| Endoderm | |
|---|---|
 Tissues derived from endoderm. | |
| Details | |
| Days | 16 |
| Precursor | Epiblast |
| Identifiers | |
| MeSH | D004707 |
| FMA | 69071 |
| Anatomical terminology | |
Endoderm is the innermost of the three primarygerm layers in the very earlyembryo. The other two layers are theectoderm (outside layer) andmesoderm (middle layer).[1] Cells migrating inward along thearchenteron form the inner layer of thegastrula, which develops into the endoderm.[2]
The endoderm consists at first of flattened cells, which subsequently become columnar. It forms theepithelial lining of multiple systems.
Inplant biology, endoderm corresponds to the innermost part of thecortex (bark) in youngshoots and youngroots often consisting of a singlecell layer. As theplant becomes older, more endoderm willlignify.
The following chart shows thetissues produced by the endoderm.The embryonic endoderm develops into the interior linings of two tubes in the body, the digestive and respiratory tube.[3]
| Layer | Category | System | |
|---|---|---|---|
| General[4] | Gastrointestinal tract | the entirealimentary canal except part of themouth,pharynx and the terminal part of therectum (which are lined by involutions of theectoderm), the lining cells of all the glands which open into the digestive tube, including those of theliver andpancreas | |
| General | Respiratory tract | thetrachea,bronchi, andalveoli of thelungs | |
| General | Endocrine glands and organs | the lining of the follicles of thethyroid gland and the epithelial component of thethymus (i.e. thymic epithelial cells). | |
| Auditory system | theepithelium of theauditory tube andtympanic cavity | ||
| Urinary system | theurinary bladder and part of theurethra |
Liver andpancreas cells are believed to derive from a common precursor.[5]
In humans, the endoderm can differentiate into distinguishable organs after 5 weeks ofembryonic development.
This article incorporates text in thepublic domain frompage 49 of the 20th edition ofGray's Anatomy(1918)
