| What are the layers of basement membrane? | Lamina rara or lucida (clear, electron lucent)
Lamina densa (middle, wide and electron dense, main layer of basal lamina)
Lamina reticularis (AKA par fibroreticularis very clear represents junction between lamina densa and underlying CT secreted by cells of CT type III collagen) |
| How are the first two layers of basement membrane synthesized? | By cells that they rest on, from type IV collagen, proteoglycans, and glycoproteins. (laminin, fibronectin) |
| Talk about non-specialized connective tissus. | AKA proper, common or classic, characterized by presence of cells (fixed or wandering) and a very abundant ECM (ground substances, fibers, structural glycoproteins) originate from mesenchyme. |
| How are non-specialized cells? | non polar divided into two categories wandering and fixed cells. |
| How are fixed non-specialized cells? | non-motile consist mainly of fibroblast (and adipocytes) |
| What are fibroblasts? | principal and least specialized connective cell, compared to others, originate from the mesenchyme. |
| Describe the fibroblast? | spindle shaped cells with long cytoplasmic processes (extensions) and lack a basement membrane. their size varies according to the activity level. significant mitotic activity. basophilic cytoplasm nucleus is central ovoid large and elongated with one or two nuecleoles, active fibroblasts contain abundant organelles involved in protein synthesis cytoskeleton is well developed and formed of actin filaments. |
| What roles do fibroblast have? | Control and maintain ECM (synthesis and secretion of macromolecules of ECM/ produce enzymes for catabolism of these macromolecules.)
Tissue repair |
| What happens when fibroblasts deactivate? | nucleus condenses, cytoplasm loses basophilic characteristics absence of any genetic activity, it becomes a fibrocyte. |
| Talk about wandering non-specialized cells. | move actively, presence is variable and occasional, cells of the immune system, reach CT through bloodstream by crossing capillary barriers through diapedesis. (lymphocytes, granulocytes, monocytes..) |
| What is the ECM of non-specialized connective tissues? | composed of amorphous ground substance, fibrous proteins and glycoproteins, very abundant. |
| What are ground substances? | Highly hydrated gel-like material, implicated in the diffusion of molecules between cells and blood, primarily made of GAG and proteoglycans |
| What are GAG? | glycosaminoglycans, polysaccharide chains mainly made up of disaccharides hydrophilic and form a gel-like matrix sucks alot of water (hyaluronic acid, chondrition sulphate, dermatan sulphate heparan sulpahte. |
| What are proteoglycans? | molecules that consist of core protein covalently attached to several sulphated GAGs Hyaluronic acid can form non covalent bonds with it, form the framework of the ECM and play an essential role in serving molecular exchanges through connective tissues. they form gels fix growth and control activity of enzymes and cell migration. |
| What are the two types of fibers? | collagen and elastin |
| What are collagen fibers? | collagen is the most abundant proteins in the human body, very resistant glycoproteins, insoluble in water but soluble in highly salted boiling water, can be denatured by collagenase.. alpha polypeptide chain organized in triple helix (called procollagen) aa chain differs according to the type of synthesized collagen. |
| What happens to collagen in extracellular matrix? | procollagens are cleaved on both sides, forming tropocollagen, that assemble from end to end to form microfibers, that also aggregate to form fibrils having striation of 67 nm, fibrils are then combined to form more thick fibers, depending on collagen type, which then can aggregate to form bundles. |
| List the main types of collagen. | Type I (most abundant, present as thick bundles in loose, dense and bone connective tissues
Type II (present in cartilage)
Type III (reticular fibers, thinner than others and donot form bundles form stroma of lymphoid cells and hematopoetic organs as well as basement membrane.
Type IV basement membrane |
| WWhat is elastin? | major component of elastin fibers, found in variable number of loose CT and abundant in elastic ligaments, arteries, cartilage. Ability to stretch and recoil back into original. Synthesis is same as collagen, elastin is mostly assosciated with other components , proteoglycans, structural glycoproteins. |
| What are structural glycoproteins? | globular proteins role in CT organization, interaction and attachment of cells to ECM. numerous, mainly fibronectin (link between cells and collagen and GAGs) Laminins (binding sites between cells and ECM) |
| Is the thickness of basement membrane the same? | no it varies according to epithelium location. |
| Talk about the mucous connective tissues. | Close to mesenchyme but more differentiated, ground substances are very abundant, viscous and rich with hyaluronic acid, found in umbilical cord and pulp of young teeth. |
| Talk about loose (Areolar) CT. | most widespread type, balanced proportions of cells and fibers, and abundant ground substance, flexible and resistant, roles (mechanical: support of tissues and organs/ metabolic: passage of various substances between blood and cells/ defense: inflammatory rxns immune processes.) |
| Talk about dense CT. | rich in fibers, few cells and non-abundant ground substances, role is resistance, CT with predominance of collagen fibers are of two types (irregular and regular) |
| Talk about the dense fibrous regular CT. | found in regions where tensions are on one direction, parallel bundles of collagen fibers (tendons, ligaments) |
| talk about dense fibrous irregular CT. | found in regions where tension is in all directions, bundles of fibers are interwitted and don't have an orientation allowing resistance of tension (dermis of the skin, capsules around organs) |
| Talk about CT with predominance of elastic fibers. | very rare, elastic fibers mostly smooth muscle cells are found between elastic fibers, ability to stretch and snap back to original shape, trachae. |
| Talk about predominant reticular fibers CT. | rich in cells and composed only of reticular fibers, (type III collagen) dispersed within matrix with proteoglycans, form stroma of hemapoietic and lymphoid organs (Spleen, bone marrow, lymph nodes and liver) |
