IntroductionDEFINITION

It is one of the four general classes of animal tissues- as well as epithelial, muscle and nervous tissues.

Is a kind of animal tissue that connects, supports, binds, or separates other tissues or organs of the body.

It is the most diverse tissue and is found throughout the body

Unlike epithelial tissue, connective tissue has relatively little intimate contact between the cells that make up part of its structure

Function:

1. Storage of energy

2. Protection of organs

3. Provision of structural framework for the

body

4. Connection of body tissues

5. Connection of epithelial tissues to muscle

fiber.

6. Transportation of fluids and dissolved

substances

7. Defend the body against microorganisms

8. Repair of body tissue

Structurally, connective tissue  is made up of cells and extracellular matrix. The extracellular matrix is made up of protein fibers in and polysaccharide matrix, secreted and organized by cells in the extracellular matrix. Variations in the composition of the extracellular matrix, determines the properties of the connective tissue. For example, if the matrix is calcified, it can form bone or teeth.

Structure of Connective tissue

Cells are spread through an extracellular fluid.Ground substance - A clear, colorless, and viscous fluid containing glycosaminoglycans and proteoglycans to fix the body water and the collagen fibers in the intercellular spaces, fills the space between the cells and contains the fibers.Ground substance slows the spread of pathogens.Fibers. Not all types of CT are fibrous. Examples of non-fibrous CT include adipose tissue and blood.

Characteristics of Connective tissue

CELLS OF CONNECTIVE TISSUE

A variety of cells with different origins

and functions are present in connective

tissue

1) Fibroblasts

2) mast cells

3) macrophages

4) plasma cells

5) Adiposities cells

Macrophage

Fibroblast

Lymphocyte

Fat cell

Mast cell

Neutrophil

Capillary

Cell types Extracellularmatrix

Fibers• Collagen fiber• Elastic fiber• Reticular fiber

Ground substance

CELLS OF CONNECTIVE TISSUEOrigin of cells :

Fibroblasts originate from : undifferentiated mesenchymal cells spend all their life in connective tissuemast cells, macrophages, and plasma cells

originate from: hematopoietic stem cells in bone marrow These are all types of Immune cell. circulate in the blood, and then move into

connective tissue where they remain and execute their functions.

1.Fibroblasts They are mainly responsible for secreting the

non-rigid extracellular matrix including the fibers collagen, elastin or fibronectin.

Two stages of activity:o active fibroblastso inactive fibroblasts.

Cells with synthetic activity are morphologically distinct from inactive fibroblasts that are scattered within the matrix they have already synthesized.

CELLS OF CONNECTIVE TISSUE

Active fibroblast Large, euchromatic, oval nucleus

Cytoplasm not usually visible but contains

abundant rough endoplasmic reticulum and

Golgi apparatus

Elongated, spindle-shaped cells

High synthetic activity

CELLS OF CONNECTIVE TISSUE

Active fibroblast

Inactive fibroblast

Small, heterochromatic, flattened

nucleus.

Reduced cytoplasm and organelles.

Low synthetic activity.

CELLS OF CONNECTIVE TISSUE

2.Macrophages Derived from blood monocytes Are large cells with more cytoplasm than

lymphocytes or plasma cells. They have no granules and function to ingest

other cells and bacteria by phagocytosis, antigen processing, and cytokine secretion.

Enter connective tissue from the bloodstream and rapidly transform into macrophages

CELLS OF CONNECTIVE TISSUE

3.Mast cells releasing immune modulators from

cytoplasmic granules, in response to

antigen binding with cell surface antibodies.

Mast cells secrete histamine, heparin and

other factors.

They are important in the uptake of fatty

acids from the blood into fat cells.

CELLS OF CONNECTIVE TISSUE

4.Plasma cellsSecrete antibodies to provide humeral

immunity

Derived from B-lymphocytes take up

residence in lymph nodes, bone marrow, and

loose connective tissue where they synthesize

and secrete specific antibodies.

CELLS OF CONNECTIVE TISSUE

5. Adipose cells

Adipocytes are connective tissue cells that

have become specialized for storage of neutral

fats or for the production of heat.

CELLS OF CONNECTIVE TISSUE

EXTRACELLULAR MATRIX

2. Fibers:

Collagen fibers

Reticular fibers

Elastic fibers

Collagen is the most common protein found in the human body. It is found in almost all organs and body parts. In general, collagen winds itself into a fiber mesh that adds structural stability to that specific body part.It is commonly associated with skin integrity, but is critical for proper function of many other body parts, too.At least 12 types of collagen exist, four of which are commonly found in different body parts. Type I collagen is the most abundant type

collagen fiber

 composed of type III collagen secreted by reticular cells.Reticular fibers crosslink to form a fine meshwork (reticulin). This network acts as a supporting mesh in soft tissues such as liver, bone marrow, and the tissues and organs of the lymphatic system.

Reticular fiber

Elastic fiber

 are bundles of proteins (elastin) found in extracellular matrix of connective tissue  produced by fibroblasts and smooth muscle cells in arteries. These fibers can stretch up to 1.5 times their length, and snap back to their original length when relaxed.Elastic fibers include elastin, elaunin and oxytalan.

EXTRACELLULAR MATRIX

3. Ground substances

It is a jelly like substance having proteins and

sugars, in bone the ground substance

include minerals and in blood the ground

substance is the plasma

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