Alimentary canal

Question 1

Ingestion

Answer 1

taking food and drink into the body (through the mouth in humans)

Question 2

Digestion

Answer 2

breaking down of large food molecules into smaller water-soluble molecules

Question 3

Absorption

Answer 3

Movement of digested food molecules from the wall of the intestine into the blood and lymph.

Question 4

Egestion

Answer 4

Removal of substances through the anus that were ingested but not absorbed by the body (faeces)

Question 5

Assimilation

Answer 5

the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells.

Question 6

Mechanical vs Chemical digestion

Answer 6

Mechanical: occurs mainly in the mouth, where food is broken down physically into smaller pieces by bitting and chewing action of the teeth.

It also happens in the small intestine, where bile helps to emulsify fats, which means breaking them down into smaller droplets.

Chemical: the breakdown of large food molecules into smaller ones using chemicals such as enzymes. SOME molecules are already small enough to pass through the alimentary canal wall and do not need to be digested.

Question 7

What is the alimentary canal?

Answer 7

A continuous tube through the body, from the mouth through the oesophagus, stomach, small intestine, and large intestine to the anus where faeces are egested.

Question 8

Main regions of the alimentary canal

Answer 8

• Mouth, salivary glands
• Oesophagus
• Stomach
• Pancreas
• liver
• gall bladder
• Small intestine (duodenum + ileum)
• Large intestine (colon +rectum)
• Anus.

Question 9

Mouth

Answer 9

Where food is mechanically digested by the cutting and movement from the teeth and tounges

Question 10

Salivary glands

Answer 10

Saliva is added—containing amylase (to begin digestion of starch)

Question 11

Oesophagus

Answer 11

Where each lump of swallowed food (bolus) is moved from the mouth to the stomach by waves of muscle contraction called peristalsis

Question 12

Stomach

Answer 12

Pepsin breaks down protein into amino acids

• Hydrochloric acid kills bacteria

Question 13

Liver

Answer 13

• Cells in the liver secret bile
• amino acids not used for making proteins are broken down to form urea (which passes to the kidneys for excretion)
• Excess glucose is removed from the blood and stored as glycogen in liver cells

Question 14

Gall bladder

Answer 14

stores bile from the liver

• bile is passed along the bile duct into the small intestine where it NEUTRALISES the stomach acid in chyme

Question 15

Pancreas

Answer 15

• Secrets digestive enzymes in an alkaline fluid into the dodenum

Question 16

Small intestine (duodenum and ileum)

Answer 16

• Secretions from the gall bladder and pancreas enter the first part of the small intestine (duodenum) to complete the process of digestion
• Emulsify large lipids
• Pancreatic juice in duodenum that contain amylase, trypsin and lipase
• Digested good molecules and water are absorbed in the ileum. Has a very large surface area due to vili and microvilli. Each villus contains many blood vessels and a lacteal

Question 17

Large intestine (colon)

Answer 17

Water is absorbed from the remaining material. Contains no digestive enzymes.

Question 18

Rectum

Answer 18

The remaining, unabsorbed, material (faeces), plus dead cells from the lining of the alimentary canal and bacteria are compacted and stored

Question 19

Anus

Answer 19

Faeces is egested through a sphincter