block III: CT video 1 Flashcards
Which tissues does connective tissue serve to connect?
epithelium, muscle and nerve
What are the adult types of Connective tissue?
Connective tissue proper (major type)
Specialized connective tissue
What are the embryonic types of Connective tissue?
Messenchymal CT (mesodermal organs)
Mucoid CT (found in umbilical cord)
Which is the general diffuse type of connective tissue found all through out the body connecting together the other tissues
Connective tissue proper
Which are the specialized connective tissues?
- Reticular connective tissue (Lymphatic and blood forming organs)
- Adipose tissue (fat)
- Cartilage
- Bone
- Blood
Where are most types of CT derived from?
undifferentiated mesenchymal cells of
the embryonic mesoderm (some CT comes from neural crest [from CT of head[)
What characterizes CT histologically in basic characteristics?
presence of cells which are typically widely
separated from each other by extensive
regions of an extracellular matrix
which typically consists of several types of
fibers and a ground substance.
Identify
mesentery spread as an example of
connective tissue
Identify
Micrograph of epithelium in small intestine showing tight spacing of epithelial cells with only small amounts of extracellular matrix
Identify
Micrograph of connective tissue in submucosa of small intestine
showing CT cells widely separated with extracellular space with
fibers and ground substance
What are some functions of CT?
- connect together & strengthen the other tissues
- provide a diffusional pathway for the movement of ions, molecules,
and metabolites to the other tissues. (Blood vessels typically run in the connective tissue) - immunological defense (immunocompetent cells are typically present. In addition connective tissue acts as a physical barrier to microbes)
- wound healing (scar formation)
What are the types of fibers in CT?
- Collagen fibers
- Reticular fibers
- Elastic fibers
identify
Micrograph of a mesentery spread showing stained collagen and elastic fibers as well as CT cells
What is the size and stain of collagen fibers?
- 2-30 microns (largest within CT proper)
- Stain with eosin in H&E preps
What are collagen fibers composed of and how do they look in electron microscope?
- collagen fibrils
- collagen fibrils are composed of collagen and show distinct 68nm cross striation in EM
Functions of collagen fibers
They have extreme tensile strength and depending on the numbers and arrangement they add mechanical strength to surrounding tissues [compared to steel, resist pulling forces]
identify
Micrograph of submucosa of small intestine showing collagen fibers
stained with H&E
identify
EM showing collagen fibers composed of bundles of collagen fibrils, and a fibroblast cell
identify
EM of collagen fibrils in dense irregular CT with and inset showing the cross-banding
structure of the fibrils (striated pattern) [distinct 68nm repeat]
identify
Collagen Type I fibrils as seen in atomic
force microscope image. Note the striations [distinct 68nm repeat]
WHat is the size of reticular fibers and its stain?
- about 1.5 microns in diameter
- not typically seen in routine H&E. Stained with silver metal containing stains
What is the arrangement of reticular fibers?
arranged in a delicate meshwork or network of fibrils, rather than the large
bundles seen in collagen fibers
Functions of reticular fibers
surround small blood vessels, small nerves, fat cells, and form the CT
framework of liver & most lymphoid and blood-forming tissues.
identify
reticular fibers
What is the structure of collagen?
linear molecule 1.5 nm diameter by 300nm length composed of three helically arranged polypeptide chains.
What is present in the helical regions of collagen?
glycine, every third residue
WHta is the percetange of hydroxyproline and hydroxylysine?
10% hydroxyproline
10% hydroxylysine
Why are hydroxyproline residues important?
important in forming hydrogen bonds
between the polypeptides and
stabilize the triple helical structure
Why is hydroxylysine important?
important for forming crosslinks between adjacent collagen molecules in the fibril. An enzyme lysl oxidase is required.
WHat cofactors are important for hydroxylation reactions?
Vitamin c and iron; Thus diets including a
source of vitamin C (fruits and
vegetables) and iron (meat for
example) are important for proper
collagen synthesis.
Where does the formation of the triple helical procollagen molecule occur?
RER of cytoplasm
What final step forms collagen and where does it occur?
final clipping of the non-helical
ends of molecule assembly of the molecules to form the fibril or other arrangements of collagen; occurs extracellularly in association with indentations (coves) of the fibroblast cell surface
How many types of collagen are there and which are the most important?
28 types, 4 are most important:
1. Type I
2. Type II
3. Type III
4. type IV
Where is collagen type I found?
In dermis, bone, tendons, fibrocartilage, dentin, most organ capsules. Type found in collagen fibers (90% of collagen in body)
Where is collagen type II found?
Found in all cartilages. (Fibrocartilage contains both Type II and Type I)
Where is collagen type III found?
Found associated with blood vessels, nerves, lymphatic and blood forming tissues, the liver, lung. Type of collagen associated with reticular fibers
Where is collagen type IV found?
Associated with basement membranes (non-fibrillar) [blood brain barrier]
identify type of collagen present
Collagen Type I fibers in submucosal layer of small intestine
identify type of collagen present
Hyaline cartilage containing Type II
collagen
identify type of collagen present
Reticular fibers with Type III collagen stained with silver in lymph node
What collagen is found in type I fibrils? What are they associated with?
Type V, XI, XII & XIV
Type V associates with surface of Type I collagen fibrils and type XI forms the initial core of the type I fibril. Small amounts of Type III may also be found
Types XII & XIV also attach to Type I fibrils and play a role in their 3D arrangement in CT
What collagen is found in Type II fibrils? What are they associated with?
Collagen type IX, Associated with the surface of type II collagen fibrils forms links to other
extra-cellular molecules
