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2 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Sylvia S. Mader Immagini e concetti della biologia

3 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 C7 - Digestive system and nutrition

4 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Digestion helps homeostasis A digestive system involves various processes: Ingestion Mechanical digestion Chemical digestion Absorption Elimination

5 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Digestion helps homeostasis Chemical digestion involves specific enzymes in the macromolecule breakdown.

6 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Digestive tract An incomplete digestive tract as in planaria (a flatworm) has a single opening through which nutrients enter and exit.

7 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Digestive tract A complete digestive tract, as in birds and worms, has a mouth, an anus and specialized parts: crop (for storage), gizzard (for first mechanical digestion) and intestine (for chemical digestion).

8 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Digestive system in mammals Carnivores have a short digestive tract, as they obtain nutrients from meat more easily. They also have a relatively small cecum.

9 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Digestive system in mammals Herbivores have a long digestive tract, as it takes a long time to digest cellulose from plants, and a large cecum with specialized enzymes.

10 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Digestive system in mammals Some herbivores called ruminants (cows, sheep) have specialized stomaches divided into: rumen (1), reticulum (2), omasum (3) and abomasum (4) hosting microbial flora.

11 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Human digestive system Our digestive system is adapted to an omnivorous diet.

12 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The mouth Both first mechanical and chemical digestion occur in the mouth. 32 teeth divided into 4 classes chew food 3 pairs of salivary glands contain salivary amylase for digesting starch The tongue (skeletal muscle) forms a food bolus for swallowing

13 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The esophagus The esophagus is a muscular tube that passes from the pharynx to the stomach. During swallowing, the air passage is blocked by soft palate (1) and epiglottis (2), so the food bolus enters the esophagus (3).

14 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The esophagus After swallowing, peristaltic movements push the food bolus in the esophagus to the stomach.

15 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The stomach Food storage and second chemical digestion take place in the stomach. The food is mixed with gastric acid juices containing a protein digesting enzyme called pepsin.

16 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The small intestine Chemical digestion ends and absorption of nutrients takes place in the 5 to 9 meters long small intestine. Bile and pancreatic juices prepare carbohydrates, proteins and fats for digestion by maltase, peptidase and lipase.

17 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The small intestine Intestinal enzymes complete digestion to small nutrient molecules which are absorbed by the villi on the intestinal wall. villi

18 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Pancreas and liver Pancreas and liver are accessory digestive organs that produce pancreatic juice and bile respectively.

19 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Stomach and duodenum Stomach and duodenum (the upper part of the intestine) are also endocrine glands and secrete hormones. Stomach produces gastrin to help regulate food digestion. Duodenum produces secretin and cholecystokinin for stimulating the digestion of fats and proteins.

20 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Liver diseases Liver malfunctioning has effects on the whole organism. Liver disorders include: Jaundice - yellow pigmentation of the skin caused by increased levels of bilirubin in the blood. Hepatitis - inflammation of the liver caused by viruses. Cirrhosis - damage of tissues leading to loss of liver functions. Liver cancer.

21 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The large intestine The large intestine absorb water, minerals and vitamins and prepare waste for elimination. Is divided into cecum, colon and rectum. The cecum controls the flux of material through the intestine and the appendix protects from infections.

22 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The large intestine The colon is the last portion of the digestive tract and extracts water and minerals from waste before final elimination. Bacteria-aided fermentation occurs. The rectum is the final part of the large intestine and terminates in the anus. Here feces are formed and expelled.

23 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Nutrition Alimentation must provide all nutrients in balance amount. The most important nutrients are: Carbohydrates Lipids Proteins Minerals Vitamins

24 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Carbohydrates Carbohydrates (sugars, starch and fibers) provide immediate energy. Whole-grain carbohydrates are more nutritious while fibers are indigestible cellulose carbohydrates that stimulate intestine functions.

25 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Lipids Lipids supply long-term energy and are stored in fat cells. Foods from animals (butter, meat, cheese) is rich in saturated fats and cholesterol.

26 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Proteins Proteins supply amino acids, the building blocks for cells. 8 out of 20 amino acids are essential as they can not be synthesized by our cells. Protein-rich food include meat, fish, eggs, nuts, soybean and cheese.

27 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Minerals Minerals regulate biochemical reactions, maintain fluid balance and are incorporated into structures and compounds.

28 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Vitamins Vitamins are organic compounds that regulate metabolism and physiological development. Vitamins are classified as lipo-soluble (as A and D) or hydro-soluble (as C and B).

29 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Vitamins

30 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Nutrition disorders Obesity is defined as weighing 30% more than ideal body weight. Obesity is often associated with Type 2 Diabetes and cardiovascular diseases. Other common nutrition disorders are anorexia nervosa (distorted body image that leads to hypo-nutrition) and bulimia nervosa (binge-eating and purging).