Download Loose connective tissue

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Histology
Dr.Ahmed_2015
Connective Tissues are responsible for providing and maintaining form
to the body. They function in a mechanical role, providing a matrix that
connects and binds the cells and organs and ultimately gives support to
the body.
Connective tissue composed of:C.T. fibers; C.T. cells; and Matrix
Function of C.T. The functions of the various types of C.T. are
generally depending on the types of cells, fibers, and the characters of the
ground substances in the matrix. The functions include the binding
together, support, and physical and immunologic protection of other
tissues and organs, as well as storage.
1 FIBERS OF CONNECTIVE
A. Collagen fibers
TISSUE PROPER
They provide strength, the more cartilage the stronger the tissue is.
It is demonstrated using the Masson & Gomori techniques and with
the Van Gieson stain. The only monosaccharide found in the
human body.
B. Elastic fibers
They are abundant in tissue that needs flexibility, as they allow tissue to
stretch. These fibers cannot usually be seen in H&E stains. Special stains
for these fibers are Verhoeff’s van Gieson, Weigerts Stain, or Gomori.
C. Reticular fibers
They have identified as a type of collagen. They may be demonstrated
with argyrophillic reactions, as they have the ability to absorb silver from
a solution. The silver may then be reduced to a metallic form.
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Histology
Dr.Ahmed_2015
Types of cells in C.T.
Fibroblasts – most common cells in connective tissue.
*Mesenchymal – these are primitive cells that may develop into
other differentiated cell types if the need arises for
replacement.
Adipose or Fat - these synthesize and store lipid and are more
common in most loose connective tissue.
Mast cells – contains abundant secretory granules. These
granules contain heparin & histamine and exhibit
metachromasia when stained with Toluidine Blue.
Macrophages – they are known as the “big eaters” or scavenger
cells that are found not only in connective tissue but in a
variety of other tissue as liver, myeloid, and lymphatic
tissue.
Plasma cells – they derive from B lymphocytes produce
immunoglobulins.
Blood cells – may be found in tissue.

Collagen
Collagen is the main protein of connective tissue. It has great tensile
strength, and is the main component of ligaments and tendons. It is
responsible for skin elasticity, and its degradation leads to wrinkles that
accompany aging. Collagen also fills out the cornea where it is present in
crystalline form.
Collagen is the most abundant protein in mammals.
Collagen has an unusual amino acid composition. It contains large
amounts of glycine and proline, as well as two amino acids that are not
inserted directly by ribosomes – hydroxyproline and hydroxylysine
Types of collagen
Collagen occurs in many places throughout the body, and occurs in
different forms known as types:
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Histology
Dr.Ahmed_2015
• Type I collagen - This is the most abundant collagen of the human
body. It is present in scar tissue, the end product when tissue heals
by repair. It is found in tendons and the organic part of bone.
• Type II collagen - Articular cartilage
• Type III collagen - This is the collagen of granulation tissue, and is
produced quickly by young fibroblasts before the tougher type I
collagen is synthesized.
• Type IV collagen - Basal lamina
• Type V collagen - most interstitial tissue, assoc. with type I
• Type VI collagen - most interstitial tissue, assoc. with type I
• Type VII collagen - epithelia
• Type VIII collagen - some endothelial cells
• Type IX collagen - cartilage, assoc. with type II
• Type X collagen - hypertrophic and mineralizing cartilage
• Type XI collagen - cartilage
• Type XII collagen - interacts with types I and III
Elastic
Elastic fibers are bundles of proteins (elastin) found in connective tissue
and 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.
Bundles are formed from covalent cross-linking between two amino
acids: desmosine and isodesmosine.
Reticular Fibers –
Reticular fibers are composed of type III collagen. - The fibrils are
branched, with a narrow diameter, and do not bundle to form thick fibers.
- Reticular fibers provide a supporting framework for cellular constitutes
of various organs.
- They are not stained by routine H&E stain, stained with Silver
technique, and they are PAS positive (contain sugar group) fibers.
- Reticular cells produce the collagen of reticular fibers in hemopoietic
and lymphatic tissues. - Fibroblasts produced reticular fibers in other
locations
The ground substance contains a variety of molecules secreted by CT
cells such as :- - Proteoglycans (aggrecan, syndecan) - Multiadhesive
glycoproteins (fibronectin, laminin). - Glycosaminoglycans (dermatan
sulfate, keratan sulfate, hyalronic acid).
Lec-3
Histology
Dr.Ahmed_2015
TYPES OF CONNECTIVE TISSUE
Loose connective tissue - delicate, flexible, not very resistant to stress, well
vascularized. All types of connective tissue cells present. Majority are
fibroblasts and macropahges. Collagen, elastic, and reticular fibers present. In
certain organs (intestine) and in certain disease conditions, numerous
lymphocytes may be present. Loose connective tissue also called areolar
tissue,suppots epithelium and organs.Its presentce in lungs,arteries,the urinary
bladder allaws these organs to expand and it protective many organs ,muscles
nerves ,blood vessels.The second type of loose connective tissue is adipose
tissue ,is a special type of losse connective tissue in which the cells enlarge and
storage fat.It has little extracellular matrix ,it stored energy,it also releases a
hormone called leptin which regulates appetite-control centers in the ,around the
kidney, an on the surface of heart.
Dense connective tissue - Clear predominance of collagen fibers at expense of
ground substance. Fewer cells than loose. Less flexible and more resistant to
stress.
Dense connective tissue found in tendons which connect muscles to bone and
ligament which connect bone to bone.
When collagen bundles are present without apparent orientation, called dense
irregular connective tissue.
When oriented in parallel arrays, called dense regular connective tissue.
Elastic tissue - bundles of thick, parallel elastic fibers. Small amount of loose
connective tissue around each bundle. Yellow color.
Reticular tissue - a specialized loose connective tissue with reticular cells that
form a fine matrix of reticular fibers. Provides a structural framework for
hematopoietic organs such as bone marrow and spleen.
Mucous tissue - a lot of amorphous ground substance composed mainly of
hyaluronic acid (glycosaminoglycan). Forms a jellylike tissue. Mainly
fibroblasts present. Found in umbilical cord and pulp of young teeth.
Adipose tissue - fat cells are connective tissue cells that are specialized for lipid
synthesis and storage. As they differentiate, these cells retract their cytoplasmic
processes and become spherical. This type of connective tissue is an exception
to the rule in that it does not have much “extra”cellular ground substance.
Lec-3
Histology
Dr.Ahmed_2015
Instead, these cells synthesize and store copious amounts of lipid. This means
that the bulk of the tissue is composed of lipid rather than cells. This is probably
the reason it is classed as a connective tissue. There are two types of adipose
tissue,
White adipose tissue - Composed of adipose cells, each with a single very large
droplet (unilocular) of lipid (mostly triglyceride) tat occupies nearly all the
volume of the cell. This lipid is a stored energy reserve that the body may call
on in times of need. The nulclei are always at the periphery of these cells.
Brown adipose tissue - each cell contains multiple droplets of lipid
(multilocular). The nuclei of these cells may be central with in the cell. Also
contain lipochrome pigments that cause the tissue to have a brown hue.
Widespread in fetus and young child. In adult humans it occurs in localized in
small areas,; however, it is abundant in animals that hibernate. Important in heat
production in the fetus, young child, and in hibernating animals.
Specialized connective tissue
1-Cartilage 2-Bone 3-Blood