The myelencephalon or afterbrain is the most posterior region of the embryonic

hindbrain The hindbrain, rhombencephalon (shaped like a rhombus) is a developmental categorization of portions of the central nervous system in vertebrates. It includes the medulla, pons, and cerebellum. Together they support vital bodily processes. Met ...

, from which the

medulla oblongata The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (involun ...

develops. Myelencephalon is from myel- (bone marrow or spinal cord) and encephalon (the vertebrate brain).

Development

Neural tube to myelencephalon

During fetal development, divisions of the

neural tube In the developing chordate (including vertebrates), the neural tube is the embryonic precursor to the central nervous system, which is made up of the brain and spinal cord. The neural groove gradually deepens as the neural folds become elevated, ...

that give rise to the hindbrain (

rhombencephalon The hindbrain, rhombencephalon (shaped like a rhombus) is a developmental categorization of portions of the central nervous system in vertebrates. It includes the medulla, pons, and cerebellum. Together they support vital bodily processes. Met ...

) and the other primary vesicles (

forebrain In the anatomy of the brain of vertebrates, the forebrain or prosencephalon is the rostral (forward-most) portion of the brain. The forebrain controls body temperature, reproductive functions, eating, sleeping, and the display of emotions. Ve ...

and

midbrain The midbrain or mesencephalon is the uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons. It consists of the cerebral peduncles, tegmentum, and tectum. It is functionally associated with vision, hearing, mo ...

) occur 28 days after conception. With the exception of the midbrain, these primary vesicles undergo further differentiation at 5 weeks after conception to form the myelencephalon and the other secondary vesicles.

Myelencephalon to medulla

The final shape differentiation of the myelencephalon into the

can be observed at 20 weeks of gestation.Carlson, Neil R. Foundations of Behavioral Neuroscience.63-65 {, {, {, class="wikitable plainrowheaders sortable" , Neural Tube , Primary Vesicles , Secondary Vesicles , Adult Structures , - , rowspan="5" , Brain , rowspan="2" ,

Forebrain In the anatomy of the brain of vertebrates, the forebrain or prosencephalon is the rostral (forward-most) portion of the brain. The forebrain controls body temperature, reproductive functions, eating, sleeping, and the display of emotions. Ve ...

, Telencephalon , Rhinencephalon, Amygdala, Hippocampus, Cerebrum(Cortex), Basal Ganglia,Lateral ventricles , - ,

Diencephalon In the human brain, the diencephalon (or interbrain) is a division of the forebrain (embryonic ''prosencephalon''). It is situated between the telencephalon and the midbrain (embryonic ''mesencephalon''). The diencephalon has also been known as t ...

, Epithalamus, Thalamus, Hypothalamus, Subthalamus, Pituitary, Pineal, Third ventricle , - ,

Midbrain The midbrain or mesencephalon is the uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons. It consists of the cerebral peduncles, tegmentum, and tectum. It is functionally associated with vision, hearing, mo ...

, Mesencephalon , Tectum, Cerebral peduncle, Pretectum, Cerebral aqueduct , - , rowspan="2" ,

Hindbrain The hindbrain, rhombencephalon (shaped like a rhombus) is a developmental categorization of portions of the central nervous system in vertebrates. It includes the medulla, pons, and cerebellum. Together they support vital bodily processes. Met ...

, Metencephalon , Pons, Cerebellum , - , Myelencephalon , Medulla Oblongata , - , colspan="4" , Spinal cord 1302 Brain Vesicle DevN

Medulla oblongata

The

is part of the brain stem that serves as the connection of the spinal cord to the brain. It is situated between the

pons The pons (from Latin , "bridge") is part of the brainstem that in humans and other mammals, lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum. The pons is also called the pons Varolii ("bridge of ...

and the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

Function

The medulla oblongata is responsible for several functions of the

autonomic nervous system The autonomic nervous system (ANS), sometimes called the visceral nervous system and formerly the vegetative nervous system, is a division of the nervous system that operates viscera, internal organs, smooth muscle and glands. The autonomic nervo ...

. These functions include: 1) Respiration: monitors the acidity of the blood and sends electrical signals to intercostal muscle tissue to increase their contraction rate in order to oxygenate the blood as needed. 2) Cardiac & Vasomotor Center: monitors and regulates cardiovascular activities by: * Sympathetic excitation in order to increase cardiac output * Parasympathetic inhibition of cardiac output * Affecting blood pressure via

vasodilation Vasodilation, also known as vasorelaxation, is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. Blood vessel wa ...

and

vasoconstriction Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vesse ...

3) Reflexes * Coughing * Sneezing * Swallowing (palatal) * Vomiting * Gagging (pharyngeal) * Jaw jerk (masseter)

Damage/trauma

Because of its location in the

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...

and its many important roles in the autonomic nervous system, damage to the medulla oblongata is usually fatal.

References

{{Authority control Animal developmental biology