Cells to Systems

• Levels of structural organisation in multicellular organisms

  • Cell
  • Tissue
  • Organ
  • System
  • Organism
• Cell


  Basic functional unit of a living thing
• Tissue


  Assembly of similar cells
• Organ


  Made up of several different kinds of tissue that together, perform a single common function (eg stomach digests proteins)
• System


  Different organs that together perform a single common function (eg the digestive system working together to digest things)
• Organism


  Has lots of different systems and performs a grand function
• Basic tissue types


  • Muscle tissue
  • Nervous tissue
  • Epithelial tissue
  • Connective tissue
• Muscle tissue


  • Largely involved in movement in various ways, Muscle tissue is composed of cells that have the special ability to shorten or contract in order to produce movement of the body parts.
• Nervous tissue


  • Involved in communications between one part of the body and another
• Connective tissue


  • Supports, protects, and gives structure to other tissues and organs in body
• Types of muscle tissue

  • Skeletal/striated muscle tissue
  • Smooth muscle tissue
  • Cardiac muscle tissue
• Skeletal/striated muscle tissue


  Attached to the skeleton, voluntary muscle (you can choose to move them, eg turning your head), contracts voluntarily
• Smooth muscle tissue


  Found around blood vessels and intestines, involuntary muscle (you can't choose or have control over the contractions in your intestine), contracts involuntarily
• Cardiac muscle tissue


  Makes up the walls of the chambers of the heart, contracts involuntarily (can't voluntarily make your heart beat faster or slower)
• Types of nervous tissue

  • Sensory Neuron
  • Interneurons
  • Motor Neuron
  • Glia
• Sensory Neuron


  Carries information to CNS
• Interneurons


  Within the CNS and carries information from CNS to CNS
• Motor Neuron


  Going from the CNS out to muscles and other effectors that can respond to the stimuli that have been communicated
• Glia


  Not a neuron, it's the other main type of nervous tissue, outnumbers neurons by 10 times, facilitates communication between neurons, regulates inflammation and forms the blood-brain barrier
• Epithelial tissues


  Includes all the cells that form the interface between the body and the external environment. It includes the epidermis, mucous membrane, lining of the gastrointestinal tract, airways, reproductive system, and exocrine glands.
• Connective tissues


  • Loose connective tissues (areolar tissues)
  • Adipose tissue
  • The dermis
  • Ligaments
  • Tendons
  • Osseous tissue
  • Cartilage
  • Blood
• Connective tissues


  Fibrous tissues containing cells, separated by an extracellular matrix (some sort of substance that's not actually made of cells)
• Organs


  Structures in the body composed of various tissues (often of all 4 tissue types) that together, achieve an important function in the body
• Systems


  Arrangements of organs that work together to carry out a major purpose in the body. The organs often overlap in different systems.
• The trachea is considered an external environment. Thus, the lining of the trachea is made from epithelial tissue
• Organs contain several tissue types, not just one