ANA 307 Development of The Tongue, Lingual Papillae, Taste Bud and Salivary Glands

Question 1

When does the development of the tongue begin

Answer 1

4th week IUL

Question 2

Which pharyngeal arches contribute to the to the development of the tongue

Answer 2

1st, 2nd, 3rd and 4th

Question 3

First stage of tongue development

Answer 3

Development begins with growth of a medial swelling from the first pharyngeal arch known as tuberculum impar

Question 4

Second stage of tongue development

Answer 4

Gradually 2 Lateral lingual swelling start to grow in the 5th week from the first arch

Question 5

The muscosa overlying the anterior 2/3 of the tongue receives its Innervation from where?

Answer 5

Mandibular branch of CN V

Question 6

The mesoderm of the second third and fourth arch receives its sensory innervation from where?

Answer 6

CN IX glossopharyngeal nerve

Question 7

Third stage of tongue development

Answer 7

As the lateral swellings increase in size they eventually merge and overlap the tuberculum impar, this merging leads to the formation of the anterior 2/3 of the tongue

Question 8

Fourth stage of tongue development

Where does this developing part receive innervation from?

Answer 8

The posterior most part of the tongue develops from a 3rd median swelling arising from the fourth arch, specifically the hyper bronchial eminence

Receives innervation from the superior laryngeal nerve

Question 9

Origin and innervation of tongue muscles

Answer 9

Muscles of the tongue predominantly derive from the myoblasts

innervated by CN XII hypoglossal nerve except palatoglossus which is innervated by vagus nerve CNX

Question 10

What are the extrinsic muscles of the tongue?

Answer 10

Palatoglossus
Genioglossus
Styloglossus
Hyoglossus

Question 11

What are the paired intrinsic muscles of the tongue?

Answer 11

superior longitudinal muscles
inferior longitudinal muscles
transverse muscles
vertical muscles

Question 12

Action of extrinsic muscles of the tongue

Answer 12

Allows the tongue to move an all directions

Question 13

Action of intrinsic muscles of the tongue

Answer 13

Responsible for changing tongue shape

Question 14

When does the development of the taste bud begin

Answer 14

8weeks IUL

Question 15

First stage of taste bud development

Answer 15

Between the 9th and 11the week of gestation many taste buds primordia develop

Question 16

Second stage of taste bud development

Answer 16

They differentiate into different cell types around the 11th to 13th postovulatory week
During this period Taste pores also develop

Question 17

Development of the lingual papillae starts when?

Answer 17

8th week IUL

Question 18

First stage of the development of the lingual papillae

Answer 18

Vallate papillae are first to appear
Filiform papillae develop between 10th to 11th week of gestation

Question 19

Second stage of the development of the lingual papillae

Answer 19

Taste buds start to develop during weeks 11-13 by inductive interaction between the epithelial cells of the tongue and the nerve cells innervating The tongue

Question 20

Types of lingual papillae

Answer 20

Filiform
fungiform
Foliate
Circumvallate

Question 21

What are the salivary glands?

Answer 21

A group of compound exocrine glands that produce saliva, an important fluid required for: lubrication, immunity, mastication, deglutition, taste and speech.

Question 22

What are the major salivary glands?

Answer 22

Paired:

Parotid
Submandibular
Sublingual

Question 23

Where do the 3 major salivary glands develop from?

Answer 23

The parotid gland develops as an ectodermal outgrowth from the cheek at the angle of the stomodeum.
The submandibular gland develops as an endodermal outgrowth from the floor of the mouth.
The sublingual gland develops as multiple endodermal outgrowth from the floor of the mouth

Question 24

The embryologic development of the salivary glands is the result of interaction between 2 distinct tissues

Answer 24

The oral epithelium
Underlying mesenchyme

Question 25

The mucosa of the upper aero-digestive tract is lined by what?

Answer 25

100’s of small minor salivary glands

Question 28

how do the secretions of the glands reach the mouth?

Answer 28

through the ductal system

Question 29

Explain how all the salivary glands have a common embryogenesis

Answer 29

They all develop from growths of oral epithelium into the underlying mesenchyme

Question 30

Salivary glands consist of a series of branched ducts which terminate where?

Answer 30

In a spherical or tubular end piece of acini

Question 31

What arises from the epithelial outgrowths?

Answer 31

the secretory units (acini) and ductal system of each gland will eventually arise from here

Question 32

The epithelial growths are of which origin for the 3 major glands

Answer 32

Ectodermal origin

Question 33

The epithelial growths are of which origin for the minor glands

Answer 33

Mixed ectodermal and endodermal origin

Question 34

Describe the formation of the morphological signature of the glands

Answer 34

The mesenchymal cells contain the information for the branching pattern that will eventually be the morphologic signature of these glands

Question 35

What information is carried my the epithelial cells?

Answer 35

They carry information for the type of salivary secretions that will be produced by each future gland

Question 36

Describe the development of the stroma

Answer 36

The stroma which comprises the capsule of each gland as well as the septae that divide the gland into the lobes and lobules will develop from cranial neural crest cells*

These cells originate from the dorsal part of the neural tube epithelium.

Question 37

Which gland is the 1st to develop in the 6th week IUL?

Answer 37

Parotid gland

Question 38

Which gland is the 2nd to develop in the 7th week IUL?

Answer 38

submandibular

Question 39

Which gland is the 3rd to develop in the 8th week IUL?

Answer 39

sublingual

Question 40

When do the minor glands develop?

Answer 40

9-12th week

Question 41

What occurs during 18-25 weeks?

Answer 41

Salivary glands acquire connective capsules and interlobular ducts
Glandular parenchyma shows rapid growth, leading to high increase in the number of lobules and almost complete canalization of the tubules

Question 42

What are the stages of SG development?

Answer 42

1. Initial bud stage
2. Early pseudo glandular stage
3. Late pseudoglandular stage
4. Terminal differentiation stage

Question 43

Describe the 1st stage of SG development

Answer 43

Initial bud stage

• The pre-bud stage is followed by an invagination of the thickened epithelium into the underlying mesenchyme
• Which leads to the formation of a spherical bud connected to the oral epithelium through a thick solid epithelial stalk
• The epithelial stalk will give rise to the main salivary duct whereas the terminal bud constitutes the primordium of the intralobular parenchyma

-Each epithelial bud is surrounded and separated from the mesenchyme by a basement membrane which is a thick layer of ECM that has within it a broad range of structural macromolecules

Question 44

Describe the 2nd stage of SG development

Answer 44

2. Early pseudo glandular stage

• A solid cord of cells forms from the epithelial bud through cell proliferation
• Condensation and proliferation occur in the surrounding mesenchyme which is closely associated with the epithelial cord
• The basal lamina plays a role in influencing morphogenesis and differentiation in the SG’s throughout development
• The arborization of the SG epithelium is produced by branching morphogenesis
• Clefts form at the surface of the primary epithelial bud, deepen and divide the bud into 2-3 buds
• These newly formed buds expand, elongate and cleft again, successive rounds of expansion, elongation and clefting progressively build up an extensive network of epithelial stalks and end buds

Question 45

Describe the 3rd stage of SG development

Answer 45

3. Late pseudo glandular stage

• Eventually, the network of epithelial stalks and end bud leads to the formation of multilobed glands

-The basement membrane is secreted by the epithelial cells located at the periphery of the salivary epithelial bud and adjacent mesenchymal cells

• Whereas the stromal elements of the ECM are produced by the mesenchymal cells
• The branching continues as the terminal portion of the cord forms an extension tree-like system of bulbs
• As branching occurs, the CT differentiates around the branches, eventually producing extensive tubulation

Question 46

Describe the 4th stage of SG development

Answer 46

4. Terminal differentiation stage

• The final stage of SG development is histodifferentiation of the functional acini and intercalated ducts
• Myoepithelial cells arise from the epithelial stem cells in terminal tubules and develop in concert with acinar cytodifferentiation

-When the ducts and acini are finally hollowed out, the terminal differentiation stage starts

• During this stage, epithelial cells lining the ducts, and tubules. and acini process to differentiate morphologically and functionally (anatomically and physiologically)
• Throughout the glands, the ducts will differentiate into excretory, striated and intercalated types, whereas the cells within the acini differentiate into serous or mucous secretory cells as well as myoepithelial cells
• These changes show that the intercalated ducts lead from the acini to the striated ducts.