Endocrinology Pineal gland

1. PINEAL GLAND
Submitted by:
Name: Priya padmini Gogoi
Class: B.Sc 5th semester
Roll no.: 25
Department: Zoology
Session: 2022-2023

2. STRUCTURE:
• Pineal gland is a neuroendocrine gland that
regulates daily body rhythms.
• The adult human pineal (epiphysis) is a pinecone
shaped organ.
• This land receives its stimuli through vision;
hence it is called “the third eye”.
• This gland was first discovered by Herophilus.
• Development: It develops from neuroectoderm
of the posterior portion of the roof of the
diencephalon and receives attached to the brain
by a short stalk.
• It is somewhat flattened, cone shaped, grey body
measuring about 5-8mm in length and 3-5mm in
breadth. Fig: microscopic image of t.s. of
pineal gland

3. HISTOLOGY:
• Consist of two types of major cells:- Pinealocytes and interstitial (glial) cells.
• The cells of the pineal are neural in origin, but bear little resemblance to
nerve cells when fully differentiated. Besides these connective tissue cells,
mast cells, Schwan cells and axons of autonomic nerves are also present in
the pineal gland.
i. Pinealocytes or parenchymal cells: They are the chief cells of the pineal
gland. They are arranged in clumps or cords within lobules formed by
connective tissue septa. Pinealocytes have a large deeply infolded
nucleus with one or more prominent nucleoli and contain lipid droplets
within their cytoplasm.
ii. Interstitial (glial) or supportive cells: They constitute about 5% of the
cells in the gland. They lie between clusters of Pinealocytes and in
perivascular spaces. These cells have a dense nucleus, fewer
mitochondria, granular reticulum and free ribosomes.

4. Fig: Pinealocytes Fig: Interstitial (glial) cells

5. HORMONE SECRETION:
• Both melatonin and its precursor serotonin are synthesized in the
pineal gland. Melatonin in secreted by the Pinealocytes cells of the
pineal gland.
• Serotonin is acetylated and methylated to yield melatonin within the
pineal gland.
• Melatonin is secreted in response to darkness, hence the name
“hormone of darkness”.

6. FUNCTIONS OF PINEAL HORMONE
(MELATONIN):
• It plays an influential role in the regulation of sleep cycles.
• It plays a role in regulating the female menstruation cycle.
• Melatonin hormone has a significant effect on affecting circadian
rhythms and integrating photoperiod.
• It also has a significant effect on reproduction and other phenomena
showing circadian rhythms. This hormone is also helpful for children
with development disabilities such as ADHD and autism.
• It is often considered to be the body’s natural pacemaker, as it plays
an instrumental role in signalling time of day and time of year, helping
to regulate our body's internal clock

7. THANKYO
U