Final answer:
Umbilical hernias are small hernias that occur due to an incomplete closure of the umbilical region after birth, forming a bulge near the navel, especially during crying or straining, and are more common in females.
Step-by-step explanation:
The umbilical hernias that the student is asking about are typically small hernias due to a defect in the abdominal wall resulting from an incomplete closure of the umbilical region. As mentioned in Figure 23.5.4, the umbilical cord is cut shortly after birth, which leaves a stub that eventually withers away and forms the navel, usually within a month. However, in some cases, the area does not close fully, leading to an umbilical hernia. These hernias are indeed more common in females and can be characterized by a bulge near the navel, especially when the infant cries or strains.