1. Chapter 14 The Digestive System and Body Metabolism
Essentials of Human Anatomy & Physiology
Seventh Edition
Elaine N. Marieb
Chapter 14 The Digestive System and Body Metabolism
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

2. Organs of the Digestive System
Figure 14.1
Slide 14.2b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

3. Know this: Peristalsis vs. segmentation
Alternating contractions & relaxations move food one way through digestive system
Alternating contractions & relaxations move food back & forth to break it up and mix it

4. Mouth
Why is the epithelium on the gums, hard palate, and dorsal surface of tongue keratinized?
Protect from abrasion during eating
Lips and cheeks
keep food between teeth when we chew
play a role in speech
Palate
hard palate & soft palate
What happens during swallowing so that we do not aspirate food into the lungs?
Soft palate rises to close off the nasopharynx while Epiglottis closes off larynx to block trachea

5. Mouth (Oral Cavity) Anatomy
Figure 14.2a
Slide 14.4
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6. Tongue
Functions
speech movements
mixes food with saliva
forms food bolus
What are the function of the intrinsic & extrinsic muscles of the tongue?
Intrinsic – allows tongue to change shape
Extrinsic – alters the position of the tongue

7. Tongue Lingual Frenulum Papillae secures tongue to floor of mouth
limits posterior movements – can’t really swallow your tongue!
tongue tied = extremely short lingual frenulum – causes speech distortions – can be surgically cut to correct
Papillae
Filiform = rough – provide friction
Fungiform = taste buds – located on sides & apex
Circumvallate = taste buds – row on back of tongue

10. Salivary Glands 4 functions Cleanses teeth Dissolves food chemicals
Moistens food
Chemical breakdown of starch

11. Types of salivary glands
Parotid
Mumps = viral inflammation of parotids – can cause sterility in males
submandibular
sublingual
Types of cells
serous cells produce salivary amylase to breakdown starch
mucous cells produce mucus for lubrication
different glands produce different types of secretions

13. Pharynx
2 muscular layers (circular & longitundinal) cause peristaltic waves to move food
Oropharynx and laryngopharynx are common passageways for food, fluids, and air
Nasopharynx has no digestive role (unless you laugh so hard that you blow your soda through your nose !!!)

14. Review: Pharynx Anatomy
Nasopharynx – not part of the digestive system
Oropharynx – posterior to oral cavity
Laryngopharynx – below the oropharynx and connected to the esophagus
Figure 14.2a
Slide 14.8
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15. Swallowing Process

16. Esophagus ~10 inches long epiglottis routes food into it
goes through the diaphragm to join stomach at gastroesophageal sphincter (aka. Cardioesophageal sphincter)

18. GERD = gastroesophageal reflux disease
Heartburn is a symptom of this

19. Esophageal ulcers

20. Includes full body digestive system diagram
End of Quiz #1 Material
Includes full body digestive system diagram

21. Stomach Function: storage tank Site of mechanical digestion
Chemical breakdown of proteins begins

23. Stomach position In shorter or more obese people:
High and horizontal
In taller or thinner people:
Elongated vertically (like a J shape)

24. Stomach features ~ 10 inches long – on left side of abdominal cavity
can hold 1.5 L to 4.0 L of food
Rugae – large longitudinal folds that help mix food in stomach
Know ALL structures on diagram

25. Stomach features
Pyloric sphincter: controls stomach emptying into small intestine
What important substance is produced by the parietal cells of the stomach & what does it do?
Intrinsic factor – necessary for vitamin B12 absorption
What blood disorder can absence of this substance lead to?
Pernicious anemia

26. Stomach
Stomach empties in 4-6 hours – know this

27. Specialized Cells Simple columnar epithelium
Mucous neck cells – produce a sticky alkaline mucus
Gastric glands – secrete gastric juice
Chief cells – produce protein-digesting enzymes (pepsinogens)
Parietal cells – produce hydrochloric acid
Endocrine cells – produce gastrin
Slide 14.19
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

28. Stomach features Mucosal Barrier – important 3 factors
Thick coating of alkaline mucus
Tight junctions of epithelial cells
Epithelium is completely renewed ~3 days

30. Chyme
Creamy semifluid mass of ingested, partially digested food

31. Stomach features Gastric Ulcers Erosion of stomach wall
Causes: H.pylori bacteria, hypersecretion of HCl or pepsin, hyposecretion of mucus, dietary/smoking/stress factors contribute
Danger: perforation of stomach wall followed by peritonitis and hemorrhage

32. Gastric Ulcer

34. Stomach Anatomy Slide 14.17 Figure 14.4a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

35. Small Intestine 6 meters long (~21 feet) but only 1 inch in diameter
suspended by mesentary in the abdominal cavity
3 sections of the small intestine
Duodenum: joins stomach at pyloric sphincter, ~10 inches, curves around head of pancreas
Jejunum: ~8 feet
Ileum: ~12 feet, joins large intestine at ileocecal valve

36. Function & Features of SI
Function: all nutrient absorption
Huge surface area due to length & modification
Plicae circulares: deep folds that force chyme to spiral – mixes it and slows movement – folds do NOT disappear when filled with food – contain Peyer’s patches (lymphatic glands)
Villi: fingerlike projections – increase SA for absorption
Microvilli: tiny projections – increase SA & release digestive enzymes

37. Villi of the Small Intestine
Fingerlike structures formed by the mucosa
Give the small intestine more surface area
Figure 14.7a
Slide 14.24
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

38. Microvilli of the Small Intestine
Small projections of the plasma membrane
Found on absorptive cells
Figure 14.7c
Slide 14.25
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

39. Liver Liver has multiple functions: metabolic & regulatory
Only digestive function is to produce bile for export to the duodenum
Bile is used to emulsify fats – distribute fat into solution to be accessible to digestive enzymes

40. Liver Has 4 lobes & weighs about 3 pounds
Very vascular (since one of its other functions is to detoxify blood!)
It is the largest gland in your body

42. Cell Types in Liver Hepatocytes: Kupffer cells Produce bile
Pick up nutrients to process (example: convert glucose to glycogen for storage)
Store vitamins ADEK
Detoxify substances in blood
Kupffer cells
Phagocytes that remove debris from blood

43. Liver disorders
Hepatitis: acute inflammation of liver – usually caused by a virus – multiple types: some transmitted by contaminated food or water, some transmitted sexually
Cirrhosis: chronic inflammation of liver – can be caused by multiple things: alcoholism, toxins, ongoing hepatitis

44. Gall Bladder 4 inches long Thin walled, greenish sac
Stores & concentrates bile
Sphincter of Oddi regulates release of bile into small intestine

48. Pancreas Principal enzyme producing organ of the digestive system
2 types of cells
Acinar – secrete pancreatic enzymes
Islets of Langerhan’s – secrete insulin & glucagon to regulate blood glucose
Bile & pancreatic juice enter SI together through Sphincter of Oddi

50. Chemical Digestion in the Small Intestine
Figure 14.6
Slide 14.23b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

51. Large Intestine ~5 feet long
Major function: dry out indigestible substances by absorbing water – then eliminates feces
Subdivisions (see on diagram): Cecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anus

53. Large Intestine
Appendix can be a trouble spot: can be a spot for bacteria to accumulate, multiply, cause infection, then rupture
Signs: pain in umbilical region, nausea, lower right quadrant pain (rebound pain)
Surgical removal before rupture!

54. Anal Sphincters
Internal, involuntary
External, voluntary

55. End of Quiz #2 Material stomach & liver diagrams

56. Physiology of Digestion

57. Processes of the Digestive System
Figure 14.11
Slide 14.46
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

58. Sensors of the GI tract
Regulated by the Parasympathetic division of ANS
Mechanoreceptors: responds to stretch of the organ walls
Osmoreceptors: responds to solute concentration and pH
Chemoreceptors: responds to the presence of end products

59. Saliva
Salivary amylase is an enzyme that begins the digestion of starches
There are 4 helpful substances in saliva that help protect/heal us
IgA antibodies
Lysozyme
Glandular virus blocker
Growth factor
The average daily output of saliva is 1 to 1.5 L

60. Saliva Fear/excitement cause dry mouth
When SNS is activated, it causes vasocontriction of BV to the salivary glands and inhibits saliva release
Halitosis: Any disease process that inhibits saliva secretion will result in halitosis since decomposing food particles accumulate and bacteria flourish (bacterial waste cause the odor!!)

61. Swallowing Structures involved in swallowing: Tongue Soft palate
Pharynx
Esophagus
22 other muscles

62. Routing the food
What 3 things does your body do to cause food to be routed into the digestive tract only?
Tongue blocks off mouth
Soft palate rises to close off nasopharynx
Epiglottis closes off laryngeal opening to respiratory tract

63. Rennin The enzyme called rennin is only produced by infants.
This enzyme helps with milk digestion by solidifying the milk.

64. Nutrient Absorption
Alcohol and aspirin are 2 of the commonly ingested substances that can be absorbed directly into the blood stream through the stomach mucosa.
Other nutrients are absorbed in the SI during their 3-6 hour journey.

65. Cleft Palate
Hard palate does not fuse completely so mouth is open into nasal cavity. Seriousness is that infants cannot suck properly to obtain nourishment. They will have to be fed through a stomach tube.

66. Cleft palate

67. Plasticity What is plasticity & why is it important?
Stress/relaxation response: ability of smooth muscle to be stretched & then relax while distended
Prevents tension from causing the stomach to contract expulsively as it fills with food/fluids
This would cause you to vomit violently every time your stomach started to fill up

68. Stomach Emptying It takes the stomach 4-6 hours to empty completely
The rate of gastric emptying depends on:
Contents of duodenum as well as state of food digestion in stomach.
Duodenum must be empty enough to receive chyme

69. FYI: Digestion Rates
High carbohydrate meals move rapidly through the duodenum – this is why you get hungry quickly after eating sugary cereal for breakfast
Fats form an oily layer on top of the chyme and cause release of enterogastrone which slows digestion – this is why breakfast tacos keep you feeling fuller longer

70. Disorders
Hiatal hernia, heartburn, esophagitis, & esophageal ulcers: page 449

71. Vomiting
At home: Read imbalance on page 452

72. Miscellaneous Facts
Bile is necessary for absorption of fat & fat soluble vitamins in the intestines
Bile salts emulsify fats
Remember: bile is produced by the liver & stored in the gall bladder
Bilirubin gives bile its yellowish-green color

73. Food Allergies – just know the basics of this
Immature intestinal mucosa allows intact proteins across the membranes.
Immune system doesn’t recognize the antigens on the proteins & attacks them.
These early food allergies usually disappear as mucosa matures.
This is the reason why infants should not be started on solids foods too earlier – also the types of solid foods they eat affect this.

74. Fiber
Insoluble cellulose compounds that are indigestible by our digestive system
Fiber increases the strength of the colon contractions and holds water to soften the feces
Imbalances: diverticulitis, diverticulosis

75. Large Intestine
Bacteria in your LI have 5 main byproducts: (list on quiz)
H2 gas
CO2 gas
CH4 gas (methane)
H2S (hydrogen sulfide – rotten egg smell!)
Vitamins K and some B vitamins

76. Other Facts
Feces are semisolid products delivered to the rectum for excretion
They contain undigested food, residues, mucus, cells, bacteria, and water
The Valsalva maneuver involves voluntarily closing the glottis and contracting the abdominal muscles & the diaphragm to force feces distally

77. Ileostomy
When large intestine is removed due to disease process, a portion of the ileum is sutured into an opening in the abdominal wall
Feces are excreted through this opening into a pouch.

78. Anorexia & Bulemia
Anorexia: process of overexercise & refusal to eat produces wasting away of body tissue – can lead to heart failure
Bulemia: binge & purge cycle – person overeats then rids the GI tract of food by self induced vomiting and overuse of laxatives – can lead to ruptures of esophagus, loss of normal intestinal peristasis

80. Periodontal disease
Infection in pockets of gum lead to bone destruction

81. End of quiz #3 material
No diagrams