Formation of the human digestive system, depicted at about (A) 16 days, (B) 18 days, (C) 22 days, and (D) 28 days. Digestive System Alimentary Canal develops.

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

Digestive System Alimentary Canal develops from endoderm and splanchnic mesoderm

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 parietalMesentery

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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.

Epi Ecto invaginates to meet endo to form Stomodeum & Proctodeum

A septum separates the cloaca into anus (dorsal) and urogenital (ventral

Alimentary Canal and Association Organs

Differentiation of associated organs at the level of the forming stomach occurs both dorsally (spleen) and ventrally (liver).

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).

respiratory tract and aveolar epithelium are endoderm in origin with mesoderm contributing surrounding tissue

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

In the head/neck region, the pharynx forms a major arched cavity within the phrayngeal arches.