Topic 6.1: Digestion and Absorption

Question 1

What are two major groups of organs which comprise the human digestive system?

Answer 1

alimetary canal and accessory organs

Question 2

Define alimentary canal

Answer 2

The alimentary canal consists of organs through which food actually passes (oesophagus, stomach, small & large intestine)

Question 3

Define accessory organs

Answer 3

The accessory organs aid in digestion but do not actually transfer food (salivary glands, pancreas, liver, gall bladder)

Question 4

Is the esophagus part of the alimetary canal or accessory organs?

Answer 4

alimetary canal

Question 5

Is the stomach part of the alimetary canal or accessory organs?

Answer 5

alimetary canal

Question 6

Is the small intestine part of the alimetary canal or accessory organs?

Answer 6

alimetary canal

Question 7

Is the salivary glands part of the alimetary canal or accessory organs?

Answer 7

accessory organs

Question 8

Is the pancreas part of the alimetary canal or accessory organs?

Answer 8

accessory organs

Question 9

Is the liver part of the alimetary canal or accessory organs?

Answer 9

accessory organs

Question 10

Is the gall bladder part of the alimetary canal or accessory organs?

Answer 10

accessory organs

Question 11

Is the large intestine part of the alimetary canal or accessory organs?

Answer 11

alimetary canal

Question 12

What is the structure and function of the oesophagus?

Answer 12

A hollow tube connecting the oral cavity to the stomach (separated from the trachea by the epiglottis)

• Food is mixed with saliva and then is moved in a bolus via the action of peristalsis

Question 13

What is the structure and function of the stomach?

Answer 13

A temporary storage tank where food is mixed by churning and protein digestion begins

• It is lined by gastric pits that release digestive juices, which create an acidic environment (pH ~2)

Question 14

What is the structure and function of the small intestine?

Answer 14

A long, highly folded tube where usable food substances (nutrients) are absorbed

• Consists of three sections – the duodenum, jejunum and ileum

Question 15

What is the structure and function of the large intestine?

Answer 15

The final section of the alimentary canal, where water and dissolved minerals (i.e. ions) are absorbed

• Consists of the ascending / transverse / descending / sigmoidal colon, as well as the rectum

Question 16

What is the structure and function of the salivary glands?

Answer 16

Release saliva to moisten food and contains enzymes (e.g. amylase) to initiate starch breakdown

• Salivary glands include the parotid gland, submandibular gland and sublingual gland

Question 17

What is the structure and function of the pancreas?

Answer 17

Produces a broad spectrum of enzymes that are released into the small intestine via the duodenum

• Also secretes certain hormones (insulin, glucagon), which regulate blood sugar concentrations

Question 18

What is the structure and function of the liver?

Answer 18

Takes the raw materials absorbed by the small intestine and uses them to make key chemicals

• Its role includes detoxification, storage, metabolism, bile production and haemoglobin breakdown

Question 19

What is the structure and function of the gall bladder?

Answer 19

The gall bladder stores the bile produced by the liver (bile salts are used to emulsify fats)

• Bile stored in the gall bladder is released into the small intestine via the common bile duct

Question 20

What is the first step of mechanical digestion?

Answer 20

Food is initially broken down in the mouth by the grinding action of teeth (chewing or mastication)

Question 21

After Food is initially broken down in the mouth by the grinding action of teeth (chewing or mastication), what is the next step of mechanical digestion?

Answer 21

The tongue pushes the food towards the back of the throat, where it travels down the esophagus as a bolus

Question 22

After The tongue pushes the food towards the back of the throat, where it travels down the esophagus as a bolus, what is the next step of mechanical digestion?

Answer 22

The epiglottis prevents the bolus from entering the trachea, while the uvula prevents the bolus from entering the nasal cavity

Question 23

After The epiglottis prevents the bolus from entering the trachea, while the uvula prevents the bolus from entering the nasal cavity, what is the next step of mechanical digestion?

Answer 23

The stomach lining contains muscles which physically squeeze and mix the food with strong digestive juices (‘churning’)

Question 24

After The stomach lining contains muscles which physically squeeze and mix the food with strong digestive juices (‘churning’), what is the next step of mechanical digestion?

Answer 24

Food is digested within the stomach for several hours and is turned into a creamy paste called chyme

Question 25

After Food is digested within the stomach for several hours and is turned into a creamy paste called chyme, what is the next step of mechanical digestion?

Answer 25

Eventually the chyme enters the small intestine (duodenum) where absorption will occur

Question 26

After Eventually the chyme enters the small intestine (duodenum) where absorption will occur, what is the last step of mechanical digestion?

Answer 26

Segmentation contractions move chyme in both directions, allowing for a greater mixing of food with digestive juices

Question 27

What is segmentation (digestion)?

Answer 27

Segmentation involves the contraction and relaxation of non-adjacent segments of circular smooth muscle in the intestines

Question 28

What is the first step of chemical digestion?

Answer 28

The stomach contains gastric glands which release digestive acids to create a low pH environment (pH ~2)

Question 29

After The stomach contains gastric glands which release digestive acids to create a low pH environment (pH ~2), what is the next step of chemical digestion?

Answer 29

The acidic environment functions to denature proteins and other macromolecules, aiding in their overall digestion

Question 30

After The acidic environment functions to denature proteins and other macromolecules, aiding in their overall digestion, what is the next step of chemical digestion?

Answer 30

The stomach epithelium contains a mucous membrane which prevents the acids from damaging the gastric lining

Question 31

After The stomach epithelium contains a mucous membrane which prevents the acids from damaging the gastric lining, what is the next step of chemical digestion?

Answer 31

The pancreas releases alkaline compounds (e.g. bicarbonate ions), which neutralise the acids as they enter the intestine

Question 32

After The pancreas releases alkaline compounds (e.g. bicarbonate ions), which neutralise the acids as they enter the intestine , what is the next step of chemical digestion?

Answer 32

The liver produces a fluid called bile which is stored and concentrated within the gall bladder prior to release into the intestine

Question 33

After The liver produces a fluid called bile which is stored and concentrated within the gall bladder prior to release into the intestine, what is the next step of chemical digestion?

Answer 33

Bile contains bile salts which interact with fat globules and divide them into smaller droplets (emulsification)

Question 34

After Bile contains bile salts which interact with fat globules and divide them into smaller droplets (emulsification), what is the next step of chemical digestion?

Answer 34

The emulsification of fats increases the total surface area available for enzyme activity (lipase)

Question 35

After The emulsification of fats increases the total surface area available for enzyme activity (lipase), what is the last step of chemical digestion?

Answer 35

Enzymes are biological catalysts which speed up the rate of a chemical reaction (i.e. digestion) by lowering activation energy Enzymes allow digestive processes to therefore occur at body temperatures and at sufficient speeds for survival requirements Enzymes are specific for a substrate and so can allow digestion of certain molecules to occur independently in distinct locations

Question 36

What are the four main tissue layers of the small intestine from outside to center?

Answer 36

serosa, muscle layer, submucosa, mucosa

Question 37

Define serosa (small intestine)

Answer 37

Serosa – a protective outer covering composed of a layer of cells reinforced by fibrous connective tissue

Question 38

Define muscle layer (small intestine)

Answer 38

Muscle layer – outer layer of longitudinal muscle (peristalsis) and inner layer of circular muscle (segmentation)

Question 39

Define submucosa (small intestine)

Answer 39

Submucosa – composed of connective tissue separating the muscle layer from the innermost mucosa

Question 40

Define mucosa (small intestine)

Answer 40

Mucosa – a highly folded inner layer which absorbs material through its surface epithelium from the intestinal lumen

Question 41

What is the function of villi in the small intestine?

Answer 41

Villi increase the surface area of epithelium over which absorption is carried out • Villi absorb monomers formed by digestion as well as mineral ions and vitamins