Basic structure of GI

Question 1

Role of the GI tract

Answer 1

Bring nutrients/water into internal
environment to be used by the body

Question 2

Roles of the GI tract

Answer 2

• Motility
• Secretion
• Digestion
• Absorption

Question 3

Motility

Answer 3

Transport food into & through the body, mixing luminal contents, and transport waste out

Question 4

Secretion

Answer 4

Synthesise and release enzymes,
mucus & serous fluid into the lumen

Question 5

Digestion

Answer 5

Break nutrients into smaller pieces
(mechanically and chemically)

Question 6

Absorption

Answer 6

Bring nutrients/water from the lumen to
internal environment

Question 7

Why does the GI tract have different areas and how are they seperated?

Answer 7

They have different functions and they are seperated by Sphincters

Question 8

Components of the main tube

Answer 8

Oral cavity –> pharynx –> eso –> stomach –> SI –> LI –> Anus

Question 9

What are the outgrowths of the main tube called

Answer 9

The accessory structures

Question 10

Where are the different sphincters

Answer 10

*Mouth
*Base of eso to control flow into stomach + prevent backflow
* Stomach and SI to control flow
*Between SI and LI
* 2 in the anus to control defecation

Question 11

Type of epithelia in the Moth/oral cavity, pharynx and eso + their function

Answer 11

Stratified squamous epithelia

• protection from abrasion

Question 12

Type of epithelia in the Stomach, SI and LI + their function

Answer 12

Simple columnar epithelia

• Secretion and absorption

Question 13

Type of epithelia in the Anus + their function

Answer 13

Stratified squamous

• Protection from abrasion

Question 14

Why does the middle of the tract have different type of epithelia?

Answer 14

• The contents are more watery so dont have to worry about abrasion

Question 15

Unicellular glands

Answer 15

• Columnar/Goblet shape
• Secretes mucus onto the apical surface
• Basal nucleus
• Function is to lubricate the lumen and provide a barrier

Question 16

Multicellular glands

Answer 16

Epithelium can invaginate to form glands:
* Simple
* Compound

Question 17

Simple multicellular glands

Answer 17

Gland with single duct (e.g. stomach and small intestine)

Question 18

Compound multicellular glands

Answer 18

Gland with 2 or more ducts (e.g. salivary glands)

Question 19

4 layers of the gut tube

Answer 19

1. Mucosa
2. Submucosa
3. Muscularis (externa/proper)
4. Adventitia

Question 20

Components of the mucosa

Answer 20

• Epithelium connected to
• Basement membrane attatched to
• Lamina propria (made of FCT)
• Muscularis mucosae

Question 21

What can be found in the Lamina Propria

Answer 21

Blood vessels lymphatics and sometimes glands

Question 22

What does the Muscularis mucosae do

Answer 22

Band of smooth muscle that moves the mucosa

Question 23

Components of the submucosa

Answer 23

• Predom FCT
• Glands
• Blood vessels
  *Submucosal nerve plexus

Question 24

What does the Submucosal nerve plexus do?

Answer 24

Network of nerves that are part of the enteric system, controls the secretion of the glands

Question 25

The muscularis (externa/proper) components + functions

Answer 25

*Made of smooth muscle *Has two layers: inner circular arrangement and outer longitdinal arrangement *Myenteric plexus (Part of ENS) - Located between muscle layers and regulates motility

Question 26

The Adventitia

Answer 26

*Outermost layer *Mostly FCT *Supports and sometimes anchors to other organs

Question 27

What happens in the oral cavity + mouth

Answer 27

Digestion begins * Mechanical through the teeth * Chemical– requires enzymes * Lubrication needed * Passes through fauces, into oropharynx & laryngopharynx then into esophagus

Question 28

How is the oral cavity lubricated

Answer 28

Through salivary glands --> secretes watery serous fluid and mucus

Question 29

Chemical that digests carbs

Answer 29

Amylase

Question 30

Features of the salivary glands

Answer 30

3 pairs: - Parotid glands - Sublingual glands -Submandibular glands

Question 31

Parotid

Answer 31

Parotid glands are beside the ear and secrete watery serous fluid

Question 32

Sublingual

Answer 32

secrete mucus, found underneath the tongue

Question 33

Submandibular

Answer 33

found on the side of jaw, secretes both, opening at the bottom of the tongue, helps move food around when chewing

Question 34

Salivary glands have...

Answer 34

Multiple ductsW

Question 35

What is an acinus

Answer 35

cluster of cells connected to ducts that can secrete * Serous fluid & enzymes (amylase) * mucus

Question 36

What do the ducts do

Answer 36

- transport the fluids secreted by acinus to the surface - Also the cells secretes bicarbonate to act as a pH buffer as it is very basic

Question 37

Features of the eso

Answer 37

* Long tube (~25cm) that carries food from mouth to stomach * Located posterior to the trachea, extends from pharynx to stomach * Epiglottis ensures that food enters the esophagus, and not the trachea

Question 38

How is the epiglottis activated?

Answer 38

The tongue pushes back and puts pressure on the epi

Question 39

How is the eso modified

Answer 39

* First 1/3: skeletal muscle to have concious control * Middle 1/3: a mixture * Last 1/3: smooth muscle Highly folded submucosa and mucosa that flattens and unflods to allow food to pass

Question 40

Mucus around the eso

Answer 40

* Stratified squamous epithelium * Need mucus for lubrication and protection * No goblet cells, instead have glands with ducts to surface * In submucosa * Plus in mucosa close to stomach