Histology Upper respiratory and upper digestive tract

Question 1

What type of epithelium is the olfactory epithelium, and where is it located?

Answer 1

A: The olfactory epithelium is a pseudostratified columnar epithelium located in the olfactory segment of the nasal cavity.

Question 2

Q: What are the four types of cells found in the olfactory epithelium?

Answer 2

Olfactory receptor cells (bipolar neurons) - Detect smell.
Sustentacular cells (columnar epithelial cells with microvilli) - Provide physical support and secrete odorant-binding proteins.
Brush cells (columnar epithelial cells) - Involved in sensation.
Basal stem cells - Small, round cells that can differentiate into other cell types.

Question 3

Q: What is the function and structure of olfactory receptor cells?

Answer 3

A: Olfactory receptor cells are bipolar neurons responsible for detecting odors. They have an apical dendrite with cilia (~20 per cell, 200 μm long) that extends into the nasal cavity, and a basal axonal process that forms part of the olfactory nerve (Cranial Nerve I).

Question 4

Q: What is the role of sustentacular cells in the olfactory epithelium?

Answer 4

A: Sustentacular cells provide physical support to the olfactory receptor cells and secrete odorant-binding proteins. They are columnar epithelial cells with microvilli and have nuclei located in the apical portion of the epithelium.

Question 5

Q: What is the function of brush cells in the olfactory epithelium?

Answer 5

A: Brush cells are involved in sensory transduction, particularly related to general sensation. They are columnar epithelial cells with microvilli, with nuclei located basally, and they form synapses with axons from the trigeminal nerve (Cranial Nerve V).

Question 6

Q: What is the significance of basal cells in the olfactory epithelium?

Answer 6

A: Basal cells are small, round stem cells that reside at the base of the olfactory epithelium. They are essential for regenerating the different cell types within the epithelium, including olfactory receptor neurons.

Question 7

Q: What is the lamina propria, and what does it contain?

Answer 7

A: The lamina propria is a layer of loose connective tissue beneath the olfactory epithelium. It contains blood vessels, sero-mucous glands (Bowman’s glands), and the olfactory nerves.

Question 8

Q: How can you identify the different cell types in the olfactory epithelium based on the location of their nuclei?

Answer 8

A:

Sustentacular cell nuclei: Located at the apical (top) region.
Olfactory receptor cell nuclei: Found in the middle layer.
Basal cell nuclei: Located at the base (bottom) of the epithelium.

Question 9

Q: What is the function of the glands in the olfactory epithelium?

Answer 9

A: The sero-mucous glands, also known as Bowman’s glands, secrete mucus that helps dissolve odorants so they can be detected by olfactory receptor neurons.

Question 10

Q: What are the three types of mucosa found in the oral cavity, and where are they located?

Answer 10

A:

Masticatory Mucosa: Gingiva (gums) and hard palate, lined with keratinized stratified squamous epithelium and lamina propria.
Lining Mucosa: Cheeks, lips, mouth floor, inferior tongue surface, and soft palate, lined with non-keratinized stratified squamous epithelium and lamina propria.
Specialized Mucosa: Dorsal surface of the tongue, lined with stratified squamous epithelium with papillae and taste buds, plus lamina propria.

Question 11

Q: What are the characteristics of masticatory mucosa, and where is it found?

Answer 11

A: Masticatory mucosa is found in the gingiva (gums) and hard palate. It is lined with keratinized stratified squamous epithelium and lamina propria, containing anucleate cells at the surface and papillae with blood vessels. The lamina propria has more collagen fibers, providing strength for mastication.

Question 12

Q: Describe the structure of the lining mucosa in the oral cavity.

Answer 12

A: The lining mucosa is composed of non-keratinized stratified squamous epithelium with multiple cell layers, including nucleated squamous cells and basal cuboidal stem cells. The underlying lamina propria is a loose connective tissue layer.

Question 13

Q: What are the different types of papillae found on the tongue?

Answer 13

A:

Filiform Papillae: Most common, wave-shaped, covered by stratified squamous epithelium, no taste buds.
Fungiform Papillae: Mushroom-shaped, fewer in number, contain taste buds.
Foliate Papillae: Located on the lateral edges of the tongue, contain taste buds on their lateral walls, with glands opening at the base.
Circumvallate Papillae: Large, located at the back of the tongue, surrounded by a trench, contain numerous taste buds.

Question 13

Q: What are the components of a taste bud?

Answer 13

A: Taste buds consist of basal cells, columnar epithelial cells (support or sensory), and axonal branches of Cranial Nerve VII (Facial Nerve).

Question 13

Q: What is specialized mucosa, and where is it located on the tongue?

Answer 13

A: Specialized mucosa is found on the dorsal surface of the tongue. It is lined with stratified squamous epithelium that contains papillae and taste buds, supported by lamina propria.

Question 14

Q: What is the difference between exocrine and endocrine glands?

Answer 14

A:

Exocrine Glands: Secrete products onto surfaces via ducts. Examples include mucous, serous, sweat, oil, and milk glands.
Endocrine Glands: Secrete products into blood vessels or connective tissue without ducts. Examples include hormone and neurotransmitter-secreting glands.

Question 15

Q: What is the main difference between keratinized and non-keratinized stratified squamous epithelium?

Answer 15

A:

Keratinized Epithelium: Found in areas like the gingiva and hard palate, has a layer of anucleate (dead) cells filled with keratin for protection.
Non-Keratinized Epithelium: Found in areas like the cheeks and soft palate, lacks the keratin layer, and cells retain their nuclei, making it more flexible and less resistant to abrasion.

Question 16

Q: What is the merocrine or eccrine mechanism of secretion?

Answer 16

A: Merocrine (or eccrine) secretion involves the release of products by exocytosis, where secretory vesicles fuse with the plasma membrane, releasing their contents without losing any part of the cell. This mechanism is common in salivary glands.

Question 17

Q: How does apocrine secretion differ from merocrine secretion?

Answer 17

A: In apocrine secretion, the apical portion of the cell membrane buds off with the secretory product, resulting in the loss of some cytoplasm. This mechanism is seen in certain sweat glands and mammary glands.

Question 18

Q: What are the key differences between endocrine and paracrine secretion?

Answer 18

A:

Endocrine Secretion: Hormones are released into the bloodstream and travel to target cells. Glands lack ducts.
Paracrine Secretion: Signaling molecules diffuse through the extracellular space to affect nearby target cells, without entering the bloodstream.

Question 19

Q: What are goblet cells, and where are they found?

Answer 19

A: Goblet cells are unicellular glands found within the epithelium. They secrete mucus to lubricate and protect the surface of mucous membranes, such as in the respiratory and digestive tracts.

Question 20

Q: What are the structural classifications of glands?

Answer 20

A:

Tubular Glands: Secretory cells arranged in tube-like structures.
Acinar (Alveolar) Glands: Secretory cells form a cluster around a central duct, resembling a raspberry.
Compound Glands: Complex branched structures with multiple tubular or acinar secretory units

Question 21

Q: What characterizes an acinar gland, and what are its two main types?

Answer 21

A: Acinar glands consist of clusters of secretory cells arranged around a central duct. They can be:

Serous Acini: Secrete watery, enzyme-rich fluid.
Mucous Acini: Secrete viscous, mucous-rich fluid.
Mixed Acini: Contain both serous and mucous cells.

Question 22

Q: Describe the structure of salivary glands.

Answer 22

A: Salivary glands are surrounded by a dense connective tissue capsule. Inside, septa (extensions of the capsule) divide the gland into lobes and lobules. The septa also contain large blood vessels and excretory ducts.

Question 23

Q: What is the role of ducts in salivary glands, and how are they structured?

Answer 23

A: Ducts in salivary glands are lined with simple cuboidal to columnar epithelium. They modify secretions as they pass through and may have basal plasma membrane infoldings (striations) to assist in this process.

Question 24

Q: What are the characteristics of serous secretory cells?

Answer 24

A: Serous secretory cells have a pyramidal shape with prominent Golgi apparatus and rough endoplasmic reticulum (rER). The apical portion of the cell contains granules that are inactive enzyme precursors. The “demilune” appearance in mixed glands is an artifact of fixation.

Question 25

Q: What are the key features of mucous secretory cells?

Answer 25

A: Mucous secretory cells store mucus in granules located in the apical cytoplasm. In H&E stained sections, these cells appear empty or clear due to the loss of mucus during the staining process.

Question 26

Q: What is the role of myoepithelial cells in glands?

Answer 26

A: Myoepithelial cells are contractile cells that help move secretions toward the excretory duct. They are present in both acini and ducts and are characterized by their flat nuclei, which can be difficult to identify in histological sections.

Question 27

Q: How can you identify the parotid gland histologically?

Answer 27

A: The parotid gland is a serous-only gland with numerous long ducts. Striated ducts are large and easily recognizable. The gland contains significant amounts of adipose tissue, and the facial nerve (Cranial Nerve VII) passes through it.

Question 28

Q: What are the histological features of the sublingual gland?

Answer 28

A: The sublingual gland is a mixed gland with a predominance of mucous cells, resulting in pale staining tissue. The secretory portions are more tubular rather than acinar in shape.

Question 29

Q: How can you identify the submandibular gland?

Answer 29

A: The submandibular gland is a mixed serous-mucous gland with obvious serous demilunes. The gland tissue shows brightly stained areas with patches of pale cells.