TISSUS

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Cells are the smallest living units. In the human body, they are grouped into ordered sets that are TISSUE. These materials are used for training and ORGAN SYSTEMS. A tissue is a set of differentiated cells in the same manner, and their derivatives, for the production of one or more similar functions. The performance of a function requires a particular specialization. In organs and systems, there are still several types of tissues, yet one class predominates.

EPITHELIAL TISSUE: The Epithelia are tight assemblies of cells that line the external surfaces and (or) internal organs, forming one or more layers:

The top layer of skin, called the epidermis, is also an epithelium. Not being irrigated by blood, exchange of substances are the cell to the interstitial space and vice versa. The glands are groups of epithelial cells or organs, which are processed in the growth of the embryo.

This is the largest category. The cells are arranged so that they form a wide-mesh network, a cellular sponge loose, which spaces are engorged with interstitial fluid substance containing salts and proteins. Adult connective tissue is composed of two categories:

b) TIGHT: Compose the LIGAMENTS (bone-os link) and TENDONS (muscle-bone connection):

Another category of connective tissue, is closed by CARTILAGES, such as nose and ears ... They are composed of cartilaginous cells, connective fibers and ground substance, which gives them great strength and excellent resistance to tearing. Cartilages are not irrigated.

Just like a house, the structure of the Human Body is built on and around a solid framework: the SKELETON. This is the locomotor liabilities. About 206 bones make up the skeleton, which represents about 25% of the total weight of the Human Body. It consists of two very distinct tissues: the OS and CARTILAGE. Bones are classified into different families:

THE OSSEOUS TISSUE: It consists of cells encompassed in a hard substance the ossein. It consists of about 40% of a fibrous protein called: Collagen. Without collagen, bone would also brittle as glass. Other substances that make up the structure of bone tissue, are the Mineral Salts, mainly Calcium and Phosphate. Without minerals, the bones would be as flexible as a rubber toy.

The microstructure of the bone is in the form of concentric layers of cells, LAMELLES surrounding galleries Called: Canals of Havers. These channels protect blood vessels and nerves. The fabric compact (dense), is covered by a layer of osteogenic tissue (which makes the bone) and the hard shell of a: PERIOSTEUM. Depending on whether the structure is very dense and convoluted, it is compact or spongy tissue. This type of fabric is especially present where bone undergoes less stress. Its cells are occupied by a soft, fatty substance: bone marrow. Marrow plays an essential role in the production of red blood cells.

THE MUSCLE TISSUE: The special connective tissue are determined by the interstitial substances. In muscle tissue, it is the internal structures PROTEINSwhich confer the ability to actively shorten: CONTRACTILITY. Muscle tissue is composed of many muscle cells called myofibrils or Muscular fibrils. They are in bundles by loose connective tissue. The bundles are grouped by connective tissue to form the MUSCLE. The muscle surface is covered with a conjunctival blade much more resistant, called DUCT MUSCLE or Fascia.

It forms the muscular layer of vessels and hollow organs (stomach, intestines peristalsis =). Its contraction is slow, involuntary, rhythmic and autonomous. Influence of the autonomic nervous system.

Composed of clear disks juxtaposed with dark disks visible under the microscope, at low power. It consists of long fibers, containing many CORES, located on the outskirts. Its contraction is fast, depends on the will, does not match any rate, it is dependent on the cerebro-spinal nervous system.

Has properties both of the smooth muscle and striated muscle. The cell nucleus is central, the fibers are striated and are interconnected networks. Heart contractions are rapid, involuntary, rhythmic and autonomous. Under the influence of the autonomic nervous system.

COMPOSITION of Physique: Contractile proteins are composed of elements; nutrients consist of carbon hydrates, glucose (liquid blood), glycogen (the body stock), and the dye: myoglobin (red) that is the subject oxygen; waste which include lactic acid and creatinine.

NERVOUS TISSUE: Our body is equipped from head to toe, a network of nerves that control activities and sensations. The total length of peripheral nerves of the body is 150 000 km!! There are 43 pairs of main connections between the central nervous system (CNS) and the peripheral nervous system (PNS), and 12 pairs between the CNS and PNS in the brain. The maximum voltage of nerve impulses is 100 mV. The largest nerve of the body are the spinal cord that is 45 cm long and 3.8 cm wide, and the tibial nerve, which measures 50 cm. The largest nerve after spinal cord, sciatic is 2 cm.

The functional unit of the nervous tissue is the NEURON, connected by GLIA or névrolgie fabric providing support and metabolic exchange of the central nervous system:

The nerve cell differs from other cells of the body, its ramifications and the particular character of its membrane. These ramifications are of two types: AXONS and DENDRITES:

The membrane of the nerve cell, which surrounds its ramifications throughout their length, has the distinction of being excitable, which allows him to convey electrochemical impulses. The nerves transmit these impulses, but not in direct contact with each other. Nerve impulses are gathered by Dendrites and transmitted to the axon they follow to its end. There, between the membrane of the axon and a dendrite of a neighboring neuron, is inserted a kind of lock, the SYNAPSE, which specialized molecules ensure the transmission of nerve impulses:

In this narrow range, also called intersynaptic space, molecules called neurotransmitters or chemical messengers, cross the space intersynaptic one thousandth second! The nerve impulse continues its journey through the same process, to of the neighboring nerve dendrites its axon.