1. The Digestive System Functions
Biology 12

2. The Mouth
Mouth uses both mechanical (physical) and chemical digestion to start the process
Mastication – chewing by teeth
Salivary glands add water and salivary amylase to bolus of food
Salivary amylase starts digestion of starch
Uvula and soft palate help with swallowing and covers the nasal cavity so that fluids do not go wrong way

3. Salivary Glands Each gland comes in a pair
Parotid s.g. secretes the most salivary amylase to help carbohydrate digestion
Saliva is 99% water and 1% protein and salts
Saliva pH ~ 6.5
Acts as a solvent for food, and helps soften bolus for swallowing

4. Pharynx and Epiglottis
Epiglottis covers the trachea to prevent food from entering lungs
Pharynx part of BOTH digestive and respiratory systems

5. esophagus
Lining of the esophagus is stratified squamous epithelial tissue with additional smooth muscle layers
Peristalsis is muscle contractions that push food down towards stomach
Gastroesophageal Reflux Disease (GERD) when burning of esophageal tissues due to stomach acid
Average adult length 10 inches

6. Stomach When expanded can hold 1 litre of food or liquid 3 parts
Cardiac – contains mucous secreting cells (close to esophageal sphincter)
Fundus – top, contains gastric juices
Pyloric – secretes hormone Gastrin
Parietal cells make HCl (pH 2.5)
Chief cells secrete pepsinogen
Pepsinogen + HCl  Pepsin (active enzyme that breaks down protein)
Food called CHYME once gastric juices added to bolus

7. Stomach

8. Small Intestine 6 meters long and 1 inch in diameter
Duodenum – receives pancreatic juices, secrete maltase, sucrase, lactase, peptidases
Jejunum – where absorption of monomers take place. Large villi to increase surface area
Ileum – absorbs vitamin B’s and C

9. Villi
Villi are very important for increasing surface area of the small intestine
Lacteal help absorb dietary fats
Lacteal leads to lymph system for fat circulation
All other monomers go directly into blood stream

10. Liver B – produces bile B – breaks down red blood cells
B – produces blood proteins (A, B, Rh)
B – Blood detoxification
B – Blood sugar storage of glycogen
U – produced urea (from ammonia)

11. Gall Bladder Stores bile(which is made in the liver)
When given hormone signal, gall bladder will contract and squeeze out the bile through the cystic duct and common bile duct, into the duodenum
Can be removed without long term impact on health (may impact fat absorption)

12. Pancreas
Creates insulin and glucagon as part of the blood sugar homeostasis
Create pancreatic juices (SLTPNW)
Sodium bicarbonate (neutralize HCl)
Lipase (enzyme for lipids)
Trypsin (2nd enzyme for protein)
Pancreatic Amylase (2nd enzyme for starch)
Nucleases (Enzyme for nucleic acids)
Water
Released into the duodenum

13. Duct system of accessory organs
Hepatic duct takes bile from liver to gall bladder
Cystic duct takes bile from gall bladder to common bile duct which drains to duodenum
Pancreatic duct is from pancreas to common bile duct
Sphincter of Oddi controls the ducts emptying into duodenum

14. Large intestine 1.5 metres in length & 2.5 inches thick
Gut bacteria excrete vitamins B & K and it is absorbed in large intestine
Gut bacteria also produce methane gas
Reabsorbs water to body and helps to create a solid waste

15. Rectum and Anus
Rectum is a continuation of the large intestine and stored accumulating fecal matter until ready to remove
No villi, but many goblet cells to produce mucous to help lubricate and form stool
Anus is the opening that is controlled by the anal sphincter

16. What is acid reflux? HCl able to move through esophageal sphincter
HCl goes into esophagus and due to lack of mucus, can damage lining
Sphincter muscle relaxes at the wrong time
Treatment – something to neutralize acid

17. What are hemorrhoids?
Swollen veins around anus (similar to varicose veins)
Can result from increased pressure on vascular system or straining during bowel movement
Result in rectal bleeding
Soak to prevent infections and promote healing

18. What are intestinal polyps?
Most polyps are harmless, but some need to be treated to prevent irregular growth leading to cancerous growth
Fairly common in people over 60 years old (25% of population)

19. What is an ulcer?
In stomach (peptic ulcer) caused by H.pylori bacteria
Treat with antibiotics
In duodenum, caused by weakened pyloric sphincter

20. What is Cirrhosis? Liver develops polyps and damaged cells
Liver dysfunction results in yellowing of skin and whites of eyes.
Bilirubin accumulation causes yellowing
Byproduct of breakdown of red blood cells
Caused by alcoholism and hepatitis

21. Diabetes
Type 1 – pancreas Beta cells do not make insulin. Must inject insulin in order to allow glucose to be used in cell for ATP production and glycogen production
Type 2 – insulin insensitivity. Developed usually due to obesity (but not always). Does not allow insulin to work as gated receptor

22. Gall Stones
Gall stones can block the cystic duct and common bile duct and prevent bile and pancreatic juices from entering duodenum
Can be either cholesterol stones (yellow), build up of cholesterol, or pigment stones (black), build up of bilirubin from liver
Cause a great deal of pain