Animal tissues and organs

• Epithelium


  Tissue that covers surfaces such as the skin or digestive tract
• Simple epithelium


  Single layer of cells
• Stratified epithelium


  Many layers of cells
• Squamous epithelium


  • Thin and flat cells that are elliptically shaped, joined like paving bricks
  • Lie on basement membrane which attaches to other tissues
  • Nucleus is flattened and in the centre of each cell
• Simple squamous epithelium


  • One-cell thick
  • Lines inside of blood capillary walls, called the endothelium
  • Lines the alveoli (in lungs)
• Stratified squamous epithelium


  • Inner lining of cheek
  • Skin is made up of stratified squamous epithelium
• Cuboidal epithelium


  • Cube-like in structure
  • Round nuclei found in the centre of the cell
  • May have microvilli on surface to increase surface area for absorption
• Cuboidal epithelium


  • Lining of sweat glands
  • Lining of salivary glands
  • Lining of kidney tubules
  • Lining of thyroid glands
• Ciliated epithelium


  • Elongated, similar to columnar epithelium
  • Have hair-like structures called cilia on the surface
• Ciliated epithelium


  • Trachea
  • Nostrils
  • Oviduct
• Columnar epithelium


  • Elongated cells
  • Nuclei located at the base of the cell
  • May contain goblet cells that secrete mucus
  • May also contain microvilli to increase surface area for absorption
• Columnar epithelium


  • Digestive tract, stomach, small intestine
• There are three types of muscle tissue: skeletal, cardiac, and smooth
• Skeletal muscle


  • Cells are long cylindrical, non-tapering and un-branched
  • Many nuclei (multi-nucleated) which are situated towards the periphery of muscle fibre
  • Transverse alternate light and dark bands present
  • Voluntary contract rapidly but soon undergo fatigue
• Smooth muscle


  • Cells are long with tapering ends (spindle shape) and un-branched
  • The cells have only one nucleus (uni-nucleated) situated in the center
  • Striations or strips are absent
  • Involuntarily not at our will, contract comparatively slow but do not fatigue
• Cardiac muscle


  • Cells are non-tapering, cylindrical and branched
  • Each cell contains one or two nuclei situated in the center
  • Cells have faint striations
  • Involuntary, rhythmically contract and relax throughout life without fatigue under normal conditions
• Neuron


  Nerve cell
• Types of neurons


  • Sensory neuron
  • Motor neuron
  • Interneuron
• Sensory neuron


  Responsible for carrying impulses (nervous messages) from the sense organs or receptors to the central nervous system (CNS which is the brain and spinal cord)
• Motor neuron


  Carries impulses from CNS to effectors (which are muscles or glands)
• Interneuron


  Connect a sensory neuron to a motor neuron
• Parts of a neuron

  • Cell body (the cell's life support center)
  • Dendrites (receive messages from other cells)
  • Axon (passes messages away from the cell body to other neurons, muscles, or glands)
  • Myelin sheath (covers the axon of some neurons and helps speed neural impulses)
• There are four groups of connective tissue: connective tissue with a jelly-like matrix, connective tissue with a rubbery matrix, connective tissue with a rigid or hard matrix, and connective tissue with a liquid matrix
• Loose connective tissue (areolar)

  • Fibroblasts secrete elastin and collagen fibres
  • Mast cells involved in inflammation
  • Elastic fibres form a loose network
  • Macrophages ingest foreign particles
  • Adipose tissue stores fat
  • Collagen fibres are thick and strong but not flexible
• Dense connective tissue (tendons and ligaments)


  • Has a dense network of white collagen fibres packed tightly together
  • Allows muscles to pull on bones to cause movement
• Tendons


  Joins muscle to bone
• Ligaments


  Attaches bone to bone at the joints
• Elastin


  Strong white fibres
• Collagen


  Strong white fibres
• Groups of connective tissue

  • Connective tissue with a jelly-like matrix: loose (areolar), dense (tendons, ligaments)
  • Connective tissue with a rubbery matrix: hyaline cartilage, yellow elastic cartilage, white fibrous cartilage
  • Connective tissue with a rigid or hard matrix: bone
  • Connective tissue with a liquid matrix: blood
• Types of neurons


  • Cell body
  • Sensory neuron
  • Motor neuron
  • Interneuron
• Basic parts of a neuron

  • Cell body (the cell's life support center)
  • Dendrites (receive messages from other cells)
  • Axon (passes messages away from the cell body to other neurons, muscles, or glands)
  • Terminal branches of axon (form junctions with other cells)
  • Myelin sheath (covers the axon of some neurons and helps speed neural impulses)
• Ligaments


  • Have a dense network of yellow elastic fibres which are tightly packed
  • Allow easy movement at the joints so that bones do not move out of place
• Cartilage


  Made up of cells called chondrocytes that are found inside spaces called lacunae, which are all floating in a rubbery matrix
• Types of cartilage


  • Hyaline
  • Yellow elastic
  • White fibrous
• Hyaline cartilage


  Reduces friction in the joints, can easily regenerate
• Hyaline cartilage


  • Has a smooth matrix
  • Chondrocytes arranged in groups of 2 or 4, or in singles
• Yellow elastic cartilage


  Gives shapes to the pinna and nose, allows epiglottis to bend without breaking
• Yellow elastic cartilage


  • Has mainly yellow elastic fibres
• White fibrous cartilage


  Acts as a shock absorber, prevents bones from dislocating