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Human reproductive system

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FEMALE AND MALE REPRODUCTIVE SYSTEM

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Human reproductive system

  1. 1. Human Reproductive System G5 PBL
  2. 2. Objectives: ● Male main reproductive organs. ● Female main reproductive organs. ● Male hormones. ● Female hormones. ● Oogenesis ● Spermatogenesis ● Infertility in both men and women ● Vitro Fertilization
  3. 3. The Male Reproductive System The purpose of the organs of the male reproductive system is to perform the following functions: ● To produce, maintain, and transport sperm (the male reproductive cells) and protective fluid (semen) ● To discharge sperm within the female reproductive tract during sex ● To produce and secrete male sex hormones responsible for maintaining the male reproductive system Unlike the female reproductive system, most of the male reproductive system is located outside of the body. These external structures include the penis, scrotum, and testicles.
  4. 4. Organs of the Male Reproductive System ● Testicles (testes): These are oval organs about the size of large olives that lie in the scrotum, secured at either end by a structure called the spermatic cord. Most men have two testes. The testes are responsible for making testosterone, the primary male sex hormone, and for generating sperm. Within the testes are coiled masses of tubes called seminiferous tubules. These tubes are responsible for producing sperm cells.
  5. 5. ● Scrotum: This is the loose pouch-like sac of skin that hangs behind and below the penis. It contains the testicles (also called testes), as well as many nerves and blood vessels. The scrotum acts as a "climate control system" for the testes. For normal sperm development, the testes must be at a temperature slightly cooler than body temperature. Special muscles in the wall of the scrotum allow it to contract and relax, moving the testicles closer to the body for warmth or farther away from the body to cool the temperature. ● Epididymis: The epididymis is a long, coiled tube that rests on the backside of each testicle. It transports and stores sperm cells that are produced in the testes. It also is the job of the epididymis to bring the sperm to maturity, since the sperm that emerge from the testes are immature and incapable of fertilization. During sexual arousal, contractions force the sperm into the vas deferens.
  6. 6. ● Vas deferens: The vas deferens is a long, muscular tube that travels from the epididymis into the pelvic cavity, to just behind the bladder. The vas deferens transports mature sperm to the urethra, the tube that carries urine or sperm to outside of the body, in preparation for ejaculation. ● Ejaculatory ducts: These are formed by the fusion of the vas deferens and the seminal vesicles (see below). The ejaculatory ducts empty into the urethra. ● Urethra: The urethra is the tube that carries urine from the bladder to outside of the body. In males, it has the additional function of ejaculating semen when the man reaches orgasm. When the penis is erect during sex, the flow of urine is blocked from the urethra, allowing only semen to be ejaculated at orgasm.
  7. 7. ● Seminal vesicles: The seminal vesicles are sac-like pouches that attach to the vas deferens near the base of the bladder. The seminal vesicles produce a sugar-rich fluid (fructose) that provides sperm with a source of energy to help them move. The fluid of the seminal vesicles makes up most of the volume of a man's ejaculatory fluid, or ejaculate. ● Prostate gland: The prostate gland is a walnut-sized structure that is located below the urinary bladder in front of the rectum. The prostate gland contributes additional fluid to the ejaculate. Prostate fluids also help to nourish the sperm. The urethra, which carries the ejaculate to be expelled during orgasm, runs through the center of the prostate gland.
  8. 8. ● Bulbourethral glands: Also called Cowper's glands, these are pea-sized structures located on the sides of the urethra just below the prostate gland. These glands produce a clear, slippery fluid that empties directly into the urethra. This fluid serves to lubricate the urethra and to neutralize any acidity that may be present due to residual drops of urine in the urethra. ● Penis: This is the male organ used in sexual intercourse. It has three parts: the root, which attaches to the wall of the abdomen; the body, or shaft; and the glans, which is the cone-shaped part at the end of the penis. The opening of the urethra, the tube that transports semen and urine, is at the tip of the penis. Semen, which contains sperm (reproductive cells), is expelled (ejaculated) through the end of the penis when the man reaches sexual climax (orgasm). When the penis is erect, the flow of urine is blocked from the urethra, allowing only semen to be ejaculated at orgasm.
  9. 9. Testes ● ●
  10. 10. testes ● ● ●
  11. 11. SPERM A sperm has three main parts: 1. The head of the sperm contains the nucleus. The nucleus holds the DNA of the cell. The head also contains enzymes that help the sperm break through the cell membrane of an egg. 2 . The midpiece of the sperm is packed with mitochondria. Mitochondria are organelles in cells that produce energy. Sperm use the energy in the midpiece to move.
  12. 12. 3. The tail of the sperm moves like a propeller, around and around. This tail is a long flagella that pushes the sperm forward. A sperm can travel about 30 inches per hour. Functions of the spermatozoon: The main function of the spermatozoon is to carry the paternal genetic and to activate the ovum.
  13. 13. Spermatogenesis ● In humans, spermatogenesis takes 65–75 days. It begins with the spermatogonia, which contain the diploid (2n) number of chromosomes . ● Primary spermatocytes, like spermatogonia, are diploid (2n); that is, they have 46 chromosomes. Shortly after it forms, each primary spermatocyte replicates its DNA and then meiosis begins . In meiosis I, homologous pairs of chromosomes line up at the metaphase plate, and crossing-over occurs. The two cells formed by meiosis I are called secondary spermatocytes.
  14. 14. ● Each secondary spermatocyte has 23 chromosomes, the haploid number (n). Each chromosome within a secondary spermatocyte, is made up of two chromatids. No replication of DNA occurs in the secondary spermatocytes. ● In meiosis II, the chromosomes line up in single file along the metaphase plate, and the two chromatids of each chromosome separate. The four haploid cells resulting from meiosis II are called spermatids ● A single primary spermatocyte therefore produces four spermatids via two rounds of cell division (meiosis I and meiosis II). . No cell division occurs in spermiogenesis; each spermatid becomes a single sperm cell.
  15. 15. Hormones ● Spermatogenesis is controlled by hormonal secretions from hypothalamus and pituitary gland . The hypothalamus release gonadotropin–releasing hormone (GnRH) which control the release of the anterior pituitary gonadotropin, follicle – stimulating hormone (FSH) and luteinizing hormone (LH) . ● FSH stimulates spermatogenesis by stimulating the sertoli cells to complete the development of sperms from spermatids . The sertoli cells are elongated cells found in the seminiferous tubules of the testis and they nourish the spermatids. .
  16. 16. ● LH stimulates leydig cells to release testosterone which causes the growth and development of germinal epithelial to form sperms . ● Inhibin hormone is produced by the sertoli cells and serves to control the spermatogenesis at normal rate .
  17. 17. Causes of Infertility in Men The most frequent cause of infertility in males is low sperm count and/or a large proportion of abnormal sperm, which can be due to environmental influences. It appears that a sedentary lifestyle coupled with smoking and alcohol consumption is most often the cause of male infertility. when males spend most of the day driving or sitting in front of a computer or TV, the testes’ temperature remains too high for adequate sperm prodution.
  18. 18. Female Reproductive System ● The female reproductive system is immature at birth and develops to maturity at puberty to be able to produce gametes, and to carry a fetus to full term ● Main organs: 1- Vagina. 4 - Fallopian tube. 2 - Cervix. 5- Ovaries. 3 - Uterus.
  19. 19. Vagina ● it is a fibro-muscular tube, about 10 cm long that extends from the cervix of the uterus to outside. ● Vagina is located between the rectum and the urinary bladder. ● The vigina serves as a passageway for menstual flow and is the birth canal during childbirth.
  20. 20. Cervix ● The cervix is the neck of the uterus, the lower, narrow portion where it joins with the upper part of the vagina. ● It is cylindrical or conical in shape and protrudes through the upper anterior vaginal wall. ● Approximately half its length is visible, the remainder lies above the vagina beyond view.
  21. 21. Uterus ● The uterus is a muscular organ that receives the fertilized oocyte and provide an appropriate environment for developing fetus. ● The uterus incubates the embryo. ● The main part of the uterus (which sites in the pelvic cavity) is called the body of the uterus, while the rounded part above the entrance of the fallopian tubes is the fundus. ● The thick wall and lining of the uterus is composed of 3 layers: Endometrium, myometrium and perimetrium.
  22. 22. Fallopian tube. ● The Fallopian tubes are two tubes leading from the ovaries into the uterus. ● On maturity of an ovum, the follicle and the ovary's wall rupture, allowing the ovum to escape and enter the Fallopian tube. ● There it travels toward the uterus, pushed along by movements of cilia on the inner lining of the tubes. - Its surface is lined by a serosa and subjacent connective tissue. ● If the ovum is fertilized while in the Fallopian tube, then it normally implants in the endometrium when it reaches the uterus, which signals the beginning of pregnancy.
  23. 23. ovary ● The two ovaries are the primary female reproductive organs or gonads. ● Ovaries are small, almond-shaped organs located near lateral walls of pelvic cavity. ● The ovaries are held in place by various ligaments which attached them to the uterus and the pelvis. ● The ovary contains ovarian follicles, in which eggs develop. ● Once a follicle is mature, it ruptures and the egg is ejected from the ovary into the fallopian tubes./ This is called (ovulation)
  24. 24. Function of ovary 1 - Production of female gametes (oocytes). 2 - Secretion of female sex hormones (estrogen , progestin)
  25. 25. The functional units of the ovary are : 1 - Primordial follicles: ● very prevalent ; located in the periphery of the cortex. ● a single layer of squamous follicular cells surround the oocyte. 2 - Growing follicles : ● develop into secondary follicles.
  26. 26. 3 - Mature follicles: ● Follicle reaches maximum size before ovulation, *All other female reproductive organs help to transport and provide nutrients to the egg or developing fetus.
  27. 27. Components of the Ovary ● Surface: The surface layer of the ovary is formed by simple cuboidal epithelium, known as germinal epithelium. ● Cortex: The cortex (outer part) of the ovary is largely comprised of a connective tissue stroma. It supports thousands of follicles. Each primordial follicle contains an oocyte surrounded by a single layer of follicular cells. ● Medulla: The medulla (inner part) is composed of supporting stroma and contains a rich neurovascular network which enters the hilum of ovary from the mesovarium.
  28. 28. Ovum The ovum ( the egg cell ) is the female reproductive cell in the female reproductive system , It is large in size ( as sesame seed size ) due the the storage of the nutrient materials . The ovum is not capable of active movement , and it is much larger than the sperms cells , when the ovum joins with the sperms during the fertilization , and a diploid cell ( the zygote ) is formed , and the embryo is formed , which gradually grows into a new organism . The ovum is a spherical cell and not mobile ( static ) , It is one of the largest cells in the human body , it is visible to the naked eye without the aid of a microscope or other magnification device , and it is approximately 0.12 mm in diameter .
  29. 29. Ovum The ovum consists of the nucleus , the cytoplasm and the cellular membrane ( that surrounds the cell from outside ) , The nucleus contains one half of the genetic materials ( the chromosomes ) , and the cytoplasm stores the food and the nutrients .
  30. 30. ovum The function of the ovum The function of the ovum is to carry the set of chromosomes contributed by the female and It creates the right environment to enable the fertilization by the sperm . The ova provide the nutrients for the growing embryo until it sinks into the uterus and the placenta takes over .
  31. 31. Oogenesis Oogenesis: the process where the ova or female gametes are produced (“the beginning of an egg”). it occurs in the outermost layers of the ovaries. As with sperm production, oogenesis starts with a germ cell, called an oogonium (plural: oogonia), but this cell undergoes mitosis to increase in number, eventually resulting in up to one to two million cells in the embryo .
  32. 32. Oogenesis 1. The cell starting meiosis is called a primary oocyte. This cell will begin the first meiotic division, but be arrested in its progress in the first prophase stage. ✓ At the time of birth, all future eggs are in the prophase stage.
  33. 33. Oogenesis 2. At adolescence, anterior pituitary hormones cause the development of a number of follicles in an ovary. This results in the primary oocyte finishing the first meiotic division. The cell divides unequally, with most of the cellular material and organelles going to one cell, called a secondary oocyte, and only one set of chromosomes and a small amount of cytoplasm going to the other cell. This second cell is called a polar body and usually dies. 3. A secondary meiotic arrest occurs, this time at the metaphase II stage.
  34. 34. Oogenesis 4. At ovulation, this secondary oocyte will be released and travel toward the uterus through the oviduct. 5. If the secondary oocyte is fertilized, the cell continues through the meiosis II, completing meiosis, producing a second polar body and a fertilized egg containing all 46 chromosomes of a human being, half of them coming from the sperm.
  35. 35. Reproductive Hormones in female ● The hypothalamus, pituitary, and ovaries interact to regulate female reproduction ● Hypothalamus releases Gonadotropin Releasing Hormone (GRH)which binds with receptors in Anterior Pituitary ● Anterior Pituitary releases Follicle Stimulating Hormone (FSH)and Luteinizing Hormone(LH)pass in blood to the site of action ● FSH acts on receptors in ovaries to stimulate development of the egg follicles ● LH causes rupture of egg follicles. ● Rupture of egg triggers production of estrogensand progesteronefrom remaining tissues of follicle, corpus luteum. ● These hormones travel in blood to the brain ● Hypothalamus senses levels, then may decrease release of GRH (negative feedback mechanism).
  36. 36. MENSTRUAL (uterine) CYCLE The events of the uterine, or menstrual, cycle are the cyclic changes that the endometrium, or mucosa of the uterus, goes through month after month as it responds to changes in the levels of ovarian hormones in the blood. The cyclic production of estrogens and progesterone by the ovaries is, in turn, regulated by the anterior pituitary gonadotropic hormones, FSH and LH. Ovulation typically occurs midway in the cycles, on or about day 14.
  37. 37. Uterine Cycle • Reflects hormonal changes during ovarian cycle • Averages 28 days • Consists of three phases 1) Menstrual phase (decreased oestrogen & progesterone) 1-5 days • Uterine lining is shed. 5-7 days 2) Proliferative phase (oestrogen) 6 -14 days • Endometrium renewed in preparation for possible pregnancy 3) Secretory or progestational phase (progesterone). 15- 28 days • Coincides with luteal phase. Endometrium develops
  38. 38. 1) Menstrual phase – Characterized by discharge of blood and endometrial debris from vagina – First day of menstruation is considered start of new cycle – Coincides with end of ovarian luteal phase and onset of follicular phase – Triggered by decreased oestrogen and progesterone: – hormones decrease when CL degenerates – Release of uterine prostaglandin · Causes vasoconstriction of endometrial vessels – Disrupts blood supply – Causes death of endometrium · Stimulates mild rhythmic contractions of uterine myometrium – Helps expel the menstrual flow
  39. 39. 2) Proliferative phase: Begins concurrent with last portion of ovarian follicular phase. Uterus prepares for fertilized ovum: – Endometrium starts to repair itself and proliferate under influence of oestrogen from newly-growing follicles – Oestrogen-dominant proliferative phase lasts from end of menstruation to ovulation – Peak oestrogen levels trigger LH surge responsible for ovulation
  40. 40. 3) Secretory phase: Endometrium is prepared for implantation. – Blood supply increased – Glands enlarge and secrete glycogen-rich fluids – Secretory phase conditions promoted by progesterone – Uterus enters this phase after ovulation when new corpus luteum is formed – Corpus luteum secretes large amounts of progesterone and oestrogen ● Progesterone converts endometrium to highly vascularized, glycogen-filled tissue – Endometrial glands actively secrete glycogen – If fertilization and implantation do not occur ● Corpus luteum degenerates ● New follicular phase and menstrual phase begin again
  41. 41. Hormonal control of the cycle GnRH Gonadotropins (FSH and LH) Oestrogen and progesterone ● FSH: follicle stimulating hormone growth and development of follicles ● LH: luteinising hormone causes ovulation, development of corpus luteum ● Inhibin: decreases FSH, not LH – Oestrogen secreted first from the follicle, then from the corpus luteum – Progesterone secreted from the corpus luteum – LH and FSH secreted from the anterior pituitary – Oestrogen and progesterone inhibit LH and FSH secretion
  42. 42. Hormonal control of the cycle Oestrogens · Stimulate oogenesis and follicle development · Promote proliferative-phase uterine conditions · Induce expression of uterine progesterone receptors · Induce expression of granulosa cell LH receptors · Secondary sexual characteristics · Breast growth during pregnancy Progesterone · Promotes secretory-phase uterine conditions · Suppresses uterine contraction during pregnancy · Promotes growth of glandular breast tissue but suppresses milk production
  43. 43. A.Fluctuation of gonadotropin levels: Fluctuating levels of pituitary gonadotropins (FSH and LH) in the blood regulate the events of the ovarian cycle. (b) Ovarian cycle: Structural changes in the ovarian follicles during the ovarian cycle are correlated with (d) changes in the endometrium of the uterus during the uterine cycle. Hormonal interactions of the female cycles
  44. 44. (c) Fluctuation of ovarian hormone levels: Fluctuating levels of ovarian hormones(estrogens and progesterone) cause the endometrial changes of the uterine cycle. (d) The three phases of the uterine cycle: • Menstrual: Shedding of the functional layer of the endometrium. • Proliferative: Rebuilding of the functional layer of the endometrium. • Secretory: Begins immediately after ovulation. Enrichment of the blood supply and glandular secretion of nutrients prepare the endometrium to receive an embryo.
  45. 45. Fertilization ● Fertilization is the fusion of sperm and egg ● Mucus becomes sticky after ovulation and this blocks sperm. ● Thus, fertilization is most likely on the day of ovulation or a day or so preceding ● Successful penetration of the egg by a sperm is dependent on many sperm surrounding the egg. ● The ovum completes the second meiotic division after sperm entry ● Conception: Fertilization and implantation Implantation ● After about 3-5 days after fertilization the embryo implants in the endometrium ● Membranes that develop around the embryo secrete hCG, human chorionic gonadotrophin. ● After ~ 3 months, uterine tissues begin to form the placenta, the corpus luteum degrades and the placenta takes over nourishment of the embryo
  46. 46. CAUSES OF INFERTILITY IN WOMEN The most common causes of female infertility include problems with ovulation, damage to fallopian tubes or uterus, or problems with the cervix. Age can contribute to infertility because as a woman ages, her fertility naturally tends to decrease.
  47. 47. Ovulation problems may be caused by one or more of the following: ● A hormone imbalance ● A tumor or cyst ● Eating disorders such as anorexia or bulimia ● Alcohol or drug use ● Thyroid gland problems ● Excess weight ● Stress ● Intense exercise that causes a significant loss of body fat ● Extremely brief menstrual cycles
  48. 48. Damage to the fallopian tubes or uterus can be caused by one or more of the following: ● Pelvic inflammatory disease ● A previous infection ● Polyps in the uterus ● Endometriosis or fibroids ● Scar tissue or adhesions ● Chronic medical illness ● A previous ectopic (tubal) pregnancy ● A birth defect ● DES syndrome (The medication DES, given to women to prevent miscarriage or premature birth can result in fertility problems for their children.)
  49. 49. In Vitro Fertilization (IVF) ● In-vitro fertilization means fertilization outside of female body. It is also known as test tube baby technique. It is the most effective type of assisted reproductive technology ● It is used when a woman’s fallopian tubes are blocked or when a man produces too few sperms. ● In the IVF procedure, a small incision is made near the umbilicus of female under general anaesthetic and secondary oocytes are sucked by a hollow needle. ● Sperms are collected from male partner and washed in a culture to remove seminal fluid. ● About 100,000 sperms are added to each sperm about 6 hours after collection of eggs. This is done in a glass dish. ● The fertilized eggs are grown for about 2 days, after which they are at 2 to 8 cell stage. ● After examination under a microscope, the embryo are transferred through cervix into the uterus using a fine plastic tube i.e., embryo transfer.
  50. 50. references books: ● Essentials of Human Anatomy Physiology - Marieb, Elaine N. chapter 16 page 551 ● Principles of Anatomy and Physiology 13th ed - G. Tortora, B. Derrickson (Wiley, 2012) BBS
  51. 51. references wibesite: ● http://www.online-sciences.com/the-living-organisms/the-structure-and-function-of-the-ovum-in-the-female-reproductive-sy stem/ ● https://www.boundless.com/biology/textbooks/boundless-biology-textbook/animal-reproduction-and-development-43/huma n-reproductive-anatomy-and-gametogenesis-239/gametogenesis-spermatogenesis-and-oogenesis-891-12142/ ● http://study.com/academy/lesson/oogenesis-how-the-female-reproductive-system-produces-eggs.html ●
  52. 52. Thank you

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