GB 4. Swallowing Flashcards
What is the “bird beak” appearance of the esophagus?
It is when there is narrowing of the esophagus and so, there is difficulty for food and liquids to enter the stomach
What are the 3 purposes/functions of chewing?
[1] lubricates food
[2] mixes food with salivary amylase
[3] mechanically breaks up food
What is another word for chewing?
Mastication
What is Mastication?
another word for chewing
Where does most carbohydrate (sugar) digestion occur?
It occurs in the duodenum due to the presence of pancreatic amylase
What are the 3 glands that produce saliva?
[1] Parotid Glands
[2] Sublingual Glands
[3] Submandibular Glands
What type of saliva is created by the Parotid glands?
a serous, watery secretion containing amylase
What type of saliva is created by the Sublingual glands?
mainly mucous
What type of saliva is created by the Submandibular glands?
mixed serous and mucous, viscous secretion containing mucins
What is another name for the Submandibular glands?
Subaxillary glands
What is another name for the Subaxillary glands?
Submandibular glands
Describe the characteristics and composition of saliva. [6]
[1] Mucins (Glycoproteins) present
[2] alpha-amylase (ptyalin) and lingual lipase
[3] immunoglobulins, lysozymes
- has a protective function
[4] Na+, K+, Ca2+, Mg2+, Cl-, HCO3-, P04 2-
- as the rate of secretion changes, the concentration of ions change
[5] pH 6 to pH 8
- pH optimum for amylase = 7
[6] Hypotonic
- it is a bit watery (compared to blood and other things)
What are the functions of saliva?
[1] facilitates swallowing and speech
[2] solubilizes food for tasting
- saliva presents the fluid to taste buds
[3] starch digestion
[4] oral hygiene (lysozyme, IgA)
[5] buffering
- bicarbonate has an important role in preventing the pH from going too low
What is dysphagia?
difficulty swallowing
What is Xerostomia?
dry mouth
What occurs due to xerostomia?
- dental caries (breakdown of teeth)
- mouth infection
- difficulty with speech
- difficulty with taste
- difficulty swallowing (dysphagia)
What is the difference between efferent and afferent nerves?
Efferent Nerves = motor neurons
Afferent Nerves = sensory neurons
Does parasympathetic stimulation increase or decrease saliva production? Does sympathetic stimulation increase or decrease saliva production?
Parasympathetic = increase saliva production Sympathetic = decrease saliva production
What nerves are involved with parasympathetic stimulation?
Cranial Nerve VII (facial)
Cranial Nerve IX (glossopharyngeal)
Under parasympathetic stimulation, what changes are involved with it?
[1] Increased Secretion of Amylase
[2] Increased Secretion of Mucus
[3] Increased Blood Flow
[4] Increased Growth
Under sympathetic stimulation, what changes are involved with it?
[1] Increased Secretion of Amylase
[2] Increased Secretion of Mucus
[3] Decreased Blood Flow
Why does stress cause xerostomia?
Under stress, the sympathetic nervous system is stimulated - this constricts blood vessels (decreasing blood flow) and leads to decreased secretion of saliva
What is Deglutition?
another word for swallowing
What are the 3 phases of swallowing?
[1] Oral (Voluntary)
[2] Pharyngeal (Reflex)
[3] Esophageal (Reflex)
Name the layers of the general cross section of the gastrointestinal tract from the outside in. [6]
[1] Tunica Serosa [2] Tunica Muscularis Externa [3] Myenteric Plexus [4] Tunica Submucosa [5] Muscularis Mucosae [6] Lamina Propria
How many layers is the Muscularis Externa made up of what are they called?
[1] Longitudinal (outer)
[2] Circular (inner)
Where is the Myenteric (Auerbach’s) Plexus located?
It is located between the muscularis externa layers
Where is the Submucosal (Meissner’s) Plexus located?
It is located below the muscularis externa.
Name the layers of the general cross section of the GIT from inside out.
[1] Mucosa (a) Epithelium (b) Lamina Propria [2] Muscularis Mucosae [3] Submucosa [4] Muscularis Externa (a) Circular Muscle Layer (b) Longitudinal Muscle Layer [5] Serosa
Explain the intrinsic and extrinsic control in the gut wall?
REFER TO SLIDE 16
- there are chemo-, osmo- and mechanoreceptors in the gut wall
- the receptors react in response to the stimulus in the lumen
INTRINSIC:
- receptors feed into intramural plexuses
- intramural plexuses have an effect on the smooth muscle, exocrine cells and endocrine cells
EXTRINSIC:
- receptors send signals to CNS through the afferent nerves
- the CNS controls the sympathetic and parasympathetic efferents to the intramural plexuses
*side note: other inputs (like stress) have an input on the CNS
Where do the sympathetic and parasympathetic nerves typically end?
typically ends on the plexuses, not on the smooth muscles or the glands
What is the pharyngeal phase? (general overview)
- tongue pushes food to back of the throat
- the food enters the pharynx
What are the afferent and efferent nerves involved in the pharyngeal phase?
AFFERENTS:
- cranial nerves 5, 9 and 10
- nerves from pharynx relay to the swallowing centre in the PONS and MEDULLA
EFFERENTS:
- 5, 7, 9, 10 and 12 nerves
What are the events that occur in the pharyngeal phase?
- soft palate is raised
- vocal folds approximate
- larynx is raised
- epiglottis swings back
- upper esophageal sphincter (UES) relaxes
- superior pharyngeal constrictor contracts
- initiates peristaltic wave!
side note: lasts 1 second + breathing inhibited
What type of muscle is involved in swallowing?
striated muscle
What might impair swallowing?
striated muscle involved in swallowing
- conditions which affect striated muscle (e.g. stroke, myasthenia gravis, parkinson’s disease, MS etc….)
What are the events that occur in the esophageal phase?
- UES contracts
- primary peristaltic wave moves to the lES
- secondary peristaltic waves clear the esophagus of food
- controlled by vagal and intrinsic reflexes
What nerves control the esophageal phase?
- controlled by vagal and intrinsic reflexes
Describe the composition of the esophageal wall.
First 1/3:
- striated muscle
Middle 1/3:
- striated + smooth muscle
Last 1/3:
- smooth muscle
What is vomiting (emesis) preceded by?
- nausea
- salivation
- sweating
- pallor
- mydriasis
- irregular heart rate
What are the nerves involved with vomiting? (the afferents and efferents)
- afferents from stomach and duodenum to sympathetics and nerve 10 to VOMITING CENTRE + MEDULLA
- efferents in 5, 7, 9, 10 and 12 nerves
What is the cause of emesis (vomiting)?
- distension of the stomach and duodenum
- motion
- psychic stimuli
- pain
- increased intracranial pressure
- tactile stimulation of the back of the throat
- pregnancy
What are some emetics?
- cytotoxic drugs
- morphine
- uraemia (build up of waste)
- endogenous substances released from radiotherapy, infection or disease
What are the receptors and nerve processes involved in emesis?
- emetics acting on receptors in the stomach/duodenum and on the chemoreceptor trigger zone in the medulla (e.g. the area postrema, part of the circumventricular organ system)
What are the physiological responses to vomiting (emesis)?
- antiperistalsis in small intestine
- relaxation of pylorus and stomach
- muller’s manoeuvre
- elevation of larynx
- elevation of soft palate
- contraction of abdominal muscles
- relaxation of LES, esophagus and UES
*side note: the contraction of diaphragm and abdominal muscles squish the relaxed stomach
What is Muller’s Manoeuvre?
it is forced inspiration against the closed epiglottis
- this leads to negative pressure in the body since not really breathing in
