MODULE 8 (the various cell types of animals)

• Organisms are classified as unicellular and multicellular.
• Higher forms of animals reach a certain degree of complexity that their cells are organized into groups or layers to specify functions in the body)
• Epithelial tissues cover the body's internal and external surfaces with one or more layers of tightly packed cells.
• Epithelial tissues cover organ surfaces such as the surface of the skin, the airways, the reproductive tracts and the inner lining of your digestive tract.
• Epithelial tissues other functions include protection, nutrient absorption (along the intestinal tract and gas diffusion in lungs), and secretion (glandular secretion).
• Epithelial tissue can be structurally divided into two groups depending on the number of cell layers.
• Simple epithelium consists of a single layer of cells whereas stratified epithelium is made of multiple cell layers.
• Any epithelium is separated from the underlying tissue by a thin sheet of connective tissue called basement membrane
• Basement membrane provides structural and support for the epithelium and bind it to neighboring structures.
• Epithelial tissues are classified partly by shapes of their cells: squamous (flattened), cuboidal (cube-shaped), or columnar (tall and thin/elongated).
• Simple epithelium can be divided further according to shape and function of cells.
• Simple squamous epithelium is a single layer of flat cells with oval nuclei and arranged like tiles on the floor.
• Simple squamous epithelium is usually found on lining of the lungs, blood vessels, and capillary walls. Because of this, it permits diffusion of substances from one side to the other.
• Simple epithelium squamous can diffuse out the capillaries, in the lungs, oxygen can diffuse across the alveoli and into the blood.
• Simple cuboidal epithelium, roughly cuboidal in shape and each cell has spherical nucleus in the center.
• It is commonly found in secretive or absorptive tissues such as kidney tubules, ducts, and small glands and surface of the ovary.

  Simple cuboidal epithelium
• Simple cuboidal epithelium cells are elongated and column-shaped with elongated nuclei. Some columnar cells are specialized for sensory perception such as nose, ears, and taste buds of the tongue.
• Ciliated epithelium is made up of cells which can be either columnar or cuboidal, but in addition, they possess fine hair-like outgrowths called cilia on their free surfaces.
• Cilia are usually found in air passages like the nose, in the uterus, and in the fallopian tubes.
• An example is the movement of cilia in certain directions which causes the mucus to be secreted by the goblet cells to move (flow or stream) in that direction like propelling the ovum to the uterus.
• Muscular tissues are specialized cells that have a primary function of contraction and their cells are called muscle fibers which are elongated and arranged in parallel arrays. Their coordinated contraction results in movement.
• A muscle fiber is composed of cytoplasm, the sarcoplasm and its membrane called sarcolemma.
• Embedded in the sarcoplasm are many myofibrils and mitochondria. Each myofibril in turn is composed of two kinds of contractile proteins, actin and myosin.
• Muscles are classified according to location, appearance, and neural control.
• Based on their location, muscles maybe skeletal, if they are attached to the bones like biceps, triceps, pectoralis; visceral or smooth.
• If the muscles are located in the walls of hollow internal structures like the stomach, intestines, and blood vessels; and cardiac if they make up the heart.
• Based on appearance muscle may be striated, if cross striations are observed or unstriated ; smooth if cross striations are not noticeable.
• Based on neural control, muscle can be either be voluntary or involuntary.
• Voluntary muscles are found outside of the skeleton and are under control of the will.
• Involuntary muscles produce movements over which we have no control, such as motions of the stomach and other hollow internal organs.
• 3 Muscular Tissue

  • Striated
  • Smooth or Visceral
  • Cardiac
• Simple Epithelium

  • Simple squamous
  • Simple cuboidal
  • Simple columnar
• Striated muscle which is made up of long filamentous fibers with many elongated nuclei in the sarcolemma and the presence of many striations of the dark and light cross bands.
• Smooth or visceral muscle is made up of spindle-shaped cells and it is found in the walls of visceral organs. It is non-striated or smooth in appearance.
• Cardiac muscle is a very special type of muscle, which is striated and involuntary. It has many nuclei, each located internally, the fibers are characterized by branches with cross striations and unique dark bands called intercalated disk.
• Intercalated disk is where two cell membranes are adjacent to each other.
• Connective tissue is to bind together various parts of the body, to give form and support the body and lastly, forms rigid structures capable of resisting pressure and shocks.
• Connective tissues are characterized by the presence of extracellular matrix, this is a non-living material composed of protein fibers and ground substance.
• The protein fibers are composed of collagen and elastin which give strength and flexibility while the ground substance supports the cells and fibers.
• The part of the body wherein you can find connective tissue includes the cartilage, bone tendon, ligament and adipose tissue.