GI System

Question 1

What is the mucosa layer of the GI made up of?

Answer 1

epithelium
lamina propria
muscularis mucosa

Question 2

Properties of epithelium in GI?

Answer 2

continuous lining in GI tract
shed and replaced every 2-3 days
apical side faces GI lumen, basolateral side faces interstitium and vasculature
extent of vili and crypts depend on the section function of GI

Question 3

What is the lamina propria?

Answer 3

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

Question 4

What is the muscularis mucosa?

Answer 4

thin layer of smooth muscle that increases surface area by creating ridges and folds

Question 5

What is the submucosa?

Answer 5

Thicker layer with similar composition to lamina propria
incorporates blood vessels and nerve bundles that form a submucosal plexus- it is an integral part of enteric nervous system

Question 6

What is the Meissner Plexus?

Answer 6

Submucosal plexus

Question 7

What is the muscularis externa made up of?

Answer 7

circular muscle
myenteric plexus
longitudinal muscle

Question 8

What is the Auerbach plexus?

Answer 8

Myenteric plexus

Question 9

Properties of muscularis externa

Answer 9

ENS coordinates contractions to mix and move contents between compartments, sphincters regulate this flow.

Question 10

What makes up the serosa?

Answer 10

Outermost layer of connective tissue and squamous epithelial cells

Question 11

What do sections of the GI tract have if they do not have a serosal layer?

Answer 11

They connect directly with adventitia

Question 12

What divisions of the autonomic nervous system regulate the GI?

Answer 12

parasympathetic
sympathetic
enteric

Question 13

Where is GI innervation from the parasympathetic nervous system derived from?

Answer 13

Vagus in the medulla oblongata

Pelvic splanchnic nerves in S2-S4

Question 14

What stimulates the sensory and motor components of the parasympathetic NS?

Answer 14

stretch
pressure
temperature
osmolarity

Question 15

What are the primary transmitters of the parasympathetic NS in the GI?

Answer 15

acetylcholine ACh
gastric-releasing peptide
substance P

Question 16

What processes does the parasympathetic nervous system facilitate in GI system? *

Answer 16

digestion and absorption of nutrients

Question 17

Where does the nerves of the sympathetic nervous system originate and synapse?

Answer 17

Originate:
thoracic region T5-T12
lumbar region  L1-L3
celiac ganglion
Synapse:
superior mesenteric ganglion
inferior mesenteric ganglion

Question 18

What innverates the upper GI region? (sympathetic NS)

Answer 18

Nerves that synapse in superior cervical ganglion

decreases GI secretions and motility

Question 19

Organisation of ENS nerves?

Answer 19

myenteric and submucosal plexuses

Question 20

Operation of ENS?

Answer 20

Autonomously by intrinsic regulation and sensory reflexes

Question 21

Properties of myenteric plexus?

Answer 21

dense parallel neuronal configuration
regulates intestinal smooth muscle
tonic and rhythmic contractions

Question 22

Properties of submucosal plexus?

Answer 22

regulates intestinal secretion and local absorptive environment
can synapse on blood vessels, circular muscle and longitudinal muscle, and muscularis mucosa

Question 23

What supports ENS neurons?

Answer 23

enteric glial cells that resemble brain astrocytes

Question 24

What regulates ENS reflexes?

Answer 24

Neural circuits involving mechanoreceptor or chemoreceptor stimulation in mucosa

Question 25

Explain how a signal is transmitted in ENS?

Answer 25

Signal transmitted to neurons in submucosal plexus, which stimulate other neurons in submucosal or myenteric plexus that regulate endocrine or secretory cells

Question 26

What neurotransmitters are used by ENS?

Answer 26

enkephalins: constrict circular muscle around sphincters | VIP, substance P, ACh, nitric oxide and seratonin

Question 27

Explain cephalic phase of digestion*

Answer 27

triggered by the thought of food | Neural and causes release of ACh and VIP which stimulates secretion by salivary glands, stomach, pancreas, intestines

Question 28

Explain the gastric phase of digestion*

Answer 28

begins when food or oral secretions enter stomach coincides with distension neural, hormonal and paracrine GI responses

Question 29

Explain intestinal phase of digestion*

Answer 29

begins when stomach contents reaches duodenum | hormone, paracrine and neural responses

Question 30

GI hormones

Answer 30

``` cholecystokinin gastrin glucose dependent insulinotropic peptide motilin sectretin ```

Question 31

GI paracrines

Answer 31

histamine (increases secretion) somatostatin (decrease secretion) prostagladins (decrease secretion)

Question 32

What is the role of the upper GI tract?

Answer 32

transports and prepares food for absorption- breaking food down and hydrating to improve environment for enzymatic action

Question 33

Role of mouth*

Answer 33

mechanical and chemical breakdown with mastication (chewing)

Question 34

Role of salivary glands

Answer 34

Produces saliva by sublingual and submandibular and parotid glands lubricates mouth, begins food digestion and is protective

Question 35

What type of process is swallowing?*

Answer 35

A parasympathetic process | provides afferent feedback to swallowing centre and efferent responses through other nuclei

Question 36

Describe the process of swallowing*

Answer 36

tongue forces food back to initiate voluntary process soft palate pulled upward to close access to nasopharynx larynx and hyoid bone pulled upwards and epiglottis closes off access to larynx upper esophageal sphincter relaxes to allow food to enter esophagus

Question 37

What is peristalsis? *

Answer 37

A series of coordinated muscle contractions/relaxations that commence after the upper esophageal sphincter and propels food down oesophagus

Question 38

What are the functions of the stomach?

Answer 38

accept and store food mix food with secretions digest food deliver food to small intestine

Question 39

How are salivary secretions controlled?

Answer 39

by sympathetic and parasympathetic processes in 2 steps 1. Na+ and Cl- transported into duct lumen 2. ductal cells modify them by reabsorbing Na+ and Cl- and secreting HCO3 and K+

Question 40

Gastric secretions

Answer 40

``` ions water mucus from mucus neck cells pepsinogen from chief cells intrinsic factor and H+ from paritetal cells ```

Question 41

Properties of small intestine *

Answer 41

longest section where most macronutrient, vitamin and mineral absorption occurs mixing by segmentation and propulsion by peristalsis of contents made up of duodenum, then jejunum, then ileum (longest)

Question 42

Properties of large intestine *

Answer 42

consist of caecum, ascending, transverse and descending, sigmoid colon, rectum and anus where water and ion absorption take place segmentation, peristalsis and mass movement occur

Question 43

What does the ileocecal sphincter do?

Answer 43

regulates amount of chyme entering large intestine

Question 44

Function of sympathetic nervous system in relation to GI system? *

Answer 44

Sympathetic stimulation causes inhibition of gastrointestinal secretion and motor activity, and contraction of gastrointestinal sphincters and blood vessels.

Question 45

Function of enteric nervous system in relation to GI system? *

Answer 45

It contains full reflex circuits for control of intestinal motility, fluid transport, blood flow and nutrient handling.

Question 46

Role of oesophagus? *

Answer 46

Transports food from mouth to stomach

Question 47

What are the different parts of the stomach from top to bottom?

Answer 47

Fundus Body Antrum Pyloric sphincter

Question 48

What are the layers of the GI from inside to out?

Answer 48

Mucosa Submucosa Muscularis externa Serosa