40 Questions
What is the characteristic of the filiform type of papillae?
Pointed and heavily keratinized
What is the function of the basal cells in the taste buds?
They regenerate the sensory and supporting cells
What is the name of the type of epithelium that covers the papillae?
Stratified squamous epithelium
Where are the taste buds found in the tongue?
In the fungiform, circumvallate and foliate papillae
What is the shape of the taste buds in histological sections?
Ovoid
What is the function of the microvilli in the sensory cells?
They contain the receptors for the basic taste modalities
What is the location of the small salivary glands in the tongue?
In the connective tissue of the tongue
What is the number of cells typically found in a taste bud?
50-75 cells
What is the shape of fungiform papillae?
Mushroom-shaped
What is the number of circumvallate papillae in humans?
Between 8 and 12
Where are the taste buds located on the circumvallate papillae?
On the lateral surfaces of the papillae
What is the function of the serous glands opening into the trenches surrounding the circumvallate papillae?
To flush the cleft, renewing the fluid in contact with the taste buds
What is the characteristic of the surface of the tongue where the circumvallate papillae occur?
Depressions of the surface
What is the characteristic of the foliate papillae in adults?
Poorly developed
What is the distribution of the taste buds on the fungiform papillae?
Scattered on their upper surfaces
What is the characteristic of the micrograph of a circumvallate papilla?
Many taste buds around the sides and several small salivary glands
What type of epithelium covers the soft palate, lips, cheeks, and the floor of the mouth?
Nonkeratinized squamous epithelium
What is found in the submucosa of the soft palate?
Diffuse small salivary glands
What is the function of the filiform papillae on the tongue?
To provide a rough surface for food movement
What is the shape of the filiform papillae on the tongue?
Conical
What is the epithelium of the filiform papillae on the tongue?
Keratinized
What is the characteristic of the tongue's dorsal surface?
It is irregular and has many small eminences called papillae
What is the boundary between the anterior two-thirds and the posterior one-third of the tongue's dorsal surface?
The terminal sulcus
What is found on the surface of the root of the tongue?
Lingual tonsils
What type of muscle cells are found in the muscularis layer of the digestive tract?
Smooth muscle cells
What is the main function of the epithelial lining of the digestive tract?
To provide a selectively permeable barrier between the contents of the tract and the tissues of the body
What type of epithelium lines the oral cavity?
Stratified squamous epithelium
What type of muscle fibers are found in the middle third of the oesophagus?
A combination of skeletal and smooth muscle fibers
What is the function of the keratin layer in the oral cavity?
To protect the oral mucosa from damage during masticatory function
What type of muscle fibers are found in the distal third of the oesophagus?
Only smooth muscle fibers
What is the outermost layer of the digestive tract?
Serosa/Adventitia
What type of tissue covers the oesophagus in the peritoneal cavity?
Serosa
What is the function of the arrangement of the oesophageal mucosa?
To allow marked distension during the passage of a food bolus
What is the function of the lamina propria in the oral cavity?
To support the epithelial layer
What is the function of mucosa in the digestive tract?
To provide a selectively permeable barrier between the contents of the tract and the tissues of the body
What type of epithelium lines the lumen of the oesophagus?
Stratified squamous epithelium
What is the function of the submucosa in the digestive tract?
To support the mucosa
What is the function of the seromucous glands in the submucosa?
To aid lubrication during the passage of a food bolus
What is the arrangement of the muscularis propria in the oesophagus?
Inner circular and outer longitudinal layers of smooth muscle
Why are bundles of skeletal muscle present in the upper third of the oesophagus?
Because the first part of swallowing is under voluntary control
Study Notes
Digestive Tract
- The digestive tract has four layers: mucosa, muscularis, submucosa, and serosa/adventitia
- Mucosa supports the mucosa, composed of epithelium, lamina propria, and muscularis mucosae
- Muscularis is thick and composed of smooth muscle cells, divided into two sublayers: internal (circular) and external (longitudinal)
- Serosa/Adventitia is a thin outer layer of loose connective tissue, rich in blood vessels, lymphatics, and adipose tissue
Functions of the Epithelial Lining
- Provides a selectively permeable barrier between the contents of the tract and the tissues of the body
- Facilitates the transport and digestion of food
- Promotes the absorption of the products of digestion
- Produces hormones that affect the activity of the digestive system
- Produces mucus for lubrication and protection
Oral Cavity
- The oral cavity is lined with stratified squamous epithelium, which is keratinized or nonkeratinized depending on the region
- The keratin layer protects the oral mucosa from damage during masticatory function and is best developed on the gingiva and hard palate
- The lamina propria in these regions has many papillae and rests directly on bony tissue
Tongue
- The tongue is a mass of striated muscle covered by a mucous membrane whose structure varies according to the region
- The muscle fibers cross one another in three planes and are grouped in bundles separated by connective tissue
- The tongue's dorsal surface is irregular, covered anteriorly by small eminences called papillae
Papillae of Tongue
- Filiform papillae: smallest and most numerous, conical shape, epithelium does not contain taste buds and is keratinized
- Fungiform papillae: less numerous, lightly keratinized, mushroom-shaped with connective tissue cores and scattered taste buds on their upper surfaces
- Circumvallate papillae: largest and least numerous, occur in depressions of the surface of the tongue, surrounded by a trench formed by the infolding of the epithelium
- Foliate papillae: poorly developed in adults, consist of parallel ridges and furrows on the sides of the tongue, contain many taste buds
Taste Buds
- Taste buds are ovoid/onion-shaped structures containing 50-75 cells, resting in the basal lamina
- Taste buds are most numerous in the fungiform, circumvallate, and foliate papillae
- In addition, taste buds are found in the palate, palatoglossal and palatopharyngeal arches, and in the pharynx and larynx
- Taste buds contain sensory cells, supporting cells, and basal cells
- Sensory cells extend microvilli into the taste pore, which contain the receptors for the different basic taste modalities
Learn about the mucosa, muscularis, and serosa/adventitia layers in Wheater's functional histology. Understand their composition, structure, and functions.
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