The pineal gland is a midline structure involved in the regulation of circadian rhythm. The "internal clock" that allows for coordination of sleep and wake cycles with changes in night and day is largely regulated by the actions of melatonin, a neurotransmitter that is produced by the constituent cell of the pineal gland: the pinealocyte. Pinealocytes give rise to a rare group of tumors... Continue Reading →
Dorsal Root Ganglion
The dorsal root ganglia consist of the cell bodies of sensory afferent neurons and are located along either side of the spinal cord. These unipolar neurons characteristically have large cell bodies, which are needed to support the very long axons that carry sensory information from the distal extremities to the cord. Normal ganglia (such as the one... Continue Reading →
Fetal Gyral Development
During the first half of gestation, the human fetal brain has a smooth surface. At about 20 weeks gestation, the brain begins to form the bumps (gyri) and grooves (sulci) that are typical of the adult brain, averaging about 1 sulcus per week of gestation after 20 weeks. The brain of this 25 week gestation... Continue Reading →
Cortical Atrophy in an Elderly Person (90 years old)
A normal adult loses about 0.2% of brain volume every year after middle age. Compared to young and middle-aged adults, the brains of the elderly have comparatively widened sulci, narrowed gyri, a thin cortical ribbon, and enlarged ventricles due to progressive brain volume loss, which, clinically, may contribute slower processing speed for cognitive tasks and other changes. Microglia-mediated synaptic pruning and other etiologies for decreasing cortical volume in the... Continue Reading →
Premature Fetal Brain
The brain of a premature fetus, shown here (front of brain pointing to the left) is initially smooth in the early stages of development. After about 20 weeks gestation, grooves develop in the cortical surface that gradually become more defined until they form well delineated gyri and sulci (i.e. bumps and grooves) typical of a mature brain. The brain... Continue Reading →
This image of a nerve root shows axons myelinated by oligodendroglial cells of the central nervous system (top of image) and Schwann cells of the peripheral nervous system (bottom of image) at a point of transition called the Obersteiner-Redlich zone.
Coronal Section of a Fetal Brain
Coronal section of a fetal brain, approximately 21 weeks gestational age, with edema. Notice how, unlike in adult brains, there is no apparent delineation between white matter and grey matter due to incomplete myelination of the immature brain.
Dorsal Root Ganglia
Dorsal root ganglia are located along the length of the spinal cord and are composed of clusters of large neuron cell bodies, each with a prominent nucleus and nucleolus, that belong to sensory nerves whose axons deliver sensory information to the spinal cord.
Astrocytes and the Blood Brain Barrier
Astrocytes, like the one highlighted here by GFAP stain, are star-shaped glial cells that are involved in a large number of CNS functions, including the blood brain barrier. Together with pericytes and endothelial cells, astrocyte end plates surrounding a vessel forms an essential component of the blood brain barrier which severely limits passage of certain... Continue Reading →