The third ventricle is a midline cavity situated between the two thalami and hypothalamus. It extends from the lamina terminalis anteriorly to the cerebral aqueduct posteriorly. The third ventricle has anterior, posterior, roof, floor and lateral walls formed by surrounding structures like the thalamus, hypothalamus, pineal gland and others. It has recesses that extend into surrounding structures like the infundibular recess into the pituitary stalk. The pineal gland is a small reddish-grey structure located between the superior colliculi that secretes the hormone melatonin and is involved in biological functions like sleep-wake cycles.

1. Dr. Rati Tandon
J.N.M.C.,AMU,
ALIGARH

2. THIRD VENTRICLE
IT IS CAVITY WITHIN
DIENCEPHALON.
DIENCEPHALON: is a
part of brain between
the cerebrum and the
brainstem.

3. Pars dorsalis: (a) thalamus,
(b) metathalamus: the medial and
lateral geniculate bodies, and
(c) epithalamus: pineal body (gland),
Pars ventralis: (a) subthalamus, and
(b) hypothalamus.

4. It is a midline slit-like cavity situated between the
two thalami and the part of hypothalamus.

5. Communications

6. It extends from the lamina terminalis anteriorly to
the superior end of the cerebral aqueduct of midbrain
posteriorly. The cavity of third ventricle is lined by a
ciliated columnar epithelium, the ependyma.

7. Boundaries
The third ventricle has-
Anterior wall,
Posterior wall,
Roof,
Floor, and
Two lateral walls.

8. Anterior wall is formed from
above downwards by:
– anterior column of fornix,
– anterior commissure, and
– lamina terminalis.

9. Posterior wall is formed
from above downwards
by,
– pineal gland,
– posterior commissure,
and
– commencement of
cerebral aqueduct.

10. Roof is formed by the ependyma that stretches across
the upper limits of two thalami.

11. Floor is formed from
before backwards by,
– optic chiasma,
- infundibulum (pituitary
stalk),
– mammillary bodies,
– posterior perforated
substance, and
– tegmentum of the
midbrain.

13. Lateral wall is marked by a curved sulcus, the
hypotha-lamic sulcus extending from the
interventricular foramen to the cerebral aqueduct.

14. The sulcus divides the
lateral wall into:
a larger upper part and
smaller lower part.
• The larger upper part
formed by the medial
surface of anterior two
third of the thalamus.
• The smaller lower part of
the lateral wall is formed
by the hypothalamus.

15. Recesses of the Ventricle
The cavity of third ventricle extends into the
surrounding structures as a pocket-like protrusion
called recesses.

16. These are as follows:
1. Infundibular recess. It is
a deep tunnel-shaped
recess extending
downwards into the
infundibulum, i.e. the stalk
of the pituitary gland.
2. Optic (or chiasmatic)
recess. It is angular recess
situated at the junction the
anterior wall and the floor
of the ventricle just above
the optic chiasma.

17. 3. Anterior recess (vulva
of ventricle). It is a
triangular recess which
extends anteriorly in
front of interventricular
foramen.

18. 4. Suprapineal recess. It is
a fairly capacious blind
diverticulum which
extends posteriorly above
the stalk of pineal gland.
5. Pineal recess. It is a small
diverticulum, which
extends posteriorly
between the superior and
inferior laminae of the
stalk of the pineal gland.

19. Pineal gland (epiphysis cerebri)
 midline cone-shaped reddish grey structure (only 3
mm × 5 mm in size)
between the two superior colliculi below the
splenium of corpus callosum.

20. It has a stalk which divides into two laminae.
The extension of the cavity of third ventricle between
the two laminae is termed pineal recess.

21. The pineal gland is supplied by a nerve called nervus
con-arii, which consists of postganglionic sympathetic
fibres arising from superior cervical sympathetic
ganglion.

22. Structure
neuroendocrine gland.
Consists: parenchymal cells called pinealocytes, and
neuroglial cells.
secrete a hormone called melatonin.

23. Functions
 seat of soul
dorsal third eye
 biological clock for physiological and behavioural
control.
Regulates sleep wake cycle.
secretes a hormone, melatonin. inhibits secretion of
gonadotrophins (GnRH) from hypothalamus.

24. Clinical Correlation
 The lesions of the pineal gland are associated with
precocious puberty.
The calcification of the pineal gland is demonstrable
radiologically in more than 50% of normal adults. It
lies in midline or midsagittal plane of the skull, and is
about 5 cm above the external auditory meatus, in
lateral view of the X-ray skull.

25. THANK YOUTHANK YOU