Dental students

1. ORAL
EMBRYOLOGY

2. CHAPTER CONTENTS
1.Introduction to general and oral Embryology
2. Development of the Oral Facial Region
3. Development of the Face and Palate
4. Development of Teeth
5. Eruption and Shedding of the Teeth
6. Enamel
7. Dentin and Dental Pulp

3. CHAPTER CONTENTS
8. Cementum
9. Periodontium: Periodontal Ligament
10.Periodontium: Alveolar Process and Cementum
11.Oral Mucosa
12.Salivary Glands and Tonsils.

4. CHAPTER CONTENTS
CHAPTER ONE
Introduction to general and oral
Embryology

5. Introduction
WHAT IS EMBRYOLOGY?
Embryology is the study of prenatal development in the stages before birth.
Pregnancy begins with conception, also known as fertilization
This occurs when the sperm penetrates and fertilizes the ovum
Birth occurs, on average, 38 weeks after conception, or 40 weeks after
the beginning of the last menstrual period (LMP).
For general descriptive purposes, this is divided into three trimesters of 3
months each
In embryology, developmental age is based on the date of conception, which is
assumed to have occurred 2 weeks after the LMP.

6. Early embryogenesis
Say you have an egg cell, like this.
The outer glycol-protein coat called
Zona-pellucida, and plasma
membrane inside it.
And sperm has made its way
through the zona pellucida.
And managed to get in through
plasma membrane, emerged its
genetic material inside the egg, you
are now called Zygote.

7. Sperm Fertilizes
the Ovum and
Unites with It to
Form the Zygote

8. Early embryogenesis

9. Cleavage
After fertilization, it divide into multiple cells.
So fast, and actually just split into two cell, and this process of
splitting without growth is called Cleavage.
Cleavage: Rapid cell division that leads to a multicellular embryo.

10. Cleavage
And this a number of time, dividing from
two cells to four, and from four cells to
eight, all the while staying within the
Zona-pellucida.

11. Early embryogenesis

12. CONT…
You’ve gone 16 to 32 cells, at this point you look different enough
that somebody decides to give you a new name.
So instead of being called a zygote, you have called Morula. (morula
is just Greek word that means Mulberry.
You actually look a little bit like mulberry.
Now, you’ve finished with the Cleavage stage of early
embryogenesis.

13. Morula

16. CONT…
The different cells within the morula, start to get closer and closer
together.
And in fact, the cells start to get a little bit different from each
other.
Then the out side cells, also little bit different the inside cells.
And that different things is called Differentiation.
Finally, we’ve two separate population of cells.
The outside which is called Trophoblasts.
And inside are Embryoblasts.

18. BLASTULATION
And the cavity is called Blastcoel.
A new little bit, which is more different than you’ve in past, the
structure that you’re turned into, with a blastocoel and outer cell
ring of trophoblasts is called Blastocyst.
That means after cleavage the process is called Blastulation.

19. BLASTULATION

20. GASTRULATION
As the process continue, a developed another cavity, which is called
Amniotic Cavity.
And also the inner mass of embryoblasts has started to differentiate
more.
Now, it’s got this layer on the bottom of it here, and the cells in this
layer are called Hypoblasts.
While the cells in the layer just above it are called Epiblasts.
And the formation of the primitive streak from bilaminar disc of the
next stage of early embryogenesis is called Gastrulation.

24. A thickening containing
midline groove forms
along the midsagittal
plane of the embryonic
disc.

25. After the next days, this
thickening, called
Primitive Streak, elongate
to occupy about half the
length of the embryonic
disk.
The groove formed is
called Primitive Groove.

32. CONT…
Now, what that primitive streak actually is the site where the cells in this epiblast layer
of bilaminar disk start to migrate.
The path of that migrating cell heap themselves up right at the primitive streak, and
then they start burrowing their way down into the bilaminar disk. And they go out into
the hypoblast layer.
.

33. CONT…

35. NEURULATION
Now, we have three layers, which are actually called Germ layers.
Also that process of formation of the three layers is known as
Gastrulation.
 That final stage in early embryogenesis
is called Neurolation. Because as you
might expect with “Neuro” in the name,
we see some neural elements formed.

36. Primary Embryonic Layers
During the third week of development, the cells of the
embryo form the three primary embryonic layers:
Ectoderm: The outer layer of cells in the embryo
Mesoderm: The middle of the three primary germ layers of
the embryo.
Endoderm: The innermost of the three primary germ layers of
the embryo.

37. Three primary embryonic layers

38. Three primary embryonic layers

40. Prenatal Development
Prenatal Development The preimplantation period
is the first week
The embryonic period extends from the beginning
of the second week to the end of the eighth week;
at this time the developing life is known as an
embryo
The fetal phase begins with the ninth week and
lasts until birth.

41. CONT…
Prenatal life comprises of three periods:
 Pre-embryonic: 0 - 2 weeks
 Embryonic: 3 - 8 weeks (period of organogenesis)
 Fetal: 9 weeks to birth.

42. Common terms used in
embryology:
Cephalic and Caudal: Cephalic refers to
the head of the embryo, while caudal
refers to the tail (inferior) end. Cranial is
often used instead of cephalic when
describing a location of one structure
relative to another.

43. Common terms used in
embryology:
Ventral and Dorsal: The term
ventral refers to the anterior
(front) aspect of the embryo,
while dorsal refers to the
posterior (back).

44. Common terms used in embryology:
Rostral and Caudal: Rostral is
taken from the Latin rostrum, to
mean towards the nose/beak.
Rostral therefore refers to the
anterior (front) aspect of the
head. In this context, caudal
refers to the posterior (back) of
the head.

46. CONT…
Development, growth and differentiation continues after. So
the total life span of a human is divided in to phases.
1) Prenatal: before birth (total 280 days)
2) Birth.
3) Postnatal: After birth which can be further divided in to:
Infancy
Childhood
Puberty
Adolescence
Adulthood.

47. CONT…
ORAL EMBRYOLOGY:
Oral embryology is the study of the development
of the oral cavity, and the structures within it.
The majority of oral embryological development
occurs between weeks 3 and 8 after conception,
and the oral and facial structures are fully formed
by week 12.

48. Third week
Shallow indentation of
the ectoderm at the
head end of the embryo
develops (this is the
primitive mouth, or
stomodeum).
This is separated from the
rudimentary pharynx by a
temporary structure called the
oropharyngeal membrane.

49. Fourth
week

50. END
ANY
QUESTIONS