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. Muscular Contractions of the Digestive System
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. Absorption of nutrients into the bloodstream occurs here
SMALL INTESTINE
Absorption of nutrients into the bloodstream occurs here
VILLI - finger-like projections lining the small 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 juice contains:
proteases - digest proteins
lipases - digest lipids
amylases - digest carbohydrates

32. Small, non-vital organ – storage of bile Bile – emulsifies fat
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 Function: Largest internal organ – opposite stomach
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 producing cholesterol

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. Human Digestive System
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.

51. HEARTBURN
Cardiac sphincter stretches and stomach acid splashes walls of esophagus.
Burning and pressure in chest
Caused by overeating, acidic foods, or caffeinated beverages

52. Not enough water is absorbed out of waste before egestion
Diarrhea
Not enough water is absorbed out of waste before egestion
Usually caused by bacteria
Results in watery feces
Could cause SEVERE DEHYDRATION
Picture?

53. Appendicitis Inflammation of the appendix
Could be very dangerous if it explodes – infection will spread in bloodstream throughout body

54. Gallstones
Accumulation of hardened cholesterol in the gall bladder

55. HEPATITIS AND CIRRHOSIS
Hepatitis (inflammation of the liver)
Type A , B, & C
Cirrhosis
Distorted or scarred liver as a result of chronic inflammation

56. Question #1
The principal function of the large intestine is to:
Produce salivary amylase
Produce bile
Store bile
Reabsorb water from feces

57. Question #2
Choking on food is most likely caused by an interference with the proper functioning of the
Diaphragm
Oral cavity
Esophagus
Epiglottis

58. Question # 3
What is the role of teeth in digestion?
They break down food mechanically, increasing the surface area of the food for enzyme action.
They break food down mechanically, stimulating enzyme synthesis in the food.
They break down food chemically, aiding in the movement of food down the esophagus.
They break down food chemically, mixing saliva with the food for easier digestion.

59. Question # 4
In the human body, hydrochloric acid is responsible for the low pH of the contents of the
Lungs
Kidneys
Pancreas
Stomach

60. Question # 5
In humans villi that absorb small, soluble nutrients into the bloodstream are found in the
Large Intestine
Small Intestine
Esophagus
Stomach

61. Question # 6
Bile is a secretion produced by the liver, which aids in the emulsification of
Lipids
Proteins
Sugars
Starches

62. Question #7
Feces is usually about 40% water and 60% solid matter. Reducing the water content to 20% would most likely result in
Diarrhea
Ulcers
Gallstones
Constipation

63. Question # 8
Which nutrient should provide the largest percentage of calories in a well-balanced diet?
Proteins
Saturated fats
Water
Carbohydrates