Chapter 3 Connective tissue Chapter 3 Connective tissue

1. General features: 1. General features: 1) small number of cells and large amount of extracellular matrix (intercellular material) 1) small number of cells and large amount of extracellular matrix (intercellular material) 2) the extracellular matrix is composed of fibers and an amorphous ground substance 2) the extracellular matrix is composed of fibers and an amorphous ground substance 3) all of them originate from mesenchyme -embryonic CT 3) all of them originate from mesenchyme -embryonic CT 4) functions: connection, supporting, protecting, nutrition, defense and repairing 4) functions: connection, supporting, protecting, nutrition, defense and repairing

2. Classification 2. Classification Connective tissue proper Connective tissue proper Cartilage Cartilage Bone Bone blood blood The types of CT are determined on the basis of the types of cell and the characteristics of the extracellular matrix

CT in narrow sense means connective tissue proper, include: loose CT adipose tissue reticular tissue dense CT

Loose connective tissue (areolar tissue) Loose connective tissue (areolar tissue) The most common type of connective tissue The most common type of connective tissue consists of most types of cell and all the kinds of fibers consists of most types of cell and all the kinds of fibers The most widely distributed in the body The most widely distributed in the body

functions: connection, supporting, defense and repairing

1)Cells:

① fibroblast ---structure: LM: LM: large,flattened cell with processes, satellate in shape large,flattened cell with processes, satellate in shape Large ovoid pale nucleus - contain more fine chromatin, with clear one or two nucleoli Large ovoid pale nucleus - contain more fine chromatin, with clear one or two nucleoli Weakly basophilic cytoplasm Weakly basophilic cytoplasm

EM: rich in rough endoplasmic reticulum (RER), Golgi complex and free ribosome rich in rough endoplasmic reticulum (RER), Golgi complex and free ribosome ---function: synthesis of fibers and ground substance

fibrocyte: still state or inactive fibroblast ---structure: spindle-shaped, small spindle-shaped, small small, dark nucleus small, dark nucleus Acidophilic cytoplasma Acidophilic cytoplasma EM: less organelles EM: less organelles ---function: become into fibroblast for repairing fibroblast for repairing

fibrocyte fibroblast fibroblast

② macrophage ---structure: LM: LM: Round, ovoid or irregular in shape Round, ovoid or irregular in shape have short blunt processes: pseudopodium have short blunt processes: pseudopodium Small and dark nucleus Small and dark nucleus Acidophilic cytoplasm Acidophilic cytoplasm

EM: rich in EM: rich in lysosome lysosome Phagosome: phagocytosis Phagosome: phagocytosis pinosome : pinocytosis pinosome : pinocytosis Residual bodies Residual bodies Microfilament and microtubule Microfilament and microtubule

---function: a. Chemotaxis: chemotactic factor a. Chemotaxis: chemotactic factor b. phagocytosis: b. phagocytosis: (1)Special phagocytosis: recognize bacterium, virus and foreign cell phagocytosis

(2)non special phagocytosis: carbon particles, dust and dead cells

c. Bioactive product secretion: lysozyme, complement and interleukin-1 (IL-1)and interferon(INF) c. Bioactive product secretion: lysozyme, complement and interleukin-1 (IL-1)and interferon(INF) d. antigen presenting function d. antigen presenting function

③ plasma cell ---structure: LM: round or ovoid in shape round or ovoid in shape Nucleus with more clock-liked heterochromatin which located eccentrically Nucleus with more clock-liked heterochromatin which located eccentrically Basophilic cytoplasm Basophilic cytoplasm

EM: rich in parallelly arranged RER, free ribosome and Golgi complex ---function: synthesize and secrete immunoglobulin, Ig- antibody

④ mast cell ---structure: LM: round and large cell round and large cell Small dark-stained nucleus Small dark-stained nucleus Basophilic secreting granules--metachromatically Basophilic secreting granules--metachromatically

Basophilic secreting granules: heparin: an anticoagulant heparin: an anticoagulant Histamine: increase vascular permeability, capillary leakage to form edema, promotes the contraction of the smooth muscles Histamine: increase vascular permeability, capillary leakage to form edema, promotes the contraction of the smooth muscles Eosinophil chemotactic factor Eosinophil chemotactic factor Other bioactive chemicals Other bioactive chemicals

---function: involved in allergic reaction

⑤ fat cell ---structure: large, round or polygonal large, round or polygonal flattened ovoid nucleus located on one side of cell flattened ovoid nucleus located on one side of cell thin layer of cytoplasm thin layer of cytoplasm a large lipid droplet a large lipid droplet ---function: synthesize and store fat

⑥ undifferentiated mesenchymal cell ---structure: similar to fibrocyte ---structure: similar to fibrocyte ---function: multi-differentiating potential ---function: multi-differentiating potential

⑦ leukocytes: neutrophil, acidophil and lymphocyte ⑦ leukocytes: neutrophil, acidophil and lymphocyte neutrophilacidophil lymphocyte

2) fibers

① collagenous fiber (white fiber) LM: 1-20 um in diameter 1-20 um in diameter Belt-liked wave and branch to form a network Belt-liked wave and branch to form a network Eosinophilic Eosinophilic

EM: parallel-arranged fibrils Fibril: nm in diameter nm in diameter Have periodic cross striation at 64nm interval Have periodic cross striation at 64nm interval

*formation of collagenous fibers: collagen (type I and III) collagen (type I and III) collagenous fibril collagenous fiber

② elastic fiber (yellow fiber) LM: LM: thinner and less, um thinner and less, um Slight red (HE) Slight red (HE) branch and form a network branch and form a network EM: EM: core: an amorphous substance--elastin-low electron density core: an amorphous substance--elastin-low electron density Peripheral: microfibril nm, electron dense Peripheral: microfibril nm, electron dense function rubber-like properties rubber-like properties

③ reticular fiber LM: thin and less, um in diameter thin and less, um in diameter Branch to form a delicate network Branch to form a delicate network Argyrophilic fiber (stained by silver nitrate) Argyrophilic fiber (stained by silver nitrate) PAS+ PAS+

EM: type III collagen type III collagen 64nm cross striation 64nm cross striation---distribution: reticular tissue reticular tissue connecting portion, e.g. reticular lamina connecting portion, e.g. reticular lamina

3) ground substance amorphous colloidal substance, occupies space between cells and fibers. amorphous colloidal substance, occupies space between cells and fibers. Consists mostly of Proteoglycans and Hyaluronic acid. Consists mostly of Proteoglycans and Hyaluronic acid. Proteoglycans are very large molecules with a protein core and many long-chained polysaccharides (glycosaminoglycans, GAGs) covalently bound to the core protein. the core protein.

GAGS: Hyaluronic acidHeparan sulfate Hyaluronic acidHeparan sulfate Chondroitin 4- and 6-sulfateHeparin Chondroitin 4- and 6-sulfateHeparin Dermatan sulfateKeratin sulfate Dermatan sulfateKeratin sulfate

Molecular sieve: The entangled macro-molecular proteoglycan aggregate forms a bottle brush-like structureThe entangled macro-molecular proteoglycan aggregate forms a bottle brush-like structure To exclude or entrap molecules of different sizesTo exclude or entrap molecules of different sizes Serves as a physical barrier to prevent the spread of bacteria and other microorganisms.Serves as a physical barrier to prevent the spread of bacteria and other microorganisms.

tissue fluid Arterial end→ Tissue fluid → venous end →blood steam oxygen, nutrients waste material, carbon dioxide oxygen, nutrients waste material, carbon dioxide cells cells Acts as the midium for exchange of metabolites between circulating and tissue cells Acts as the midium for exchange of metabolites between circulating and tissue cells

4. Dense connective tissue 4. Dense connective tissue ---more fiber ---connection and supporting

1) regular DCT: parallel-arranged collagenous fibers parallel-arranged collagenous fibers tendon cells: special fibroblast tendon cells: special fibroblast ---distribution: tendons, ligament and cornea

2) irregular DCT: Fiber arranged in bundles, running in different direction Fiber arranged in bundles, running in different direction Less fibroblast and less ground substance Less fibroblast and less ground substance Form a three-dimensional network and to provide adequate resistance to stress from all directions Form a three-dimensional network and to provide adequate resistance to stress from all directions ---distribution: dermis, sclera and capsule of some organs

5. adipose tissue 5. adipose tissue ---LCT + fat cells Fat cells from large aggregations and become the principal cells Fat cells from large aggregations and become the principal cells Serves as metabolic energy reservoir, an insulating layer to conserve body heat Serves as metabolic energy reservoir, an insulating layer to conserve body heat

6. reticular tissue 6. reticular tissue ---reticular cells: stellate with processes-form network stellate with processes-form network round, ovoid and pale nucleus with 1-2 nucleoli round, ovoid and pale nucleus with 1-2 nucleoli EM: rich in RER EM: rich in RER ---reticular fiber: connect to form network ---distribution: hemopoietic tissue and lymphatic tissue