FEMALE REPRODUCTIVE SYSTEM

Female gonads are the ovaries where the female sex cells or ova are formed. 

    Female reproductive tract includes :

    1)An organ (uterus) to hold and nourish a developing infant.

    2)Various passageways

    3) External genital organs

   

OVARIES

   

     Small, somewhat flattened oval body.             Ovaries descend but only as far as the pelvic portion of the abdomen. 

    Held in place by ligaments that attach them to the uterus and body wall.

   

OVA AND OVULATION

   Ovaries of a newborn female contain a large number of potential ova.

   Each month during the reproductive years, several ripen but only one is released.

   

   Maturation of the ovum takes place in a small fluid-filled cluster of cells called the ovarian follicle. (graffian follicle)

  As the follicle develops, cells in its wall secrete estrogen which stimulates growth of the uterine lining.

  

   When an ovum has ripened, the ovarian follicle may rupture and discharge the egg cell from the ovary surface.

   The rupture of follicle allowing the escape of an ovum is called ovulation. 

  

   Any ova that are not released degenerate.

   Released egg cell makes its way to the nearest oviduct i.e. a tube that arches over the ovary and leads to the uterus.

   

CORPUS LUTEUM

    After the ovum is expelled, the remaining follicle is transformed into a solid mass called the corpus luteum.

   Corpus luteum secretes estrogen and progesterone.

   Which eventually shrinks and is replaced by scar tissue.

   When a pregnancy occurs, however, the structure remains active for three months.

   Sometimes during a normal ovulation, the corpus luteum persists and forms a small ovarian cyst, (fluid filled sac) which resolves without treatment

   

ACCESSORY ORGANS

They include :

    oviducts

    uterus

    vagina

    greater vestibular glands 

    vulva

    perineum

  

OVIDUCTS

   Tubes that transport the ova in the female reproductive system.

   Also known as the uterine tubes or fallopian tubes. Their is no direct connection between ovary and this tube.

   Ovum is swept into oviduct by a current in the peritoneal fluid

  

   Peritoneal fluid produced by fimbriae. (small, fringelike extensions located at the edge of the tube’s opening into the abdomen). 

   Ova cannot move on own.

   Movement depends on sweeping action of cilia in the oviduct’s lining and on peristalsis of the tube.

   Takes 5 days for an ovum to reach the uterus form the ovary

  

UTERUS

   Organ in which a fetus can develop to maturity.

  Oviducts lead to the uterus.

  Superior portion rests on upper surface of the urinary bladder and inferior portion embedded in the pelvic floor between the bladder and the rectum.

   

 WALLS OF UTERUS

The walls of the uterus include:

    1) Muscular layer (myometrium)    

    2) Inner layer called endometrium

      

The inner layer changes during menstrual cycle

   

VAGINA

    Distal part of the birth canal which opens to the outside of the body.

    Cervix (opening of the uterus) leads to the vagina.

   Muscular tube connecting the uterine cavity with outside.Lining of the vagina is a wrinkled mucous membrane similar to that found in the stomach.

  

    Rugae (folds) permit enlargement so that childbirth usually does not tear the lining.

   Vagina is an organ for child birth and also receives the penis during sexual intercourse.          A fold of membrane, called the hymen, may sometimes be found near the vaginal canal opening.

  

GREATER VESTIBULAR GLANDS

   Just superior and lateral to the vaginal opening are the two mucus-producing greater vestibular glands.

   These glands secrete into an area near the vaginal opening known as the vestibule.

  These glands provide lubrication during intercourse.

   

PUBERTY IN FEMALES

   The onset of puberty is caused by an alteration in brain function that increases the secretion of GnRH.

   This hormone in turn stimulates the secretion of pituitary gland gonadotropins,which stimulate follicle development and estrogen secretion.

   

   The adipose-tissue hormone leptin is known to stimulate the secretion of GnRH and may play a role in puberty. This may explain why the onset of puberty tends to correlate with the attainment of a certain level of energy stores(fat) in the girl’sbody.

AMENORRHEA 

   

    The failure to have a normal menstrual cycle is called amenorrhea. Primary amenorrhea is the failure to initial normal menstrual cycles at puberty(menarche), whereas secondary amenorrhea is defined as the loss of previously normal menstrual cycles(common causes pregnancy and menopause).

   

     Excessive exercise and anorexia nervosa can cause both primary and secondary amenorrhea.

  

PRECOCIOUS PUBERTY

    The age of normal onset of puberty is controversial. However, puberty onset before the age of 6-7 in girls and 8- 9in boys warrants clinical investigation.

    Precocious puberty is defined as the premature appearance of secondary sex characteristics and is usually caused by an early increase in gonadal steroid production.

    This leads to an early onset of the puberty growth spurt, maturation of the skeleton, breast development(in girls) and enlargement of genitalia in boys. 

    True precocious is caused by the premature activation of GnRH and LH and FSH secretion.         Which is often caused by tumors or infections in the area of the central nervous system that control GnRH release. 

    Treatments that decrease LH and FSH release are important to allow normal development.

  

CONTROL OF OVARIAN FUNCTIONS

THE OVARIES HAVE SEVERAL FUNCTIONS

▪ Oogenesis-the production of gametes during the fetal period.

▪ Maturation of the oocyte.

▪ Expulsion of the mature oocyte(ovulation)

▪ Secretion of the female sex steroid hormones (estrogen and progesterone). It also secretes the peptide hormone inhibin.

 

The major factors controlling the ovaries are:

1.GnRH – Gonadotropin-releasing hormone 2.FSH-Follicle stimulating hormone

3.LH- leutinizng hormone

4.Estrogen 

5.Progesterone

  

GONADOTROPIN-RELEASING HORMONE IS SECRETED FROM THE HYPOTHALMUS AND IT STIMULATES THE ANTERIOR PITUITARY GLAND TO SECRETE LH AND FSH.

    LH is released form the pituitary gland. Its main function is to cause ovulation and it causes the formation of the corpus luteum.

    FSH is primarily responsible for stimulating the growth of the ovarian follicle.

   Estrogen is secreted from the ovary and it is involved in the thickening of endometrium of the uterus and the growth of the uterus

   Progesterone causes the endometrium to secrete special proteins during the second half of the menstrual cycle, preparing it to receive and nourish an implanted fertilized egg.

  

   During early in uterine development, the primitive germ cells, or oogonia, undergo numerous mitotic divisions. Around the seventh month after conception, the fetal oogonia cease dividing. 

   

   During fetal life, all the oogonia develop into primary oocytes, which then begin a first meiotic division by replicating their DNA. 

   They do not complete division in the fetus. The cells are said to be in a state of meiotic arrest. This state continues until puberty and the onset of renewed activity in the ovaries.

 

   Only those primary oocytes destined for ovulation will complete the first meiotic division,it occurs just before the egg is ovulated.

    Each daughter cell receives 23 chromosomes, each with two chromatid. In this division, one of the two daughter cells, the secondary oocyte, retains virtually all the cytoplasm.

    The other called the first polar body is small and non-functional. Thus, the primary oocyte, which is already as large as the egg will pass on to the secondary oocyte just half of its chromosomes but almost all of its nutrient-rich cytoplasm.

      The second meiotic division occurs in the fallopian tube after ovulation, but only if the secondary oocyte is fertilized. 

     As a result of this second meiotic division, the daughter cells receive 23 chromosomes, each with a single chromatid.

  

   Once again, the daughter cell, now called an ovum, retains nearly all the cytoplasm. The other daughter cell, the second polar body is very small and non-functional.

   The net result of oogenesis is that each primary oocyte can produce only one ovum.

      

    GnRH is secreted from the hypothalmus. This causes the secretion of LH and FSH from the anterior pituitary gland. 

    LH and FSH levels increase (slightly elevated levels of estrogen and inhibin exhibit little negative feedback)

   

     Multiple follicles begin to enlarge and secrete estrogen. Estrogen concentration increase markedly.

    FSH secretion and FSH plasma concentration decrease.

     The increasing plasma estrogen concentration exerts a “positive” feedback on gonadotropin secretion.

 

   An LH and FSH surge is triggered and ovulation occurs.

   The corpus luteum forms and begins to secrete large amounts of both estrogen and progesterone.

   

    Plasma concentrations of estrogen and progesterone increase.

 FSH and LH secretion are inhibited and their plasma concentrations decrease.

 The corpus luteum begins to degenerate and decrease its hormone secretion.

 Plasma estrogen and progesterone concentrations decrease.

 FSH and LH concentrations begin to increase and a new cycle begins.

  

EFFECTS OF ESTROGEN

▪ Stimulates the growth of the ovary and follicles.

▪ Stimulates external genitalia.

▪ Stimulates breast growth, particularly ducts and fat deposition in puberty.

▪ Stimulates female body configuration development during puberty: narrow shoulders, broad hips, female fat distribution. (deposition on hips and breasts)

▪ Stimulates prolactin secretion but inhibits prolactin’s milk-inducing action on the breasts.

  

EFFECTS OF PROGESTERONE 

▪ It Converts the estrogen primed endometrium to an actively secreting tissue suitable for implantation of the embryo.

▪ Decreases contraction of the fallopian tubes and myometrium.

▪ Increases body temperature.

▪ Decreases proliferation of vaginal epithelial cells.

▪ Induces thick, sticky cervical mucus.

▪ Inhibits milk producing effects of prolactin.

▪ Stimulates breast growth, particularly glandular tissue.