Collagen is the main structural protein in the extracellular space in the various connective tissues in the body. As the main component of connective tissue, it is the most abundant protein in mammals, making 25% to 35% of the whole-body protein content. Collagen consists of amino acids wound together to form triple-helices of elongated fibrils, it is found in fibrous tissues such as tendons and skin. Depending upon the degree of mineralization, collagen tissues may be rigid, compliant, or have a gradient from rigid to compliant, it is abundant in corneas, blood vessels, the gut, intervertebral discs, the dentin in teeth. In muscle tissue, it serves as a major component of the endomysium. Collagen constitutes one to two percent of muscle tissue and accounts for 6% of the weight of strong, muscles; the fibroblast is the most common cell. Gelatin, used in food and industry, is collagen that has been, hydrolyzed. Collagen has many medical uses in treating complications of skin; the name collagen comes from the Greek κόλλα, meaning "glue", suffix -γέν, -gen, denoting "producing".
This refers to the compound's early use in the process of boiling the skin and tendons of horses and other animals to obtain glue. Over 90% of the collagen in the human body is type I. However, as of 2011, 28 types of collagen have been identified and divided into several groups according to the structure they form: Fibrillar Non-fibrillar FACIT Short chain Basement membrane Multiplexin MACIT Other The five most common types are: Type I: skin, vasculature, bone Type II: cartilage Type III: reticulate found alongside type I Type IV: forms basal lamina, the epithelium-secreted layer of the basement membrane Type V: cell surfaces and placenta The collagenous cardiac skeleton which includes the four heart valve rings, is histologically and uniquely bound to cardiac muscle; the cardiac skeleton includes the separating septa of the heart chambers – the interventricular septum and the atrioventricular septum. Collagen contribution to the measure of cardiac performance summarily represents a continuous torsional force opposed to the fluid mechanics of blood pressure emitted from the heart.
The collagenous structure that divides the upper chambers of the heart from the lower chambers is an impermeable membrane that excludes both blood and electrical impulses through typical physiological means. With support from collagen, atrial fibrillation never deteriorates to ventricular fibrillation. Collagen is layered in variable densities with cardiac muscle mass; the mass, distribution and density of collagen all contribute to the compliance required to move blood back and forth. Individual cardiac valvular leaflets are folded into shape by specialized collagen under variable pressure. Gradual calcium deposition within collagen occurs as a natural function of aging. Calcified points within collagen matrices show contrast in a moving display of blood and muscle, enabling methods of cardiac imaging technology to arrive at ratios stating blood in and blood out. Pathology of the collagen underpinning of the heart is understood within the category of connective tissue disease. Collagen has been used in cosmetic surgery, as a healing aid for burn patients for reconstruction of bone and a wide variety of dental and surgical purposes.
Both human and bovine collagen is used as dermal fillers for treatment of wrinkles and skin aging. Some points of interest are: When used cosmetically, there is a chance of allergic reactions causing prolonged redness. Most medical collagen is derived from young beef cattle from certified BSE-free animals. Most manufacturers use donor animals from either "closed herds", or from countries which have never had a reported case of BSE such as Australia and New Zealand; as the skeleton forms the structure of the body, it is vital that it maintains its strength after breaks and injuries. Collagen is used in bone grafting as it has a triple helical structure, making it a strong molecule, it is ideal for use in bones. The triple helical structure of collagen prevents it from being broken down by enzymes, it enables adhesiveness of cells and it is important for the proper assembly of the extracellular matrix. Collagen scaffolds are used in tissue regeneration, whether in thin sheets, or gels. Collagen has the correct properties for tissue regeneration such as pore structure, permeability and being stable in vivo.
Collagen scaffolds are ideal for the deposition of cells such as osteoblasts and fibroblasts, once inserted, growth is able to continue as normal in the tissue. Collagens are employed in the construction of the artificial skin substitutes used in the management of severe burns and wounds; these collagens may be derived from bovine, porcine, or human sources. Collagen is one of the body’s key natural resources and a component of skin tissu
Macrophages are a type of white blood cell, of the immune system, that engulfs and digests cellular debris, foreign substances, cancer cells, anything else that does not have the type of proteins specific to healthy body cells on its surface in a process called phagocytosis. These large phagocytes are found in all tissues, where they patrol for potential pathogens by amoeboid movement, they take various forms throughout the body. Besides phagocytosis, they play a critical role in nonspecific defense and help initiate specific defense mechanisms by recruiting other immune cells such as lymphocytes. For example, they are important as antigen presenters to T cells. In humans, dysfunctional macrophages cause severe diseases such as chronic granulomatous disease that result in frequent infections. Beyond increasing inflammation and stimulating the immune system, macrophages play an important anti-inflammatory role and can decrease immune reactions through the release of cytokines. Macrophages that encourage inflammation are called M1 macrophages, whereas those that decrease inflammation and encourage tissue repair are called M2 macrophages.
This difference is reflected in their metabolism. However, this dichotomy has been questioned as further complexity has been discovered. Human macrophages are about 21 micrometres in diameter and are produced by the differentiation of monocytes in tissues, they can be identified using flow cytometry or immunohistochemical staining by their specific expression of proteins such as CD14, CD40, CD11b, CD64, F4/80 /EMR1, lysozyme M, MAC-1/MAC-3 and CD68. Macrophages were first discovered by Élie Metchnikoff, a Russian zoologist, in 1884. A majority of macrophages are stationed at strategic points where microbial invasion or accumulation of foreign particles is to occur; these cells together as a group are known as the mononuclear phagocyte system and were known as the reticuloendothelial system. Each type of macrophage, determined by its location, has a specific name: Investigations concerning Kupffer cells are hampered because in humans, Kupffer cells are only accessible for immunohistochemical analysis from biopsies or autopsies.
From rats and mice, they are difficult to isolate, after purification, only 5 million cells can be obtained from one mouse. Macrophages can express paracrine functions within organs that are specific to the function of that organ. In the testis for example, macrophages have been shown to be able to interact with Leydig cells by secreting 25-hydroxycholesterol, an oxysterol that can be converted to testosterone by neighbouring Leydig cells. Testicular macrophages may participate in creating an immune privileged environment in the testis, in mediating infertility during inflammation of the testis. Cardiac resident macrophages participate in electrical conduction via gap junction communication with cardiac myocytes. Macrophages can be classified on basis of the fundamental activation. According to this grouping there are classically activated macrophages, wound-healing macrophages and regulatory macrophages. Macrophages that reside in adult healthy tissues either derive from circulating monocytes or are established before birth and maintained during adult life independently of monocytes.
By contrast, most of the macrophages that accumulate at diseased sites derive from circulating monocytes. When a monocyte enters damaged tissue through the endothelium of a blood vessel, a process known as leukocyte extravasation, it undergoes a series of changes to become a macrophage. Monocytes are attracted to a damaged site by chemical substances through chemotaxis, triggered by a range of stimuli including damaged cells and cytokines released by macrophages at the site. At some sites such as the testis, macrophages have been shown to populate the organ through proliferation. Unlike short-lived neutrophils, macrophages survive longer in the body, up to several months. Macrophages are professional phagocytes and are specialized in removal of dying or dead cells and cellular debris; this role is important in chronic inflammation, as the early stages of inflammation are dominated by neutrophils, which are ingested by macrophages if they come of age. The neutrophils are at first attracted to a site, where they proliferate, before they are phagocytized by the macrophages.
When at the site, the first wave of neutrophils, after the process of aging and after the first 48 hours, stimulate the appearance of the macrophages whereby these macrophages will ingest the aged neutrophils. The removal of dying cells is, to a greater extent, handled by fixed macrophages, which will stay at strategic locations such as the lungs, neural tissue, bone and connective tissue, ingesting foreign materials such as pathogens and recruiting additional macrophages if needed; when a macrophage ingests a pathogen, the pathogen becomes trapped in a phagosome, which fuses with a lysosome. Within the phagolysosome and toxic peroxides digest the pathogen. However, some bacteria, such as Mycobacterium tuberculosis, have become resistant to these methods of digestion. Typhoidal Salmonellae induce their own phagocytos
A fibroblast is a type of biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework for animal tissues, plays a critical role in wound healing. Fibroblasts are the most common cells of connective tissue in animals. Fibroblasts have a branched cytoplasm surrounding an elliptical, speckled nucleus having two or more nucleoli. Active fibroblasts can be recognized by their abundant rough. Inactive fibroblasts are smaller, spindle-shaped, have a reduced amount of rough endoplasmic reticulum. Although disjointed and scattered when they have to cover a large space, when crowded locally align in parallel clusters. Unlike the epithelial cells lining the body structures, fibroblasts do not form flat monolayers and are not restricted by a polarizing attachment to a basal lamina on one side, although they may contribute to basal lamina components in some situations. Fibroblasts can migrate over substratum as individual cells, again in contrast to epithelial cells.
While epithelial cells form the lining of body structures, it is fibroblasts and related connective tissues which sculpt the "bulk" of an organism. The life span of a fibroblast, as measured in chick embryos, is 57 ± 3 days. Fibroblasts and fibrocytes are two states of the same cells, the former being the activated state, the latter the less active state, concerned with maintenance and tissue metabolism. There is a tendency to call both forms fibroblasts; the suffix "-blast" is used in cellular biology to denote a stem cell or a cell in an activated state of metabolism. Fibroblasts are morphologically heterogeneous with diverse appearances depending on their location and activity. Though morphologically inconspicuous, ectopically transplanted fibroblasts can retain positional memory of the location and tissue context where they had resided, at least over a few generations; this remarkable behavior may lead to discomfort in the rare event that they stagnate there excessively. The main function of fibroblasts is to maintain the structural integrity of connective tissues by continuously secreting precursors of the extracellular matrix.
Fibroblasts secrete the precursors of all the components of the extracellular matrix the ground substance and a variety of fibers. The composition of the extracellular matrix determines the physical properties of connective tissues. Like other cells of connective tissue, fibroblasts are derived from primitive mesenchyme, thus they express the intermediate filament protein vimentin, a feature used as a marker to distinguish their mesodermal origin. However, this test is not specific as epithelial cells cultured in vitro on adherent substratum may express vimentin after some time. In certain situations epithelial cells can give rise to fibroblasts, a process called epithelial-mesenchymal transition. Conversely, fibroblasts in some situations may give rise to epithelia by undergoing a mesenchymal to epithelial transition and organizing into a condensed, laterally connected true epithelial sheet; this process is seen in many developmental situations, as well as in wound healing and tumorigenesis.
Fibroblasts make collagen fibres, glycosaminoglycans and elastic fibers, Growing individuals' fibroblasts are dividing and synthesizing ground substance. Tissue damage stimulates induces the production of fibroblasts. Besides their known role as structural components, fibroblasts play a critical role in an immune response to a tissue injury, they are early players in initiating inflammation in the presence of invading microorganisms. They induce chemokine synthesis through the presentation of receptors on their surface. Immune cells respond and initiate a cascade of events to clear the invasive microorganisms. Receptors on the surface of fibroblasts allow regulation of hematopoietic cells and provide a pathway for immune cells to regulate fibroblasts. Fibroblasts, like the tumor-associated host fibroblasts, play a crucial role in immune regulation through TAF-derived extracellular matrix components and modulators. TAF are known to be significant in the inflammatory response as well as immune suppression in tumors.
TAF-derived ECM components initiate the ECM remodeling. The ECM remodeling is described as changes in the ECM as a result of enzyme activity which can lead to degradation of the ECM. Immune regulation of tumors is determined by the ECM remodeling because the ECM is responsible for regulating a variety of functions, such as proliferation and morphogenesis of vital organs. In many tumor types those related to the epithelial cells, ECM remodeling is common. Examples of TAF-derived ECM components include Tenascin and Thrombospondin-1, which can be found in sites of chronic inflammation and carcinomas respectively. Immune regulation of tumors can occur through the TAF-derived modulators. Although these modulators may sound similar to the TAF-derived ECM components, they differ in the sense that they are responsible for the variation and turnover of the ECM. Cleaved ECM molecules can play a critical role in immune regulation. Proteases like matrix metalloproteineases and the uPA system are known to cleave the ECM.
These proteases are derived from fibroblasts. Mouse embryonic fibroblasts are used as "feeder cells" in human embryonic stem cell research. However, many researchers are phasing o
Pathology is the study of the causes and effects of disease or injury. The word pathology refers to the study of disease in general, incorporating a wide range of bioscience research fields and medical practices. However, when used in the context of modern medical treatment, the term is used in a more narrow fashion to refer to processes and tests which fall within the contemporary medical field of "general pathology," an area which includes a number of distinct but inter-related medical specialties that diagnose disease through analysis of tissue and body fluid samples. Idiomatically, "a pathology" may refer to the predicted or actual progression of particular diseases, the affix path is sometimes used to indicate a state of disease in cases of both physical ailment and psychological conditions. A physician practicing pathology is called a pathologist; as a field of general inquiry and research, pathology addresses four components of disease: cause, mechanisms of development, structural alterations of cells, the consequences of changes.
In common medical practice, general pathology is concerned with analyzing known clinical abnormalities that are markers or precursors for both infectious and non-infectious disease and is conducted by experts in one of two major specialties, anatomical pathology and clinical pathology. Further divisions in specialty exist on the basis of the involved sample types and physiological systems, as well as on the basis of the focus of the examination. Pathology is a significant field in medical research; the study of pathology, including the detailed examination of the body, including dissection and inquiry into specific maladies, dates back to antiquity. Rudimentary understanding of many conditions was present in most early societies and is attested to in the records of the earliest historical societies, including those of the Middle East and China. By the Hellenic period of ancient Greece, a concerted causal study of disease was underway, with many notable early physicians having developed methods of diagnosis and prognosis for a number of diseases.
The medical practices of the Romans and those of the Byzantines continued from these Greek roots, but, as with many areas of scientific inquiry, growth in understanding of medicine stagnated some after the Classical Era, but continued to develop throughout numerous cultures. Notably, many advances were made in the medieval era of Islam, during which numerous texts of complex pathologies were developed based on the Greek tradition. So, growth in complex understanding of disease languished until knowledge and experimentation again began to proliferate in the Renaissance and Baroque eras, following the resurgence of the empirical method at new centers of scholarship. By the 17th century, the study of microscopy was underway and examination of tissues had led British Royal Society member Robert Hooke to coin the word "cell", setting the stage for germ theory. Modern pathology began to develop as a distinct field of inquiry during the 19th Century through natural philosophers and physicians that studied disease and the informal study of what they termed “pathological anatomy” or “morbid anatomy”.
However, pathology as a formal area of specialty was not developed until the late 19th and early 20th centuries, with the advent of detailed study of microbiology. In the 19th century, physicians had begun to understand that disease-causing pathogens, or "germs" existed and were capable of reproduction and multiplication, replacing earlier beliefs in humors or spiritual agents, that had dominated for much of the previous 1,500 years in European medicine. With the new understanding of causative agents, physicians began to compare the characteristics of one germ’s symptoms as they developed within an affected individual to another germ’s characteristics and symptoms; this realization led to the foundational understanding that diseases are able to replicate themselves, that they can have many profound and varied effects on the human host. To determine causes of diseases, medical experts used the most common and accepted assumptions or symptoms of their times, a general principal of approach that persists into modern medicine.
Modern medicine was advanced by further developments of the microscope to analyze tissues, to which Rudolf Virchow gave a significant contribution, leading to a slew of research developments. By the late 1920s to early 1930s pathology was deemed a medical specialty. Combined with developments in the understanding of general physiology, by the beginning of the 20th century, the study of pathology had begun to split into a number of rarefied fields and resulting in the development of large number of modern specialties within pathology and related disciplines of diagnostic medicine; the term pathology comes from the Ancient Greek roots of pathos, meaning "experience" or "suffering" and -logia, "study of". The modern practice of pathology is divided into a number of subdisciplines within the discrete but interconnected aims of biological research and medical practice. Biomedical research into disease incorporates the
Lobules of liver
A hepatic lobule is a small division of the liver defined at the microscopic. The hepatic lobule is a building block of the liver matter, consisting of a portal triad, hepatocytes arranged in linear cords between a capillary network, a central vein, it should not be confused with the anatomic lobes of the liver, or any of the functional lobe classification systems. The two-dimensional microarchitecture of the liver can be viewed from multiple different perspectives: The term "hepatic lobule", without qualification refers to the classical lobule; the hepatic lobule can be described in terms of metabolic "zones". Each zone is centered on the line connecting two portal triads and extends outwards to the two adjacent central veins; the periportal zone I is nearest to the entering vascular supply and receives the most oxygenated blood, making it least sensitive to ischemic injury while making it susceptible to viral hepatitis. Conversely, the centrilobular zone III has the poorest oxygenation, will be most affected during a time of ischemia.
The portal triad is a functional unit of the liver and consists of three vessels, the interlobular arterie, the interlobular vein and a bile duct. Zones differ by function: zone I hepatocytes are specialized for oxidative liver functions such as gluconeogenesis, β-oxidation of fatty acids and cholesterol synthesis zone III cells are more important for glycolysis and cytochrome P-450-based drug detoxification; this specialization is reflected histologically. Other zonal injury patterns include zone I deposition of hemosiderin in hemochromatosis and zone II necrosis in yellow fever. Bridging fibrosis, a type of fibrosis seen in several types of liver injury, describes fibrosis from the central vein to the portal triad. Histology image: 15401loa – Histology Learning System at Boston University Histology at siumed.edu Histology at okstate.edu Histology at webmd.idv.tw. UIUC Histology Subject 923
International Standard Serial Number
An International Standard Serial Number is an eight-digit serial number used to uniquely identify a serial publication, such as a magazine. The ISSN is helpful in distinguishing between serials with the same title. ISSN are used in ordering, interlibrary loans, other practices in connection with serial literature; the ISSN system was first drafted as an International Organization for Standardization international standard in 1971 and published as ISO 3297 in 1975. ISO subcommittee TC 46/SC 9 is responsible for maintaining the standard; when a serial with the same content is published in more than one media type, a different ISSN is assigned to each media type. For example, many serials are published both in electronic media; the ISSN system refers to these types as electronic ISSN, respectively. Conversely, as defined in ISO 3297:2007, every serial in the ISSN system is assigned a linking ISSN the same as the ISSN assigned to the serial in its first published medium, which links together all ISSNs assigned to the serial in every medium.
The format of the ISSN is an eight digit code, divided by a hyphen into two four-digit numbers. As an integer number, it can be represented by the first seven digits; the last code digit, which may be 0-9 or an X, is a check digit. Formally, the general form of the ISSN code can be expressed as follows: NNNN-NNNC where N is in the set, a digit character, C is in; the ISSN of the journal Hearing Research, for example, is 0378-5955, where the final 5 is the check digit, C=5. To calculate the check digit, the following algorithm may be used: Calculate the sum of the first seven digits of the ISSN multiplied by its position in the number, counting from the right—that is, 8, 7, 6, 5, 4, 3, 2, respectively: 0 ⋅ 8 + 3 ⋅ 7 + 7 ⋅ 6 + 8 ⋅ 5 + 5 ⋅ 4 + 9 ⋅ 3 + 5 ⋅ 2 = 0 + 21 + 42 + 40 + 20 + 27 + 10 = 160 The modulus 11 of this sum is calculated. For calculations, an upper case X in the check digit position indicates a check digit of 10. To confirm the check digit, calculate the sum of all eight digits of the ISSN multiplied by its position in the number, counting from the right.
The modulus 11 of the sum must be 0. There is an online ISSN checker. ISSN codes are assigned by a network of ISSN National Centres located at national libraries and coordinated by the ISSN International Centre based in Paris; the International Centre is an intergovernmental organization created in 1974 through an agreement between UNESCO and the French government. The International Centre maintains a database of all ISSNs assigned worldwide, the ISDS Register otherwise known as the ISSN Register. At the end of 2016, the ISSN Register contained records for 1,943,572 items. ISSN and ISBN codes are similar in concept. An ISBN might be assigned for particular issues of a serial, in addition to the ISSN code for the serial as a whole. An ISSN, unlike the ISBN code, is an anonymous identifier associated with a serial title, containing no information as to the publisher or its location. For this reason a new ISSN is assigned to a serial each time it undergoes a major title change. Since the ISSN applies to an entire serial a new identifier, the Serial Item and Contribution Identifier, was built on top of it to allow references to specific volumes, articles, or other identifiable components.
Separate ISSNs are needed for serials in different media. Thus, the print and electronic media versions of a serial need separate ISSNs. A CD-ROM version and a web version of a serial require different ISSNs since two different media are involved. However, the same ISSN can be used for different file formats of the same online serial; this "media-oriented identification" of serials made sense in the 1970s. In the 1990s and onward, with personal computers, better screens, the Web, it makes sense to consider only content, independent of media; this "content-oriented identification" of serials was a repressed demand during a decade, but no ISSN update or initiative occurred. A natural extension for ISSN, the unique-identification of the articles in the serials, was the main demand application. An alternative serials' contents model arrived with the indecs Content Model and its application, the digital object identifier, as ISSN-independent initiative, consolidated in the 2000s. Only in 2007, ISSN-L was defined in the
Connective tissue is one of the four basic types of animal tissue, along with epithelial tissue, muscle tissue, nervous tissue. It develops from the mesoderm. Connective tissue is found in between other tissues everywhere in the body, including the nervous system. In the central nervous system, the three outer membranes that envelop the brain and spinal cord are composed of connective tissue, they protect the body. All connective tissue consists of three main components: ground substance and cells. Not all authorities include blood or lymph as connective tissue because they lack the fiber component. All are immersed in the body water; the cells of connective tissue include fibroblasts, macrophages, mast cells and leucocytes. The term "connective tissue" was introduced in 1830 by Johannes Peter Müller; the tissue was recognized as a distinct class in the 18th century. Connective tissue can be broadly subdivided into connective tissue proper, special connective tissue. Connective tissue proper consists of loose connective tissue and dense connective tissue Loose and dense connective tissue are distinguished by the ratio of ground substance to fibrous tissue.
Loose connective tissue has much more ground substance and a relative lack of fibrous tissue, while the reverse is true of dense connective tissue. Dense regular connective tissue, found in structures such as tendons and ligaments, is characterized by collagen fibers arranged in an orderly parallel fashion, giving it tensile strength in one direction. Dense irregular connective tissue provides strength in multiple directions by its dense bundles of fibers arranged in all directions. Special connective tissue consists of reticular connective tissue, adipose tissue, cartilage and blood. Other kinds of connective tissues include fibrous and lymphoid connective tissues. Fibroareolar tissue is a mix of fibrous and areolar tissue. New vascularised connective tissue that forms in the process of wound healing is termed granulation tissue. Fibroblasts are the cells responsible for the production of some CT. Type I collagen is present in many forms of connective tissue, makes up about 25% of the total protein content of the mammalian body.
Characteristics of CT: Cells are spread through an extracellular fluid. Ground substance - A clear and viscous fluid containing glycosaminoglycans and proteoglycans to fix the body water and the collagen fibers in the intercellular spaces. Ground substance slows the spread of pathogens. Fibers. Not all types of CT are fibrous. Examples of non-fibrous CT include adipose blood. Adipose tissue gives "mechanical cushioning" to the body, among other functions. Although there is no dense collagen network in adipose tissue, groups of adipose cells are kept together by collagen fibers and collagen sheets in order to keep fat tissue under compression in place; the matrix of blood is plasma. Both the ground substance and proteins create the matrix for CT. Connective tissues are derived from the mesenchyme. Types of fibers: Connective tissue has a wide variety of functions that depend on the types of cells and the different classes of fibers involved. Loose and dense irregular connective tissue, formed by fibroblasts and collagen fibers, have an important role in providing a medium for oxygen and nutrients to diffuse from capillaries to cells, carbon dioxide and waste substances to diffuse from cells back into circulation.
They allow organs to resist stretching and tearing forces. Dense regular connective tissue, which forms organized structures, is a major functional component of tendons and aponeuroses, is found in specialized organs such as the cornea. Elastic fibers, made from elastin and fibrillin provide resistance to stretch forces, they are found in the walls of large blood vessels and in certain ligaments in the ligamenta flava. In hematopoietic and lymphatic tissues, reticular fibers made by reticular cells provide the stroma—or structural support—for the parenchyma—or functional part—of the organ. Mesenchyme is a type of connective tissue found in developing organs of embryos, capable of differentiation into all types of mature connective tissue. Another type of undifferentiated connective tissue is mucous connective tissue, found inside the umbilical cord. Various types of specialized tissues and cells are classified under the spectrum of connective tissue, are as diverse as brown and white adipose tissue, blood and bone.
Cells of the immune system, such as macrophages, mast cells, plasma cells and eosinophils are found scattered in loose connective tissue, providing the ground for starting inflammatory and immune responses upon the detection of antigens. There are many types of connective tissue disorders, such as: Connective tissue neoplasms including sarcomas such as hemangiopericytoma and malignant peripheral nerve sheath tumor in nervous tissue. Congenital diseases include Ehlers-Danlos Syndrome. Myxomatous degeneration – a pathological weakening of connective tissue. Mixed connective tissue disease – a disease of the autoimmune system undifferentiated connective tissue disease. Systemic lupus erythematosus – a major autoimmune disease of connective tissue Scurvy, caused by a deficiency of vitamin C, necessary for the synthesis of collagen. For microscopic viewing, most of the connective tissue staining-techniques, colour tissue fibers in contrasting shades. Collagen may be differentially stained by any of the following: Van Gieson's stain Masson's trichrome stain Mallory's t