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Cells, tissues, organs, organs systems and organs apparatus

Cells, tissues, organs, organs systems and organs apparatus

Cell (cellula) is a microscopic formation, elementary particle of a living organism, but is a complex system that contains the nucleus and cytoplasm. The sizes of the cells are from a few micrometers to 200 micrometers. Cell shape is different (spherical, spindle-shaped, flat, cubic, prismatic, cylindrical, star-shaped, with spikes). Cell structure is difficult. Externally, every cell has a membrane - cytolemma (plasmolema). Cytolemma - is a semi-permeable membrane through which performes the transport of substances and the interaction of cells with neighboring cells and intercellular substance. In the cell is contained nucleus, which is involved in protein synthesis and keeps genetic information. The core is covered with shell - cariolema. The core filled nucleoplasm (carioplasma), which have 1-2 nucleolus and chromatin. Around the core is placed cytoplasm. The composition of the cytoplasm included cytosol, organelles and cytoplasmic inclusions. Cytosol - is free of organelles substance of cytoplasm semi-liquid, semi-transparent, is involved in the metabolism. Organelles - constant part of cells that perform specific functions.

Organelles include:
- Mitochondria - the energy cell organelles are involved in the processes of oxidation, phosphorylation;
- Internal mesh apparatus (lamellar complex or Golgi apparatus), which consists of vesicles, plates, tubes, synthesize polysaccharides is involved in removing of products of its life to outside of the cell;
- Cytoplasmic (endoplasmic) grid - formed by tubes and plates. Non-granular cytoplasmic grid involved in the metabolism of lipids and polysaccharides. Granular cytoplasmic grid contains spherical granules - ribosomes and their clusters - polysomes (polyribosomes). Granular cytoplasmic grid is involved in protein synthesis. Cytoplasmic inclusion - is the accumulation of various substances (protein, fat, pigment and others creations).

The organism and its integrity

Organism (from the Greek. Organon - organ) is defined as any whole alive plant or animal, including the man. The main properties of the organism are: constant exchange of substances and energy (internal and with the environment), self-renewal, movement, reactivity, self-development and growth , heredity and variability, adaptability to conditions of existence. The more complex the structure of the body, the better it retains constant internal environment (homeostasis (body temperature, blood biochemical composition, etc)) regardless of environmental conditions. For human, unlike animals, external factors of the leading importance attaches to socio-economic conditions.

The evolution of the animals occurred by increase in the level of life organization: molecular, cytoplasmic (unicellular protozoa), cell (sponge), tissue organisms (coelenterates), higher animals (with complex of organs). Evolution included two opposite processes: differentiation or division of the body for tissues, organs, systems of organs(with appropriate and the simultaneous distribution and specialization of functions) and integration, or combining of pieces into an integral organism, sealed humoral and neural connections. The highest organisms, including man, preferably is inherent a system level of performance. The presence other levels of functioning is not disputed but they have a subordinate character.

Man in Nature

Modern man in the classification system of animal organisms belongs to the type of chordates (Chordata), a subtype of vertebrates (Vertebrata), the class of mammals (Mammalia), a number of primates (Primates), friendly of people (Hominidae), kind of man (Homo), species Homo sapiens (Homo sapiens). The human body keeps a general structure, inherent in all vertebrates: bilateral symmetry, the prevalence of paired organs, the presence of the axial skeleton, saving some (relic) signs of segments (metamerism), better detected in primitive form. These and many other features (reduced state of smell saved some rudiments of caudal vertebrae, the presence of the rudiments of the third eyelid, etc.) testify to ways the evolution past zoological ancestors.

The main morphological features of the human body compared to other primates body include: functional forelimbs (in human upper limb - arm), high growth and differentiation of the mantle (cortex) of the brain, a significant weakening of the jaw apparatus, equal number of teeth, lack of overall hair , upright posture, prolonged childhood and so on. Modern man owns expressive language, interconnected with abstract thinking (development of the second signal system). However, the main distinguishing feature between man and animal is that people - a social being, the main condition and formation of life is socially useful labor, is closely associated with the emergence of society.