Intercellular connections (pins)

Plasmolemma metazoan organisms has been actively involved in the formation of special structures - intercellular junctions (junctiones intercellulares), providing intercellular interactions. There are several types of such structures.

Simple intercellular junctions, (junctio intercellularis simplex) - convergence plasmolemma neighboring cells at a distance of 15-20 nm. In this case, there is an interaction glycocalyx layers of neighboring cells. A variety of simple compounds is "fingered" or connection type lock.

Tight connection (locking zone) (zonula occludens) - the area where the two layers plasmolemma close together as possible, here it is as if the merger sites plasmolemma two neighboring cells. Role tight closing compound is mechanically connecting cells with each other. This area is impermeable to macromolecules and ions, and therefore, it closes, separates the intercellular gap (and with them their own internal environment of the body) from the external environment.

It often occurs, especially in the epithelium, a special type of connection - spot clutch or desmosomes occur (desmosoma). This structure represents a small area, sometimes having a layered form, to a diameter of 0.5 microns, which zone is located between the membranes with a high electron density. By plasmolemma zone by desmosomes portion adjacent cytoplasm elektronnoplotnogo substance so that the inner layer of the membrane appears thickened. Underneath this bulge region is thin fibrils, which can be shipped in a relatively dense matrix. The functional role of desmosomes is mainly in mechanical communication between cells.

Slit connection, or nexus (nexus), is an area of 0.5-3 length of synaptic connections, or synapses (synapsis). This type of connection is characteristic of the nervous tissue and is found in specialized areas of contact between two neurons or between a neuron and any other element forming part of the receptor or effector (eg, neuromuscular, neuro-epithelial synapses). Synapses - contacts between the two parts of cells specialized for one-way transfer of excitation or inhibition from one element to another. The structure of the synapse is also seen in the subject nerve endings.

Some terms:

organelle(gr. organon gun, body + c. -eides like; syn. organelle) - constant cytoplasmic structures of animal or plant cell that performs a specific function (eg., mitochondria, ribosome, the cell center);

phagocytosis (phagocytosis; phagocyte -oz +) - the process of grasping and active absorption of microorganisms, destroyed cells and foreign particles from single-celled organisms or special cells (phagocytes) multicellular organisms;

pinocytosis (pinocytosis; Gr. pineo- drink, absorb + GIST. cytus cell -oz +) - the active uptake of fluid from the environment to the formation of cytoplasmic vesicles containing liquid;

exocytosis(exo + GIST. cytus cell -oz +) - the process of allocating the cell material in the form of secretory granules or vacuoles;

secretion (secretio; Lat. "branch", "selection") - the process of developing cell secretion and release it to the surface epithelium or in the internal environment of the body;

excretion (lat. excerno, excretum, to separate, to allocate, from ex- + cerno - distinguish sifting; syn. selection) - a set of physiological processes to relieve the body of the end products of metabolism of foreign substances and excess water, mineral and organic compounds received food or formed in the body during metabolism;

excreta (lat. excerno, excretum separate, allocate) - the end product of metabolism, secreted by the body;

Test questions:

1. Ultrastructural structure of the outer cell membrane

2. The organization and functions of the glycocalyx

3. Mechanisms of penetration of substances through the cell membrane

4. Types of intercellular contacts

5. The structure of cell-cell contacts