Fibrous Connective tissue (My notes) Flashcards
What are connective tissues?
Connective tissues are supportive as they anchor organs and join the other body tissues into a structurally integrated whole
What is the general composition of connective tissues?
Few cells and Extracellular (intercellular) Matrix
What makes up the extracellular matrix?
Collagen protein fibers
Ground substance
Other supporting biochemicals (structural glycoproteins)
Are connective tissues vascularized?
May be vascularized or avascular (cartilage)
Functions of connective tisssue?
- Binding and support ie Ligaments
- Defense ie macrophages, lymphocytes, mast cells of different tissues
- Storage ie adipose tissue
- Protection ie. adipose tissue
- Transport or materials between blood and other tissues
What is ground substance?
Amorphous (without shape), gel-like material
Composed of charged glycosaminoglycans (GAGs)- mucopolysaccharides (polymers of disaccharide subunits) and proteoglycans- mucoproteins
Why is ground substance particularly important?
Aids in the transport of nutrients and waste, due to their component charges they are hydrophilic they can mix with tissue fluid readily.
For instance, substances from tissues can be transported into the blood.
What are the components of ex
What are structural glycoproteins?
Glycoproteins are involved in anchoring and fastening cells to extracellular material, including the basement membrane
What are the two types of fibers present in the connective tissue?
Collagen
Elastic
What is a collagen molecule?
Protein that has three alpha-helical chains would be in a triple helix
Before being active it is called tropocollagen which is a form of collagen that needs to be cleaved in order to be active.
What is a collagen fiber?
Many collagen molecules packed together into a repeating pattern via crosslinking
What is the most abundant type of collagen?
Type I
High tensile strength and flexible, but inelastic
What collagen fibers form the framework for the liver, lymphatic tissue and bone marrow?
Type III collagen fibers
Thin, branched reticular fibers
What are elastic fibers made of?
Elastin (protein)
Fibrillin (glycoprotein→ regulates deposition of elastin)
Where are elastic fibers most important?
The elasticity is important in organs that can be deformed and return to their shape (skin & larger arteries)
Name the types of cells present in adult fibrous connective tissues?
FLAP MoM
Fibroblasts
Mast cells
Macrophages
Adipocytes
Lymphocytes
Plasma cells
What are the two types of Embryonic connective tissues?
Mesenchyme
Mucous (Wharton’s Jelly)
What is mesenchyme?
- Primitive connective tissue with few fibers that form a loose mesh of rudimentary connective tissue.
- Contains spindle shaped cells with potential to develop into various specialized connective tissue cells
- Derived from the mesoderm
What role do mesenchymal cells play in adults?
They play a role in tissue repair
What is muscous tissue?
Embryonic connective tissue found only in the umbilical cord and a few locations in the embryo
Contains fibroblasts and very few collagen fibers coursing through a jelly-like ground substance in the umbilical cord called Wharton’s jelly
What are fibroblasts?
Derived from mesenchymal cells
Responsible for making and maintaining the matrix as they are capable of producing all the components of the ECM
Cells with elongated extensions
What are macrophages?
Derivatives of monocytes which have left circulation and entered the tissue.
What is the function of macrophages?
Engulf foreign or dead cells and debris and present antigens to lymphocytes in the immune responses.
What are resident (fixed) macrophages?
Regular inhabitants of a particular tissue
Stay in particular tissue
What are elicited (wandering/free) macrophages?
They circulate the blood, migrate and enter the tissues where they are needed
What are Mast cells?
Cells that originate in the bone marrow, but occupy connective tissues
Larg with prominant cytoplasmic membrane-bound granules containing histamine and/or other chemicals involved in the inflammatory response
What are adipocytes?
Derived from mesenchymal cells and fibroblasts (maybe)
Cells specialized to store fat
What are unilocular fat cells?
These cells store fat as a single, large droplet that pushes the nucleus and cytoplasm to the edge of the cell
What are multilocular fat cells?
These cells are smaller and have a spherical nucleus.
Fat is stored in many droplets
What are leukocytes?
These are white blood cells of which various types can be seen at the site of an infection or inflammation
How do lymphocytes show on a slide?
Dark staining nucleus surrounded by a thin layer of cytoplasm like a halo of cytoplasm
How do plasma cells look when stained?
Larger (may be ovular) with purplish cytoplasm and eccentric nucleus
How do neutrophils look when stained?
Segmented lobed nucleus with granular cytoplasm
What is loose areolar tissue?
This is connective tissue that looks like a spider web but with all the spaces it allows for blood vessels, lymphatic vessels, collagen, elastic fibers, fibroblasts, mast cells, macrophages and other connective cells to pass through there.
Where is loose areolar tissue found?
filler between muscles, between muscles and skin, other locations
What is dense regular connective tisuuses?
Collagen fibers are arranged in bundles and they all go in one direction
Poorly vascularized
Fiber arrangement allows tensile strength along the length
What kind of cells are compressed and appear elongated in dense regular connective tissue?
Fibroblasts
What is an example of dense regular connective tissue?
Tendons
Wha tis dense irregular connective tissue?
Densely packed collagen bundles arranged in all directions
Vascularized
What is the predominant cell type in dense irregular connective tissue?
FIBROBLASTS
Where can dense irregular connective tissue be found?
Dermis and capsules of many organs
What are the two types of adipose tissue?
White adipose tissue
Brown adipose tissue
What does a cell name ending in “blasts” indicate?
The cell is maturing and producing the components of the matrix
What does a cell name ending in “cyte” indicate?
The cell is mature and is maintaining the matrix that was secreted.
What makes the negative charge in ground substance so important?
The negatively charged side groups in terms of carboxyl, hydroxyl and sulfate groups have negative charges which will attract water to the matrix allowing for the maintenance of the gel-like state.
The negative charge also attracts cations which can draw in H2O.
What groups are attached to proteoglycans?
Sulfate groups
Chondroitin-4-sulfate
Chondroitin-6-silfate
Dermatan sulfate
Heparan sulfate
Keratan sulfate
What group is not associated with Hyaluronic acid?
Sulfate groups
What are the most common types of collagen in supporting tissues?
Type 1 (High tensile → dermis, tendon, ligament, bone)
Type 2 (Hyaline cartilage at end of bone)
Type 3 ( reticulin → branched fibers in liver, bone marrow and lymphoid organs)
Type 4 (meshwork in basement membranes)
Type 7 (anchoring fibrils in basement membrane)
What is elastin?
This is a substance secreted by fibroblasts in the form of tropoelastin.
It provides extensibility and elasticity to connective tissues encountered in lungs, dermis, and blood vessels
What is fibronectin and what does it do?
Structural glycoprotein
Regulates the deposition and orientation of the collagen fibers by binding to collagen
Forms a link between the cytoskeleton and extracellular matrix by binding to integrin which is an integral protein that is bound to the cytoskeleton at its cytoplasmic end.
What are the two fibril-forming molecules?
Fibrillin (elastin deposition)
Fibronectin (collagen deposition)
What are the two non-fibrillary proteins that form links between cells and the extracellular matrix?
Laminin
Entactin
Tenascin
What is Laminin?
This is part of the basement membrane present at the base of all organs that anchor cells to the basement membrane
It is a hemidesmosome
What is Entactin?
This is a protein that binds laminin to type 4 collagen in the basement membrane
What is tenascin?
This is a non-fibrillary protein that binds to integrins and promotes nerve cell growth and development in embryos
What is the basement membrane?
A protein matrix that goes between supporting and parenchymal cells of other tissues such as epithelium, muscle or nerve
What is the basement membrane called in muscle and nerve tissue?
External lamina
What are the three layers of the BM?
Lamina lucida (Type 4 collagens)
Lamina densa (thickest layer)
Lamina fibroreticularis (type 3 collagens)
What is the lamina lucida?
This is the thin part of the BM which contains very few fibers so it appears almost clear.
This is right under the epithelial cells and the laminin anchors the type 4 collagen that makes it up
What is lamina densa in the BM?
Second and thickest layer that stains very dark
It contains collagen bound to heparan sulfate which is a glycosaminoglycan that anchors collagen fibers
What is the lamina fibroreticularis?
Looks almost continuous with the connective tissue and it contains type 3 collagen which secretes reticular fibers
Connects the epithelium with the connective tissue
