Transcript connective tissue introduction text

CONNECTIVE TISSUE
Without it you’d fall apart.
INTRODUCTION TO CONNECTIVE TISSUE
Connective tissue - a tissue, the major constituent of which is
extracellular matrix - material between the cells,
General:
ground substance - matrix found between cells of loose and
dense connective tissue
Specific types:
osteoid matrix - over 90% collagen type I embedded in a
ground substance of proteoglycans, condroitin, keratan and
hyaluronic acid. Mineralized with calcium phosphate as
hydroxyapatite [Ca5(PO4)3(OH)]
chondroid matrix - extracellular material between cartliage cells.
plasma - the fluid component of blood.
EXTRACELLULAR MATRIX OF CONNECTIVE TISSUE
The following molecules are found in the extracellular matrix of all types
of connective tissue and are major components of the organic matrix of
cartilage and bone,
1. glycosaminoglycans - polysaccharides formed of repeating
disaccharide sub-units composed of uronic acid and hexosamine
•Uronic acid is a hexose with the primary hydroxyl group oxidized
to form an acid.
•Hexosamine is a hexose with an amino acid attached.
Except for hyaluronic acid, glycosaminoglycans are bound to a
protein core to form proteoglycan molecules.
In combination with hyaluronic acid, proteoglycans can form
even larger molecules called proteoglycan aggregates.
In all of the above molecules, carbohydrate is the
predominant molecular component.
Hyaluronic acid
Uronic acid
Hexosamine
Disaccharide subunit
EXTRACELLULAR MATRIX OF CONNECTIVE TISSUE
2. glycoproteins - proteins with sugars attached where.
forms the major part of the molecule
Glycoproteins
The protein
10,000 - 700,000
Dalton - a mass unit that is used when describing the molecular weight of large
molecules such as proteins and proteoglycans. It is essentially equal to the mass
of a hydrogen atom (precisely 1.0000 on the atomic mass scale, a hydrogen
atom actually weighs a tad more)."
PROTEINECEOUS FIBERS FOUND IN CONNECTIVE TISSUE
Various proteineceous fibers are found within the extracellular
matrix of glyoproteins, glycosaminoglycans, and
proteoglycans. These include,
1. Collagen fibers
•Most abundant protein in human body. Molecules of
fibers are often oriented to form a sort of lattice. As a
result these fibers are birefringent.
•They are inelastic, but have great tensile strength. Thus
can be bent without breaking.
•Impart strength and flexibility to tissue.
•Collagen fibers often organized in a parallel array
forming a bundle.
•There are 5 types of collagen,
Types of collagen
•Type I - most common, found in every connective tissue.
microfibrils
http://anatgw.tiho-hannover.de/conntis/pcd_imgs/img0011.jpg
http://anatgw.tiho-hannover.de/conntis/ko1_bdgw.htm#TYP1
Forms tendons and
ligaments
http://www.unomaha.edu/~swick/2740connectivetissue.html
http://anatgw.tiho-hannover.de/conntis/pcd_imgs/img0048.jpg
Types of collagen
•Type II - found in hyaline and elastic cartilage and in the
vitreous body of eye.
•Type III - found in reticular fibers - healing wounds,
smooth muscle, fetal skin, support for cellular structure of
some organs such as the liver and spleen
•Type IV - found in the basal lamina of epithelia
•Type V - found in placental basal laminae, tendon, and
muscle sheaths.
PROTEINECEOUS FIBERS FOUND IN CONNECTIVE TISSUE
http://www.unomaha.edu/~swick/2740connectivetissue.html
2. Reticular fibers
a. Form network of fibers.
b. Stained black by silver salts
(agyrophilic).
c. High glycoprotein content making
them PAS-positive.
d. Contain collagen type III associated with glycoproteins,
proteoglycans and other types of collagen.
e. Abundant in smooth muscle and tissues of hematopoietic
organs.
f. Form a flexible network that strengthens the tissue structure of
these organs and supports the cells within.
Scanning EM - capillary
Reticular fibers are important in
anchoring small blood vessels to
surrounding tissue.
C - type I collagen fibers
RF - reticular fibers, type III
http://education.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab5/Examples/exretic.htm
Reticular fibers - type III collagen
Here “a whole-mount of a small blood vessel has been stained with silver. The thin black vertical
lines are reticular fibers running around the outside of the vessel like barrel hoops. The irregular
horizontal lines, running parallel to the length of the vessel are the silvered outlines of endothelial
cells.”
http://www.meddean.luc.edu/lumen/MedEd/Histo/frames/Histo02.html
Reticular fibers - type III collagen
http://www.vh.org/adult/provider/anatomy/MicroscopicAnatomy/Section03/Plate0338.html
“Silver stained smooth muscle of the intestinal wall. Top - inner circular layer, Bottom outer longitudinal layer. Reticular fibers stain black with a silver stain.”
2. Elastic fibers
•Form - broad, often wavy, diffusely stained bundles.
•These bundles branch and fuse with one and other to form network.
•Characteristically yellow in living tissue.
•The protein elastin is an important component - responsible for elasticity and yellow color.
•Stretch to 1 1/2 times unstretched length.
http://www.bu.edu/histology/p/00801ooa.htm
http://casweb.cas.ou.edu/pbell/Histology/Captions/Connective/2.areolar.html
http://www.siumed.edu/~dking2/intro/ct.htm#elastin
TYPES OF CELLS FOUND IN CONNECTIVE TISSUES
1. Fibroblasts
•Flattened, ovoid or stellate cells that have long, tapering,
branching processes.
•Actively involved in secretion of extracellular matrix (ground
substance) and in fiber formation, usually collagen.
•Associated with most connective tissues.
•Involved in wound healing, if absent, wound will not heal.
•Grow easily in tissue culture (too easily).
http://images.google.com/imgres?imgurl=http
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http://anatgw.tiho-hannover.de/conntis/ko1_bdgw.htm#FIBROGENESE
Fibroblasts
Rough ER for protein synthesis
http://www.meddean.luc.edu/lumen/MedEd/Histo/frames/h_frame4.html
2. Macrophages - many are present in loose connective tissue. Sometimes look
similar to fibroblasts; however, they are actively phagocytic. May be fixed in position
(histocytes, phagocytes) or wandering (this is usually what we think of as a
macrophage). Macrophages are derived from monocytes (white blood cells).
Distributed throughout
body.
Loose (areolar) connective tissue
•Magenta arrow - fibroblasts
•Green arrow - macrophages
•Blue arrow - collagen fiber
•Red/orange arrow - elastic fiber
http://www.faculty.une.edu/com/abell/histo/histolab2.htm
http://www.aids-info.ch/e_te/aas-e-imm.htm
3. Mesenchymal cells
•Form embryonic connective tissue cells.
•Resemble fibroblasts, but usually smaller, may have stellate appearance.
http://www.lumen.luc.edu/lumen/meded/Histo/HistoImages/hl2-01.jpg
•In adults (as well as children) they are often found aggregated along capillaries
where they are called pericytes (or perivascular cells). Differentiate to form new blood
vessels and connective tissue after injury.
•May differentiate into a number of connective tissue cell types when stimulated
by an appropriate inducing factor.
4. Reticular cells
•Form three-dimensional networks of cells that are in contact via long
processes.
Reticulum of lymph node
http://www.meddean.luc.edu/lumen/MedEd/Histo/frames/h_fram12.html
•Cellular network called a cellular reticulum - forms the supportive framework for
bone marrow, lymph nodes and the spleen.
•May be phagocytic.
•Form reticular fibers (type III collagen).
•Also may have a hemopoietic function as precursors for blood stem cells.
•Function in immune response.
5. Mast cells - contain large basophilic granules that are composed of a sulfated
glycosaminoglycan called heparin (anticoagulant), as well as other pharmacological agents such
as histamine (vasodilator). Important in allergic reactions.
http://www.meddean.luc.edu/lumen/MedEd/Histo/frames/h_frame4.html
6. Plasma cells - antibody producing B-lymphocytes. Other non-activated B-lymphocytes,
as well as T-lymphocytes may also be present in loose C.T. Identifying features - spokelike arrangement of the chromatin within the nucleus, in the case of plasma cells, a “large”
amount of cytoplasm associated with nucleus.
http://www.meddean.luc.edu/lumen/MedEd/Histo/frames/h_frame4.html
7. Adipose cells - unilocular (white),
multilocular ( brown) - lipid storage
http://www.unomaha.edu/~swick/2740connectivetissue.html
8. Leukocytes - white blood cells.
http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Blood/Blood.htm#Neutrophilic
9. Pigment cells (melanocytes) - have
shape similar to fibroblasts, but
cytoplasm contains melanin granules.
Originate from neural crest cells in
embryo.
http://education.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab14/EXAMPLES/Exmelano.htm
TYPES OF CONNECTIVE TISSUE
1. Loose or areolar connective tissue •Delicate, flexible, not very resistant to stress, well vascularized.
•All types of connective tissue cells may be present.
•Majority are fibroblasts; however many macrophages and/or lymphocytes
may be present.
•Collagen, elastic, and reticular fibers present.
Relatively many cells and
“few” fibers in substantial
ground substance.
http://www.drbio.cornell.edu/Infrastructure/MPM_WWW/MPM_hist/loose.htm
TYPES OF CONNECTIVE TISSUE
2. Dense connective tissue - Clear predominance of collagen fibers at
expense of ground substance. Fewer cells than loose connective
tissue. Less flexible and more resistant to stress.
•When cells and collagen fibers are oriented in a
parallel array - dense regular connective tissue.
Relatively few cells and many fibers in
little ground substance.
http://www.unomaha.edu/~swick/2740connectivetissue.html
http://www.pathguy.com/histo/052.htm
•When collagen bundles are present without apparent
orientation, called dense irregular connective tissue.
TYPES OF CONNECTIVE TISSUE
3. Elastic tissue - bundles of thick, parallel elastic fibers. Small amount of
loose connective tissue around each bundle. Yellow color.
http://www.unomaha.edu/~swick/2740connectivetissue.html
Elastic connective tissue - aorta
elastic fibers - elastin
Reticular connective tissue - spleen
reticular fibers - Type III collagen
4. 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.
TYPES OF CONNECTIVE TISSUE
5. 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 (Wharton’s jelly) and
pulp of young teeth.
Umbilical cord
Dental pulp
http://anatgw.tiho-hannover.de/conntis/gal_bdgw.htm
http://www.kumc.edu/instruction/medicine/anatomy/histoweb/ct/ct15.htm
TYPES OF CONNECTIVE TISSUE
6. Adipose tissue •Specialized for lipid synthesis and storage.
•As lipid accumulates, these cells retract their cytoplasmic processes
and become spherical.
Two types of adipose tissue.
•White adipose tissue - adult adipose tissue. Composed of
adipose cells, each with a single large droplet (unilocular) of lipid
(mostly triglyceride).
http://www.unomaha.edu/~swick/2740connectivetissue.html
TYPES OF CONNECTIVE TISSUE
Brown adipose tissue
•Each cell contains multiple droplets of lipid (multilocular).
http://www.vivo.colostate.edu/hbooks/pathphys/misc_topics/brownfat.html
http://anatgw.tiho-hannover.de/bdgw/pcd_imgs/img0074.jpg
•Contain lipochrome pigments - gives living tissue a brown hue.
•Widespread in fetus and young child.
•In adults localized in small areas, abundant in animals that hibernate.
•Important in heat production for fetus, young child, hibernating animals.
TYPES OF CONNECTIVE TISSUE
•Bone - discussed in next lecture.
•Cartilage - discussed in next lecture