4. The adrenal gland consists of
Superficial Cortex
Deeper Medulla
Adrenal cortex and medulla are
two embryologically and
functionally distinct units.
The cells of the cortex arise from
coelomic epithelium (mesoderm).
Cortex -
Mesoderm
The cells of the medulla are
derived from the neural crest
(ectoderm).
Medulla -
Neuroectoderm
Embryology
5. Embryology
Adrenal cortex
Derived from intermediate mesoderm of
urogenital ridge
Formed during 2nd month by a
proliferation of coelomic epithelium. The
cells of the cortex arise from the coelomic
epithelium, that lies in the angle between
the developing gonad and the attachment
of the mesentery.
Beginning in the 5th week of gestation,
mesenchymal cells located at the urogenital
ridge and the root of mesentery proliferate
( form Fetal Adrenal Cortex). The cells
are large and acidophil. They surround
cells of medulla.
6. Adrenal medulla
Derived from Neural Crest Cells (from
somites 18-24), located in
adjacent
sympathetic ganglia.
Neural Crest Cells are similar to
postganglionic sympathetic neurons. Pre-
ganglionic sympathetic neurons terminate in
relation to them
They migrate into medial aspect of fetal
cortex by 9th week of gestation
They continue to invade cortex until they
achieve a central position surrounding the
adrenal vein by 18th week of gestation
this embryologic relationship explains
the brown stippling of adrenal cortex.
Embryology
7. Adrenals InTheNeonate
At term
Each gland weighs 4 g; avg weight of two
glands is 9 g (average in adult is 7-
12 g)
At birth
Adrenals are relatively very large at birth
Constitute 0.2% of entire body weight,
compared with 0.01% in adult
Fetal adrenal gland is twice the weight of
an adult adrenal gland, but has not
completed development.
Left gland is heavier and larger than right,
as in the adult
Cortex is thicker than in adult and medulla
is small.
9. Anatomy
They are paired retroperitoneal organs
composed of a cortex and medulla
Contained in its own sub-compartment
within Gerota’s fascia
Gross examination reveals
Cortex = spiculated, mustard yellow
colour
Medulla = central, brown colour
Weight ~ 4 - 5 g each
Size
Length = 4 - 6 cm
Width = 2 - 3 cm
Right adrenal gland is triangular in shape
Left adrenal gland is crescent shaped
10.
11.
12. Blood supply
Arterial Supply
Receives blood @ 7cc/gm/min
3 arterial sources of flow:
Branches from Inferior Phrenic
ArteryDirect visceral branches from
AortaBranches from I/L Renal Artery
Superior Adrenal A.
Middle Adrenal A.
Inferior Adrenal A.
The main adrenal arteries branch to form a subcapsular plexus
From subcapsular plexus
Some branches continue directly to medulla
Others form sinusoids to cortex
13.
14.
15. Medullary veins coalesce to form adrenal
vein
Adrenal vein is surrounded by medullary
tissue within the gland.
Single main vein on each side
Most important surgical structure
Right adrenal vein
Short
Drains directly into post IVC
Left adrenal vein
Long as compared to right adrenal
vein
Joined by Inferior Phrenic vein prior
to draining into Left Renal Vein
Venous Drainage
16.
17.
18.
19. sympathetic fibers from sympathetic trunk directly to
Nerve Supply
Sympathetic
Medulla
Preganglionic
chromaffincells
Cortex
Postganglionic fibers from splanchnic
ganglia
Parasympathetic to adrenal cortex and medulla
Not well defined
Branches from Vagus nerve may be present
22. Histology
Each adrenal gland is enclosed within a
fibrous capsule
Directly beneath the capsule is the
cortex, which comprises three zones:
Zona Glomerulosa (Outermost
Layer)
Small polyhedral cells with scant
eosinophilic cytoplasm and dark
round nuclei.
Zona Fasciculata
Broad layer of large pale
cells arranged in vertical
columns beneath
glomerulosa
Zona Reticularis (Innermost layer)
Round dark staining cells
23. Normal adrenal histopathology.
A, Low-power view showing the adrenal cortex (C) and medulla (M).
B, Medium-power view demonstrating individual layers of the adrenal cortex. The thickness
of the zona glomerulosa varies along its length (hematoxylin and eosin stain).
