Organisation of GI Tract, Salivary glands+swallowing reflex 1

Question 1

LEARNING OBJECTIVES:

*Gut functions
*Gut wall
*Control of Digestive Activity
-Central role of neural and endocrine
pathways
*Salivary glands and secretion
*Swallowing reflex

Question 2

*proximal distal
1. Salivary secretion,
swallowing reflex
2. Stomach
3. Small intestine
4. Liver and pancreas
5. Large intestine

Question 3

Gut general functions: 5

Answer 3

Motility - movement down through tube
Some shunting back and forth, especially in small intestine
Secretion - derived from circulation system plasma
Digestion - product of carbohydrates, proteins and fats to absorption units
Absorption - movement from material from tube into tissue
Immunological - GALT gives protective

Question 4

Small intestine - primary role?

Answer 4

Absorption

Question 5

Where does most absorption occur in small intestine?
What is absorbed?
Does it have abundant reserve absorptive cavity?

Answer 5

Duodenum and jejunum
Carbohydrates, proteins and fats
Electrolytes vitamins and water from them^
Yes - caveat: terminal ileum

Question 6

Energy rich nutrients are derived from food so that these absorption units can be taken up by the circulatory system:
The role of the digestive system is to convert 1,2,3 into absorption foods what are they converted into:
1.Carbohydrates?
2. Proteins?
3. Fats?

Answer 6

1. Monosaccharides - sugar chains
2. Amino acids
3. Fatty acids and glycerol - more complex in management

Question 7

Digestive tract wall - what tissue types? 5

Answer 7

Epithelium, Lymphoid tissues Connective tissue, Nerve plexuses and Smooth muscle

Question 8

Parts of digestive tract wall
1. Inner - mucosa what parts does it contain and what kind of tissue layer do they have?
2. Submucosa?
3. Muscularis externa?
4. Myenteric plexus?
5. Enteric NS?
6. 2 others?

Answer 8

1. Membrane membrane: epithelium lining
   Lamina propria: connective tissue layer
   Muscularis mucosa: smooth muscle layer
2. Connective tissue layer that gives distension and flex
   NB collection of nerves here: plexisim network associated called the submucosal plexus
3. 2 muscle layers orginated in 2 different places Outer longitudinal layer: fibres original length ways along tube which shortens at contraction.
   Inner circular muscle: contracts and re diameter
4. Associated with muscularis externa
5. Myenteric plexus and submuocsal plexus
6. Serosa and mesentery

SLIDE 7 DIAGRAM SEE

Question 9

Central role of neural and endocrine pathways?
4 Important factors?

Answer 9

Control of motility and secretion
1. Autonomous smooth muscle function
2. Intrinsic nerves
3. Extrinsic nerves
4. Gastrointestinal hormones

DIAGRAM SLIDE 8

Question 10

1. What does receptor activation alter?
2. Receptors in digestive tract?
3. Intrinsic nerve plexuses what kind of reflex?
4. Extrinsic autonomic nerves what kind of reflex?
5. Intrinsic nerve plexus, extrinsic autonomic nerves, Gastrointestinal hormones what effects do these have?

Answer 10

1. Digestive Activity via neural and hormonal pathways
2. Chemoreceptors, mechanoreceptors, osmoreceptors
3. Short reflex
4. Long reflex
5. Smooth muscle: contraction for motility
   Exocrine gland cells: secretion of digestive juices
   Endocrine gland cells: Secretion of GI and pancreatic hormones

Question 11

Is smooth muscle self excitable?

Answer 11

Yes

Question 12

CNS?
PNS?

Answer 12

CNS - brain and spinal cord
PNS - nerve fibres carry information between CNS and body

Question 13

PNS
1. Afferent?
2. Efferent?
3. Efferent is broken into?
4. Somatic nervous system?
5. Autonomic nervous system?
6. Autonomic nervous system is split up into?

Answer 13

1. Information from periphery to CNS via sensory neurons
2. Information from CNS to periphery
3. Somatic and autonomic nervous system
4. Skeletal muscle: voluntary
5. Smooth muscle: - gut, blood vessels bladder: involuntary
6. Parasympathetic and sympathetic nervous system

Question 14

Parotid gland - what kind of gland is it?
Where is it located?
Parotid duct?
What does duct produce?
Dissect parotid by slicing through and staining with?
What is shown?
Dysfunction in parotid can effect which nerves?

Answer 14

It is a Salivary gland
Near ear, it extends across masseter, once past it goes through buccinator
Penetrates buccinator opposite crown of 2nd upper molar tooth
Serous secretion
H+E stain
Purple staining cells: serous secreting gland which contains amylase to break down carbohydrates
Facial nerves

Question 15

What kind of gland is a submandibular gland?
What does it look like?
Where is it?
Where does the submandibular duct merge from?
What kind of secretion does it make?
Flap of tissue under the tongue is called?
What nerve does it come across?
How does this mixed gland stain?
What is the mucous secretion for?

Answer 15

Salivary gland
Hook shaped with superficial and deep arms
Inside mandible looking at back - at floor of mouth
Merges from deep part to open on sublingual papilla: runs medial to sublingual gland and comes up into oral cavity
Produces a mixed mucous/serous secretion
Lingual Ferenum
Lingual nerve
Stains lighter
Lube and protection

Question 16

What kind of gland is sublingual gland?
What does it look like?
Is there one on the left/right or both?
What does the sublingual duct drain into?
What kind of secretion does it make?
Predominant what type of secretion is that even though it is still classed as a mixed gland?
Where does it come into the oral cavity?

Answer 16

Salivary gland
Almond shaped lying lateral to submandibular duct
One left+right =both
Drains into oral cavity via several minor ducts
Produces a mixed secretion
Predominant mucous secreting
Comes in at sublingual folds

Question 17

3 Major salivary glands?

Answer 17

Sublingual, Parotid and Submandibular Glands

Question 18

What does tonic low-level parasympathetic stimulation induce?
What does it innervate?
What does it ensure?
How much saliva is made per day?
How can this salivary secretion be enhanced?

Answer 18

Production of basal salivary secretion
It innervates the above glands
Ensures saliva is constantly produced
1-2L of saliva made per day
Can be enhanced by 2 salivary reflexes

Question 19

How may salivary secretion be increased?
Explain this

Answer 19

2 types of salivary reflexes: conditioned and simple

Positive feedback

Input to cerebral cortex which goes to salivary centre in medulla and then:
1. Pressure receptors and chemoreceptors in mouth
2. Autonomic nerves - salivary glands - increased salivary secretion

Question 20

In terms of digestion what is the steps of preprocessing of the bolus in the mouth?

Answer 20

1. Sensory analysis of material before swallowing
2. Mechanical processing (teeth, tongue, palate)
3. Lubrication (mucus, and salivary gland secretions)
4. Sterilisation (lysozyme, lactoferrin)
5. Neutralisation (bicarbonate)
6. Beginning of digestion (amylase)

Question 21

2 Major divisions include the organs of digestive system and glands, what are these?

Answer 21

Organs of digestive system and glands
Organs - Oral cavity, pharynx, stomach, small intestine: duodenum, jejium, illium and large intestine
Glands - Salivary glands, liver, gall blader, etc

Question 22

Digestive system is what kind of tube and what length when dissected and when in vivo?

Answer 22

Simple hollow tube
Dissected: 30ft
In vivo: 15ft

Question 23

What does the small intestine do in terms of calcium and iron?

Answer 23

It will adjust Iron are calcium absorption, depending on physical requirements

Question 24

Small intestine is a very efficient system, when are most materials absorbed?
SI structure function is relative what does this mean?

Answer 24

Before ileum
SI will adapt to suit role
Has mechanisms for transporting materials especially for the reabsorption of vile involved in fat absorption and absorption if vitamins

Question 25

Lamina propria contains what? Explain this abbreviation:

Answer 25

Lamina propria contains GALT The Gut-Associated Lymphoid Tissue (GALT)

Question 26

What are the intrinsic nerves of digestive tract wall made up of? What do they respond to? What is their function? Is there control local or distal?

Answer 26

Submucosal and myenteric plexus, Enteric NS, Intrinsic nerves plexus Respond locally to chemical mechanical, osmolarity changes in DT wall Control motility and secretion in DT Local control

Question 27

What is the extrinsic nerve of the digestive tract? What doe sit respond to? Role of ANS here?

Answer 27

Vagal nerve Responds to external stimuli such as smell food or see food being made ANS will input onto DS to control secretion and motility.

Question 28

Gi hormones are relative locally in digestive tract what do they modulate?

Answer 28

Motility and secretion

Question 29

What role does the ANS have in secretion and motility

Answer 29

Parasympathetic NS increases secretions and motility and sympathetic does the opposite so decreases

Question 30

What does the simple reflex cause? What causes this, give an example? Where does it send afferent input to? Where is the NS salivary centre located? What happens after the input to salivary centre? Does mechanical distention cause this?

Answer 30

Increased saliva secretion Pressure or chemical changes in oral cavity such as ingesting food Salivary centre Medulla in brain stem Efferent output is sent to autonomic nerves to salivary glands to increase salivary secretion Yes, it takes place when any mech distention occurs ie dentist, food etc. Distention in oral cavity is inducing simple reflex

Question 31

How is the conditioned reflex different to the simple reflex? Give an example? Where is it made? Once input is sent to medulla what happens?

Answer 31

It is due to experience and acts as a learned response For example you see food you salivate At higher cortical levels which sends inputs down to the medulla Promotes autonomic nervous input to salivary glans to release this secretion

Question 32

What is bolus? There is sensory analysis of material when eating, what does this mean?

Answer 32

Ball of material in oral cavity Push bolus around against cheeks with tongue for sensory analyis

Question 33

Explain the 11 steps of the swallowing reflex - the oropharyngeal stage?

Answer 33

1. Swallowing is initiated voluntarily. At the start of the swallow, the tongue presses the bolus agains hard palate. 2. The tongue propels bolus to the pharynx 3. Swallowing centre inhibits respiratory centre in brain stem. 4. Elevation of uvula prevents food from entering nasal passageways. 5. Position of tongue prevents food from reentering mouth. 6. Tight alignment of vocal cords prevents food from entering trachae. 7. Epiglottis folds over closed glottis. 8. Contraction of pharyngeal muscles pushes bolus through opened pharyngoesophageal sphincter into esophagus. 9. Pharyngoesophageal sphincter closes, oropharyngeal structures return to resting position and breathing resumes. 10. Peristalsis propels bolus down length of esophagus. 11. Gastroesophageal sphincter relaxes as peristalsis pushes bolus into stomach. Swallow is complete. Sphincter again contracts

Question 34

During swallowing reflex where is the oesophagus? What does it pass between? What does it run from? What is significant in its structure?

Answer 34

*Oesophagus is posterior to trachea in superior mediastinum *Significant mobility in structure *Passes between pharynx and stomach *Runs from CVI to TXI

Question 35

Peristalsis is a wave of contraction - what does this mean?

Answer 35

*Basic electrical rhythm (BER) sets up a wave of contraction in the muscularis externa

Question 36

RECOMMENDED READING: *Human Physiology: From Cells to Systems. Lauralee Sherwood *Principles of Human Physiology. Cindy Stanfield *Grays Anatomy for Students. Drake, Vogl and Mitchell.

Question 37

How many inches from pharynx to stomach?

Answer 37

10 inches

Question 38

Peristalsis waves - fast/slow? Is there membrane depolarisation? Action potential of peristalsis relative to?

Answer 38

Normally more slow waves but can fast Yes membrane depolarisation in rhythmic contraction AP relative to contraction of muscular layers