1. Cadaver dissection videos
Gastrointestinal:

2. The Digestive System Mouth---bite, chew, swallow
Pharynx and esophagus----transport
Stomach----mechanical disruption; absorption of water & alcohol
Small intestine--chemical & mechanical digestion & absorption
Large intestine----absorb electrolytes & vitamins (B and K)
Rectum and anus---defecation

3. Layers of the GI Tract 1. Mucosal layer 2. Submucosal layer
3. Muscularis layer
4. Serosa layer

4. Mucosa
Epithelium
stratified squamous (in mouth, esophagus & anus) = tough
simple columnar in the rest
secretes enzymes and absorbs nutrients
specialized cells (goblet) secrete mucous onto cell surfaces
enteroendocrine cells---secrete hormones controlling organ function
Lamina propria
thin layer of loose connective tissue
contains BV and lymphatic tissue
Muscularis mucosae---thin layer of smooth muscle
causes folds to form in mucosal layer
increases local movements
movements increase absorption
with exposure to “new” nutrients

5. Submucosa Loose connective tissue Meissner’s plexus
containing BV, glands and lymphatic tissue
Meissner’s plexus
parasympathetic
innervation
vasoconstriction
local movement by muscularis mucosa smooth muscle

6. Muscularis Skeletal muscle = voluntary control
in mouth, pharynx, upper esophagus and anus
control over swallowing and defecation
Smooth muscle = involuntary control
inner circular fibers & outer longitudinal fibers
mixes, crushes & propels food along by peristalsis
Auerbach’s plexus (myenteric)
both parasympathetic & sympathetic innervation of circular and longitudinal smooth muscle layers

7. Serosa An example of a serous membrane
Covers all organs and walls of cavities not open to the outside of the body
Secretes a serous fluid
Consists of connective tissue covered with simple squamous epithelium

8. Peritoneum Peritoneal cavity
potential space containing a bit of serous fluid
Contains most of the digestive organs
A sheet of serosa forms the peritoneal cavity
Serosa is known as the Peritoneum
Cavity within the abdomen that contains the viscera
Formed by a parietal layer
visceral layer covers organs

9. Serosa also forms connections from the parietal peritoneum to several organs in the cavity = Mesenteries
4 kinds:
Mesentery – parietal peritoneum to small intestines
Mesocolon – parietal peritoneum to large intestine (colon)
Lesser omentum
Greater omentum
The 4 Mesenteries

10. The path of food: oral cavity/teeth/salivary glands
oropharynx/epiglottis
esophagus
stomach
small intestine: duodenum
small intestine: jejunum
small intestine: ileum
large intestine: ascending colon
large intestine: transverse colon
large intestine: descending colon
sigmoid colon
rectum
anus

11. Mouth Oral cavity proper---the roof = hard, soft palate and uvula
floor – geniohyoid, mylohyoid – contains the tongue
lips and cheeks-----contains buccinator muscle that keeps food between upper & lower teeth
Vestibule---area between cheeks and teeth
Lined with an oral mucosa (stratified squamous epithelium & lamina propria)
Lining of the cheeks = buccal mucosa
Lining of the maxilla and mandible = alveolar mucosa (gingiva)
Landmarks: lingual frenulum, labial frenulum, uvula
Shortened lingual frenulum can impede movement of the tongue within the mouth

12. Tubal tonsil
Geniohyoid
Mylohyoid
Epiglottis
Vocal cords
Lingual tonsil
Larynx
Oropharynx
Nasopharynx
Laryngopharynx

13. Pharyngeal Arches
Two arches skeletal muscles that elevate the soft palate when we swallow
Closes off the nasopharynx and directs food into the oropharynx
First arch = Palatoglossal muscle
extends from palate down to tongue
uvula dangles from the middle of this arch
forms the boundary between the oral cavity and oropharnyx
Second arch = Palatopharyngeal muscle
extends from palate to pharyngeal wall
part of the oropharynx
found behind the palatine tonsil

14. Structure and Function of the Tongue
Muscular structure covered with an oral mucosa
Muscle of tongue is attached to hyoid, mandible, hard palate and styloid process
Two groups of muscles
1. Intrinsic muscles
Change the shape of the tongue
Organized as transverse muscles, longitudinal and vertical muscles
2. Extrinsic muscles
move the tongue in the oral cavity
Styloglossus, palatoglossus & hyoglossus
Geniohyoid & genioglossus

15. Salivary Glands Parotid below your ear and over the masseter
Submandibular is under lower edge of mandible
Sublingual is deep to the tongue in floor of mouth
All have ducts that empty into the oral cavity (exocrine glands)
Classified either as: serous or mixed
Wet food for easier swallowing
Dissolves food for tasting
Bicarbonate ions buffer acidic foods
Helps build stronger enamel
Chemical digestion begins with enzyme salivary
amylase & lingual lipase
Also contains lysozyme ---helps destroy bacteria
Protects mouth from infection with its rinsing action
Serous glands - cells secrete a watery fluid – e.g. parotid
Mixed glands secrete both mucus and a serous fluid – e.g. submandibular & sublingual

16. secretes the enzyme Salivary amylase
Parotid gland
secretes the enzyme Salivary amylase
Submucosa
layer of the tongue secretes
Lingual lipase
Parotid
Sublingual
Submandibular

17. Salivation Parasympathetic nerves - Increase salivation
sight, smell, sounds, memory of food, tongue stimulation---rock in mouth
cerebral cortex signals the salivatory nuclei in brainstem
carried by parasympathetic nerves = CN 7 & 9
Sympathetic nerves - Stop salivation
dry mouth when you are afraid
sympathetic nerves

18. Teeth: -grinding, tearing and shearing of food
-two main divisions: crown and root
-crown: above gumline/gingiva
-covered with a layer of enamel
-root: below the gumline, embedded in the alveolar socket of the jaw
-entry of nerves and blood vessels via the apical foramen
-root is secured in the jaw by two tissues: cementum & periodontal membrane/ligament
-neck – where crown and root meet
-gingiva should form a tight a seal at this area
-inside of the tooth = pulp (nerves/blood vessels)
-nerves and BVs enter the root via apical foramen
and travel through root canals to enter the pulp cavity
-tooth is formed of a calcified connective tissue called dentin
-dentin, enamel and cementum – made of calcium phosphate
very similar to bone

19. Primary and Secondary Dentition
-primary: 20 teeth starting at 6 months
-secondary/adult: between 6 and 12 years = 32 teeth
8 incisors
4 canines (cuspids)
8 premolars (bicuspids)
12 molars (tricupids)
** third pair of molars (wisdom teeth) may not erupt -impacted

20. Pharynx
Funnel-shaped tube extending from internal nares to the esophagus (posteriorly) and larynx (anteriorly)
Skeletal muscle lined by mucous membrane
Deglutition or swallowing is facilitated by saliva and mucus
starts when bolus is pushed into the oropharynx
sensory nerves send signals to deglutition center in brainstem

21. Esophagus Collapsed muscular tube In front of vertebrae
Posterior to trachea
Posterior to the heart
Pierces the diaphragm at hiatus
hiatal hernia or diaphragmatic hernia
Esophagus
Mucosa = stratified squamous
Submucosa = large mucous glands
Muscularis = upper 1/3 is skeletal, middle is mixed, lower 1/3 is smooth
upper & lower esophageal sphincters are prominent circular muscle

22. Thoracic
Aorta
Esophagus
Diaphragm
Liver

23. Physiology of the Esophagus - Swallowing
Voluntary phase---tongue pushes food to back of oral cavity
Involuntary phase----pharyngeal stage
breathing stops & airways are closed
soft palate & uvula are lifted to close off nasopharynx
vocal cords close
epiglottis is bent over airway as larynx is lifted
controlled by autonomic nervous system
Peristalsis pushes food down
circular fibers behind bolus
longitudinal fibers in front of bolus shorten the distance of travel
Travel time is 4-8 seconds for solids and 1 sec for liquids
Lower sphincter relaxes as food approaches

24. Gastroesophageal Reflex Disease
If lower esophageal sphincter fails to open
distension of esophagus feels like chest pain or heart attack
If lower esophageal sphincter fails to close
stomach acids enter esophagus & cause heartburn (GERD)
for a weak sphincter---don't eat a large meal and lay down in front of TV
smoking and alcohol make the sphincter relax worsening the situation
Control the symptoms by avoiding
coffee, chocolate, tomatoes, fatty foods, onions & mint
take Tagamet HB or Pepcid AC 60 minutes before eating
neutralize existing stomach acids with Tums

25. Anatomy of Stomach Size when empty
large sausage
stretches due to rugae (folds in the mucosa caused by contraction of the m. mucosae)
Muscularis – three layers of smooth muscle
longitudinal
circular
oblique
Parts of stomach
Cardiac region
Fundus
Dody
Pyloric region---starts to narrow as
approaches pyloric sphincter
- Greater curvature
- Lesser curvature
Bolus of food enters and mixes with gastric juice  Chyme
Stomach empties as small squirts of chyme leave the stomach through the pyloric valve/sphincter

26. FUNDUS BODY PYLORIC REGION LESSER CURVATURE GREATER CURVATURE PANCREAS
DUODENUM
PYLORIC REGION
PANCREAS
GREATER CURVATURE
LESSER CURVATURE

27. Mucosa of the Stomach
simple columnar epithelium with embedded mucus cells
Mucosa forms columns of secretory cells = gastric glands that open into the stomach lumen through gastric pits
Chief cells secrete pepsinogen (inactive) into the stomach which will become pepsin (active) – for protein digestion
Parietal cells secrete H+ and Cl- ions into the stomach – become Hydrochloric acid
HCl converts pepsinogen into pepsin = protein digestion
Intrinsic factor (parietal cells)
absorption of vitamin B12 for RBC production
Gastrin hormone (G cells)
Increases gastric juice production, gastric motility and increase gastric emptying

28. Anatomy of the Small Intestine
20 feet long----1 inch in diameter
Large surface area for majority of absorption
3 parts
duodenum---10 inches
jejunum---8 feet
ileum---12 feet
ends at ileocecal valve

29. Lesser
Omentum
Liver
Stomach
Gallbladder
Descending
Colon
Transverse
Colon
Ascending
Colon
Mesentery of
Small Intestine
Small
Intestine

30. Small Intestine Structures that increase surface area plica circularis
permanent ½ inch tall folds in the mucosa
not found in lower ileum
cannot stretch out like rugae in stomach
villi
1 Millimeter tall
Core is lamina propria of mucosal layer
Contains vascular capillaries and lacteals (lymphatic capillaries)
microvilli
Found on the apical surface of absorptive cells
Gives the villus the appearance of a brush border

31. Small intestine - Mucosa
Absorptive cells
-project their microvilli into the lumen of the SI
-absorb amino acids and saccharides from food
Epithelial cells at the bottom of the villus form a gland = Intestinal gland
– production of intestinal juice or brush-border enzymes
Goblet cells – mucus production
Enteroendocrine cells
Found within the intestinal glands
Secrete three hormones
secretin
cholecystokinin
gastric inhibitory peptide
Paneth cells
secretes lysozyme
kills bacteria
Small intestine - Mucosa
Submucosal layer has duodenal glands
secretes alkaline mucus

32. Anatomy of Large Intestine
5 feet long by 2½ inches in diameter
Ascending & descending colon are retroperitoneal (not in the peritoneal cavity)
Cecum & appendix
Rectum = last 8 inches of GI tract anterior to the sacrum & coccyx
Anal canal = last 1 inch of GI tract
internal sphincter----smooth muscle & involuntary
external sphincter----skeletal muscle & voluntary control

33. Histology of Large Intestine
Muscular layer
internal circular layer is normal
outer longitudinal muscle can be seen from the outside
taeniae coli = shorter bands
Permanent contractions of these bands puckers the LI into pouches called haustra (also called diverticula)
epiploic appendages
Serosa = visceral peritoneum

34. Histology of Large Intestine
Mucosa
smooth tube -----no villi
intestinal glands found in the mucosa
simple columnar cells absorb water & goblet cells secrete mucus
Submucosal & mucosa contain lymphatic nodules

35. Defecation Reflex moves feces into rectum
Stretch receptors signal to the sacral spinal cord
Parasympathetic nerves contract muscles of rectum & relax internal anal sphincter
External sphincter is voluntarily controlled

36. Anatomy of the Pancreas
5" long by 1" thick
Head close to curve in C-shaped duodenum
pancreatic duct joins common bile duct from liver
Opens 4" below pyloric sphincter

37. Pancreatic Juice 1 + 1/2 Quarts/day at pH of 7.1 to 8.2
Contains water, enzymes & sodium bicarbonate
Digestive enzymes:
pancreatic amylase, pancreatic lipase, proteases (protein degradation)
Ribonuclease & deoxyribonuclease - digest nucleic acids

38. The 4 Proteases
Trypsinogen Trypsin
Enterokinase (intestines)
trypsinogen---activated by enterokinase (a brush border enzyme)
chymotrypsinogen----activated by trypsin
procarboxypeptidase-activated by trypsin
proelastase---activated by trypsin
Chymotrypsinogen Chymotrypsin
Trypsin
Proelastase Elastase
Trypsin
Procarboxypeptidase Carboxypeptidase
Trypsin

39. Anatomy of the Liver and Gallbladder
weighs 3 lbs.
below diaphragm
right lobe larger
gallbladder on right lobe
size causes right kidney to be lower than left
Gallbladder
fundus, body & neck

40. Right & Left
Hepatic Ducts
Common
Hepatic
Duct
Pancreatic
Duct
Gallbladder
Cystic Duct
Ampulla of Vater
Common Bile Duct

41. Blood Supply to the Liver
Hepatic portal vein
nutrient rich blood from stomach, spleen & intestines
splenic vein + superior mesenteric vein + inferior mesenteric vein
Hepatic artery branches off the Common hepatic artery (from the celiac trunk)
Splenic
Vein
Superior
Mesenteric
Hepatic
Portal
Common
Bile
Duct
Inferior

42. Histology of the Liver Hepatocytes arranged in lobules
Sinusoids in between hepatocytes are blood-filled spaces
Kupffer cells phagocytize microbes & foreign matter

43. Gallbladder Lined with simple columnar epithelium No submucosa
Three layers of smooth muscle
For the production of Bile
role in the absorption of fats
Stimulated by the presence of fat in the duodenum
Fat stimulates CCK production by SI which stimulates contraction of the gallbladder and the release of bile
Flow of Bile
Bile capillaries
Hepatic ducts connect to form common hepatic duct
Cystic duct from gallbladder & common hepatic duct join to form common bile duct
Common bile duct & pancreatic duct empty into duodenum

44. Types of Digestion Mechanical – mouth, stomach, SI, LI
Chemical – mouth, stomach, SI

45. Chemical Digestion in GI tract
Digestion of Proteins
Digestion of Carbohydrates
Stomach
HCl denatures or unfolds proteins
pepsin turns proteins into peptides
Pancreas
Proteases --split peptides into smaller peptides and dipeptides
Intestines
brush border enzymes-----aminopeptidase or dipeptidase------split off amino acid at amino end of a peptide (aminopeptidase) or split dipeptides into individual amino acids (dipeptidase)
Mouth---salivary amylase
Esophagus & stomach---nothing happens
Duodenum----pancreatic amylase
Brush border enzymes (maltase, sucrase & lactase) act on disaccharides
these enzymes produce the monosaccharides fructose, glucose & galactose
lactose intolerance (no enzyme; bacteria ferment sugar)--gas & diarrhea

46. Digestion of Nucleic Acids
Digestion of Lipids
Digestion of Nucleic Acids
Pancreatic juice contains 2 nucleases
ribonuclease which digests RNA
deoxyribonuclease which digests DNA
Nucleotides produced are further digested by brush border enzymes (nucleosidease and phosphatase)
pentose, phosphate & nitrogenous bases
Mouth----lingual lipase
Small intestine
emulsification by bile
pancreatic lipase---splits into fatty acids & monoglyceride
no enzymes in brush border

47. Digestion in the Mouth Mechanical digestion (mastication or chewing)
breaks into pieces
mixes with saliva so it forms a bolus
Chemical digestion
salivary amylase
begins starch digestion at pH of 6.5 or 7.0 found in mouth
when bolus & enzyme hit the pH 2.5 gastric juices hydrolysis ceases
lingual lipase
secreted by glands in tongue – Ebner’s glands
begins breakdown of triglycerides into fatty acids and glycerol

48. Stomach--Mechanical Digestion
Gentle mixing waves
every 15 to 25 seconds
mixes bolus with 2 quarts/day of gastric juice to turn it into chyme (a thin liquid)
More vigorous waves
travel from body of stomach to pyloric region
Intense waves near the pylorus
open it and squirt out 1-2 teaspoons full with each wave

49. Stomach--Chemical Digestion
Protein digestion begins
HCl denatures (unfolds) protein molecules
HCl transforms pepsinogen into pepsin that breaks peptides bonds between certain amino acids
Fat digestion continues
gastric lipase splits the triglycerides in milk fat
most effective at pH 5 to 6 (infant stomach)
HCl kills microbes in food
Mucous cells protect stomach walls from being digested with 1-3mm thick layer of mucous

50. Absorption of Nutrients by the Stomach
Water especially if it is cold
Electrolytes
Some drugs (especially aspirin) & alcohol
Fat content in the stomach slows the passage of alcohol to the intestine where absorption is more rapid
Gastric mucosal cells contain alcohol dehydrogenase that converts some alcohol to acetaldehyde-----more of this enzyme found in males than females
Females have less total body fluid that same size male so end up with higher blood alcohol levels with same intake of alcohol

51. Mechanical Digestion in the Small Intestine
1. Weak peristalsis in comparison to the stomach---chyme remains in SI for 3 to 5 hours
starts at the lower portion of the stomach and pushes the chyme forward
reaches the end of the ileum after 90 – 120 minutes
then another wave starts in the stomach
2. Segmentation---local mixing of chyme over the surface of the absorptive cells in the SI
does NOT push the food through the SI
moves chyme back and forth within a segment of the SI
done in specific segments
most rapid in the duodenum and slows at it reaches the ileum

52. Small Intestine-Chemical Digestion
Mucosal layer forms Intestinal glands = Crypts of Lieberkuhn
Glands secretes intestinal juice or brush border enzymes
-sucrase, maltase, lactase, dextrinase – dissacharides
-aminopeptidase or dipeptidase – peptides
-phosphatase - nucleic acids
-enterokinase – trypsin activation

53. Small Intestine-Chemical Digestion
-duodenum is also the site for secretion of the Pancreatic juice:
-trypsin, chymotrypsin, elastase, carboxypeptidase
-1-2 qt./day at pH 7.6
-enzymes are made in the pancreas as inactive forms
eg. trypsinogen, chymotrypsinogen, proelastase, procarboxypeptidase
-trypsin synthesized as trypsinogen - converted to trypsin by the enzyme enterokinase (brush border enzyme)
-activated trypsin then converts others into their active forms

54. Mechanical Digestion in Large Intestine
Done by the smooth muscle
Peristaltic waves (3 to 12 contractions/minute)
haustral churning----relaxed pouches are filled from below by muscular contractions (elevator)
gastroilial reflex = when stomach is full, gastrin hormone relaxes ileocecal sphincter so small intestine will empty and make room
gastrocolic reflex = when stomach fills, a strong peristaltic wave moves contents of transverse colon into rectum

55. Chemical Digestion in Large Intestine
No human digestive enzymes are secreted by the LI
only mucous – by the Goblet cells in the intestinal glands
Chyme that leaves the SI is acted upon by the action of bacteria (E.coli)
Bacteria actions:
ferment undigested carbohydrates  carbon dioxide & methane gas
breakdown undigested proteins - simpler substances (indoles, skatoles, hydrogen sulfide)----odor
turn bilirubin into simpler substances that produce color
Bacteria produce vitamin K and B in colon

56. Absorption & Feces Formation in the Large Intestine
food has now been in the GI tract for 3 to 10 hours
solid or semisolid due to water reaborption = feces
feces – water, salts, sloughed-off epithelial cells, bacteria, products of bacterial decomposition, unabsorbed and undigested materials
90% of all water absorption takes place in the SI – 10% in the LI
but the LI is very important in maintaining water balance
also absorbs some electrolytes---Na+ and Cl- and vitamins
dietary fiber = indigestible plant carbohydrates (cellulose, lignin and pectin)
soluble fiber – dissolves in water (beans, barley, broccoli, prunes, apples and citrus)
forms a gel that slows the passage of materials through the colon
also helps to lower blood cholesterol – binds to bile salts to prevent their reabsorption
liver must make more cholesterol to make more bile salts – takes this cholesterol from the blood
insoluble fiber – woody or structural parts of the plant (skins of fruits and vegetables, coatings around bran and corn)
passes though the colon relatively unchanged

57. Where will the absorbed nutrients go?

58. Absorption of Water 9 liters of fluid dumped into GI tract each day
Small intestine reabsorbs 8 liters
Large intestine reabsorbs 90% of that last liter
Absorption is by osmosis through cell walls into vascular capillaries inside villi

59. Liver Functions--Carbohydrate Metabolism
Turn proteins into glucose
Turn triglycerides into glucose
Turn excess glucose into glycogen & store
in the liver
Turn glycogen back into glucose as needed
Liver Functions--Protein Metabolism
Deamination = removes NH2 (amine group) from amino acids
Converts resulting toxic ammonia (NH3) into urea for excretion by the kidney
Synthesizes plasma proteins utilized in the clotting mechanism and immune system
Convert one amino acid into another
Liver Functions --Lipid Metabolism
Synthesize cholesterol
Synthesize lipoproteins----HDL and LDL (used to transport fatty acids in bloodstream)
Stores some fat
Breaks down some fatty acids

60. Other Liver Functions
Detoxifies the blood by removing or altering drugs & hormones (thyroid & estrogen)
Releases bile salts help digestion by emulsification
Stores fat soluble vitamins-----A, B12, D, E, K
Stores iron and copper
Phagocytizes worn out blood cells & bacteria
Activates vitamin D (the skin can also do this with 1 hr of sunlight a week)

61. Gallbladder Bile Production Simple columnar epithelium No submucosa
Three layers of smooth muscle
Serosa or visceral peritoneum
Bile Production
One quart of bile/day is secreted by the liver
yellow-green in color & pH 7.6 to 8.6
Components
water & cholesterol
bile salts = Na & K salts of bile acids
bile pigments (bilirubin) from hemoglobin molecule
Flow of Bile
Bile capillaries
Hepatic ducts connect to form common hepatic duct
Cystic duct from gallbladder & common hepatic duct join to form common bile duct
Common bile duct & pancreatic duct empty into duodenum