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15 Reproductive System.ppt


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15 Reproductive System.ppt

  2. 2. INTRODUCTION <ul><li>Reproductive is essential for the continuation of the species. </li></ul><ul><li>If any species lost the ability to reproduce, it would become extinct very soon. </li></ul><ul><li>All mammals, including Man reproduce by sexual means. </li></ul><ul><li>This involves the fusion of two gametes or germ cells . </li></ul><ul><li>The male produces sperm , while the egg or ovum is produced by the female. </li></ul>
  4. 4. EGG SPERM
  5. 5. <ul><li>The two cells come together and fuse during the physical act of copulation . </li></ul><ul><li>At this time, though many sperms are produced, only one of them fuses with the ovum. </li></ul><ul><li>The ovum is then said to be fertilized . </li></ul><ul><li>The resulting cell is called zygote . </li></ul><ul><li>Under favorable conditions it is able to undergo cell division and differentiation, to produce a new, complex organism. </li></ul>
  7. 10. <ul><li>The male and female germ cells are produced in different organs. </li></ul><ul><li>These organs are able to produce the germ cells (sperm/ova) only after puberty . </li></ul><ul><li>Puberty usually occurs a little earlier in girls (around 12 years) compared to boys (around 14 years). </li></ul><ul><li>The onset of puberty depends on the release of ‘trigger’ hormones from the anterior pituitary and the hypothalamus. </li></ul><ul><li>It is believed that a particular brain area acts as a time marker’, and at puberty sends stimulator signals to the hypothaiamus. </li></ul>
  8. 11. <ul><li>Hence various functions of the reproductive system are closely controlled by the nervous and endocrine systems. </li></ul><ul><li>At the age of puberty in both sexes certain changes occur, which are indicators of sexual maturity. </li></ul><ul><li>These changes are depended on the secretion of specific hormones. </li></ul><ul><li>As described dealing with nervous system, the hypothalamus controls these secretions. </li></ul><ul><li>The hypothalamus is in turn, controlled by a higher centre in the cerebral cortex. </li></ul>
  9. 14. TESTOSTERONE ESTROGEN/PROGESTERONE <ul><li>In both sexes the most important change is the change in the function of the reproductive glands. </li></ul><ul><li>After puberty, in the male the testes produce sperms, while the female ovaries produce ova. </li></ul><ul><li>In addition to these changes, there are other secondary changes – In both sexes there are definite psychological changes. </li></ul><ul><li>In the male there is appearance of facial hair and deepening of the voice. </li></ul><ul><li>In the female the development of the mammary glands or breasts, takes place. </li></ul>
  10. 15. MALE REPRODUCTIVE SYSTEM <ul><li>The male reproductive system includes the testes , which are present in the scrotum, outside the abdomen. </li></ul><ul><li>Sperm cells are produced here and pass through a long tube – the vas deferens . </li></ul><ul><li>The tube leads from the testis upwards to join the urethra. </li></ul><ul><li>In the urethra, other fluids mix with the sperms, to form semen . </li></ul><ul><li>The fluid portion of the semen is made up of secretions of glands called seminal vesicles below the bladder. </li></ul>
  11. 17. <ul><li>Other secretions are contributed by the prostate gland . </li></ul><ul><li>The urethra extends along the centre of the penis , where it serves the dual function of carrying urine or semen. </li></ul>
  12. 18. TESTES <ul><li>Testes are the male sex glands, </li></ul><ul><li>located in the scrotum or scrotal sac, </li></ul><ul><li>outside the abdomen. </li></ul><ul><li>The hormones produced by these </li></ul><ul><li>glands are responsible for the changes which occur in a boy at puberty. </li></ul><ul><li>Sperms are produced by special cells in the testes. </li></ul><ul><li>These cells are very sensitive to temperature. </li></ul><ul><li>Hence in normal males the testes lie outside the abdomen, where the temperature is 3 degrees lower than inside the abdomen. </li></ul>
  13. 19. SEMINAL VESICLES <ul><li>The seminal vesicles are two small pouches at the back of the bladder. </li></ul><ul><li>The secretions of these glands are present in the semen, and provide nutrition to the sperms. </li></ul>
  14. 20. PROSTATE GLAND <ul><li>The prostate gland is an auxiliary gland which surrounds the urethra where the latter joins the urinary bladder. </li></ul><ul><li>Ducts from the prostate lead into the urethra. </li></ul><ul><li>The prostate gland secretes a thin, milky fluid. </li></ul><ul><li>This secretion, together with that of the seminal vesicles and the sperms, makes up the semen. </li></ul><ul><li>The prostatic fluid is alkaline. </li></ul><ul><li>This increases the motility and fertility of the sperms. </li></ul>
  15. 22. ENLARGED PROSTATE GLAND <ul><li>In many men, there is a gradual enlargement of the prostate with age. </li></ul><ul><li>The cause is idiopathic. </li></ul><ul><li>As the gland increases in size, it presses on the neck of the bladder, interfering with the discharge of urine. </li></ul><ul><li>This incomplete emptying causes a frequent need to urinate. </li></ul><ul><li>Severe enlargement usually requires surgery. </li></ul><ul><li>If the condition is neglected, the bladder cannot empty at all. </li></ul><ul><li>This is a medical emergency, requiring immediate attention. </li></ul>
  16. 23. URETHRA <ul><li>The urethra passes down the centre of the penis. </li></ul><ul><li>It is common duct for urine and semen. </li></ul><ul><li>The urethra is surrounded by spongy tissue, which has a very rich blood supply. </li></ul><ul><li>These blood vessels fill with blood, following sexual stimulation, a necessary step for erection of the penis. </li></ul><ul><li>This is brought about by parasympathetic nerve stimulation. </li></ul>
  17. 24. <ul><li>Sympathetic nerve stimulation is necessary for the semen to be extruded from the urethra to the exterior. </li></ul><ul><li>This process is called ejaculation. </li></ul><ul><li>Sympathetic nerves also cause relaxation of the internal sphincter of the urinary bladder, preventing semen from entering the bladder. </li></ul>
  18. 25. FEMALE REPRODUCTIVE SYSTEM <ul><li>The female reproductive organs lie entirely in the pelvis. </li></ul>
  19. 26. <ul><li>A fold of peritoneum stretches across the pelvis. </li></ul><ul><li>In front of the peritoneum lies the bladder, behind it lies the rectum. </li></ul><ul><li>This peritoneal fold is called the broad ligament . </li></ul><ul><li>Between its folds lie the uterus, the fallopian tubes, and the ovaries . </li></ul><ul><li>After attaining sexual maturity (post puberty), each ovary produces an ovum every four weeks. </li></ul><ul><li>If the ovum is not fertilized, then the internal lining of the uterus (the endometrium ) is shed as a mass of blood and tissue. </li></ul><ul><li>This is the process of menstruation. </li></ul>
  20. 27. UTERUS <ul><li>The uterus is a hollow, muscular organ. </li></ul><ul><li>It lies in the pelvic cavity, between the urinary bladder (in front) and the rectum (behind), covered with a fold of peritoneum. </li></ul><ul><li>The main function of the uterus is to provide protection and nourishment to the developing fetus until birth. </li></ul><ul><li>The non pregnant adult uterus is about the size of a pear (7.5 cm long, 5 cm wide, 2.5 cm thick and weighting 30-40 gm). </li></ul>
  21. 28. Sagittal Section UTERUS
  22. 29. <ul><li>The upper part is board and branches out on either Fallopian tubes . </li></ul><ul><li>At its lower end the uterus narrows down into the cervix , which leads into the vagina . </li></ul><ul><li>The uterine walls consist of strong muscle tissue lined with mucus membrane. </li></ul><ul><li>From puberty until the menopause , each month the lining of the uterus prepares itself to receive a fertilized ovum. </li></ul><ul><li>If fertilization does not occur, the lining is sloughed off, and passes out of the body – this is called menstruation. </li></ul>
  23. 31. <ul><li>CERVIX </li></ul><ul><li>Is the Latin word for ‘neck.’ </li></ul><ul><li>It refers to the lower portion of the uterus which projects into the vagina. </li></ul><ul><li>VAGINA </li></ul><ul><li>Is the passageway of the uterus. </li></ul><ul><li>The vagina and urethra are two separate passages, with separate openings. </li></ul><ul><li>The vaginal opening is surrounded and protected by folds of skin. </li></ul>
  24. 33. <ul><li>OVARIES </li></ul><ul><li>Are a pair of oval reproductive glands. </li></ul><ul><li>They are located in the pelvis, on either side of the uterus. </li></ul><ul><li>The ovaries are linked by the Fallopian tubes to the upper part of the uterus. </li></ul><ul><li>Their main functions are the production of ova and secretion of hormones – estrogen and progesterone . </li></ul>
  25. 34. <ul><li>They contain thousands of tiny structures (Graafian follicles), where ova develop. </li></ul><ul><li>Once a month, an ovary releases an ovum which passes along the Fallopian tube to the uterus. </li></ul><ul><li>Hence from the time of puberty, and until menopause the ovaries release one (or even two to three) ova each month and secrete hormones in large amounts. </li></ul>
  26. 35. OVULATION <ul><li>The process by which a mature ovum is released from an ovary. </li></ul><ul><li>Ovulation occurs at the midpoint of the menstrual cycle. </li></ul><ul><li>After ovulation an ovum remains viable and capable of being fertilized for about 24 hours. </li></ul><ul><li>Ovulation is usually accompanied by a slight rise in body temperature. </li></ul><ul><li>This is often made use of in detecting whether ovulation has occurred or not. </li></ul>
  27. 36. <ul><li>In this way the ‘natural method of birth control’ is sometimes practiced. </li></ul><ul><li>This involves abstinence from sexual intercourse for about 4 days prior to ovulation and 3 days after. </li></ul><ul><li>This method can only be practiced if the menstrual cycle are regular. </li></ul>
  28. 37. OVULATION
  29. 38. FALLOPIAN TUBE <ul><li>Are about 10 cm long. </li></ul><ul><li>On each side they connect the uterus to the ovary. </li></ul><ul><li>They are also called oviduct or uterine tubes . </li></ul><ul><li>These ducts play an important part in the fertilization of an ovum. </li></ul><ul><li>About midway between two menstrual periods, an unfertilized egg or ovum, is released from an ovary and is moved slowly to the uterus, by contractions of the muscular wall of the tube. </li></ul>
  30. 40. FERTILIZATION <ul><li>Usually takes place in the ovarian end of the tube. </li></ul><ul><li>After ejaculation , a few sperm are transported through the uterus to the ovarian ends of the Fallopian tubes within 5 to 10 minutes, due to contractions of the uterus and the tubes. </li></ul><ul><li>A sperm remains viable for about 4 days within the female genital tract. </li></ul><ul><li>However, out of the half a billion sperms deposited in the female tract, only 1000-3000 reach the tubes. </li></ul>
  31. 41. <ul><li>A single sperm fertilizes the ovum. </li></ul><ul><li>The two cells become a single cell, which inherits qualities from both parents. </li></ul><ul><li>This cell continues to divide, and this tiny, developing mass of life travels towards the uterus. </li></ul><ul><li>It usually reaches the uterus within another 3-4 days. </li></ul><ul><li>In the uterus the developing embryo attaches itself to the wall of the uterus, and draws nourishment from it. </li></ul>
  32. 42. MENSTRUATION <ul><li>Is the periodic shedding of the lining of the uterus (which is seen as a mass of blood and tissue) in women of child bearing age – that is from the age 12 or 14 to about 50 years. </li></ul><ul><li>The first occurrence of menstruation is called menarche . </li></ul><ul><li>The cyclical nature of the menstrual cycle is because of the periodic release of hormones by the hypothalamus. </li></ul><ul><li>Gonadotropin Releasing Hormone (GnRH) from the hypothalamus causes the release of Follicle Stimulation Hormone (FSH) from the ovary. </li></ul>
  33. 43. <ul><li>Under the influence of FSH a rudimentary egg cell begins to develop in the ovary. </li></ul><ul><li>This development continues for the next 14 days, i.e., from the first day of menstruation till the fourteenth day. </li></ul><ul><li>During this time, changes are also occurring in the uterus. </li></ul><ul><li>During menstruation the lining of the uterus is sloughed off. </li></ul><ul><li>This may take 1 to 4 days. </li></ul><ul><li>After the fourth day, repair of the uterine lining begins. </li></ul>
  34. 44. <ul><li>Around day 14 , the hypothalamus suddenly secretes increased amount of GnRH, this causes the ovary to secrete increased amounts of LH, this is called LH surge . </li></ul><ul><li>Under the influence of these increased amounts of LH, in the ovary the membrane bursts and the ovum or egg is released, this is called ovulation . </li></ul><ul><li>The part of the ovary from which the ovum is released, accumulates yellow pigment and is called the yellow body or corpus luteum . </li></ul><ul><li>It secretes estrogen and progesterone, which cause changes in the uterus so that it is ready for the fertilized ovum. </li></ul>
  35. 45. <ul><li>Progesterone causes a rise in body temperature, an indicator that ovulation has occurred. </li></ul><ul><li>In case the ovum is not fertilized, then at the end of 14 days from the time of ovulation the corpus luteum starts to degenerate. </li></ul><ul><li>The level of estrogen and progesterone falls and the uterine lining which was prepared to receive the fertilized ovum is now sloughed off as the menstrual flow. </li></ul><ul><li>Approximately 30 mL of blood is lost each time. </li></ul><ul><li>If the ovum has been fertilized, pregnancy follows. </li></ul>
  36. 46. <ul><li>Amenorrhea - Absence or abnormal cessation of the menses. </li></ul><ul><li>Dysmenorrhea - Difficult and painful menstruation. </li></ul><ul><li>Menorrhagia - Excessively prolonged or profuse menses. </li></ul><ul><li>Premenstrual tension (PMT) - in women of reproductive age, the regular monthly experience of physiological and emotional distress, usually during the several days preceding menses; characterized by nervousness, depression, fluid retention, and weight gain. </li></ul>