GI 1 Flashcards
1
Q
What are the functions of the alimentary canal?
A
- ingestion: bringing food in
- secretions: lots of secretions along whole length of tube (saliva, enzymes, bile, gastric juices)
- mixing and propulsion: propulsion moves food from mouth towards bottom end, mixing through coordinated contractions of muscles of GI wall which can segment the tube
- digestion: breaking food down by mechanical fashion or chemical fashion (acids and enzymes produced by various organs)
- absorption: taking nutrients that have been broken down and bringing them into bloodstream
- defecation: things that can not be absorbed are excreted
2
Q
What is the function of the gums, teeth, tongue, lips, cheek, hard and soft palate, and uvula in terms of digestion?
A
- gums and cheek keep teeth in place and work to get food into working spaces of teeth to break down food mechanically
- lips close off the oral cavity as you are chewing so food doesn’t fall out
- superior and inferior labial frenulum help to restrict movement of lips
- hard palate part of maxilla covered by mucous membrane
- soft palate contains skeletal muscle to close off nasopharynx to prevent food from entering
- uvula has large density of irritant receptors to get reflex response of emesis (vomiting)
- lingual frenulum restricts backward movement of the tongue
3
Q
Where is the opening to the duct of the submandibular gland located?
A
- under the tongue
- secretes saliva
- stimulate anterior 1/3 of tongue and you will observe saliva under tongue
4
Q
What are the primary tastes?
A
-sweet, bitter, salty, sour, and umami
5
Q
What are the types of papillae?
A
- vallate papillae: 12 each containing 100-300 taste buds
- fungiform papillae: scattered over tongue each containing 5 taste buds
- foliate papillae: in the lateral margins of the tongue; degenerate in childhood
- filiform papillae: tactile sensations and friction (no taste buds)
- approximately 10 000 taste buds
6
Q
What are taste buds made of?
A
- gustatory receptor cells
- specialized epithelial cells
- detect chemical stimuli and release a neurotransmitter signal onto the neuron
- cells are constantly being regenerated
- neuron is deep in the tongue so it is not exposed to the harsh food environment
7
Q
What cranial nerves are involved in gustation?
A
- facial nerve (anterior 2/3)
- glossopharyngeal (posterior 1/3)
- vagus (throat and epiglottis)
- tactile sensations are somatic and travels through mandibular branch of CN5 (trigeminal)
- taste ends up in parietal lobe
8
Q
How does olfaction occur?
A
- specialized epithelial cells that detect chemicals that have become dissolved within mucus lining nasal cavity (superior part on cribriform plate)
- put NTs on cranial nerve 1 and that sensation of smell goes up those neurons to primary olfactory cortex in insular cortex
- does not synapse in the thalamus (lose sense of smell over time with a particular smell because of receptor desensitization, not because thalamus is filtering it out
9
Q
What are the types of teeth and dentitions?
A
- incisors for cutting (4)
- canines for tearing (2)
- premolars for crushing (4)
- molars for grinding (6)
- 32 teeth in total if you have all of them
- deciduous dentition (baby teeth) and permanent dentition
10
Q
A
- enamel is hardest substance in body
- teeth are 95% calcium salts (more than bones)
- dentin is less calcified version of enamel
- pulp in pulp cavity is analagous to bone marrow- supplied by blood vessels and nerves (CN5)
- periodontal ligaments hold teeth in place made up of collagen
- vitamin C needed to make strong collagen so over time, if you don’t have adequate vitamin C in your diet the periodontal ligaments will become weak and teeth will fall out (scurvy)
11
Q
What is mastication?
A
- effort between teeth, tongue, and cheek
- small working space in mouth for grinding down food between teeth
- tongue and cheek put food up there to do mastication
- requires saliva to lubricate it which has enzymes to start chemical digestion
- parotid gland sits just in front of ear, duct releases about level of 2nd molar
- submandibular gland under mandible
- sublingual gland which has several ducts along base of tongue
- partly a reflex action from pattern generators and also have voluntary control
12
Q
A
- both sets of longitudinal muscles contract at the same time and cause shortening of the tongue
- if you were just to contract the upper layer, tongue curls upwards
- transverse muscles contract to make tongue thinner
- if you just contract the upper layer you can make a slide out of it
- vertical muscle contraction flattens tongue out useful for moving tongue around
- all intrinsic muscles of tongue are innervated by CN12
13
Q
A
- styloglossus attached to styloid process and tongue, when contracted tongue elevates in the oral cavity useful when trying to swallow
- hyoglossus attached to hyoid bone and tongue
- genioglossus attached from base of tongue in back to chin, when it contracts it brings it forward in the oral cavity
14
Q
A
- have action on jaw to help close mouth
- temporalis lies over the temporal bone and sends its tendon over the zygomatic arch
- if you clench your jaw, can feel this muscle above the ear
- masseter is main muscle of mastication arising from maxilla down to mandible
- both controlled by CN5
15
Q
A
- innervated by facial nerve
- buccinator muscle contracts to keep food up against cheek when chewing (this one gets sore when blowing up a balloon)
- orbicularis oris acts as sphincter around the lips to keep food in mouth
16
Q
Describe the blood supply to the muscles of mastication
A
- comes from external carotid
- facial artery goes under mandible to supply lower jaw
- maxillary artery supplies structures of upper jaw/nasal cavity
- superficial temporal artery supplies temporalis muscle
- veins are the same names
17
Q
What are the components of secretions from the salivary glands? How are the secretions controlled?
A
- mostly water
- amylase (helps break down complex carbs), mucin (gives saliva stickiness), lysozyme (breaks up bacteria), IgA (protection for mucus membrane), defensins, and electrolytes
- parasympathetic (CN 7 and 9) results in watery enzyme rich saliva
- sympathetic results in thick mucin-rich saliva (mainly sublingual)
18
Q
Describe the saliva from the different types of salivary glands
A
- parotid: only serous (with amylase)
- submandibular: mostly serous (with amylase)
- sublingual: mostly mucous (with lipase)
19
Q
What gland is the target of mumps?
A
- parotid gland
- virus is spread through saliva
- creates pressure in front of ear when it is infected which hurts when you try to smile
20
Q
What are the phases of deglutition?
A
- Voluntary: oral cavity and tongue, consciously move bolus of food toward pharynx where stretch receptors activate pattern generators in brainstem (all skeletal muscle)
- Pharyngeal: as you stretch oropharynx, signals to brainstem that close off nasopharynx by elevating soft palate and elevating larynx/closing epiglottis to protect trachea, upper esophageal sphincter relaxes to allow food through
- Esophageal: peristalsis, proximal 1/3 skeletal and distal 1/3 smooth muscle
21
Q
What are the kinks and hiatus of the esophagus?
A
- as esophagus passes behind trachea it will have a kink
- kink at left atrium
- hiatus through diaphragm
22
Q
Describe the histology of the esophagus
A
- mucosa: nonkeratinized stratified squamous epithelium
- lamina propria: connective tissue that glues endothelium to lower structures and where epithelium gets blood vessels from
- muscularis mucosae: smooth muscle which puts the overlying epithelium into folds
- submucosa
- muscularis: inner circular layer and outer longitudinal layer, forces bolus of food (circular layer contracts to push it down, longitudial contracts in front of bolus to ease its movement)
- adventitia (connective tissue anchoring it to neck)
23
Q
What is the function of the esophagus?
A
- a passage to get food bolus from mouth to the stomach
- no mechanical or chemical digestion
- no absorption of nutrients
- stratified squamous because food bolus provides some friction
24
Q
What occurs during late deglutition?
A
- lower esophageal (gastroesophageal) sphincter keeps acidic content of stomach out of the esophagus
- as food bolus approaches lower esophageal sphincter it momentarily relaxes to allow bolus through
- stomach produces a sticky mucus with a lot of bicarb but the esophagus has no protective mucus layer
25
What causes gastroesophageal reflux disease?
- gastric juices move up into the esophagus
- could be because of low lower esophageal pressure so that it doesn't act like a sphincter
- could have gastric pouch (intra thoracic reservoir) where a portion of the stomach has herniated into the thoracic cage- diaphragm can no longer help gastroesophageal sphincter so it doesn't close as well; hiatal hernia
26
How does GERD present?
- sub sternal chest pain
- many causes but is worsened by alcohol & smoking (cause lower esophageal sphincter to relax), coffee/chocolate/peppermint/stress by virtue of it secreting cortisol which increases amount of acid stomach makes, obesity and pregnancy put pressure on stomach which increases intragastric pressure making it more likely that acid will move up the esophagus
- treatment: smaller meals (less acid produced), upright position after meal, avoid problematic foods, antacids to neutralize acids (bicarb and calcium salt)
