Connective Tissue
Osteoclasts of bone and microglia of the brain, although morphologically different, belong to the mononuclear phagocyte system.
(No extra definition)
Collagen Fibers
- Are a large family of proteins and comprise the most important fibrillar extracellular matrix componets. -Characteristics: flexible, high tensile strengh
All members of the mononuclear phagocyte system:
- Arise from a common stem cell in the bone narrow -Possess lysosomes -Are capable of phagocytosis -Display receptors for complement
Cell Adhesive Glycoproteins are large macromolecules with several domains that bind to:
- Cell surface proteins called integrins. -Collagen fibers -Proteoglycans
Adipose cells (fat cells, adipocytes)
- Derived from undifferentiated fibroblast-like mesenchymal cells. Function: Synthesis and storage of triglycerides Producing hormones know as adipokines
Dense Regular Connective Tissue (Elastic)
- Possesses coarse branching elastic fibers with only a few collagen fibers forming network -Present in large blood vessels, ligamentum flavum of the vertebral column, and the suspensory ligament of the penis.
Pericytes
-Are multi-functional mural cells that surround endothelial cells of the capillaries and small venules. (Reside outside of the connective tissue compartment because they posses their own basal lamina) -Pericytes posses characteristics of endothelial cells and smooth muscle cells in that they contain actin, myosin and tropomyosin Function: Contraction in small Blood vessels (picture- blood vessel)
Dense Regular Connective Tissue Collagenous
-Coarse (grueso) collagen bundles packed and oriented into parallel cylinder or sheets that resist tensile forces. -Thin, sheet-like fibroblasts are located between bundles of collagen
Dense irregular connective tissue
-Contains mostly coarse (grueso) collagen fibers interwoven (entretejido) into a meshwork (mall) that resist stress from all firections. -The collagen bundles are packed so tightly that space is limited for ground substance and cells.
Characteristics of Myofibroblast
-Elongated, Spindly connective tissue cell. -H&E stain: not easily distinguished by routine light microscopy. -EM: bundles of actin filaments and myosin. Myofibroblasts are abundant in areas undergoing wound healing where they function in wound contraction. -Display typical characteristics of the fibroblast and the smooth muscle cells.
Depending upon the signal proteins present, Fibroblast may differentiate into, what other cells of connective tissue?
-Fat cell -osteoblasts -chondroblasts -myofibroblast
Connective Tissue Fibers
-Fibrillar proteins determine the tensile properties of the support tissues. -The are four major proteins that form fibrils in the extracellular matrix: 1. Collagen 2. Fibrin 3. Elastin 4. Fibronectin
Dense Connective Tissue
-Most abundance of fibers -Fewer cells than loose connective tissue -Dense irregular connective tissue: The collagen fiber bundles are arranged randomly -Dense regular connective tissue The fiber bundles of the tissue are arranged in parrallel or organized 1. Elastic Type 2. Collagenous type
Functions of Macrophages
-Phagocytose foreign substances and amaged and senescent cells as well as cellular debris(escombros) -Also, Assit in the initiation of the immune response. -Play a Key Role in presenting antigens to lymhocytes and are therfore also know as antigen-presenting cells
Reticular Fibers (reticulin fibers)
-Provide a supporting framework for the cellular constituents of various tissues and organs. -Thin fibrils (20 nm) of Type III Collagen Staining: PAS (periodic acid acid-schiff reaction) After silver treatment: fibers appear black (argyrophilic)
Classification of Connective tissue
1. Connective Tissue Proper -Loose connective tissue -Dense connective tissue -Dense irregular connective tissue -Dense regular connective tissue 2. Specialized Connective Tissue -Adipose -Cartilage -blood -bone
The collagens can be divided into several families according to the types of structure they form:
1. Fibrillar collagens: types i, ii, iii, V, XI 2. Short-chain collagens: Types VIII, X 3.Basement membrane collagens: type IV 4. Other collagens: types VI, VII, XIII *Collagen types I, II and III are arranged as rope-like fibrils and are the main forms of fibrillar collagen
Support cells (Connective tissue) and description of each cell
1. Fibroblasts: Secrete extracellular matrix components in most tissues, usually collagen and elastin. *Most important and abundant 2. Chondrocytes: Secrete the extracellular matrix components of cartilage. 3. Osteoblasts: Secrete the extracellular matrix components of bone. 4. Myofibroblasts: Secrete extracellular matrix components and also have a contractile function. 5. Adipocytes: Are specially adapted lipid-storing support cells which not only acts as an energy store, but also have a cushioning and padding function
Which are the mayor types of adhesive glycoproteins?
1. Fibronectin 2. Laminin 3. entactin 4. tenascin 5. chondronectin 6. osteonectin
Characteristic of Connective Tissue
1. Forms the Structural Support of the body 2. It is a site for fat storage 3. Composed by support cells and their associated extracellular matrix. 4. Support cells are vital in providing mechanical stability to tissues. 5. Provides the cell and macromolecules that defend the body by mounting an inflammatory and/ or immune response. 6. Is the medium for the exchange of the cell's waste products with nutrientes and oxygen.
Name of Macrophages by area
1. Kupffer cells- Liver 2.Dust cells- Lung 3. Langerhans cells-skin
Which are the 3 types of Ground Substance of the extracellular Matrix?
1. Proteoglycans: aggrecan, syndecan 2. Cell adhesion Glycoproteins: fibreonectin, laminin 3. Glycosaminoglycans: keratan sulfate, hyaluronic acid. Ground Substances -Function: To attach everything together -Provides mechanical and structural support for tissues and influences extracellular communication
Functions of the Extracellular Matrix (ECM):
1. Tensile strength for the tissue 2. Biochemical barrier 3. Provides pathways for cell migration 4. Modulate cell growth
The extracellular matrix is composed of:
A hydrated gel-like ground substance with fibers embedded in it.
Marfan's Syndrome
Abnormal expression of the fibrillin gene, autosomal dominant connective tissue disorder. Absence of the elastin-associated fibrillin microfibrils. *Abnormal Elastic Tissue. -Affect Musuclar and Cardiovascular System.
Loose connective tissue is characterized by...
Abundant ground substance and extrecellular fluid (tissue fluid) housing the fixed connective tissue cells: fibroblasts, adipose cells, macrophages, and amst cells, as well as some undifferentiated cells. -Collagen fibers (most sticky) -Reticular fibers -Elastic fibers
Fibroblasts may occur in either an
Active state or a quiescent state. -Active fibroblast -Quiescent fibroblast (fibrocyte) EM: abundant rough endoplasmic reticulum (RER), especially when the cell is actively manufacturing matrix, as in wound healing.
Fibroblasts (picture)
Basophilic cytoplasm reflecting active collagen synthesis (purple)
Mast cells arise from?
Bone Marrow stem cells -20-30 uM diameter They are ovoid and posses a centrally placed, spherical nucleus.
The ability of cells to adhere to components of the Extracellular Matrix (ECM) is mediated to a great extent by...
Cell adhesive glycoproteins
Fixed Cells (cellular components):
Cell that have developed and remain in place within the connective tissue. -Fibroblasts -Adipose cells -Pericytes
Extracellular Matrix consist of:
Consist of ground substance and fibers. -Cells -Fibers -Ground Substance *All 3 components are critical to the role of connective tissue function in the body.
What are proteoglycans?
Constitute a family of macromolecules; each is composed of a protein core to which GAGs are covalently bonded.
Dense irregular connective tissue (Trichrome staining of a section from skin)
D= Dense irregular C T Blue= Collagen fibers
Microfibrils contain fibrillin and are important components of elastic fibers.
Fibrillin is a fibril forming glycoprotein and the main component of extracellular microfibrils. Microfibrils are prominent in elastic containing extracellular matrix, particularly in lung, skin and blood vessel walls.
What cells synthesize the Extracellular Matrix (ECM)?
Fibroblast synthesize the ECM
Which are the most abundant cells of Dense irregular connective tissue and where are they located?
Fibroblasts, the most abundant cells of this tissue and are located in the interstices between collagen bundles Location: It constitutes the dermis of skin; the sheaths of nerves; and the capsules of spleen, testes, ovary, kidney, and lymph nodes.
Elastin
Hydrophobic protein prodiced by fibroblasts -Elastin fibers are formed by the interaction of elastin and fibrillin -Elastic Fibers confer elasticity to the tissues and allow them to recoil after strectching.
Loose connective tissue contains many transient cells responsible for...
Inflammation, allergic rx, and the immune response *Because this tissue lies immediately beneath the thin epithelia of the digestive and respiratory tracts, it is here that the body first attacks antigens, bacteria, and other foreign invaders.
Loose and dense irregular connective tissue in mammary gland
LCT= Loose connective tissue DICT= Dense irregular connective tissue (look for GE)
location of loose connective tissue
Lies below the mesothelial lining of the internal body cavities -It is associated with the adventitia of bloo vessels, and sorrounds the parenchyma of glands
Reticular fibers form the main extracellular matrix fibers supporting the haemopoietic and lymphoid tissues.
Lymph node Silver Stain
Which are the Mast cell granules in a Inflammatory Response?
Mast Cell granules" 1. Primary mediators: HISTAMINE 2. Secondary mediators: leukotrienes, thromboxanes, and prostaglandins
Give rise to the connective tissues and their cells
Mesenchymal cells (Fibroblast is the most important an abundant)
Macrophages arise from?
Monocytre developed in the Bone Marrow and circulate in the blood. *At the proper signal, they leave the bloodstream by migrating through the endothelium of capillaries or venules.
Macrophages belong to the___________?
Mononuclear phagoctic system.
Macrophages of the connective tissue spleen, lymph nodes, thymus, and bone marrow are all members of the...
Mononuclear phagocyte system and possess similar morphology and functions.
What are GAGs?
Negatively charged, long, rod-like chains of repeating disaccharides that have the capability of binding large quantities of water.
Transcient Cells (Cellular Matrix)
Originate mainly in the bone marrow and circulate in the bloodstream. Plasma cells -Lymphocytes -Neutrophils -Eosinophils -Basophils -Monocytes -Macrophages -Mast Cells
Mallory's connective tissue stain ( anylin blue)Mallory's connective tissue stain ( anylin blue)
Stain readily with eosin and other acidic dyes. (acidophilic). To identify connective tissue, specially collagen fibers
Elastic Fibers allow tissues to respond to...
Stretch and distention -Elastic Fibers are thinner than the collagen fibers. (Staining: takes up acidic dyes such as eosin better than collagen. Special dyes: orcein or resorcin fuchsin)
Main function of connective tissue
Structural Support
Fibrocytes (picture)
The fibroblasts lose their voluminous basophilic cytoplasm and the nucleus shrinks (se encoje). Fibrocytes->purple Collagen- pink
Fibroblasts
The most abundant and most widely distributed resident cells of connective tissue.
What is the identifying characteristic of Mast cells?
The presence of numerous granules in the cytoplasm
Reticular Fibers Characteristics
They form a loose mesh in many support tissues and areparticularly evident in a zone beneath basement membranes , where they are thought to have a support function as part of the fibroreticular lamina. Location: At the bounday of connective tissue and epithelium. Surrounding adipocytes, small blood vessels, nerves, and muscle cells. Prominent in the initial stages of wound healing and scar tissue formation Also function as a supporting stroma in hemopoietic and lymphatic tissues.
What occurs when a pathogenic bacteria, such as Staphylococcus aureus secrete hyaluronidase into the cell?
This enzyme cleaves hyaluronic acid into numerous small fragments, converting the gel state of the Extracellular Matrix (ECM) to a sol (liquid) State This permit the rapid spread of bacteria through the connective tissue spaces.
Masson's stain ( light Green)
To identify connective tissue, specially collagen fibers
Macrophages and subdivided into which groups of cells?
Two groups: Phagocytes and antigen-presenting cell
Where Fibroblasts derivate from?
Undifferentiated mesenchymal cells.
What are the two types of fat cells, which constitute two types of adipose tissue?
Unilocular fat cells white adipose tissue Multilocular fat cells Brown adipose tissue
How is the loose connective tissue of the mucous membranes called?
lamina propria (as in the alimentary canal)
Dense regular collagenous connective tissue from monkey tendon (Picture)
parallel arrangement
