3-13. BURSA
a. A bursa (figure 3-3) is the simplest of serous cavities. Each bursa is a small
sac located between two moving structures, usually a muscle moving over a bony
surface. The bursa reduces the friction between the two structures. For example, a
bursa prevents excessive friction between the skin and patella (knee cap). This bursa,
called the prepatellar bursa, allows the skin to move freely over the patella. (When
injured, it produces excessive amounts of the serous fluid and is known as
"housemaid's knee.")
Figure 3-3. A bursa--the simplest serous cavity.
b. As a fibrous sac, each bursa has a central cavity which is lined with a serous
membrane. This membrane is a simple squamous epithelium. The serous membrane
secretes a serous fluid into the serous cavity. The serous fluid is the lubricant,
minimizing friction.
3-14. OTHER SEROUS CAVITIES OF THE BODY
a. Other important serous cavities are associated with the major hollow organs,
referred to as visceral organs. Each lung is encased in a serous cavity called the
pleural cavity. The heart lies in a serous cavity called the pericardial cavity. The
intestines are allowed to move freely during the digestive processes within the
peritoneal cavity.
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