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SYSTEM REPRODUKSI SIMPLE BANGET



Reproductive System

Overview of the Reproductive System                                                                  
  1. The reproductive system consists of primary and secondary sex organs.

  2. The secondary sex organs are those that are essential to reproduction,
  3. The primary sex organs (gonads) are those that produce gametes (sperms and eggs) Male:  testes Female:  ovaries Male:  ducts, glands, and a penis Female:  uterine tubes, uterus, vagina 
  4.  Secondary sex characteristics are features that are not essential for reproduction but that attract the sexes to each other.
  5. The sex of an individual is determined by 2 sex chromosomes: Male:  XY; Female: XX
Male Reproductive System

Testes                                                  
  1. Produce sperm cells which are developed from germ cells in seminiferous tubule
  2. Secret testosterone by interstitial (Leydig) cells
Scrotum                                                                                              
  1. Protect testes 
  2. Maintain the temperature of the testes degrees lower than body temperature (Osmoregulator) 
Epididymus 
  •  is the storage site of sperm cells. It reabsorbs about 90% of the fluid secreted by the testis. Sperm remain stored here for 40-60 days and become reabsorbed if not ejaculated prior to that time.

The Spermatozoan                                                                                         
               
The spermatozoan, or sperm cells, has a pear-shaped head and a long tail.
  1. The head contains the haploid nucleus, an acrosome bearing enzymes used to dissolve a path to penetrate the egg, and a flagellar basal body.
  2. The tail contains large mitochondria that produce ATP for sperm motility.

Semen                                                                                                                 
The fluid expelled during orgasm is called semen or seminal fluid. Its major constituents are as follows.
  1. Sperm cells from epididymus are present at a count of 50-120 million sperm/mL.
  2. Fructose, produced by the seminal vesicles, provides a source of energy for the sperm.
  3. Clotting and anticoagulant factors are produced by seminal vesicles and prostate. After ejaculation, semen clots like blood, causing it to stick inside the female vagina. About 15-30 minutes later, fibrolysin in the prostatic fluid dissolves the clot and sperm can begin their migration up the reproductive tract of the female.
  4. Prostaglandins, produced by the prostate and seminal vesicles, stimulate peristaltic contractions of the female reproductive tract that may help draw semen into the uterus.
  5. Spermine is a base that reduces acidity of the female vagina, increasing the survival rate of sperm.
Sexual Intercourse                                                                                                                                         
The male sexual response include two phases:
  1. Erection of the penis, allowing it to penetrate the female vagina, and
  2. Ejaculation, expelling semen into the vagina.
Ejaculation
  1. Ejaculation is the propulsion of semen from the male duct system.
  2. Initiated by massive discharge of sympathetic nerve impulses
  3. The ducts and accessory glands contract, emptying their contents into the urethra
  4. The bladder sphincter constricts, preventing shunt of semen into the bladder.
  5. The bulbospongiosus muscles of the penis contract rapidly and rhythmically, propelling semen from the urethra.

Refractory Period
1.         A period following ejaculation and lasting anywhere from 10 minutes to a few hours
2.         impossible to attain another erection and orgasm
                                                               
The Female Reproductive System
The Ovaries
  1. Produce oocytes
  2. Produce sex hormones
 The ovarian follicles secrete estrogens, progesterone, inhibin, and a small amount of androgen.

The Uterine Tubes
  1. The uterine tube (oviduct or fallopian tube) is a canal 10 cm long leading from the ovary to the uterus. It has a trumpet-shaped infundibulum with projections called fimbriae.
  2. The wall of the uterine tube is well endowed with smooth muscle, and its mucosa has ciliated cells.
  3. The cilia beat toward the uterus and, with the help of muscular contractions of the tube, convey the egg in that direction. It takes about 3 days for an egg to travel the length of the uterine tube, but an unfertilized egg lives only 24 hours.
The Uterus
is a thick, muscular chamber that functions to:
  1. harbor the embryo
  2. provide a source of nutrition
  3. expel the fetus at the end of its development
Vagina
  1. a tube 8-10 cm long that allows for the discharge of menstrual fluid, receipt of the penis and semen, and birth of a baby. The vaginal wall is thin but very distensible.
  2. Adult vaginal epithelium is a stratified squamous epithelium. The epithelial cells are rich in glycogen. Bacteria ferment this to lactic acid, resulting in a low vaginal pH.
               
Accessory Glands and Erectile Tissues
  • On each side of the vagina is a pea-sized greater vestibular (Bartholin) gland with a short duct opening into the vestibule or lower vagina. These glands are homologous to the bulbourethral glands of the male. They keep the vagina moist and provide most of the lubrication for intercourse.

Climacteric and Menopause
  1. Women, like men, go through a midlife change in hormone secretion called the climacteric. In women, it is accompanied by menopause, the cessation of menstruation.
  2. With age, the ovaries have fewer remaining follicles and those that remain are less responsive to gonadotropins. Consequently, they secrete less estrogen and progesterone. Without these steroids, the uterus, vagina, and breasts atrophy.

Menopause is the cessation of menstrual cycles, usually occurring between the ages of 45 and 55. The average age has increased steadily in the last century and is now about 52.

Oogenesis and the Sexual Cycle
Oogenesis
  1. Egg production is called oogenesis, which is a distinctly cyclic event.
  2. Most primary oocytes undergo a process of degeneration called atresia. Only 2 million remain at the time of birth, and by puberty, only 400,000 remain.
  3. Beginning in adolescence, FSH stimulates the primary oocytes to complete meiosis I, which yields two haploid daughter cells of unequal size. One will become the egg with large amounts of cytoplasm. The other, a polar body, will serve only as a dumping ground for the extra set of chromosomes.

The secondary oocyte proceeds as far as metaphase II and then arrests until ovulation. If it is fertilized, it completes meiosis II and produces a second polar body. The large remaining egg unites its chromosomes with those of the sperm and produces a zygote.

The Sexual Cycle
  • a  28-day cycle of sequential changes caused by shifting patterns of hormone secretion.
  • starts at the first day of menstruation. 
  • Changes in the ovaries constitute the ovarian cycle which is subdivided into 3 phases: the follicular phase, ovulation, and luteal phase.   
  • The parallel changes in the uterus are called the menstrual or unterine cycle, which is subdivided into 3 phases: menstruation, proliferative phase, and secretory phase.

Ovarian Cycle
The Follicular Phase   (Day 1-14)
  1. The follicular phase extends from the beginning of menstruation until ovulation. It averages 14 days, but is also the most variable portion of the cycle.
  2. FSH causes follicular cells around the oocyte to develop into granulosa cells, and the follicle is now a primary follicle.
  3. Granulosa cells secrete an estrogen-rich follicular fluid, which pools to form the antrum. The follicle is now called the secondary follicle.
  4. One follicle rapidly outpaces the others and becomes the dominant follicle.

Ovulation  (Day 14)
  1. Ovulation is triggered by a sudden burstlike release of LH (Luteining Hormone) secretion from pituitary when estrogen rises beyond a critical concentration.  The LH surge is the consequence of an exceptional positive feedback of estrogen on hypothalamus-pituitary axis.
  2. Only the oocyte in the dominant follicle is released in each ovarian cycle.  Oocytes in other follicles degenerate.
Luteal Phase  (Day 15-28)
  1. When the follicle expels the oocyte, it collapses and bleeds into the antrum. Under the influence of LH, this structure now develops into a glandular corpus luteum that secretes progesterone and some estrogen.
  2. Corpus luteum also secretes inhibin at this point, which suppresses FSH and further ovulations.
  3. In the absence of pregnancy the corpus luteum begins to degenerate in about 10 days because rising progesterone output inhibits further release of FSH and LH. Without LH, the corpus luteum begins to shrink.
  4. If pregnancy occurs, the corpus luteum continues to secrete progesterone and estrogen for about 3 months under the stimulation of LH-like hormone released by the developing embryo.  The secretion by corpus luteum does not stop until the placenta is ready to take over its homone-producing duties.
Menstrual (Uterine) Cycle
Menstruation  (Day 1-5)
  1. The superficial layer stratum functionalis of the uterus detaches from the uterine wall, accompanied by bleeding for 3-5 days. 
  2. Sex hormones are at their lowest normal levels at Day 1
  3. Menstrual fluid contains fibrolysin, therefore it normally does not clot.
Proliferative Phase (Day 6-14)
  1. Estrogen stimulates mitosis, the prolific growth of blood vessels, and the formation of a new stratum functionalis.
  2. Estrogen also stimulates the endometrium to develop progesterone receptors.
  3. As ovulation approaches, the uterine tune becomes edematous, its fimbriae develop and caress the ovary, and its cilia create a gentle current in the nearby peritoneal fluid. The ovulated egg is usually caught up in this current and swept into the tube.   An oocyte has only 24 hours to be fertilized. The chance of fertilization is enhanced by changes in the cervical mucus at the time of ovulation. It becomes thinner and more stringy.

Secretory Phase  (Day 15-28)
In response to rising level of progesterone, the endometrium of the uterus proliferates further in preparation for possible pregnancy.
  1. Spiral arteries elaborate and coil more tightly
  2. Uterine glands enlarge, coil, and begin secreting nutritients into the uterine cavity to sustain the embryo until implantation.
  3. The cervical mucus becomes viscous, forming the cervical plug, which prevents sperm entry. 
If pregnancy does not occur towards the end of the secretory phase, LH level drops due to negative feedback of high level of progesterone.  Progesterone level decline following the drop of LH.  Without the support of progesterone, the endometrium undergoes degeneration in the following sequence.
  1. The spiral arteries close due to continuous and intensive constriction (spasm).
  2. The superficial layer stratum functionalis of the uterus is deprived of blood supply.
  3. The endometrial cells die of ischemia.
  4. The spiral arteries suddenly relax and open wide.
  5. Blood gushes into the weakened capillary beds, causing the capillaries to fragment and the stratum functionalis to slough off.