Physiology of the Reproductive Tract

Published on 10/03/2015 by admin

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Last modified 10/03/2015

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Chapter 3 Physiology of the Reproductive Tract

Ovulation 46

Female Reproductive Physiology 46
Hypothalamus 49
GnRH 50
FSH 50
LH 50
Ovulation 50
Cyclical Ovarian Hormonal Changes 51

Oestrogens 51
Progesterone 51
Endometrial Cycle 51
Action of Ovarian Hormones 52

Oestrogen 52
Progesterone 52
Target Tissues 52
Effects of Ovarian Hormones 53

Genital Tract 53
Breast 53
Hypothalamus 53
Cardiovascular System 53
Skeleton 53
Psychological Characteristics 53
Puberty 54
The Menopause 55

Ovulation

Female reproductive physiology

During reproductive life, the cyclical development of ovarian follicles is the dominant process. The associated hormonal production has significant effects on the female genital tract, hypothalamus and pituitary.

In men, gamete production continues throughout life, whereas women develop their life supply of gametes during intrauterine life. See Chapter 1. The numbers decline even before birth, and there will be around 300,000 remaining at puberty.

The surface of the ovary is covered by a cuboidal ‘germinal’ epithelium. This layer is contiguous with the peritoneum. Underneath the epithelial layer is a thin layer of fibrous tissue, beneath which is the true cortex.

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The cortex consists of a specialised stroma or parenchyma; the primordial follicles are embedded in this layer.

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The primordial follicle consists of a primary oocyte surrounded by a single layer of flattened cells, the pre-granulosa, said to be derived from the cells of the sex cords.

The pre-granulosa cells become cuboidal and proliferate to form a shell several layers thick. At this stage, a hyaline membrane is formed immediately around the ovum – the zona pellucida.

The granulosa cells continue to proliferate until the follicle is approximately 200 μm in diameter. Fluid spaces now appear between the granulosa cells. They coalesce to form a cavity, the antrum, pushing the ovum to one side. The granulosa cells immediately surrounding the ovum are now known as the corona radiata, and the whole mass of cells in this situation is termed the cumulus oophorus.

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At the same time, the surrounding parenchymal cells arrange themselves concentrically around the follicle. The cells opposite the ovum become smaller and more epithelial in appearance. As the follicle increases in size, this epithelial change spreads to the parenchymal cells around the circumference of the follicle. This band of cells constitutes the theca interna. The cells are surrounded by sinusoidal capillaries, thus forming an endocrine gland-like structure. External to this band, the parenchymal cells are also arranged concentrically but retain their fusiform shape.

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