B6.2 and B6.3 : Alimentary Canal

Question 1

Alimentary Canal

Answer 1

the whole passage along which food passes through the body from mouth to anus

Question 2

Parts/Organs part of the alimentary canal

Answer 2

1. Mouth
2. Oesophagus
3. Stomach
4. Liver
5. Gall Bladder
6. Pancreas
7. Small Intestine
8. Large Intestine
9. Rectum/Anus

Question 3

Mouth

Answer 3

1. Mechanical digestion in the teeth which is when the teeth break down food into smaller particles to increase surface area to maximum digestion. More enzyme contact
2. Salivary amylase breaks does starch into glucose
3. Salivary glands secrete salivary amylase
4. There are 3 salivary glands
5. Food is rolled into a bolus which is a ball of food and saliva. The bolus then moves down the oesophagus and into the stomach
6. Ingestion takes place which is when food is taken in

Question 4

Oesophagus

Answer 4

1. 4 different layers - mucosa, submucosa, muscularis→ achieves swallowing, and adventitia
2. Peristalsis - a muscle like contraction that pushes food into other parts of the digestive tract
3. Bolus of food is swallowed and moved into the oesophagus
4. No digestion occurs - just moves food from one part to another

Question 5

Stomach

Answer 5

1. Gastric juice - produced by mucus cells in the lining of the stomach (gastric juice can be pepsin and HCL, it can also be located in the lining and protects the stomach from burning it).
2. Hydrochloric acid - activates enzyme pepsin (breaks down protein), decreases acidic level. Hydrochloric acid also kills bacteria and denatures bacterial enzymes
3. Digestive enzymes - gastric lipids
4. pH is 1.5 - 3.5 so it is acidic
5. Bolus turns into chyme (leaves the stomach into the small intestine - liquid with small chunks of solid (lipids still in the polymer form, carbs and protein started digestion)
6. Start of protein digestion
7. Rugae - wave like structure in the lining of the stomach which churns the food (mechanical digestion) to mix it with pepsin and HCL
8. Stops the digestion of starch from salivary amylase as the enzyme will denature

Question 6

Liver

Answer 6

1. Secretes bile which emulsifies fat (physically breaks it down into smaller fat molecules to increase surface area)
2. Bile is held in the gallbladder and when it is needed it is transferred to the small intestine
3. Emulsification of fat is both mechanical and chemical digestion
4. Bile is a complex fluid which contains water electrolytes, bile acid bilirubin, e.t.c
5. Bile gets rid of waste products such as cholesterol and haemoglobin
6. Bile absorbs fat and fat-soluble vitamins
7. Also filters blood (not in digestion)
8. There is a duct that leads into the small intestine that connects the liver/gallbladder and the pancreas
9. Accessory organs to the alimentary canal (food does not pass through it)

Question 7

Pancreas

Answer 7

1. Secretes pancreatic lipase, protease and amylase which is transferred to the small intestine for digestion
2. Produces bicarbonate which neutralizes the HCL from the stomach
3. pH of substances created by the pancreas are alkaline as it activates the enzymes and neutralizes the HCL from the stomach
4. There is a duct that leads into the small intestine that connects the liver/gallbladder and the pancreas
5. Accessory organs to the alimentary canal (food does not pass through it)

Question 8

Small Intestine

Answer 8

1. Digestion and absorption of nutrients of minerals.
2. Secretes protease, lipase, and amylase from the inner lining
3. Receives pancreatic amylase, lipase and protease which breaks down carbohydrates
4. Receives bile from the gallbladder which emulsifies fat (makes it smaller for surface area) fat
5. 90% of digestion occurs in the small intestine
6. The only mechanical digestion that takes place is from bile, the rest of the digestion is chemical digestion
7. Mixes chyme with digestive juices for digestion
8. Has a lumen which is the inner space of the small intestine - lined with epithelial cells which make up villi - inside the villi is capillaries and lacteal - carbs and protein enter the capillaries and fatty acids and glycerol enter the lacteal through diffusion (lumen to increase surface area)
9. Finishes all digestion and all nutrients are broken down
10. Most of the digestion begins in the duodenum which is in the beginning of the small intestine while most of the absorption happens in the ileum
11. Absorption is when the nutrients are absorbed into the bloodstream to be transported to other organs/parts of the body

Question 9

Large Intestine

Answer 9

1. Absorption of water
2. Also absorbs minerals and electrolytes
3. Has 3 units (parts of the large intestine - all connected) - ascending, transverse, and descending
4. Also has an appendix - no function
5. Fibre can be fermented - bacteria helps with the processing of fibre
6. The fibre that has a lot of cellulose is necessary because it scratches the walls of the large intestine to push and move food, feaces, and other substances pass
   E.coli which is a bacteria (good bacteria which we are not bothered by it) living in the guts helps to digest/access vitamin K

Question 10

Rectum

Answer 10

1. Where excretion takes place
2. The large intestine absorbs water so food turns into stool/feces and is moved into the rectum through peristalsis (muscle contraction in a certain direction)
3. Storage unit for feces
4. Sends signals to the brain saying that stool and feces needs to be released
5. When holding it in, signal will be sent to your brain to temporarily stop the feeling of needing to release feces and stool

Question 11

Why fat digestion does not occur in the stomach

Answer 11

1. Lipase does not work in acidic conditions (low pH)
2. The lipase will become denatured where the shape of the active site changes so the substrate (fat molecules) no longer can fit or bind with the enzyme