Chapter 8 Embryology and Histology

Germinal Period (Zygote)

The first two weeks of prenatal development after conception, characterized by rapid cell division and the beginning of cell differentiation.

Embryonic Period (Embryo)

Development from 2-8 weeks after conception, when the brain, spine, major organs, and bodily structures form. This is the most critical time because cells begin to proliferate, differentiate, and integrate into specialized systems

Fetal Period (Fetus)

From eight weeks to birth

Increased growth and "fine detailing"

conception/fertilization

the union of the ovum and sperm

Stomodeum

The embryonic invagination that becomes the oral cavity. It merges with the primitive pharynx during the fourth week of development

Odontogenesis

Formation of new teeth. The first signs of tooth development are found in the lower anterior region, followed shortly by the upper anterior, and then progressing toward the posterior in both jaws

Bell stage of tooth development

The cells differentiate and become specialized in a process called histodifferentiation. (4th stage)

Initiation Stage of tooth development

At 6th to 7th week, Induction. Ectoderm lining stomodeum gives rise to oral epithelium and then to dental lamina; adjacent to deeper ectomesenchyme, which is derived from the neural crest cells. Both tissue types are separated by a basement membrane. (1st stage)

Cap stage of tooth development

9th and 10th week, Proliferation, differentiation, morphogeneisis. Formation of tooth germ as enamel organ forms into cap shape that surrounds inside mass of dental papilla, with an outside mass of dental sac, both from the ectomesenchyme. (3rd stage)

Bud stage of tooth development

At the 8th week, Proliferation. Growth of the dental lamina into a bud shape that penetrated the growing ectomesenchyme. (2nd stage)

anatomical crown

Portion of the tooth that is covered with enamel

Clinical crown

That portion of the tooth that is visible in the oral cavity

enamel

hard, outermost layer of a tooth. hardest substance in the human body. its primary mineral component is Hydroxyapatite.

Dentin

Dense tissue forms the bulk of a tooth. contains microscopic canals called dentinal tubules.Each tubule contains a dentinal fiber that transmits pain stimuli, making dentin a living, sensitive tissue

Ameloblasts

Cells that form enamel

Osteoblasts

bone forming cells

Odontoblasts

Cells that form dentin

Osteoclasts

Bone-destroying cells

Cementoblasts

Cells that form cementum

Fibroblasts

In connective tissue, cells that secrete the proteins of the fibers.

Zygote Period of Prenatal Development

2 weeks, fertilization, implantation, start of placenta

natal teeth

teeth present at birth

Neonatal teeth

Erupt within the first 30 days of life

Cementum

material covering the tooth root

pulp cavity

contains blood vessels and nerves

CEJ (cementoenamel junction)

Where enamel of crown and cementum of root meet

DEJ (dentinoenamel junction)

Where the dentin and enamel meet

alveolar bone

bone that supports and encases the roots of teeth

gingiva

tissue surrounding the teeth and covering the jaw

apical foramen

the hole at the tip of the root where nerves and blood vessels enter the tooth

Maxillary Central incisor (Primary)

Eruption Date: 6-10 months; Exfoliation Date: 6-7 years; #1

Maxillary Lateral incisor (Primary)

Eruption Date: 9-12 months; Exfoliation Date: 7-8 years; #2

Maxillary First molar (Primary)

Eruption Date: 12-18 months; Exfoliation Date: 9-11 years; #3

Maxillary Canine (Primary)

Eruption Date: 16-22 months; Exfoliation Date: 10-12 years; #4

Maxillary Second molar (Primary)

Eruption Date: 24-32 months; Exfoliation Date: 10-12 years; #5

Mandibular Central incisor (Primary)

Eruption Date: 6-10 months; Exfoliation Date: 6-7 years; #1

Mandibular Lateral incisor (primary)

Eruption Date: 7-10 months; Exfoliation Date: 7-8 years

Mandibular First molar (primary)

Mandibular First molar (primary)

Mandibular Canine (primary)

Eruption Date: 16-22 months; Exfoliation Date: 9-12 years

Mandibular Canine (primary)

Eruption Date: 12-18 months; Exfoliation Date: 10-11 years

Mandibular Second molar (primary)

Eruption Date: 20-32 months; Exfoliation Date: 10-12 years

Maxillary Central incisor (Permanent)

Eruption Date: 7-8 years; Order of Eruption: #2

Maxillary Lateral incisor (Permanent)

Eruption Date: 8-9 years; Order of Eruption: #3

Maxillary Canine (Permanent)

Eruption Date: 11-12 years; Order of Eruption: #6

Maxillary First premolar (Permanent)

Eruption Date: 10-11 years; Order of Eruption: #4

Maxillary Second premolar (Permanent)

Eruption Date: 11-12 years; Order of Eruption: #5

Maxillary First molar (Permanent)

Eruption Date: 6-7 years; Order of Eruption: #1

Maxillary Second molar (Permanent)

Eruption Date: 12-13 years; Order of Eruption: #7

Maxillary Third molar (Permanent)

Eruption Date: 17-21 years; Order of Eruption: #8

Mandibular Central incisor (Permanent)

Eruption Date: 6-7 years; Order of Eruption: #2

Mandibular lateral incisor (Permanent)

Eruption date: 7-8 years; order of eruption: #3

Mandibular canine (permanent)

Eruption Date: 9-10 years; Order of Eruption: #4

Mandibular first premolar (permanent)

Eruption Date: 10-11 years; Order of Eruption: #5

Mandibular second premolar (permanent)

Eruption Date: 11-12 years; Order of Eruption: #6

Mandibular first molar (permanent)

Eruption Date: 6-11 years; Order of Eruption: #1

Mandibular second molar (permanent)

Eruption Date: 11-13 years; Order of Eruption: #7

Mandibular third molar (permanent)

Eruption Date: 17-21 years; Order of Eruption: #8