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The Reproductive System

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Presentation on theme: "The Reproductive System"— Presentation transcript:

1 The Reproductive System
17 The Reproductive System Chapter Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 The Human Life Cycle Puberty – sequence of events that lead to sexual maturity Occurs between the ages of 11 and 13 for females Occurs between the ages of 14 and 16 for males Functions of the reproductive organs Production and transport of gametes To deliver sperm (in males) and receive sperm (in females) The uterus houses the fertilized egg and allows it to develop within the female body Production of sex hormones

3 The Male Reproductive System

4 Male Reproductive System
The Testes Produce sperm and the male sex hormones Located outside of the abdominal cavity within the scrotum Anatomy of a Testis Enclosed by a fibrous capsule Divided into lobules that each contain one to three seminiferous tubules Seminiferous tubules contain cells that produce sperm Interstitial cells produce androgens

5 Fig 17.4

6 Male Reproductive System
Spermatogenesis Production of sperm Includes the process of meiosis Two types of cells in the seminiferous tubules: Germ cells – involved in spermatogenesis Spermatogonia Primary spermatocytes Secondary spermatocytes Spermatids Sustentacular (Sertoli) cells – support, nourish, and regulate the development of cells undergoing spermatogenesis


8 Male Reproductive System
Spermatids mature into spermatozoa (sperm) Sperm have three distinct parts: Head – contains a nucleus covered by the acrosome Middle piece – contains mitochondria Tail – provides motility Sperm typically survive for about 48 hours

9 Male Reproductive System
Male Internal Accessory Organs Epididymides Lining consists of ciliated pseudostratified columnar epithelium Stores and supports sperm Peristaltic contractions move sperm along as they mature Vas Deferens Continuation of the epididymis Lined by pseudostratified columnar epithelium Contained within the spermatic cord Widens at the ampulla, located at the posterior base of the urinary bladder Joins with the duct of a seminal vesicle to form an ejaculatory duct The ejaculatory duct passes through the prostate gland to join the urethra

10 Male Reproductive System
Seminal Vesicles Lateral to each vas deferens Secrete an alkaline fluid that contains fructose and prostaglandins Prostate Encircles the urethra Secretes a fluid that helps adjust the pH of seminal fluid and enhances the motility of sperm Bulbourethral Glands (Cowper glands) Inferior to prostate gland Secrete a mucuslike fluid that lubricates the end of the penis

11 Fig 17.6

12 Male Reproductive System
Male Sexual Response External genitals Penis Male organ of sexual intercourse Internal root and an external shaft Erectile tissue Contains distensible blood spaces Autonomic nerves causes erectile tissue to fill with blood Veins that take blood away from the penis are compressed Penis becomes erect Scrotum


14 Male Reproductive System
Regulation of Male Hormone Levels At the start of puberty the hypothalamus begins to increase its production of gonadotropin-releasing hormone (GnRH) GnRH stimulates the anterior pituitary to produce the gonadotropic hormones FSH (follicle-stimulating hormone) promotes spermatogenesis LH (luteinizing hormone) Also called interstitial cell-stimulating hormone (ICSH) Stimulates androgen production

15 Fig 17.8

16 Male Reproductive System
Negative Feedback Mechanisms Maintains testosterone production at a fairly constant level Maintains the continuous production of sperm Testosterone Necessary for the normal development and function of the male sex organs Secondary sex characteristics Hair growth Activity of cutaneous glands Deeper pitch to the voice Muscle strength

17 The Female Reproductive System
Fig 17.9

18 Female Reproductive System
The Ovary Lie on either side of the uterus Held in place by several ligaments Made up of an outer cortex and an inner medulla Follicles contain an immature ovum called an oocyte

19 Fig 17.10

20 Female Reproductive System
Oogenesis Production of an ovum Includes the process of meiosis A primary oocyte undergoes meiosis I to become a secondary oocyte A secondary oocyte undergoes meiosis II only if it is fertilized by a sperm cell Begins within a follicle Primary follicle  secondary follicle  vesicular (Graafian) follicle Follicular fluid surrounds the oocyte Primary oocyte divides and produces two cells Secondary oocyte Polar body Ovulation – vesicular follicle bursts and releases the secondary follicle

21 Female Reproductive System
The secondary oocyte (egg) enters a uterine tube If fertilization occurs, meiosis II will commence and a zygote will form Corpus luteum – follicle that has lost its egg If implantation does not occur, it will degenerate after about 10 days If implantation does occur, the corpus luteum secretes hormones for about six months

22 Fig 17.11

23 Female Reproductive System
Female Internal Accessory Organs Uterine tubes (fallopian tubes) Extend from the uterus to the ovaries Fimbriae sweep over the ovary at the time of ovulation Egg is propelled toward the uterus by ciliary action and by muscular contractions Fertilization normally occur in the upper one-third of a uterine tube An ectopic pregnancy occurs if the embryo becomes imbedded in the wall of a uterine tube

24 Fig 17.12

25 Female Reproductive System
Uterus Thick-walled, muscular organ Three sections: Fundus Body Cervix Location of embryo development Endometrium Participates in formation of the placenta Varies in thickness during the menstrual cycle of a nonpregnant female Vagina Tube that serves as the birth canal Facilitates intercourse

26 Female Reproductive System
External Genitals (vulva) Labia majora Mons pubis Labia minora Clitoris Vestibule

27 Female Reproductive System
Regulation of Female Hormone Levels At the start of puberty the hypothalamus begins to increase its production of gonadotropin-releasing hormone (GnRH) GnRH stimulates the anterior pituitary to produce the gonadotropic hormones FSH and LH Stimulate the ovaries to produce and release ova Cause elevated estrogen and progesterone production by the ovaries Estrogen Stimulates the growth of the uterus and the vagina Needed for maturation of the ovum and for the onset of the menstrual cycle Causes the development of secondary sex characteristics Both estrogen and progesterone are needed for breast development

28 Female Reproductive System
Menstrual Cycle Pre-ovulation events Follicular phase of the ovary – several follicles begin developing in the ovary Only one follicle continues developing and secretes increasing amounts of estrogen Causes more GnRH to be released from the hypothalamus LH surge causes ovulation First menstruation and then the proliferative phase occur in the uterus

29 Female Reproductive System
Post-ovulation events Emptied follicle becomes the corpus luteum (luteal phase) Secretes progesterone and some estrogen As levels of progesterone increase, LH levels decline and the corpus luteum begins to degenerate Secretory phase begins in the uterus Endometrium thickens Uterine glands mature and produce a thick secretion If fertilization and implantation occur, human chorionic gonadotropin (HCG) is released by the developing placenta

30 Female Reproductive System
Menopause Menstrual cycle ceases Ovaries are no longer responsive to gonadotropins Ovaries secrete low levels of estrogen and progesterone Uterine cycle becomes irregular Hormonal changes cause physical symptoms “hot flashes” Dizziness Headaches Insomnia Depression

31 Female Reproductive System
Female Breast and Lactation Budding of the breasts occurs during puberty Followed by development of lobes and deposition of adipose tissue During pregnancy, breast enlarge and ducts and alveoli increase in number and size Usually no milk is produced during pregnancy Prolactin is needed for lactation to begin After birth, prolactin is secreted from the anterior pituitary Colostrum is produced for the first few days after birth Continued production of milk requires suckling

32 Fig 17.15

33 Control of Reproduction and STDs
Contraception Prevention of pregnancy A health care provider should be consulted Methods: Natural Non-prescription Prescription hormonal Prescription barrier Surgical sterilization Research continues for new methods

34 Control of Reproduction and STDs

35 Control of Reproduction and STDs

36 Control of Reproduction and STDs

37 Control of Reproduction and STDs

38 Control of Reproduction and STDs

39 Fig 17.16

40 Control of Reproduction and STDs
Emergency contraception “Morning-after pills” Prevents pregnancy after unprotected intercourse Medication upsets the normal uterine cycle, preventing implantation of an embryo Estimated to be 80% effective Side effects Nausea Vomiting Abdominal pain Fatigue Headache Mifepristone (RU-486) Causes loss of an implanted embryo 95% effective in terminating an early pregnancy Abstinence Most reliable method of birth control Also prevents transmission of STDs

41 Control of Reproduction and STDs
Infertility Failure to achieve pregnancy after one year of regular, unprotected intercourse 15% of all couples are infertile 40% attributed to the male 40% attributed to the female 20% attributed to both

42 Control of Reproduction and STDs
Causes Low sperm count and/or a large proportion of abnormal sperm Herbicides and pesticides Smoking, alcohol, and/or drug abuse Exposing the testicles to overheating Females Body weight is the most significant factor Blocked uterine tubes due to pelvic inflammatory disease and endometriosis Assisted Reproductive Technologies Artificial insemination In vitro fertilization Intracytoplasmic sperm injection

43 Control of Reproduction and STDs
Sexually Transmitted Diseases Caused by a variety of organisms Humans cannot develop effective immunity to any STDs Any person exposed to an STD should seek medical treatment immediately A latex or polyurethane condom should be used to prevent the spread of STDs Treatment of viral STDs will not eliminate them from the body Only bacterial STDs are curable with antibiotics

44 Control of Reproduction and STDs
Genital warts Caused by the human papillomaviruses (HPVs) New vaccine has been released for the HPV that most commonly causes genital warts Genital warts are associated with cancer of the cervix Genital herpes Caused by the herpes simplex virus Type 1 usually causes cold sores and fever blisters Type 2 causes genital herpes

45 Control of Reproduction and STDs
Hepatitis Infects the liver and can lead to liver failure, liver cancer, and death Six known viruses that cause hepatitis (designated A-G) Hepatitis A can be sexually transmitted Hepatitis B is spread through sexual contact and blood-borne transmission Hepatitis D and G are sexually transmitted A combined vaccine is available for hepatitis A and B

46 Control of Reproduction and STDs
Chlamydia Caused by bacterium Chlamydia trachomatis Usually mild or asymptomatic Causes cervical ulcerations, which increase the risk of acquiring HIV Pelvic inflammatory disease (PID) may result if proper treatment is not received

47 Control of Reproduction and STDs
Gonorrhea Caused by the bacterium Neisseria gonorrhoeae Latent infection can lead to PID in males and females Gonorrhea proctitis is an infection of the anus Oral/genital contact can lead to infection of the mouth, throat, and tonsils Resistance to antibiotics is becoming more common

48 Control of Reproduction and STDs
Syphilis Caused by bacterium treponema pallidum Penicillin is an effective antibiotic Three stages: Primary stage Secondary stage Tertiary stage Congenital syphilis – caused by syphilitic bacteria crossing the placenta

49 Sex hormone levels decline
Effects of Aging Sex hormone levels decline Menopause usually occurs between the ages of 45 and 55 In men, testosterone production diminishes steadily after age 50 May be the cause of enlargement of the prostate Sperm production declines, but men can remain fertile well into old age Chances of erectile dysfunction increases

50 Homeostasis Estrogen promotes fat deposition Estrogen Androgens Energy
Insulation Estrogen Induces the liver to produce proteins Induces synthesis of bone matrix proteins Androgens Stimulate synthesis of structural proteins in skeletal muscles and bone Affect the activity of various enzymes in the liver and kidneys

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