Anatomy - Gracey's Meat Hygiene - page 35

if the animal is in calf and regress in the non-pregnant
uterus, that is, that the animal must have been at least
3½ months or longer in calf.

Endocrine system
The endocrine or ductless glands (thyroid, parathyroids
thymus, adrenals and gonads, i.e. testes and ovaries)
produce secretions or hormones which pass directly
into the bloodstream to act on another organ or tissue.
The liver and pancreas are both endocrine and exo-
crine glands, each possessing ducts, and are usually
described with the digestive system. ( Exocrine glands
such as the sweat, mammary and lachrymal glands
pass their secretions along ducts to the surface of the
body.)

Ewe
The uterine horns are relatively long, the cotyledons
being circular, pigmented and much smaller than in the
cow, while in advanced pregnancy, the centre of each is
cupped or umbilicated.

Gilt and sow
The uterine horns are very long and arranged in coils. The
mucous membrane has no cotyledons but is arranged in
numerous thin longitudinal folds. The ovaries are rounded
with an irregularly lobulated surface. The sow and gilt
carcase may be differentiated not only by the develop-
mental condition of the udder and teats but also by exami-
nation of the uterine arteries. In the sow, the udders are
enlarged, and in the broad ligaments of the uterine horns,
the peripheral branches of the uterine middle arteries are
torturous owing to pregnancy. In the gilt, these arterial
vessels are less apparent and almost straight. Characteristic
histological changes also take place in the uterine arteries
during and after pregnancy; there is hyperplasia of the
elastic fibres in the intima and media of the vessel wall,
the intima is hypertrophied, and the internal elastic lam-
ina is split into two or more layers. Similar changes can
be observed in the arteries supplying the ovary.

Thymus
The thymus is pinkish white and distinctly lobulated and
constitutes the true sweetbread . It consists of two por-
tions; the thoracic portion (heart bread) is rich in fat and
roughly the shape of the palm of the hand in the ox and
lies in the thoracic cavity, extending back to the third rib
where it contacts the base of the heart; the second por-
tion (neck bread) is poor in fat and consists of two lobes
joined at their base and extending up the neck on either
side of the trachea, diverging and diminishing in size as
they pass up the neck and reaching almost to the thyroid
gland.
In the calf , the thymus is at its largest at 5-6 weeks,
when it weighs 453-680 g, but gradually atrophies. By
the onset of sexual maturity, little of the cervical portion
remains. It is very small in 3-year-old cattle, but a vestige
of the thoracic portion may be seen in cows even after 8
or 9 years. In the pig , the thymus is large and greyish yel-
low and reaches to the throat.
In early life, the thymus is necessary for the develop-
ment of certain immune responses and antibodies. It is
probably also associated with lymphocyte production. If
this is removed shortly after birth, the production of
lymphocytes, lymphoid tissue and plasma cells is much
reduced; antibodies are not formed; and skin grafts, even
from different species, are not rejected. Since no hor-
mone has yet been isolated from the thymus, it should
probably be classified as belonging to the circulatory sys-
tem rather than the endocrine system. In animals, cer-
tain autoimmune diseases such as haemolytic anaemia
and systemic lupus erythematosus are associated with a
defective thymus.

Udder
Cow
The right and left sides of the udder are separated anatomi-
cally by a tendinous septum. Although a strong septum
does not exist between the fore- and hindquarters of the
same side, all four quarters are anatomically distinct, and
injection of differently coloured fluids into the four teats
shows that they each drain separate and distinct areas.
The smooth udder of the heifer, which is composed
almost entirely of fat, must be distinguished from the
pendulous fleshy udder of the cow in which glandular
tissue predominates and which is grey to yellowish white
in colour.

Ewe and goat
The udder is composed of two halves, each with one
small teat. In the goat, the udder is similar but the halves
are more pendulous and the teats are more strongly
developed and directed forwards.

Adrenal (suprarenal) bodies
In the ox , the adrenal glands are related to the two kid-
neys and lie anterior to them. The left adrenal body is in
contact with the dorsal sac of the rumen, though it does
not rotate with the left kidney when the rumen is dis-
tended. After dressing of the carcase, portions of the
right adrenal body may sometimes be found attached to

Sow
There are 10-16 mammary glands, arranged in two par-
allel rows; each possesses a flat triangular teat, and the
glandular substance appears whitish red on section.