The document provides an overview of the digestive system, including its main organs and their functions. It describes the mouth, esophagus, stomach, small intestine, large intestine, liver, gallbladder and pancreas. It explains that food is broken down mechanically and chemically by these organs, through processes like digestion and absorption, into nutrients that can be used by the body's cells. Key enzymes produced by organs like the stomach, pancreas and intestines help break down carbohydrates, proteins and fats during digestion.

1. The Digestive System
What happens to what we eat ??

2. Introduction
 Principal structure: GI tract also called
alimentary tube/canal
 Hollow tube 29 feet long in average adult
 General functions:
 Digestion mechanical & chemical food
breakdown & Absorption of nutrients
 Elimination of waste

3. Name that organ …

5. Primary Organs of Digestion
 Mouth
 pharynx
 esophagus
 stomach
 small intestine (duodenum,jejunum,ileum)
 large intestine (cecum ascending,
transverse descending, sigmoid)
 rectum
 anal canal

6. Accessory Organs
 teeth
 tongue
 salivary glands
 liver
 gall bladder
 pancreas
 appendix
 Salivary glands : parotid, submandibular,
sublingual

7. Gastric Disorders
 Disorders affecting the organs of the
digestive system
 Can you name a few???

8. Mechanism of Disease
1. Primary digestive organ affected
2. S/S
3. Dx/tests
4. Treatments
5. How is digestive SYSTEM affected?
Homeostasis altered?

12. Digestive Tract Wall Layers
 4 layers found within the lumen of the entire
digestive tract but specific tissue type comprising
each layer can vary from organ to organ
 Serosa: outermost, covers outside of dig organs.
Attaches dig tract to wall of abdominal pelvic
cavity by forming folds called mesenteries
 Muscularis: 2-3 layers of smooth muscular tissue
 Submucosa: connective tissue
 Mucosa: innermost, epithelial tissue

13. Peritoneum
 Serous membrane lining the abdominal
cavity & covers most digestive organs
 Parietal layer: lines abd. Cavity
 Visceral layer: covers organs
 Peritoneal space: between 2 layers which
contains peritoneal fluid (lubes for
breathing and digestive movements)

14. Extensions
 Extensions of peritoneum serve to suspend
organs in abd cav : carry nerves/bld vessels
to organs.
 Mesentary: Fan shaped extension between
the parietal and visceral layers of
peritoneum; anchors sm intestine to
posterior abd wall
 Greater omentum: Apron shaped pouchlike
extension of visceral peritoneum from
stomach, duodenum & transverse colon

16.  Peritonitis: inflammation (usually bacterial)
of peritoneum
 Ascites: accumulation of fluid in peritoneal
space

17. Mouth and Teeth
 Oral cavity; lined w/ mucous membrane
 Parts:
 Hard Palate: anterior bony structure on
roof of mouth Soft palate: posterior to
hard palate; made of muscular tissue
 Teeth 20 deciduous 32 permanent

18.  Uvula: cone shaped process, extending
from soft palate; prevents liquids from
entering nasal cavity, directs food down
 Tongue: skeletal muscle covered with
mucous membrane, anchored by hyoid
bone
 Frenulum: attaches tongue to floor of
mouth

19. 3 Salivary Glands
 3 pairs secrete 1L of saliva daily
 How by way of ducts that carry it to
digestive tract
 Parotids: largest, located below ears
 Submandibulars: post corners of mandible
 Sublinguals: below floor of mouth

21.  Saliva: mostly H2O which helps dissolve
food for tasting and moisten it for
swallowing
 Contain mucous and digestive enzyme
salivary amylase which begins process of
chemical breakdown of food

22. Pharynx
 Organ of respiratory &digestive system
 Swallowing (deglutition) is reflexive and
controlled by medulla.
 Esophagus
 Muscular tube lined w/ mucous membrane
 @ 10” long Posterior to trachea
 Passageway for food
 Junction of stomach : lower espohageal
sphincter (LES) contracts prevents backup
of stomach contents into esophagus

23. Esophageal inflamm d/t GERD

24. Stomach
 Inferior to diaphragm; “C” shaped in LUQ,
Stomach secretes both gastric acid (HCl and
enzymes) and mucus (for self protection)
pH: 1-2, necessary for enzyme (pepsin)
function and kills pathogens
 Temporary store for food which is also
churned by 3 muscular layers to form
chyme; a creamy semi-solid substance

26. Gastric Disorders
 Gastritis: inflammation of stomach lining;
acute or chronic
 Pyloric stenosis
 Ulcer: cause: helicobacter pylori bacterium.
Peptic or duodenal
 Hiatal Hernia: stomach protrudes thru
diaphragm
 Stomach CA
 Food Poisoning: eschericia coli common
cause

27. Small Intestine
 @ 20 feet long; smaller diameter than
large intestine.
 3 parts: duodenum, jejunum, ileum
 Digestion completed in small intestine.
End products of digestion are absorbed
into blood/lymph
 1000s of internal glands w/in the mucous
membrane lining secrete digestive juices
aids the chemical breakdown of chyme

29. Small Intestine Disorders
 Enteritis inflammation of small intestine
 Malabsorption Syndrome: failure to absorb
nutrients

30. Large Intestine
 5 ft long; @ 2.5” diameter
 Extends from ileum to anus.
 Divisions: cecum, ascending colon,
transverse colon, descending colon,
sigmoid colon, rectum and anal canal
 Passage of material takes 3-5 days
Functions: absorps H2O, minerals, vits
 eliminate indigestible material
 Undigested, unabsorbed food ( chyme)
changes to consistency of fecal matter
here as H2O and salts are reabsorbed

31. Large Intestine Disorders
 IBS: intermittent constipation/diarrhea.
Often d/t food sensitivity, inflammation,
genetics. Rarely serious
 Colitis: general name for any inflammation
of lg int. Generally, inflammation/ulceration
of rectum or small sections of colon
 Crohn’s Disease: inflammation /ulceration
may be accompanied by strictures of
intestines **often affects small intestine
 Colorectal CA
 Diverticulitis: inflammation of abnormal
outpouching of int. (grape like structures)

32. Intestinal Disorders
 Paralytic ileus: cessation of smooth muscle
contraction of intestine. Etiology . Surgical
complication or due to
inflammation/peritonitis
 Bowel Obstruction: caused by many
conditions. s/s: pain, nvd, abd distention
 Intussusception: telescoping of intestine

34. Liver/Gall Bladder
 Located in RUQ
 Liver: largest gland in the body
 Exocrine gland: secretes bile
 Has two major blood vessels: hepatic
artery & portal vein
 Liver cells many functions but digestive
function is the production of bile
 GB a small sac on undersurface of liver
concentrates & stores bile produced in
liver

36. Bile
 Composition mostly H2O.
 Excretory function: carries billirubin and
excess cholesterol to intestine for elimination
in feces
Digestive function accomplished by bile salts
which emulsify fats in small intestine
 Production of bile stimulated by hormone
(secretin)which is produced by duodenum
when food enters small int

37. Bile collects in bile caps w/in liver, which
merge to form bile ducts that drain into R &
L hepatic ducts, which in turn merge to
form the common hepatic duct
The cystic duct (from GB) joins with the
common hepatic duct to form the common
bile duct
Bile can drain directly into the duod via the
common bile duct or be temporarily stored
in the GB via the cystic duct
The common bile duct and the pancreatic
duct enter the duodenum together at the
Ampulla of Vater. The branchings of the bile
ducts are called the "biliary tree"

39. Liver/GB Disorders
 Cholelithiasis: gallstones; silent or
symptomatic occurs when bile has high
conc of chol
 Cholecystitis
 In a cholecystectomy the hepatic duct is
connected directly to the common bile duct
and dilute bile flows into duod
 Jaundice and biliary colic
 Hepatitis: virus causes inflamm &liver
damage

40. Liver GB Disorders
 Cirrhosis: liver scarring d/t etoh, hepatitis
virus or other viral organisms
 Portal Htn: ^ b/p in blood vessels
supplying liver distends veins in
esophagus and stomach; complication of
cirrhosis (esophageal varices)

41. Gallstones

42. 10. Pancreas
 Location LUQ Retroperitoneal organ located
posterior to the stomach on the posterior
abdominal wall
 Two functions:
 Exocrine glands: produce pancreatic juice
containing digestive enzymes
 Endocrine glands: produce insulin and
glucagon
 Main source of enzymes for digesting lipids
and proteins - the intestinal walls have
enzymes that digest CHO

43. Pancreas (stomach removed)

45.  Pancreatic secretions accumulate in
intralobular ducts that drain to the main
pancreatic duct, which drains directly into
the duodenum
 Digestive enzymes:
 Amylase: digests starch to maltose;
backup to salivary amylase
 Lipase: converts fats to fatty acids and
glycerol
 Trypsinogen: inactive enzyme that
activates in duodenum to trypsin which
digests polypeptides to amino acids

46. Pancreatic Disorders
 Pancreatitis: usually due to duct blockage
 Pancreatic CA
 Cystic Fibrosis: thickened secretions block
flow

47. 11. Appendix
 No digestive function
 Contains lymph tissue and may have
minor immune function
 Loc in RLQ and opens into the cecum and
the lumen of this opening is larger in
pediatrics and may be completely closed
in geriatrics

48. So how does it all work !
 The digestive system prepares food for
use by hundreds of millions of body’s cells.
 Food when eaten cannot reach cells
because it cannot pass through the
intestinal walls to the bloodstream and, if
it could it would not be in a useful
chemical state.

49.  The gut modifies food physically and
chemically and disposes of unusable waste
 Physical and chemical modification
(digestion) depends on exocrine and
endocrine secretions and controlled
movement of food through the digestive
tract.

50. Digestion, Absorption Metabolism
 Food undergoes 3 types of processing:
digestion, absorption and metabolism
 Digestion: altering of the physical composition
of food for absorption & use by the body’s cells
 Absorption: passage of food molecules through
internal membrane to bloodstream for use by
body’s cells
 Digestion & absorption performed by digestive
system
 Metabolism: use of various by-products from
digestive processes for chemical cellular
processes; performed by all body cells

51. Digestion
 Mechanical: breaks food into smaller pieces,
mixes it w/ digestive juices, moves it along
alimentary canal and eliminates waste
 Chemical: breaks down food into absorbable
molecules able to pass thru internal mucosa
into circulatory system
 3 primary types of substances that are
digested: carbs, proteins, fats

52. What is an enzyme?
 Much of the work of the digestive tract is
accomplished by enzyme activity
 Enzyme: biological catalyst. Necessary for
chemical digestion
 Most enzymes are proteins
 Each enzyme has specific shape due to
folding/looping of amino acid chains
 Substrate (subs to be altered) fits into part
of the enzyme called the active site
 Enzyme itself does not change but it
changes the substrate

53. Carb Digestion
 Mainly occurs in small intestine
 Pancreatic enzyme: amylase breaks
CHO(carbohydrates) into simpler maltose
 Intestional enzymes: maltase, sucrase and
lactase break down CHO into simpler
sugars, primarily glucose

54. Protein Digestion
 Begins in stomach where Pepsin, enzyme
in gastric juice, along w/ HCl simplifies
protein molecule
 In small intestine, trypsin from pancreatic
juice and peptidase from intestinal juice
break down the smaller protein molecules
into amino acids

55. Fat Digestion
 Fat is emulsified in duodenum by bile
 Then, pancreatic lipase breaks down fat
molecules into fatty acids and glycerol