Organisation in Animals

• The five levels of organisation in living organisms are: cells, tissues, organs, organ systems and organisms.
• A tissue is a group of cells with similar structure and functions.
• An organ is a group of tissues working together to perform a specific function.
• The function of bile in digestion is to neutralise hydrochloric acid from the stomach and emulsify fat to form small droplets with large surface area.
• The function of saliva is lubrication to help swallowing - contains amylase to break down starch.
• Amylase, protease and lipase are three enzymes produced in the pancreas.
• The four main components of blood are: plasma, red blood cells, white blood cells, and platelets.
• The function of platelets is to form blood clots - prevent the loss of blood and stop wounds becoming infected.
• Red blood cell adaptions:

  No nucleus - more space for oxygen.

  Contains a red pigment call haemoglobin - binds to oxygen.

  Has a bi-concave disc shape - large surface area to volume ratio for diffusion of oxygen.
• White blood cells protect the body by engulfing pathogens and producing antitoxins or antibodies.
• Substances transported in blood plasma: hormones, proteins, urea, carbon dioxide and glucose.
• The human circulatory system is a double circulatory system because blood passes through the heart twice for every circuit of the body - deoxygenated blood is pumped from the right side of the heart to the lungs and the oxygenated blood that returns from the lungs is pumped from the left side of the heart to the body.
• Arteries carry blood away from the heart under high pressure so they have a small lumen and thick, elasticated walls that can stretch.
• Capillaries carry blood to cells and tissues so they have one cell thick walls to provide a short diffusion distance.
• The structures air passes through when breathing in:

  mouth/nose.

  trachea.

  bronchi.

  bronchioles.

  alveoli.
• Veins carry blood back to the heart at low pressure so it doesn't need thick, elasticated walls but it has valves that prevent blood flowing the wrong way.