Connective Tissue

Li-zhongjie

1. Introduction

Connective tissue is versatile ， the types including Connective Tissue proper and the specialized Cartilage ， Bone and Blood.

Connective tissue comprises a diverse group of ce

lls embedded in a tissue-specific extracellular ma

trix （ ECM ） .

M esenchymal cell

structure: 1)stellate in shaped with processes 2)a large nucleus,with clear nucleoles 3)slight basophilic cytoplasm

function: 1) undifferentiated cell 2) multiple developmental potential

1.1 Classification Connective Tissue proper Loose connective tissue ※ Dense connective tissue Adipose tissue Reticular tissue Cartilage ※ Bone ※ Blood ※

1.2 Component

Connective tissue

Cell

Extracellular matrix （ ECM ） Fiber

amorphous Ground substance

1.3 Characteristics

Have small number of cells but have much extracellular matrix. all of them originate from mesenchyme-embryonic CT have functions of connection, supporting, protecting, nutrition, d

efence and repairing

2. Connective tissue proper

Loose(areolar) connective tissue※

Dense connective tissue

Adipose tissue

Reticular tissue

CT in narrow sense means connective tissue proper, include:

loose CT adipose tissue reticular tissue dense CT

2.1 Loose connective tissue

1) consists of 7 types of cells, 3 t

ypes of fiber and ground substanc

e

2 ） The most widely distributed

in the body

3) functions: connection, supporti

ng, defence and repairing

2.1.1 Cells in loose connective tissue

there are 7 types of cells present in LCT ※

Fibroblast※Macrophage※Plasma cell ※ Mast cell ※ Fat cellundifferentiated mesenchymal cell ※ Leukocytes

① fibroblast

---structure:

LM:

•large,flattened cell in shaped

•Large ovoid pale nucleus with clear one-two nucleoli

•Weakly basophilic

EM: rich in RER, Golgi complex a

nd free ribosome

---function: synthesize fibers and ground substance

Synthesis of collagenous fiber in three steps:

a. a. synthesis of procollagen (RER) → process (Golgi) → procollagen → out of cell

b. b. procollagen→ tropocollagen → fibril

c. c. fibril → collagenous fiber

fibrocyte: still state or inactive fibroblast

---structure: spindle-shaped, small small, dark nucleus Acidophilic cytoplasma

EM: less organelles

---function: become into fibroblast for repairing

②macrophage

（ The mononuclear phagocyte system ）

---structure:

LM: round or ovoid-irregular in shape Small and dark nucleus Acidophilic cytoplasm

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

---function:

a.    Chemotaxis: chemotactic factor

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, interleukin-1 (IL-1), interferon

(INF) and growth factor.

d.  antigen presenting function

*capture antigen→processes→+ MHC II molecule (major histocompatibility complex molecules) →antigen-MHC II complexes→T lymphocytes

Monocyte in blood is the precursor of macrophages

Liver: Kupffer cells Central nervous system: microglial cell

s Skin: Langhans cells Lymph node: dendritic cells Bone: osteoclast

The mononuclear phagocyte system

③plasma cell---derive from B lymphocyte

---structure:

LM: round or ovoid Round eccentrically-located nucleus with m

ore spot-liked heterochromatin Basophilic cytoplasm

---EM: rich in parallelly arranged RER, free ribosome and Golgi complex

---function: synthesize and secrete antibody（ immunoglobulin ）

④mast cell

---structure:

LM: round and large cell Small dark-stained nucleus Basophilic secreting granule

s

Basophilic secreting granules:

heparin: an anticoagulant Histamine: increase vascular permeability, capillary

leakage to form edema, promotes the contraction of the smooth muscles

Eosinophil chemotactic factor Other bioactive chemicals

EM Membrane bound granule

s A few Mitochondria A little RER

Function: cause allergic reaction

⑤fat cell

---structure: large, round or polygonal flattened ovoid nucleus located on one side of cell thin layer of cytoplasm a large lipid droplet

---function: synthesize and store fat

---structure:similar to fibrocyte

---function: multidifferentiating potential

⑥undifferentiated mesenchymal cell

⑦leukocytes:

Granulocyte: neutrophil, eosinophil and basophil

Agranulocyte: lymphocyte (B, T) monocyte

A. Classification of CT B. 7 types of cell in LCT 1. fibroblast 2. macrophage 3. plasma 4. mast cell 5. fat cell 6. undifferentiated mesenchymal cells 7. leukocyte

summary

Question

1. What kind of cells present in loose connective tissue? And what are the structure AND functions of those cells?

2.1.2 fibers

Collagenous fiber Elastic fiber Reticular fiber

①collagenous fiber (white fiber)

LM: 1-20 um in diameter Belt-liked wave and branch to form a network Eosinophilic

EM: parallel-arranged fibrilsFibril: 20-200nm in diameter Have periodic cross striation at 64nm interval

collagen (type I and III)

collagenous fibril

collagenous fiber

*formation of collagenous fibers:

② elastic fiber (yellow fiber)

LM: thinner and less, 0.2-1.0 um Slight red (HE) branch and form a networkEM: core: an amorphous substance--elastin-low electron density Peripheral: microfibril 10-12 nm, electron dense Function rubber-like properties

③reticular fiber

LM: thin and less,0.2-1.0 um in diameter Branch to form network black (silver impregnation method)---distribution: reticular tissue connecting portion, e.g.reticular lamina

2.1. 3 ground substance

---amorphous colloidal substance

---consists of proteoglycan, glycoprotein and tissue fluid

Function of the ground substance

Connection affect the differentiation and moveme

nt of cells a barrier to the penetration of foreign

particles

① Proteoglycan: mostly of Proteoglycans and Hyaluronic acid.

Molecular sieve:

•The entangled macro-molecular proteoglycan aggregate forms a bottle brush-like structure

•To exclude or entrap molecules of different sizes

•Serves as a physical barrier to prevent the spread of bacteria and other microorganisms.

② Glycoprotein Fibronectin Laminin chondronectin

③ tissue fluid

Arterial end→ Tissue fluid → venous end →blood steam oxygen, nutrients waste material, carbon dioxide cells

Acts as the midium for exchange of metabolites between circulating and tissue cells

Summary Loose connective Tissue3 fibers and 7 kinds of cells

2.2   Dense connective tissue

---Abundant fibers and few cells

---connection and supporting

Dense regular CT; Dense irregular CT;Elastic CT

2.2.1 regular DCT:

parallelly-arranged collagenous fibers tendon cells: /special fibroblast

/wing-liked processes

---distribution: Tendons Ligament Cornea

2.2.2 irregular DCT: Fiber arranged in bundles,runing in different d

irection Fibroblast less ground substance---distribution: dermis, sclera and capsule of so

me organs

2.2.3 Elastic Tissue: elastic fiber in bundles or in membran

e ligament and large artery

2.3 adipose tissue

---LCT+fat cells

---white fat T: single fat cell

---brown fat T: fat cell contain many small lipid droplets, rich in large mitochondria centrally-located nucleus

2.4     reticular tissue

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

The end