[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Embryology](https://durgical.com/en/embryology/) › [Nervous system and senses](https://durgical.com/en/embryology/#a-nervous) › Brain vesicles: from three to five and what each becomes [Embryology](https://durgical.com/en/embryology/) · [Nervous system and senses](https://durgical.com/en/embryology/#a-nervous) # Brain vesicles: from three to five and what each becomes - Embryonic structure The head end of the neural tube swells into three vesicles that then split into five; the whole brain grows from them. Updated 2026-11-01 **See it in 3D:** [Midbrain](https://durgical.com/en/anatomy/midbrain/) · [Pons](https://durgical.com/en/anatomy/pons/) · [Medulla oblongata](https://durgical.com/en/anatomy/medulla-oblongata/) · [Cerebellum](https://durgical.com/en/anatomy/anterior-quadrangular-lobule/) · [Thalamus](https://durgical.com/en/anatomy/thalamus/) · [Hypothalamus](https://durgical.com/en/anatomy/hypothalamus/) · [Pineal gland](https://durgical.com/en/anatomy/pineal-gland/) · [Frontal lobe](https://durgical.com/en/anatomy/superior-frontal-gyrus/) · [Lateral ventricles](https://durgical.com/en/anatomy/lateral-ventricle/) · [Third ventricle](https://durgical.com/en/anatomy/third-ventricle/) · [Cerebral aqueduct](https://durgical.com/en/anatomy/aqueduct-of-midbrain/) · [Fourth ventricle](https://durgical.com/en/anatomy/fourth-ventricle/) ## Key points - 3 primary (week 4) → 5 secondary (week 5). - Diencephalon → thalamus, hypothalamus, neurohypophysis and retina. - Metencephalon → pons and cerebellum; myelencephalon → medulla. - The mesencephalon is the only vesicle that does not split; its cavity is the aqueduct. - Each vesicle gives a ventricle: lateral, third, aqueduct, fourth. ## What it is The brain vesicles are the swellings of the cranial end of the neural tube. Three primary vesicles are present in week 4 and five secondary vesicles by week 5, each with an adult fate and a cavity that becomes a ventricle. This sequence explains brain anatomy, the ventricular system and malformations such as holoprosencephaly. ## Key facts - Week 4: after the anterior neuropore closes, the prosencephalon, mesencephalon and rhombencephalon form. - Week 5: the prosencephalon splits into telencephalon and diencephalon, the rhombencephalon into metencephalon and myelencephalon; the mesencephalon does not split. - The lumen of the neural tube persists as the ventricular system and, in the cord, as the central canal. - Three flexures appear: cephalic (at the midbrain), cervical (between hindbrain and cord) and pontine. - The optic vesicles bud from the diencephalon: the retina and optic nerve are, by origin, part of the brain. - The brainstem (midbrain, pons, medulla) keeps alar and basal plates like the cord; the hemispheres and cerebellum expand mainly the alar plates. ## Structure - A wall with three layers: ventricular (proliferating neuroepithelium), mantle (future gray matter) and marginal (future white matter). - In the brainstem the sulcus limitans separates the alar plate (sensory, dorsal) from the basal plate (motor, ventral). - The rhombencephalic isthmus marks the midbrain–hindbrain boundary, a key organizing center. ## What it becomes - Telencephalon: cerebral hemispheres, basal nuclei, olfactory bulbs. - Diencephalon: thalamus, hypothalamus, epithalamus with the pineal gland, neurohypophysis, retina and optic nerve. - Mesencephalon: adult midbrain (superior and inferior colliculi, cerebral peduncles). - Metencephalon: pons and cerebellum. - Myelencephalon: medulla oblongata. ## From primary vesicle to adult structure | Primary | Secondary | Adult structures | Cavity | | --- | --- | --- | --- | | Prosencephalon | Telencephalon | Hemispheres, basal nuclei | Lateral ventricles | | Prosencephalon | Diencephalon | Thalamus, hypothalamus, neurohypophysis, retina | Third ventricle | | Mesencephalon | Mesencephalon | Midbrain (colliculi, peduncles) | Cerebral aqueduct | | Rhombencephalon | Metencephalon | Pons, cerebellum | Fourth ventricle (upper part) | | Rhombencephalon | Myelencephalon | Medulla oblongata | Fourth ventricle (lower part) | | Caudal neural tube | (no vesicle) | Spinal cord | Central canal | ## Markers - SHH - FGF8 - OTX2 - GBX2 - EN2 - HOX ## Clinical notes - If the prosencephalon fails to split into two hemispheres, holoprosencephaly results. - A narrow aqueduct (midbrain) is the most common cause of congenital hydrocephalus. - Defects of the hindbrain and cerebellum underlie Chiari and Dandy–Walker malformations. ## Memory aid Picture three siblings who have five children: the middle one (mesencephalon) stays single, while the two outer ones each have twins (tele/dien and met/myel). ## Test yourself Think of the answer, then tap the question to see it. ## Which secondary vesicle gives rise to the pons and cerebellum? The metencephalon, the cranial part of the rhombencephalon. ## Which primary vesicle does not subdivide, and what cavity does it leave? The mesencephalon; its lumen narrows into the cerebral aqueduct. ## Which vesicle do the retina and neurohypophysis come from? The diencephalon: the optic vesicle and the infundibulum are outgrowths of its wall. ## In which weeks do three vesicles become five? The three primary vesicles are seen in week 4 and the five secondary vesicles in week 5. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/embryology/brain-vesicles-from-three-to-five-and-what-each-becomes/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Midbrain](https://durgical.com/en/anatomy/midbrain/) - [Pons](https://durgical.com/en/anatomy/pons/) - [Medulla oblongata](https://durgical.com/en/anatomy/medulla-oblongata/) - [Cerebellum](https://durgical.com/en/anatomy/anterior-quadrangular-lobule/) - [Thalamus](https://durgical.com/en/anatomy/thalamus/) - [Hypothalamus](https://durgical.com/en/anatomy/hypothalamus/) - [Pineal gland](https://durgical.com/en/anatomy/pineal-gland/) - [Frontal lobe](https://durgical.com/en/anatomy/superior-frontal-gyrus/) - [Lateral ventricles](https://durgical.com/en/anatomy/lateral-ventricle/) - [Third ventricle](https://durgical.com/en/anatomy/third-ventricle/) - [Cerebral aqueduct](https://durgical.com/en/anatomy/aqueduct-of-midbrain/) - [Fourth ventricle](https://durgical.com/en/anatomy/fourth-ventricle/) ## Related - [Neurulation and closure of the neural tube](https://durgical.com/en/embryology/neurulation-and-closure-of-the-neural-tube/) - [Spinal cord: alar and basal plates and the ascent of the cord](https://durgical.com/en/embryology/spinal-cord-alar-and-basal-plates-and-the-ascent-of-the-cord/) - [Ventricles and cerebrospinal fluid](https://durgical.com/en/embryology/ventricles-and-cerebrospinal-fluid/) - [Holoprosencephaly](https://durgical.com/en/embryology/holoprosencephaly/) - [Neural tube defects: anencephaly, spina bifida and encephalocele](https://durgical.com/en/embryology/neural-tube-defects-anencephaly-spina-bifida-and-encephalocele/) - [Eye: optic vesicle, optic cup and lens](https://durgical.com/en/embryology/eye-optic-vesicle-optic-cup-and-lens/) - [Pituitary gland: Rathke pouch and the neurohypophysis](https://durgical.com/en/embryology/pituitary-gland-rathke-pouch-and-the-neurohypophysis/) ## Related conditions - [Hydrocephalus](https://durgical.com/en/conditions/hydrocephalus/) [← All of embryology](https://durgical.com/en/embryology/) Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given. Sources: [13.1 The Embryologic Perspective - Anatomy and Physiology 2e](https://openstax.org/books/anatomy-and-physiology-2e/pages/13-1-the-embryologic-perspective) (OpenStax, 2022); [Fetal development: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/002398.htm) (U.S. National Library of Medicine, 2024); Langman's Medical Embryology, 13th ed., ch. 18: Central Nervous System (Wolters Kluwer, 2015). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/embryology/brain-vesicles-from-three-to-five-and-what-each-becomes/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/embryology/brain-vesicles-from-three-to-five-and-what-each-becomes/