Question 1

________ Inner cells of the dental sac
A)Dental pulp
B)Predentin
C)Dental sac
D)Enamel
E)Cement

Accepted Answer

The inner cells of the dental sac differentiate into cementoblasts,which produce cement (L.cementum)and deposit it over the dentin of the root.

Question 2

________ Lanugo
A)Tetracyclines
B)Ameloblastic layer
C)Hair follicles
D)Neural crest cells
E)Epithelial root sheath of the developing tooth

Accepted Answer

Lanugo is the soft downy hairs that are first produced by the hair follicles.These hairs are chiefly shed before or right after birth and are replaced by coarser hairs that arise from new hair follicles.

Question 3

________ Fused layers of enamel epithelia
A)Tetracyclines
B)Ameloblastic layer
C)Hair follicles
D)Neural crest cells
E)Epithelial root sheath of the developing tooth

Accepted Answer

The inner and outer enamel epithelia of the enamel organ come together and fuse in the neck region of the tooth,where they form the epithelial root sheath.This sheath grows into the mesenchyme and initiates root formation.

Question 4

________ Derived from the inner enamel epithelium
A)Tetracyclines
B)Ameloblastic layer
C)Hair follicles
D)Neural crest cells
E)Epithelial root sheath of the developing tooth

Accepted Answer

The ameloblastic layer is derived from the inner enamel epithelium of the enamel organ.The ameloblasts produce enamel and deposit it over the dentin.As the enamel increases,the ameloblasts regress toward the outer enamel epithelium.Enamel and dentin formation begins at the tip (cusp)of the tooth and progresses toward the future root.

Question 5

________ Dental lamina
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The dental lamina develops from the oral ectoderm and gives rise to the deciduous and permanent tooth buds.

Question 6

________ Melanocytes
A)Tetracyclines
B)Ameloblastic layer
C)Hair follicles
D)Neural crest cells
E)Epithelial root sheath of the developing tooth

Accepted Answer

Melanocytes differentiate from melanoblasts,which are derived from neural crest cells.Melanoblasts migrate into the dermis during the early fetal period and soon enter the epidermis where they slowly differentiate into melanocytes.These cells produce melanin and distribute it to the epidermal cells after birth.Melanoblasts also migrate into the hair bulbs and differentiate into melanocytes.Melanin is distributed to the hair-forming cells before birth.

Question 7

________ Sebaceous glands
A)Tetracyclines
B)Ameloblastic layer
C)Hair follicles
D)Neural crest cells
E)Epithelial root sheath of the developing tooth

Accepted Answer

Most sebaceous glands arise as buds from the sides of the epithelial root sheaths of hair follicles,late in the second trimester of pregnancy.A few sebaceous glands develop from the epidermis,independently of hair follicles (e.g. ,in the eyelids and labia minora).

Question 8

________ Bud of the permanent tooth
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The tooth buds for the permanent teeth develop from continuations of the dental laminae.They begin to appear at about 10 weeks and lie lingual to the deciduous tooth buds.

Question 9

________ Contains vessels and nerves
A)Dental pulp
B)Predentin
C)Dental sac
D)Enamel
E)Cement

Accepted Answer

The dental pulp derived from the mesenchymal dental papilla of the embryo contains the vessels and nerves of the tooth.

Question 10

________ Periodontal ligament
A)Dental pulp
B)Predentin
C)Dental sac
D)Enamel
E)Cement

Accepted Answer

The periodontal ligament is derived from the dental sac,a capsule-like structure that develops from the mesenchyme surrounding the tooth.

Question 11

________ Derived from the neural plate
A)Tetracyclines
B)Ameloblastic layer
C)Hair follicles
D)Neural crest cells
E)Epithelial root sheath of the developing tooth

Accepted Answer

Neural crest cells are derived from the neuroepithelium of the neural plate.When the neural folds fuse,some neuroectodermal cells at the lateral edges of the neural plate are not incorporated into the neural tube;these cells form the neural crest that gives rise to neural crest cells.

Question 12

________ Dental papilla
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The dental papilla,a condensation of mesenchyme,invaginates the tooth bud,giving it the appearance of a cap.The dental papilla gives rise to the dental pulp and to the odontoblasts,which form the dentin.There is some evidence that the mesenchymal cells that differentiate into odontoblasts are derived from the neural crest.

Question 13

________ Ameloblasts
A)Dental pulp
B)Predentin
C)Dental sac
D)Enamel
E)Cement

Accepted Answer

The ameloblasts are enamel formers.They produce long enamel prisms and deposit them over the dentin.Enamel formation begins at about 20 weeks in the deciduous teeth and continues in the permanent teeth until about age 16.If vitamin D is deficient during this period,the erupted surfaces of the teeth may be rough instead of smooth and shiny.The ameloblastic layer also induces the odontoblastic layer to form.Hence,if the ameloblasts do not differentiate normally (e.g. ,as in vitamin A deficiency),dentin formation is also affected.

Question 14

________ Discoloration of teeth
A)Tetracyclines
B)Ameloblastic layer
C)Hair follicles
D)Neural crest cells
E)Epithelial root sheath of the developing tooth

Accepted Answer

Tetracycline antibiotics are known to cause brownish yellow discoloration and fetal enamel hypoplasia if given to pregnant females or to children.If given after the eighth year,the third molar teeth are the only ones that may be affected because they are still developing.

Question 15

________ Odontoblasts
A)Dental pulp
B)Predentin
C)Dental sac
D)Enamel
E)Cement

Accepted Answer

The odontoblasts derived from mesenchymal cells in the dental papilla (future pulp)give rise to predentin and deposit it adjacent to the inner enamel epithelium.Later,the predentin calcifies and becomes dentin.

Question 16

________ Induction of the odontoblastic layer
A)Tetracyclines
B)Ameloblastic layer
C)Hair follicles
D)Neural crest cells
E)Epithelial root sheath of the developing tooth

Accepted Answer

The ameloblastic layer induces the mesenchymal cells in the dental papilla adjacent to the inner enamel epithelium to differentiate into odontoblasts.If there is a deficiency of vitamin A,the ameloblasts do not differentiate properly.Consequently,there is abnormal formation of odontoblasts.

Question 17

________ Inner enamel epithelium
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The inner enamel epithelium of the enamel organ induces the adjacent mesenchymal cells in the dental papilla to differentiate into an odontoblastic layer.The inner enamel epithelium differentiates into ameloblasts,the enamel-forming cells.

Question 18

________ Dental sac
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The dental sac develops from the mesenchyme that surrounds the developing tooth.This capsule-like structure gives rise to cementoblasts,which form cementum,and to the periodontal ligament,which embeds in the cementum and the surrounding bony socket of the tooth.Thus,the periodontal ligament holds the tooth in its socket.

Question 19

________ Inner enamel epithelium
A)Dental pulp
B)Predentin
C)Dental sac
D)Enamel
E)Cement

Accepted Answer

Cells of the inner enamel epithelium adjacent to the dentin differentiate into ameloblasts.These cells produce enamel in the form of prisms (rods)and deposit it over the dentin.

Question 20

________ Part of the enamel organ
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The inner enamel epithelium is part of the enamel organ.Other parts are the outer enamel epithelium and the enamel reticulum.For a while,the enamel organ is attached to the oral epithelium by the dental lamina.

Quiz 17: Integumentary System

________ Inner cells of the dental sac

________ Lanugo

________ Fused layers of enamel epithelia

________ Derived from the inner enamel epithelium

________ Dental lamina

________ Melanocytes

________ Sebaceous glands

________ Bud of the permanent tooth

________ Contains vessels and nerves

________ Periodontal ligament

________ Derived from the neural plate

________ Dental papilla

________ Ameloblasts

________ Discoloration of teeth

________ Odontoblasts

________ Induction of the odontoblastic layer

________ Inner enamel epithelium

________ Dental sac

________ Inner enamel epithelium

________ Part of the enamel organ