Tissues

Tissues

1. Epithelial

   • Simple
     • Squamous
       • Structure
         • A thin single layer of delicate cells containing nuclei. The layer of cells is in contact with a base membrane,
       • Function
         • The single layer of cells occurs where small molecules need to pass quickly through membranes by diffusion hence the cells being thin. This tissue occurs in capillary and alveolar walls in order to let oxygen and carbon dioxide pass through in both and glucose in capillary walls.
     • Cuboidal
       • Structure
         • The cuboidal epithelial cells are cuboid in shape with nuclei in the centre and can withstand more trauma than the squamous cells. 
       • Function
         • These cells are used for secretion and absorption. For example water in the kidney tubules or thyroxin in the thyroid gland, etc.
     • Cilliated columnar
       • Structure
         • The cilliated columnar cells are column in shape with nuclei in the centre. They often have goblets between them and have microvilli on the top
       • Function
         • The goblets in between the cilliated columnar cells produce mucus (which traps dust and dirt). The microvilli on top of the columnar cells move the mucus. These cells are found in the upper respiratory tract, fallopian tubes, etc.
   • Stratified
     • Keritanised
       • Structure
         • These cells are the human skin. The layers on top are dead, flat cells filled with keratin. They contain no nuclei or organelles. The latyers underneath are cuboidal.
       • Function
         • The cells are filled with the protein keratin in order to maintain the waterproof nature of the human skin. The bottom layer of cells continually divide to replace the surface cells thus creating house dust. 
     • Non-keratinised
       • Structure
         • The non-keratinised structure is the same as the keratinised with the absence of the dead layer.
       • Function
         • The cells are kept moist by bodily secretions to keep them from drying out. They are designed for lubrication specifically in chewing and swallowing. they are found in the esophagus, anal canal, etc.

2. Muscle

   • The nervous system controls the muscles.
   • Skeletal
     • Skeletal muscle is controlled by motor nerves in the somatic nervous system.
     • Structure
       • The muscle is connected to the bone by tendon. It contains blood vessels and muscle fiber in the centre of the fascicle.
     • Function
       • The muscles contract and relax to cause movement of the bones they are attached to. They are controlled by motor (efferent)( nerves under conscious control.
   • Smooth
     • Smooth muscle is controlled by nerves in the autonomic nervous system.
     • Structure
       • Smooth muscle cells are rugby ball shaped. Smooth muscle cells are 'fatter' when contracted. They are flatter when relaxed.
     • Function
   • Cardiac
     • Cardiac muscle is controlled by the autonomic nervous system (the sympathetic branch speeds the heart up and the parasympathetic branch slows the heart down.
     • Structure
     • Fucntion

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