Biomedical Engineering Reference
In-Depth Information
the bladder. Paired seminal vesicles communicate with the
ductus deferens near where they enter the prostate gland.
The prostate gland in nonhuman primates is more
conspicuous than in some other mammals, but it does not
form a complete ring around the urethra as it lacks the
anterior lobe found in humans. The final pair of glands,
the bulbourethral glands, discharge their product into the
urethra via slender ducts just caudal (inferior) to the
urogenital diaphragm (m. sphincter urethrae). (See perineal
morphology in the sections “Overview of perineum” and
“Female perineum” below for further details of external
genitalia.)
(anteriorly). The tail lies dorsally in the upper left quadrant
of the abdomen and is accessible from a lateral approach.
Pancreatic biopsies can be obtained through a vertical left
paramedian, paracostal incision through which the tail of
the pancreas can then be dissected out from its position near
the spleen.
Ovarian follicle aspiration is accomplished via lapa-
roscopy. The trocar, sleeve and laparoscope are positioned
in the body cavity through a transumbilical puncture site.
Two additional small incisions (0.5 cm) are located in the
lower left quadrant of the abdomen and along the midline
approximately 10 cm caudal to the umbilicus respectively.
Uterine biopsy can be performed by either laparotomy or
laparoscopy, and endometrial biopsies can also be per-
formed transvaginally.
Gastric intubation of nonhuman primates is similar to
other quadrupeds and is usually performed nasogastrically
to prevent biting on the tube. Elevation of the chin
straightens the pharynx and results in a fairly straight line
between the pharynx, esophagus, and stomach. Cranially,
the esophageal wall is thick then thins markedly around the
middle of the organ where the lumen has its widest diam-
eter. The distal (lower) part of the esophagus is surrounded
by a thick layer of circular muscle which acts as a valve and
may offer resistance to dilation. The stomach itself is
relatively large and offers no resistance to intubation.
Palpation for pregnancy, even early pregnancy, is
possible because the uterus is a single midline structure
lying cranial (superior) to the bladder. Through the
abdominal wall even the nongravid uterus is palpable
between the thumb and four fingers immediately cranial
(superior) and dorsal (posterior) to the pubic symphysis.
Alternatively, rectal digital palpation can be used. Deter-
mination of the age of the pregnancy is based on uterine
texture and fetal size, which varies considerably among
species.
Gut motility is another clinically significant aspect of
nonhuman primate morphology. The speed of transit of
food items through the digestive system varies greatly
among the species, but this variation has not yet been
clearly linked to phylogeny, diet, body size, and/or gut
morphology.
Neurovascular Systems
The autonomic nervous system in the abdomen and pelvis
includes sympathetic nerve fibers which typically exit the
spinal cord with spinal nerves T6 through L3 (
Kuntz, 1933
)
and form splanchnic nerves which synapse in pre-aortic
(for the gastrointestinal tract) or para-aortic (for the urinary
system) ganglia. The parasympathetic nerves to the gut
proximal to and including the first two parts of the large
intestine are from the vagus nerves (cranial nerve X). The
parasympathetic nerves to the more distal gut and to pelvic
viscera generally arise with spinal nerves L7 through S2.
As in humans and other mammals it is not uncommon to
find the levels of nerves exiting for the autonomic nervous
system to vary by one level in either direction.
The vascular system in the abdomen and pelvis follows
the general pattern seen in all mammals (
Lineback, 1933b
).
The exact location of the vessels and relative positions of
the portal and caval venous systems are similar, but not
identical, to those of humans as well as most mammalian
quadrupeds. For example, the left renal vein is found more
caudal (inferior) in the abdomen than is the right; the
splenic artery is the smallest branch of the celiac trunk and
the left gastric the largest
in some species,
including
Maccaca mulatta (
Lineback, 1933a
).
Clinically Significant Features of
Abdominal and Pelvic Morphology
Clinically significant features of abdominal and pelvic
morphology include the location of the pancreas and uterus
for biopsy and the ovary for egg aspiration as well as the
structures encountered in gastric intubation and palpation
of pregnancy.
The most common site for pancreatic biopsies is from
the tail of the organ. Although nearly the entire organ lies
retroperitoneal immediately posterior to the stomach, the
tail is intraperitoneal where its tip approaches the hilum of
the spleen. Its long axis lies transversely and the head is
surrounded by the duodenum. The pancreas is triangular in
cross section with the broadest base facing ventrally
PERINEAL MORPHOLOGY
Overview of Perineum
The perineum of nonhuman primates differs from humans in
both shape and function and shows considerable variation
among species. Some species have marked seasonal varia-
tion in coloration, prominence of sexual organs, and/or
swelling of the skin of the perineum (
Wislocki, 1933
). (See
also the section “Skin” above.) The perineum is bounded by
the base of the tail dorsally and the pubic symphysis
