1. Anatomy and Physiology Chapter 21 - Digestive System I, II
Martini’s Visual
Anatomy and Physiology
First Edition
Martini w Ober
Chapter 21 - Digestive System I, II
Lectures 7 & 8
100 min, 52 slides

2. Lecture Overview (Lectures 7 & 8)
Introduction to the digestive system
General characteristics of the alimentary canal
The mouth and tongue
Salivary glands
Pharynx and esophagus
Stomach
Pancreas

3. Digestive System Functions of Digestive System ingestion
mechanical digestion
chemical digestion
propulsion
absorption
excretion
defecation
Digestion is the mechanical and chemical breakdown of food into a form that cells can absorb

4. Major Organs of Digestive System
Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007
Organs can be divided into the:
Digestive tract (primary) (alimentary canal); tube extending from mouth to anus (about 30 ft.)
Accessory organs; teeth, tongue, salivary glands, liver, gallbladder, and pancreas

5. The Greater and Lesser Omenta
Omentum: One of the folds of the peritoneum that connect the stomach with other abdominal organs.
Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

6. The Mesentery
Mesentery: Any of several folds of the peritoneum that connect the intestines to the dorsal abdominal wall, especially such a fold that envelops the jejunum and ileum.
Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

7. The Abdominal Cavity & Peritoneum
Notice that the pancreas, duodenum, and rectum are retroperitoneal
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

8. Alimentary Canal
Continuous tube modified along its length to carry out specialized, regional functions.
Mouth, pharynx, esophagus, and anal canal are lined by nonkeratinized stratified squamous epithelium
Stomach and intestines are lined by simple columnar epithelium.
Why?
105 min; 54 slides

9. Alimentary Canal Wall Know the 4 layers of the alimentary canal
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

10. Alimentary Canal Wall

11. Movements Through the Alimentary Canal
mixing movements (segmentation)
peristalsis - The wavelike muscular contractions of the alimentary canal or other tubular structures by which contents are forced onward toward the opening. (Triggered by pacesetter cells.)

12. Innervation of the Alimentary Canal
The alimentary canal has extensive sympathetic and parasympathetic innervation - mainly in the muscularis externa regulates its tone and the strength, rate, and velocity of muscular contractions
submucosal plexus – controls secretions/blood flow
myenteric plexus – controls gastrointestinal motility/sphincters
parasympathetic division of ANS – increases activities of digestive system and relaxes sphincters
sympathetic division of ANS – generally inhibits digestive actions and contracts sphincters

13. Mouth (Oral or Buccal cavity)
(Labium)
ingestion
mechanical digestion
prepares food for further chemical digestion
The lips (labia) are formed by the orbicularis oris muscle covered with keratinized skin. The red margin is what we normally think of as the lips. This is very thin and poorly keratinized with no sweat or sebaceous glands (must be kept moist by saliva).
Palatoglossal arches in front; palatopharyngeal arches behind. Between these two arches are the fauces, containing the palatine tonsils.
(Labium)
Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

14. Tongue
Very muscular; muscles run in several directions Covered by mucous membranes
Blast from the past - Root of tongue is anchored to the hyoid bone
Tastebuds
Friction for food handling
Secretes lingual lipase
Filiform papillae roughen surface of tongue to provide friction for food handling. Fungiform papillae Circumvallate (vallate) papillae aligned in a V-shaped row on back of tongue. Foliate papillae are pleat-like folds on posterolateral portion of tongue. (Fungiform, circumvallate, and foliate papillae contain taste buds.)
Lingual tonsils are located on posterior of tongue.
Sensory fibers are CN IX and chorda tympani branch of CN VII. CN XII innervates tongue muscle.

15. Palate roof of oral cavity
(adenoids)
Important in separating the nasopharynx from the pharynx during swallowing
Muscles of the soft palate include: 1. Tensor Palati, 2. Levator Palati, 3. Palatoglossus, 4. Palatopharyngeus, and the 5. Superior Constrictor

16. Secondary (Permanent) Teeth
Total of 32 secondary (permanent) teeth 1 16
Watch for incoming ICBMs!!! 32 17
Know the order of these
Dental formula: /

17. Primary (Deciduous, Baby, Milk) Teeth
(Mastication = chewing)
8 incisors
4 cuspids
8 molars
20 total
Dental formula: /
All primary teeth are lost, generally between ages 6 and 12

18. Section of a Tooth What type of articulation is this?
Oh no! Not again!
What type of articulation is this?
Know this diagram for exam

19. Functions of Saliva Moistens food Binds food particles
Dissolves food for tasting
Begins chemical digestion of complex CHO (amylase)
Cleans teeth and mouth (pH = 6.5 – 7.5)
Anti-microbial (IgA and lysozyme)
Saliva is hypotonic, alkaline containing K+, HCO3-, Ca2+, Mg2+, PO43-. Ca/Po4 prevents demineralization of tooth enamel.

20. Salivary Glands
Parasympathetic – CN VII and IX; sympathetic via cervical sympathetic chain.

21. Secretions of Salivary Glands
Secretions are slightly acidic and continual due to basal parasympathetic stimulation, but increase after
- presence, or anticipation of, food; - parasympathetic stimulation (watery, large volume) - sympathetic stimulation (viscous, small volume)
Parotid glands
clear
primarily water, serous fluid
rich in amylase
mumps virus typically attacks here
Food in mouth stimulates the nucleus of the tractus soliarius and this stimulates the salivatory nuclei in the pons/medulla send signals to salivary glands via the facial and glossopharyngeal nerves
Submandibular glands
primarily serous fluid
some mucus, amylase
Sublingual glands
primarily mucus
most viscous

22. Pharynx
Superior, middle, and inferior constrictor muscles. Motor and sensory fibers in CN IX and CN X.
Pharynx aids swallowing by grasping food and moving it toward the esophagus.

23. Three Phases of the Swallowing Reflex
Only voluntary phase is the buccal (oral) phase, i.e., the initiation of swallowing, then…
soft palate and uvula raise
hyoid bone and larynx elevate
Pharyngeal phase
epiglottis closes off top of trachea
longitudinal muscles of pharynx contract
reflexive
inferior constrictor muscles relax and esophagus opens
Esophageal phase
peristaltic waves push food through pharynx

24. Swallowing Mechanism
Muscles that elevate the hyoid/larynx: digastric, stylohyoid, mylohyoid, and geniohyoid.

25. Esophagus
Veins drain into hepatic portal vein (via gastric veins)
Esophagus is about 25 cm long. Straight course through the mediastinum. Solid foods pass from the oropharynx to the stomach in about 8 sec.; fluids in about 1-2 sec.
Innvervated by CN X (via connection with myenteric plexus).
Lower esophageal (cardiac) sphincter prevents reflux (backup) of stomach acid into the esophagus.
Esophagus conveys food from pharynx to stomach by peristalsis

26. Stomach Rugae flatten as stomach fills
Stomach can hold about liters of material
Gastric glands
M G cells D cells
Greater curvature
Stomach Functions: - Mixing - Reservoir - Secretion of gastric juice - Digestion, anti-bacterial action, facilitates absorption of vitamin B Secretion of gastrin, somatostatin
Range of stomach volume is about 50 ml (empty) to about 4L (very distended).
Rugae flatten as stomach fills

27. Blood Supply and Drainage of Stomach
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

28. Lining and Gastric Glands of Stomach
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

29. Gastric Secretions mucus (cardia) from goblet cells and mucous glands
protective to stomach wall
hydrochloric acid
from parietal cells
needed to convert pepsinogen to pepsin
‘p’ in parietal and ‘p’ in pH
pepsinogen
from chief cells
inactive form of pepsin
intrinsic factor
from parietal cells
required for vitamin B12 absorption
pepsin
from pepsinogen in presence of HCl
protein splitting enzyme
mucus, gastrin, somatostatin
from pyloric glands
protective to stomach wall
gastrin and somatostatin are hormones
H.Pylori is difficult to eradicate, so three medications are used simultaneously.
This is called "Triple Therapy". The best treatment at present is called OAC, taken for 7 days:
O = Omeprazole (which decreases the acid level in the stomach)
A = Amoxicillin (a penicillin antibiotic).
C = Clarithromycin (an antibiotic related to erythromycin)
OMC is used in those who are penicillin allergic, where M = Metranidazole.
INFANTS ONLY
rennin (chymosin)
gastric lipase

30. Secretion of H+ by Parietal Cells
Important functions of the stomach pH (1.5 – 2.0)
- kills microorganisms - denatures proteins - breaks down plant material and CT in meats - activates pepsin
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

31. Three Phases of Stomach Control
Cephalic phase
triggered by smell, taste, sight, or thought of food
begin secretion and digestion
Gastric phase
triggered by distension, presence of food, and rise in pH in stomach
enhances secretion and digestion
Intestinal phase
triggered by distension of small intestine and pH change
controls rate of gastric emptying; may slow emptying
NOTE that all these phases control activity in the STOMACH
Know what each phase does (shown in red)

32. Cephalic Phase of Gastric Secretion
Emotional states can exaggerate or inhibit this phase
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

33. Gastric Phase of Gastric Secretion
Secretion stimulated by: 1) ACh 2) histamine 3) gastrin. Small peptides and amino acids cause secretion of gastrin. Below pH 2, gastrin secretion is inhibited.
Proteins, alcohol, and caffeine can markedly increase secretions by stimulating gastric chemoreceptors
Histamine stimulates acid secretion by parietal cells
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

34. Intestinal Phase of Gastric Secretion
Enterogastric reflex (inhibits gastric activity) –reduces gastric motility, stimulates contraction of pyloric sphincter (pylorus)
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

35. Overview of Gastric Control/Secretion
Key +
Stimulation -
Mucous Cells
Inhibition
Emptying of Stomach
( [H+ ])
Stomach Molility (Segmentation/Peristalsis)
ECL Cells
Histamine
Endocrine Factor + + +
Exocrine Factor +
(cephalic/gastric phases)
Parasympathetic NS
G cells
Gastrin +
Both +
D cells
Somatostatin
Intrinsic Factor +
B12
Parietal Cells
pH < 3.0 - +
H+ + Cl-
HCO3- (alkaline tide) + + + + +
(intestinal phase)
Stretch of stomach
Fats in Small Intestine
pH > 3.0 (dilution of H+)
Peptides
Chief Cells
Pepsinogen
Pepsin
Protein Breakdown
Food in Stomach
Fat Breakdown
Lipases

36. Mixing and Emptying Actions

37. Gastric Absorption Gastric absorption is very limited due to:
- blanket of mucus covering cells - epithelial cells lack specialized transport mechanisms - tight junctions between adjacent epithelial cells - gastric lining is relatively impermeable to water - chyme usually contains only partially digested material
Some substances can be absorbed by the stomach:
some water
certain salts
certain lipid-soluble drugs, e.g., aspirin
alcohol (slowed by presence of fats)

38. Pancreas Exocrine (digestive) and endocrine (metabolic) functions
Completes digestion of proteins that was started in the stomach

39. Blood Supply and Drainage of Pancreas
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

40. Pancreatic Juice
pancreatic amylase – splits glycogen into disaccharides
pancreatic lipases – break down triglycerides
pancreatic nucleases – digest nucleic acids
bicarbonate ions – make pancreatic juice alkaline (pH = 8) and neutralize acid coming from stomach
Pancreatic proteolytic enzymes…

41. Pancreatic Proteolytic Enzymes
Enteropeptidase (Enterokinase) (brush border of sm. intestine)
Know this chart
Trypsinogen
Trypsin
Chymotrypsinogen
Chymotrypsin
Pancreas
Procarboxypeptidase
Carboxypeptidase
Proelastase
Elastase
(Proenzymes, Zymogens)
(Active enzymes)
Dipeptides, tripeptides, amino acids
Proteins
Purpose of proteolytic enzymes is continued breakdown of proteins that began in the stomach

42. Regulation of Pancreatic Secretions
acidic chyme stimulates release of secretin
secretin stimulates release of watery pancreatic juice with bicarbonate and phosphate (= buffers; to  pH) CCK and parasympathetic NS stimulate production and secretion of pancreatic enzymes and zymogens
The acini of the pancreas secrete enzymes/zymogens; the ducts secrete buffers (bicarbonate, phosphates)

43. Regulation of Pancreas/Intestinal Digestion
Key +
Stimulation
Acidic Chyme Enters Duodenum +
(brush border) + +
Enterokinase
Cholecystokinin (CCK)
Secretin +
Trypsinogen
Trypsin + + +
Gallbladder Contraction
Relaxation of hepatopancreatic sphincter
Chymotrypsinogen Procarboxypeptidase Proelastase
Trypsinogen Carboxypeptidase Elastase
Pancreas
Bile and Pancreatic ducts
(proenzymes, zymogens)
Proteins
Bile
Lipases
HCO3-, PO43-
(emulsification)
Nucleases (DNA, RNA)
Amylase (glycogen, starches)
Di- and tripeptides
Triglycerides Cholesterol Fat Soluble Vitamins
 pH to ≈ 8 (req. for enzyme action)
Nucleotides
Mono-, di-, trisaccharides
Action of brush border enzymes
Fatty acids, monoglycerides
Lacteals
Portal Vein
Amino acids
Conversion to chylomicrons
Subclavian vein
Monosaccharides

44. Review Alimentary canal (direct contact with food)
Mouth, pharynx, esophagus, stomach, small and large intestines, anal canal
Accessory structures (no direct contact with food, but provide secretions)
Salivary glands, liver, gall bladder, pancreas
Four layers of the alimentary canal
Mucosa – absorption, secretion, protection
Submucosa – nutrition and transport
Muscularis – movement
Serosa – protection, lubrication

45. Review Wave-like movement of alimentary canal is called peristalsis
Results from stretching
Bowel sounds
Innervation of the alimentary canal (enteric nervous system)
Parasympathetic – increases activity
Sympathetic – decreases activity
Mouth
Mastication – mechanical processing of food and mixing with saliva

46. Review Tongue Palate (roof of oral cavity) Lined by mucous membranes
Thick, skeletal muscle
Papillae function in food handling and taste
Lingual frenulum
Lingual tonsils
Lingual glands secrete lingual lipase
Palate (roof of oral cavity)
Hard palate (Palatine proc. of maxillary bones)
Soft palate
Uvula is suspended from this
Uvula closes opening to nasal cavity (nasopharynx)

47. Review Tonsils Teeth Lingual (back of tongue)
Palatine (lateral to tongue)
Pharyngeal (posterior wall of pharynx; adenoids)
Teeth
Primary teeth (deciduous teeth; baby teeth)
6 months to 2-4 years
20 total
Secondary (permanent teeth)
6 yrs to years
32 total

48. Review Teeth (continued) Incisors – sharp for biting
Cuspids (canine) – for grasping/tearing
Bicuspids and molars – grinding
Structure
Crown – above gum line
Root – below gum line
Outer covering is enamel
hardest substance in body
NOT replaceable
Inner substance is dentin (alive)
Pulp cavity
Periodontal ligament

49. Review Alimentary canal (direct contact with food)
Mouth, pharynx, esophagus, stomach, small and large intestines, anal canal
Accessory structures (no direct contact with food)
Salivary glands, liver, gall bladder, pancreas
Four layers of the alimentary canal
Mucosa – absorption, secretion, protection
Submucosa – nutrition and transport
Muscularis – movement
Serosa – protection, lubrication

50. Review Wave-like movement of alimentary canal is called peristalsis
Results from stretching
Bowel sounds
Innervation of the alimentary canal (enteric nervous system)
Parasympathetic – increases activity
Sympathetic – decreases activity
Mouth
Mastication – mechanical processing of food and mixing with saliva

51. Review Tongue Palate (roof of oral cavity) Lined by mucous membranes
Thick, skeletal muscle
Papillae function in food handling and taste
Lingual frenulum
Lingual tonsils
Lingual glands secrete lingual lipase
Palate (roof of oral cavity)
Hard palate (Palatine proc. of maxillary bones)
Soft palate
Uvula is suspended from this
Uvula closes opening to nasal cavity (nasopharynx)

52. Review Tonsils Teeth Lingual (back of tongue)
Palatine (lateral to tongue)
Pharyngeal (posterior wall of pharynx; adenoids)
Teeth
Primary teeth (deciduous teeth; baby teeth)
6 months to 2-4 years
20 total
Secondary (permanent teeth)
6 yrs to years
32 total

53. Review Teeth (continued) Incisors – sharp for biting
Cuspids (canine) – for grasping/tearing
Bicuspids and molars – grinding
Structure
Crown – above gum line
Root – below gum line
Outer covering is enamel
hardest substance in body
NOT replaceable
Inner substance is dentin (alive)
Pulp cavity
Periodontal ligament

54. Review Salivary glands produce saliva which
Moistens food
Binds food particles
Begins chemical digestion of CHO
Dissolves food (for taste)
Cleanses mouth and teeth; antibacterial
Three pairs of salivary glands
Parotid; front of ear, watery fluid rich in amylase
Submandibular; floor of mouth, viscous fluid
Sublingual; below tongue, thick, stringy secretion

55. Review Salivary glands Pharynx
Sympathetic stimulation – small quantity of viscous saliva
Parasympathetic stimulation – large volume of watery saliva
Pharynx
Cavity connecting mouth with esophagus
Nasopharynx, oropharynx, laryngopharynx
Muscles
Inner circular – constriction
Outer longitudinal – movement of food bolus

56. Review Swallowing Esophagus
Initiation is voluntary; act of swallowing is NOT – it’s a reflex
Three stages
Chewing and rolling of food into oropharynx (voluntary, buccal)
Swallowing reflex (pharyngeal)
Epiglottis closes over larynx
Muscles in lower pharynx relax
Esophagus opens and food moves in
Peristalsis in esophagus transports food to stomach (esophageal)
Esophagus
Muscular tube connects to cardiac region of stomach
Esophageal hiatus
Lower esophageal (cardiac) sphincter

57. Review Stomach Cardiac, fundus, body, pylorus
Mixes food and begins digestion of protein
Limited absorption (alcohol)
Moves food into small intestine
Pyloric sphincter (entrance to small intestine)
Rugae and gastric pits
Gastric glands
Mucous cells (goblet) – secrete mucous
Chief cells (peptic) – secrete digestive enzymes, esp. pepsinogen
Parietal cells (oxyntic) – secrete HCl (Parietal, pH)
Infants only - Gastric lipase and rennin

58. Review Regulation of gastric activity
Cephalic phase (primarily neural)
Prior to food entry into stomach
Increased motility and production of gastric juice
Gastric phase
Neural: Food entering stomach / pH rising
Hormonal: gastrin release
Local: histamine release (stimulates parietal cells)
Intestinal phase
Neural: distension of duodenum (enterogastric reflex)
Hormonal: CCK, GIP, and secretin, gastrin
Reduction (slowing) of gastric emptying

59. Review Pancreas Both exocrine and endocrine functions
Main source of intestinal digestive enzymes
Pancreatic amylase (starches)
Pancreatic lipase (fats)
Nucleases
Proteolytic proenzymes / enzymes
Regulation of pancreatic activity
Acid chyme stimulates secretin
Secretin stimulates watery buffering secretion
Parasympathetic NS and CCK stimulate production and secretion of digestive enzymes