TR056/PG1007 Lecture 6 Deriva6ve of the Endodermal Germ Layer Dr. Neil Docherty My Teaching Objec/ves • To depict the changes leading to the closure of the body wall
and formation of the gut tube
• To outline the series of structure specified by further growth
of the endoderm
Development of The Endoderm
Name a process/structure
WEEK 3
ECTODERM
Ne_____ N_____ T_____
MESODERM
_______genesis Scl____
ENDODERM
TODAY
ENDODERM
Gives rise to;
• Lining of gastrointestinal tract
• Lining of the respiratory tract
• Eptihelium of the thymus
• Epithelium of thyroid and parathyroid
glands
• Auditory epithelium
• Lining of the bladder
Sagittal Midline Sections of Embryo
(Day 17-28)
17d
22d
28d
24d
Foregut
Hingut
Growth in the head and tail region leads to cephalocaudal folding
Lateral Folding and Body Wall Closure
Pinched to a narrow channel
by folding
Lateral folding of the embryo proceeds to body wall closure
by end of week 4
Transverse Section of Gut and Embryonic
Body Cavity Formation (Mouse)
Opening of Foregut and Hindgut
Cephalic end
FOREGUT
Caudal end
HINDGUT
Ectodermal/endodermal membrane
OROPHARYNGEAL MEMBRANE
Rupture in week 4
Ectodermal/endodermal membrane
CLOACAL MEMBRANE
Rupture in week 7
Open cavity at cephalic end of primitive gut
-ORAL CAVITY-ECTODERM LINED
Open cavity at caudal end of primitive gut
-ANUS-ECTODERM LINED
Endoderm Derived Structures Weeks 4 and 5
Sagittal View
ECTODERM
• CNS
• PNS
• Special senses
epithelia
• Integumentary system
MESODERM
ENDODERM
• Muscle
• Lining of gastrointestinal tract
• Cartilage
• Lining of the respiratory tract
• Bone
• Epithelium of the thymus
• Dermis
• Epithelium of thyroid
• Vascular system/blood
and parathyroid glands
• Urogenital system
• Auditory epithelium
• Adrenal Cortex
• Lining of the bladder
Organised assembly of tissue from each layer contributes
to mature tissues and organs (cooperation in gut)
SYSTEMS BASED EMBRYOLOGY
Today’s Learning Objec/ves Your learning from today should focus on being able to;
1)  Explain the sequence of changes that cause closure of the
body wall and formation of the gut tube
2) Recognise the structures specified by further growth
of the endoderm and link the mature gut to integration of
Structures from the ectoderm and mesoderm