Lecture 02- Functions of the mouth and oesophagus
- Digestion
Conversion of dietary nutrients into a form that the small
intestine can absorb
Starts in the oral cavity, mouth lined by STRATIFIED SQUAMOUS
EPITHELIUM
- Teeth
Primary/deciduous dentitions include 20 teeth, permanent
dentitions include 32
Chewing can also be called mastication. This increases surface to
volume ratio and creates a larger surface area in food.
Decreases food particle size to allow better action of digestive
enzymes for better absorption
- Tongue
Papillae have taste buds which have gustatory cells or taste
receptors. Prepares food for swallowing.
- Saliva
Contains 99.5 percent water, along with electrolytes, salivary
amylase and other enzymes. Has a major role in taste, motility
and cleaning the mouth
Salivary gland:
It is an exocrine gland.
It has a branched ductal system to release secretory products
such as saliva. Secretion can either be serous (watery) or
mucous.
There are 3 glands, innervated by PNS. Parotid (Serous),
sublingual (Mucus) and submandibular (Mixed).
Cells: Acinar cells produce saliva by transporting ions across cell
membranes and goblet cells produce lubrication for hydration
purposes.
Primary saliva produced by acinar cells is isotonic and high
concentrations of Na+ and Cl-. These ions need to be removed to
make final saliva hypotonic. Hypotonic saliva is more effective in
lubricating.
, Goblet cells modify primary saliva by causing reabsorption of the
ions. Na+ through Na+K+ pumps. Cl- would be passively
reabsorbed, HCO3- generated from giblet cells and secreted into
saliva to regular pH.
Saliva is alkaline. This is because it protects against acid,
enzymatic activity, antimicrobial properties, tooth
remineralization and tissue health.
- Esophagus
Muscular tube that connects pharynx to the stomach. Main
secretion is mucus.
Upper 1/3rd is skeletal muscle: swallowing is consciously
controlled, starts peristaltic wave.
Middle 1/3rd is skeletal and smooth muscle: automated
swallowing and less conscious
Lower 1/3rd is smooth muscle: maintain sustained slower
contractions of peristalsis, controls entry of food and prevents
acid reflux
Bolus refers to the food stuff that will get swallowed
- Swallowing
Phases:
1. Oral preparatory phase: food manipulated in the mouth and
reduced to swallow
2. Oral transport phase: tongue propels bolus until pharyngeal
swallow reflex is triggered.
3. Pharyngeal phase: bolus transported through pharynx with
coordinated closure of glottis and cessation of breathing and
relaxation of upper esophageal sphincter (UOS)
4. Esophageal phase: peristalsis carries bolus from UOS to LES
(lower).
- Salivary gland diseases
Sjogren’s syndrome: autoimmune, dry mouth and eyes,
associated with rheumatoid arthritis.
Mumps virus: mumps is a viral infection. Swelling of parotid
gland, hence affects serous secretion.
,- Esophagus disease
GORD: gastro-oesophageal reflux disease, caused by stuff like
obesity, hiatal hernia, drugs that lower LOS, pregnancy. Mucosal
damage produced by abnormal acidic reflux in stomach to the
esophagus.
Sliding hernia, more common, occurs at GOJ, cardia of stomach
slides upwards opening into thorax
Rolling hernia, less common, upward movement of gastric
fundus, creates a bubble of stomach into thorax.
Symptoms: heartburn (burning sensation), dysphagia
(inflammation), laryngopharyngeal reflux (also called cough,
hoarseness and chronic earache)
Outcomes of GORD:
1. Esophagitis: inflammation of esophagus due to chronic
exposure to stomach acid, leads to ulceration and bleeding.
Odynophagia
2. Strictures: scar tissue narrowing esophagus . dysphagia
3. Barret’s metaplasia: change in epithelium in response to
environmental stress. Affects secretion and impairs barrier
function. Can lead to cancer (next one)
4. Esophageal adenocarcinoma: affects lower esophagus, closely
linked with metaplasia above.
Diagnosis: 24h pH monitoring, surveillance endoscopy,
cytosponge monitoring
Treatment: stuff like weight loss counts as conservative,
medical counts as drugs and surgical methods like repairing
the hernias or fundoplication/cutting the fundus.
Achalasia: degeneration and reduction of ganglion in LOS
segment, leading to relaxation failure, hard to swallow food
due to impaired esophagus. Medications, surgery (Heller’s
myotomy) and decreasing pressure of LES
, Lecture 3- stomach
- Functions of the stomach
Secretion depending on different cell types
Motility or peristalsis
Digestion or carbohydrates, proteins and fat
Absorption in small amounts
- Contractions
1. Tonic contractions: continuous and sustained contractions,
oral region (upper including the fundus). DOES NOT PUSH
FOOD FORWARD, MAINTAINS PRESSURE WITHIN STOMACH,
controls rate at which bolus is delivered to intestine
2. Phasic contractions: caudad region (lower), peristaltic
movements mix the content within the stomach, helps
physical breakdown of food
- Cell types and secretions
1. Mucous Neck Cells: secrete mucus, which protects the
stomach lining.
2. Parietal Cells: secrete acid and produce HCO3- on their
basolateral side
3. EC-like Cells: secrete histamine that stimulates parietal cells
to produce
4. Chief Cells: release pepsinogen and lipase, secretions
indirectly stimulate G cells to produce gastrin
- Digestion
Conversion of dietary nutrients into a form that the small
intestine can absorb
Starts in the oral cavity, mouth lined by STRATIFIED SQUAMOUS
EPITHELIUM
- Teeth
Primary/deciduous dentitions include 20 teeth, permanent
dentitions include 32
Chewing can also be called mastication. This increases surface to
volume ratio and creates a larger surface area in food.
Decreases food particle size to allow better action of digestive
enzymes for better absorption
- Tongue
Papillae have taste buds which have gustatory cells or taste
receptors. Prepares food for swallowing.
- Saliva
Contains 99.5 percent water, along with electrolytes, salivary
amylase and other enzymes. Has a major role in taste, motility
and cleaning the mouth
Salivary gland:
It is an exocrine gland.
It has a branched ductal system to release secretory products
such as saliva. Secretion can either be serous (watery) or
mucous.
There are 3 glands, innervated by PNS. Parotid (Serous),
sublingual (Mucus) and submandibular (Mixed).
Cells: Acinar cells produce saliva by transporting ions across cell
membranes and goblet cells produce lubrication for hydration
purposes.
Primary saliva produced by acinar cells is isotonic and high
concentrations of Na+ and Cl-. These ions need to be removed to
make final saliva hypotonic. Hypotonic saliva is more effective in
lubricating.
, Goblet cells modify primary saliva by causing reabsorption of the
ions. Na+ through Na+K+ pumps. Cl- would be passively
reabsorbed, HCO3- generated from giblet cells and secreted into
saliva to regular pH.
Saliva is alkaline. This is because it protects against acid,
enzymatic activity, antimicrobial properties, tooth
remineralization and tissue health.
- Esophagus
Muscular tube that connects pharynx to the stomach. Main
secretion is mucus.
Upper 1/3rd is skeletal muscle: swallowing is consciously
controlled, starts peristaltic wave.
Middle 1/3rd is skeletal and smooth muscle: automated
swallowing and less conscious
Lower 1/3rd is smooth muscle: maintain sustained slower
contractions of peristalsis, controls entry of food and prevents
acid reflux
Bolus refers to the food stuff that will get swallowed
- Swallowing
Phases:
1. Oral preparatory phase: food manipulated in the mouth and
reduced to swallow
2. Oral transport phase: tongue propels bolus until pharyngeal
swallow reflex is triggered.
3. Pharyngeal phase: bolus transported through pharynx with
coordinated closure of glottis and cessation of breathing and
relaxation of upper esophageal sphincter (UOS)
4. Esophageal phase: peristalsis carries bolus from UOS to LES
(lower).
- Salivary gland diseases
Sjogren’s syndrome: autoimmune, dry mouth and eyes,
associated with rheumatoid arthritis.
Mumps virus: mumps is a viral infection. Swelling of parotid
gland, hence affects serous secretion.
,- Esophagus disease
GORD: gastro-oesophageal reflux disease, caused by stuff like
obesity, hiatal hernia, drugs that lower LOS, pregnancy. Mucosal
damage produced by abnormal acidic reflux in stomach to the
esophagus.
Sliding hernia, more common, occurs at GOJ, cardia of stomach
slides upwards opening into thorax
Rolling hernia, less common, upward movement of gastric
fundus, creates a bubble of stomach into thorax.
Symptoms: heartburn (burning sensation), dysphagia
(inflammation), laryngopharyngeal reflux (also called cough,
hoarseness and chronic earache)
Outcomes of GORD:
1. Esophagitis: inflammation of esophagus due to chronic
exposure to stomach acid, leads to ulceration and bleeding.
Odynophagia
2. Strictures: scar tissue narrowing esophagus . dysphagia
3. Barret’s metaplasia: change in epithelium in response to
environmental stress. Affects secretion and impairs barrier
function. Can lead to cancer (next one)
4. Esophageal adenocarcinoma: affects lower esophagus, closely
linked with metaplasia above.
Diagnosis: 24h pH monitoring, surveillance endoscopy,
cytosponge monitoring
Treatment: stuff like weight loss counts as conservative,
medical counts as drugs and surgical methods like repairing
the hernias or fundoplication/cutting the fundus.
Achalasia: degeneration and reduction of ganglion in LOS
segment, leading to relaxation failure, hard to swallow food
due to impaired esophagus. Medications, surgery (Heller’s
myotomy) and decreasing pressure of LES
, Lecture 3- stomach
- Functions of the stomach
Secretion depending on different cell types
Motility or peristalsis
Digestion or carbohydrates, proteins and fat
Absorption in small amounts
- Contractions
1. Tonic contractions: continuous and sustained contractions,
oral region (upper including the fundus). DOES NOT PUSH
FOOD FORWARD, MAINTAINS PRESSURE WITHIN STOMACH,
controls rate at which bolus is delivered to intestine
2. Phasic contractions: caudad region (lower), peristaltic
movements mix the content within the stomach, helps
physical breakdown of food
- Cell types and secretions
1. Mucous Neck Cells: secrete mucus, which protects the
stomach lining.
2. Parietal Cells: secrete acid and produce HCO3- on their
basolateral side
3. EC-like Cells: secrete histamine that stimulates parietal cells
to produce
4. Chief Cells: release pepsinogen and lipase, secretions
indirectly stimulate G cells to produce gastrin
