of adjacent osteocytes make contact with one another via gap junctions
33
Q

three types of lamellar organization

A

1.concentric:
haversian canals (osteons)
volkmann canals

  1. inner and outer circumferential

3-intersitial

34
Q

haversian canals

A

-run parallel to long axis of bone and contain small blood vessles, loose CT, and nerves

35
Q

volkmann canals

A
  • run at oblique angle to the long axis of the bone

- connect haversian canals to each other and to the free surface

36
Q

outer and inner circumferential lamellae

A

inner is just beneath endosteum
outer is just underneath periosteum
-consist of a few lamellae that extend around the circumference of the shaft

37
Q

interstitial lamellae

A
  • angular fragments of lamellar bone (leftover)

- located between Haversian systems

38
Q

ECM of compact bone-organic

A
  • type I collagen
  • non-collagenous proteins
  • ground substance-GAGs and proteoglycans (not aggregated)
  • toughness and resilience
39
Q

ECM of compact bone-inorganic

A
  • calcium phosphate (hydroxyapatite)-thin plates or crystals, associated with collagen fibers
  • responsible for hardness
40
Q

outer layer of periosteum

A
  • consists of dense irregular CT
  • has a few fibroblasts
  • blood vessels which enter volkmans canals
  • some of its collagen fibers anchor periosteum to bone
41
Q

inner layer of periosteum

A
  • has osteogenic potential
  • appearance depends on functional state
  • osteoblasts present during embryonic and post natal growth
  • osteoprogenitor cells in adults
42
Q

osteoprogenitor cells

A
  • not actively making bone
  • low profile
  • compact chromatin
  • less basophilic cytoplasm
  • can be reactivated
43
Q

endosteum

A

more delicate single layered structure

  • lines surfaces of vascular channels
  • covers the tranbeculae of spongy bone
44
Q

spongy bone

A

a-3D lattice of branching bony trabeculae
b-interconnecting spaces that are lined with endosteum and filled with bone marrow
c-intercellular substance is lamellar- but not concentric, no BV, no canals-nourished via canaliculi
d-osetocytes are identical to compact- only nuclei visible in H&E, processes extend into canaliculi

45
Q

Remodeling of bone-functional adaptation

A
  • bone destroyed and replaced as soon as it is formed–whole skeleton once every 10 years.
  • occurs in spongy and compact
  • relative activity of osteoblasts and osteoclasts
  • bone adapts to mechanical load- osteocytes are mechanotransducers of local strain
  • remodeling removes microdamage
46
Q

major functions of functional adaptation

A
  1. maximal strength with minimum bone mass

2. removal of microdamage and replacement with new bone

47
Q

Osteoclasts

A
  • located in small pits on surface of bone-from fusion of monocytes (Howship’s lacunae or resorption bays)
  • multinucleated
  • eosinophilic in cytoplasm
  • ruffled border
  • rich in mito and lysosome
  • attached to bone with podosomes that form tight seal
  • break down organic matrix by means of lysosomal hydrolytic enzymes
  • dissolution of bone mineral by creating acid environment
48
Q

Osteoclasts 2

A
  • cathepsins- hydrolytic enzymes that digest organic matrix

- acid environment created by proton pump solubilized inorganic matrix, and provides optimum pH for hydrolytic enzymes

49
Q

osteoporosis

A
  • inbalance between osteoclasts and osteoblasts
  • osteoclasts may increase when estrogen decreases
  • resorption exceeds formation
  • skeletal fragility and increased susceptibility to fractures-vertebral common hip debilitating
  • treatment with bisphosphonates inhibit osteoclasts but can lead to osteonecrosis and increased risk of femoral fractures
  • also common among older men-20% over 50 have hip, spine, or wrist

Microscopic Anatomy Unit 1 (5 decks)

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