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2. Immagini e concetti della biologia Sylvia S. Mader
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

3. C8 - Digestive system and nutrition
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

4. Digestion helps homeostasis
A digestive system involves various processes:
Ingestion
Mechanical digestion
Chemical digestion
Absorption
Elimination
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

5. Digestion helps homeostasis
Chemical digestion involves specific enzymes in the macromolecule breakdown.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

6. Digestive tract
An incomplete digestive tract as in planaria (a flatworm) has a single opening through which nutrients enter and exit.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

7. 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).
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

8. 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.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

9. 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.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

10. 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.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

11. Human digestive system
Our digestive system is adapted to an omnivorous diet.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

12. 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
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

13. 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).
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

14. The esophagus
After swallowing, peristaltic movements push the food bolus in the esophagus to the stomach.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

15. 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.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

16. 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.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

17. The small intestine
Intestinal enzymes complete digestion to small nutrient molecules which are absorbed by the villi on the intestinal wall.
villi
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

18. Pancreas and liver
Pancreas and liver are accessory digestive organs that produce pancreatic juice and bile respectively.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

19. 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.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

20. 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.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

21. 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.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

22. 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.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

23. Nutrition Alimentation must provide all nutrients in balance amount.
The most important nutrients are:
Carbohydrates
Lipids
Proteins
Minerals
Vitamins
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

24. 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.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

25. 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.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

26. 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.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

27. Minerals
Minerals regulate biochemical reactions, maintain fluid balance and are incorporated into structures and compounds.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

28. 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).
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

29. Vitamins
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

30. 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).
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018