Multicellular Organisms - Section 6

 A large animal has a small surface area relative to its volume  It needs additional absorbing surfaces to take in oxygen & food  Once these substances have entered the body, they need to be carried to each of the cells  - this requires a circulatory system

 By the end of this section you will be able to:  - describe the pathway of blood flow through the circulatory system  - identify the chambers of the heart  - identify the key structural features of the three types of blood vessel  - describe the components of blood

Structure of the heart Divided into 4 chambers - 2 atria & 2 ventricles Right atrium receives deoxygenated blood from the body - via the vena cava This blood passes through the heart Leaves via the pulmonary artery Picks up oxygen in the lungs Returns to the heart via the pulmonary veins Passes through the heart, and leaves via the aorta

Heart wall and valves Left ventricle wall is very thick and muscular - to pump blood around the body Right ventricle wall is thinner - only pumping to the lungs The heart has 4 valves They open and close to let blood flow through - ensure blood only travels in one direction - stops blood flowing backwards

Blood Vessels Arteries - carry blood AWAY from the heart - have a thick muscular wall (to withstand high pressure) - usually carry oxygenated blood (exception is pulmonary artery) Veins - carry blood TO the heart - carry blood at low pressure - thin walled, but have valves - valves prevent backflow Capillaries - tiny vessels (1 cell thick) - exchange materials between blood and cells

Coronary arteries The heart muscle needs it’s own blood supply - provided by the coronary arteries These branch off from the aorta They spread out all across the heart If they become blocked = coronary heart disease (heart attack)

 An average adult has 5 litres of blood in the body  Blood transports useful and waste substances around the body  E.g. oxygen, CO 2, food, urea  Blood has the following components:  Platelets  - form blood clots  White blood cells  - involved in the immune system  plasma  – liquid part of the blood  - carries dissolved substances  Blood also contains…..

 -Very small and numerous (5.5 million/ml of blood) - Have a biconcave shape - - provides a larger surface area - Small and flexible - - can easily squeeze through narrow capillaries - Cytoplasm is rich in haemoglobin - - in the lungs, combines with oxygen to form oxy- haemoglobin - - at the tissues, oxygen is released

 1) Name the four chambers of the heart  2) Name blood vessel A  3) Where has the blood in vessel A come from?  4) Name the three types of blood vessel, and describe the differences in their structure  5) Name the pigment in red blood cells, that helps carry oxygen  A

Structure & function of lungs Organs of gas exchange Air passes in through the nose or mouth Then passes through the trachea (windpipe), bronchi, bronchioles - and finally into the alveoli (air sacs) Trachea and bronchi are lined by tiny hair-like cilia - and cells that secrete mucus - which traps dirt and micro- organisms The cilia sweep the mucus away from the lungs

Gas Exchange Alveoli are surrounded by many capillaries Alveolus lining is very thin and moist Large surface area for exchange Breathing in: - air enters alveoli - oxygen dissolves in the moist lining - then diffuses into the blood - blood is now oxygenated - CO 2 moves in the opposite direction

 Food is needed for cells to:  Give fuel for energy  Provide building materials for  - growth  - repair  - fighting infection (antibody production)  Digestion breaks down large insoluble molecules  - into small soluble molecules  - much of the digestion is done by enzymes  These molecules can then be absorbed into the bloodstream

 A long tube running from mouth to anus  Has several associated organs connected to it  e.g. liver, pancreas, salivary glands  These organs are connected by tubes or ducts Pharynx (throat) Oesophagus

 Oesophagus is a muscular tube  - connects the mouth to the stomach  It’s wall is lined with circular muscle  Contraction & relaxation of this muscle pushes food along  This is known as Peristalsis  This process continues all the way along the alimentary canal

 Where the majority of digestion (& all absorption) takes place  Structure:  - very long  - folded inner lining  - covered in finger-like villi  These create a large surface area  Each villus has a blood capillary and lacteal  Lining is only 1 cell thick  Glucose & amino acids pass into the capillary  Fat digestion products pass into the lacteal  Digestion products absorbed into the bloodstream

 The major food groups that make up a balanced diet are carbohydrates, fats and proteins  Carbohydrates  – provide energy for cell activities  Fats  – Energy storage & insulation  Proteins  – Provide materials for growth & repair

The lack of a certain vitamin or mineral in the diet can result in a deficiency disease VitaminFood source FunctionEffect of Vitamin deficiency ADairy products & fish Healthy skin, good vision, strong immune system Night blindness CFruit & Veg Growth & repair of skin Scurvy DOily fish & eggs Calcium absorption – for bone growth Rickets MineralFood sourceFunctionEffect of deficiency IronMeat & eggsHelps form haemoglobin Anaemia CalciumDairy products Hardening bones & teeth Rickets Sodium /Potassium Most foodsMuscle contraction / nerve impulses Impaired movement

 1) What is the purpose of :  - the cilia  - mucus  2) Explain the role of alveoli  3) Describe the mechanism of peristalsis, with reference to a mouthful of food having been swallowed  4) State three ways the small intestine is suited to it’s role of absorbing digested food