Embryology is the science that treats of the origin and development of the individual organism. It is a gradual bringing to completion both in structure and in function. Its chief characteristic is cumulative change in a progressive direction.

1. Embryology is the science that treats of the
origin and development of the individual
organism.
It is a gradual bringing to completion both
in structure and in function. Its chief
characteristic is cumulative change in a
progressive direction.

2. PRE-NATAL AND POST-NATAL
In many animals like fishes and amphibians,
they are capable of an independent existence
at relatively immature stages
- free-living forms called larvae
In man, the human newborn, is fairly complete
anatomically, yet dependent on its elders for
food and care

3. Infancy, childhood and adolescence –
completion of some organs and a gradual
remodeling of body shape
Only at about the age of 25 are the last of
these progressive changes finished and the
body stabilized in the adult condition

4. OVUM – Fertilization to end of first week
EMBRYO – Second to eighth week, inclusive
FETUS – Third to tenth lunar month, inclusive
BIRTH

5. NEWBORN – Neonatal period, birth to end of
second week
INFANCY – Third week, until assumption of
erect posture at end of first year
CHILDHOOD –
Early – Milk tooth period, second to sixth
year, inclusive
Middle – Permanent tooth period, 7 – 10
years, inclusive
Later – Prepubertal period, from 9 or 10 years
to 12-15 years in females, and to 13-16
years in males

6. ADOLESCENCE – the six years following puberty
ADULT –
Prime and transition – between 20 and 60 years
Old age and senescence – From 60 years on
DEATH

7. Morphological and functional categories
DEVELOPMENTAL ANATOMY
Morphological – deals with form, structure and
relations
- purely descriptive and comparative
in treatment
- it traces the formative history of
animals from a germ cell of each parent to
the resulting , adult offspring

8. DEVELOPMENTAL PHYSIOLOGY
Functional – attempts to explain on the basis of
experiment and analysis, the ways in which
development works
EXPERIMENTAL EMBROLOGY – experimental
attack
CHEMICAL EMBRYOLOGY – chemistry of
developmental processes

9. COMPARATIVE EMBRYOLOGY – deals with
different closely related groups
EVOLUTIONARY EMBRYOLOGY
MEDICAL EMBRYOLOGY AND TERATOLOGY
VALUE AND IMPORTANCE OF EMBRYOLOGY
- logically, it is a key that helps unlock the
secrets of heredity, the determination of sex,
and organic evolution

10. - Medically, it is important because it supplies
a comprehensive and rational explanation of
the intricate arrangements of human
anatomy.
The body does not just happen to be arranged
as it is; each end-result is preceded by a
definite course of developmental events.
Because of this, malformations of various kinds
can be explained on the basis of departures
from the usual pattern.

11. It is also able to interpret vestigial structures,
to explain growth, differentiation and repair,
and to shed light on some pathological
conditions.
- It is essential to sound training in anatomy,
pathology and surgery. Furthermore,
obstetrics is largely applied embryology.
Subspecialties like pediatrics and OB find it
an indispensable tool

12. ANCIENT VIEWS OF HUMAN EMBRYOLOGY
Egyptians of the Old Kingdom, about 3,000
B.C. knew of methods for incubating birds’
eggs but they left no records.
Akhnaton (Amenophis IV) praised the sun-
god, Aton, as the creator of the germ in
woman, maker of the seed in man, and giver
of life to the son in the body of his mother.
The ancient Egyptians believed that the soul
entered the child at birth through the
placenta

13. Aristotle – first to formulate the alternative that
an embryo must either be preformed and
only merely enlarging during its
development, or it must be actually
differentiating from a formless beginning
- favored epigenesis
Francesco Redi

14. Louis Pasteur
William Harvey
Kaspar Friedrich Wolff – revived Epigenesis
-observed the development of a chick embryo,
he demonstrated that the embryonic parts
develop from tissues have no counterpart in
adult organism

15. Marcello Malphighi – all organs of the adult
were prefigured in miniature within the sperm
or the egg
Albrecht von Haller and Charles Bonnet
Immanuel Kant and Johann Friedrich
Blumenbach

16. Christian Pander – discovered the 3 germ layers
Ectoderm, Mesoderm, Endoderm
Triploblastic vs diploblastic
- The germ layers did not form their organs
independently enough to indicate what it
truly is, it still needs the help and interaction

17. Karl Ernst von Baer – discovered the notochord
- also discovered the
mammalian egg
Heinrich Rathke – described the formation of
the vertebrate skull

18. - studied the development of
inverts, especially the crayfish.
- discovered the Rathke’s pouch, the
embryonic rudiment of the pituitary.

19. Heredity operates through internal factors
-genes as hereditary determiners
-direct the development of a host of
enzymic reaction-systems
Environment supplies the external factors
-can condition the appearance of genetic
characters
-can modify the developmental
expression of inherited characters

20. -can alter the genetic constitution of
chromosomes (mutations and teratology)
METHODS OF STUDY
- In proper age-sequence
- Serial, related series that permits changing
appearances
- Depth, breadth and length
- Time

21. EPIGENESIS
-embryo organs de novo (from scratch)
PREFORMATION
-all adult organs are preformed and prefigured
in miniature within the sperm or the egg
-aligned with Descartes

22. 1. The general features of a large group of
animals appear earlier in development than
do the specialized features of a smaller
group
2. Less general characters develop from the
more general, until finally the most
specialized appear

23. 3. The embryo of a given species, instead of
passing through the adult stages of lower
animals, departs more and more from them
4. Therefore, the early embryo of a higher
animal is never like a lower animal, but only
like its early embryo

24.  Cell Proliferation
- carried out by mitosis
-DNA synthesis at interphase
-prophase
-metaphase
-anaphase
-telophase – daughter cell formation

25. - Developmental increase in mass
- Fundamental property of life
- Important factor in development

26. 1. Protoplasmic synthesis – building up of new
protoplasmic material from available food
stuff
-takes place when anabolism
exceeds catabolism
2. Water uptake – colloids within cells imbibe
water and swell
ionic concetrations – can hold or release
water

27. 3. Intercellular deposition – results from the
manufacture and the deposit of non-living
substances like jelly, fibers and ground
substance of cartilage and bone
4. Intracellular storage – fat deposition
underneath the skin or in between organs

28. A. Absolute rate – amount of increase during
any period divided by the length of that
period
B. Relative rate – relative increase per unit of
time
- computed by dividing each
absolute rate by the initial value (in
weight/volume/or length)

29. Absolute gain in weight of a 10 lb baby and a
100 lb youth may be 1 lb each but expressed
in relative terms would be 10% and 1%
Generally, organisms grow at the same relative
rate
Differential growth – progressive alteration of
form and proportions both external and
internal

30.  Constitutional factor – control the speed of
growth to be approximately the same in all
individuals of a species; there is little
difference in the final size attained
- inherited qualities predispose
toward a definite basic rate of cell division
and growth

31.  Temperature – each species has its critical
maximum and minimum range at which
development ceases
- optimum temperature – most
favorable temperature for growth
 Nutritional factor – creation of new
protoplasm
-amino acids – building blocks
9 a.a. are indispensable for growth

32.  Growth promoting factors – embryonic
factors increase mitosis and shorten division
time
- hormones – secretions of ductless
glands which regulate growth
thyroid hormone – increases rate of cell
metabolism and oxidative processes
hypophysis – stimulates growth of various
tissues

33. - vitamins – accessory food
substances which animals obtain from plants
vit A – for weight gain/growth of skeleton
vit B12 (riboflavin) – exerts specific
influence on growth; no growth without it
vit C and vit D – essential for normal
growth

34.  Growth arresting factors – check and balance
in growth to prevent gigantism
- Differentiation – implies increasing
structural complexity
- Morphogenesis – change in shape and
organization of the body and its parts
- Histogenesis – progressive change in the
substance and structure of the cells
themselves whereby tissues are created

35. – molding of the body and its organs into form
and pattern
Cell multiplication and growth
1. Cell migration
2. Cell aggregation – masses, cords sheets
3. localized growth – enlargements of
various kinds and constrictions
4. fusion and splitting

36. 5. Folding – evaginations
- invaginations
6. Bending – due to unequal growth
7. Degeneration – to remove temporary or
excess parts
Vestigial organs:
teeth
appendix

37. - Cell specialization controlled by the genes in
the chromosomes (DNA) to transmit coded
information to RNA
- during histodifferentiation, germ layers
that are at first alike in visible structure and
lack of specific shape are designated by the
suffix blast
neuroblast – nerve cell
myoblast – muscle cell

38.  Change form and character as they produce
hairs, nails, lens of eye, enamel of teeth
 Glandular derivatives – sweat glands,
mammary glands, salivary glands, anterior
lobe of hypophysis
 Local specializations – sensory epithelium of
organs of smell, hearing and vision

39.  Cell proliferation
 Morphogenesis
 Histogenesis
- decentralizing processes
-need to be re-investigated into a cooperative
working mechanism
-control is supplied by endocrine glands and
nervous system