1. The Digestive System Vocabulary Headings Important Info

2. Overview of GI tract Functions
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 & Anus: defecation

3. Layers of the GI Tract 1. Mucosal Layer
secretes enzymes & absorbs nutrients
2. Submucosal Layer
containing BV, glands & lymphatic tissue
3. Muscularis Layer
Skeletal:control over swallowing and defecation
Smooth: mixes, crushes & propels food along by peristalsis
4. Serosa Layer
Covers all organs and walls of cavities not open to outside of body
Secretes slippery fluid

4. Peritoneum Peritoneum Peritoneal Cavity visceral layer covers organs
parietal layer lines the walls of body cavity
Peritoneal Cavity
potential space containing a bit of serous fluid

5. 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

6. Composition and Functions of Saliva
Wet food for easier swallowing
Dissolves food for tasting
Protects mouth from infection with its rinsing action:
1 to 1 ½ qt/day
Bicarbonate ions buffer acidic foods
Bulimia---vomiting hurts the enamel on your teeth
Salivary Amylase (enzyme):
Starts chemical digestion of starch
Lysozyme (enzyme):
helps destroy bacteria

7. Mumps Myxovirus that attacks the parotid gland Symptoms
inflammation and enlargement of the parotid
fever, malaise & sour throat (especially swallowing sour foods)
swelling on one or both sides
Sterility rarely possible in males with testicular involvement (only one side involved)
Vaccine available since 1967

8. Structure and Function of the Tongue
Muscle of tongue is attached to hyoid, mandible, hard palate and styloid process
Papillae are the bumps:
taste buds are protected by being on the sides of papillae

9. Tooth Structure & Composition
Crown
Neck
Roots
Pulp cavity
Enamel
hardest substance in body
calcium phosphate or carbonate
Dentin
calcified connective tissue
Cementum
bone-like
periodontal ligament penetrates it

10. Dentition Permanent teeth differing structures indicate function
Primary/baby teeth
20 teeth that start 6months
1 new pair of teeth per month
Permanent teeth
32 teeth erupt b/t 6 & 12 years of age
differing structures indicate function
incisors for biting
Canines/cuspids for tearing
premolars & molars for crushing/grinding food

11. Primary and Secondary Dentition

12. Digestion in the Mouth Mechanical Digestion (Mastication/Chewing)
breaks into pieces
mixes with saliva forming: Bolus
Chemical Digestion
Amylase
begins starch digestion at:
pH of 6.5 or 7.0 found in mouth
when bolus & enzyme hit pH 2.5 gastric juices hydrolysis ceases
Lingual Lipase
secreted by glands in tongue
begins breakdown of triglycerides into fatty acids and glycerol

13. Pharynx
Funnel-shaped tube extending from internal nares to the esophagus (posteriorly) and larynx (anteriorly)
Skeletal muscle lined by mucous membrane
Deglutition/swallowing is facilitated by saliva and mucus
starts when bolus is pushed into the oropharynx
sensory nerves send signals to deglutition center in brainstem
soft palate is lifted to close nasopharynx
larynx is lifted as epiglottis is bent to cover glottis

14. 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

15. 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

16. Swallowing Upper sphincter relaxes when larynx is lifted
Peristalsis pushes food down
circular fibers behind bolus
longitudinal fibers in front of bolus shorten the distance of travel
Travel time:
4-8 seconds for solids
1 sec for liquids
Lower sphincter relaxes as food approaches

17. Gastroesophageal Reflex Disease
If lower sphincter fails to open
distension of esophagus feels like chest pain or heart attack
If lower sphincter fails to close
stomach acids enter esophagus & cause heartburn (GERD)
for a weak sphincter---don't eat a large meal & lay down in front of TV
smoking & alcohol make sphincter relax worsening situation
Control 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

18. Anatomy of Stomach Parts of stomach
Cardia
Fundus
Body
Pylorus:
starts to narrow as approaches Pyloric Sphincter
Empties as small squirts of chyme leave the stomach through the pyloric valve

19. Pylorospasm and Pyloric Stenosis
Abnormalities of the pyloric sphincter in infants
Pylorospasm
muscle fibers of sphincter fail to relax trapping food in the stomach
vomiting occurs to relieve pressure
Pyloric Stenosis
narrowing of sphincter indicated by projectile vomiting
must be corrected surgically

20. Histology of the Stomach

21. Mucosa & Gastric Glands
Hydrochloric acid converts pepsinogen from chief cell to pepsin
Intrinsic factor
absorption of vitamin B12 for RBC production
Gastrin hormone (g cell)
“get it out of here”
release more gastric juice
increase gastric motility
relax pyloric sphincter
constrict esophageal sphincter preventing entry

22. Muscularis Three layers of smooth muscle: Outer Longitudinal Circular
Inner Oblique
Permits greater churning & mixing of food with gastric juice

23. Physiology of Digestion— Mechanical vs. Chemical
Protein digestion begins
HCl denatures protein molecules
HCl transforms Pepsinogen into Pepsin
breaks peptide bonds b/t certain a.a.
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 w/ mm thick layer of mucous
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 pylorus
opens & squirts out 1-2 teaspoons full w/each wave

24. Cephalic Phase = “Stomach Getting Ready”
Cerebral Cortex:
sight, smell, taste & thought
stimulate PNS
Vagus Nerve:
increases stomach muscle and glandular activity

25. Gastric Phase = “Stomach Working”
Nervous control keeps stomach active
stretch receptors & chemoreceptors provide info
vigorous peristalsis and glandular secretions continue
chyme is released into duodenum
Endocrine influences over stomach activity
distention & presence of caffeine or protein cause G cells secretion of gastrin into bloodstream
gastrin hormone increases stomach glandular secretion
gastrin hormone increases stomach churning and sphincter relaxation

26. Intestinal Phase = “Stomach Emptying”
Stretch receptors in duodenum slow stomach activity & increase intestinal activity
Distension, fatty acids or sugar signals medulla
SNS slow stomach activity
Hormonal influences
secretin hormone decreases stomach secretions
Cholecystokinin (CCK) decreases stomach emptying
Gastric Inhibitory Peptide (GIP) decreases stomach secretions, motility & emptying

27. 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 w/higher blood alcohol levels with same intake of alcohol

28. Digestive Hormones Gastrin Gastric inhibitory peptide--GIP Secretin
stomach, gastric & ileocecal sphincters
Gastric inhibitory peptide--GIP
stomach & pancreas
Secretin
pancreas, liver & stomach
Cholecystokinin--CCK
pancreas, gallbladder, sphincter of Oddi, & stomach

29. Digestive Enzymes
When chyme enters the duodenum, proteins & carbohydrates are only partly digested, & fat digestion needs to be carried out
Enzymes aid in digestive breakdown & absorption of chyme
_____________________________________________________________
Bile Salts (Liver & Gallbladder) Pancreatic & Salivary Amylase (Pancreas & Mouth)
Fat  Fat Droplets Starch + H2O  Maltose
Trypsin & Pepsin (Pancreas)
Protein + H2O  Peptides
Lipase (Pancreas)
Fat Droplets + H2O  Glycerol + Fatty Acids
Peptidases (Intestinal Juice)
Peptides + H2O  Amino Acids
Maltase (Intestinal Juice)
Maltose + H2O  Glucose
Bile is a thick digestive fluid secreted by the liver and stored in gallbladder.
Facilitates digestion by emulsifying fats into fatty acids, which can be absorbed by the digestive tract

30. Vomiting (Emesis): Reverse Peristalsis
A deep breath is taken, the glottis is closed, and the larynx is raised to open the upper esophageal sphincter. Soft Palate is elevated to close of external nares
Diaphragm contracts down to create a negative pressure in the thorax, which facilitates opening of the esophagus and esophageal sphincter
Simultaneously with the downward movement of the diaphragm, the abdominal muscles contract elevating inner gastric pressure. With the pylorus closed and the esophagus open the exit route is clear

31. Anatomy of the Pancreas
5" long by 1" thick
Head close to curve in C-shaped duodenum
Main duct joins common bile duct from liver
Sphincter of Oddi on major duodenal papilla
Bile and pancreatic secretions enter the digestive system through this point
Opens 4" below pyloric sphincter

32. Composition and Functions of Pancreatic Juice
1.5 Quarts/day
pH 7.1 to 8.2
Contains water, enzymes & sodium bicarbonate
Digestive enzymes
pancreatic amylase, pancreatic lipase, proteases
Ribonuclease
to digest nucleic acids
deoxyribonuclease   
                                                                                                    

33. Pancreatitis Pancreatitis:
inflammation of the pancreas occurring with the mumps
Acute Pancreatitis:
associated with heavy alcohol intake or biliary tract obstruction
result is patient secretes trypsin in pancreas & starts to digest themselves

34. Regulation of Pancreatic Secretions
Secretin
acidity in intestine causes increased sodium bicarbonate release
GIP
fatty acids & sugar causes increased insulin release
CCK
fats and proteins cause increased digestive enzyme release

35. 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
The gallbladder stores about 50 ml of bile

36. Liver Functions—Carbohydrate Metabolism
Turn proteins  glucose
Turn triglycerides  glucose
Turn excess glucose  glycogen & store in the liver
Turn glycogen back  glucose as needed

37. Liver Functions: Lipid Metabolism
Synthesize cholesterol
Synthesize lipoproteins
HDL (high-density lipoprotein)
helps move cholesterol back to liver for removal from bloodstream (GOOD)
LDL (low-density lipoprotein)
helps cholesterol stick to artery walls (BAD)
Breaks down some fatty acids

38. Liver Functions: Protein Metabolism
Deamination = removes NH2 (amine group) from amino acids so can use what is left as energy source
Converts resulting toxic ammonia (NH3) into urea for excretion by the kidney
Synthesizes plasma proteins utilized in clotting mechanism and immune system
Convert one amino acid into another

39. Other Liver Functions
Detoxifies blood by removing or altering drugs & hormones (thyroid & estrogen)
Removes the waste product:
Bilirubin
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

40. Bile Production 1 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
Globin = a reuseable protein
Heme = broken down into iron and bilirubin

41. Pathway of Bile Secretion
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

42. Regulation of Bile Secretion

43. Blood Supply to the Liver
Hepatic Portal Vein
nutrient rich blood from stomach, spleen & intestines
Hepatic artery branch off the aorta

44. 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

45. Small Intestine Plica Circularis Villi Microvilli
permanent ½ inch tall folds that contain part of submucosal layer
not found in lower ileum
cannot stretch out like stomach
Villi
1 Millimeter tall
Contains vascular capillaries and lacteals (lymphatic capillaries)
Microvilli
Absorption and digestion
Digestive enzymes found at cell surface on microvilli
Digestion occurs at cell surfaces
Small Intestine

46. Small Intestine: Regions and Structures

47. Mechanical Digestion in Small Intestine
Weak peristalsis in comparison to the stomach:
chyme remains for 3 to 5 hours
Segmentation:
local mixing of chyme with intestinal juices
sloshing back & forth

48. Digestion of Carbohydrates
Digestion of Nucleic Acids
Mouth: salivary amylase
Esophagus & stomach: nothing happens
Duodenum: pancreatic amylase
Brush Border Enzymes (maltase, sucrase & lactose) act on disaccharides
produces monosaccharides--fructose, glucose & galactose
lactose intolerance (no enzyme; bacteria ferment sugar)--gas & diarrhea
Pancreatic juice contains 2 nucleases
ribonuclease which digests RNA
deoxyribonuclease which digests DNA
Nucleotides produced are further digested by brush border enzymes
Absorbed by active transport

49. Digestion of Lipids Digestion of Proteins Stomach Pancreas
HCl denatures or unfolds proteins
pepsin turns proteins into peptides
Pancreas
digestive enzymes: split peptide bonds b/t different amino acids
brush border enzymes: split off amino acid at amino end of molecule or split dipeptide
Mouth: lingual lipase
Small intestine
emulsification by bile
Pancreatic Lipase:
splits into fatty acids & monoglyceride
No enzymes in brush border

50. Absorption in Small Intestine

51. Absorption of Monosaccharides
Absorption into epithelial cell
glucose & galactose: sodium symporter(active transport)
Fructose: facilitated diffusion
Movement out of epithelial cell into bloodstream
by facilitated diffusion
Absorption of Amino Acids & Dipeptides
Absorption into epithelial cell
active transport w/Na+ or H+ ions
Movement out of epithelial cell into blood
diffusion

52. Absorption of Lipids
Small fatty acids enter cells & then blood by simple diffusion
Larger lipids exist only within micelles (bile salts coating)
Lipids enter cells by simple diffusion leaving bile salts behind in gut
Bile salts reabsorbed into blood & reformed into bile in the liver

53. Absorption of Electrolytes
Sources of electrolytes
GI secretions & ingested foods and liquids
Enter epithelial cells by diffusion & secondary active transport
sodium & potassium move = Na+/K+ pumps (active transport)
chloride, iodide and nitrate = passively follow
iron, magnesium & phosphate ions = active transport
Intestinal Ca+ absorption requires vitamin D & parathyroid hormone

54. Absorption of Vitamins
Fat-Soluble Vitamins
A, D, E, K
travel in micelles & are absorbed by simple diffusion
Water-Soluble Vitamins
Vitamin B complex, Ca
absorbed by diffusion
B12 combines with intrinsic factor before it is transported into the cells
receptor mediated endocytosis

55. 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

56. Anatomy of Large Intestine
5 feet long by 2½ inches in diameter
Ascending & descending colon are retroperitoneal
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

57. Appendicitis
Inflammation of the appendix due to blockage of the lumen by chyme, foreign body, carcinoma, stenosis, or kinking
Symptoms
high fever, elevated WBC count, neutrophil count above 75%
referred pain, anorexia, nausea and vomiting
pain localizes in right lower quadrant
Infection may progress to gangrene and perforation within 24 to 36 hours

58. Mechanical Digestion in Large Intestine
Smooth muscle: mechanical digestion
Peristaltic Waves
3 to 12 contractions/minute
Haustral Churning:
relaxed pouches filled from below by muscular contractions (elevator)
Gastroileal 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

59. Chemical Digestion in Large Intestine
No enzymes are secreted only mucous
Bacterial Fermentation
undigested carbohydrates into carbon dioxide & methane gas
undigested proteins into simpler substances (indoles)----odor
turn bilirubin into simpler substances that produce color
Bacteria produce vitamin K and B in colon

60. Absorption & Feces Formation in Large Intestine
Some electrolytes:
Na+ and Cl-
After 3 to 10 hours, 90% of H2O has been removed from chyme
Feces are semisolid by time reaches transverse colon
Feces = dead epithelial cells, undigested food such as cellulose, bacteria (live & dead)

61. Defecation Gastrocolic reflex moves feces into rectum
Stretch receptors signal sacral spinal cord
Parasympathetic nerves contract muscles of rectum & relax internal anal sphincter
External sphincter is voluntarily controlled

62. Defecation Problems Diarrhea Constipation
chyme passes too quickly through intestine
H20 not reabsorbed
Constipation
decreased intestinal motility
too much water is reabsorbed
Remedy = fiber, exercise and water

63. Dietary Fiber Insoluble Fiber Soluble Fiber
Woody parts of plants (wheat bran, veggie skins)
speeds up transit time & reduces colon cancer
Soluble Fiber
gel-like consistency
beans, oats, citrus white parts, apples
lowers blood cholesterol by preventing reabsorption of bile salts so liver has to use cholesterol to make more

64. Aging and the Digestive System
Changes that occur:
decreased secretory mechanisms & motility
loss of strength & tone of muscular tissue
changes in neurosensory feedback
diminished response to pain & internal stimuli
Symptoms:
sores, loss of taste, peridontal disease, difficulty swallowing, hernia, gastritis, ulcers, malabsorption, jaundice, cirrhosis, pancreatitis, hemorrhoids and constipation
Colon or rectum is common

65. Nutrition & Health Nutrient:
Substance used by the body for growth, maintenance, and repair
Nutrient:

69. Categories of Nutrients
Carbohydrates
Most are derived from plants
Exceptions: lactose from milk and small amounts of glycogens from meats
Lipids
Saturated fats from animal products
Unsaturated fats from nuts, seeds, and vegetable oils
Cholesterol from egg yolk, meats, and milk products
Proteins
Complete proteins – contain all essential amino acids
Most are from animal products
Legumes and beans also have proteins, but are incomplete
Vitamins
Most vitamins are used as cofactors and act with enzymes
Found in all major food groups
Minerals
Play many roles in the body
Most mineral-rich foods are vegetables, legumes, milk, & some meats

70. The sum of all chemical reactions necessary to maintain life
Metabolism
The sum of all chemical reactions necessary to maintain life
Catabolism
Substance is broken down to simpler products
Energy is released
Anabolism
Larger molecules are built from smaller ones
Energy Required

71. Basal Metabolic Rate (B.M.R.)
The amount of energy expended while at rest, (meaning that the digestive system is inactive, which requires about twelve hours of fasting in humans). Release of energy in this state is sufficient only for vital organ function
Wt (kg) = wt (lbs) / 2.2lbs/kg
Age BMR Equation (how many cal you need)
Males (60.9 x wt) - 54
(22.7 x wt) + 495
(17.5 x wt) + 651
(15.3 x wt) + 679
(11.6 x wt) + 879
>60 (13.5 x wt) + 487
Females (61.0 x wt) - 51
(22.5 x wt) + 499
(12.2 x wt) + 746
(14.7 x wt) + 496
(8.7 x wt)
>60 (10.5 x wt) + 596

72. Body Mass Index (B.M.I.)
1. Convert your weight in pounds to kilograms by
dividing by 2.2
161lbs / 2.2kg = 73.18kg
2. Convert your height in feet to inches (1 foot = 12 inches).
5’5’’ = 65’’
3. Convert your height to meters: multiply your height in inches by Then divide by 100
65’’ x 2.54 = 165.1m
165.1m/100 = 1.651
4. Multiply your height (in meters) by itself. 
1.651 x =
5. Divide your weight in kilograms (step 1) by your height squared (step 4) 
73.18kg/ m2 =
B.M.I. of 26.85
(Mrs. Warren is Overweight—Yikes!—see ya at LA Fitness)

73. BMI Categories Underweight: Less than 18.5 Normal Weight: 18.5 - 24.9
Overweight:
Obese: 30 or higher