Digestive system

Question 1

What is the function of the digestive system?

Answer 1

Breaks down food into forms that can be absorbed and used by the body.

Also eliminates waste.

Question 2

What are the three organs involved in swallowing?

Answer 2

Pharynx, tongue and mouth

Question 3

What are the two basic digestive processes?

Answer 3

1. Mechanical - process of physically breaking down food e.g., chewing
2. Chemical - process of chemically splitting large molecules into smaller ones (uses enzymes, acids and bile)

Question 4

What are the two organ GROUPS in the digestive system?

Answer 4

1. Gastrointestinal (GI) tract - continuous tube extending from mouth to anus
2. Accessory digestive organs - organs that help or feed liquids into the GI tract e.g., pancreas, salivary glands, teeth

Question 5

What are the 4 major layers that make up the tissue throughout the GI tract and their general function?

Answer 5

1. MUSCOSA - the inner lining of the GI tract (includes muscularis mucosa which creates small folds to increase surface area for digestion and absorption)
2. SUBMUCOSA - consists of blood/lymphatic vessels, submucous plexus that innervates the mucosa, blood vessels and secretory cells)
3. MUSCULARIS - skeletal muscle, smooth muscle and myenteric plexus which innervates smooth muscle layers
4. SEROSA - serous membrane that secretes slippery fluid to allow the GI tract to sit in the correct orientation within the body (oesophagus lacks a serosa)

Question 6

What regulates the digestive system (x 3)?

Answer 6

1. Enteric nervous system (gut brain)
2. autonomic nervous system
3. gastrointestinal reflex pathways

Question 7

What is the largest serous membrane of the body and what are it’s two divisions?

Answer 7

The peritoneum

1. parietal peritoneum - lines walls of the abdominal cavity
2. visceral peritoneum - covers some of the organs and constitutes their serosa

Question 8

Why is the peritoneum important?

Answer 8

Supports the viscera and provides pathways for blood and lymphatic vessels.

Question 9

What are the peritoneal folds and their function?

Answer 9

Folds of the peritoneum that bind organs to each other and to the wall of the abdominal cavity. Contains blood vessels, lymphatic vessels and nerves.

Question 10

What are the five main peritoneal folds?

Answer 10

1. greater omentum
2. falciform ligament
3. lesser omentum
4. mesentery
5. mesocolon

Question 11

There are small and major salivary glands that secrete saliva into the oral cavity. What are the three major glands called?

Answer 11

1. Paratid (near ears)
2. Submandibular (mandible)
3. Sublingual glands (beneath tongue)

Question 12

What is saliva composed of and in what quantities?

Answer 12

99.5% water, 0.5% solutes

Solutes include:
- mucus
- bicarbonate and phosphate ions (buffer acidic foods)
- chloride ions (activate salivary amylase)
- salivary amylase (starts breakdown of starch)
- lysozyme (kills bacteria)
- immunoglobulin (IgA) (prevents attachment of microbes to the epithelium)

(pH is 6.35-6.85)

Question 13

What is the role of saliva?

Answer 13

• remove waste molecules
• protect mouth from infection w rinsing action
• keeps mucous membranes moist

Question 14

Which system controls salivation?

Answer 14

Autonomic nervous system

Question 15

What chemical digestion happens in the mouth?

Answer 15

• release of salivary amylase (starts the breakdown of starch) and lingual lipase (activated in the stomach)

Question 16

What are the 3 stages of swallowing (deglutition)?

Answer 16

1. voluntary stage - bolus forced into the pharynx by the tongue
2. pharyngeal (involuntary) - nasopharynx closed; epiglottis closed; upper oesophageal sphincter relaxes
3. oesophageal (involuntary) - enters oesophagus, peristalsis, lower oesophageal sphincter relaxes, glands secrete mucus to reduce friction

Question 17

Name the functions of the stomach.

Answer 17

• mixed saliva, food and gastric juices to form chyme
• reservoir for food before release into small intestine
• secretes gastric juices
• secretes gastrin into blood

Question 18

Functions of gastrin?

Answer 18

• stimulates parietal cells to secrete HCL
• stimulates chief cells to secrete pepsinogen
• contracts lower oesophageal sphincter
• increases motility of the stomach
• relaxes pyloric sphincter (connects stomach and small intestine)

Question 19

What cells are found in gastric pits (formed by mucosa)?

Answer 19

• surface mucous cells (secrete mucous)
• mucous neck cells (secrete mucous)
• parietal cells (secrete HCL and intrinsic factor)
• chief cells (secrete pepsinogen and gastric lipase)
• G cells (secrete gastrin)

Question 20

What are the six basic processes of digestion?

Answer 20

1. ingestion
2. secretion
3. mixing and propulsion
4. digestion (mechanical and chemical)
5. absorption
6. defecation

Question 21

The sensory neurons of the enteric nervous system receive stimulation from what?

Answer 21

1. chemoreceptors
2. mechanoreceptors (respond to stretching of wall og GI organs)

Question 22

What are the 4 major regions of the stomach?

Answer 22

1. cardia
2. fundus
3. body
4. pyloric antrum

Question 23

What substance in the stomach activates pepsinogen into pepsin, denatures proteins and kills bacteria?

Answer 23

HCL

Question 24

Which cells allow an alkaline protective barrier to form on the inner stomach lining to prevent acid erosion?

Answer 24

Mucous cells

Question 25

What are the two major ducts of the pancreas that convey secretions into the small intestine?

Answer 25

- pancreatic ducts (duct of Wirsung) - accessory duct (duct of Santorini)

Question 26

Why is pancreatic juice slightly alkaline?

Answer 26

To stop stomach pepsin activity and promote the activity of pancreatic enzymes.

Question 27

What are some of the enzymes found in pancreatic juice?

Answer 27

- pancreatic amylase (digests starch) - pancreatic lipase (digests triglycerides) - proteases (digests protein) - ribonuclease and deoxyribonuclease (digests RNA and DNA)