DIGESTION and ABSORPTION

1
DIGESTION and ABSORPTION

• Learning Objectives
• Understand the physical and chemical processes of
  digestion
• Learn the function of each organ in the digestive
  system
• Gain an understanding of common Gastrointestinal
  Disorders

2
TASTE and SMELLThe Chemosenses

• 1. Olfactory Cells
• Stimulated by odors around us
• Found high inside the nose, connect directly to
  the brain
• 2. Gustatory Cells
• React to food and beverages
• Clustered into taste buds
• TASTE salty, sweet, bitter, sour, and umami

3
(No Transcript)
4
TASTE and SMELLThe Chemosenses

• 3. Common Chemical Sense
• Thousands of nerve endings on the moist surfaces
  of the eyes, nose, mouth, and throat accent our
  sense of smell and taste
• FLAVOR texture, temperature, common chemical
  sense, taste, and odor

5
CEPHALIC (preabsorptive) PHASE RESPONSE

• In response to sensory stimulation, your body
  primes its resources to better absorb and use
  anticipated nutrients
• EXAMPLE
• Sound (Hearing a description of food) can
  cause the salivary glands to increase the flow of
  saliva

6
Important Structures
7

• ASSISTING ORGANS

8
(No Transcript)
9
(No Transcript)
10
PHYSICAL PROCESSES

• Chewing
• Peristalsis the wavelike, rhythmic muscular
  contractions of the GI tract that move chyme down
  its tract
• Segmentation periodic squeezing and
  partitioning of the SI which mixes the chyme and
  promotes close contact with digestive juices and
  absorbing cells
• Sphincters regulate the flow of food particles

11
(No Transcript)
12
(No Transcript)
13
CHEMICAL PROCESSES

• Enzymes protein compounds that facilitate
  chemical reactions but are not altered in the
  process

14
CHEMICAL PROCESSES

• Acid in the stomach (hydrochloric acid)
• Base in the small intestine (bicarbonate)
• Bile
• Mucus

15
MOUTH

• Saliva
• Amylase breaks down starches into small sugar
  molecules (only about 5)
• Lingual Lipase breaks down fats, but only in a
  miniscule amount
• Epiglottis guards entrance to the trachea

16
(No Transcript)
17
STOMACH

• GASTRIC JUICE
• Water
• Hydrochloric Acid (pH 2) page 77
• Mucus
• Enzymes
• Hormones
• Intrinsic Factor

18
NUTRIENT ABSORPTION in the STOMACH

• Only
• Some lipid-soluble compounds
• Weak acids, such as alcohol and aspirin

19
SMALL INTESTINE

• Almost all digestion of protein, fat, and
  carbohydrate is performed in the SI
• Divided into three parts
• Duodenum (the first 10-12 inches)
• Jejunum ( 4 feet)
• Ileum ( 5 feet)

20
NUTRIENT DIGESTION in the SMALL INTESTINE

• SECRETIN is released upon the appearance of chyme
  in the SI ?? SECRETIN stimulates the release of
  BICARBONATE from the pancreas ?? BICARBONATE
  neutralizes the chyme

21
NUTRIENT DIGESTION in the SMALL INTESTINE

• The neutralization is important because the
  enzymes in the SI need a neutral environment
• Pancreatic juice and secretions from the
  intestinal wall cells contain a variety of
  digestive enzymes that help to digest fats,
  carbohydrates, and proteins

22
NUTRIENT DIGESTION in the SMALL INTESTINE

• BILE is released from the gall bladder upon the
  appearance of fat in the SI
• BILE acts as an emulsifier, and without it,
  lipids might not come into contact with
  pancreatic lipase, and would not be properly
  digested

23
NUTRIENT DIGESTION in the SMALL INTESTINE

• With pancreatic and intestinal enzymes working
  together, digestion creates smaller compounds of
  protein, fat, and carbohydrate which can then be
  easily absorbed
• Minerals, vitamins, and cholesterol are not
  broken down and are generally absorbed unchanged

24
NUTRIENT ABSORPTION in the SMALL INTESTINE

• Most absorption occurs in the SI 90
• Provides the surface area equivalent to a tennis
  court!
• Nutrients are trapped in folds of the intestinal
  wall and absorbed through the microvilli
• Each villus contains blood vessels and a lymph
  vessel which transport nutrients

25
(No Transcript)
26
NUTRIENT ABSORPTION in the SMALL INTESTINE

• Water-soluble nutrients are absorbed directly
  into the bloodstream
• Fat-soluble lipid compounds are absorbed into the
  lymph rather than the blood

27
(No Transcript)
28
NUTRIENT ABSORPTION in the SMALL INTESTINE

• Duodenum and Upper Jejunum most minerals (except
  sodium, chloride, and potassium)
• Jejunum and Upper Ileum carbohydrates, amino
  acids, water-soluble vitamins
• Jejunum lipids and fat-soluble vitamins
• Terminal Ileum Vitamin B12

29
LARGE INTESTINE

• Is 5 feet long and includes the cecum, colon,
  rectum, and anal canal

30
(No Transcript)
31
NUTRIENT DIGESTION in the LARGE INTESTINE

• Little digestion occurs in the large intestine
• The large population of bacteria digests small
  amounts of fiber
• This bacterial activity forms Vitamin K, Vitamin
  B12, Thiamin, Riboflavin, Biotin, and gases

32
NUTRIENT ABSORPTION in the LARGE INTESTINE

• Little absorption occurs in the large intestine
• However, it does absorb water, sodium,
  potassium, chloride, and some of the Vitamin K
  produced by bacteria
• It does not absorb Vitamin B12

33
Healthy Bacteria

• Probiotics are live microorganisms (in most
  cases, bacteria) that are similar to beneficial
  microorganisms found in the human gut.
• Probiotics are available to consumers mainly in
  the form of dietary supplements and foods.
• Look for live and active cultures. The good
  bacteria most often comes from two groups
  Lactobacillus or Bifobacterium.

34

• Prebiotics are not digested in the SI, and are
  used as food by bacteria

35
NUTRITION and GI DISORDERS

• CONSTIPATION
• Occurs when the colon absorbs too much water, or
  if the colons muscle contractions are slow and
  sluggish
• CAUSES
• Not enough liquids in the diet
• Not enough fiber in the diet
• Sedentary lifestyle
• Some medications
• Abuse of laxatives
• TREATMENT?

36
NUTRITION and GI DISORDERS

• DIARRHEA
• Occurs when the colon absorbs too little water
• CAUSES
• Most common infection from bacteria, viruses, or
  parasites
• Antibiotics
• Chronic diarrhea may signal a more serious
  medical problem (Inflammatory Bowel Disease)
• TREATMENT
• BRAT diet (bananas, rice, applesauce, toast)
• Rehydrate and replace electrolytes

37
NUTRITION and GI DISORDERS

• Gastroesophageal Reflux Disease
• Basically, chronic heartburn
• CAUSES
• Hiatal Hernias
• Foods that relax the lower esophageal sphincter
  (LES)
• Frequently occurs in people with asthma,
  irritable bowel syndrome, and developmental
  disabilities
• Concern because of increased risk of esophageal
  cancer

38
(No Transcript)
39
(No Transcript)
40

• TREATMENT
• Avoid foods that relax the LES
• Dont lie down or exercise too soon after eating,
  raise the head of the bed
• Wear loose fitting clothing
• Medications

41
NUTRITION and GI DISORDERS

• DIVERTICULOSIS
• Result of rising pressure in the colon, believed
  to be caused by low-fiber diet and constipation
• DIVERTICULITIS
• Infected or inflamed diverticulum (fecal matter
  or bacteria gets trapped)
• May experience abdominal pain, indigestion, fever
• Diverticulum may rupture causing infection, or
  can form scar tissue and create an obstruction

42
(No Transcript)
43
Diverticulosis/itis

• TREATMENT
• Diverticulosis high fiber diet
• Diverticulitis low fiber diet

44
NUTRITION and GI DISORDERS

• IRRITABLE BOWEL SYNDROME
• Disorder that interferes with normal functions of
  the colon. Symptoms are abdominal pain, bloating,
  constipation, and diarrhea
• People with IBS have more sensitive colons and
  react more strongly to stress, large meals,
  certain foods, caffeine, or alcohol
• Diagnosed by symptoms and the absence of other
  diseases
• TREATMENT
• Reduce stress
• Change diet
• Medications

45
NUTRITION and GI DISORDERS

• ULCERS
• CAUSES
• Helicobacter pylori infection (most common),
  chronic use of anti-inflammatory drugs, and
  disorders that cause excessive gastric acid
  secretion
• Not caused by spicy foods or stress

46
(No Transcript)
47

• TREATMENT
• Antibiotics
• Medications (acid suppressors)

48
NUTRITION and GI DISORDERS

• LACTOSE INTOLERANCE
• CAUSES
• Inability to digest lactose, caused by a shortage
  of lactase
• Symptoms nausea, cramps, bloating, gas, and
  diarrhea
• TREATMENT
• Dont eat dairy products! Or eat less, and more
  processed types (ex. Yogurt vs. milk )

49
(No Transcript)