EPITHELIAL TISSUE PDF
Terms that help us understand what kinds of tissues we are identifying: Terms referring to the layers. Simple = one layer. Stratified = more than. Most epithelial tissues are essentially large sheets of cells covering all the surfaces of the body exposed to the outside world and lining the outside of organs. Is avascular tissue (without blood supply – cells receive nourishment by diffusion from a highly vascular area of loose connective tissue just below the basement.
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General Considerations. ➢ Classification of epithelial tissues. ❖ Lining and covering epithelia. ▫ Form the boundary between external environment and body. Types of Tissue. • Epithelial Tissue. • Connective Tissue. • Muscle Tissue. • Nervous Tissue. 1. Properties of Epithelia. • Cellularity. • Polarity. • Avascularity. (1) COVERING EPITHELIUM. • It is one type of the epithelial tissue which covers the body surface from outside and lines its cavities from inside. • It can be.
In addition, E2 induces epithelial cell hypertrophy and keratin-mediated differentiation via stimulation of Krt6 and Krt10 production. A lack of epithelial ESR1 causes excess Il1b and Il8 levels in the vaginal tissue leading to increased recruitment of neutrophils. Elevated neutrophil levels in the vaginal tissues result in excessive MMP activity and subsequent extracellular matrix ECM modification.
In the absence of ESR1, Muc1 and Muc4 levels are increased, causing an overproduction of glycoproteins in the apical membrane. Moreover, the epithelial cells are unable to produce Krt6a and Krt10, leading to an undifferentiated epithelial layer. These aberrant ECM modifications and undifferentiated epithelial layer leads to a loss of epithelial tissue integrity, and cells are easily detached from the stroma during mating. Ly6G-positive staining confirmed that a majority of the leukocytes were indeed neutrophils.
However, further investigation is needed to identify the different immune cell types in the presence or absence of epithelial ESR1 in the vagina. Some lesions were severe, resulting in a complete detachment of the vaginal epithelium. Based on these results, a lack of epithelial ESR1 results in an extremely fragile vaginal epithelium that can be easily damaged by physical stress, such as mating.
Cell atrophy contributes to vaginal dryness and sexual dysfunction in postmenopausal women It is established that E2 induces cell hypertrophy in the uterus This finding suggests that local epithelial ESR1 signaling is necessary to induce vaginal cell hypertrophy. Cell proliferation is essential for tissue growth. We previously reported that stromal, but not epithelial, ESR1 in the uterus is required for epithelial cell proliferation 22 , We speculated that vaginal epithelial cell proliferation is also dependent on stromal ESR1 signals, since the proliferation was indeed independent of epithelial ESR1 expression during estrus.
However, an increased proliferation index at 0. It is highly likely that differentiating cells detached prematurely before they could terminally differentiate into cornified cells, or detached due to physical stress during mating. Based on these observations, a loss of epithelial ESR1 led to a reduced number of non-proliferating cells and an increased proliferating index at 0.
In , Long and Evans described the cyclic pattern of the rat vaginal epithelium Since then, the process of vaginal keratinization has been studied extensively and determined to be induced by E2. Keratin 6, 10, 13, and 16 are involved in the keratinization process 29 , 30 , 31 , 32 , Krt6a is a type 2 keratin, associated with pachyonychia congenita Krt10 is a type 1 keratin and a mutation in Krt10 is associated with hyperkeratosis 36 , Pachyonychia congenita and hyperkeratosis are rare autosomal dominant disorders, and the mutated keratin proteins impair the compaction of the stratum corneum of the skin.
Therefore, reduction in Krt6a and Krt10 expressions may contribute to the absence of the cornified layer and a loss of cellular integrity in the vaginal epithelium. In contrast to keratinization, vaginal mucification is triggered by changes in circulating levels of P4 and E2 39 , High levels of P4 oppose E2-induced action resulting in mucification — a production of glycoproteins including mucins. Mucins are the major barrier molecules in the reproductive mucosa.
Two members of the mucin family, mucin 1 and 4 are expressed in human vaginal epithelium Our findings are consistent with the previous report that suppression of ESR1 activity caused aberrant induction of MUC1 production in the mouse uterus Thus, we conclude that epithelial ESR1 in the vaginal tissue is required for normal keratinization and mucification processes. The host defense system of the lower female reproductive tract is composed of epithelial layers, the immune system, vaginal flora, low pH, and mucus in the CVF.
The dynamic immune system responds to sex hormones and physical stimuli. In women, elevated E2 during the proliferative phase suppresses mucosal immunity, creating a window of vulnerability for infection 6. In rodents, an increased risk of infection in the lower female reproductive tract is also associated with increased levels of E2 43 , 44 , Our data are consistent with these findings as gram-positive bacterial colonies were present in vaginal smears during the estrus stage of control animals.
At estrus, the absence of leukocytes in the vaginal lumen allows the growth of bacteria colonies during this window of vulnerability 6.
In contrast, a loss of epithelial ESR1 caused excessive leukocyte infiltration throughout all stages of the estrous cycle, resulting in a lack of gram-positive bacterial colonies.
Thus, it is possible that the ovarian cycle provides a window of recovery in the female reproductive tract, allowing the tissue to grow and normal flora to colonize in an environment with minimal immunosuppression. Cells within the mucus were distorted or elongated It is established that excessive neutrophil activity has a negative impact on tissue health, primarily due to hyperactivity of neutrophil elastase NE 46 , a proteinase that degrades epithelial cadherin resulting in a loss of tissue integrity In the lung, NE reduces respiratory epithelial integrity.
Simple epithelial tissue is organized as a single layer of cells and stratified epithelial tissue is formed by several layers of cells. Simple Epithelium The shape of the cells in the single cell layer of simple epithelium reflects the functioning of those cells. The cells in simple squamous epithelium have the appearance of thin scales. Squamous cell nuclei tend to be flat, horizontal, and elliptical, mirroring the form of the cell.
The endothelium is the epithelial tissue that lines vessels of the lymphatic and cardiovascular system, and it is made up of a single layer of squamous cells. Simple squamous epithelium, because of the thinness of the cell, is present where rapid passage of chemical compounds is observed.
The alveoli of lungs where gases diffuse, segments of kidney tubules, and the lining of capillaries are also made of simple squamous epithelial tissue.
Histology Epithelium — Functions and Types of Epithelial Tissue
The mesothelium is a simple squamous epithelium that forms the surface layer of the serous membrane that lines body cavities and internal organs.
Its primary function is to provide a smooth and protective surface. Mesothelial cells are squamous epithelial cells that secrete a fluid that lubricates the mesothelium. In simple cuboidal epithelium, the nucleus of the box-like cells appears round and is generally located near the center of the cell. These epithelia are active in the secretion and absorptions of molecules.
Simple cuboidal epithelia are observed in the lining of the kidney tubules and in the ducts of glands. In simple columnar epithelium, the nucleus of the tall column-like cells tends to be elongated and located in the basal end of the cells.
Like the cuboidal epithelia, this epithelium is active in the absorption and secretion of molecules. Simple columnar epithelium forms the lining of some sections of the digestive system and parts of the female reproductive tract.
Ciliated columnar epithelium is composed of simple columnar epithelial cells with cilia on their apical surfaces. These epithelial cells are found in the lining of the fallopian tubes and parts of the respiratory system, where the beating of the cilia helps remove particulate matter. Pseudostratified columnar epithelium is a type of epithelium that appears to be stratified but instead consists of a single layer of irregularly shaped and differently sized columnar cells.
In pseudostratified epithelium, nuclei of neighboring cells appear at different levels rather than clustered in the basal end. The arrangement gives the appearance of stratification; but in fact all the cells are in contact with the basal lamina, although some do not reach the apical surface.
Pseudostratified columnar epithelium is found in the respiratory tract, where some of these cells have cilia. Both simple and pseudostratified columnar epithelia are heterogeneous epithelia because they include additional types of cells interspersed among the epithelial cells.
Figure 3. Goblet Cell. Stratified Epithelium A stratified epithelium consists of several stacked layers of cells.
Epithelial Tissue - Overview PDF
This epithelium protects against physical and chemical wear and tear. The stratified epithelium is named by the shape of the most apical layer of cells, closest to the free space.
Stratified squamous epithelium is the most common type of stratified epithelium in the human body.
The apical cells are squamous, whereas the basal layer contains either columnar or cuboidal cells. The top layer may be covered with dead cells filled with keratin. Mammalian skin is an example of this dry, keratinized, stratified squamous epithelium. The lining of the mouth cavity is an example of an unkeratinized, stratified squamous epithelium.
Stratified cuboidal epithelium and stratified columnar epithelium can also be found in certain glands and ducts, but are uncommon in the human body. Etournay, A. Sagner, J. Roeper, C. Collinet, Q.
Mao, J. Sedzinski, and the Dahmann team. References 1.This epithelium protects against physical and chemical wear and tear. The endothelium is the epithelial tissue that lines vessels of the lymphatic and cardiovascular system, and it is made up of a single layer of squamous cells.
In the absence of ESR1 in the vaginal epithelial tissue, we also observed an excess of neutrophil infiltration, regardless of the estrous cycle stage. At estrus, the P4 level is elevated but will gradually decline towards the end of the cycle.
An anchoring junction includes several types of cell junctions that help stabilize epithelial tissues. The top layer may be covered with dead cells filled with keratin.