Formation of the human digestive system, depicted at about A 16 days, B 18 days, C 22 days, and D 28

1
Digestive System Alimentary Canal develops
from endoderm and splanchnic mesoderm
Formation of the human digestive system,
depicted at about (A) 16 days, (B) 18 days, (C)
22 days, and (D) 28 days.
2
Digestive System Alimentary Canal develops
from endoderm and splanchnic mesoderm
four layers of the digestive tract - the mucosa
(1), the submucosa (2), the muscularis (3),
the serosa (4). Peritoneum - visceral vs
parietal Mesentery
)
3
Epi Ecto invaginates to meet endo to form
Stomodeum Proctodeum A septum separates the
cloaca into anus (dorsal) and urogenital (ventral
sagittal view of the 6-week embryo. The stomach
region has begun to dilate, and the pancreas is
represented by two buds that will eventually
fuse.
4
Alimentary Canal and Association Organs
Differentiation of associated organs at the level
of the forming stomach occurs both dorsally
(spleen) and ventrally (liver).
5
respiratory tract and aveolar epithelium are
endoderm in origin with mesoderm contributing
surrounding tissue
the respiratory system does not carry out its
physiological function (of gas exchange) until
after birth. The lungs go through distinct
phases of development and late in fetal
development respiratory motions and amniotic
fluid are thought to have a role in lung
maturation. Development of this system is not
completed until the last weeks of Fetal
development, just before birth. Therefore
premature babies have difficulties associated
with insufficient surfactant (end month 6
alveolar cells type 2 appear and begin to secrete
surfactant).
6
In the head/neck region, the pharynx forms a
major arched cavity within the phrayngeal arches.
The upper row of illustrations are sections
through the embryo at the plane indicated,
showing the fates of the pharyngeal pouches. The
first forms the external auditory passages, while
the second pouch expands, eventually covering
pouches 2, 3, and 4