1. 3/28/08 Movement of Bolus  Forward movement ♦Waves of contraction in muscularis externa ♦Along length of tube ♦Process of peristalsis ♦Circular muscles contract behind bolus ♦Longitudinal muscles contract at cardiac sphincter ♦Wave of relaxation opens entrance to stomach  Side to side movement ♦No set direction ♦Helps to mix bolus with mucus for more lubrication ♦Contraction in muscles → segmentation ♦Mostly in large & small intestine – helps to fragment bolus

2. 3/28/08 Digestive System Chapter 22 – Day 3

3. 3/28/08 Stomach Anatomy  Shape  Sphincters ♦Cardiac ♦Pyloric  Folds = rugae ♦Deep muscular folds  Mucosa Fig. 22.12

4. 3/28/08 Stomach Anatomy  Mucosa ♦Gastric pits with gastric glands ♦Secretory cells  4 types of secretory cells: CellSecretion  Chief cells→ Pepsinogen  Parietal cells →HCl (acid)  Mucus cells →Mucus  Enteroendocrine cells →Gastrin (hormone)

5. 3/28/08 Stomach Processes  What happens to food when it enters the stomach?  Digestion & Secretion – almost no absorption  3 phases of secretion in the stomach (FIGURE 22.15) – KNOW IT!!!! 1.Cephalic ♦Begins at the sight of food ♦Gastrin is secreted ♦Stimulates HCl & pepsinogen  Food enters the stomach

6. 3/28/08 Phases of Gastric Secretion in Stomach 2.Gastric Phase Secretion  Mucus is secreted to protect stomach lining  More gastrin, more pepsinogen  Acidic environment – pH drops (pepsinogen → pepsin at low pH)  Secretions stop when pH reaches 2.0 Digestion  Proteins in food →pepsin →amino acids  Milk proteins →gastric lipase → amino acids & renin

7. 3/28/08 Phases of Gastric Secretion in Stomach 2.Gastric Phase Mixing  Rugae become stretched – stomach is distended  Muscular contractions mix food for several hours  Food becomes watery mixture ♦Chyme (acidic)  After several hours of mixing waves of contractions (peristalsis) reach the lower end/base of the stomach – near the pyloric sphincter  Sphincter opens & closes with each wave  Squirts chyme into the duodenum  The Duodenum secretes enteric gastrin ♦starts next phase

8. 3/28/08 Phases of Gastric Secretion in Stomach 2.Gastric Phase General info/reminders  After 2-6 hours, the stomach is emptied  Some macromolecules move faster through the stomach: ♦Carbohydrates ♦Proteins ♦Then fats  Remember NO absorption in the stomach except for EtOH, H2O, aspirin (alcohol is absorbed fast – gets to brain fast)  On to next phase = intestinal phase

9. 3/28/08 Phases of Gastric Secretion in Stomach 3.Intestinal Phase Food moves to intestine = gastric emptying  Small intestine secretes 2 hormones:  Cholecystokinin (CCK) ♦Is released when proteins & fat are in the chyme ♦Inhibits gastric secretions ♦Triggers pancreas secretion  Secretin ♦Released when pH in duodenum drops below 4.5 ♦Stimulates bicarbonate release from pancreas Deactivates pepsin Inhibits stomach secretions Stimulates bile secretion from liver

10. 3/28/08 Accessory Structures  Digestion in small intestine depends on secretions from pancreas & liver - Take a closer look at these accessory structures  Pancreas ♦Elongated organ posterior to stomach ♦Contains pancreatic islets & acini ♦Acini – very important for digestive system Secretes pancreatic juice when cholecystokinin is secreted in duodenum ♦Pancreatic Juice Contains: water, bicarbonate ions It alters the pH of the chyme to 7.1-8.2

11. 3/28/08 Accessory Structures: Pancreas  Enzymes produced by Pancreas = 6 ♦Pancreatic α-amylase Carbohydrate digestion ♦Pacreatic lipase Fat digestion ♦Nucleases Nucleic acid digestion ♦Trypsin ♦Chymotrypsin ♦Carboxypeptidase  These enzymes are secreted by the acinar cells ♦Are carried to the duodenum in 2 major ducts proteins

12. 3/28/08 Accessory Structures: Pancreas Fig. 22.18

13. 3/28/08 Accessory Structures: Pancreas  These enzymes are secreted by the acinar cells ♦Are carried to the duodenum in 2 major ducts  Pancreatic Duct/Duct of Wirsung ♦Joins the common bile duct to enter the duodenum At the hepatic pancreatic ampulla  Accessory Duct/Duct of Santorini ♦Enters the duodenum above the ampulla

14. 3/28/08 Accessory Structures: Liver  Important synthesis and recycling center in the body  Nutrients are absorbed and go to the liver first  External anatomy: ♦Left & Right Lobes Held together by Falciform ligament ♦Posterior surface of the liver - 2 other lobes Caudate – near superior vena cava Quadrate – near gall bladder  Important vessels ♦Hepatic vein & Hepatic portal vein Drain blood into vena cava ♦Hepatic Artery Brings blood in ♦Common bile duct Brings bile out of liver Fig. 22.19

15. 3/28/08 Accessory Structures: Liver  Internal anatomy – histology  Network of vessels among cells – see Fig. 22.20  Cells: ♦Hepatocytes Square cells/plates of cells Vein branches run between cells = sinusoids Lead to a central vein – to the hepatic vein ♦Sinusoid walls are lined with epithelium ♦Contain phagocytes = Kupffer Cells Break down old RBCs, WBCs, toxins, & bacteria  Liver recycles, but also produces & secretes: ♦Hepatocytes – secrete total of approx. 1 L of bile every day ♦Bile enters bile caniculli also dispersed among hepatocytes

16. 3/28/08 Accessory Structures: Liver - Gallbladder Fig. 22.20

17. 3/28/08 Accessory Structures: Liver - Gallbladder  Bile canaliculi merge with hepatic ducts – bile is taken to the gall bladder for storage  At release bile leaves via the cystic duct  This merges with the common hepatic duct to form the common bile duct which goes to the duodenum ♦The liver also releases bilirubin into the duodenum for waste excretion ♦Stimulated by the vagus nerve & secretin stimulation  In the gall bladder ♦Bile is concentrated, water is absorbed ♦The common bile duct enters the duodenum at the same entrance as the pancreatic duct

18. 3/28/08 Accessory Structures: Liver - Gallbladder  Release is controlled by the hepatopancreatic sphincter  Contraction of sphincter is stimulated by CCK  Secretin increases the rate of production  In the intestines – bile breaks down fats = emulsification

19. 3/28/08 Small Intestine  Long tube = 20 feet in length  Divided into 3 regions ♦Duodenum Shortest region – follows stomach Approx. 10 inches long ♦Jejunum 8 feet ♦Ileum 12 feet  Activities in the small intestine: ♦Secretion & Absorption

20. 3/28/08 Small Intestine – Secretions Summary  Hormones in duodenum ♦Cholecystokinin ♦Secretin  Pancreatic juice ♦α – amylase ♦Nucleases ♦Lipase ♦Trypsin ♦Chymotrypsin ♦Carboxypeptidase ♦Bicarbonate ions  Liver secretions ♦Bile

21. 3/28/08 Small Intestine – Anatomy  Within the tube = 4 layers  Mucosa ♦Contains waves of ridges Plicae – these are like rugae, but they don’t stretch ♦Contains small projections Villi – these are absorptive cells  Within each villus – single layer epithelial tissue ♦There are hair like extensions on the cell – “brush border” ♦Below the epithelium = capillaries for absorption There is also a lymph vessel = lacteal Other larger molecules are not transferred through the blood Will enter the lacteal ♦Goblet cells Produce alkaline mucus Neutralize pH, thus protecting the intestine from acid  Submucosa – below villi ♦Contains “Peyer’s patches” = lymph nodules – these help in fat absorption

22. 3/28/08 Small Intestine – Digestion  Duodenum ♦Main job = secretion  Summary of secretions: ♦Maltase, sucrase, & lactase  All 4 types of macromolecules can be digested in the S.I.  Chyme is mixed with secretions – needs segmentation & peristalsis  There are parasympathetic controls

23. 3/28/08 Small Intestine – Digestion Digestion of Macromolecules  Carbohydrates: ♦Starch → maltose: needs amylase ♦Maltose → glucose: needs maltase ♦Sucrose → glucose + fructose: needs sucrase ♦Lactose → glucose + galactase: needs lactase these smaller molecules can be absorbed into the bloodstream  Proteins ♦Only certain ones are digested in stomach, the remainder are digested in the S.I. ♦Trypsin, Chymotrypsin: proteins → peptides (small chains) ♦Carboxypeptidase: peptides → amino acids

24. 3/28/08 Small Intestine – Digestion Digestion of Macromolecules  Lipids (Fats): ♦Fats are broken up into smaller globules ♦Emulsification requires bile ♦Fats → Fatty Acids (monoglycerides): needs lipase  Nucleic Acids ♦DNA (or RNA) → pentose sugars + nitrogen compounds: needs nuclease (then they are absorbed)  Small compounds are then ready for absorption ♦90% of absorption in S.I. via villi  HOW ARE THEY ABSORBED??

25. 3/28/08 Small Intestine – Digestion  Duodenum ♦Main job = secretion  Summary of secretions: ♦Maltase, sucrase, & lactase  All 4 types of macromolecules can be digested in the S.I.  Chyme is mixed with secretions – needs segmentation & peristalsis  There are parasympathetic controls

26. 3/28/08 Swallowing Fig. 22.11

27. 3/28/08 Alvioli – Capillary Interface Fig. 22.4

28. 3/28/08 ld

29. 3/28/08 Mechanics of Respiration  Ventilation ♦= mechanical process ♦involves the diaphragm and skeletal muscles (intercostal muscles)  Breathing consists of 2 phases: ♦Inspiration air is taken into the lungs ♦Expiration Air passes out of the lungs

30. 3/28/08 Alvioli – Capillary Interface Fig. 21.11