DEVELOPMENT OF THE ADRENAL GLAND IN THE CROSSBRED GOAT
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Date
1999
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COLLEGE OF VETERINARY AND ANIMAL SCIENCE,MANNUTHY
Abstract
Studies on the prenatal and postnatal development of the
adrenal gland in crossbred gosts were conducted using 55
embryos/foetuses of varying gestational ages and 45 goats from
day old to 180 days postpartum. The project was taken up to
trace the normal growth and developmental pattern of the
glands and their relationship with age, body weight and the
physiological status.
After recording gross relations and measurements, the
material was fixed using various fixatives for studying the
cellular details, arrangement of cells, connective tissue
framework, micrometry and histochemistry.
The glands attained their characteristic shapes even
during early development and were located cranial to the
kidneys in the retroperitoneum. During the prenatal period
v/eight of the adrenals increased steadily upto 141 days
followed by a spurt thereafter due to the hypertrophy and
hyperplasia of the cortex. After birth also an increasing
trend was noticed in adrenal weight from birth to 180 days
with a slight decrease at 45 days. The glandular weight was
positively correlated with age and body weight. The
proportion of the adrenal to body weight percentage shov/ed a
decreasing trend in both the groups studied. The deft gland
was slightly heavier and longer tljan the right while the right
one was broader and thicker. The length, breadth and
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thickness were positively correlated with the age of foetuses
and kids.
The cortical primoridum was first detected at 33 days of
embryonic development. By 36 days, these cells began to
organize into cords and dense aggregations. Though a thin
collagenous capsule began to develop by 42 days, it became
conspicuous with outer more fibrous and inner more cellular
layers by 70 days. Reticular fibres appeared by 58 days and
elastic fibres by 74 days of foetal life.
By 42 days, histological differentiation started with
organization of cells into small groups and clusters
separated by irregular spaces. The central vein also started
development at this stage. Differentiation of zona
glomerulosa was noticed by 58 days and was completed by 95
days. Zona fasciculata and zona reticularis became apparent
by 129 days. A distinct corticomedullary junction appeared at
95 days eventhough interdigitations of cortex and medulla were
seen at the junction throughout the study period. Towards the
centre of the gland interroingling of cortical and'medullary
cells were seen upto 104 days. Patches of cortical cells were
seen in the medullary region and also around the central vein
throughout the period of study. Neural crest cells invaded
the cortical primordium by 50 days and this process was
completed by 70 days. Chromaffin reaction appeared in the
medullary cells by 50 days. Eventhough norepinephrine cells
were detected in the gland at this stage, epinephrine cells
made their presence only by 98 days. Follicles containing
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colloid material were encountered in the medulla during both
the advanced foetal and the postnatal periods.
In goats, the glands were covered by highly vascular
connective tissue capsule composed of collagen, reticular and
elastic fibres with a few smooth muscle cells. An outer more
fibrous and an inner more cellular layers were recognizable.
The capsule contained undifferentiated cells, differentiated
cortical type cells, fibroblasts, neurons and melanocytes.
The parenchyma was divisible into a cortex and a
medulla. Cortex was further subdivided into zona glomerulosa,
zona fasciculata and zona reticularis. Each zone had
distinct pattern of cellular arrangement and cytological
characteristics. Mast cells were occasionally detected in all
the cortical zones. Mitotic figures were also recorded
throughout the cortex. A zona intermedia was observed between
the zona glomerulosa and the zona fasciculata.
Capsule, trabeculae and the parenchyma were all PAS
positive. Acid mucopolysaccharides and glycogen were also
detected in the cortex. They were seen at varying intensities
in the cortex and medulla of the prenatal and the postnatal
subj ects.
Intensity of phosphatase enzymes was lower in the
cortical cells between third and fourth month of gestation
after which the same increased till term. After birth a
higher activity upto 30 days and a reduced activity at 45 days
v/ere recorded especially in tdie zona fasciculata. Medullary
IV
cells revealed moderate alkaline phosphatase and intense acid
phosphatase activities during the study period.
Lipid was first detected by 50 days, and upto 74 days a
uniform distribution was seen throughout the cortex.
Afterwards, it concentrated more in the clusters of cells in
the subcapsular region. Between 84 and 122 days, a low lipid
content was noticed in the cortical cells, the concentration
of which gradually increased towards term. After 141 days a
heavy accumulation was observed in the cortex. During the
postnatal period, the inner two cortical zones showed heavy
lipid accumulation upto 15 days and a slight depletion at iO
days. This was followed by a very heavy accumulation in all
the three cortical zones at 45 days. Following this, a
gradual depletion was noticed from all the cortical zones.
In the prenatal group, capsular thickness, width of the
entire cortex as well as the various cortical zones and
diameter of the medulla showed positive correlation with
foetal age. In the postnatal group, excepting the width of
zona reticularis, all other parameters were positively
correlated with age. After 135 days of gestation, width of
the cortex, especially of the inner two cortical zones
increased significantly till term.
During postnatal period, a decrease was noticed in the
width of outer two cortical zones by 45 days, however the
diameter of medulla increased steadily upto 180 days. Growth
rate of zona glomerulosa was higher than that of zona
fasciculata till 60 days, after which the latter grew faster.
The medulla grew faster than the cortex upto 45 days and
thereafter no significant difference in growth rates could be
detected.
Percentage contribution of zona glomerulosa to the entire
cortex was more during the foetal period compared to the
postnatal animals. On an average, during the postnatal period
the zona glomerulosa contributed 16.71 per cent, zona
fasciculata 74.16 per cent and zona reticularis 9.13 per cent
to the total cortical width.
It was concluded that the stress induced on the growing
foetus towards the end of gestation due to the insufficiency
of placenta resulted in a higher activity of the cortex,
particularly of the zona fasciculata under the influence of
foetal ACTH. At parturition, exposure of the new born to the
external environment induced severe stress which was
responsible for the higher activity of the gland during early
neonatal period. When the young one got acclimatized to the
new surroundings, the stress was relieved which in turn
resulted in the reduced activity of the gland by 45 days
postpartum.
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