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Question 1

How appears connective tissues in Epithelia, Nervous tissue and Muscle tissue?

Answer 1

In Epithelia, basement membrane is connecting epithelia cells to connective tissue under. two lagers in BM which are Basal lamina and Reticular lamina.

In nervous tissue, in the brain, a connective layer is surrounded outside of the brain called Meninges(“a meninx”), including Dura mater, arachnoid matter and pia mater(from outside to inside). Inflammation of meninges called “Meningitis”
Nervous structures is also surrounded by connective tissue, they are Endoneurium, Perineurium and Epineurium(from single axon to the nervous bundle)

In Muscle tissues, similar as in nervous structure, surrounded by connective tissue called Endomysium, Perimysium and Epimysium(from single muscle fiber to the muscle bundle)

There are other connective tissues as well such as Ligament (connecting bone to bone), Tendons (connecting muscle to bone) and Aponeurosis ( as a “flat tendon”).

Question 2

Classify the connective tissue.

Answer 2

• Embryonic CT
• Connective tissue proper
• Specialized CT, including Bone, Cartilage and blood

Question 3

Describe CT components.

Answer 3

All CT is formed by:
1. Extracellular matrix or ECM
  - ground substance
      . GAGs
      . proteoglycans
      . multiadhesive glycoproteins
  - protein fibers
      . collagenous
      . reticular
      . elastic  
2. Cells
   - resident
     eg: fibroblasts成纤维细胞, myofibroblasts肌成纤维 
     细胞, macrophages巨噬细胞, adipocytes脂肪细胞, 
     mast cells肥大细胞, mesenchymal stem cells间充质 
     干细胞...
   - transient or wandering
     eg: Lymphocytes(T cells, NK cells, B cells to plasma  
     cells), neutrophils嗜中性粒细胞, eosinophils嗜酸性 
     粒细胞, basophils嗜碱性粒细胞, monocytes单核细 
     胞

Question 4

Describe GAGs as ECM ground substance.

Answer 4

GAGs(glycosaminoglycans) is a long, unbranched polysaccharide chains build by repeating disaccharide blocks (disaccharide: Amino sugar and uronic sugar)

Based on the disaccharide structures, there are four classes under GAGs:

• chondroitin/dermatan sulfate
• keratan sulfate
• heparin/heparan sulfate
• hyaluronan/hyaluronic acid(none-sulfated)

GAGs attract water-molecules which gives connective tissue a jelly-like consistency&facilitates diffusion

Question 5

Describe the formation and the function of proteoglycans as ECM ground substance.

Answer 5

• GAGs attached to a protein core forms proteoglycans.
• Membrane-tethered and transmembrane forms exist
• Divers functions t.ex. regulation of collagen fibrillogenesis, roles in cell/cell and cell/ECM signaling, hydration.

Question 6

Difference between Multiadhesive Glycoproteins and proteoglycans?

Answer 6

The carbohydras/sugar chain content of a proteoglycan is usually much higher than that in multiadhesive glycoprotein, plus the sugar chain that attached on proteoglycan are usually long and unbranched GAGs. while in multiadhesive glycoprotein are usually short and branched.

Question 7

Describe the 4 groups of multiadhesive glycoproteins.

Answer 7

1, focal adhesion: connects the actin cytoskeleton to fibronectin
2, hemidesmosome: connects intermediate filaments to laminin
3, tenascin: play en important function of scar formations and wound healing, and tissue remodeling, including tumor formation
4, osteopontin: play functions during bone formulation,

Question 8

Describe the functions of collagen type I,II,III,IV and VI

Answer 8

Collagen type I: fiber forming, most abundant in our body, found in tendons, skin… can stains with H&E

Collagen type II: fiber forming, predominant collagen in cartilage

Collagen type III: forms reticular fibers (H&E negative), provides supportive scaffold for certain cell types

Collagen type IV: sheet-forming collagen in the basal lamina

Collagen type VI: attches chondrocytes (“cartilage cells”) to the ECM, forms a microfilament network

Question 9

Describe three types of protein fibers in ECM.

Answer 9

• Collagen fibers
  with the help of the enzyme proline hydroxylase,
  proline be modificated to hydroxyproline and then
  three collagen subunits of polypeptide protein chains
  which contains amount of glycine and hydroxyproline
  form a triple helix collagen molecule.
  The collagen molecule can do self-accembly and
  form the type I collagen fibril.
  Type I collagen fibers are flexible but inelastic, mainly
  build up by type I collagen. it is highly abundant i
  cartilage软骨, tendons肌腱, aponuroses腱膜 and
  ligaments韧带.

- Reticular fibers
   . Comparably thin fibers
   . made of type III collagen
   . form a network
   . H&E negative
   . contains more sugar compared to collagen type I 
     fibers(PAS, silver stain)

. Reticular fibers form a scaffold for many types of
cells(muscles, nerves, adipocytes)
. Important component of the reticular connective
tissue of the kidneys, spleen, lymph nodes and bone
marrow
. Abundant at early stages of wound healing/scar
formation

• Elastic fibers
  . Built of elastin and fibrillin
  . form a 3-dimensional network
  . increase flexibility/elasticity of connective tisse
  . poorly stained by eosin(can use orcein, Weigert’s)Elastic fibers are highly aboundant where
  flexibility/elasticity matters.