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Epithelial tissues Epithelia are the linings of internal and external surface and body cavities, including ducts carrying secretion from glands. They are composed of several layers of cells called epithelia or just a single layer known as simple epithelia. The lowest or the bottom layers of cells are attached to a basement membrane for support and connection. The basement membrane is secreted by the epithelial cells. There are nerve supplies to epithelia but they are supplied with oxygen and nutrients from deeper tissues by diffusion. As they are surface tissues and exposed to fraction, their capacity for growth and repair is grater than other tissues and usually occurs during sleep. Simple epithelia Simple epithelia serve many roles in various body locales. As components of serous and synovial membranes, simple epithelia secrete fluids that lubricate tissues to minimize friction as organs or other body structures rub against one another. Other simple epithelia line body tracts as protective, absorptive, or secretory cells. All glands of the body are constructed of epithelial cells as are the ducts that connect the exocrine types to body surfaces. As linings in the alveoli (air sacs), kidneys, and blood vessels, simple squamous types assist in diffusion, osmosis and filtration phenomena. As linings and covering on all external and internal body surfaces, epithelia serve as the "first line of defence" against microbial invasions. ...read more.


Cells Cartilage Cartilage is a specialized connective tissue that provides for both strength and flexibility. It is mainly found in the form of hyaline cartilage (hyalos means "glass" in Greek), which is so named because of its smooth, glassy bluish-white appearance when fresh. Cartilage forms the precursor for the vertebrate skeleton in the embryo, which is replaced by bone in the neonate. The exception to this is the articular surfaces of bones (articular surfaces are where two bones move against one another) involved in joints and the ventral ends of the ribs. Hyaline cartilage is also what makes up the cartilage in the nose, bronchi, larynx and trachea. The cells of cartilage are called chondrocytes and are found in spaces (called lacunae) surrounded the extra cellular cartilage matrix. It does not contain blood vessels and is nourished by diffusion from underlying bones. Bones Long bone or spongy bone Bones are rigid connective organs that make up the skeleton of vertebrates. Bones are primarily comprised of osseous tissue which may also be referred to as bone or bone tissue. Bone is much harder substance than cartilage but it can be worn away by friction. The ridge matrix has two major components: calcium salt, which form around collagen fiber and give bone its hardness. Collagen fiber, which offer some ability to band under strain abd prevent bone from being too brittle and there fore being very likely to fracture. ...read more.


It is said to be myogenic because it is capable of rhythmically contracting without receiving any nervous stimuli and in this it differ from other muscle. The muscle branch repeatedly to form a network through which contraction spreads rapidly. Each cell has a central nucleus and is both horizontally and vertically striped. The divisions between cells are known as intercalated discs and are specially adapted for transmission of impulses. Under normal healthy circumstance, cardiac muscles is not allowed to contract myogenically because the atrial or upper chamber muscles has a different contraction rate to that of lower ventricular muscles and this would lead to inefficient and uncoordinated heart action. The automatic nervous system controls the rate of contraction in order to adapt the flow of blood to specific circumstances such as rest and exercise. Branching network Nervous tissue Nervous tissue is only found in nervous system and consist of brain, spinal code and nerves. Receiving stimuli from both external and internal sources, it serves to create consistency, co-ordination and communication between different parts of the body. The nervous system interprets stimuli from the senses organ so that vision, hearing, smell etc become apparent. Nervous is composed of: Neurones- highly specialised nerve cells which transmit nervous impulses. They are present only in brain and spinal code, but their long process forms the nerves. Neuroglia- connective tissue cells intermingled with neurones in the brain and spinal code that offers support and protection. ...read more.

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