H/E Lecture 13 Flashcards
What is ground substance made of?
Glycosaminoglycans
Proteoglycans
Proteoglycan aggregates
Multiadhesive glycoproteins
What are GAGs?
Glycosaminoglycans
They repeating disaccharide units, most are sulfated and negatively charged.
What are proteoglycans?
Made up of a core protein and branches that are made of GAGs that add a negative charge to PGs. These form further branched molecules with linker proteins and hyaluronan to for PG Aggregates.
What is the purpose of PG Aggregates?
They hold water which is necessary for the function of cells, and provides shock absorption. These are present in all general CTs.
How do GAGs and PGs stain?
Both are negatively charged, so they stain with basic dyes. They are blue in H&E and magenta in PAS because GAGs are carbohydrates.
What are multiadhesive glycoproteins?
These are a variety of proteins that help stabilize the ECM and they link the ECM to CT cells. The proteins involved are fibronectin, laminin, tenascin, osteopontin, entactin/nidogen.
Features of elastic fibers and how to identify them.
Thinner than collagen fibers
Often branches (collagen fibers do not branch)
Look like rubber bands that have recoiled
Blunt and broken looking ends
Found in dermis, large blood vessels, lungs
Stain dark brown/black with Orcein
Stains same as collagen with Eosin (pink)
Made of elastin core and fibrillin microfibrils
What cells make collagen and what are the three major groups of collagen?
Made by: fibroblasts, epithelial cells, smooth muscle, schwann cells
- Fibrillar (I, II, III)
- Sheet forming (IV)
- Anchoring (VII)
What is periodicity in regard to collagen fibers?
Collagen fibrils have light and dark stripes on them that repeat over and over. These come from the way tropocollagen fibers form into fibrils.
What are the features of type I collagen?
Only type that bundles, used for tensile strength
Stains with trichrome and H&E
Most widely found type, dermis, bone, ligaments, tendons, joint capsules, investments of muscles and nerves, sclera of eye, scar tissue
Tends to appear white
Features of type II collagen?
Makes up cartilage
Used for tensile strength and restrains PG aggregates expansion
Stain slightly pink in H&E, but high concentrations of PG stain blue and mask the pink
Does not bundle into fiber bundles
Features of type III collagen?
Remain as fibrils only
First type of collagen laid down in embryo and in injury as adults
Heavily glycosylated
Seldom visible with H&E, stains black with silver, could use PAS because heavily glycosylated
Surround adipocytes, smooth muscle, peripheral nerve, small blood and lymph vessels
Looks like chicken wire, provides support for organs that filter blood or lymph (spleen, lymph), have rich vasculature (liver GI, endocrine), or rapidly proliferating cells (bone marrow)
Large part of the reticular lamina
Features of type IV collagen?
Does not form fibrils and thus doesn’t have periodicity
Makes sheets that make up the basal lamina adn external lamina in muscle and nerve
Provides support and anchoring for the epithelium and filtration
Features of type VII collagen?
Anchoring collagen
non-fibrillar
anchors basal lamina to reticular lamina
What is Ehlers-Danlos type IV?
Problem with type III collagen
Hypermobility of joints of digits, pale thin skin, severe bruisability, early morbidity and mortality from rupture of vessels and organs
