Digestive System

1
Chapter 23

• Digestive System

2
Overview

• Structure
• Digestive tract
• Accessory organs
• Functions
• Mechanical digestion
• Chemical digestion
• Absorption
• Nutrition
• Nutrients
• Energy balance

3

• Function and Design of
• the Digestive System
• Chief functions
• Digestion
• Absorption
• Elimination
• Organs
• Digestive tract
• Accessory organs

4
Checkpoint 20-1 Why does food have to be
digested before cells can use it?
5

• The Wall of the Digestive Tract
• Mucous membrane (mucosa)
• Digestive juice-secreting cells
• Mucus-secreting cells (goblet cells)
• Submucosa
• Connective tissue
• Contains blood vessels and nerves that help
  regulate digestion
• Smooth muscle
• Inner layer
• Outer layer
• Peristalsis
• Serous membrane
• Epithelium
• Loose connective tissue

6
Small intestine Folds and villi
7
Wall of the digestive tract. The mucous membrane
of the small intestine shown here has numerous
projections called villi.   Zooming In u What
type of tissue is between the submucosa and the
serous membrane in the digestive tract wall?
8
Checkpoint 20-2 The digestive tract has a wall
that is basically similar throughout its length
and is composed of four layers. What are the
typical four layers of this wall?
9

• The Peritoneum
• Membrane that lines the abdominopelvic cavity
• Parietal peritoneum
• Visceral peritoneum
• Mesentery
• Mesocolon
• Greater omentum
• Lesser omentum

10
The abdominopelvic cavity. Subdivisions of the
peritoneum fold over, supporting and separating
individual organs.   Zooming In u What part of
the peritoneum is around the small intestine?
11
Checkpoint 20-3 What is the name of the large
serous membrane that lines the abdominopelvic
cavity and covers the organs it contains?
12

• Organs of the Digestive Tract
• Alimentary tract or gastrointestinal (GI) tract
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large intestine

13

• The Mouth
• Also called oral cavity, processes food by
• Ingestion
• Mastication
• Mixing with saliva
• Deglutition

14
Mouth
15
The digestive system.   Zooming In u What
accessory organs of digestion secrete into the
mouth?
16

• The Teeth
• Deciduous teeth (baby teeth)
• 20 teeth
• Adult permanent teeth
• 32 teeth
• Incisors
• Cuspids (canines or eyeteeth)
• Molars
• Structure
• Dentin
• Blood vessels
• Nerves
• Gingiva
• Crown
• Enamel
• Roots
• Cementum

17
Checkpoint 20-4 How many baby teeth are there
and what is the scientific name for the baby
teeth?
18

• The Pharynx
• Also called the throat
• Oropharynx
• Palatine tonsils removed during tonsillectomy
• Nasopharynx
• Laryngeal pharynx
• Soft palate
• Uvula
• Epiglottis

19

• The Esophagus
• Muscular tube
• No digestion occurs here
• Joins with stomach
• Esophageal hiatus-Hiatial hernia

20

• The Stomach
• Structure
• Additional angled muscle layer
• Greater and lesser curvature
• Fundus
• Lower esophageal sphincter (LES) (cardiac
  sphincter)
• Pylorus- may not be patent in newborn- vomiting
• Pyloric sphincter
• Rugae
• Functions
• Store food and liquid
• Secrete gastric juice
• Secrete mucus

21
Stomach Structure
22
Checkpoint 20-5 What type of food is digested in
the stomach?
23

• The Small Intestine
• Structure
• Duodenum
• Jejunum
• Ileum
• Functions
• Secrete mucus
• Secrete enzymes
• Absorb digested food
• Villi
• Microvilli
• Blood vessels
• Specialized lymphatic capillaries (lacteals)

24
The small and large intestines.   Zooming In u
What part of the small intestine joins the cecum?
25
Checkpoint 20-6 What are the three divisions of
the small intestine? Checkpoint 20-7 How does
the small intestine function in the digestive
process?
26

• The Large Intestine
• Structure
• Cecum
• Ileocecal valve
• Vermiform appendix
• Colon
• Ascending
• Transverse
• Descending
• Sigmoid
• Rectum
• Anal canal
• Anus
• Functions
• Secrete mucus
• Reabsorb some water
• Form feces (stool)
• Defecation

27
Large intestine
28
Checkpoint 20-8 What are the divisions of the
large intestine? Checkpoint 20-9 What are the
functions of the large intestine?
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• The Accessory Organs
• Release secretions through ducts into digestive
  tract
• Salivary glands to mouth
• All other organs to duodenum

30
Accessory organs of digestion.   Zooming In u
Into what part of the intestine do these
accessory organs secrete?
31

• The Salivary Glands
• Functions of saliva
• Moistens food
• Facilitates mastication and deglutition-(swallowin
  g)
• Helps keep teeth and mouth clean
• Production of saliva
• Parotid glands
• Submandibular (submaxillary) glands
• Sublingual glands

32
Checkpoint 20-10 What are the names of the
salivary glands?
33

• The Liver
• Structure
• Right, left lobes
• Portal vein
• Hepatic artery
• Functions
• Manufacture bile
• Store glycogen, convert to glucose
• Modify fats
• Store vitamins, iron
• Form blood plasma proteins
• Destroy old red blood cells
• Synthesize urea
• Detoxify harmful substances drugs

34

• The Gallbladder
• Bile
• Flows from liver through cystic duct
• Is stored in gallbladder
• Flows through cystic duct and common bile duct to
  duodenum when needed

35

• The Pancreas
• Produces enzymes that digest fats, proteins,
  carbohydrates, and nucleic acids
• Produces alkaline (basic) fluid to neutralize
  acidic chyme in small intestine
• Produces insulin and glucagon to regulate sugar
  metabolism

36
Checkpoint 20-11 What is the role of the
gallbladder? Checkpoint 20-12 What is the role
of the bile in digestion?
37

• Enzymes and the Digestive
• Process
• Enzymes
• Speed up rate of chemical reactions
• Are not changed or used up in reactions
• Are proteins
• Are highly specific in their actions

38

• The Role of Water
• Water is used to
• Produce digestive juices
• Dilute food
• Aid chemical process of digestion
• Added to nutrient molecules as they are split by
  enzymes

39

• Digestion, Step-by-Step
• Mouth
• Chews food, mixes with saliva
• Stomach
• Secretes hydrochloric acid, enzymes
• Secretes mucus
• Forms chyme
• Small intestine
• Mixes chyme with bile
• Receives pancreatic juice enzymes
• Produces enzymes

40
Checkpoint 20-13 What organ produces the most
complete digestive secretions?
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• Absorption
• Villi in mucosa of small intestine
• Arteriole and venule bridged with capillaries
• Capillaries absorb
• Simple sugars
• Small proteins
• Amino acids
• Simple fatty acids
• Water
• Portal system transports nutrients to liver

42
Digestion and absorption
43

• Absorption of Fats
• Lacteals absorb fat
• Fat/lymph mixture (chyle) drains from small
  intestine
• Chyle merges with lymphatic circulation, enters
  blood in veins near heart
• Liver further processes absorbed fats

44

• Absorption of Vitamins and Minerals
• When vitamins and minerals are
• Dissolved in water
• Absorbed directly into blood
• Incorporated in fats
• Absorbed with fats
• Produced by bacterial action
• Absorbed in large intestine

45
Checkpoint 20-14 What is absorption?
46

• Control of Digestion
• Nervous
• Parasympathetic stimulation increases
  activityFeed and Breed
• Sympathetic stimulation decreases activity
• Hormonal
• Digestive organs produce hormones
• Gastrin
• Gastric-inhibitory peptide (GIP)
• Secretin
• Cholecystokinin

47
Checkpoint 20-15 What are the two types of
control over the digestive process?
48
Chemical digestion
49

• Hunger and Appetite
• Hunger
• Hypothalamic centers regulate
• Blood nutrient levels stimulate-glucose levels
• Satisfied by adequate meal
• Appetite
• No relationship to need for food
• May not be satisfied by adequate meal

50

• Eating Disorders
• Anorexia
• Chronic loss of appetite
• Possible emotional, social factors
• Anorexia nervosa
• Psychological disorder
• Bulimia (binge-purge syndrome)

51
Checkpoint 20-16 What is the difference between
hunger and appetite?
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• Disorders of the Digestive
• System
• Sources of digestive problems
• Mechanical
• Nervous
• Chemical
• Hormonal

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• Peritonitis
• Infection of the peritoneum following infection
  of
• an organ covered by peritoneum
• Localized
• Generalized

54

• Diseases of the Mouth and Teeth
• Dental caries
• Gingivitis
• Periodontitis
• Vincent disease
• Leukoplakia

55
Checkpoint 20-17 What are some common diseases
of the mouth and teeth?
56

• Disorders of the Esophagus and Stomach
• Acid reflux
• Varicose veins of the esophagus
• Hiatal hernia
• Heartburn
• Chronic reflux or gastroesophageal reflux disease
  (GERD)
• Nausea
• Vomiting (emesis)
• Gastritis
• Flatulence
• Stomach cancer
• Peptic ulcer
• Pyloric stenosis

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• Intestinal Disorders
• Appendicitis
• Inflammatory bowel disease (IBD)
• Crohn disease
• Ulcerative colitis
• Irritable bowel syndrome (IBS)
• Gastroenteritis
• Diverticulitis
• Diarrhea
• Constipation
• Intestinal obstruction
• Intussusception
• Volvulus
• Ileus
• Hemorrhoids
• Colon and rectum cancer

58
Checkpoint 20-18 What two diseases fall into the
category of inflammatory bowel disease?
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• Infection of the Salivary Glands
• Mumps
• Contagious viral infection of parotid salivary
  glands
• Possible complications
• Inflammation of testicles
• Sterility in males
• Prevented by childhood vaccine (MMR)

60

• Cirrhosis and Other Liver Diseases
• Cirrhosis
• Active liver cells replaced by scar tissue
• Alcoholic (portal) type is most common
• Jaundice
• Hepatitis
• Liver inflammation
• Viral causes
• Cancer

61

• Gallstones
• Cholelithiasis
• Most common gallbladder disease
• May remain in gallbladder or lodge in bile ducts

62

• Pancreatitis
• Pancreatic enzymes back up into pancreas
• Can be fatal (acute pancreatitis)

63

• Aging and the Digestive
• System
• Loss of appetite
• Difficulty swallowing-with Alzheimers
• Decreased digestive organ activity
• Digestive disorders
• Tumors and cancer