Digestive System I

Question 1

Oral cavity

Answer 1

• lined by stratified squamous epithelium

- lined by a mucous membrane

Question 2

What keeps the mucous membrane moist?

Answer 2

secretion of glands and/or epithelial cells

Question 3

Lips

Answer 3

• mucocutaneous junction and forms the entrance to the oral cavity
• covered by thick stratified squamous epithelium

Question 4

What makes up the long papillae of the lips?

Answer 4

underlying lamina propria/submucosa form long papillae that extend into the thick epithelial layer

Question 5

Palate

Answer 5

forms the dorsal wall of the oral cavity and is divided into hard and soft parts

Question 6

Hard palate

Answer 6

• mucous membrane over bone with rostral transverse ridges

- submucosa continuous with the periosteum of the bones

Question 7

Dental pad

Answer 7

• located in the rostral part of the hard palate in ruminants and replaces the upper incisors
• has a thick stratum corneum to withstand mechanical stress applied by the lower incisors

Question 8

Soft palate

Answer 8

• located caudal to hard palate and consists of mucous membrane covering skeletal muscles
• may contain lymphatic nodules
• transition to respiratory epithelium occurs on the dorsal surface of the soft palate

Question 9

Buccal wall

Answer 9

• located deep to the facial muscles
• contains minor salivary glands
• contains openings of ducts from major salivary glands

Question 10

Tongue

Answer 10

• mucous membrane sack filled with skeletal muscles

- functions in mastication, swallowing, and grooming

Question 11

Epithelial papillae of tongue and oral cavity are classified as what 2 things?

Answer 11

mechanical functions (keratinized)
gustatory function (contains taste buds)

Question 12

Filiform papillae

Answer 12

• most numerous
• found throughout the dorsal surface of rostral 2/3 of tongue
• apical processes are keratinized, point caudally
• important for grooming and grasping food

Question 13

Conical papillae

Answer 13

• located on root of tongue and cheek inner surface

- large with keratinized epithelium and large CT core

Question 14

Lenticular papillae

Answer 14

• large, grossly visible, lentil shaped, and keratinized

- found on dorsal prominence of tongue in ruminants

Question 15

Fungiform papillae

Answer 15

• scattered on rostral dorsal surface of tongue
• may be keratinized in herbivores
• taste buds found on dorsal surface in carnivores, lateral surface in herbivores

Question 16

Vallate papillae

Answer 16

• arranged in V at rostral border of the root of tongue
• each papilla surrounded by a depression called a moat
• taste buds located on lateral surface and open in moat

Question 17

Foliate papillae

Answer 17

• found in row at lateral margin of tongue
• leaf-like, separated by furrows
• numerous taste buds may be located on their lateral surface

Question 18

Gustatory glands

Answer 18

• serous secreting w/ ducts opening into the moat around vallate papillae or furrows between foliate papillae
• secretions function as medium through which chemicals diffuse to taste buds

Question 19

What is taste?

Answer 19

chemosensation

Question 20

Taste buds

Answer 20

• located on fungiform, vallate, and foliate papillae as well as epiglottis and soft palate
• comprised of oval clusters of columnar cells located within the epithelium and extending through its thickness

Question 21

Taste pore

Answer 21

opens into the oral cavity

Question 22

Name the 2 types of columnar cells within a taste bud

Answer 22

sensory (neuroepithelial) cells

supportive (sustentacular) cells

Question 23

Sensory cells

Answer 23

• taste receptors on apical processes
• basal synaptic vesicles
• nerve contacts

Question 24

Sustentacular cells

Answer 24

• apical microvilli
• higher levels of L-type Ca2+ channels
• needed for nerve impulse generation

Question 25

What influences tastant sensitivity?

Answer 25

interactions beween sensory cells

Question 26

How are basal cells related to taste buds?

Answer 26

basal cells divide every few days to replace the columnar cells of a taste bud

Question 27

Taste sensation

Answer 27

- sensory cells express specialized receptors that are responsible for the various modalities of taste - a single taste cell may respond to multiple taste modalities

Question 28

Name the 5 taste modalities

Answer 28

``` sweet umami bitter salt sour ```

Question 29

What is the ligand for sweet?

Answer 29

mono/di/poly-saccharides, sweeteners | cats have T1R2 deletion, can't taste sweet

Question 30

What is the ligand for umami?

Answer 30

amino acids | mostly glutamate in humans, all amino acids in mice

Question 31

What is the ligand for bitter?

Answer 31

vegetable alkyloids, quinine, etc. | T2$ receptors found in gastric and duodenal enteroendocrine cells

Question 32

What is the ligand for salt?

Answer 32

sodium ions, others

Question 33

What is the ligand for sour?

Answer 33

organic acids - e.g. citric, malic

Question 34

How are teeth classified?

Answer 34

according to the type of growth | according to the period of function

Question 35

Brachydont (short tooth)

Answer 35

- finite growth period - limited period of eruption - found in man, carnivores, pig, and ruminant (incisors)

Question 36

Hypsodont teeth

Answer 36

- continuously erupting | - continuously emerging through the gingivia

Question 37

Deciduous teeth

Answer 37

first teeth to erupt, then root is resorbed by osteoclast and replaced by adult dentition

Question 38

Permanent teeth

Answer 38

last throughout adult life

Question 39

Crown

Answer 39

- part of tooth distal to neck - clinical clown is part exposed through gingiva - composed of layers of enamel over dentin

Question 40

Gingiva

Answer 40

- gum | - anchored to enamel

Question 41

Root

Answer 41

- anchored in a bony alveolus of the jaw | - composed of the mineralized dentin covered by cementin

Question 42

Pulp cavity

Answer 42

-located in center of tooth and contains nerves, vascular supply, fibroblasts, and collagen fibers

Question 43

Periodontal ligament

Answer 43

- consists of perforating fibers anchored in both the bony alveolus of jaw and cementum of root - shock absorber, holds tooth in place

Question 44

Name the 3 mineralized tissues in teeth

Answer 44

enamel dentin cementum

Question 45

Enamel (4)

Answer 45

- formed by ameloblasts - hardest part of tooth - composed of acellular organic matrix and hydroxyapatite - enamel does not form after eruption of tooth

Question 46

Dentin (4)

Answer 46

- produced by odontoblasts - harder than bone - composed of collagen and hydroxyapatite - formed throughout life and produced in response to injury

Question 47

Cementum (3)

Answer 47

- produced by cementoblasts - like bone in structure and composition - cemetocytes located in lacunae within the cementum

Question 48

Name the 5 things involved in brachydont tooth development

Answer 48

``` enamel organ inner enamel epithelium outer enamel epithelium stellate reticulum epithelial root sheath ```

Question 49

Dental papilla

Answer 49

- condensation of mesenchyme | - layer of dental papilla cells adjacent to ameloblasts differentiates into odontoblasts that form dentin of crown

Question 50

Dental sac

Answer 50

- condensation of CT that forms around entire developing tooth - gives rise to the cementoblasts of the root, the periodontal ligament, and the alveolar bone

Question 51

Eruption

Answer 51

- process of tooth emergence through the gingiva | - root formation is complete after eruption

Question 52

Structure of hypsodont teeth

Answer 52

- body has no distinct neck or crown - entire tooth covered by cementum - root confined to short area w/ no enamel - enamel crests are ridges formed on occlusal surface

Question 53

Development of hypsodont teeth

Answer 53

- enamel organ collapses before tooth eruption | - in continuously growing teeth, enamel, dentin, and cementum formation continues for life of tooth