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Human Structure > Histology: Cartilage and Bone > Flashcards

Histology: Cartilage and Bone Flashcards

1
Q

Cartilage Characteristics and Functions

A
  • Avascular (limits the thickness)
    • Limited capactiy for repair
  • Extensive ECM
  • 3 Types:
    • Hyaline
    • Elastic
    • Fibrocartilage

Functions:

  • Shock absorbers
  • Reduce friction
  • Guide development and growth of long bones
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2
Q

Hyaline Cartilage

A
  • Most common type in body
    • ​Articular surfaces of joints
    • Respiratory Tract
    • Costal Cartilage
  • Appears “glassy” in fresh tissue
  • Chondrocytes (mature cartilage cells)
    • Produce and maintain ECM
    • Reside in lacunae
      • ​Isogenous groups (recently divided chondrocytes)
  • Composition
    • Mostly Water and ECM (NOT cells)
    • Type II Collagen
    • Aggrecan (proteoglycan)
  • Capsular Matrix (very basophilic, purple) immediately arround chondrocytes –> lots of proteins
    • Type VI collagen
  • Terrotial Matrix
    • Mostyle Type II and IX
  • Interstitial Matrix:
    • Type II collagen
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3
Q

Elastic Cartilage

A

Similar structure to hylaine cartilage

  • ECM contains lots of elastic fibers (requires fuchsin and orcein stains) in addition to type II collagen
  • Covered by Perichondrium
  • Found in ear, epiglottis
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4
Q

Fibrocartilage

A
  • Dense Regular CT and Hyaline Cartilage
    • ​ECM contains type I and type II collagen
      • Chondrocytes in a line
    • Also contains fibroblasts (arrows in picture)
  • No perichondrium
  • In anulus fibrosus of intervertebral disc
    (pubic symphysis and menisci)
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5
Q

Perichondrium

A

Dense CT covering

  • Growth and maintenance of cartilage
  • 2 Layers:
    • Inner Cellular Layer: mesenchymal stem cells for growth
    • Outer Fibrous Layer (type I collagen)
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6
Q

Appositional Cartilage Growth

A
  • Growth at the surface
  • Chondroblasts from perichondrium (inner cell layer) deposit matrix
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7
Q

Interstitial Growth

A
  • Growth from within
  • Chondrocytes proliferate
    • Occurs at epiphysial plate and articular cartilage
  • Fibrocartilage can only grow via interstitial growth
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8
Q

Bone Characteristics

A
  • Specialized CT with hard, mineralized matrix
  • Functions:
    • Support for body
    • Bone Marrow (blood cells)
    • Ca2+ and Phosphate reservoir
  • Two Types:
    • Immature (woven) bone
      • ​First appears in embryonic development
      • Temporary - remodeled to mature bone
      • Lower minteral content and more osetocytes
        • ​Appears more basophilic (purple)
    • Mature (lamellar) bone
      • ​Layers
      • Higher mineral content (stains more eosinophilic)
      • Compact Bone (dense)
      • Cancellous Bone (spongy)
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9
Q

Typical Long Bone

A

Diaphysis

  • Long shaft of compact bone with inner marrow cavity

Epiphysis

  • Expanded region of end of diaphysis
  • Spongy bone within outer shell compact bone

Metaphysis

  • Flared region between diaphysis and epiphysis
  • Spongy bone with shell of compact bone
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10
Q

Osteon

A
  • Structural and functional unit of compact bone
  • Central Canal in center (blood vessels and nerves)
  • Cement line: light area covering osteon
  • Lacunae (black dots)
    • Contains osteocytes
  • Canaliculi extend from lacunae
  • Perforating Canals
    • ​Connect adjacent central canals
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11
Q

Lamellae

A

Concentric Lamellae

Interstitial Lamellae (osteon remodeled)

Outer Circumferential Lamellae (outside diaphysis)

Inner Circumferential Lamellae (located around marrow cavity)

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12
Q

Cancellous Bone

A
  • Lamellar
  • Lacks osteons
  • Interconnected Spicules of bone covered by endosteum
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13
Q

Periosteum

A

Dense Fibrous CT

Covers outer surface of bones

2 Layers:

  • Outer fibrous layer
  • Inner cellular layer
    • ​Osteoprogenitor cells

Perforating Fibers

  • Collagen fibers the penetrate bone matrix to bind to periosteum
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14
Q

Osteoblasts

A

Arise from osteoprogenitor cells in periosteum and endostium

  • Cuboidal cell layer
  • Secrete osteoid (unmineralized bone matrix)
    • Lighter pink band in image
  • Secrete aklaline phosphatase
    • ​Promotes matrix calcification
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15
Q

Osteocytes

A

Derived from osteoblasts

  • Most abundant bone cell
  • In lacunae and extend cytoplasmic processes (canaliculi) into unmineralized matrix to contact adjacent osteocytes
  • Orchestrate bone remodeling
    • Signal osteoblasts or osteoclasts
    • Increased mechanical stress: more bone
    • Decreased mechanical stress: bone loss
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16
Q

Osteoclasts

A

Large, multinucleated cells

  • Derived from monocytes
    • requires M-CSF and RANKL
  • Involved in resorption and remodeling of bone
    • Pump acid (H+ and Cl-) to area being resorbed
    • Clear zone demarcates area
    • Basolateral side exocytoses digested material
17
Q

Osteoporosis

A

Decrease in bone density

  • OVERactive osteoclasts, underactive osteoblasts
18
Q

Osteopetrosis

A

Abnormally dense bones

  • Defective osteoclasts
19
Q

Bone Matrix

A

Osteoid (unmineralized matrix)

  • Organic component of bone
  • Type I collagen
  • Osteonectin
  • Osteoclacin

Hydroxyapatite Crystals (inorganic component)

  • Major calcium reservoir
  • Alkaline phosphatase necessary for formation of crystals
20
Q

Intramembranous Ossification

A
  1. Mesenchymal cells aggregate at ossification center
  2. Differentiate into osteoblasts and secrete osteoid
  3. Osteoblasts become osteocytes and matrix becomes mineralized
  4. Bony spicules grow via appositional growth
  5. Adjacent spicules join to form network of woven immature bone
  6. Growth and remodeling into mature bone

This process occurs in flat bones of skull

21
Q

Endochondral Ossification

A

Forming bone from cartilage model

  1. Mesenchymal cells aggregate and differentiate into condroblasts to produce cartilage model
  2. Perichondrial cells give rise to osteoblasts to form bony collar around diaphysis
  3. Chondrocytes hypertrophy
    1. Secrete alkaline phosphatase which calcifies cartilage matrix
  4. Chondrocytes die
  5. Blood vessels and osteoprogenitor cells penetrate bone collar
    1. Differentiate to osteoblasts to secrete osteoid onto calcified cartilage –> mixed spicule
  6. Osteoclasts remove woven bone and calficied cartilage to form osteon system
22
Q

Primary Ossification Center

A

In diaphysis of long bones

23
Q

Secondary Ossification Center

A

In epiphysis of long bones

Form after birth

Epiphyseal Plate:

  • Zone of Reserve Cartilage
    • Nearest epiphysis
    • No proliferation
    • Hyaline cartilage
  • Zone of Proliferation
    • ​Chondrocytes proliferate and organize into columns
    • Produce collagen and matrix (stains basophilic)
  • Zone of hypertophy
    • ​Chondrocytes enlarge
    • Secrete alkaline phosphatase
  • Zone of Calcified Cartilage
    • Cartilage matrix becomes calficied
  • Zone of Ossification
    • ​nearest diaphysis
    • new bone deposited/cartilage reabsorbed
24
Q

Fracture Repair

A
  • Blood from torn blood vessels forms hematoma
    • Hematoma removed by macrophages and replace dby soft (fibrocartilagenous) callus
    • Soft callus invaded by blood vessels with osteoblasts
      • Replaced by woven bone to form hard callus
      • Woven bone remodeled to form compact and cancellous bone
25
Q

Synarthroses

A

Little or no movement

Fibrous Joints:

  1. Sutures
  2. Syndesmosis (between radius and ulna)
    1. Held together by fibrous tissue
  3. Gomphosis (teeth)

Cartilagenous Joints:

  1. Synchondrosis (epiphyseal plates)
  2. Symphysis (intervertebral discs)
    1. Held together by fibrocartilage
26
Q

Diarthroses

A

Synovial Joints

  • Held together by fibrous capsule of Dense Regular CT
    • Filled with synovial fluid
  • Synovial Membrane:
    • Specialized CT (NOT EPITHELIUM)
    • Type A Synoviocytes
      • Macrophage like
    • Type B
      • ​Produce hyaluronan to attract water
  • Articular Cartilage
    • ​Hyaline cartilage NOT covered by perichondrium
    • Reduces friction and absorbs shock

Classified by shape/movement

Human Structure (30 decks)

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