The document discusses early human embryo development from the morula stage through formation of the embryonic plate and germ layers. Key events include: - The morula forms from the 16-cell embryo and has an inner cell mass and outer trophoblast layer. Fluid then accumulates to form the blastocyst with a cavity and embryonic/animal pole. - The embryonic plate forms with distinct germ layers - ectoderm, endoderm, mesoderm and associated structures like the notochord and neural groove. - Various tissues and organs derive from each germ layer, including the epidermis, nervous system, muscles and glands from ectoderm and endoderm respectively.

1. EMBRYOLOGY
PRACTICAL

2. MORULA
•As the cleavage proceeds the
ovum comes to have 16 cells.
•It looks like a mulberry.
•It is still surrounded by the zona
pellucida.
•It has inner cell mass and outer
layer of cells giving rise to future
trophoblast.
•The inner cell mass give rise to
embryo proper so called
embryoblast.

3. * Fluid accumulation starts.
•Inner cell mass and
trophoblast are well
defined.
•Zona pellucida
disappears.

4. BLASTOCYST
•Know the morula
becomes the blastocyst.
•The cavity – blastocoele.
•The side of the blastocyst
to which inner cell mass is
attached is known as
embryonic /animal pole
and the opp side-
aembryonic pole.

5. EMBRYONIC PLATE
LABELLED WITH RESPECTIVE COLOURS
•SURFACE ECTODERM
•PRIMITIVE GROOVE & PRIMITIVE FOLDS
•BUCCOPHARYNEAL (ABOVE)&CLOACAL
MEMBRANE( BELOW)
•PRIMITIVE NODE
•PRIMITIVE STREAK ( LINE BETWEEN THE
PRIMITIVE NODE AND CLOCAL
MEMBRANE.)

6. EMBRYONIC PLATE
SHOWING GERM LAYERS
•SURFACE ECTODERM
•NOTOCHORD
•NEURAL GROOVE
•ENDODERM
•MESODERM(paraxial,intermedi
ate and lateral plate mesoderm)
•Curves on sides are EXTRA
EMBRYONIC MESODERM.

7. SURFACE ECTODERM DERIVATIVES:
1. Epidermis of skin
2.sweat glands and sebaceous glands
3. mammary glands
4. hair ,nails, enamel of teeth
5. epithelium of lip, cheeks, gums
6. lens of eye
7. anterior pitutary
8. internal ear
9. epithelium of cornea, conjunctiva,ciliary
body and iris
10. outer layer of tympanic membrane.

8. FROM NEURAL CREST CELLS :
•MEDULLA & SUPRA RENAL GLAND
•PIGMENT CELLS( melanocytes)
•SCHWANN CELLS
•DORSAL ROOT GANGLIA
•SYMPATHETIC GANGLIA
•DENTINE OF TEETH
•BONES OF HEAD
•BULBAR AND CONJUNCTIVAL RIDGES IN THE
HEART.

9. FROM NEURAL TUBE:
•BRAIN & SPINAL CORD
• RETINA
•PINEAL BODY
•POSTERIOR PITUITARY

14. PHARYNGEAL ARCHES.
1st arch-mandibular nerve-medial and lateral
pterygoid,temporalis, massestor,mylohyoid, ant belly of
digastric muscles,tensor tympani and tensor palati.
2nd arch-facial nerve- facial muscles, occipitofrontalis,
platysma,stylohyoid,posterior belly of digastric,stapedius,
auricular musles
3rd arch-glossopharyngeal nerve- stylopharyngeus
4th arch- superior laryngeal nerve- muscles of larynx and
pharynx
5th-glossopharyngeal nerve

15. ENDODERMAL POUCHES
1ST POUCH-ventral part forms the tongue,dorsal part along with
dorsal part of the second pouch forms a diverticulum along the
developing ears,called tubo tympanic recess.Proximal part called
auditory tube and distal part called middle ear cavity.
2nd pouch- epithelium of the ventral part of this pouch contributes to
the formation of the tonsil.
3rd- inferior parathyroid glands and the thymus
4 th pouch- superior parathyroid glands and thyroid gland.
5th pouch or ultimobrachial pouch. Generally incorporated with the
4 th pouch forming caudal pharyngeal complex.
The superior parathyroid arises from this and also the parafollicular
cells of the thyroid gland.

16. ECTODERMAL CLEFTS
FIRST cleft- develops into the epitheal lining of the
External acoustic meatus, the pinna is formed from
a series of swellings or hillocks, that arise on the
first and second arches,where they adjoin the first
cleft. The ventral part of this arch is obliterated.
Cerival sinus present between the second arch and
remaining arches.