A perimarginal cavernous sinus is situated outside the marginal zone or directly adjacent to the lymphoid follicles, in areas where the marginal sinus is absent. Figure 8.16. The human spleen is surrounded by a capsule of dense connective tissue containing relatively little muscle and therefore incapable of the extensive contraction exhibited by the muscular capsule of the spleen in dogs and cats. To understand why connective tissue is so important, lets take a close look at the various kinds of connective tissue, along with some examples. Initial evidence that distinct subsets of pre-cDCs may exist came from analysis of CD24 expression which subdivided pre-cDCs into three populations based on CD24 expression (CD24hi, CD24int, and CD24lo), with CD24hi and CD24lo cells preferentially generating cDC1s and cDC2s, respectively, while CD24int cells maintained the potential to generate both subsets (Naik etÂ al., 2007, 2006). The units that together form these fibers are called reticular cells or fibroblasts. Macrophages, which differentiate from circulating monocytes, are often the predominant cells. Menstrual endometrium is a mixture of late secretory phase endometrium and âsloughing endometrium.â Sloughing endometrium is composed of compact stromal balls surrounded by epithelium and, at times, prominent neutrophil infiltration. The proliferative phase endometrium is found during the first half of the cycle when estrogen levels are high, and it is relatively thin at the beginning of the cycle (immediately following menstruation). 8.15A). It has an irregular interface with the smooth muscle myometrium, and the endometrial appearance and thickness vary tremendously with menstrual cycle/hormonal status. Bruchâs membrane aids in the support of the internal structures of the eye, and selectively filters the passage of macromolecules between the retina and choriocapillaris. However, RPE (peripheral-lining, nonsensory, epithelial support cells to the retina) tight junctions prevent leakage into the retina of the healthy eye, and create osmotic pressure that assists in drawing fluid out of the retina through cellular mechanisms. C, capsule; Cx, cortex; F, follicle; H, hilum; M, medulla; Mc, medullary cords; P, paracortex; S, subcapsular sinus; T, trabecula. Unique Medical and Health Contents, Food and Educational Contents. (2013), with permission. Due to their function as exchange villi, sometimes more than 50% of the stromal cross section is dominated by vessels (capillaries and sinusoids). Identify and label the tissue type, total magnification, epidermis, dermis, dermal papillae and reticular layer. (A) The endocervix is composed of simple columnar mucinous epithelium. Once generated, the pre-cDC1s and pre-cDCs2 leave the BM and traffic via the blood to the different tissues, where they differentiate into cDC1s and cDC2s, respectively (Liu etÂ al., 2009; Schlitzer etÂ al., 2015; Naik etÂ al., 2007, 2006; Grajales-Reyes etÂ al., 2015). Once inside the lymph node, lymph enters a subscapular sinus (see Fig. After distributing branches to the white pulp and marginal zone, the central artery branches into straight, slender vessels called penicilli which may terminate as such or become finer arterial capillaries. This is the white pulp. Conversely, most domestic species have a layer of reflective tissue, the tapetum lucidum, interspersed between the choriocapillaris and the midsize vessels. 17.16). In humans, Bruchâs membrane is subject to a variety of senescent changes representing a significant cause of age-related visual defects, including age-related macular degeneration (AMD). FigureÂ 1. cDCs develop from HSCs through a series of intermediate precursor stages in the bone marrow. (2006), with permission. For a long time it was unclear if pre-cDCs represented a single population capable of generating both cDC subsets or if they could be further subdivided into cDC subset-specific progenitors. (A) Rodent estrus cycle. Both cDC subsets develop from hematopoietic stem cells in a stepwise manner through a number of intermediary progenitor cells before ultimately deriving from distinct precursors (Liu etÂ al., 2009; Schlitzer etÂ al., 2015; Grajales-Reyes etÂ al., 2015; Naik etÂ al., 2006). This villous type is much larger than mesenchymal villi with diameters between 100 and 300Â Î¼m. Areolar connective tissues hold organs in place and attaches epithelial tissue to other underlying tissues. In proestrus, the uterus is distended and hyperemic, mitotic cells are observed in the epithelial cells, and leukocytes infiltrate the stroma. In this micrograph of loose connective tissue of the tracheal mucosa numerous (labeled) cells of the connective tissue … Rodent uterine body and cervix. Interestingly, the number of terminal villi follows their microenvironment within the placenta. In the tissues, the pre-cDC subsets terminally differentiate into cDC1s and cDC2s. Connective tissue supports the body by providing a matrix that connects and binds the cells and organs. The lymphoid tissue is separated from the red pulp by the marginal zone. 8.16). Figure 1. Later Stages in the Maturation of B Cells. Jeffrey K. Actor PhD, in Elsevier's Integrated Review Immunology and Microbiology (Second Edition), 2012. Morphologic changes in the vaginal mucosa are associated with hormonal changes during the rodent estrus cycle. Areolar Tissue is loose connective tissue that consists of a meshwork of collagen, elastic tissue, and reticular fibres - with many connective tissue cells in between the meshwork of fibres There are more than 20 different types of reticular fibers in the human body. It is found mainly under the skin but also in deposits between the muscles, in the intestines and in This is made up by thin-walled blood vessels, the splenic sinuses (or sinusoids), and thin plates of cells which lie between the sinuses, the splenic cords. Blood vessel loops extend from the optic disc in the ventral and lateral planes the extent of the medullary rays, the myelinated axons of the ganglion cells that course on top of the retina before exiting the globe through the optic nerve. Estrogen exerts a proliferative effect on the endometrium, whereas progesterone leads to the differentiation of the endometrium. As the cycle progresses, the glands become dilated, serrated, and crowded. Within the sinuses, fine fibers of. The columnar, mucous-secreting epithelium of the endocervical mucosa then transitions to the relatively smooth squamous epithelium, which lines the ectocervical portion(Fig. (B) Photomicrograph. At the next stage of cDC differentiation, the MDP generates CD117lo CX3CR1+ CD135+ CD115+ DC committed progenitors, termed common DC progenitors (CDPs) (Onai etÂ al., 2007) or pro-DCs (Naik etÂ al., 2007).Â The CDPs generated from MDPs have lost their potential toÂ generate cells of the monocyte/mÏ lineage andÂ nextÂ differentiate into either CD117âCX3CR1â CD135+CD115âCCR9+CD11cintB220+Ly6C+ pDCs through a CCR9â pre-pDC intermediate (Schlitzer etÂ al., 2011, 2012) or into CD117âCX3CR1+CD135+CD115âCD11cint SIRPÎ±int precursors of cDCs (pre-cDCs) (Naik etÂ al., 2007). Start studying Tissue labeling. The lamina propria of the corpus is more fibrous compared to the uterine horns. Monocytes and macrophages are motile, yet become highly adherent upon phagocytic activity. Still other activated B cells turn into quiescent memory B cells and become part of the bodyâs immunological memory bank. Areolar Connective Tissue: Adipose Tissue: Reticular Connective Tissue: LABEL: fibroblast cell. When viewed with an electron microscope, the unit fibrils of reticular fibers show the same banding pattern as the unit fibrils of type I collagen fibers even though they are different in structure in terms of number, diameter, and pattern of arrangement of the unit fibrils. Reticular tissue provides a very delicate meshwork that serves as a scaffold to other tissues and also supports other cells and tissues. O.Z. Mesenchymal villi have diameters between 40 and 80Â Î¼m and show two-layered villous trophoblast coverage with the syncytiotrophoblast and a clear layer of villous cytotrophoblast (Fig.Â 2A). The presence of the lineage restricted pre-cDC1s was also confirmed in a separate study, which identified the progenitors to be CD24+ fitting with the earlier analysis (Grajales-Reyes etÂ al., 2015). 17.13 and 17.16). 8.14). In general, these potent vasodilators cause contraction of nonvascular smooth muscle, increased vascular permeability, and pain. Due to the affinity of reticular fibers for silver salts, reticular fibers are sometimes called argentophil fibers this is probably due to the more carbohydrates contained in reticular fibers than Type I fibers. Dendritic cells play an important functional role, especially within the cortex. Hence, mesenchymal villi are the forerunners of all other villous types. Endothelial cells are elongated and lie parallel to the long axis of the vessel. Veins of the pulp enter the trabeculae as trabecular veins which are continuous with the splenic vein which lies outside the organ. It also serves as a reservoir of. The function of terminal villi is the direct exchange between mother and fetus across the placental barrier. On the other hand, cases with growth restricted babies and reduced blood flow in the umbilical arteries leads to an increase in placental oxygen concentrations (Sibley etÂ al., 2002) followed by regression and thus decreased numbers of terminal villi. After antigenic stimulation, lymphoid follicles, now called secondary lymphoid follicles, develop a lighter staining germinal center that consists predominantly of activated B cells with increased amounts of cytoplasm (Fig. The villous trophoblast of stem villi is quite thin with low numbers of villous cytotrophoblasts. Peppas, in Encyclopedia of Materials: Science and Technology, 2010. The sinus pore size can vary between species, and the morphology and degree of fenestration can change in certain disease processes, such as cirrhosis. proudly created with wix.com. Within these intermediate villi an increased longitudinal growth of vessels results in protrusions of vessels covered by villous trophoblast, terminal villi (Fig.Â 2D). 17.14B). Structure of a lymph node. In addition, the cellular endometrial stroma gradually becomes more fibrous, similar to that seen in rodents. The vaginal fornix (VF) is shown. The thymus weighs about 0.32â0.39 g (0.4% of bodyweight) in neonates; it increases in weight and size, and undergoes progressive involution in which the thymic tissue is successively replaced by connective and adipose tissue, starting in the fourth month post partum. Macrophages are terminally differentiated, long-lived monocytes residing in, The feline thymus is an elongated multilobed structure located in the thoracic mediastinum. - ground substance is a gel like matrix that surrounds the cells and fibers of the tissue. pDCs then directly enter peripheral tissues through the bloodstream where they produce high levels of type 1 interferon in response to viral infections. For example, filamentous micelles up to 8Â Î¼m in length and only 60Â nm in thickness could circulate in the blood up to a week, much longer than any conventional spherical formulation and on a time scale more attractive for sustained release. LABEL: fat storage area. (B) The transformation zone changes in position during various hormonal stages but is composed of metaplastic squamous cells and endocervical cells. Berthold Huppertz, in Encyclopedia of Reproduction (Second Edition), 2018. The opposite (convex) surface receives afferent lymphatic vessels. Due to their size about 20%â25% of the villous volume at term can be attributed to this villous type. Each stage of pregnancy can be defined by a specific subset of villous types. Dense connective tissue, also called dense fibrous tissue, is a type of connective tissue with fibers as its main matrix element. Loose connective tissues provide support, flexibility, and strength required to support internal organs and structures such as 7.28) Reticular connective tissue is present in the liver, spleen, lymph nodes, thymus, tonsils, bone marrow and lamina propria of the gut wall. Tight junctions (zonulae occludens) of the retinal endothelium provide a barrier to macromolecule diffusion from blood vessels that is additionally supported by a discontinuous layer of surrounding cells with smooth-muscle characteristicsâpericytesâand by basement membrane of MÃ¼ller cells and astrocytes. 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