The Digestive System: Crashcourse

Question 1

Why is surface area important in digestion?

Answer 1

• Humans have acids and enzymes in digestive tracts that break down food so it can be absorbed and used.
• Chewing breaks food down (increase surface area)
• Enzymes in saliva (salivary amylase) start braking foods down further until nutrients can be absorbed
• Absorption happens in the small intestine- have villi and more micro villi (increase surface area)

Question 2

How does food move from the mouth to the oesophagus?

Answer 2

• Peristalsis- wave like contractions of the oesophagus (how most movement occurs in the digestive system)
  Food passes down the pharynx and down the oesophagus
• Salivary Amylase breaks down starch into glucose
• Food becomes bolus

Question 3

How does the stomach help with digestion?

Answer 3

• Stomach churns and mixes bolus together with enzymes/ acids called gastric juice
• Hydrochloric acid pH 1 (very acidic)- breaks food down and kills bacteria
• Pepsin- breaks down protein into amino acids
• Mucus- protects the stomach. Not enough mucus could lead to peptic ulcers (when acids comes in contact with stomach)
• When food leaves the stomach it becomes chyme
• Diarrhea- body does not absorb nutrients just excretes chyme
• There are valve sphincters between stomach and small intestine that regulates how much chyme gets into the small intestine

Question 4

What is gastric juice made up of?

Answer 4

• Hydrochloric acid
• Mucus
• Pepsin
• Water

Question 5

How does the small intestine help with digestion?

Answer 5

• Beginning of the small intestine is called the duodenum
• Things are absorbed and secreted into the duodenum
• Bicarbonate which neutralises gastric acid before it can go any further
• SI- where cellular exchange of nutrients and the breakdown of fats occurs
• Lined with epithelial tissue (has many ridges and folds)
• Villi- has capillaries in it so it can absorb nutrients. Villi covered in microvilli
• Small intestine and gall bladder help break down fats

Question 6

How does bile help break down fats?

Answer 6

• Near the top of the small intestine is the bile duct.
• Bile- made by liver, store by the gall bladder are squirted into the small intestine
• Bile is an emulsifier- takes hydrophobic fat molecules and breaks them up into fatty acids and monoglycerides (can be absorbed by epithelial tissue

Question 7

How does the large intestine help with digestion?

Answer 7

• Food goes through another sphincter and enters the cecum (the beginning of the large intestine)
• Removes most of the water and bile salts from the chyme (prevents diarrhea)
• Food passes through anal sphincters and is excreted

Question 8

What is the appendix used for?

Answer 8

• Acts as a safe house for all good bacteria needed for food digestion.
• Helps body recolonise after illness