Digestive System

Question 1

What is the digestive system?

Answer 1

Mouth 
Oesophagus
Stomach
Duodenum 
Jejunum
Ilium 
Large intestine (colon) 
Rectum

Question 2

What is the order of the large intestine?

Answer 2

Caecum, ascending colon, transverse colon, descending colon, sigmoid colon

Question 3

What is the peritoneum?

Answer 3

Serosa double membrane surround the organs of the GI tract in the abdomen (except the duodenum). Connects to the abdomen wall by the mesentery

Question 4

What are the 4 layers of the gut wall

Answer 4

Mucosa
Submucosa
Muscularis externa
Serosa

Question 5

What are the three layers of the gut mucosa?

Answer 5

Epithelium
Lamina propria - connective tissue, mucosal glands, peyers patches
Muscularis mucosae - smooth muscle

Question 6

What does the submucosa of the gut contain?

Answer 6

Connective tissue with glands, arteries, veins and nerves.

Question 7

What does the muscularis externa?

Answer 7

Two layers of smooth muscle - inner circular layer and outer longitudinal layer

Question 8

What is digestion?

Answer 8

Conversion of what we eat (by physical and chemical disruption) into a solution of neutral pH, relatively sterile and isotonic from which we can absorb nutrients

Question 9

What is the physical disruption occurring in the mouth?

Answer 9

Action of the teeth, tongue and muscles of mastication act to break down food

Question 10

What are four functions of saliva?

Answer 10

Salivary amylase and lipase - start breakdown of food
Bacteriostatic - contain immunoglobulin A
High calcium - protects teeth
Protects mouth and assists swallowing - forms a food bolus
Alkaline

Question 11

Food moved through the oesophagus by ___________

Answer 11

Peristalsis

Question 12

What nerves are present in the muscularis externa of the oesophagus?

Answer 12

Submucosal plexus
Myenteric plexus
(Part of autonomic nervous system - post ganglionic neurones form plexuses - use a range of neurotransmitters)

Question 13

What are the physical and chemical functions of the stomach?

Answer 13

Physical - churning, three layers of muscle and rugae, contracts rhythmically to mix and disrupt stomach content

Chemical - acid (HCL) and proteolytic enzymes (e.g. Pepsin) breakdown food and disinfect

Question 14

What part of the GI tract acts as a primary food store?

Answer 14

Stomach (we eat faster than we digest)

Question 15

How is the stomach itself protected from degradation?

Answer 15

Contain mucous secreting cells, thick layer of mucus - resistant to pepsin degradation, contains bicarbonate (neutralise H+) protects stomach lining

Question 16

What is the product of stomach digestion (transported to the duodenum)?

Answer 16

Produces hypertonic chyme (partially digested stomach content) slowly (controlled) to duodenum

Question 17

What happens in the duodenum? (4)

Answer 17

Walls contain brunners glands - secret bicarbonate rich mucus to neutralise acidic chyme
Water drawn in from extracellular fluid - dilutes chyme
Liver secrets bile (via gallbladder) contains water, alkali and bile salts (emulsify fats)
Pancreas, liver and intestine secrete specific enzymes (act with bile) to complete digestion of chyme

Question 18

What three things are required for absorption?

Answer 18

Active process (lots of ATP)
Large surface area
Good blood supply/drainage

Question 19

What occurs in the jejunum?

Answer 19

Most of the absorption - most sugars, amino acids and fatty acids

Question 20

What are plicae circulares?

Answer 20

Circular folds of mucosa and submucosa that project into the gut lumen (present in the jejunum)

Question 21

What happens in the ilium?

Answer 21

Absorbs vitamin 12, bile acid and remaining nutrients

Question 22

What happens in the large intestine?

Answer 22

Water recovery
Electrolyte absorption
Crypts of lieberkuhn secrete a lot of mucus (goblet cells)

Question 23

What are three functions of bacteria in the colon?

Answer 23

Synthesis of vitamins K, B12, thiamine and riboflavin
Breakdown of bile acids
Conversion of bilirubin to non-pigmented metabolites
Competition for pathogenic bacteria - physical barrier

Question 24

What are some of the defences the colon has against pathogens?

Answer 24

Mucus layer
Immunoglobulin A 
Tight junctions
High turnover of cells
Peyers patches

Question 25

What is the function of histamine in digestion and what type of signalling does it show?

Answer 25

Paracrine signalling - acts locally controlling the production of stomach acid

Question 26

What is secretin?

Answer 26

Peptide hormone - promotes bicarbonate secretion from the pancreas and promotes bile production in the liver. Also inhibits the secretion of acid by parietal cells of the stomach

Question 27

What is cholecystokinin (CCK)?

Answer 27

Peptide hormone synthesised and secreted by entero-endocrine cells of the duodenum. Promotes release of digestive enzymes from the pancreas and release of bile from the gallbladder (stimulates it to contract). Acts as a hunger suppressant.

Question 28

What is gastrin?

Answer 28

Peptide hormone released by G cells of pyloric antrum of stomach, pancreas and duodenum. Promotes production of gastric acid (HcL) by parietal cells of the stomach.

Question 29

What are the three phases of swallowing?

Answer 29

Oral phase - chewing, makes bolus, soft pallet stays down to protect nose. Epiglottis sits over trachea to prevent food down windpipe (upper oesophageal sphincter closed)
Pharyngeal phase - upper oesophageal sphincter opens
Oesophageal phase - upper oesophageal sphincter closes

Question 30

What is harder to swallow - liquids or solids?

Answer 30

Liquids are harder- move with gravity, harder to coordinate by muscle

Question 31

What is aspiration?

Answer 31

When swallowing goes wrong.

Food, saliva, liquids etc goes into lungs