1. Nutrition for Health Professions
Lecture 3
Mr.Adham Ahmed

2. Lecture 3
Digestion, Absorption, and Metabolism
Mr.Adham Ahmed

3. Objectives
Describe the processes of digestion, absorption, and metabolism
Name the organs in the digestive system and describe their functions
Name the enzymes or digestive juices secreted by each organ and gland in the digestive system
Calculate your basal metabolic rate (BMR)
Lecture 3
Mr.Adham Ahmed

4. Digestion
The breakdown of food in the body in preparation for absorption.
Lecture 3
Mr.Adham Ahmed

5. Type of Digestion
Mechanical digestion: food is broken up by teeth and moved along GI tract by peristalsis.
Chemical digestion: carbohydrates, proteins, and fats are broken down into nutrients tissues can absorb and use.
Lecture 3
Mr.Adham Ahmed

6. Digestion
Chemical changes occur through hydrolysis (the addition of water and breaking down of food molecules).
Enzymes act on food substances, causing them to break down into simple compounds.
An enzyme can act as a catalyst, which speeds up the chemical reactions without itself being changed in the process.
Lecture 3
Mr.Adham Ahmed

7. Absorption
The passage of nutrients into the blood or lymphatic system.
Nutrients must be in their simplest form
Carbohydrates: simple sugars
Proteins: amino acids
Fats: fatty acids and glycerol
Lecture 3
Mr.Adham Ahmed

8. Absorption
Most absorption occurs in the small intestine; some occurs in the large intestine.
Water is absorbed in the stomach, small intestine, and large intestine.
Lecture 3
Mr.Adham Ahmed

9. The Digestive System
Lecture 3
Mr.Adham Ahmed

10. Mouth Digestion begins here Enzyme (salivary amylase) acts on starch
Starch is a complex carbohydrate
Teeth break up food; food mixes with saliva
“Bolus” formed
Length of time food is in mouth is brief
Small amounts of carbohydrates changed
Lecture 3
Mr.Adham Ahmed

11. Esophagus Food travels through this muscular tube.
Connects mouth to stomach
Peristalsis and gravity act to move bolus
Cardiac sphincter opens at lower end of esophagus to allow passage of bolus into stomach.
Lecture 3
Mr.Adham Ahmed

12. Stop and Share
What symptom results when the cardiac sphincter does not close properly?
What is the name of the condition?
What prevents this condition from occurring?
Lecture 3
Mr.Adham Ahmed

13. Stop and Share
Indigestion or heartburn occurs as a result of stomach acid flowing back into the esophagus.
This is called gastroesophageal reflux.
The proper closing of the cardiac sphincter prevents the acidic content of the stomach from flowing back into the esophagus.
Lecture 3
Mr.Adham Ahmed

14. Stomach Temporary storage of food Mixing of food with gastric juices
Regulation of a slow, controlled emptying of food into the intestine
Secretion of the intrinsic factor for vitamin B12
Destruction of most bacteria inadvertently consumed
Lecture 3
Mr.Adham Ahmed

15. Stomach Pepsin breaks down proteins
Hydrochloric acid prepares the gastric area for enzyme action
Pepsin breaks down proteins
In children, rennin breaks down milk proteins
Lipase acts on emulsified fats
Lecture 3
Mr.Adham Ahmed

16. Stop and Share
You are preparing a teaching plan for the nursing staff working on a GI floor.
You plan to review anatomy and physiology of the stomach.
Lecture 3
Mr.Adham Ahmed

17. Stop and Share
Complete the following objectives to prepare for your class:
Identify the 3 parts of the stomach
Define chyme
Identify the condition that results from lack of the intrinsic factor in the stomach
Lecture 3
Mr.Adham Ahmed

18. Stop and Share Fundus: upper portion of the stomach
Body of the stomach: middle area
Pylorus: end of stomach near small intestines
Chyme: semiliquid mass of food and gastric juices
Pernicious anemia: lack of intrinsic factor
Lecture 3
Mr.Adham Ahmed

19. Small Intestine Hormones released Bile
Secretin causes pancreas to release sodium bicarbonate to neutralize acidity of chyme
Cholecystokinin triggers gallbladder to release bile
Bile
Emulsifies fat after it is secreted into small intestine
Produced in liver; stored in gallbladder
Lecture 3
Mr.Adham Ahmed

20. Small Intestine
Enzymes are found in the pancreatic juice that is secreted into small intestine.
Pancreatic proteases (trypsin, chymotrypsin, carboxypeptidases): split proteins
Pancreatic amylase: converts starches (polysaccharides) to simple sugars
Pancreatic lipase: reduces fats to fatty acids and glycerol
Lecture 3
Mr.Adham Ahmed

21. Small Intestine Produces enzymes Prepares foods for absorption
Lactase, maltase, sucrase convert lactose, maltose, sucrose to simple sugars
Peptidases reduce proteins to amino acids
Twenty-two feet long
Villi, hairlike projections, increase surface area for maximum absorption
Lecture 3
Mr.Adham Ahmed

22. Small Intestine
Lecture 3
Mr.Adham Ahmed

23. Stop and Share
A patient with a duodenal ulcer asks you where the ulcer is located.
How do you respond?
Lecture 3
Mr.Adham Ahmed

24. Stop and Share The small intestine is divided into three sections.
The duodenum is the first section of the small intestine.
The jejunum is the middle section and the ileum is the last section.
Lecture 3
Mr.Adham Ahmed

25. Large Intestine
Colon walls secrete mucus to protect against acidic digestive juices in chyme.
Major tasks of the large intestine:
Absorb water
Synthesize some B vitamins and vitamin K
Collect food residue
Lecture 3
Mr.Adham Ahmed

26. Stop and Share
You are providing pre-op teaching to a patient who is going to have intestinal surgery.
The patient asks you to explain the structure of the large intestine.
How do you respond?
Lecture 3
Mr.Adham Ahmed

27. Stop and Share
The cecum (blind pocket), colon and rectum make up the large intestine. Contents travel through:
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anal canal
Lecture 3
Mr.Adham Ahmed

28. Large Intestine
Lecture 3
Mr.Adham Ahmed

29. Metabolism The use of food by the body after digestion
Results in energy
Occurs after digestion and absorption; nutrients are carried by the blood to the cells of the body
Lecture 3
Mr.Adham Ahmed

30. Metabolism Oxidation Energy is released as nutrients are oxidized.
Nutrients combine with oxygen
Carbohydrates reduce to carbon dioxide and water
Protein to carbon dioxide, water, and nitrogen
Also known as aerobic metabolism
Energy is released as nutrients are oxidized.
Lecture 3
Mr.Adham Ahmed

31. Metabolism
Anaerobic metabolism reduces fats without the use of oxygen.
The complete oxidation of carbohydrates, proteins, and fats is commonly called the Krebs cycle.
Lecture 3
Mr.Adham Ahmed

32. Metabolism
Anabolism is the process of using energy from oxidation to create new compounds.
Catabolism is the breakdown of compounds during metabolism.
Lecture 3
Mr.Adham Ahmed

33. Metabolism
Controlled primarily by hormones secreted by the thyroid gland: Triiodothyronine (T3) and thyroxine (T4).
Lecture 3
Mr.Adham Ahmed

34. Stop and Share
What condition is associated with too much thyroid hormone?
What condition is associated with too little thyroid hormone?
Lecture 3
Mr.Adham Ahmed

35. Stop and Share
Hyperthyroidism: metabolism speeds up and the body metabolizes its food too quickly, weight is lost.
Hypothyroidism: metabolism slows down and the body metabolizes its food too slowly; patient tends to become sluggish and accumulate fat.
Lecture 3
Mr.Adham Ahmed

36. Energy Needed for involuntary and voluntary activity
Involuntary activity: maintenance of body tissue, temperature, growth
Voluntary activity: walking, swimming, eating, reading, typing
Lecture 3
Mr.Adham Ahmed

37. Energy Three groups of nutrients provide energy
Carbohydrates
Proteins
Fats
Carbohydrates should be primary source of energy.
Lecture 3
Mr.Adham Ahmed

38. Energy
The unit used to measure the energy value of foods is the kilocalorie.
kcal: amount of heat needed to raise the temperature of 1 kilogram of water 1 degree Celsius.
kcal is commonly called calorie.
Lecture 3
Mr.Adham Ahmed

39. Energy 1 gram of carbohydrate yields 4 kcal
1 gram of protein yields 4 kcal
1 gram of fat yields 9 kcal
1 gram of alcohol yields 7 kcal
Lecture 3
Mr.Adham Ahmed

40. Stop and Share
If you eat a dessert with 19 grams of fat in it, how many calories from fat does it have?
Lecture 3
Mr.Adham Ahmed

41. Stop and Share 171 calories Fat contains 9 kcal per gram
Dessert has 19 grams of fat
9 kcal/gram × 19 grams of fat = 171 kcal
Lecture 3
Mr.Adham Ahmed

42. Basal Metabolic Rate (BMR)
The rate at which energy is needed for body maintenance.
The energy necessary to carry on all involuntary vital processes while the body is at rest.
Also known as resting energy expenditure (REE).
Lecture 3
Mr.Adham Ahmed

43. Basal Metabolic Rate (BMR)
Factors that affect BMR: lean body mass, body size, sex, age, heredity, physical condition, and climate.
BMR is greater in men than women.
BMR increases during growth and fever.
BMR decreases with age and during starvation.
Lecture 3
Mr.Adham Ahmed

44. Calculating BMR Harris-Benedict equation Female BMR Male BMR
Used by dietitians for persons over age 18
Uses height, weight, and age
Female BMR
655 + (9.6 × weight in kg) + (1.8 × height in cm) – (4.7 × age)
Male BMR
66 + (13.7 × weight in kg) + (5 × height in cm) – (6.8 × age)
Lecture 3
Mr.Adham Ahmed

45. Calculating BMR Another method used to estimate BMR
Convert body weight from pounds to kilograms
Multiply kilograms by 24 (hours per day)
Multiply the answer obtained by 0.9 for a woman and by 1.0 for a man
Lecture 3
Mr.Adham Ahmed

46. Stop and Share Calculate the BMR for a woman who weighs 110 pounds.
Calculate the BMR for a man who weighs 170 pounds.
Lecture 3
Mr.Adham Ahmed

47. Stop and Share 110 pound woman: BMR 1,080 kcal
110 pounds  2.2 (pounds per kg) = 50 kg
50 kg × 24 hours in a day = 1,200 kcal
1,200 kcal × 0.9 =1,080 kcal
Lecture 3
Mr.Adham Ahmed

48. Stop and Share 170 pound man: BMR 1,854 kcal
170 pounds  2.2 (pounds per kg) = kg
77.27 kg × 24 hours in a day = 1,854 kcal
1,854 kcal × 1.0 =1,854 kcal
Lecture 3
Mr.Adham Ahmed

49. Conclusion
Food is broken down through the processes of mechanical and chemical digestion into nutrients that can be absorbed.
Enzymes act to break down nutrients.
Absorption occurs mostly in the small intestines.
Lecture 3
Mr.Adham Ahmed

50. Conclusion
During metabolism, carbohydrates and proteins are combined with oxygen in a process called oxidation.
Energy released during oxidation is measured by the kcal.
A person’s energy requirement can be measured in part by estimating the basal metabolic rate (BMR).
Lecture 3
Mr.Adham Ahmed