Digestive system-2

Question 1

What is the oral cavity bounded by? what are the key associated organs?

Answer 1

bounded by lips, cheeks, palate and tongue

the tongue, the salivary glands and the teeth

Question 2

What are the 5 key components of the mouth?

Answer 2

o Lips (labia): composed of fleshy orbicularis oris muscle
o Oral vestibule: recess internal to lips and cheeks, external to teeth and gums
o Cheeks: composed of buccinator muscles
o Oral cavity proper: lies within teeth and gums
o Labial frenulum: median attachment of each lip to gum

Question 3

What is the difference between the hard and soft palate?

Answer 3

Hard palate:

• palatine bones and palatine processes of the maxillae
• Slightly corrugated(bumpy) to help create friction against the tongue

Soft palate:
-fold formed mostly
of skeletal muscle
-closes off the nasopharynx during swallowing
-Uvula projects downward from its free edge

Question 4

What are the 3 functions of the tongue? what are the 2 types of muscles in the tongue and what do they do? What is the lingual frenulum of the tongue?

Answer 4

o Repositioning and mixing food during chewing
o Formation of the bolus
o Initiation of swallowing, speech, and taste

o Intrinsic muscles change the shape of the tongue
o Extrinsic muscles alter the tongue’s position

Lingual frenulum: attachment to the floor of the
mouth

Question 5

What is ankyloglossia?

Answer 5

congenital condition in which children are born with an extremely short lingual frenulum referred to as “tonguetied” or “fused tongue”

Question 6

What are the 2 parts of the tongue that are divided by the terminal sulcus?

Answer 6

▪ Body: anterior 2/3 residing in the oral cavity

▪ Root: posterior third residing in the oropharynx

Question 7

What are the 4 parts of the surface papillae of the tongue? Which parts sense taste? What are the 5 taste sensations?

Answer 7

Surface papillae (projections of lamina propria covered with epithelium):
1. Foliate—on the lateral aspects of the posterior
tongue
2. Filiform—whitish, give the tongue roughness
and provide friction
3. Fungiform—reddish, scattered over the
tongue
4. Circumvallate (vallate)—V-shaped row in
back of tongue

Circumvallate, foliate and fungiform papilla contain taste buds

salty, sour, bitter, sweet & Umami (savory)

Question 8

What are the 4 functions of the saliva?

Answer 8

▪ Cleanses mouth
▪ Dissolves food chemicals for taste
▪ Moistens food; compacts into bolus
▪ Begins breakdown of starch with enzyme amylase

Question 9

What are the 2 types of secretory cells in the salivary glands and what do they produce?

Answer 9

▪ Serous cells: produce watery secretion, enzymes, ions, bit of mucin
▪ Mucous cells: produce mucus

Question 10

What are the names of the extrinsic salivary glands? how much saliva each of them produce? what is the name of the intrinsic salivary glands?

Answer 10

Extrinsic:
Parotid(25%)
Sublingual(70%)
Submandibular(5%)

Intrinsic:
Buccal

Question 11

How much saliva is produced per day in ml? Which section of nervous system activates the salivary glands? what are examples of other stimuli for salivary glands? what causes dry mouth?

Answer 11

1500ml/day

peripheral nervous system

irritating foods, nausea

strong sympathetic stimulation which inhibits salivation

Question 12

What is mastication? What is the difference between the crown and the root? What are the 4 major types of teeth?

Answer 12

▪ Mastication: process of chewing that tears
and grinds food into smaller fragments

• Crown: exposed part above gingiva (gum)
• Root: portion embedded in jawbone
– Connected to crown by neck

▪ Incisors: chisel shaped for cutting
▪ Canines: fanglike teeth that tear or pierce
▪ Premolars (bicuspids): broad crowns with rounded cusps used
to grind or crush
▪ Molars: broad crowns, rounded cusps: best grinders

Question 13

What are the 2 processes involved in mastication? what does it produce?

Answer 13

▪ Mechanical
– Closed lips and cheeks
– Teeth
– Tongue

▪ Chemical(enzymatic)
• breakdown of starch by salivary amylase
• breaking of fats by lingual lipase (in the stomach but
with the enzyme produced in the mouth)

Production of bolus (lump) easy to swallow

Question 14

What are 4 key characteristics of the pharynx?

Answer 14

o Allow passage of food, fluids, and air
o Food passes from mouth into oropharynx and then into laryngopharynx
o SSE lining with mucus-producing glands
o External muscle layers consists of two skeletal muscle layers
• Inner layer of muscles runs longitudinally
• Outer pharyngeal constrictors encircle wall of pharynx

Question 15

What are 4 key characteristics of the esophagus? what dpes lower esophageal sphincter do?

Answer 15

▪ Flat muscular tube (~25 cm) that runs from laryngopharynx to stomach
▪ collapsed when not involved in food propulsion
▪ pierces diaphragm at esophageal hiatus
▪ joins stomach at cardial orifice

▪ Gastroesophageal (cardiac) sphincter (lower esophageal sphincter) surrounds cardial orifice
• Keeps orifice closed when food is not being swallowed
• Mucus cells on both sides of sphincter help protect esophagus from acid reflux

Question 16

What are the 4 layers of the esophagus?

Answer 16

o Esophageal mucosa contains SSE that changes to simple columnar epithelium at the stomach
o Esophageal glands in submucosa secrete mucus to aid in bolus movement
o Muscularis externa: skeletal muscle superiorly; mixed in middle; smooth muscle inferiorly
o Has adventitia instead of serosa

Question 17

What is the main function of the pharynx and esophagus? What are the 2 phases of swallowing(degluttion)? What is the passage of food regulated by?

Answer 17

▪ Pharynx & esophagus: passage of food from mouth to stomach
▪ Major function of both organs is propulsion that starts with deglutition
(swallowing)

• Buccal phase
o Voluntary contraction of the tongue
• Pharyngeal - esophageal phase
o Involuntary
o Control swallowing center in the medulla & lower pons

The passage of food is regulated by:
▪ Two sphincters: upper esophageal and lower esophageal
▪ Peristalsis: (involuntary muscle movements controlled by medulla oblongata) & facilitated by mucus produced by the submucosal glands

Question 18

What are the 5 phases of swallowing?

Answer 18

1. buccal phase
2. start of pharyngeal-esophageal phase
3. end of pharyngeal-esophageal phase
4. persitalsis moves food through esophagus
5. gastroesophageal sphincter opens and food enters stomach