The main difference between ovarian and uterine cycle is that the ovarian cycle describes the changes that occur in the follicle, whereas the uterine cycle describes the changes that occur in the endometrium lining.
Ovarian and uterine cycles are two cycles that occur in the reproductive system of females. Periodic changes occur in the ovaries and uterus nearly every month.
Key Areas Covered
1. What is Ovarian Cycle
– Definition, Facts, Phases
2. What is Uterine Cycle
– Definition, Facts, Phases
3. Similarities Between Ovarian and Uterine Cycle
– Outline of Common Features
4. Difference Between Ovarian and Uterine Cycle
– Comparison of Key Differences
Key Terms
Follicular Phase, Luteal Phase, Menstruation, Ovulation, Ovarian Cycle, Proliferative Phase, Regenerative Phase, Secretory Phase, Uterine Cycle
What is the Ovarian Cycle
The ovarian cycle is the periodic changes that occur in the cortex of the ovary. The three ovarian cycle phases include the follicular phase, ovulation, and luteal phase.
Follicular Phase
The follicular phase is responsible for the first half of the ovarian cycle. The ovarian follicle undergoes maturation and the secretion of estrogen during the follicular phase. Many primary ovarian follicles grow under the influence of FSH secreted by the anterior pituitary gland. Only one of the primary ovarian follicles undergoes maturation into a Graafian follicle that secretes estrogens responsible for the proliferative phase of the uterus’s endometrium lining.
Figure 1: The Ovarian Cycle
Ovulation
The Graafian follicle ruptures in ovulation, releasing the mature ovum once every lunar month (28 days) during the fertile period. Also, ovulation occurs 14 days before menstruation. It inhibits FSH and stimulates LH secretion by the pituitary gland’s anterior lobe. This results in the rupture of the Graafian follicle.
Luteal Phase
The corpus luteum’s formation and progesterone secretion by the corpus luteum occurs in the luteal phase of the ovarian cycle. It also follows ovulation.
What is Uterine Cycle
The uterine cycle is the periodic changes that occur in the uterus’s endometrium lining, depending on the hormonal changes. Menstruation, regenerative, proliferative, and secretory phases are the four phases of the uterine cycle.
Menstruation
The corpus luteum degenerates at the end of the ovarian luteal phase, decreasing the progesterone and estrogen levels and resulting in a temporary spasm of the spiral arteries that supply the upper 2/3 of the endometrium. Followed by ischemia and necrosis, capillaries of the endometrium wall release blood along with the necrosed endometrium. It occurs for 3-5 days. The menstrual flow includes epithelial cells and blood. The thickness of the endometrium is 0.5 mm at this stage.
Figure 2: The Uterine Cycle
Regenerative Phase
The endometrium regeneration occurs on the fourth to sixth day of menstruation. The epithelium of the fundi of the glands is responsible for the regeneration of the epithelial lining of the endometrium. The thickness of the endometrium is 2 mm at this point, and it is flat, containing endometrial glands that are narrow and straight. At this phase, lymphocytes occur in the endometrial stroma.
Proliferative Phase
The endometrium proliferates under the influence of estrogen secreted by the Graafian follicle on the seventh to the fifteenth day of the uterine cycle. The thickness of the endometrium becomes 4 mm, and the epithelial lining is cuboidal. Also, the uterus contains straight, long, and widely separated glands at this phase.
Secretory Phase
The secretory phase corresponds to the luteal phase of the ovarian cycle and occurs on the 16th to the 28th day of the uterine cycle. Also, it is under the control of the hormone progesterone. The thickness of the endometrium is 10 mm at this phase. The endometrium is soft, velvet, and loaded with water. It also contains columnar epithelium that is differentiated into three layers at the end of this phase: stratum compactum, stratum spongiosum, and stratum basale.
Similarities Between Ovarian and Uterine Cycle
- The ovarian and uterine cycles are two cycles that occur in the reproductive system of females.
- They are periodic changes that occur nearly every month.
Difference Between Ovarian and Uterine Cycle
Definition
The ovarian cycle refers to the series of changes in the ovary during which the follicle matures, the ovum is shed, and the corpus luteum develops. In contrast, the uterine cycle refers to the phases characterized by changes in the endometrial lining of the uterus.
Occurrence
The ovarian cycle occurs in the ovary follicle, while the uterine cycle occurs in the uterus’s endometrium lining.
Phases
The three phases of the ovarian cycle include the follicular (preovulatory) phase, ovulation, and luteal (postovulatory) phase, while the four phases of the uterine cycle include menstruation, regenerative, proliferative (postmenstrual) phase, and secretory (premenstrual) phase.
Importance
The formation, maturation, and release of the ovum occur in the ovarian cycle, while menstruation and formation of the endometrial lining occur in the uterine cycle.
Conclusion
In brief, the ovarian and uterine cycles are two cycles that occur in the female reproductive system. The ovarian cycle occurs in the follicle of the ovary. Also, the follicular phase, ovulation, and luteal phase are the three phases of the ovarian cycle. In comparison, the uterine cycle occurs in the lining of the endometrium of the uterus. Menstruation, regenerative, proliferative, and secretory phases are the three phases of the uterine cycle. Therefore, the main difference between ovarian and uterine cycles is the type of changes in each cycle.
References:
- MedCrave Publishing. (2016, July 21). Reproductive cycles in females. MOJ Women?s Health.
Image Courtesy:
- “Anatomy and physiology of animals Ovarian cycle showing from top left clockwise” By Sunshineconnelly at English Wikibooks – Own work (CC-BY 3.0) via Commons Wikimedia
- “Figure 43 04 04” By Vaccinationist – Own Work (CC-BY 4.0) via Commons Wikimedia
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