Download Chapter 5 Embryology / Histology

Chapter 8
Embryology / Histology
Embryology

Study of prenatal
growth and
development.
 Study

of embryos
immature organism
contained within the
coverings of an egg or
within the body of the
mother

Conception

Ovum



Sperm


Female cell
Fertilized by the
Male cell
This begins gestation


The time from conception
to birth
38 – 40 weeks average
Prenatal Phases

Zygote (1st phase)
 Conception


Cells are blank
‘Stem cells’
 Proliferation


– 2 weeks
occurs
Cells rapidly increasing
in numbers
Causes cell growth

Multiply by dividing
Prenatal Phases

Embryo (2nd phase)
week – 8 week
 Differentiation occurs
3

Development of
individual
characteristics



18-19
Cells
days→
Tissues
Forms and shapes

5 weeks (ectopic pregnancy)
Stages of differentiation

Cytodifferentiaton
 Development

Histodifferentiation
 Development

of different cells
of different tissues
Morphodifferentiation
 Development
of different forms / shapes
Primary embryonic layers

Ectoderm
 Outside
layer of the
embryo
 Forms





Skin
Hair
Nails
Brain
Enamel of the teeth
Primary embryonic layers

Mesoderm
 Middle
layer of the
embryo
 Forms





Lining of stomach
Bones
Muscles
Several body systems
Dentin, cementum, pulp
of the teeth
Primary embryonic layers

Endoderm
 Inside
layer of the
embryo
 Forms



Glandular organs
Lining of respiratory
system
Digestive tract
Prenatal Phases

Fetus (3rd phase)
 9th
week – birth
Proliferation and differentiation continue
 Growth and development continue

Stomodeum (primitive mouth)
1st sign of a developing mouth on an embryo


30-32 days
28-29 days ↓
→
Developmental disturbances

Cause abnormal
growth or
development of the
fetus.
 Genetics
 Medications
 Trauma
 Alcohol
 Drugs
Developmental disturbances

Cleft


Improper fusion or joining
of body structure.
Cleft lip

Improper fusion of the
max. process w/ the nasal
process.




Unilateral
Bilateral
Partial
Complete
Developmental disturbances

Cleft palate
 Improper
fusion of the
palatal process w/ the
max. process.




Unilateral
Bilateral
Partial
Complete
Developmental disturbances

FAS
 Fetal
alcohol
syndrome

Consumption of alcohol
during gestation.



Stunts growth / weight
Affects neurons /
brain development
Causes Craniofacial
deformities
Transition / conclusion
Understanding growth and development
will lead you to understanding how
different cells form different tissues.
 This leads us to the next part of this
chapter…..
 Histology

Histology

The study of tissue in
thin slices.
 Aka
microscopic
anatomy
 Essential part of
understanding biology
Tissue types

4 basic types of tissue
 Epithelial
 Nervous
 Muscle
 Connective
Tooth tissues

Enamel

Hardest tissue

Cells that form enamel
Harder than bone, harder
than cementum.

Anatomical crown

Light passes through


No pain

Cells that form dentin
Bulk of the tooth

No nerves/blood supply

Odontoblasts

Translucent



Covers the top of the tooth.


Dentin
Ameloblasts



Comprised of dentinal
tubules
Filled w/ dentinal fluid
Sends sensory info to the
pulp.
Gives a tooth it’s ‘hue’

Underlying color
Tooth tissues

Cementum
 Covers
dentin on the
roots

Pulp
 Provides

Cementoblasts

Cells that form
cementum.
 Softer
than enamel or
dentin.


Can be brushed away.
Nourishment to the
dentin.
 Detects


Temperature and
Chemical changes
 Transmits

Stimuli to the brain
Tooth pulp

Pulp chamber


Pulp horns


Bulk of the pulp located
here!
Upward projections at the
top of the chamber
Pulp canals

Aka root canals

Small hollow tubes from
apical foramen to the
chamber.
Tooth tissue junctions

CEJ
 Cementoenamel
junction

DEJ
 Dentinoenamel
junction
Periodontal tissues

Gingiva
 Covers



bone
Sulcus
Epithelial attachment
Bone
 Alveolar

bone
Lamina Dura

Compact bone that
lines socket.
Periodontal tissues

PDL
 Periodontal



Attaches tooth to bone
“shock absorber”
Nourishment to
cementum
 Sharpey’s

ligament
fibers
Attach PDL to tooth and
bone.
Conclusion
You are NOW the expert!
 You should know the 4 different types of
tooth tissues…
 Their purpose/function
 Where they are located on the tooth.
 Please review this info for the quiz.
 Any questions???????
