Mastication: the process of chewing your food. ○
Deglutition: the process of swallowing. ○
Partly regulated the enteric nervous system (another branch of the PNS)
Peristalsis: alternating waves of muscle contraction and relaxation used to move food through the GI tract. ○
Definitions •
Help keep food in the oral cavity
Lower and upper lips (labia) ○
Appendages that attach the labia to the gums
Limit the mobility that the lips have
Superior and inferior labial frenula ○
Limits posterior movement of the tongue … stops you from …
Lingulal frenulum ○
At the base of the tongue (and the base of the lingulal frenulum?)
Produces saliva
Controlled by CN7 (which also provides the sensations from the anterior two thirds of the tongues)
Submendibular gland ○
Part of the soft pallet
Responsible for closing nasal cavity when you have food
Uvula ○
Goes from the pallet to the tongue
Palatoglossal arch ○
Goes from the pallet to the ______
Palatopharyngeal arch ○
Mucosal Associated lymphoid tissue
Between the arches Tonsils ○ ○ Mouth • Sweet Bitter Salty Sour Umami Primary tastes ○
Most of the approximately 10,000 taste buds are found on the tongue. ○
These are raised projections □
12 each containing 100- 300 taste buds. □
Vallate papillae:
Taste buds are found on the papillae of the tongue: ○
Gustation •
GI-1
12 each containing 100- 300 taste buds. □
Scattered over tongue each containing 5 taste buds. □
Fungiform papillae:
In the lateral margins of tongue; degenerate in childhood. □
Account for the changes in your taste preference as you grow older □
Foliate papillae:
Helps create friction for your food □
Don’t have taste buds associated with them □
Falliform papillae
Modified neuronal cells
Constantly renew themselves
These are your taste receptors
Also passes through the thalamus □
Synapse with a sensory neuron to send the signal in the primary gustatory cortex in the temporal lobe
Gustatory Receptor Cells ○
Anterior 2/3 of the tongue □
Facial (VII)
Posterior 1/3 of the tongue □
Glossopharyngeal (IX)
Throat (edges of the pharynx?) and epiglottis □
Vagus (X)
Nuclei arise from the brain stem □
Signal relayed through the thalamus □
Nerves
Cranial Nerves ○
Taste is combined with smell
Smell involves CN1 … another example where the CNS escapes the bony confines of the skull … cell bodies are sitting right in the mucous membrane
Cells are specialized to recognize odorant molecules … and to do this the stuff have to be dissolved in the liquid
Therefore if you smoke and it dries the nose … it will be hard to smell
Olfaction ○
Teeth, Tongue, Cheek Saliva Muscles of Mastication Mastication requires: ○
Partly voluntary and partly reflex (stretch receptors in the cheeks).
Note ○
Cutting □
Four above and four below □
Incisors
Tearing □
Two above and two below □
Canine
Crushing □
Four above and four below □ Premolars Grinding □ Molars
Full complement is 32 when you have all your molars (including wisdom teeth)
Note □
The one that you lose early on
Deciduous □
It comes behind the deciduous and push out the deciduous
As the permanent teeth grow, they will grow up or down and push out the deciduous Permanent □ Dentitions Crown Neck
Embedded in the bone of the maxilla ◊
Held in place by connective tissue … (loosen up in scurvy) ◊
Root
Top to bottom □
Has a lot of calcium cells (more than the bones you have)
Dentin □
95% calcium cells
Hardest substance in the body
Enamel □
Neurovascular bundle supplies each tooth CN5 is involved AVN □ Closer Look Teeth ○
Help to change the shape of the tongue □
Can't help you stick your tongue out! □ Intrinsic muscles Tongue ○ Mastication •
Can't help you stick your tongue out! □
Superior and inferior
Contraction = tongue gets shorter
Longitudinal muscles □
Superior and inferior
Contraction together = make tongue skinnier
Contraction of one group = curling the tongue
Transverse muscles □
Contraction = flattening the tongue out
Vertical muscles □
Connect to a bone as well as the tongue □
Attaches to the base of the tongue and then the hyoid bone
Brings the base of the tongue down … letting you put it on the floor on the mouth
Hyoglossus □
Attaches to the base of the tongue and the styloid process (by the mastoid process)
Helps you move the tongue up to the roof
Styloglossus □
Attached to the anterior aspect of the mandible and then the base of the tongue
Let's you stick the tongue out
Genioglossus □
Hypoglossal nerve
Hypo = below … glossal = tongue
CN12 □
Extrinsic muscles
Help move the mandible up towards the maxilla □
Introduction
Right on top of the temporal bone □
Bulges on the side of the skull when you chew □
CN5 □ Temporalis
Runs from the maxilla down to the mandible □
Most beast of them all □
CN5 □ Masseter
Contributes to most of the muscle mass when you cheek □
Used for blowing □
CN7 (facial cause blowing changes the shape of your face) □
Buccinator
Allows you to close your lips □ Cn7 □ Obicularis Oris Muscles of Mastication ○
Intrinsic tongue muscles (4) Hypoglossal Extrinsic tongue muscles (3) Hypoglossal
Temporalis Trigeminal
Masseter Trigeminal
Buccinator Facial
Orbicularis oris Facial
Muscle Summary ○
Also involved for sensations from the teeth □
CN5
Also allows you to convey sensations from the anterior two thirds of the tongue □
Controls secretions from the submandibular and sublingulal glands □
Parasympathetic functions is built into it
Innervation □
CN7
Posterior 1/3 of the tongue sensations □
Controls parasympathetic saliva secretion from the parotid gland (by the ear) □
CN9
CN12
Cranial Nerves - Extra ○
Muscles of mastication are controlled by the somatic nervous system Symp □ Parasymp □ Enteric □ Not: iClicker ○
Comes as a branch from the external carotid
Right or left facial artery □ Arteries Facial vein □ Drainage Vascular Supply ○ Saliva
Parotid (CN9) □ Submandibular (CN7) □ Sublingual (CN7) □
3 major extrinsic salivary glands:
Pump cloride and sodium out so water follows into salivary gland
Water □
Amylase □
Helps make saliva gummy Mucin □ Lysozyme □ IgA □ Defensins □ Electrolytes □ Composition (1-1 ½ litres/day):
Parasympathetic (CN VII and IX) results in watery, enzyme-rich saliva. □
Sympathetic results in thick mucin-rich saliva. □
Control
Parotid Only serous (with amylase)
Submandibular Mostly serous Sublingual
This is the only one active with symp innervation? •
Note: lipase only works at lower pH … secrete it right now so when it goes to the stomach it works •
Mostly mucous (with lipase) □
(SA)(S)(ML)
Acronym □
Different salivary gland = different composition
Saliva ○
Trachea conducts air up past the epiglottis through the oropharynx through the oral and maybe nasal cavity
Food must come down through the oral cavity to get to the esophagus
Air coming out and food coming down together makes it likely to food get down to the lungs (more likely right lung)
Talking with Mouth Full ○
After mastication and added some enzymes □
Need to get food to the stomach □
Introduction
All voluntary □
Using tongue to push food up against the soft pallet at the back of the mouth which set off stretch receptors to continue the rest of the swallowing manouver
□ Oral Phase
Involves the oropharynx and laryngeopharynx □
Involuntary □
As the sphincter relaxes, the larynx moves up to close the epiglottis to protect trachea … also this sphincter is skeletal muscle (?)
Contracting muscles in the pharynx to milk to the food to the esophagus (where the sphincter that closes it opens) □
Then the sphincter will close and the peristaltic waves will begin to dump food in the stomach □
Phrayngeal phase
Between (a) and (b), the epiglottis closes off the opening to the trachea while the uvula closes off the opening to the nasal cavity □
Early Deglutination ○
Some people have a hard time swallowing pills □
Difficulty initiating swallowing
Soft pallet doesn’t separate nasal from oral cavity □
Milk coming through the nose □
Nasophryngeal regurgitation
Epiglottis doesn’t function or larynx doesn’t move up properly □
Pulmonary aspiration
If you havent produced enough saliva, can get dried bits of it being stuck at the margins of the tongue □
Residual
Disordered Swallowing ○
These make a kink in the esophagus
Passes structures that are ridges like the bifurcation of the broni + behind left atrium + skeletal muscle of diaphragm (?) □ Journey Blood Supply Esophagus ○ Swallowing •
Note from the aorta also comes the broncihals
Branches from the descending thoracic aorta … tiny blood vessels called esophageals □
Esophageal veins … which drain into hemizygous vein (on the left side of the thoracic cavity)
Drainage □
Blood Supply
Doesn’t aid in mechanical or chemical digestion … is just a conduit □
Lots of friction … need a stratified layer
Stratified squamous epithelium ◊
Mucosa
Submucosa
Inner circular and outer longitudinal layer ◊
Work together to help push food from the oral cavity to the stomach ◊
Circular layer causes the lumen to get smaller ◊
Longitudinal layers helps shorten the path ◊ Muscularis Adventitia Layers □
Some people say he meant columnar? … ◊
Most of the rest of the GI tract is simple cuboidal epithelium Note: □ Histology Skeletal muscle First 1/3 □
Mixture of smooth and skeletal
Second 1/3 □
Completely smooth muscle
Final 1/3 □
Divisions
Sits at the level of the diaphragm □
Food going from the lower portions of the esophagus to the stomach … has to pass through the lower esophageal spincter
This is all involuntary
Late Deglutition ○
Tongue pushes masticated food towards oropharynx
Uvula closes of nasopharynx
Larynx elevates and epiglottis closes off trachea
Pharyngeal muscles push bolus passed UES
Skeletal m. in first 1/3 of esophagus pushes bolus toward involuntary section (smooth m. controlled by ANS and E-(enteric)-NS)
LES (lower esophageal spinchter) opens and bolus enters the stomach (AKA the “grinder”)
Deglutition - Review ○
Something is travelling backwards … in this case it’s the acidic contents of the stomach
Reflux ○
Isn't that great … has to rely on the diaphragm to help
If the stomach goes through the hole (herniates) in the diaphragm (esophageal hiatus?), you don’t have the diaphragm helping close the sphincter
Muscosal lining of the esophagus erodes due to the acidic stuff that is coming backwards into it
Lower esophageal sphincter ○
Heartburn is often confused with cardiac disease. … □ Causes … □ Treatments Notes ○
Gastroesophageal Reflux Disease •
Simple cuboidal □
Epithelium
Tied epithelium down (connective tissue) □
Lamin propria
Muscle that helps puts the epithelium above into folds □
Muscularis mucosa
Mucosa (Mucus Membrane) (Innermost) ○
Find glands … mucous glands □
In stomach it will be glands that produce HCl □
Well vascularized to help the glands □ General Submocosa ○ For peristalsis □ Inner circular For peristalsis □ Outer longitudinal Muscularis Externa ○
Secrete serosal fluid □ Mesothelium CT (thin) Serosa ○ Basic Plan • Control of peristalsis…
Can function independently of symp, para or technically even somatic input (even though you wouldn’t find somatic in GI)
General ○
Alternating waves of muscle contraction and relaxation used to move food through the GI tract.
Peristalsis: ○
100+ million neurons from esophagus to anus
Associated with the muscles
Myenteric plexus (between circ. and long. Layers) □
Controls the gastric secretions (and in fact entero secretions throughout the GI tract)
Submucosal plexus (in submucosa) □
2 components:
Pacemakers of the gut □
Set up rhythm and intensity of peristaltic movement □
Interstitial cells of Cajal
ENS ○
Sensed by stretch receptors in the wall of the intestine (mucosal epithelium?), which signals submucosal plexus to increase secretions … and also tells muscle to set up a peristaltic wave
Food enters small intestine □
Referred pain with the ANS/CNS? Pain □ Secretions increase Peristalsis increases
Can talk to the target organ Parasymp □ Secretions decreases Peristalsis decreases Symp □ ANS + ENS ○ Thoracolumbar
Does this by constricting blood vessels □
Turns down everything Sympathetic Innervation ○ Cranial + sacral Parasympathetic Innervation ○
Enteric Nervous System •
GI-2
Cranial + sacral
Turns up everything
Only last portion of the intestine is done by the splanchic nerve
Does most of the visceral organs inferior to the diaphragm □
CN10
Flap that attaches the stomach to the inferior stomach of the liver □
Peritoneal fold
In order to view the LI and SI, had to pull away this □
Lesser Omentum
Ascending, transverse (right to left) and then descending portions □
Then the sigmoid portion which is curving □
Straight part at the end = rectum □
Large Colon
○
Biggest peritoneal fold □
Suspends the entire section of the small intestine from the posterior abdominal wall □
As the organs were developing to get into the abdominal cavity … … □
Mesentary
Occurs down the midline of the liver □
Suspends the liver from the inferior surface of the diaphragm … also has a small portion that attaches the liver to the anterior abdominal wall (note this is the only organ here that is attached to the anterior abdominal wall … rest are suspended from the posterior abdominal wall)
□
Falciform Ligament
Suspends the transverse colon from the posterior abdominal wall □
Meso colon
Extends from greater curvature from the stomach, goes down, up and then attaches to the transverse colon □
Fat when you become old ends up here □
Greater Omentum
Helps to suspend the stomach from the inferior surface of the liver □ Lesser Omentum FL □ LO □ MC □ GO □ M □ FLLOMC GOM Overall □ Order
Behind the parietal peritoneum □
Pancreas
Duodenum (which wraps around the pancreas)
Ascending & descending colon Kidney Structures □ Note: Retroperitoneum Diagram Peritoneum ○ Abdominal Cavity •
□ Diagram
Mechanical (e.g. stretch) stimuli □
Chemical (e.g. pH) stimuli □
Digestion depends on:
Input from the cortex
ANS (parasymp + symp)
Extrinsic nervous input □
Local reflexes (through enteric NS)
Intrinsic nervous input □
Locally at the level of the GI tract
Endocrine hormones that travel in the blood
Hormonal input □
Digestion is controlled by: Introduction ○ Digestion • Serosa □ Muscularis externa □ Submucosa □ Mucous membrane □
Standard four layers
Mucosa will be sent into these large folds called rugae
Allow stomach to really expand if necessary (not here to increase SA)
Rugae □
Additional layer of muscle … is innermost
Stomach acts like a blender … can get a lot of twisting motion going to mix food with juices
Oblique muscular layer □ Alterations Make-up ○ Closest to heart □ Cardia (top)
Top most region □
Acts as a reservoir if there is more food □ Fundus Outer longitudinal Middle circular Innermost oblique
Has the muscular layers □
Lesser is attached to the liver through the lesser omentum
One side is shorter than the other … makes a lesser and greater curvature □
Body
Working region of the stomach
Most mechanical digestion occurs here
Things get prepared from grinding
Pyloric anterom □
Pyloric canal □
Really strong spincter
Even when relaxes creates only a tiny hole Pyloris □ Pyloric region Regions ○ Denatures/digests proteins □
Extremely acidic environment (pH 1.5-3.5)
Chyme = slurry = masticated food + gastric secretions □
Breaks down, mixes and puts chyme into duodenum
Needed for hemoglobin
Needed for vitamin B12 absorption □
This absorption occurs in the distal ileum □
Produces intrinsic factor
Alcohol □
ASA (aspirin) □
Absorbs drugs like:
Characteristics ○
Supply for: Lesser curvature □ Celiac trunk Blood Supply ○ Stomach •
Left and right gastric artery
Supply for: Lesser curvature □
Left and right gastroepiploic artery
Anastomose with the gastric arteries
Supply for: Greater curvature □
Also supplies a lot of the SI □
Superior mesenteric
Inferior mesenteric
Liver filters toxins that comes through the blood that made the way through the GI tract □
Liver also responsible for storing sugars as well □
Eventually: Hepatic portal vein
Dump into HPV □
Left and right gastric
Im thinking that instead of a right gastroepiploic, there is a short gastroepiploic instead
Go into the splenic vein □
That dumps into the HPV □
Short gastric + left gastroepiploic
Drainage ○
This has the parietal (produce HCl) and chief cells □
The pit is pretty much the empty space … like the space between the two walls of the gastric wall □
In the center of the cup is where you find the gastric pit … this is where the action occurs
Blood vessels supply the glands which come through the submucosa
Contains cup shaped structures called gastric glands ○
Mucous cells at the surface
I think the neck is like the opening of the pit □
Mucous cells in the neck
Secrete HCl + make intrinsic factor □
Parietal cells
Secrete pepsinogen, which when goes into the acidic environment becomes pepsin which digest proteins □
Secretes gastric lipase … (this adds with that lingual lipase) □ Chief cells Secretes gastrin □ Turns everything on □ Parietal cells Chief cells
LES (makes it tighter)
Gastric motility
Turns up □
Pyloric sphincter (tells it to relax) Turns down □ G cells Gastric pits ○
Make the proton and chloride separately and combine them in the lumen of the stomach
Bicarbonate and H+ is made from H
2O and CO2 … proton is pumped out into the gut of the stomach
□
Chloride then goes through the apical part of the parietal cell into the gut
Bicarb cant sit around in the cell … so its shuttled out into the blood stream and through an antiporter Cl-is brought it
□
Carbonic anhydrase is involved
If you vomit a lot, you lose a lot of the protons but keep the bicarb, so you have an condition called metabolic alkalosis
Gastrin □
Parasymp nerve fibers
Ach □
From mast cells Improves HCl secretion Histamine □ Regulation HCl Factory ○ Gastric Wall •
Well before there is food □
This is thoughts of food or seeing it or smelling it or tasting □
Sends signals through paraymp … tells stomach at levels of submucosal plexus to increase gastric juices. This also causes increase in gastrin release to increase peristalsis and secretion of juices
□
Cephalic Phase
When food enteres the stomach □
Food distends the stomach … activates stretch receptors □
Food increasese pH … activates chemoreceptors □
Submucosal plexus to increase the production of HCl (homeostasis) … pH went up so u make more HCl to bring it down
G cells to increase gastrin
This sends signals to □
This leads to incresed gastric emptying □
Gastric phase
Can tell it to slow down for example
Intestines control the activities of stomach □
Stretch receptors recognize distention of the duodenum Recognition □ Intestinal Phase Phases ○ Digestion •
Get signals to brain stem, which sends symp input to submucosal plexus to decrease activity
This can result in the enterogastric reflex ◊
This is an inhibitory neural signal ◊
Stretch receptors recognize distention of the duodenum
These are enteroendrocrine cells … line the mucosa of the duodenum ◊
Acts on the smooth muscle of the stomach to decrease motility –
CCK
When there is food in the intestines, tells the cells of the gastric pits to reduce acid production to slow digestion in the stomach
–
Also inhibits gastric motility … –
Secretin Release: ◊
Chemoreceptors detect fatty acids and glucose in the duodenum
Stuff is moved to the pylorus
Propulsion □
Most of the mechanical digestion takes place at the pylorus
Grinding □
Only small bits of chyme go to the duodenum at a time … so most is pushed back into the stomach
Note: Only liquid goes to the duodenum
Retropulsion □
Steps
Increases HCl and motility
This causes increase in gastrin secretion ◊
Food in the stomach
Also parasymp innervation
Promotion □
Increases enterogastric reflex ◊
Secretion of cholesystokinin ◊
When chyme reaches duodenum, it tells the stomach to slow down
Decreases gastric motility
Inhibition □
PNS stimulates (Vagus) ◊
SNS inhibits (enterogastric reflex) ◊ Neural Gastrin stimulates ◊ CCK inhibits ◊ Hormonal
Carbs are easy to digest … if you deliver that to the duodenum, it wont tell the stomach to slow it down
Carbohydrates, water (chyme enters quickly) ◊
High protein (moderate emptying) ◊
Takes time to digest so stomach is told to slow down
Fats (chyme enters slowly) ◊
Duodenum controls gastric emptying based on content: Summary □ Control Gastric Emptying ○
Acid erodes the mucosa Hypersecretion of Acid ○ Why do we VOMIT? ○ Extreme stretch
Bacterial toxins … don’t want to absorb them □
Excessive EtOH □
Certain foods & drugs □
Irritants
Causes ○
Afferent stimulation of medulla … irritant fibers send signals up
Diaphragm (contraction) □
This + diaphragm puts pressure on stomach
Abdominal muscles (contraction) □
Pressure is relieved by stuff going up through this and out of the mouth
Relaxation of LES □
This is so food doesn’t go through nasal cavity
Closing of soft palate □
Efferent signals
Involves: ○
Activates the irritant receptors really well
Syrup of Ippicac ○
Reverse Peristalsis •
This is narrowing of the pyloric sphincter ○
The only place for gastric contents to go is up the esophagus and passed the gums ○
It is most common in first male babies ○
If mild wait … ○
If severe … treat by slitting the pyloric sphincter ○
Pyloric Stenosis •
Food in oral cavity
Ingestion ○
Overview of the Digestive Process •
Food in oral cavity
Mastication
In the stomach through the churning action of the three layers of muscle
Segmentation in the small intestine
Mechanical digestion ○
Saliva and the amylase in it □
Mouth
Gastric juices which has HCl (denature proteins) and pepsin (break down proteins) □
Stomach
Receives enzymes from the accessory organs of GI tract (liver + pancreas)