Pineal gland

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Status

Done

Parent item

Epithalamus

General

• Aka: Epiphysis Cerebri

• A small piriform structure

Location

• Forms posterior wall of the third ventricle of the brain

• The attachment of the pineal body to the posterior wall of the third ventricle is through a stalk that has two laminae:
• Superior lamina: traversed by fibres of the habenular commissure
• Inferior lamina: traversed by fibres of the posterior commissure

Consist of

• Pinealocytes
• Atrophied/vestigial photoreceptors
• Disease: Trilateral retinoblastoma
• Bilateral retinoblastoma
• Pineloblastoma

• Glial cells
• Separated pinealocytes
• Resemble astrocytes in structure.

• Sympathetic nerve endings

Connection

Function:

Pinealocyte function

• Endocrine gland

• Produces a number of hormones (chemically indolamines or polypeptides) that regulate many endocrine organs
• Somatostatin → (inhibit GH) Pituitary gland
• Through
• Blood
• CSF
• TSH → Thyroid gland
• LHRH → Gonads
• Regulate the onset of puberty
• Over secretion: delays puberty
• Under secretion: precocious puberty

• Melatonin
• Production
• By pinealocytes
• 5HT → Melatonin

• Max during dark to facilitate sleep
• Circadian rhythm secre­tion of the hormone melatonin
• Light on retina → through extra geniculate pathways suprachiasmatic nucleus (SCN) of hypothalamus is activated → signal through medial forebrain bundle (MFB) → intermediolateral spinal cord cell column (IML) C8-T1 which has preganglionic sympathetic neuron → superior cervical ganglia (post ganglionic neuron) → up the sympathetic carotid plexus → release norepinephrine → Inhibits pinealocytes
• Innervated by postganglionic sympathetic neurons located in the superior cervical sympathetic ganglia.
• Pathway:
• 1st neuron: Superior cervical sympathetic ganglia → nervus conarii → end in the habenular nuclei
• 2nd neuron: From habenular nuclei → habenulopineal tract → pineal gland
• A ganglion (ganglion conarii) has been described at the apex of the pineal body.