Download Anatomy of the Thymus and Tonsils

Anatomy of the Thymus and
Tonsils
Dr Rania Gabr
Thymus
• Roughly a bi-lobed structure
• DEVELOPMENT- bilateral 3rd
pharyngeal pouches
• EVOLUTION- largest at birth or
during infancy
• Increases slightly during 1st
decade of life and decreases
thereafter.
Thymus
Introduction
It is a flattened lymphoid organ located in the
upper anterior mediastinum & lower part of
the neck
Thymus
It consists of two
lateral lobes placed
in close contact
along the middle
line, situated partly
in the thorax, partly
in the neck.
It is covered by the Con . .
sternum, Below, it
rests upon the
pericardium, being
separated from the
aortic arch and great
vessels by a layer of
fascia
In the neck it lies on
the front and sides of
the trachea.
The two lobes generally differ in size;
they are occasionally united, so as to
form a single mass; and sometimes
separated by an intermediate lobe.
The thymus is of a pinkish-gray color,
soft, and lobulated on its surfaces. It
is about 5 cm. in length, 4 cm. in
breadth below, and about 6 mm. in
thickness.
At birth it weighs about 15 grams, at
puberty it weighs about 35 grams;
after this it gradually decreases to 25
grams at twenty five years, less than
15 grams at sixty, and about 6 grams
at seventy years.
Blood SupplyVasculature
A rich arterial supply to the thymus is derived
mainly from the:
1.Anterior intercostal &
2.A.mediastinal branches of the internal
thoracic arteries
 Veins of the thymus end in the left
brachiocephalic, internal thoracic & inferior
thyroid veins.
 The lymphatic vessels of the thymus end in
the parasternal, brachiocephalic &
tracheobrochial lymphnodes.
The Tonsils
Definition: Ovoid lymphoid tissue
with fibrous capsule
laterally over the superior
constrictor muscles.
Its surface is covered with
stratified squamous
epithiluim & crypts.
It has a medulla & cortex
like all other lymphoid
tissues.
It is part of the Walderyers
ring.
The Tonsils
Waldeyer's ring is a continuous band
of lymphoid tissue that surrounds the
upper pharynx.
The superior portion of the ring is
located in the nasopharynx and is
composed of the adenoids, Laterally
the palatine tonsils and, Anteriorly
the lingual tonsils to complete the
ring.
Tonsillar crypts extend deeply into
the body of the tonsil and are
surrounded by lymphoid nodules.
Debris and foreign particles collect
within the crypts.
• The primary follicles are
formed during embryonic
development and differentiate
into secondary follicles after
birth.
• The secondary follicles mainly
contain B lymphocytes at
various stages of
differentiation, along with
scattered T lymphocytes.
• Tonsillar tumors or infections
may result in ear pain due to
referred pain conducted by
cranial nerve IX:
Glossopharyngeal nerve.
• Function:
• Concerned with immune
mechanism.
• - 1st line of defense. The
lymphoid tissues produce
lymphocytes.
• - T-cells produce plasma cells &
help in antibody formation.
• Active phase lasts until 8-10
years of age.
• This function should not alter the
decision to remove the tonsils if
a valid indication for
tonsillectomy exists.
Blood Supply:
Arterial supply:
- Tonsilar branch of facial artery from
the ext. carotid.
- Descending palatine -------- > internal
maxillary artery.
- Ascending palatine -------- facial artery
- Ascending pharyngeal ---- external
carotid.
- Dorsalis linguae ------- lingual artery
Venous drainage :
occurs through the Para
tonsillar vein, and the
vessels also pass through
to the pharyngeal plexus
or facial vein after
piercing the superior
constrictor.
Nerve supply :
to the tonsil is from the
glossopharyngeal nerve.
“
The End ”
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