CONNECTIVE TISSUE

Without it you’d fall apart.

INTRODUCTION TO CONNECTIVE TISSUE

Connective tissue - a tissue, the major constituent of which is

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)]

plasma - the fluid component of blood.

chondroid matrix - extracellular material between cartliage cells.

General:

ground substance - matrix found between cells of loose and dense connective tissue

extracellular matrix - material between the cells,

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.

EXTRACELLULAR MATRIX OF CONNECTIVE TISSUE

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.

Uronic acid

Hexosamine

Hyaluronic acid

Disaccharide subunit

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)."

EXTRACELLULAR MATRIX OF CONNECTIVE TISSUE

Glycoproteins 10,000 - 700,000

2. glycoproteins - proteins with sugars attached where. The protein forms the major part of the molecule

Various proteineceous fibers are found within the extracellular matrix of glyoproteins, glycosaminoglycans, and proteoglycans. These include,

1. Collagen fibers

PROTEINECEOUS FIBERS FOUND IN CONNECTIVE TISSUE

•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,

http://anatgw.tiho-hannover.de/conntis/ko1_bdgw.htm#TYP1http://anatgw.tiho-hannover.de/conntis/pcd_imgs/img0011.jpg

microfibrils

http://anatgw.tiho-hannover.de/conntis/pcd_imgs/img0048.jpghttp://www.unomaha.edu/~swick/2740connectivetissue.html

•Type I - most common, found in every connective tissue.

Types of collagen

Forms tendons and ligaments

•Type II - found in hyaline and elastic cartilage and in the vitreous body of eye.

•Type IV - found in the basal lamina of epithelia

•Type V - found in placental basal laminae, tendon, and muscle sheaths.

•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

Types of collagen

PROTEINECEOUS FIBERS FOUND IN CONNECTIVE TISSUE

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.

http://www.unomaha.edu/~swick/2740connectivetissue.html

http://education.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab5/Examples/exretic.htm

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

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

http://www.vh.org/adult/provider/anatomy/MicroscopicAnatomy/Section03/Plate0338.html

Reticular fibers - type III collagen

“Silver stained smooth muscle of the intestinal wall. Top - inner circular layer, Bottom - outer longitudinal layer. Reticular fibers stain black with a silver stain.”

http://www.bu.edu/histology/p/00801ooa.htm

http://casweb.cas.ou.edu/pbell/Histology/Captions/Connective/2.areolar.html

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.siumed.edu/~dking2/intro/ct.htm#elastin

TYPES OF CELLS FOUND IN CONNECTIVE TISSUES1. Fibroblasts

•Flattened, ovoid or stellate cells that have long, tapering, branching processes.

•Associated with most connective tissues.

•Involved in wound healing, if absent, wound will not heal.

•Grow easily in tissue culture (too easily).

•Actively involved in secretion of extracellular matrix (ground substance) and in fiber formation, usually collagen.

http://anatgw.tiho-hannover.de/conntis/ko1_bdgw.htm#FIBROGENESE

http://images.google.com/imgres?imgurl=http://www.mediastorehouse.com/image/fibroblast-cells_1698357.jpg&imgrefurl=http://www.mediastorehouse.com/pictures_1698357/fibroblast-cells.html&usg=__8YkQowrFHt87N-HNrgZwbd9ZN8A=&h=447&w=450&sz=122&hl=en&start=41&um=1&tbnid=ZT6NciXUY9evTM:&tbnh=126&tbnw=127&prev=/images%3Fq%3Dfibroblast%2Bpicture%26ndsp%3D21%26hl%3Den%26client%3Dsafari%26rls%3Den%26sa%3DN%26start%3D21%26um%3D1

http://www.meddean.luc.edu/lumen/MedEd/Histo/frames/h_frame4.html

Fibroblasts

Rough ER for protein synthesis

http://www.faculty.une.edu/com/abell/histo/histolab2.htm

http://www.aids-info.ch/e_te/aas-e-imm.htm

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).

Loose (areolar) connective tissue

•Magenta arrow - fibroblasts

•Green arrow - macrophages

•Blue arrow - collagen fiber

•Red/orange arrow - elastic fiber

Distributed throughout body.

http://www.lumen.luc.edu/lumen/meded/Histo/HistoImages/hl2-01.jpg

3. Mesenchymal cells

•Resemble fibroblasts, but usually smaller, may have stellate appearance.

•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.

•Form embryonic connective tissue cells.

http://www.meddean.luc.edu/lumen/MedEd/Histo/frames/h_fram12.html

4. Reticular cells

•Form three-dimensional networks of cells that are in contact via long processes.

Reticulum of lymph node

•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.

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 - spoke-like 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

http://www.meddean.luc.edu/lumen/MedEd/Histo/frames/h_frame4.html

http://www.unomaha.edu/~swick/2740connectivetissue.html

http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Blood/Blood.htm#Neutrophilic

7. Adipose cells - unilocular (white), multilocular ( brown) - lipid storage

8. Leukocytes - white blood cells.

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

http://www.drbio.cornell.edu/Infrastructure/MPM_WWW/MPM_hist/loose.htm

TYPES OF CONNECTIVE TISSUE1. Loose or areolar connective tissue -

•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.

•Delicate, flexible, not very resistant to stress, well vascularized.

Relatively many cells and “few” fibers in substantial ground substance.

http://www.unomaha.edu/~swick/2740connectivetissue.html http://www.pathguy.com/histo/052.htm

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.

•When collagen bundles are present without apparent orientation, called dense irregular connective tissue.

Relatively few cells and many fibers in little ground substance.

TYPES OF CONNECTIVE TISSUE

http://www.unomaha.edu/~swick/2740connectivetissue.html

3. Elastic tissue - bundles of thick, parallel elastic fibers. Small amount of loose connective tissue around each bundle. Yellow color.

Elastic connective tissue - aorta

elastic fibers - elastin

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.

Reticular connective tissue - spleenreticular fibers - Type III collagen

TYPES OF CONNECTIVE TISSUE

TYPES OF CONNECTIVE TISSUE5. 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

http://www.unomaha.edu/~swick/2740connectivetissue.html

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).

TYPES OF CONNECTIVE TISSUE

http://anatgw.tiho-hannover.de/bdgw/pcd_imgs/img0074.jpg

Brown adipose tissue

•Each cell contains multiple droplets of lipid (multilocular).

•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

http://www.vivo.colostate.edu/hbooks/pathphys/misc_topics/brownfat.html

TYPES OF CONNECTIVE TISSUE

•Bone - discussed in next lecture.

•Cartilage - discussed in next lecture