The key difference between somatic and splanchnic mesoderm is that the somatic mesoderm is the outer layer formed after the split of the lateral plate mesoderm. In contrast, the splanchnic mesoderm is the inner layer formed after the split of the lateral plate mesoderm.
The process of gastrulation generates the three primary germ layers: ectoderm, endoderm, and mesoderm. Ectoderm gives rise to the epidermis, external glands, hair, nails, anterior pituitary, and apical ectodermal ridge. Endoderm is responsible for the formation of the gut and associated organs. Mesoderm, on the other hand, is responsible for the formation of the skeletal system, muscular system, excretory system, circulatory system, lymphatic system, and reproductive system. Moreover, the mesoderm further divides into paraxial, intermediate, and lateral plate mesoderms. Therefore, somatic and splanchnic mesoderms are formed by splitting lateral plate mesoderm.
CONTENTS
1. Overview and Key Difference
2. What is Somatic Mesoderm
3. What is Splanchnic Mesoderm
4. Similarities – Somatic and Splanchnic Mesoderm
5. Somatic vs. Splanchnic Mesoderm in Tabular Form
6. Summary – Somatic vs. Splanchnic Mesoderm
What is Somatic Mesoderm?
The somatic mesoderm is the outer layer that is formed after the split of the lateral plate mesoderm. It contributes to the formation of connective tissue in the body wall and limbs. It is also known as somatopleure. The creation of somatic mesoderm occurs during embryogenesis when the lateral plate mesoderm splits into two layers such as somatic and splanchnic mesoderm.
The combination of ectoderm and somatic mesoderm typically forms the amnion, the chorion (membranes that cover the embryo), and the lateral body wall of the embryo. The limb formation from the somatic mesoderm is induced by certain types of genes called hox genes and the expression of other specific molecules. Once the hox genes are activated, the embryonic somatopleure (somatic mesoderm) is divided into three sections: anterior limb bud formation, posterior limb bud formation, and non-limb forming wall. Limb buds are the precursor structures of the limbs. The limb formation generally begins from the 4th week of the pregnancy.
Figure 01: Somatic and Splanchnic Mesoderm
What is Splanchnic Mesoderm?
The splanchnic mesoderm is the inner layer formed after the split of the lateral plate mesoderm associated with the endoderm. This inner lateral plate mesoderm (visceral or splanchnic) layer adheres to the endoderm. It is also known as the splanchnopleure. The splanchnic mesoderm is located external to the coelom (internal body cavity) and the endoderm.
Splanchnic mesoderm usually gives rise to the mesothelial covering of the visceral organs. Splanchnic mesoderm also forms the serous membranes, which surround the viscera and gives rise to heart and blood vessels.
What are the Similarities Between Somatic and Splanchnic Mesoderm?
- Somatic and splanchnic mesoderm are two types of lateral plate mesoderm.
- The splitting of lateral plate mesoderm forms somatic and splanchnic mesoderm.
- Both are formed in the 4th week of pregnancy.
- They perform essential functions in the human embryo.
What is the Difference Between Somatic and Splanchnic Mesoderm?
The somatic mesoderm is the outer layer formed after the split of the lateral plate mesoderm. In contrast, the splanchnic mesoderm is the inner layer formed after the split of the lateral plate mesoderm. Thus, this is the key difference between somatic and splanchnic mesoderm. Furthermore, somatic mesoderm is attached to the ectoderm, while splanchnic mesoderm is attached to the endoderm.
The infographic below presents the differences between somatic and splanchnic mesoderm in tabular form for side-by-side comparison.
Summary – Somatic vs. Splanchnic Mesoderm
Lateral plate mesoderm is a type of mesoderm. It forms the progenitor cells that make the developing embryo’s heart, cardiovascular system, blood, kidneys, smooth muscle lineage, limbs, and skeleton. The lateral plate mesoderm splits into two layers: somatic and splanchnic mesoderm. The somatic mesoderm is the outer layer that is formed after the split of the lateral plate mesoderm. In contrast, the splanchnic mesoderm is the inner layer formed after the split of the lateral plate mesoderm. Furthermore, somatic mesoderm is attached to the ectoderm, while splanchnic mesoderm is attached to the endoderm. So, this summarizes the difference between somatic and splanchnic mesoderm.
Reference:
1. “Mesoderm: Video, Anatomy, Definition & Function.” Osmosis.
2. “Splanchnic Mesoderm.” LifeMap Discovery®.
Image Courtesy:
1. “Gray31” By By Henry Vandyke Carter – Henry Gray (1918) Anatomy of the Human Body – Bartleby.com: Gray's Anatomy, Plate 31 (Public Domain) via Commons Wikimedia