Gastrointestinal Tract

Question 1

What is the primary function of the GI tract?

Answer 1

Absoprtion of dietary nutrients

Question 2

What 3 things make up the mucosa?

Answer 2

Epithelium, lamina propria and muscularis mucosa

Question 3

Describe the epithelium in the GI tract

Answer 3

Single cell layer, replaced every 2-3 days, apical side faces lumen, basolateral side faces interstitium

Question 4

Describe the lamina propria

Answer 4

Loose connective tissue made up of elastin and collagen fibres, contains nerves, blood and lymph vessels, secretory glands

Question 5

Describe the musclaris mucosa

Answer 5

Thin layer of smooth muscle, increases surface area by creating ridges and folds

Question 6

What are the different layers of the GI tract?

Answer 6

Mucosa, submucosa, muscularis externa and serosa

Question 7

Describe the submucosa

Answer 7

Thicker layer- similar to lamina propria

Question 8

What can be found in the submucosa layer?

Answer 8

The submucosal plexus- blood vessels and nerve bundles- integral part of the enteric nervous system

Question 9

What 3 things make up the muscularis externa?

Answer 9

Circular muscle, myenteric plexus, longitudinal muscle

Question 10

Describe the muscularis externa layer

Answer 10

ENS co-ordinates contractions to mix and move between compartments, sphincters regulate flow

Question 11

Describe the serosa layer?

Answer 11

Outermost layer of connective tissue + layer of squamous epithelial cells

Question 12

What occurs when there is no serosa layer in certain parts of the GI tract?

Answer 12

They will directly connect to the adventitia

Question 13

What 3 divisions of the autonomic nervous system regulate the GI system?

Answer 13

Parasympathetic

Sympathetic

Enteric

Question 14

Where is the PNS controlled from?

Answer 14

Medulla oblongata

Pelvic-splanchnic nerves

Question 15

What does the PNS respond to?

Answer 15

Stretch, pressure, temperature and osmolarity

Question 16

What are the primary neurotransmitters of the PNS?

Answer 16

Acetylcholine, Gastric-releasing peptide

Question 17

What does the PNS signals?

Answer 17

Stimulation of GI secretions and motility

Question 18

Where do the nerves originate from in the SNS?

Answer 18

Thorathic (T5-T12) and lumbar (L1-L3) regions

Question 19

Where is the upper Gi tract innervated from?

Answer 19

Superior cervial gaglion

Question 20

What is the SNS’ function?

Answer 20

Generally decreases GI secretions and motility

Question 21

What is the ENS usually synpased with and controlled by?

Answer 21

Both the PNS and SNS

Question 22

What can you organise the ENS nerves into?

Answer 22

Myenteric and submucosal plexuses

Question 23

How can the ENS operate autonomously?

Answer 23

Via intrinsic regulations and sensory reflexes

Question 24

Describe the myenteric plexus

Answer 24

Dense parallel neruonal configuration

Question 25

What is the function of the myenteric plexus?

Answer 25

Regulating intestinal smooth muscle by participating in tonic and rhythmic contraction

Question 26

What is the function of the submuscosal plexus?

Answer 26

Regulates intestinal secretions and local absorptive environment

Question 27

What are ENS neurons supported by?

Answer 27

Enteric glial cells

Question 28

Describe ENS reflexes

Answer 28

Neural circuits involving mechanoreceptor or chemoreceptor simulation in the mucosa, signal transmitted back to neurons in submucosal plexus

Question 29

Examples of neurotransmitters of the ENS

Answer 29

Enkephalins- constrict muscle around sphincter VIP, substance P, ACh, nitric oxide, serotonin

Question 30

What are the non-neuronal signalling molecules?

Answer 30

Hormones and paracrines

Question 31

Give some example of GI hormones

Answer 31

Gastrin- increases gastric acid secretion Secretin- Releases HCO3- and pepsin

Question 32

Give some examples of GI paracrines

Answer 32

Histamine- increases gastric acid secretion Somatostatin- Inhibits peptide hormones and gastric acid secretion

Question 33

What are the 3 phases of digestion?

Answer 33

Cephalic, gastric and intestinal phase

Question 34

Describe the Cephalic phase of digestion

Answer 34

Triggered by thought of food Primarily neural and causes ACh and VIP release- stimulates secretion

Question 35

Describe the Gastric phase of digestion

Answer 35

Begins when food and oral secretions enter stomach Coincides with distension Elicits neural, hormonal, paracrine GI responses

Question 36

Describe the Intestinal phase of digestion

Answer 36

Begins when stomach contents reach duodenum Initiates primarily hormonal, paracrine and neural responses

Question 37

What is included in the upper GI tract?

Answer 37

Mouth, oesophagus and stomach

Question 38

What is the function of the upper GI tract?

Answer 38

Transports and prepares food to be absorbed

Question 39

What is the function of the mouth?

Answer 39

Mechanical + chemical breakdown

Question 40

What does mastication mean?

Answer 40

Chewing

Question 41

What is the order of the type of teeth working front to back?

Answer 41

Incisors, canine, premolar and molars

Question 42

What are the four basic structures of a tooth?

Answer 42

Enamel, dentin, pulp cavity and root canal

Question 43

Describe the function of the salivary glands?

Answer 43

Produces watery fluid which; lubricates mouth, digest

Question 44

What produces saliva?

Answer 44

Sublingual, submandibular and parotid glands

Question 45

Describe peristalsis

Answer 45

Series of co-ordinated muscle contractions/relaxations

Question 46

What are the functions of the stomach?

Answer 46

Accept and store food Mix food with secretions Digest food Deliver food to small intestines

Question 47

What muscle allows food to enter the stomach?

Answer 47

Lower eophageal sphincter

Question 48

What muscle allows food to enter the duodenum?

Answer 48

Pyloric sphincter

Question 49

Where do secretions come from in the stomach?

Answer 49

Pits

Question 50

What cells make up the pits in the stomach?

Answer 50

Within the neck- mucous neck cell, G and D cells Within the base- chief cell and parietal cell

Question 51

What are the three parts of the small intestines?

Answer 51

Duodenum, jejunum and ileum

Question 52

What parts make up the large intestines?

Answer 52

Caecum Ascending, transverse, descending, sigmoid colon Rectum Anus

Question 53

What is the function of the large intestine?

Answer 53

Significant water and ion absorption, motility of contents