Human Reproductive system: Anatomy and physiology

he reproductive system is a collection of internal and external organs — in both males and females — that work together for the purpose of procreating, according to the Cleveland Clinic. Due to its vital role in the survival of the species, many scientists argue that the reproductive system is among the most important systems in the entire body.

1. Reproductive system Prof. Amol B Deore MVP’s Institute of Pharmaceutical Sciences, Nashik India

2. Reproduction It is the process by which our genetic material is passed on from one generation to the next generation. This maintains continuation of the species. It involves passing of genetic material from parent cells to daughter cells. This process requires the sperm from the male and the egg from the female. The fertilization is the process of union of a male sperm and female ovum to produce a fertilized egg, or zygote. When fertilization occurs, the zygote will possess 46 chromosomes (an ovum carrying 23 chromosomes and the sperm carrying 23).

3. MALE REPRODUCTIVE SYSTEM The male reproductive system consists of the testes, a series of ducts and accessory glands. Sperms are produced in the testes and are transported through the reproductive ducts: epididymis, deferent duct, ejaculatory duct, and urethra respectively. The accessory glands produce secretions that become part of semen, the fluid that is ejaculated from the urethra. These glands are the seminal vesicles, prostate gland, and bulbourethral glands (refer figure).

4. Organs of the Male Reproductive System Scrotum Penis Testes epididymis , Deferent duct , Ejaculatory duct, Seminal vesicles, prostate gland, and bulbourethral glands Urethra

5. SCROTUM Scrotum is the loose pouch-like sac of skin that covered to the testes between upper thighs. Scrotum hangs behind and below the penis. The scrotum controls temperature for of testes. The temperature within the scrotum is about 96 ˚̊ F, slightly lower than body temperature, which is necessary for the production of viable sperm.

6. PENIS The penis delivers sperms into the vagina of female reproductive tract. It is cylindrical in shape and consists of head (or glans penis), body, and root. Glans penis is covered with loose skin called the prepuce (or foreskin) . Internally, it is composed of three cylindrical masses of spongy tissue containing blood sinuses. When blood flow through these sinuses is minimal, the penis is loose and soft. Sexual stimulation triggers the dilation of the blood arteries in the penis. The blood sinuses fill with blood, and the penis becomes erect, enlarge, stuff and firm . The erect penis is capable of penetrating the female vagina to deliver sperm and semen during sexual intercourse.

7. TESTES Each testis is covered by a capsule of connective tissue called the tunica albuginea , which extends inward to form a series of compartments called lobules (refer fig). Each lobule contains one to three convoluted seminiferous tubules in which spermatogenesis occurs. Spermatogenesis begins from spermatogonia . It divided to form primary spermatocytes . Primary spermatocytes divided to form secondary spermatocytes that develop into spermatids . Spermatids develop into mature sperm cells (or spermatozoa). In the lobules, sertoli cells supply nutrients to the developing sperm cells. Leydig cells produce the male sex hormone testosterone.

8. EPIDIDYMIS The sperm that produced from the testes are immature and unable for fertilization; therefore the epididymis performs maturations of the sperm. During sexual stimulation, epididymis transports the sperm into the deferent duct. DEFERENT DUCT The deferent duct transports mature sperm to the urethra, the tube that carries urine or sperm to outside of the body, in preparation for ejaculation.

9. EJACULATORY DUCTS These are formed by the union of the deferent duct and the seminal vesicles. The ejaculatory ducts transport the sperms to 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 ejaculate semen when the man reaches orgasm .

10. ACCESSORY GLANDS The accessory glands secrete the liquid portion of the semen, the sperm-containing fluid called semen which is produced during ejaculation. The accessory glands are seminal vesicles, prostate gland and bulbourethral gland

11. SEMINAL VESICLES The seminal vesicles are sac-like pouches that attach to the vas deferens. The seminal vesicles produce a fructose-rich fluid that provides a source of energy for sperm motility . The fluid of the seminal vesicles makes up most of the volume of a man's ejaculatory fluid i.e. semen. PROSTATE GLAND The prostate gland is located below the urinary bladder. The prostate gland secretes the semen to permit sperm motility. Prostate fluids also help for nourishment of the sperms.

12. BULBOURETHRAL GLANDS They are also named as Cowper's glands, 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.  

13. SEMEN Semen is an alkaline milky sticky fluid containing mixture of sperm cells and the secretions of the seminal vesicles , the prostate , and the bulbourethral glands . The semen a transports, provide nutrients to the sperms in the male urethra and female vagina. It provides a transport medium for the swimming sperm. Typical ejaculate is 2.5 to 5 ml in volume Normal sperm count is 50 to 150 millions/mL

14. Composition of semen The semen is comprise of fructose, antibiotic seminalplasmin , hyaluronidase enzyme, acid phosphatase enzyme, prostaglandins, lysozymes, citric acid and certain clotting factors.

15. Sperms Sperm production begins at puberty (10 to 14 years of age), and millions of sperm are formed each day in the testes. Sperms mature at the rate of about 300 million per day and once released cannot survive more than 48 hours within female reproductive tract. A sperm cell is composed of head, a mid-piece and tail. The head contains the nuclear material (DNA) and a lysosome like structure called acrosome which contains enzymes hyaluronidase and proteinases that help in penetration of sperms in the female egg.

16. Mid-piece containing mitochondrion provides ATP energy for movement of sperms in female reproductive tract. The tail helps to propel the sperms along its way. Sperm Count : average range of sperms is about 50 to 100 million per mL of semen.

17. PUBERTY Puberty is the development of secondary sexual characteristics in male at age of 14-15 years due to increased secretion of GnRH , FSH, LH and testosterone hormones . Physical and psychological maturity changes are as follows: Increase in rate of production and maturation of sperms in the testes i.e. spermatogenesis. Enlargement of testes and penis. Increased in size of prostate gland, seminal vesicles and bulbourethral gland. Enlargement of the larynx and thickening of the vocal cords results in a deep voice.

18. Growth of hairs on face (beard), chest, underarm, abdomen and pubis. Growth of the muscle & bone and marked increased in height and weight. Increased protein synthesis in skeletal muscles. The skin thickens and become more oily. It stimulates aggressive behavior. It controls the development, growth, and maintenance of the male sex organs. It stimulates sex drive and desire.

19. DISORDERS Male infertility Infertility is an inability to fertilize a secondary oocyte when the sperm count falls below 20 million per mL of semen in the male. Then male is considered to be infertile. Male fertility requires production of adequate quantities of normal sperm count by testes, transportation of sperms through the ducts and satisfactory deposition in the vagina. The main causes of male infertility include: X-rays, infections, malnutrition, significantly higher than normal temperature of scrotum. These factors may cause degenerative changes and produce male infertility.

20. Impotent Impotency is an inability of penis erection (enlargement and stiffness) long enough for sexual intercourse. Such male is considered to be impotent. It may be due constriction of blood sinuses in penis. The main causes of impotency include diabetes mellitus, physical abnormality of penis, syphilis, neurological disturbances, testosterone deficiency and certain medicines including alcohol, antidepressants, antihypertensive, narcotics etc.

21. Female reproductive system The female reproductive system includes external genitalia and internal genitalia i.e. reproductive organs.

22. The term vulva refers to the external genitalia of the female (refer fig15.5). The following components comprise the vulva: Mons pubis : It is an elevation of adipose tissue covered by skin and coarse pubic hair that cushions the pubic symphysis. Labia majora : From the mons pubis, two longitudinal folds of skin are referred as labia majora . They are covered by pubic hair and contain an adipose tissue, sebaceous (oil) glands, and apocrine sweat glands. Labia minora : Medial to the labia majora , two smaller folds of skin called the labia minora . They are covered by many sebaceous glands.

23. Clitoris: The clitoris is a small cylindrical mass composed of two small erectile bodies. The clitoris is located at the anterior junction of the labia minora . The clitoris is like to the glans penis in males. The clitoris is capable of enlargement upon in sexual excitement in the female. Vestibule : The region between the labia minora is the vestibule. Within the vestibule are the hymen, the vaginal orifice, the external urethral orifice, and the openings of the ducts of Bartholin’s glands .

24. The main internal structures of the female reproductive system include: The vagina The uterus The ovaries The Uterine or fallopian tubes

25. VAGINA

26. Functions of vagina The functions of the vagina are to receive sperm from the penis during sexual intercourse. It serves as a passageway for the menstrual flow. It became the birth canal at the end of pregnancy. The vaginal mucosa after puberty secretes organic acids to create an acidic pH environment that helps to inhibit the growth of pathogens.

27. UTERUS (WOMB ) The uterus is a hollow, pear-shaped organ that is the site of menstruation, implantation and development of fetus during pregnancy. The uterus is divided into two parts: The fundus is the upper portion above the entry of the fallopian tubes, and the body is the large central portion. The narrow, lower end of the uterus is the cervix , which opens into the vagina. The mucus layer of cervix produce a secretion called cervical mucus. Generally female of reproductive age secrete 20 to 60 mL of mucus per day.

28. The wall of the uterus is made of three layers of tissue. Perimetrium : It is the outermost layer of uterus made of serous membrane. Myometrium: The middle layer of the uterus i.e. myometrium is the smooth muscle layer; during pregnancy these smooth muscle cells increase in size to accommodate the growing fetus. During childbirth, contraction of smooth to expel the fetus from the uterus. Endometrium: The innermost layer is the highly vascular endometrium. The endometrium is divided into two layers. The stratum functionalis and stratum basalis . The stratum functionalis is shed approximately every 28 days in in noon-pregnant woman by the process called menstruation cycle . The stratum basalis is permanent and give rise to new stratum functionalis after each menstruation.

29. OVARIES The ovaries are small, oval-shaped glands that are located in the upper pelvic cavity, on both sides of uterus. They are 2.5 to 3.5 cm long and 2 cm wide. Each ovary is attached to uterus by ovarian ligament. The surface of an ovary is covered with germinal epithelium . The capsule of an ovary consists of connective tissue called the tunica albuginea . Before puberty, ovary consists of primordial follicles. At maturity, each primordial follicle develops into primary follicle (with primary oocyte)

30. The primary follicle matures, and develops in to secondary follicle . A mature secondary follicle with a mature egg is called a graafian follicle (with secondary oocyte) , which is ready for ovulation . Ovulation : rupturing of Graafian follicle and release of female egg (ovum) near the fallopian tube . The empty graafian follicle converted into the corpus luteum , which secretes estrogen and progesterone. The corpus luteum eventually degenerates into the corpus albicans .

31. Functions of ovary Oogenesis , or formation of the female sex cells, begins in the developing female fetus where female stem cells called oogonia divide by mitosis to produce primary oocytes . The ovaries produce and release ovum ( eggs ) in ovulation. Ovulation : rupturing of Graafian follicle and release of female egg (ovum) near the fallopian tube . They also secrete the female sex hormones estrogen and progesterone .

32. UTERINE TUBES (OR FALLOPIAN TUBES ) The female body contains two fallopian tubes which transport the ovum from the ovaries to the uterus. Each fallopian tube is about 10 cm long. It consists of a funnel-shaped end called the infundibulum. The infundibulum is surrounded by finger-like projections called the fimbriae. Fimbriae are attached to the lateral end of the ovary. The ampulla of the fallopian tube is the longest portion, making up about two-third of its length. The isthmus of fallopian tube is the short portion that joins the uterus.

33. Functions of Fallopian Tubes Approximately once a month an ovum ruptures from the surface of an ovary near the infundibulum of the uterine tube, a process called as ovulation . The ovum is brush off by ciliary action of the infundibulum and by the waving fimbriae, which create a current that transports the ovum into the uterine tube. The two uterine or fallopian tubes transport the ova from the ovaries to the uterus. Fertilization usually takes place in the fallopian tube. If not fertilized, an ovum dies within 24 to 48 hours and disintegrates, either in the tube or the uterus. If fertilized, the ovum becomes a zygote and is swept into the uterus; this takes about 4 to 5 days. The ovum is moved by peristalsis and the ciliary action toward the uterus. Fertilization of male sperm and female ovum usually occurs in the ampulla of the uterine tube within 24 hours after ovulation.

34. PUBERTY IN FEMALE Puberty is the development of the secondary sexual characteristics and maturity of internal genitalia usually at the age of 10 to 14 years in female. It is the sign of the childbearing period. Puberty maturity changes are due to increased secretion of GnRH , FSH, LH, estrogen & progesterone hormones.

35. Physical and psychological maturity changes are as follows: Menstruation cycle begins Increased growth of ovarian follicles in ovary Maturation of ovaries, uterus and fallopian tubes Enlargement and development of breast and vagina Increased growth in height and widening of pelvic girdle (become broad) Mental and emotional maturity Increased deposition of fats on breast, abdomen, mons -pubis and hips Increased protein metabolism Increased voice pitch Growth of underarm (axillary) and mons pubic hairs Stimulates sebaceous glands to secrete sebum thereby giving anti-acne action

36. MENSTRUAL CYCLE This is a series of changes in ovary and wall of uterus in a non-pregnant female throughout the childbearing period. It is essential part of making sexual reproduction. Menstrual cycle is stimulated by changes in levels of hormones in the blood. The duration of menstrual cycle is normally about 28-35 days and occurs in three phases: Menstrual (follicular) phase: Ovulatory phase: Secretory Phase:

37. MENOPAUSE It is the period between the age group of 45-55 years, marking the end of childbearing period of the female. It is caused by changes in sex hormone levels due to which ovulation & menstrual cycle become irregular. The ovaries become non-responsive to FSH, LH, estrogen and progesterone hormones.

38. Menopause is characterized by: Discontinuation of menstruation cycle Sex organ weaken Primary follicles so not undergo normal development Shrinking of the breasts Loss of bones and bone density i.e. osteoporosis Pelvic and underarm hairs become thin Increased sweating and palpitation causing discomfort Disturbances of normal sleep pattern (irregular sleep) Episodes of uncharacteristic behavior: i.e. irritability, mood changes, insomnia and depression Gradual thinning of skin Vaginal dryness Muscular pain Weight gain

39. Disorders Gonorrhea Gonorrhea is a sexually transmitted disease caused by the infection of Neisseria gonorrhoeae to the female vagina and the male urethra. Men experience burning sensations during urination, and discharge of pus from the urethra . In females, infection may occur in the urethra, vagina and cervix and often discharge of pus. The vaginal fluid is the main source of infection, and bacteria are transmitted by direct contact usually sexual intercourse or during passage of a newborn through the vagina (birth canal). Female infertility Infertility is the inability to get pregnant after a year of unprotected sexual intercourse. Both men and women can be infertile. The main causes of female infertility include: damaged fallopian tube, hormonal imbalance, ovarian disease, and certain conditions of uterus.

40. Thanks