in preparation for lactation. After childbirth, hormones
secreted by the anterior lobe of the pituitary gland
stimulate production for 6 to 9 months.
FEMALE REPRODUCTIVE CYCLE
Females around age 11 begin to experience the
female reproductive cycle and continue into middle
age, after which it ceases. The female reproductive
cycle, or menstrual cycle, is characterized by regular,
recurring changes in the uterine lining, resulting in
menstrual bleeding (menses). The first phase of the
recurring reproductive cycle is menstrual bleeding.
Menstrual bleeding begins when the endometrial
lining starts to slough off from the walls of the uterus,
and it is characterized by bleeding from the vagina.
This is day 1 of the cycle, and this phase usually lasts
through day 5. The time between the last day of the
menses and ovulation is known as the postmenstrual
phase. It lasts from day 6 through day 13 or 14 and is
characterized by proliferation of endometrial cells in
the uterus, which develop under the influence of the
hormone estrogen. Ovulation, as discussed earlier in
this section, is the rupture of a primordial follicle with
the release of a mature ovum into the fallopian tubes. It
usually occurs on day 14 or 15 of the cycle. The
postovulatory (premenstrual) phase is the time
between ovulation and the onset of the menstrual
bleeding and normally lasts 14 days. During this phase
the ovum travels through the fallopian tubes to the
uterus. If the ovum becomes fertilized during this
passage, it will become implanted in and nurtured by
the newly developed endometrial lining. However, if
fertilization does not take place, the lining deteriorates
and eventually sloughs off, marking day 1 of the next
cycle.
SUMMARY
In this chapter, you have learned about the basic
structures of the cell to the many complex systems of
the human body. In addition, you have acquired the
understanding of how each body system functions and
how each system is interdependent upon each other.
You will use this knowledge of human anatomy and
physiology throughout your career in the medical
services. For example, the anatomical terminology
will be used in describing location of injuries or
conditions. Also, when you perform patient
assessments, a clear and thorough understanding of
anatomy and physiology is essential. Patient
assessment and documentation procedures will be
discussed in the next chapter, entitled Fundamentals
of Patient Care.
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