A Close Look at How the Human Body Functions

1. A Close Look at How the Human Body Functions

3. The Digestive System

4. The Basics of Nutrition Heterotrophs (can NOT synthesize organic nutrients) Digestion involves: • ingestion: taking in food • digestion: breaking down the food into a form that can be transported across the cell membrane • egestion: getting rid of undigested wastes

5. The Basics of Nutrition Nutrient: any substance that provides energy for growth and repair: • Carbohydrates • Proteins • Lipids • Vitamins • Minerals • Water

7. Food molecules must be converted into subunits that can pass easily through cell membranes

8. large molecules end products of digestion 1. Carbohydrates Monosaccharides (polysaccharides) 2. Proteins Amino acids (polypeptides) 3. Lipids Fatty acids and Glycerol

9. Structure of Digestive System • Continuous tube extending from mouth to anus • Accessory organs attached along the way (appendix, gall bladder, liver, pancreas)

10. Organs of Digestive System • Mouth – “oral cavity” • Pharynx – “throat” • Esophagus • Stomach • Small intestine • Large intestine – “colon”

11. The Mouth • Ingestion occurs here • Contains teeth, tongue, and salivary glands • Both chemical and mechanical digestion occur here. • Chemical: salivary amylase is an enzyme in saliva that breaks down ( Starch) carbohydrates. • Mechanical: teeth grind food increasing surface area for enzyme action

12. saliva also lubricates the food by adding water and mucus

13. Mechanical or Chemical?

14. a. food we swallow is called a bolus

16. Pharynx • Back of the throat • Where openings to trachea and esophagus meet • Epiglottis: flap of connective tissue that closes over the trachea when swallowing

17. Esophagus • tube that connects the oral cavity with stomach • peristalsis: muscular contractions that squeeze food towards the stomach

18. Peristalsis Muscular Contractions of the Digestive System

21. Stomach • muscular organ that mechanically digests food • lined with cells that secrete - mucus to protect stomach lining - protease ( Pepsin ) to chemically digest protein - hydrochloric acid (HCl)

22.  HCl has several functions - lowers the pH in the stomach (pepsin works best at pH 2) - helps to kill microorganisms ingested in the food

23. The acidic chyme leaves the stomach and enters the small intestine

24. SMALL INTESTINE • Absorption of nutrients into the bloodstream occurs here • VILLI - finger-like projections lining thesmall intestines for increased surface area for…… DIFFUSION of nutrients to occur

25. Small Intestines: - length is approximately 9 feet: food remains here for a long time - villi: Increases the surface area to about 300 m2 (size of tennis court)

26. Most of the chemical digestion of food occurs in the SI by the time food passes through the duodenum– (first 25 cm of the SI)

28. The Villi

29. Digested end products are taken into the villi by active and passive transport

30. Accessory Organs • Pancreas: - produces enzymes that break down carbohydrates,, lipids, proteins and releases them into the SI - produces sodium bicarbonate – neutralizes stomach acid - Also produces hormones that regulate blood sugar levels (Endocrine Hormones)

31. pancreatic juicecontains: proteases - digest proteins lipases - digest lipids amylases - digest carbohydrates

32. Gall Bladder • Small, non-vital organ – storage of bile • Bile – emulsifies fat • Tucked on underside of liver

33. Gallbladder The gallbladder releases bile into the SI

34. Bile is NOT an enzyme - its function is to break down fat globules by a emulsification

35. Emulsification: mechanical digestion of fats molecules dissolved into smaller droplets

37. The Liver • Largest internal organ – opposite stomach • Function: • Produces bile (breaks down fats) • Converts glucose to glycogen • Produces urea (the main substance of urine) • Filters harmful substances from the blood (such as alcohol) • Responsible for producingcholesterol

38. Bile is produced in the liver then stored in the gallbladder

39. Bile is a mixture of 3 chemicals • cholesterol - excess cholesterol removed from the blood by the liver

40. 2. bilirubin - a yellow pigment formed from dead red blood cells

41. 3. bile salts - to help break up the fat structure

42. Appendix • Pouch located where small and large intestines meet • A vestigial organ: • Non-vital – we notice no side effects when it is removed • Thought to house important bacteria needed for balance in body • Could possibly play a role in immunity • In evolutionary past – scientists believe that there were 180 vestigial structures – today there are virtually none!!!

44. LARGE INTESTINE • All indigestible waste at this point – no nutritional value • Known as the colon • Regulates water concentration of fecal matter before EGESTION through the RECTUM and ANUS • Function is to reabsorb most of the water that was not picked up by the SI • Too much or too little water can be problematic…

45. A large colony of bacteria known as E. Coli lives in the LI They Help produce vitamin K - needed for blood clotting

48. What Can Go Wrong?? Malfunctions of the Human Digestive System

49. Ulcers • Erosion of the stomach lining by digestive enzymes or acid due to lack of protective mucus.

50. Constipation • Large intestine is difficult to empty due to too much water being reabsorbed in the colon – waste hardens.