Structure and Function of the digestive system

Question 1

What are the 6 functions of the digestive system?

Answer 1

1. Ingestion
2. Secretion
3. Mixing and propulsion
4. Digestion
5. Absorption
6. Defecation

Question 2

Layers of the GI track

Answer 2

Mucosa
Epithelium, Lamina propria, Muscularis mucosae

Submucosa
Submucosa plexus which is part of the enteric nervous system (ENS)

Muscularis
Myenetric plexus which is the 2nd plexus of the ENS or visceral peritoneum

Serosa

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Question 3

What are the three Major Salivary glands?

Answer 3

◦ Parotid glands
◦ Submandibular glands
◦ Sublingual ducts

Question 4

What’s the function of Saliva?

Answer 4

Saliva is secreted to keep the mucous membranes of the mouth and pharynx moist and to cleanse the mouth and teeth, itincreases to lubricate, dissolve and start mechanical breakdown of food

Question 5

What are the 3 enzymes in saliva?

Answer 5

• Lysozyme
• Salivary amylase (becomes inactivated by stomach acid)
• Lingual lipase (activated in the stomach)

Question 6

What does bolus mean ?

Answer 6

The mastication the food into a soft, flexible, easily swallowed mass

Question 7

The role of the Pharynx and Oesophagus

Answer 7

When food is swallowed it first passes through the pharynx which is composed of skeletal muscle.

Muscular contractions help propel food into the oesophagus.

The oesophagus is in the posterior to the trachea and the entrance of food to the oesophagus is regulated by the upper oesophageal sphincter during swallowing and allows food to pass into the stomach.

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Question 8

Functions of the stomach

Answer 8

• Mixes saliva, food and gastric juice to form chyme.
• Holds food before release into the small intestine.
• Secretes gastric juice (containing HCl), pepsin, intrinsic factor and gastric lipase.
• HCl kills bacteria and denatures proteins.
• Pepsin begins the digestion of proteins.
• Intrinsic factor aids absorption of vit B12.
• Gastric Lipase aids digestion of Tcls.
• Secretes gastrin into blood.

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Question 9

Mechanical process of the stomach

Answer 9

After food enters the stomach, gentle, rippling peristaltic movements called mixing waves pass over the stomach for 15-20 seconds.

These waves assist in producing chyme (juice)

As digestion proceeds more vigorous mixing waves begin at the body of the stomach and intensify as they reach the pylorus.

The pyloric sphincter remains almost closed, but not fully: as food reaches the pylorus some of the chyme is forced into the duodenum due the mixing waves, however most of the chyme is forced back into the body of the stomach where mixing continues.

Food may remain in the fundus for about an hour without becoming mixed with gastric juice. During this time digestion by salivary amylase continues.

Question 10

Regulation of gastric secretion, motility and emptying

Answer 10

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Question 11

How much pancreatic juice is produced in the pancrease?

Answer 11

1.2-1.5 litre

Question 12

What are the 9 functions of the liver?

Answer 12

1. Carbohydrate metabolism
2. Lipid metabolism
3. Protein metabolism
4. Processing of drugs and hormones
5. Excretion of bilirubin
6. Synthesis of bile salts
7. Storage
8. Phagocytosis
9. Activation of Vitamin D

Question 13

what is The major site of digestion and absorption?

Answer 13

Small intestine

Question 14

How long in length and diameter is the small intestine?

Answer 14

About 1.5 m long and 6.5 cm in diameter

Question 15

What are the regions in the small intestine?

Answer 15

Cecum, colon, rectum, and anal canal

Question 16

What is Haustral churning?

Answer 16

hen the distension reaches a certain point, the walls contract and squeeze the content into the next haustrum.