Mrs. Dalia Kamal Eldien
MSC in Microbiology
Lecture NO 3
Objectives
Definition of connective tissue
Function of connective tissue
Structure of connective tissue
Characteristics of connective tissue
Cells of connective tissue
Extra cellular matrix
Introduction
DEFINITION
 It is one of the four general classes of animal tissuesas 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
Structure of connective 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.
Characteristics 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.
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
Cell types
Macrophage
Extracellular
matrix
Ground substance
Fibers
• Collagen fiber
• Elastic fiber
• Reticular fiber
Fibroblast
Lymphocyte
Fat cell
Mast cell
Neutrophil
Capillary
Cells of connective tissue
Origin of cells :
Fibroblasts :
 Originate from undifferentiated mesenchymal cells
 spend all their life in connective tissue
mast 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.
Cells of connective tissue
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 fibroblasts
o 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
Active fibroblast
Cells of connective tissue
Inactive fibroblast
 Small, heterochromatic, flattened nucleus.
 Reduced cytoplasm and organelles.
 Low synthetic activity.
Cells of connective tissue
2.Macrophages
 Derived from blood monocytes
 Enter connective tissue from the bloodstream and
rapidly transform into macrophages
 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.
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 cells
Secrete 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.
Extracellular matrix
2. Fibers:
 Collagen fibers
 Reticular fibers
 Elastic fibers
Collagen fiber
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
Reticular 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.
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