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Brain Embryogenesis

For medical students2 min readUpdated 2026-10-10

The brain develops from the cranial (anterior) part of the neural tube. Embryogenesis is based on gradual morphological complexity: from the formation of simple expansions to the creation of a highly complex system of distinct cell masses and internal cavities.

Source of developmentCranial part of the primary neural tube
Main stagesSequential transition from three primary brain vesicles to five
CavitiesTransform into the ventricular system and the cerebral aqueduct
Description vectorStructures are typically reviewed in a caudal-to-cranial direction

General Principles of Development and Histogenesis

The formation of the brain is an orderly process in which the initial cylindrical structure undergoes significant changes. The nervous tissue itself develops intensively from the walls of the primary expansions.

As cellular growth and tissue mass increase, the internal lumens of the primordia become relatively smaller. In the mature organ, these residual spaces persist and function as the brain ventricles and connecting channels (the aqueduct).

Transition from Three Vesicles to Five

The morphological division of the cranial end of the neural tube occurs in two main stages:

  1. Three-vesicle stage. Primary segregation occurs due to the formation of transverse constrictions. At this stage, three major segments are distinguished: the forebrain (Prosencephalon), midbrain (Mesencephalon), and hindbrain (Rhombencephalon).
  2. Five-vesicle stage. This arises at later stages due to the appearance of additional longitudinal flexures. During this period, the terminal primordia (anterior and posterior) divide in two. The middle vesicle does not undergo division and remains single. Ultimately, five distinct parts are formed, giving rise to all structures of the mature brain.

Anatomical Derivatives of the Brain Vesicles

The formed brain consists of five consecutive parts. Traditionally, they are examined in a caudal-to-cranial direction — that is, from bottom to top, starting from the border with the spinal cord.

Hindbrain (in the broad sense)

Develops from the primary hindbrain vesicle (Rhombencephalon), whose general cavity transforms into the fourth ventricle.

Midbrain

Develops from the single middle vesicle.

Forebrain (in the broad sense)

Forms from the structures of the primary forebrain vesicle (Prosencephalon).

Primary Vesicle5-Part StageMain StructuresCavity
Hindbrain (Rhombencephalon)Myelencephalon, MetencephalonMedulla oblongata, pons, cerebellumFourth ventricle
Midbrain (Mesencephalon)MesencephalonCerebral peduncles, tectumCerebral aqueduct
Forebrain (Prosencephalon)Diencephalon, TelencephalonThalamus, hypothalamus, cerebral hemispheresBrain ventricles

Mnemonic

It is easy to remember the direction of forebrain differentiation: it gives rise to the "highest authorities" — the Diencephalon and Telencephalon.

Frequently asked questions

What structures develop from the diencephalon?

The following structures develop from the diencephalon:

  • Thalamus;
  • Epithalamus — includes the pineal gland and habenular nuclei;
  • Metathalamus;
  • Subthalamus — includes the subthalamic nucleus;
  • Hypothalamus — hypothalamic region.
What do the cavities of the prosencephalon turn into?

The cavities of the forebrain vesicle turn into the ventricles of the brain. Specifically, they form:

  • Lateral ventricles (first and second) — in both halves of the telencephalon;
  • Third ventricle — in the diencephalon.
What derivatives does the telencephalon give rise to?

The telencephalon is represented by the right and left cerebral hemispheres (hemispheria cerebri). It includes:

  • Cerebral cortex (cortex cerebri, pallium) — the mantle;
  • Rhinencephalon (olfactory brain);
  • Basal nuclei (nuclei basales) — subcortical nuclei;
  • White matter — projection and association pathways;
  • Lateral ventricles (ventriculi laterales) — the cavities of the telencephalon.
From which germ layer does the primary neural tube develop?

The primary neural tube develops from the ectoderm (neuroectoderm). During neurulation, under the inductive influence of the notochord, the neural plate forms within the ectoderm, bends to form the neural groove, and its edges subsequently fuse into a closed neural tube that separates from the surface ectoderm.

What forms the nervous tissue of the brain during embryogenesis?

Nervous tissue develops directly from the thickening walls of the brain vesicles, which form at the cranial end of the neural tube.

What do the cavities of the primary brain vesicles turn into?

They transform into the internal cerebrospinal fluid (CSF) system: the brain ventricles and the connecting cerebral aqueduct. Meanwhile, the dimensions of the cavities decrease relative to the active growth of the nervous tissue.

Which structures develop from the middle brain vesicle?

The middle vesicle does not divide during the five-vesicle stage. The entire midbrain (Mesencephalon) forms from it, including the cerebral peduncles and the tectum.

What is the role of the thalamus, which develops from the diencephalon?

The thalamus consists of large paired clusters of gray matter that serve as the main relay station. Almost all afferent (sensory) pathways traveling to higher brain regions are relayed here.

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