Histology 1-31-07

Front 1

Collagen

Back 1

- flexible but strong
- wavy, eosin-staining structures
- TEM- bundles of fibrils with distinct banding
- collagen is synthesized in the ER (the initial process is inside the cell but the final assembly is outside of the cell)
- collagen is produced by fibroblasts

Front 2

Structure of collagen

Back 2

- every third amino acid is a glycine, and preceding that is either hydroxyproline or hydroxylysine
- there are 3 intertwined alpha helixes
- collagen is technically a glycoprotein
- carbohydrates are also associated with it
- the binding of one collagen to the next gives it its strength

Front 3

Main type of collagen

Back 3

- type I (makes up 90%)
- made of 2 of 1 alpha, 1 of 2 alpha

Front 4

Reticular Fibers

Back 4

- type III collagen fibers
- don't form thick fibers
- threadlike appearance
- mesh-like pattern
- epithelia/CT boundary in loose CT is found here
- reticular fibers are produced by reticular cells

Front 5

Elastin Fibers

Back 5

- thinner than collagen
- branching, 3D pattern
- 2 components:
1. elastin (bulk core)
2. fibrillin

- produced by fibroblasts (like collagen)
- microfibrils are made of fibrillin
- elastin fibers are found in: larynx, around arteries (allows them to stretch and contract), and ligaments of vertebral column

Front 6

Function of Elastin

Back 6

- has the ability to stretch
- has a highly coiled shape
- Desmosine and Isodesmosine= special amino acids in elastin (they play a key role in the connection between the elastin molecules)

Front 7

Marfan's Syndrome

Back 7

- elastin fibers don't function as properly
- there is a disruption in the gene of a particular fibrillin
- it is an autosomal dominant disease
- symptoms: elongated skeleton, higher flexibility, lung problems, scoliosis, arteries more prone to rupture
- famous victims: Ab Lincoln, etc.

Front 8

Extracellular Matrix

Back 8

- collagen
- noncollagen glycoproteins
- proteoglycans (ground substance)
- blood and lymphatic vessels

Front 9

Ground substance

Back 9

- fills in the space between fibers
- it is a viscous, clear substance
- high water content (hydrophilic)
- lost in preparation
- Composed of:
1. Glycosaminoglycans (GAGs)
2. Proteoglycans
3. Multiadhesive glycoproteins

Front 10

Proteoglycan structure

Back 10

- central core protein + GAGs
- the GAGs are highly charged so they draw in water
- hyaluronic acid

Front 11

Carcinoma invasion

Back 11

- it reduces the amount of cadherins
- it breaksdown plasma membrane by releasing enzymes (collagenase- breaks down collagen)
- it binds to integrins
- it promotes angiogenesis

Front 12

Cell types in CT

Back 12

Residents:
- fibroblasts and myofibroblasts
- macrophages
- mast cells
- undifferentiated mesenchyme

Transient:
- plasma cells
- basophils
- lymphocyte
- other immune cells (neurophils, eosinophils, monocytes)

Front 13

Fibroblasts

Back 13

- synthesize extracellular matrix
- only nucleus is typically visible
- produce and remodel collagen
- metabolically active
- help produce scar tissue
- the most abundant cells in CT
- fibrocytes are more spindle-shaped

Front 14

Myofibroblasts

Back 14

- have the ability to contract (like smooth muscle contraction)

Front 15

Macrophage

Back 15

- differentiate from monocytes
- difficult to ID
- numerous folds and lysosomes
- involved in defense (immune response)

Front 16

Mast cells

Back 16

- large, ovoid (20-30 um)
- numerous basophilic granules
- ID requires granules preserved
- located in vicinity of small blood vessels
- also involved in immune response

Front 17

Plasma Cells

Back 17

-regions of invasion
- produce antibodies
- cartwheel nucleus
- also involved in immune response