This document discusses the early development of the branchial arches in humans. It begins with an overview of basic embryology concepts. It then explains that the branchial arches develop as six bars of mesoderm and endoderm adjacent to the primitive pharynx between the 4th and 5th week of development. The branchial arches each contain cartilage, muscle, nerves and arteries. Their derivatives give rise to important head and neck structures including bones, muscles, nerves and the arteries of the head and neck.

1. Presented by:
Dr. Jamal Giri
Resident (1st
Year)
Development of Branchial
arches

2. Contents
 Introduction.
 Basic embryology.
 Development of Branchial arches.
 Derivatives of Branchial arches.
2

3. Embryology
 Embryo
 Greek word “Embryon”= unborn
 The branch of biology that deals with the
formation, early growth, and development
of living organisms.
3

4.  Ovum Embryo Foetus
4

5. Gametogenesis
 Spermatogenesis
 Spermiogenesis
5

6. Gametogenesis (cont..)
 Oogenesis
6

7. Ovulation
7

8. Fertilization
 Ampulla of the fallopian tube
8

9. 1st
week
9

10. 10

11.  End result of first
week.
 implanted
blastocyst
11

12. 2nd week (week of two’s)
 Trophoblast differentiates into two layers:
 cytotrophoblast and syncytiotrophoblast.
 Embryoblast forms two layers:
 epiblast and hypoblast. (Bilaminar)
 Formation of 2 cavities:
 amniotic and yolk sac cavities.
12

13.  9-day blastocyst (Bilaminar disc)
13

14.  13-day blastocyst (uteroplacental
circulation established).
14

15. 3rd
week
 Gastrulation:
 Primitive streak formation.
 Invasion of epiblast cells.
 Formation of 3 germ layers
15

16. 16

17. 17

18. 18

19. 19

20. Which is the most important time
of human life?
"It is not birth, marriage, or death, but
gastrulation, which is truly the most
important time in your life."
Lewis Wolpert (1986)
20

21. 21

22. Notochord formation
 Days 16-18
 Primitive node epiblast
cells invaginate and
migrate anteriorly
towards prochordal
plate – Notochordal
process.
 Represents early
midline axis of the
embryo
22

23. Neurulation
 Notochord induces the
overlying ectoderm to
thicken and
differentiate into
neural plate.
 Neural groove
 Neural tube
23

24. 24

25. Neural crest cells
 Transient,
multipotent,
migratory cell
population unique
to vertebrates.
 “4th
germ layer.”
25

26. 26

27. 4th
week- The body takes shape
 Folding of the
embryo in the
cranio-caudal plane.
 From a flat disc to
a C-shaped embryo.
27

28. Process of folding
28

29. 29

30. 5th
-8th
week (2nd
month)
 Embryo first looks
recognizably
human.
 All major organs
are in place.
 Head is
disproportionately
large.
30

31. Actual size of embryo
31

32. The branchial arches
 Greek “Branchia”
means gill.
 Develop adjacent to
primitive pharynx.
32

33. 33

34. Branchial apparatus
 Pharyngeal arches
 Pharyngeal
pouches
 Pharyngeal clefts
or grooves
 Pharyngeal
membrane
34

35. Development of Branchial arch
 Neural crest cells migrate into the head
and neck region (4th
week)
35

36.  The endodermal wall of the foregut is
separated from the surface ectoderm by a
layer of mesoderm.
 Soon after, the mesoderm is arranged in
the form of six bars.
 5th
arch soon degenerates.
36

37. Pharyngeal arch components
 A typical pharyngeal
arch contains:
 Cartilaginous rod
(skeleton of arch)
 Muscular component
 Nerve
 Artery
37

38. Derivatives of branchial arches
 Head and neck region of human beings
develop from these branchial arches.
 Skeletal derivatives
 Muscular derivatives
 Nerves supply
 Arterial supply
38

39. Skeletal derivatives
39

40. Skeletal derivatives
40

41. Muscular derivatives
41

42. Nerve supply/derivatives
42

43. Arterial derivatives
 Arch I : Part of the maxillary artery
 Arch II : Hyoid and stapedial arteries
 Arch III : Part of the carotid system
 Arch IV : Left side-arch of aorta, Right
side-right subclavian artery
 Arch VI : Pulmonary arteries
43

44. 44

45. Pharyngeal pouches
 The endoderm of
the pharynx lines
the internal
aspects of
pharyngeal arches
and passes into
balloon like
diverticula called
pharyngeal
pouches
45

46. Pharyngeal Grooves or Clefts
 These grooves
separate the
pharyngeal arches
externally
 Out of four pairs
only first pair
persists as the
external acoustic
meatus.
46

47. Pharyngeal Membranes
 The endoderm of the
pouches contacts the
ectoderm of the
pharyngeal grooves and
form the double layered
pharyngeal membranes.
 First pharyngeal
membrane becomes the
tympanic membrane,
others obliterate 47

48. 48