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2. Digestion and water balance
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Digestion and water balance 2
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The digestive system 3
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4. Functions of the digestive system
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Functions of the digestive system
The functions of the digestive system are:
breaking down foods into their molecular particles (mechanical and chemical digestion)
transferring these molecular particles to the blood and lymphatic stream (absorption). 4
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5. Structure of the digestive system
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Structure of the digestive system
The digestive system consists of the gastrointestinal tract and accessory organs.
The gastrointestinal tract has two endings (mouth and anus) and is formed by specialized organs.
The accessory glands (salivary glands, pancreas, liver and gallbladder) produce substances that aid digestion and absorption. 5
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6. Phases of the digestive process /mouth
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Phases of the digestive process /mouth
The digestive process includes four phases:
ingestion of food (mouth)
mechanical and chemical digestion (mouth, stomach, accessory organs, small intestine)
absorption (small and large intestine)
elimination of waste products (rectum).
The first phase occurs in the mouth: the tongue and teeth begin mechanical digestion, salivary glands produce saliva and the amylase enzyme starts chemical digestion. 6
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7. Phases of the digestive process /digestion
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Phases of the digestive process /digestion
The functions of the stomach are to:
break down and mix food particles;
produce gastric juices which continue chemical digestion and kill bacteria;
begin the digestion of proteins.
Chemical digestion continues in the small intestine, helped by the secretion of bile juice from the liver, pancreatic juice from the pancreas and intestinal enzymes. 7
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8. Phases of the digestive process /absorption
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Phases of the digestive process /absorption
During absorption, nutrients pass from the gastrointestinal tract to the blood and lymphatic streams which transport nutrients to cells.
Absorption takes place mainly in the small intestine.
Its epithelium has plicae circulares, villi and microvilli that increase its surface size, thereby facilitating absorption. 8
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9. Phases of the digestive process / large intestine
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Phases of the digestive process /
large intestine
The large intestine is the last part of the gastrointestinal tract, and it is composed of three parts: cecum, colon, rectum.
Its functions are to:
absorb water, salts and vitamins;
collect waste materials and eliminate them as feces. 9
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Nutrients
Nutrition supplies necessary nutrients to the organism, including:
carbohydrates;
lipids;
proteins;
vitamins;
minerals;
water.
Vitamins and minerals do not provide energy, but take part in all metabolic functions. Only small amounts of vitamins and minerals are necessary. 10
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The food pyramid
A balanced diet provides all the nutrients necessary for the organism.
The food pyramid indicates the types and amounts of foods that should be included in a balanced diet.
Foods at the bottom should be eaten more often and in larger quantities than foods at the top.
meat, sweets
poultry, fish, eggs, legumes
milk and dairy products
olive oil
fruits, vegetables
rice, bread, other cereals
water 11
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The urinary system 12
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13. Osmoregulation and the urinary system
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Osmoregulation and the urinary system
Osmoregulation is the process that maintains a stable fluid balance and stable concentration of solutes in the organism thereby regulating osmotic equilibrium.
The urinary system (kidneys, ureters, bladder, urethra) is responsible for the filtration of blood and for the elimination of metabolic waste as urine.
kidney
ureter
bladder
urethra 13
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14. Kidneys Kidneys are the most important organs in the urinary system.
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Kidneys
Kidneys are the most important organs in the urinary system.
Their functions are to:
eliminate metabolic waste;
regulate the concentration of salts;
maintain fluid balance;
produce erythropoietin (which stimulates red blood cell production);
regulate blood volume and pressure. 14
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15. The nephron The nephron is the basic functional unit of kidneys.
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The nephron
The nephron is the basic functional unit of kidneys.
It is formed by the renal tubule and the glomerulus.
In the glomerulus, blood is filtered.
Water and salts are reabsorbed in the renal tubule.
The remaining waste molecules are eliminated as urine which contains water, salts and uric acid. 15
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