2 - Chewing, Swallowing, GI Secretions PPT Flashcards
Getting a taste and perhaps a hint of an aroma
What is the first step to process food for digestion and absorption?
Chewing
What does chewing food do for our GI tract?
- Decreases food size
- Lubricates food with saliva
- Forms BOLUS through mastication of teeth
What’s the first line of defense in the GI tract?
Epithelial cells
What nervous system division controls saliva secretion?
Parasympathetic
Which cranial nerves control the salivary glands (submandibular, sublingual, parotid)?
CN 7 (Facial) controls the submandibular and sublingual
CN 9 (Glossopharyngeal) controls the parotid
What is saliva composed of?
- Mostly water
- Salivary amylase to break down starch & carbs
- Sodium bicarbonate (BASIC) to maintain pH
Which muscles move the TMJ to chew?
- Temporalis
- Masseter
- Medial Pterygoid
- Lateral Pterygoid
Idea: Remember “TaMMaLe” because you chew those 🧠
Which cranial nerve innervates all four chewing muscles?
CN 5 (Trigeminal)
What two receptor types detect food once it enters the GI tract?
- Mechanoreceptors
- Chemoreceptors
Information is taken up by mechano/chemoreceptors and is set to the…
… Salivatory Nuclei in the brainstem
Saliva production is increased thanks to this information. Which two cranial nerves deliver the command to the saliva glands?
CN 7 (Facial) and CN 9 (Glossopharyngeal)
What’s the fancy shmancy scientific term for swallowing?
Deglutition
What are the three phases of swallowing?
- Oral Phase
- Pharyngeal Phase
- Esophageal Phase
“OPE” kinda sounds like “gulp” to remember the phases of swallowing
Which of these three swallowing phases is the ONLY VOLUNTARY phase?
Oral Phase
Which of the three swallowing phases takes place within the mouth?
Oral Phase
Which of the three swallowing phases takes place within the pharynx and upper esophagus?
Pharyngeal Phase
Is the Pharyngeal Phase voluntary or involuntary?
Involuntary (gotta commit now bruh)
Once receptors sense the food in the Pharyngeal Phase, where is afferent information sent?
The Swallowing Center in the Medulla
Efferent information sent back from the Swallowing Center stimulates what in the pharynx?
Muscle contraction
Muscle contraction during the Pharyngeal Phase involves which structures, and what are their actions?
Soft palate and uvula: they move upwards
Epiglottis: moves down to cover larynx
Upper Esophageal: relaxes to allow the BOLUS to slip through
Epiglottis: moves back up, uncovering larynx
When does the Esophageal Phase begin?
Begins when esophageal sphincter closes to prevent reflux
Is the Esophageal Phase voluntary or involuntary?
Involuntary
Peristalsis begins in the…
… esophagus
The goal of peristalsis in the esophagus is to…
… squeeze the BOLUS down
Which cranial nerve controls peristalsis in the esophagus?
CN 10 (Vagus)
The Esophageal Phase begins in the esophagus, when does it end?
Ends when the lower esophageal sphincter relaxes and allows food to enter the stomach
What happens when food remains in the esophagus?
The myenteric plexus triggers a peristaltic wave to push it into the stomach
Once more, which of the three swallowing phases is the ONLY voluntary phase?
The oral phase is the ONLY voluntary phase
Why does food still go down your esophagus even if you were doing a handstand?
The esophagus is located within the thorax which has a higher pressure than the abdominal region. The pressure change causes the food to be pushed and pulled to the lower pressure area (the stomach).
Which two sphincters work to preserve the pressure gradient by preventing air from getting into the digestive tract?
Upper and Lower Esophageal Sphincters
Which of the two aforementioned esophageal sphincters prevents stomach acids from entering the esophagus?
The Lower Esophageal Sphincter
What conditions lead to an increase in intraabdominal pressure?
Pregnancy and morbid obesity
Increased intraabdominal pressure (IAP) can lead to GERD. What in the worlt is GERD?
GERD is gastroesophageal reflux disease! It means your stomach acid is able to enter and irritate the esophagus and its lining.
Which GI secretion is an overall INHIBITORY hormone?
Somatostatin
What is the multifaceted function of somatostatin?
It DECREASES and INHIBITS:
- Decreases secretions of other hormones
- Slows gastric emptying time
- Decreases pancreatic secretions
- Decreases visceral blood flow
Where is somatostatin secreted from?
D cells (within stomach)
What’s the role of the hormone Gastrin, a GI secretion?
It induces gastric acid secretions after being released due to stimulation by acidic content, food, and vagus nerve stimulation!
From where is Gastrin secreted?
It is secreted from G cells in the stomach and duodenum (2 locations)
(TRUE/FALSE): Gastrin is inhibited by Somatostatin.
(TRUE): Gastrin is indeed inhibited by Somatostatin.
Motilin is a hormone secreted within the GI tract. What is its purpose?
It functions to stimulate gastric and pancreatic enzyme secretion, increase gastric emptying, and IMPORTANTLY, stimulates GI tract motility.
Idea: Say “Motilinty” (mo-till-in-tee, tongue twister) to combine the name of the secretion with its primary purpose.
Where is Motilin secreted from?
M cells (of proximal small intestine)
Idea: Dial M for Motilin
What stimulates the release of Motilin?
Gastric distention and duodenal alkalinization
Jamie pull up real quick what Secretin does and where it’s secreted from.
It says it increases the pH of the duodenum and increases bicarbonate, and it’s secreted by S cells in the small intestine. Wild.
What is the function of Cholecystokinin (CCK)?
It functions to slow gastric emptying, increases gallbladder contraction, and increases pancreatic enzyme secretion.
Where is Cholecystokinin (CCK) secreted from?
I Cells (of small intestine)
(iCell lol)
What stimulates the release of Cholecystokinin (CCK)?
- Nutrient ingestion
- Presence of fatty acids
- Presence of amino acids
All 3 stimulate the release of CCK
What is the role of insulin within the GI tract?
- decreases blood glucose
- promotes glycogen storage
- promotes lipid storage in adipose
(TRUE/FALSE): Insulin is an anabolic hormone.
(TRUE): Insulin is definitely an anabolic hormone, it promotes protein synthesis and allows the uptake of glucose for your muscles.
(Just know that insulin is anabolic as that fact alone is found on the slides.)
Where can we find insulin secretions taking place?
Beta cells of pancreatic islet cells
What stimulus does the body detect that makes it secrete insulin?
High blood glucose
Glucagon is essentially the enemy of insulin. What is its function?
Glucagon counteracts insulin and increases blood glucose.
What cells secrete glucagon?
Alpha cells of pancreatic islet cells
Histamine’s got me all choked up… what does histamine do once activated by parietal cells?
It releases HCL into the stomach
Where is histamine secreted?
From the stomach mucosa
Vasoactive Intestinal Peptide understandably goes by its short abbreviation of “VIP”. What is its purpose?
VIP dilates intestinal capillaries, increases secretions, and relaxes the smooth muscle of the GI.
What is Vasoactive Intestinal Peptide (VIP) stimulated by?
VIP is stimulated by parasympathetic ganglia.
Ghrelin and Leptin have inverse function. What is the function of Ghrelin?
- Stimulates HUNGER
- Acts on the hypothalamus
Where is Ghrelin secreted from and what stimulates its secretion?
Gastric cells after the stomach realizes it is empty
What inhibits Ghrelin?
Ghrelin is inhibited by the stomach stretching when it is full
Leptin is the opposite of Ghrelin. What is its purpose?
- Stimulates SATIETY (fullness)
- Acts on the hypothalamus
Where is Leptin secreted from?
Adipocytes
What stimulates and inhibits Leptin?
Stimulated by a full stomach, inhibited by an empty stomach
