Introduction

• The organs of the digestive system are separated into two catagories :
  • the accessory digestive organs and the organs of the gastrointestinal ( digestive ) tract
• Digestive Tract :
  • ? composed of skeletal muscle and smooth muscle
  • organs of the digestive tract include the mouth , pharynx , esophagus , stomach , small intestine , and large intestine
• Accessory Digestive Organs :
  • include the teeth , tongue , gallbladder , digestive glands ( salivary glands , liver , and pancreas )
• Functions of the digestive system include :
  • ingestion , mastication , propulsion , mixing , secretion , digestion , absorption , and secretion

Peritoneum

• membrane which lines the walls and organs of the abdominal cavity
• the peritoneum has two portions : the visceral peritoneum and parietal peritoneum
• Visceral Peritoneum :
  • covers the external surface of the organs within the abdominal cavity
• Parietal Peritoneum :
  • lines the internal surface of the walls of the abdominal cavity
• the space between the two layers of peritoneum is the peritoneal cavity ( filled with peritoneal ( serous ) fluid )
• many organs of the abdominal cavity are held in place by ?
  • a mesentery is a fused double layer of peritoneum that extends from the body wall to a digestive organ
• other organs of the abdominal cavity are considered to be ?
  • lie against the posterior abdominal wall ( not suspended by a mesentery )
  • "retro" = "behind"
  • examples = pancreas , duodenum , rectum , ascending colon , descending colon , kidneys , ureters , abdominal aorta , inferior vena cava , urinary bladder

Oral Cavity

• associated structures include : lips , cheeks , palate , tongue , teeth , and salivary glands

• lips ( labia ) and cheeks :

  • composed mainly of muscle :
    • ? ( lips ) and the ? ( cheeks )
      • innervated by trigeminal and facial nerve
  • involved with the process of mastication and speech

• palate :

  • consists of two portions : the hard palate and soft palate
  • hard palate :
    • forms the " ?" of the mouth
    • tongue forces food against hard palate during chewing ( also plays a role in speech )
  • soft palate :
    • posterior to the hard palate
    • composed of ? ( closes off the nasopharynx when we swallow )

• tongue :

  • aids in chewing , swallowing , and speech

    

• salivary glands :

  • produce and secrete saliva
  • functions of saliva include :
    • ?
    • dissolves food chemicals so that they can be tasted
    • contains the enzyme salivary amylase ( begins chemical breakdown of starchy foods )
  • there are three pairs of salivary glands :
    • the parotid , submandibular , and sublingual glands
  • parotid glands :
    • one located anterior to each ear
  • submandibular glands :
    • ?
  • sublingual glands :
    • ?
    • much smaller

Pharynx

• "throat"
• food from the oral cavity passes through the ? into the oropharynx
• food then passes into the ?

Esophagus

• food passes from the laryngopharynx into the esophagus ( carries food into the stomach )
• lined with stratified squamous epithelium
• no digestion "starts" in the esophagus

Stomach

• food is broken down mechanically and chemically
• three layers of ? mechanically digest the food
• ? ( located in the lining of the stomach ) release substances that chemically digest the food
• major structures of the stomach include :
  • the cardiac sphincter , cardiac region , fundus , body , greater and lesser curvatures , pyloric region , pyloric sphincter , and rugae
• histology of the stomach :
  • the internal surface of the stomach is lined with simple columnar epithelium
  • the epithelium lining of the stomach contains ?
  • gastric pits are the openings for the ? ( produce gastric juice )
  • the highly acidic juice ( pH 1.5 to 3.5 ) contains substances that aid in chemical digestion
  • the substances that compose gastric juice are produced by the cells that form the gastric glands
  • cells of the gastric glands include :
    • mucous cells = different that goblet cells , special alkaline mucous , helps buffer acidity of gastric juice
    • parietal cells = produce $HCl$ and intrinsic factor for vitamin B₁₂
    • chief cells = produce pepsinogen. pepsinogen becomes activated into pepsin via acid produced from parietal cells
    • endocrine cells

Small Intestine

• digestive organ where digestion is completed and ?
• extends from the stomach to the large intestine
• 20 feet long in cadaver ( shorter in life due to muscle tone )
• divided into three parts : duodenum , jejunum , and ileum
• duodenum :
  • ?
  • wraps around the head of the pancrease
    • makes a "C" shape
  • lined with simple columnar epithelium
  • contains glands which produce an alkaline substance that ?
  • only a few inches long
• jejunum :
  • ? of small intestine
  • extends from duodenum to ileum
  • roughly 9 feet
• ileum :
  • ? of the small intestine
  • joins the cecum of large intestine
  • roughly 9 feet
• the small intestine has modifications which allow for an increase in surface area
  • this helps ? that takes place
• modifications that increase the surface area include :
  • overall length of the small intestine
  • the lining of the small intestine is folded ( ? ) and has tiny fingerlike projections called ?
    • plique circularis = circular folds
  • cells contain ?
• 2,700 square feet = surface area of small intestine

Liver

• second largest organ of the body
• largest gland in the body
• located in the ?
• major structures associated with the liver include : the right and left lobes , caudate lobe , quadrate lobe , and hepatic porta
• functions of the liver include :
  • ?
  • takes waste products out of the blood
  • hepatocytes of the liver produce ? ( stored in the gallbladder )
    • bile helps digest fats
• ducts associated with the liver include :
  • the common heptatic duct , right and left hepatic ducts , cystic duct , and common bile duct
• the ? carries bile away from the liver
  • formed by the union of the right and left hepatic ducts
• the common hepatic ducts joins the ? ( from the gallbladder ) to form the ?
• the common bile duct joins the ? ( from the pancreas ) and forms the hepatopancreatic ampulla ( ampulla of vater )
  • cholecystokinin ( CCK ) relaxes sphincter of Oddi
• the hepatopancreatic ampulla drains via the ? into the duodenum of the small intestine

Bile Pathway

1. Right and Left Hepatic Ducts
2. Merge to form common hepatic duct
3. Cystic Duct merges with common hepatic duct
4. Common Bile Duct
5. Pancreatic Duct
6. Ampulla of Vater
7. Major Duodenal Papilla

Pancreas

• located in the abdomen partially ?
• remember ... the pancreas is an exocrine and endocrine gland
• substances produced by the endocrine portion of the pancreas include :
  • ? , ? , ?
• substances produced by the exocrine portion of the pancreas include :
  • ? that aid in digestion of carbohydrates , fats , and proteins in the small intestine
  • ? ( $HCO_3^{-}$ ) ions that neutralize acidic chyme in small intestine
• exocrine pancreatic secretions exit the pancreas via the pancreatic duct

Large Intestine

• around 5 feet in length
• extends from the small intestine to the anus
• functions of the large intestine include :
  • ? ( absorption of nutrients completed in small intestine )
  • elimination of waste products ( feces )
• divisions of the large intestine include :
  • the cecum , colon , rectum , and anal canal
• cecum :
  • ? of large instestine
  • joins with ileum of small intestine ( ileocecal junction )
  • the veriform appendix is attached to the cecum
    • ? , can collect bacteria
• colon :
  • consists of the ascending colon , right colic ( hepatic ) flexure , transverse colon , left colic ( splenic ) flexure , descending colon , and sigmoid colon
• rectum :
  • portion of large intestine located between the sigmoid colon and anal canal
  • stores feces
    • possible fecal impaction
• anal canal :
  • last 2 - 3 cm of the digestive tract
  • extends from the rectum to the anus ( opening of the anal canal to the "outside" world )
  • surrounded by the internal and external sphincters
    • internal anal sphincters composed of ?
    • external anal sphincters composed of ?

Digestive Pathway

1. Mouth
2. Oral Cavity
3. Fauces
4. Oral Pharynx
5. Laryngopharynx
6. Esophagus
7. Lower Esophageal Sphincter ( cardiac sphincter )
8. Cardiac Region of Stomach
9. Body of Stomach
10. Pyloric Region of Stomach
11. Pyloric Sphincter of Stomach
12. Duodenum of Small Intestine
13. Jejunum of Small Intestine
14. Ileum of Small Intestine
15. Ileocecal Juction
16. Cecum of Large Intestine
17. Ascending Colon of Large Intestine
18. Hepatic Flexure of Large Intestine
19. Transverse Colon of Large Intestine
20. Splenic Flexure of Large Intestine
21. Descending Colon of Large Intestine
22. Sigmoid Colon of Large Intestine
23. Rectum of Large Intestine
24. Anal Canal of Large Intestine
25. "flush"

Histology Questions

1. The esophagus is lined with ?
   • ?
2. The Stomach is lined with ?
   • ?
3. What is the function of the mucous cells ?
   • ?
4. What is the function of parietal cells ?
   • ? ( gastric acid )
5. What is the function of chief cells ?
   • ?
6. What is the function of enteroendocrine cells ?
   • ?
7. How to identify parietal cell ?
   • ?
8. How to identify chief cells ?
   • ?
9. How to identify enteroendocrine cells ?
   • ?
10. What is the function of the circular folds , villi , and microvilli ?
    • ?
11. What is the function of goblet cells ?
    • ?
12. What is the function of Brunner's Glands ?
    • ?
13. What is the function of Peyer's Patches ?
    • ?
    • ?
14. Where are Peyers's Patches located ?
    • ?