adherens junctions

Examples of adherens junctions in the following topics:

• Adherens Junctions

  • Adherens junctions are also referred to as zonula adherens, intermediate junction, or as belt desmosomes. 
  • While other junctions, like tight junctions, provide some support for and fusion of adjacent cells, their resistance to mechanical stress is relatively small compared to the much stronger adherens junctions. 
  • This means that the functional as well as morphological integrity of the adherens junctions are calcium dependent.
  • These are the principal interactions of structural proteins at a cadherin-based plasma membrane adherens junction.
  • Actin filaments are associated with adherens junctions in addition to several other actin-binding proteins.

• Gap Junctions

  • A gap junction is a specialized cell junction that directly connects the cytoplasm of two cells.
  • Gap junctions are also called communicating junctions, macula communicans, or nexuses. 
  • The channels in a gap junction aren’t always open. 
  • Gap junctions are found in many places throughout the body. 
  • Intercalated disks consist of three different types of cell–cell junctions: actin filaments anchoring adherens junctions, intermediate filaments anchoring desmosomes, and gap junctions.

• Microscopic Anatomy

  • Intercalated discs are gap junctions that link cardiomyocytes so that electrical impulses (action potentials) can travel between cells.
  • In a more general sense, an intercalated disk is any junction that links cells together between a gap in which no other cells exist, such as an extracellular matrix.
  • Intercalated discs consist of three types of cell-cell junctions, most of which are found in other tissues besides cardiac muscle:
  • Gap junctions, which connect proteins to the cytoplasm of different cells and transmit action potentials between both cells, required for cellular depolarization.

• Desmosomes

  • A desmosome is a type of cell junction that attaches to keratin in the cytoplasm and is a localized structure adjoining two cells.
  • A desmosome , also known as macula adherens, is a type of cell junction that attaches to filaments of keratin in the cytoplasm and is characterized by a localized patch that holds two cells tightly together.
  • A desmosome, also known as macula adherens (Latin: adhering spot), is a cell structure specialized for cell-to-cell adhesion in animal cells.
  • A type of junctional complex, they are localized spot-like adhesions randomly arranged on the lateral sides of plasma membranes.

• The Junction Rule

  • Kirchhoff's junction rule states that at any circuit junction, the sum of the currents flowing into and out of that junction are equal.
  • Kirchhoff's junction rule states that at any junction (node) in an electrical circuit, the sum of the currents flowing into that junction is equal to the sum of the currents flowing out of that junction.
  • Kirchhoff's junction law is limited in its applicability.
  • This flow would be a current, thus violating Kirchhoff's junction law.
  • Kirchhoff's Junction Law illustrated as currents flowing into and out of a junction.

• Intercellular Junctions

  • Plasmodesmata are junctions between plant cells, whereas animal cell contacts are carried out through tight junctions, gap junctions, and desmosomes.
  • Lastly, similar to plasmodesmata in plant cells, gap junctions are the third type of direct junction found within animal cells.
  • Structurally, however, gap junctions and plasmodesmata differ.
  • Gap junctions are particularly important in cardiac muscle.
  • Proteins create tight junction adherence.

• Tight Junctions

  • That zipper is like a tight junction (TJ), also called an occluding junction.
  • This is why tight junctions are also called zonula occludens. 
  • Tight junctions are located within our body’s epithelia. 
  • A tight junction—a kind of symmetrical cell junction—is composed of numerous important proteins that are either directly involved in its composition or intimately involved with connecting the tight junction to and between the cells in one way or another. 
  • An electron micrograph showing a tight junction in rat kidney tissue.

• Peripheral Motor Endings

  • A neuromuscular junction exists between the axon terminal and the motor end plate of a muscle fiber where neurotransmitters are released.
  • A neuromuscular junction is the synapse or junction of the axon terminal of a motor neuron with the motor end plate, as shown in Figures 1 and 2.
  • In vertebrates, the signal passes through the neuromuscular junction via the neurotransmitter acetylcholine.
  • Electron micrograph showing a cross section through the neuromuscular junction.
  • The arrow shows junctional folds with basal lamina.

• Ascending Aorta

  • The ascending aorta is the first portion of the aorta; it includes the aortic sinuses, the bulb of the aorta, and the sinotubular junction.
  • The aortic root is the portion of the ascending aorta beginning at the aortic annulus, the fibrous attachment between the heart and the aorta, and extending to the sinotubular junction.
  • The sinotubular junction is the point in the ascending aorta where the aortic sinuses end and the aorta becomes a tubular structure.
  • At the junction of the ascending aorta with the aortic arch, the caliber of the vessel increases with a bulging of its right wall.

• Doping: Connectivity of Semiconductors

  • When we place p-type and n-type semiconductors in contact with one another, a p-n junction is formed. p-n junctions are basic components of most common electrical devices.
  • In this scenario, electrons flow from the anode toward the cathode pole and charge flows across the junction.
  • The p-n junction forms between juxtaposed p- and n-type semiconductors.
  • The free electrons from the n-type semiconductor combine with the holes in the p-type semiconductor near the junction.
  • There is a small potential difference across the junction.