Page 32 - Anatomy and Physiology of Farm Animals, 8th Edition

Introduction to Anatomy and Physiology / 17

The serous membranes of each cavity are discussed in some detail along with the
relevant systems later in this book.
form a sac wherein the serosa on the body
VetBooks.ir wall is continuous with that on the organs body cavity (the coelom) into a thoracic
The diaphragm divides the embryonic
within. As a consequence, no viscera are
found inside any of the serous sacs. A sim- cavity and the abdominopelvic cavity. Each
ple analogy is that of pushing one’s fist into of these are further subdivided.
a partially inflated balloon. The fist is never The thoracic cavity contains the pericar-
actually inside the balloon’s interior space, dial sac, derived from the pericardium sur-
but still it is surrounded by a portion of the rounding the heart, and two pleural sacs,
balloon (Fig. 1‐13). spaces which surround the two lungs. These
The part of the serosa on the surface sacs are formed by a serous membrane, the
of an organ is called the visceral serous pleura, a layer of simple squamous epithe-
membrane (visceral pericardium, visceral lium with underlying connective tissue,
pleura, and visceral peritoneum). The moistened with the small amount of fluid
serous membrane lining the cavity is called within the cavity of the sac (the pericardial
the parietal serous membrane (parietal space and the pleural space) (Fig. 1-14).
pericardium, parietal pleura, and parietal The abdominopelvic cavity is somewhat
peritoneum). The continuity of each serous arbitrarily divided into the abdominal and
sac is maintained by connecting layers of pelvic cavities. The abdominal cavity
serous membrane that extend from the contains the kidneys, most of the digestive
visceral layer of each serous membrane to organs, and a variable amount of the inter-
the parietal layer of the same serous mem- nal reproductive organs in both sexes. The
brane. The names of these connecting pelvic cavity contains the terminal part of
layers of serous membranes are based on the digestive system (the rectum) and all of
the specific areas they connect, and they the internal portions of the urogenital

(A)

(B)

(C)

Figure 1-13. (A, B) A fist pushed into a balloon never enters the interior of the balloon; it is surrounded
by a double wall of the balloon’s wall. (C) The heart in its pericardial sac. In this case, the wall of the
balloon is analogous to the pericardium, a serous membrane. This creates outer (parietal) and inner
(visceral) layers of pericardium.