Page 409 - The Veterinary Laboratory and Field Manual 3rd Edition

378 Susan C. Cork

Figure 8.12 Anatomy of the lower limb of the horse
(typical of an ‘odd toed’ ungulate). The following
key applies to all three illustrations. (A) lateral view
of lower limb bones, (B) frontal view of lower limb
bones and (C) cross section of lower limb bones in
situ. (a) distal digit or coffin bone, (b) distal sesamoid
bone (small bone which lies at flexor surface of the
joint), (c) middle digit, (d) proximal digit, (e) proximal
sesamoid bones, (f) lower end of metacarpal main
bone (front limb, equivalent to digit three), (g) distal
or lower end of small metacarpal bone (one on each
side, remnant of digits 2 or 4, also known as ‘splint’
bones), (h) digital cushion (cushion of the underside
of the foot), (i) ‘frog’, (j) sole of the foot, (k) hoof
wall, (l) laminae (sensitive area equivalent to bed
of the fingernail – laminitis is the inflammation of
this area), (m) coffin joint, (n) pastern joint, (p) fet-
lock joint, (q) common digital extensor tendon (this
keeps the foot straight), (r1) deep and (r2) superfi-
cial digital flexor tendons (allows the horse to lift the
foot, that is, flexes the fetlock joint). Tendons attach
muscle to bone and are well developed in the lower
limbs of hoofed animals.

Check the thyroid gland in the midline ven- ogy if a metabolic disease involving the bones
tral neck area, this will be enlarged in neonatal is suspected.
and mature animals in iodine deficient areas The pancreas produces the sugar regulating
(goitre) or in cases of hyperthyroidism (often hormones insulin and glucagon in the islets of
due to benign neoplastic changes). Diagnosis Langerhans. It also produces exocrine enzymes
will need to be made after histological exami- and becomes inflamed in pancreatitis. The organ
nation to assess the nature of the pathology is located among the upper parts of the small
present. The thyroid gland produces thyroid intestine near the liver and biliary entrance to
hormones which are important in the regulation the duodenum; it is usually pale brown colour
of growth and metabolic rate. The parathyroid and is elongated in shape. Histological sections
glands are usually found within the structure of may be examined to assess the integrity of the
the thyroid gland in birds and just outside it in secretory cells in the islets of Langerhans.
most mammals. The parathyroid gland produces Other endocrine tissues include the reproduc-
parathyroid hormone, which controls calcium tive glands (testes in the male and ovaries in the
and phosphorous balance along with calcitonin female) but if it is necessary to assess causes of
which is produced in the thyroid gland. There infertility or reproductive disease in the female
will rarely be evidence of gross changes in the animal at post-mortem, try to request special-
parathyroid glands but collect these for histol- ized training and/or some experience in rectal

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