Hormonal Control of Ovarian and Uterine Cycles

A. Essential organs

1. The right and left ovary

B. Female sex cells

2. Ova

• Produced in the ovaries

C. Accessory Organs

• Consist of ducts or modified structures that extend from the ovaries to the exterior

- 2 Uterine tubes, uterus, vagina

• Mammary glands

-Accessory sex glands: Bartholin's gland (2), breast (2)

-function reproductively only in women

• External reproductive organs or genitals

-vulva

II Ovaries

A. Ovarian follicles

• Embedded in connective tissue matrix just below the outer layer of ovary

- Each contains an oocyte (immature stage of a female sex cell)

B. Primary Follicles

• Are primary follicle when puberty is reached

• Each has a layer of granulosa cells around the oocyte

• During reproductive life in woman 350-500 grow into mature follicles

- What ovulates and releases an ovum for fertilization.

- Mature ovum is called Graafian follicle

• Thickness around the oocyte increases and a hollow chamber (antrum) will appear to from a SECONDARY follicle

• Development continuous after ovulation

- The ruptured follicle transforms into a hormone secreting glandular structure called corpus luteum

- A Latin word meaning yellow body, yellow appearance

III Ovary functions

A. Oogenesis

• Production of female gametes (sex cells)

• Type of cell division responsible for sperm formation, meiosis and development of ova

• During this process two meiotic divisions occur

- Chromosomes are reduced into equally daughter cells 23 compared to 46 in other body cells

- 1 large ovum and small daughter cell (polar bodies) degenerate.

- Ovum with larges cytoplasm supply provides nutrients for development of an embryo until implantation into the uterus.

- Fertilization: sex cells from both parents fuse and normal chromosome numbers are achieved (46)

B. Production of estrogen and progesterone

• The granulosa cells around the oocyte in the mature follicle secrete estrogen.

• Estrogen is the sex hormone that causes the development and maintenance of the female and stimulates the froth of the epithelial cells lining the uterus.

- Actions of estrogen allow the body to do the following:

1. Develop and mature reproductive organs ( external genitals)

2. Pubic hair and breast development

3. Female body contours by deposition of fat below the skin surface in the breast and hip region begin to develop

4. Initiation of first menstrual cycle

• Progesterone is produced by the corpus luteum

- Is a glandular structure that develops from a follicle that just released from an ovum

- Progesterone stimulates proliferation and vascularization of the epithelial lining of the uterus that acts with estrogen to initiate the menstrual cycle within girls entering puberty.

- If stimulated by the appropriate anterior pituitary hormone it will produce progesterone for 11 days after ovulation.

IV Reproductive ducts

A. uterine tubes or fallopian tubes (oviducts)

• ducts for the ovaries although not attached

• out end of each tube terminates in an expanded, funnel-shaped structure that has fringe like projections along its edge (Fimbriae)

• Post ovulation discharged ovum first enters the abdominal cavity and then enters the uterine tube assisted by wavelike movement of the fimbriae and the beating of the cilia on their surface.

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B. Uterus

• An extremely strong, small organ the size of a pear

• Mostly muscle (myometrium) with small cavity inside

• Composed of two parts

- The upper portion (the body)

- The lower portion (the cervix)

• Fundus

- The fundus is above the level where the uterine tubes attached to the body of the uterus is a rounded out form of bulging prominence.

• Three functions of Uterus

1. Menstration

2. Pregnancy

3. Labor

- When progesterone and estrogen are at their lowest consentration in the blood is when mentration starts.

- Small pieces of the mucous membrane lining of the uterus (endometrium) become loose and leave torn blood vessels underneath, this in turn allows blood to trickle out of the uterus and into the vagina to then leave the body.

- Unless one becomes pregnant this process will occur about every month, thus becoming a menstrual cycle.

C. Menstrual Phases

• Menses (menstrual flow)

- Referred to as menarche

- 4-5 days of bleeding

• Proliferative phase

- Follicles mature, uterine lining thickens, and estrogen secretion takes place

- Begins after the menstrual flow ends and lasts until ovulation

• Secretory phase

- Uterine lining reaches its greatest thickness and the ovary secretes its highest levels of progesterone.

Sources:
The human body in health and disease third addition