1. ESOPHAGUS

2. Hiatal (diaphragmatic) Hernia

3. Histology of the Esophagus
Wall has 3 layers:
Mucosa  stratified squamous
Normal 3 layers.
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
Skeletal and smooth
Figure 24.9

4. Histology of the Esophagus
Adventitia
Outermost layer of esophagus
Connective tissue
Blends with surrounding connective tissue
No peritoneum
Differences from serosa
Serosa  lubrication  secretions
Adventitia  binds structures  no secretions
Figure 24.9

5. Physiology of the Esophagus - Deglutition
Figure 24.10
Physiology of the Esophagus - Deglutition
Moves bolus from the mouth to the stomach.
Facilitated by saliva and mucus.
Involves the mouth, tongue, pharynx, and esophagus.
It consists of 3 stages:
Voluntary stage
Pharyngeal stage
Esophageal stage

6. Physiology of the Esophagus - Deglutition
Figure 24.10
Physiology of the Esophagus - Deglutition
Voluntary stage
Food: Tongue  back of oral cavity  oropharynx
Pharyngeal stage
Moves food from pharynx to esophagus
Receptors in oropharynx stimulate deglutition center in M.O.
Breathing stops and airways are closed
Uvula and soft palate lift to close off nasopharynx
Vocal cords close
Epiglottis closes over larynx
Upper esophageal sphincter relaxes

7. Figure 24.10ab Deglutition (swallowing)

8. Physiology of the Esophagus - Deglutition
Figure 24.10
Physiology of the Esophagus - Deglutition
3. Esophageal stage
Bolus enters esophagus.
Upper sphincter relaxes when larynx is lifted
Peristalsis begins
Circular fibers contract behind bolus
Longitudinal fibers shorten the distance
Lower sphincter relaxes as food approaches
Travel time:
Solids: 4-8 seconds
Liquids: 1 second

9. Deglutition Summary Swallowed food Mouth Oropharynx Laryngopharynx
Upper esophageal sphincter
Esophagus
Peristalsis
Lower esophageal sphincter
Stomach

11. STOMACH

12. Stomach J shaped enlargement of GI tract
Figure 24.11a
Stomach
J shaped enlargement of GI tract
Mixing chamber and holding reservoir
Some absorption
Does very little “digestion”
Starts digestion of proteins
Continues lipid and starch digestion
Semisolid bolus converted to chyme
Size of your fist. Expands.
2 curves

13. Stomach Four Main Regions: Cardia Fundus Body Pyloris Three regions:
Figure 24.11b
Stomach
Four Main Regions:
Cardia
Fundus
Body
Pyloris
Three regions:
Pyloric antrum
Pyloric canal
Pylorus
Communicates with duodenum via pyloric sphincter
Rugae – folds in mucosa when stomach empty

14. Histology of the Stomach
Figure 24.12a
Histology of the Stomach
Same layers as rest of GI with some modifications:
Surface of mucosa – simple columnar cells called surface mucous cells

15. Histology of the Stomach
Figure 24.12b
Histology of the Stomach
Epithelial cells extend into the lamina propria forming gastric pits and 3 types of exocrine gastric glands.
Mucous neck cells
Zymogenic (chief) cells
Parietal (oxyntic) cells

16. Histology of the Stomach
Figure 24.12b
Histology of the Stomach
Gastric glands also contain entero-endocrine cells (G cells)
Gastrin
Stimulate gastric activity

17. Figure 24.12c Histology of the stomach

18. Histology of the Stomach
Figure 24.12a
Histology of the Stomach
Muscularis has 3 layers of smooth muscle instead of 2
longitudinal, circular, and an inner oblique layer.

19. Histology of the Stomach
The serosa is a part of the visceral peritoneum.
At lesser curvature, visceral peritoneum = lesser omentum.
At greater curvature, visceral peritoneum = greater omentum.

20. Digestion in the Stomach
Mechanical
Chemical
Peristalsis
Propulsion
Retropulsion
Gastric emptying*
2-6 hours after ingestion
1st carbs, 2nd protein, last fats
Salivary amylase
Lingual lipase
Parietal cells – HCl
H+ Cl-
Proton pumps
Carbonic anhydrase
Antiporters
HCO3-
Pepsinogen  pepsin
Gastric lipase

21. Figure 24.13 Secretion of HCl (hydrochloric acid) by parietal cells in the stomach

22. Protection of the Stomach
Figure 24.12b
Protection of the Stomach
Zymogenic cells
Pepsinogen  pepsin
pH of 2 activates
Prevents digestion of protein in organ
Protection
Surface and neck cells
1-3 mm alkaline mucous
Limited absorption
Certain drugs (aspirin, alcohol), electrolytes, some water

25. PANCREAS

26. Pancreas Retroperitoneal gland Head, body and tail
Figure 24.14a
Pancreas
Retroperitoneal gland
Head, body and tail
Connects to duodenum via 2 ducts
Secretes pancreatic juices
Hepatopancreatic ampulla

27. Figures 24.14b and c

28. Histology of the Pancreas
Small clusters of glandular epithelial cells
Exocrine  Acini – 99% of clusters
Secrete pancreatic juice
Endocrine  Pancreatic islets – 1% of clusters
Secrete hormones

29. Pancreatic Juice
Clear liquid: Water, salt, sodium bicarbonate, and enzymes
Starch – pancreatic amylase
Proteins – trypsin, chymotrypsin, carboxypeptidase
Fats – pancreatic lipase
Nucleic acids – ribonuclease, deoxyribonuclease
Sodium bicarbonate – brings pH to
Inactivates pepsin
Stimulates pancreatic enzymes

30. LIVER AND GALLBLADDER

31. Liver Right and left lobes Falciform ligament 2nd largest organ
Figure 24.15a
Liver
Right and left lobes
Falciform ligament
Quadrate and caudate lobes
Lobules
2nd largest organ
Heaviest gland

32. Histology of the Liver Lobules Contain: Hepatocytes Bile canaliculi
Sinusoids
Stellate reticuloendothelial cells
Central vein

33. Histology of the Liver Lobules Contain: Hepatocytes (80%)
Major functional cells of the liver
Bile canaliculi
Small ducts between hepatocytes
Collect bile produced by the hepatocytes
Bile pathway*
Sinusoids
Permeable blood capillaries between rows of hepatocytes

34. Figure 24.16 From GI organs and spleen
Vitamins, nutrients, drugs, toxins, microbes
Liver Lobules
Double supply of blood
All leaves through hepatic vein

35. Histology of the Liver Lobules Contain:
Figure 24.16b
Histology of the Liver
Lobules Contain:
4. Stellate reticuloendothelial cells
Fixed phagocytes in hepatocytes
Hepatic macrophages
5. Central vein

36. Figure 24.16d Histology of a lobule, the functional unit of the liver

37. Three models – pg. 911 Hepatic Lobule – functional unit
Portal Lobule – exocrine (bile) function
Hepatic Acinus – more recently preferred functional unit

38. Bile Gallbladder Sac located beneath liver
Figure 24.15
Gallbladder
Bile
Sac located beneath liver
Fundus, body and neck
Mucosa - simple columnar arranged in rugae
No submucosa
Muscularis ejects bile into cystic duct
Serosa - visceral peritoneum
Store and concentrate bile
Water, bile salts, cholesterol, lecithin, ions, bile pigments
Excretory product (worn out RBCs)  bilirubin
Emulsification of triglycerides.

39. Bile pathway: produced by hepatocytes  bile canaliculi 
bile ductules 
bile ducts 
R and L hepatic ducts 
common hepatic duct 
cystic duct (storage) 
common bile duct 
hepatopancreatic ampulla 
duodenum to aid digestion

40. Assignment for the weekend
Read through all the notes we have currently done. Come to class Monday with any questions or required clarification.
Read through pages of notes on Digestion and Absorption in the small intestine
Look at pages in textbook
Focus on understanding diagram on page 921