Njds: Histology- Early Tooth Development

Front 1

QUESTION
What is ectomesenchyme and where is it derived from?

Back 1

ANSWER
A type of embryonic connective tissue, derived from the neural crest

Front 2

QUESTION
What is the primary epithelial band?

Back 2

ANSWER
Forms after the 5th week of embryonic development, and consists of a continuous linear epithelial thickening on the presumptive mandible and maxilla that corresponds to the future dental arches

Front 3

QUESTION
What two structures does the primary epithelial band give rise to?

Back 3

ANSWER
Vestibular lamina and dental lamina

Front 4

QUESTION
What initially drives tooth formation?

Back 4

ANSWER
Tooth formation is originally driven by the dental epithelium (through the actions of bone morphogenetic proteins 2 and 4), but it is soon taken over by the ectomesenchyme

Front 5

QUESTION
What characterizes the bud stage of tooth development?

Back 5

ANSWER
The initial proliferation of the dental lamina into the underlying ectomesenchyme

Front 6

QUESTION
Cap stage of tooth development

Back 6

ANSWER
-increasing cellular proliferation
-epithelial bud of the dental lamina increases in size and becomes bluntly crescent shaped.
-Adjacent,localized concentration of ectomesenchymal cells
-At this point, both cell populations are referred to as the tooth germ.

Front 7

QUESTION
What are the structures comprising the tooth germ?

Back 7

ANSWER
1. Enamel organ
2. Dental papilla
3. Dental follicle

Front 8

QUESTION
Enamel (dental) organ

Back 8

ANSWER
Part of the tooth germ, the epithelial component that will form ENAMEL

Front 9

QUESTION
Dental papilla

Back 9

ANSWER
Part of the tooth germ, located immediately below the enamel organ, it is the ectomesenchymal component that forms the DENTIN and PULP

Front 10

QUESTION
Dental follicle

Back 10

ANSWER
Part of the tooth germ, comprised of the ectomesenchyme that surrounds the dental papilla, it gives rise to the CEMENTUM, PERIODONTAL LIGAMENT, and ALVEOLAR BONE

Front 11

QUESTION
Bell stage

Back 11

ANSWER
Increasing convexity of the undersurface of the enamel organ, dissolution of the dental lamina, folding of the internal dental epithelium

Front 12

QUESTION
What happens to the enamel organ during the bell stage?

Back 12

ANSWER
-Cells at center of E.Organ secrete GAG's which causes an osmotic influx of water, leading to distension, forming the stellate reticulum.
-Cells closest to oral cavity become external dental epithelium.
-cells adjacent to dental papilla become internal dental epithelium and stratum intermedium.
-region where EDE and IDE meet is called the cervical loop

Front 13

QUESTION
What are the transient structures of the enamel organ seen during the bell stage?

Back 13

ANSWER
enamel knot, enamel cord, enamel niche

Front 14

QUESTION
What happnes to the dental papilla during the bell stage?

Back 14

ANSWER
A thick basement membrane develops between the IDE and the dental papilla, forming the acellular zone. At this stage, the cells of the dental papilla and dental follicle are still undifferentiated.

Front 15

QUESTION
Crown stage

Back 15

ANSWER
-Cells of IDE stop dividing and begin differentiating into pre-ameloblasts
-Ectomesenchymal cells become odontoblasts and start secreting predentin.
-predentin secretion causes pre-ameloblasts to secrete enamel matrix (thus becoming ameloblasts)
-Both type of cells keep secreting, odontoblasts moving towards the pulp and ameloblasts moving away from the pulp.

Front 16

Vestibular Lamina

Back 16

Arises from the primary epithelial band. Arises through a proliferation of epithelial cells into the ectomesenchyme with subsequent degeneration.

Front 17

Dental Lamina

Back 17

Arises from the primary epithelial band. A series of localized cellular proliferations occurs along the dental lamina, corresponding to the sites of future teeth.