Title: Tight junction
Content: Tight epithelia have tight junctions that prevent most movement between cells. Examples of tight epithelia include the distal convoluted tubule, the collecting duct of the nephron in the kidney, and the bile ducts ramifying through liver tissue. Other examples are the blood-brain barrier and the blood cerebrospinal fluid barrier ; Leaky epithelia do not have these tight junctions, or have less complex tight junctions. For instance, the tight junction in the kidney proximal tubule, a very leaky epithelium, has only two to three junctional strands, and these strands exhibit infrequent large slit breaks. Epithelia are classed as "tight" or "leaky", depending on the ability of the tight junctions to prevent water and solute movement:
Title: Tight junction
Content:  Tight junctions, also known as occluding junctions or zonulae occludentes (singular, zonula occludens) are multiprotein junctional complexes whose canonical function is to prevent leakage of solutes and water and seals the paracellular pathway. Tight junctions may also serve as leaky pathways by forming selective channels for small cations, anions, or water. Tight junctions are present mostly in vertebrates (with the exception of Tunicates ). The corresponding junctions that occur in invertebrates are septate junctions.
Title: Cell–cell interaction
Content:  Tight junctions are multi-protein complexes that hold cells of a same tissue together and prevent movement of water and water-soluble molecules between cells. In epithelial cells, they function also to separate the extracellular fluid surrounding their apical and basolateral membranes. These junctions exist as a continuous band located just below the apical surface between the membranes of neighboring epithelial cells. The tight junctions on adjacent cells line up so as to produce a seal between different tissues and body cavities. For example, the apical surface of gastrointestinal epithelial cells serve as a selective permeable barrier that separates the external environment from the body. The permeability of these junctions is dependent on a variety of factors including protein makeup of that junction, tissue type and signaling from the cells. Tight junctions are made up of many different proteins. The four main transmembrane proteins are occludin, claudin, junctional adhesion molecules (JAMs) and tricellulins. The extracellular domains of these proteins form the tight junction barrier by making homophilic (between proteins of the same kind) and heterophilic interactions (between different types of proteins) with the protein domains on adjacent cells. Their cytoplasmic domains interact with the cell cytoskeleton to anchor them.
Title: Tight junction proteins
Content:  TJ proteins could be divided in different groups according to their function or localization in tight junction. TJ proteins are mostly described in the epithelia and endothelia but also in myelinated cells. In the central and peripheral nervous system are TJ localized between a glia and an axon and within myelin sheaths, where they facilitate the signaling. Some of TJ proteins act as a scaffolds, that connect integral proteins with the actin in a cytoskeleton. Others have an ability to crosslink junctional molecules or transport vesicles through the tight junction. Some submembrane proteins are involved in the cell signaling and gene expression due to their specific binding to the transcription factor. The most important tight junction proteins are occludin, claudin and JAM family, that establish the backbone of tight junction and allow to passing of immune cells through the tissue.
Title: Tight junction
Content: They provide epithelial and endothelial cell sheets with barrier function, which can be further subdivided into protective barriers and functional barriers serving purposes such as material transport and maintenance of osmotic balance: ; Tight junctions prevent the passage of molecules and ions through the space between plasma membranes of adjacent cells, so materials must actually enter the cells (by diffusion or active transport) in order to pass through the tissue. Investigation using freeze-fracture methods in electron microscopy is ideal for revealing the lateral extent of tight junctions in cell membranes and has been useful in showing how tight junctions are formed. The constrained intracellular pathway exacted by the tight junction barrier system allows precise control over which 
Title: Cell adhesion
Content:  Tight junctions are normally present in epithelial and endothelial tissues, where they seal gaps and regulate paracellular transport of solutes and extracellular fluids in these tissues that function as barriers. Tight junction is formed by transmembrane proteins, including claudins, occludins and tricellulins, that bind closely to each other on adjacent membranes in a homophilic manner. Similar to anchoring junctions, intracellular domains of these tight junction proteins are bound with scaffold proteins that keep these proteins in clusters and link them to actin filaments in order to maintain structure of the tight junction. Claudins, essential for formation of tight junctions, form paracellular pores which allow selective passage of specific ions across tight junctions making the barrier selectively permeable.
Title: Stress fiber
Content:  Tight junctions, or zona occludens, are the most important cellular element for the formation of semi-permeable barriers within or between tissues. Tight junctions primarily consist of claudins and occludins, which are membrane proteins that form the cell-cell contact, as well as ZO-1, ZO-2 and ZO-3, which link tight junctions to the actin cytoskeleton. However, tight junctions have not been found to be directly linked to stress fibers, like they are for focal adhesions and adherens junctions.
Title: Intercellular cleft
Content:  Endothelial tight junctions are most commonly found in the intercellular cleft and provide for regulation of diffusion through the membranes. These links are most commonly found in the most apical aspect of the intercellular cleft. They prevent macromolecules from navigating the intercellular cleft and limit the lateral diffusion of intrinsic membrane proteins and lipids between the apical and basolateral cell surface domains. In the intercellular clefts of capillaries, tight junctions are the first structural barriers a neutrophil encounters as it penetrates the interendothelial cleft, or the gap linking the blood vessel lumen with the subendothelial space2. In capillary endothelium, plasma communicates with the interstitial fluid through the intercellular cleft. Blood plasma without the plasma proteins, red blood cells, and platelets pass through the intercellular cleft and into the capillary7.
Title: Intestinal epithelium
Content:  Tight junctions, also called zonula occludens, are the most important components of the intestinal epithelium for its barrier function. These complexes, formed primarily of members of the claudin and the occludin families, consist of about 35 different proteins, form a ring shaped continuous ribbon around the cells, and are located near the borders of the lateral and apical membranes. The extracellular domains of the transmembrane proteins in adjacent cells cross connect to form a tight seal. These interactions include those between proteins in the same membrane ("cis") and proteins in adjacent cells ("trans"). In addition, interactions can be homophilic (between identical proteins) or heterophilic (between different proteins). Similar to adherens junctions, the intracellular domains of tight junctions interact with different scaffold 
Title: Tight junction
Content:  composed of a branching network of sealing strands, each strand acting independently from the others. Therefore, the efficiency of the junction in preventing ion passage increases exponentially with the number of strands. Each strand is formed from a row of transmembrane proteins embedded in both plasma membranes, with extracellular domains joining one another directly. There are at least 40 different proteins composing the tight junctions. These proteins consist of both transmembrane and cytoplasmic proteins. The three major transmembrane proteins are occludin, claudins, and junction adhesion molecule (JAM) proteins. These associate with different peripheral membrane proteins such as ZO-1 located on the intracellular side of plasma membrane, which anchor the strands to the actin component of the cytoskeleton. Thus, tight junctions join together the cytoskeletons of adjacent cells. Transmembrane proteins: 

Question: where can tight junctions be found in the body?
Answer: Internal epithelia.
the cytoskeletons of adjacent cells.