11.10.11-+Connective+Tissue

CONNECTIVE TISSUE


 * 1. Define tissue fluid, describe its functions, and trace its flow into and out of areolar connective tissue.**

Tissue fluid is one of the three possible noncellular components of connective tissue. Tissue fluid is closely related to blood, but is a separate body of fluid outside of the vessels. We pick up its story when it is the fluid of the blood traveling through arteries to arterioles to capillaries. In capillaries, the walls are thin enough that the higher hydrostatic pressures within the capillary are able to push tissue fluid out of the vessel and into the surrounding tissue. As this occurs, the osmolarity (concentration) of the blood increases. After a while it increases so much that the osmotic pressure pushing fluid from tissue into vessel becomes higher than the hydrostatic pressure pushing fluid from vessel into tissue. When this occurs, fluid begins to move back into the capillaries.

During this flow and location switching, other extra-cellular structures are brought along for the ride. The function of this fluid flow out of and then back into capillaries is to deposit nutrients in tissues, remove wastes from tissues, and transport cytokines to areas of inflammation/infection. This is the method of dispersion for substances in the blood.


 * 2. Define (amorphous) ground substance and describe its role in areolar connective tissue.**

Ground substance is made up of three different macromolecules: proteoglycans, glycoproteins, and glycosaminoglycans (GAG).

Glycosaminoglycans are mostly carbohydrates; there is one really large and unsulfated one (hyaluronic acid), the rest are sulfated and smaller. The four smaller glycosoaminoglycans that we need to know are heparin, keratin, dermatin, and chondroitin sulfate. These four GAGs are associated with the next class of macromolecules: proteoglycans.

Proteoglycans have a protein core that serves as a branch point for the four sulfated GAGs.

Glycoproteins are the third type of macromolecule in the ECM of CT. Four glycoproteins are relevant for us: elastin, laminin, fibronectin, and chondronectin. Elastin is the principal component of elastic fibers. Fibronectin is associated with integrins in the cellular membrane and the collagen of the ECM, especially in regions in transition (e.g. wounds). In more stable structures, laminin takes the place of fibronectin and fulfills the same function. Chondronectin is a fiber that maintains the location of chondrocytes in cartilage.

Amorphous ground substance is the mass of areolar connective tissue, filling the gaps between tissues of the body.


 * 3. Describe the general structure and give the function of the following. **

A. Glycoproteins 1) Laminin 2) Fibronectin 3) Chondronectin B. Hyaluronic Acid  C. Sulfated Glycosaminoglycans (Heparan Sulfate, Chondroitin Sulfates, Keratin, Sulfate, Dermatin Sulfate) D. Proteoglycans

All collagen is formed from a helix of three amino acid chains with globules at the end. Glycine is every third amino acid (provides flexibility). Proline is also common (provides structure).
 * 4. Collagen **
 * A. What are the characteristic features common to all collagens? **


 * B. Describe the following groups of collagens: fibril-forming, fibril-associated, network-forming, and anchoring.**

Fibril-forming: I, II, III, V, XI (no globules, can associate into fibers) Network Forming: IV (matrix forming) Fibril Associated: IX, XII (cross-link fibrils) Anchoring: VII (looped to anchor I to to the basement membrane)


 * C. Outline the major steps in the synthesis of procollagen. **

AA chain synthesized on RER. Transported to golgi where prolines and lysines are hydroxylated, then hydroxylysines are glycosylated, and three chains associate into tri-helix and globule region. This is procollagen;


 * D. Describe extracellular processing in collagen fiber synthesis. **

Procollagen is then exocytosed into little invagination where if the collagen is fibril forming (I, II, III, V, XI) then globules are removed (now called tropocollagen) and helices associate into fibrils; fibrils then associate into fibers.


 * 5. Describe the location, function, and arrangement of collagen molecules in collagen types I, II, III, IV, VII, and IX. You will not be expected to recite the alpha chain composition of each subtype.**


 * Tissue || Collagen Type || Notes ||
 * Skin || I, III, V ||  ||
 * Tendon || I ||  ||
 * Bond || I ||  ||
 * Dentin || I ||  ||
 * Vitreus || II, IX ||  ||
 * Vessel || III ||  ||
 * Cartilage || II, IX, XI ||  ||
 * Organ || III, V ||  ||
 * Basement Membrane || IV ||  ||
 * Epithelium || VII ||  ||


 * 6. Elastic fibers - Describe the structure, composition and function of elastic fibers. **

Elastic fibers are primarily composed of elastin, a glycoprotein. Elastic fibers cross-link into membranes (vessel walls) or stay as long strands (elastic cartilage).


 * 7. Reticular fibers - Describe the structure, composition and function of reticular fibers.**

Reticular fibers are primarily composed of collagen III, with proteoglycans (protein core w/ GAGs) and glycoproteins (laminin, fibronectin, chondroinectin). Present in skin, the walls of vessels, smooth muscle, and the stroma of organs.


 * 8. Name and describe the morphology and major functions or products of the following connective tissue cells:**

-fibroblast (fibrocyte) -macrophage (histiocyte) - mast cell, plasma cell - unilocular adipocyte - multilocular adipocyte - neutrophil -basophil - eosinophil - lymphocyte -dendritic cell


 * 9. Describe the concept of resident and migratory connective tissue cells. List the cell types in each classification.**

Resident: Originate from undifferentiated mesenchymal cells (fibroblasts, osteoblasts, chondroblasts, adipocytes) Migratory: Originate from bone marrow hematopoeitic stem cells (leukocytes, erythrocytes, mononuclear phagocyte system, mast cells, and megakaryocytes)


 * 10. Define basal lamina, lamina lucida, lamina densa, reticular lamina, and basement membrane.**

The basement membrane is subdivided into the basal lamina and the reticular lamina. The basal lamina is further subdivided into the lamina lucida and the lamina densa. Basement membrane: present only under epithelial cells Basal lamina: present under many (all) immobile cells


 * 11. Describe the role of laminin & fibronectin, anchoring filaments, and anchoring fibrils in the attachment of basement membranes to cells and the underlying connective tissue.**

laminin: replaces fibronectin to anchor cells after development is over/wound closed fibronectin: anchor from integrins of cell membranes in transition (development/wounds) to collagen of ECM. Interconnected by proteoglycans. anchoring filaments: protein extensions from hemidesmosomes through the lamina lucida that attach to lamina densa anchoring fibrils: composed of collagen VII, present where extra attachment required, like skin to basement membrane.


 * 12. Identify which cell types have and which do not have a basal lamina. (Include cell types from all four primary tissue types as they are studied in the rest of this course.**

Epithelial Muscle Nervous Connective


 * 13. Define the mononuclear phagocyte system and list the component cell types. **

Monocytes are cells derived in blood marrow that travel through blood and disperse themselves in many tissue types. Once they arrive, they undergo differentiation and are renamed depending on their location: Connective tissue (myeloid dendritic cells and macrophages), Liver (Kuppfer Cells), Bone (Osteoclasts), etc.

A. Areolar connective tissue B. Reticular connective tissue C. Mesenchyme D. Adipose - white and brown fat E. Dense irregular connective tissue F. Dense regular connective tissue.
 * 14. Compare and contrast the structure, composition, and function of the following classes of connective tissue.**

A. Fibroblast/fibrocyte H. Unilocular adipocyte B. Adipocyte I. Multilocular adipocyte C. Macrophage J. Areolar (loose) connective tissue D. Mast cell K. Dense irregular connective tissue E. Plasma cell L. Dense regular connective tissue F. Lymphocyte M. Adipose tissue G. Eosinophil
 * 15. Identify the following microanatomical features in photomicrographs of histological sections.**