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MSK > Histology > Flashcards

Histology Flashcards

1
Q

Cartilage Fxns

A
  1. Durable + resilient, compliant + cushioning
  2. Facilitate movement at joints
  3. Flexible support
  4. Mechanical protection
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2
Q

Cartilage histology

A
  1. Solid, non-mineralized ground substance
  2. Protein fibers vary in type and density
  3. Cells in lacunae
  4. Avascular and lacks innervation
  5. Perichondrium (outer dense CT layer) in some
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3
Q

Chondroblasts

A

Young chondrocytes

  1. Located at periphery
  2. In perichondrium if present
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4
Q

Chondrocytes

A

Produce ECM

1. In lacunae

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5
Q

Fibroblasts

A

Contributes to ECM

1. In perichondrium and fibrocartilage

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6
Q

Cartilage ECM

A

Provides support and protection
1. Protein fibers
A. Type II collagen: Mose prevalent, produced by chondrocytes
B. Elastic fibers: prevalent in elastic cartilage, produced by chondrocytes
C. Type I collagen: only in fibrocartilage, produced by fibroblasts and some chondrocytes
2. Ground substance
A. Aggregate complex: multiple aggrecan monomers (proteoglycans) attached to hyaluronan macromolecule
B. Multiadhesive glycoproteins

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7
Q

Hyaline cartilage

A
  1. Most common
  2. ECM
    A. Type II collagen: dec density
    B. Aggrecans in ground matrix [(-) charge]
    C. Stains basophilic (darkest near lacunae)
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8
Q

Elastic cartilage

A
  1. External ears, epiglottis
  2. Elastic fibers distributed thru ECM
  3. (-) charge => basophilic staining
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9
Q

Fibrocartilage

A
  1. IVD, pubic symphysis, meniscus
  2. Hyaline cartilage and dense CT
  3. ECM:
    A. Chondrocytes: basophilic stain
    B. Fibroblasts/Type I collagen: acidic stain
  4. Axially arranged isogenous groups
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10
Q

Chondrogenesis

A
  1. Aggregation of mesenchymal cells (usually mesoderm derived)
  2. Mitosis and differentiation into chondroblasts
  3. Production of ECM and isolation of chondrocytes
  4. Mitosis and formation of isogenous groups
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11
Q

Cartilage growth

A

Mitotic division chondrocblasts and chondrocytes -> ECM production

  1. Interstitial: chondrocyte proliferation in cartilage -> isogenous groups
  2. Appositional: in periphery or deep layer perichondrium if present
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12
Q

Cartilage repair (adults)

A 
1. Limited:
  A. Avascularity
  B. Low metabolic rate
  C. Chondrocyte immobility
  D. Limited proliferation
2. Damage often replaced w/ scar tissue
3. Damage underlying perichondrium can be repaired w/o tissue loss
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13
Q

Hyaline calcification

A

CaPO4 crystals accumulate in ECM

  1. Endochondral bone growth
  2. Articular cartilage contact bone tissue
  3. Aging process
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14
Q

Chondroma

A

Benign tumor in chartilage

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15
Q

Chondrosarcoma

A

Malignant tumor in cartilage

1. Rarely metastasize because avascularized

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16
Q

Bone fxn:

A
  1. Solid support
  2. Mechanical protection
  3. Movement via muscles
  4. Encloses medullary cavities
  5. Ca2+ and PO4 reservoir
17
Q

Bone histology

A
  1. Solid, mineralized ground substance
  2. Protein fibers vary in type and density
  3. Cells in lacunae
  4. Vascularized and innervated
  5. Periosteum (outer CT layer) usually present
    A. Except epiphysis
  6. Endosteum lines medullary cavity
18
Q

Periosteum

A

Well-vascularized and innervated (sensory) outer layer
1. Fibrous layer: outer layer of dense irregular CT
A. Fibroblasts => type I collagen
2. Cellular layer: osteprogenitor cells
A. Well-defined in growing bones
B. Osteoclasts/blasts
3. Perforating (Sharpey) fibers: penetration into underlying tissues
A. Most dense at tendon and ligament attachment sites

19
Q

Endosteum

A

Single layer CT lining spongy bone

1. Contains endosteal and osteoprogenitor cells

20
Q

Bone formation

A
  1. Osteoblasts -> osteocalcin + matrix vesicles + collagen + proteoglycans
  2. Osteocalcin binds Ca2+ and vesicles inc [PO4]
  3. Hydroxyapatite crystals in vesicles
  4. Crystals accumulate
    A. Embedded in collagen and proteoglycans
21
Q

Bone resorption

A
  1. Osteoclasts -> sealing zone
  2. H+ pumps -> acidic micro environment (pH 4.5) -> hydrolytic enzymes
    A. Hydroxyapatite dissolution
    B. Collagen breakdown
  3. Intracellular degradation
    A. Byproducts and Ca2+ -> bloodstream
22
Q

Intramembranous ossification

A
  1. Ossification centers in mesenchyme -> osteoprogenitors -> osteoblasts around capillaries
  2. Osteoblasts -> osteoid matrix -> woven bone -> traps blasts in lacunae
  3. Osteoblasts -> calcification -> enlargement
  4. Woven bone remodeled -> lamellar bone
    A. External/internal plates compact
    B. Cancellous central
  5. Non-ossified mesenchyme -> periosteum and endosteum
23
Q

Endochondral ossification

A
  1. Fetal hyaline cartilage model develops
  2. Cartilage calcifies and periosteal bone collar around diaphysis
  3. Primary ossification center in diaphysis
  4. Secondary ossification centers in epiphyses
  5. Bone replaces cartilage, except articular cartilage and epiphyseal plates
  6. Epiphyseal plate ossify -> epiphyseal lines
24
Q

Longitudinal bone growth

A
  1. Zone of reserve cartilage
  2. Zone of proliferation
    A. Growth
    B. Active chondroblasts
  3. Zone of hypertrophy: produces ECM
  4. Zone of calcified cartilage:
    A. Chondrocytes die off
    B. Calcification
  5. Zone of ossification
    A. Woven -> lamellar
25
Q

Remodeling

A
  1. Osteon formation
    A. Osteoclasts -> cutting cone tunnels thru old bone
    1. Resorption cavity fills w/ mesenchyme and loop of blood vessels
  2. Osteoblasts (cavity walls) -> osteoid matrix
    A. Apoptosis or osteocytes w/ completion
  3. Subsequent cycles -> concentric lamellae
    A. Why inner layer = newest
26
Q

Smooth muscle

A

Walls of hollow, visceral organs, arrector pili muscles, intrinsic eye muscles
1. Lateral plate mesoderm
2. Myocytes small and spindle shaped (fusiform), central uninucleated
3. Thin and thick filaments organized
A. Contraction modulated by calmodulin (Ca2+-binding protein)
4. Gap junction in sarcolemma coordinate contractibility
5. ANS innervation
A. Lack well-defined neuromuscular junction
B. Sympathetic and parasympathetic ratio varies
6. Paracrine factor control
A. NO-> vasodilation
B. Oxytocin -> uterine contraction
7. Contractibility slow and graded because of fluctuations in Ca2+ levels
8. Hypertrophy and hyperplasia
9. Regeneration repair

27
Q

Cardiac muscle

A

Only in walls of heart
1. Lateral plate mesoderm
2. Myocytes large, cylindrical, branching
A. Central uninucleated or binucleate (less)
3. Striated - not as uniform as skeletal
A. Contraction modulated tropomyosin C (Ca2+-binding protein)
4. All-or-nothing contraction
5. Intercalated discs connect (gap junctions)
6. Myogenic = can initiate own contraction
A. ANS acts on conducting system
7. Hypertrophy
8. Scarring = repair

28
Q

Skeletal muscle

A 
All somatic muscles
1. Paraxial mesoderm
2. Myocytes large, cylindrical, peripherally multinucleated 
3. Uniform striation
  A. Contraction modulated by tropomyosin C (Ca2+ - binding protein)
4. Sarcolemma attach CT around myofiber
5. Somatic efferent and afferent innervation
6. Hypertrophy
7. Repair
  A. Satellite cells - minor damage
  B. Scarring - extensive damage
8. All-or-nothing contraction
29
Q

Tendon

A

Dense regular CT bands w/ muscle fascia, usually attaches bony surfaces
1. Type I collagen w/ fibroblasts, some have inc elastic fibers
2. Covered by epitendineum
3. Fascicles w/in surrounded by endotendineum
A. Carries small vessels and nerves

30
Q

Aponeurosis

A

Broad, flat sheets of CT, multiple layers, perpendicular to neighboring layers

31
Q

Intrafusal fibers

A

Skeletal muscle tissue

  1. Modified
  2. W/in spindle fibers
  3. Proprioception
32
Q

Extrafusal fibers

A

Skeletal muscle fibers
1. Produce/resist movement at joint
2. Myofibrils: structural subunits of muscle fibers, arranged longitudinal and surrounded by SER and mitochondria, made of myofilaments
A. Thick filaments: myosin II fibers
B. Thin filaments: F-actin polymer (helical doublets of G-actin monomers) and other proteins
1. Modulate interactions between myosin heads and f-actin
2. Troponin complex: regulate position of tropomyosin
A. TnT: binds complex to tropomyosin
B. TnC: binds cytoplasmic Ca2+, initiates conformational changes -> exposes myosin binding site
C. TnI: regulate actin-myosin interaction

33
Q

Alpha-actin protein

A

Binds thin filaments to z-discs, inhibits dislodgment w/ contraction

34
Q

Titin

A

Largest protein in body
1. Supports and connects thick filaments to Z-disc
A. Scaffolding and elastic properties prohibit sarcomere overextension

35
Q

Myomesin

A

Form M-line and binds thick filaments in place

36
Q

Dystrophin

A

Secures fiber to external lamina and endomysium -> transmit force to tendons

37
Q

Immunohistochemistry

A

Fresh-frozen tissue exposed to antibodies that bind specific isoform/protein

38
Q

Enzyme histochemistry

A

Pre-incubated in acidic/alkaline solution -> selectively denatures ATPase isoforms
1. Enzyme substrates + tissue sample -> dark precipitate where enzymes active

MSK (13 decks)

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