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HISTOLOGY & EMBRIOLOGY II > LECTURE 3 (Cartilage III) > Flashcards

LECTURE 3 (Cartilage III) Flashcards

1
Q

What is Cartilage?

A

A tough, durable form of supporting connective tissue characterised by an extracellular matrix with high concentrations of GAGs and proteoglycans interacting with collagen and elastic fibers

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2
Q

What are the functions of cartilage?

A
  • Firm consistency -> allows the tissue to bear mechanical stresses without permanent distortion
  • In respiratory tract, ears and nose -> framework for supporting softer tissues
  • Resiliency and smooth lubricated surface -> Provides cushioning and sliding regions within skeletal joints
  • Facilitates movement
  • Guides development and growth of long bones
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3
Q

Cartilage consists of cells called ______________

A

Chrondocytes

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4
Q

What is the function of chrondocytes?

A

synthesise and maintain all ECM components and are located in matrix cavities called lacunae

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5
Q

What do the physical properties of cartilage depend on?

A

Electrostatic bonds between type II collagen fibrils, hyaluronan and sulphated GAGs on densely packed proteoglycans

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6
Q

What allows cartilage to serve as a shock absorber?

A

The high content of bound water

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7
Q

Describe the blood supply of cartilage

A
  • Cartilage lack vascular supplies but chrondocytes receive nutrients by diffusion from capillaries in surrounding connective tissue
  • Avascular -> chrondocytes exhibit low metabolic activity
  • Cartilage lacks nerves
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8
Q

What is the Perichondrium?

A

A sheath of dense connective tissue that surrounds cartilage in most places, forming an interface between the cartilage and the tissues supported by the cartilage

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9
Q

What is the function of the Perichondrium?

A

It harbours the blood supply serving the cartilage and a small neural component

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10
Q

Articular cartilage lacks _______________

A

Perichondrium

Therefore it is sustained by the diffusion of oxygen and nutrients from the synovial fluid

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11
Q

What are the three main types of cartilage?

A
  • Hyaline Cartilage
  • Elastic Cartilage
  • Fibrocartilage
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12
Q

What are the properties of Hyaline Cartilage?

A
  • Most common of the three types of cartilage
  • Homogenous and semi-transparent in the fresh state
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13
Q

Where is Hyaline Cartilage located in adults?

A
  • Articular surfaces of movable joints
  • Walls of larger respiratory passages
  • Ventral ends of ribs
  • Epiphyseal plates of long bones
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14
Q

Where is Hyaline Cartilage located in the embryo?

A

Forms the temporary skeleton that is gradually replaced by bone

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15
Q

Describe Osteoarthritis

A

A chronic condition that commonly occurs during ageing and involves the gradual loss or changed physical properties of the hyaline cartilage that lines the articular ends of bones in joints

Fragments released by wear-and-tear to the articular cartilage trigger secretion of MATRIX METALLOPROTEINASES and factors from MACROPHAGES in adjacent tissues -> Exacerbate damage and cause pain and inflammation within the joint

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16
Q

In histologic preparations, what is seen in the matrix?

A

Proteoglycans make the matrix basophilic and thin collagen fibrils are barely discernible

17
Q

What is the most abundant proteoglycan of hyaline cartilage?

A

Aggrecan

150 GAG side chains of chondroitin sulfate and keratan sulfate. Hundreds of these proteoglycans are bound non-covalently by link proteins to long polymers of hyaluronan.

18
Q

What is Chondronectin?

A
  • Structural multi adhesive glycoprotein in cartilage matrix
  • Binds specifically to GAGs, collagen and integrins mediating the adherence of chrondocytes to the ECM
  • Stains differently since richer in GAGs than collagen
19
Q

Describe the arrangement of Chrondocytes in cartilage

A
  • At the PERIPHERY = young chrondocytes/chrondoblasts have an ELLITIC SHAPE with long axes parallel to the surface
  • DEEPER = round and appear in groups of up to 8 cells that originate from mitotic division of chrondoblasts (ISOGENOUS AGGREGATES)
  • Chrondocytes become more active in secreting collagens -> aggregated cells and pushed apart and occupy separate lacunae
20
Q

What is the difference between chrondocytes in living tissue and in histologic preparation?

A

LIVING TISSUE - fill their lacunae completely
IN HISTOLOGIC PREPARATION - irregular shape and retraction from matrix since cartilage cells shrink

21
Q

What does calcification to hyaline cartilage result in medically?

A

Hyaline cartilage is susceptible to partial or isolated regions of calcification during ageing -> Calcification of hyaline matrix with degenerative changes in chrondocytes -> Cells of cartilage give rise to BENIGN (CHONDROMA) or slow-growing MALIGNANT (CHONDROSARCOMA) tumours that can metastasise -> Removed surgically

22
Q

All hyaline cartilage is covered by a layer of dense connective tissue, the _______________, which is essential for growth and maintenance of cartilage

A

Perichondrium

23
Q

Describe the Perichondrium

A

Outer region consists of COLLAGEN TYPE I FIBERS and FIBROBLASTS but the inner layer adjoining the cartilage matrix contains MESENCHYMAL STEM CELLS which provide a source for NEW CHRONDOBLASTS that divide and differentiate into CHRONDOCYTES

24
Q

What differentiates Elastic Cartilage from Hyaline Cartilage?

A
  • Abundant network of elastic fibers
  • Fresh elastic cartilage is a yellowish colour
  • Elastic fibers provide greater flexibility
25
Q

Where can Elastic cartilage be found?

A
  • Auricle of the ear
  • Walls of the external auditory canals
  • Auditory tubes
  • Epiglottis
  • Upper respiratory tract
26
Q

Where is Fibrocartilage found?

A
  • Intervertebral discs
  • Attachments of certain ligaments
  • Pubic symphysis

[places where it serves a very tough, yet cushioning support tissue for bone]

27
Q

What differentiate fibrocartilage from hyaline and elastic cartilage?

A
  • Scarcity if proteoglycans makes fibrocartilage matrix more acidophilic
  • No distinct surrounding perichondrium
28
Q

Describe chrondocytes of fibrocartilage

A
  • Occur singly
  • Occur in aligned isogenous aggregates producing type II collagen and other ECM components
  • Matrix around chrondocytes is sparse
  • Areas with chrondocytes and hyaline matrix are separated by regions with fibroblasts and dense bundles of type I collagen which give extra tensile strength
29
Q

Describe the major stages of Chondrogenesis/Embryonic cartilage formation

A

1) MESENCHYME is the precursor of all types of cartilage. Mesenchymal cells round up, retract their extensions, multiply rapidly and become more densely packed together
2) MITOSIS and initial cell differentiation produces a tissue with CHRONDROBLASTS
3) CHRONDROBLASTS are separated from one another by their production of various matrix components which collectively SWELL with water and form the ECM
4) MULTIPLICATION OF CHRONDROBLASTS within the matrix gives rise to ISOGENOUS CELL AGGREGATES surrounded by a condensation of TERRITORIAL MATRIX -> In mature cartilage, the interstitial mitotic activity stops and all chrondocytes become widely separated by their production of matrix

30
Q

Describe what happens with cartilage during embryonic development

A

During embryonic development, CARTILAGE DIFFERENTIATION takes place from the centre outward -> central cells have characteristics of CHRONDROCYTES and peripheral cells are typical CHRONDROBLASTS -> Superficial mesenchyme develops as the PERICHONDRIUM

31
Q

Cartilage tissue enlarges by two types of growth, what are they?

A
  • INTERSTITIAL GROWTH = mitotic division of preexisting chondrocytes
  • APPOSITIONAL GROWTH = involves chondroblast differentiation from progenitor cells in the perichondrium
32
Q

Why are cells and matrix near the articulating surface gradually worn away and must be replaced from within?

A

There is no perichondrium to add cells by appositional growth

33
Q

What is the poor capacity of cartilage for repair and regeneration due to?

A
  • Avascularity
  • Low metabolic rate
34
Q

What is the difference between the territorial matrix and the interterritorial matrix?

A

TERRITORIAL MATRIX
- ECM immediately around each lacuna
- Contains mostly proteoglycans and sparse collagen

INTERTERRITORIAL MATRIX
- Distant from lacunae
- Richer in collagen
- Less basophilic

35
Q

What are the properties of Hyaline Cartilage?

A

MAIN FEATURES OF ECM = Homogenous with type II collagen and aggrecan
MAJOR CELLS = Chondrocytes & Chondroblasts
TYPICAL ARRANGEMENT OF CHONDROCYTES = Isolated or in small isogenous groups
PRESENCE OF PERICHONDRIUM = Yes
MAIN LOCATIONS = Upper respiratory tract, Articular ends and epiphyseal plates of long bones, foetal skeleton
MAIN FUNCTIONS = Provides smooth, low-friction surfaces in joints, structural support for respiratory tract

36
Q

What are the properties of Elastic Cartilage?

A

MAIN FEATURES OF ECM = Type II Collagen, Aggrecan and darker elastic fibres
MAJOR CELLS = Chondrocytes, Chondroblasts
TYPICAL ARRANGEMENT OF CHONDROCYTES = Usually in small isogenous groups
PRESENCE OF PERICHONDRIUM = Yes
MAIN LOCATIONS = External ear, external acoustic meatus, auditory tube, epiglottis and other laryngeal cartilages
MAIN FUNCTIONS = Provides flexible shape and support of soft tissues

37
Q

What are the properties of Fibrocartilage?

A

MAIN FEATURES OF ECM = Type II collagen and large areas of dense connective tissue with Type I collagen
MAJOR CELLS = Chondrocytes, Fibroblasts
TYPICAL ARRANGEMENT OF CHONDROCYTES = Isolated or in isogenous groups arranged axially
PRESENCE OF PERICHONDRIUM = No
MAIN LOCATIONS = Intervertebral discs, Pubic symphysis, Meniscus, Insertions of tendons
MAIN FUNCTIONS = Provides cushioning, tensile strength and resistance to tearing and compression

HISTOLOGY & EMBRIOLOGY II (13 decks)

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