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U5 Microscopic Anatomy > Cartilage and Bone > Flashcards

Cartilage and Bone Flashcards

1
Q

Functions of Cartilage

A
  1. Support of soft tissues
  2. Forms articular surface of long bones
  3. Growth in length of long bones
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2
Q

Cartilage ECM

A

Type II collagen maintains shape and provides tensile strength

Proteoglycan aggregates (between layers of collagen) provide resilience

Composition permits cartilage to bear mechanical stress without permanent distortion

GAGs: chondroitin sulfate 4, chondroitin sulfate 6, keratin sulfate

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3
Q

How to make a proteoglycan aggregate

A
  1. Begin with core proteins
  2. Add GAGs (creates proteoglycans)
  3. Bind proteoglycans to core of hyaluronic acid with link proteins
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4
Q

Morphological features of Chondrocytes

A

The only cells found in healthy cartilage

Round diffuse nucleus with prominent nucleolus

Cytoplasm rich in RER, well-developed Golgi and mitochondria (basophlic)

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5
Q

Identify

A

Hyaline cartilage (most common form) surrounded by perichondrium

Located on joint surfaces, tracheal rings, ventral end of ribs, nose, larynx, trachea, bronchi, epiphyseal plate

ECM: Type II collagen, basophilic

Chondrocytes live within lacunae - spaces in matrix.

Rich in sulfated GAGs in cytoplasm - makes ECM basophilic (blue)

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6
Q

Consequences of cartilage lacking blood vessels (avascular)

A
  1. Size limitation
  2. Low metabolic rate
  3. Poor potential for repair (except in young children)
  4. Systemic drug treatment is difficult (medically relevant)
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7
Q

Identify

A

Elastic cartilage (arrow to elastic fibers): located where flexible support is needed - external ear, epiglottis, eustachian tube, larynx

ECM: more flexible than hyaline, less homogenous, numberous elastic fibers (stain with orcein dyes)

Chondrocytes look identical to those in hyaline

Less susceptible to deneration/age change sthan hyaline

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8
Q

Identify

A

Fibrocartilage: Intervertebral discs (annulus fibrosus), pubic symphasis, menisci, some tendons

ECM : eosiniphilic (pink) ground substance reduced, collagen increased (type I predominates)

Chondrocytes look the same as those in elastic and hyaline

No perichondrium

Distinguish from dense regular CT: has irregular fiber distribution, fewer cells per unit area and rounder chondrocytes

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9
Q

Medical Conditions Assoicated with Cartilage

A
  1. Calcification of the matrix: hyaline cartilage is most susceptible, occurs with aging
  2. Osteoarthritis: loss/change in physical properties of articular cartilage, occurs with aging
  3. Chondroma: benign tumors
  4. Chondrosarcoma: slow growing malignant tumors
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10
Q

Functions of bone

A
  1. Supports fleshy structures
  2. Protects vital organs
  3. Harbors bone marrow
  4. Reservoir of calcium, phosphate, etc.
  5. Involved in body movement
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11
Q

Similarities between cartilage and bone

A
  1. Both supportive CT
  2. Bone consists mostly of ECM
  3. Osteocytes reside within lacunae
  4. Bone is surrounded by periosteum (specialized CT)
  5. Bone can grow by means of appositional growth
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12
Q

Differences between cartilage and bone

A
  1. Interstitial growth does not occur in bone
  2. Bone has a more regular arrangment of cells and fibers
  3. Bone is vascularized and has nerves
  4. Calcification of ECM is a normal process in bone
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13
Q

General structure of long bone

A

Diaphysis: cylindrical part, thick outer layer of compact (aka cortical) bone with thin marrow cavity containing spongy bone (aka cancellous or trabecular)

Epiphysis: bulbous ends, spongy bone covered by thin layer of compact bone

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14
Q

Canaliculi

A

In compact bone, small channels that radiate in all directions thru the ECM from each lacuna.

Connect (gap junctions) with canaliculi of adjacent lacunae for communication

Nutrients from intersitital fluid (in contact with capillaries)

Red squiggles in picture

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15
Q

Lamellae

A

Concentric layers of compact bone in an osteon that surround a central canal (Haversian Canal)

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16
Q

Osteocytes

A

Reside in lacunae, have processes that extend into canaliculi.

Adjacent osteocytes are in contact with one another via gap junctions - allows exchange of ions and small molecules (can provide nourishment for a chain of about 10 cells)

17
Q

Types of Lamellar Organization (compact bone)

A
  1. Haversian Canals: parallel to long axis of bone, have small blood vessels, loose CT, and nerves

Haversian system = osteon

  1. Volksman Canals: oblique angles to long axis of bone, connect Haversian canals to each other and to the free surface, not completely surrounded by concentric lamellae
  2. Interstitial lamellae: wedge-shaped regions between osteons, fragments of previous Haversian systems (continually made and destroyed)
  3. Inner circumferential lamellae: beneath endosteum
  4. Outer circumferential lamellae: beneath periosteum

(4 and 5 observed at external and internal surfaces)

18
Q

ECM of Bone: Organic Matrix (osteoid)

A

Responsible for toughness and resilience

  1. Type 1 collagen
  2. Non-collagenous proteins
  3. Ground substance (GAGs and proteoglycans)
19
Q

ECM of Bone: Inorganic Matrix

A

Responsible for hardness

  1. Calcium phosphate (hydroxyapatite): thin plates or crystals, associated with collagen fibers
20
Q

Identify

A

Osteoblasts

21
Q

Identify

A

Osteoprogenitor cells

Present in adults, have a low profile

Not actively making bone, but can be reactivated

Compact chromatin

Less basophilic cytoplasm

22
Q

Identify

A
  1. Haversian canal (lined by endosteum)
  2. Volksman canal
  3. Bone marrow

Periosteum on outside

23
Q

Identify

A
  1. Spongy bone
  2. Marrow cavity
  3. Compact bone
24
Q

Functional Adaptation (REMODELING)

A
  • Both spongy and compact bone are destroyed and replaced in a constant process throughout life
  • Involves relative activity of osteoblasts (make new bone) and osteoclasts (destroy bone). Need balanced activity to maintain skeletal integrity
  • Bone adapts to mechanical load placed on it - osteocytes are mechanotransducers of local strain

Spongy bone more responsivle to changes in load than compact bone

25
Q

Objectives of Functional Adaptation

A
  1. Provide maximal strength with minimal bone mass. Trabculae (aka spongy bone) follow lines of stress to do this.
  2. Remove microdamage and replace with new bone
26
Q

Identify

A

Osteoclasts

Large, multinucleated cells with eosinophilic (purple) cytoplasm and ruffled borders.

Rich in mitochondria and lysosomes

Attached to bone by podosomes that form a tight seal

Fx: break down organix matrix (via cathepsins) and bone mineral (acidic env)

Origin: fusion of monocytes

27
Q

Medical conditions associated with bone

A
  1. Osteoporosis: osteoclast activity enhanced (break down exceeds formation). Causes fractures (vertebral, hip). Seen when estrogen levels fall in menopause and in men over 50. Treated with bisphosphonates
  2. Osteopetrosis: defective osteoclasts, results in dense, heavy bone
  3. Osteogenesis imperfecta: insufficient type 1 collagen production, leads to bone fragility
  4. Rickets: abnormal calcification of bone matrix leads to soft bones, due to insufficient dietary Ca or lack of vitamin D in kids
28
Q

Location of cartilage in body

A

Nose

Intervertebral discs

Associated with ribs

Articular surfae of bones

Trachea, epiglottis, laynx, bronchi

Pinna of ear

Pubic symphysis

29
Q

Periosteum

A

Membrane covering outer surface of bone

  1. Outer (fibrous) layer: dense irregular CT, few fibroblasts, blood vessels enter Volkman’s canals, some collagen fibers anchor periosteum to bone
  2. Deeper (cellular) layer: osteogenic potential, osteoblasts present in baby, osteoprogenitors in adults
30
Q

Function of chondrocytes

A

Produce and secrete extracellular matrix (ECM)

Type II collagen determines tissue shape and produces tensile strength

Proteoglycan aggregates give resilience to tissue

ECM also has noncallagenous proteins

31
Q

Perichondrium

A

Dense irregular CT that surrounds hyaline and elastic cartilage (not articular cartilage)

Outer fibrous layer (type I collagen, fibroblasts)

Inner chondrogenic layer (more cellular, chondroblasts - retain ability to divide throughout fetal life)

Formed from mesenchyme

32
Q

Growth of cartilage

A
  1. Appositional: chondroblasts into chondrocytes, end up in lacunae. Add new cells and ECM to surface, latent in adults
  2. Interstitial (from within): chondrocytes capable of mitosis for a while, produce isogenous groups (clusters of cells), diminished with age
33
Q

Compact bone

A

a. Composed mostly of ECM
b. Lacunae form small cavities between lamellae (concentric patterns), each lacunae contains an osteocyte

Canaliculi radiate in all directions from each lacuna

34
Q

Endosteum

A

Lines the inner surface of bone and surface of vascular channels

More delicate, single layered structure

Site where osteoclasts resorb bone

35
Q

Spongy bone

(Aka cancellus, trabecular bone)

A

Found at the end of long bone

Lattice of branching bony trabeculae (functional unit)

Lined by endosteum

Filled with bone marrow - highly vascular

Intercellular substance of trabeculae: not concentricaly arranged around a canal (no Haversian canals), not penetrated by blood vessels, nourished from surface by canaliculi

Osteocytes idential to compact bone

36
Q

Identify

A

Pinna of ear

Stratified squamous keratinized epithelium on outside

Elastic cartilage in middle (S-shaped)

37
Q

Identify

A

Radius stained with thionine.

The marrow cavity (mc): large open area containing trabeculae of spongy bone (sb) and bone marrow. Completely surrounded by a thin collar of compact bone (cb).

Periosteum (p) covers the outside surface of the compact bone.

38
Q

Identify

A

Osteoclasts

U5 Microscopic Anatomy (6 decks)

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