Lecture 28, The Reproductive System

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1 Fundamentals of Anatomy & Physiology Lecture 28, The Reproductive System SIXTH EDITION Frederic H. Martini Lecturer: Dr. Barjis Room: P313 Phone: (718) Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings

2 Learning Objectives Specify the components of the reproductive system, and summarize their functions Describe the components of the male and female reproductive systems Outline the processes of meiosis and gametogenesis in both sexes Explain the roles played by the male reproductive tract and accessory glands in the functional maturation, nourishment, storage, and transport of spermatozoa

3 Learning Objectives Summarize the anatomical, physiological, and hormonal aspects of the male and female reproductive cycles Discuss the physiology of sexual intercourse

4 Reproductive System The only system not essential for life, but ensures continued human existence Functions of Reproductive system include: Production of gametes Storage gametes Nourishment gametes Transport gametes In female additional functions such as provide nutrient and support to the developing embryo, fetus and infant Fertilization Fusion of male and female gametes to form a zygote

5 Reproductive system includes: Organs of reproductive system include: 1) Gonads (testes, ovaries) produce sperm/egg Testes produce gametes (spermatozoa/ sperm) 1.5 billion each day and secrete sex hormones (testosterone) Ovaries release one immature gamete (oocyte) per month 2) Ducts a passageway that opens to the exterior and transport gamete Sperm is mixed with secretion of accessory glands along ducts and converted to semen Oocyte travels along uterine tube to uterus 3) Accessory glands and organs these organs secrete fluid e.g. seminal vesicle secrete seminal fluid 4) External genitalia

6 Male Reproductive System: Sperm Passageway 1. Spermatozoa is produced in testes in the seminiferous tubules Seminiferous tubules are tightly coiled tubes found in lobules of testes 2. From seminiferous tubules sperms are passed to afferent ductules 3. Afferent ductules pass the sperm to rete stestes 4. From rete testes spearm leave the testes by efferent tuctules 5. Efferent tuctules deliver the sperm to the epididymis

7 The Structure of the Testes

8 Male Reproductive System: Sperm Passageway 6. Epididymis pass the sperms to the duct deference 7. From ductus deferens, sperms are passed to the ejaculatory duct 8. Ejaculatory duct is connected to the urethra Accessory organs of male reproductive system 1. Seminal vesicles 2. Prostate gland 3. Bulbourethral glands 4. Scrotal sac encloses testes 5. Penis

9 The Male Reproductive System

10 Sperm production: Spermatogenesis Sperm production takes place in seminiferous tubules Seminiferous tubules contain sustencular cells and stem cells called spermatogonia Stem cells involved in spermatogenesis Sustencular cells sustain and promote development of sperm Interstitial cells between seminiferous tubules secrete sex hormones (testosterone)

11 Sperm production: Spermatogenesis Spermatogenesis involves three processes 1) Mitosis In this process spermatocytes are produced from spermatogonium 2) Meiosis In this process spermatocytes go through meiosis I and meiosis II and produce 4 spermatids 3) Spermiogenesis In this process spermatids differentiate into spermatozoa

12 Sperm production: Spermatogenesis Figure 28.7

13 Sperm production: Spermatogenesis

14 Sperm production: Spermatogenesis

15 Sperm production: Spermatogenesis

16 Sperm production: Spermatogenesis

17 Sperm production: Spermatogenesis

The testes Descent of the testes Movement of testes through inguinal canal into scrotum Occurs during fetal development Testes anatomy Tunica albuginea surrounds testis Septa

18 The testes Descent of the testes Movement of testes through inguinal canal into scrotum Occurs during fetal development Testes anatomy Tunica albuginea surrounds testis Septa extend from tunica albuginea and divides testes into lobules Within each lobule tightly coiled tubes called seminiferous are located Sperm production occurs in seminiferous tubules

19 The Descent of the Testes

20 Anatomy of spermatozoon Each spermatozoon is divided into 3 part: 1) Head that contains: Nucleus and densely packed chromosomes 2) Middle piece that contains Mitochondria that produce the ATP needed to move the tail 3) Tail The only cell with flagellum in the human body It enables the spermatozoa to swim

21 Spermiogenesis and Spermatozoon Structure

22 Male reproductive tract: Epididymus Epididymus is elongated tubule with head, body and tail regions Functions of epididymus are to: 1) Monitor and adjust fluid in seminiferous tubules 2) Store and protect spermatozoa 3) act as a recycling center for damaged spermatozoa 4) Facilitates functional maturation of spermatozoa Although spermatozoa leaving the epididymis are mature, but they remain immobile. Spermatozoa will become functionally mature when: 1) mixed with secretions of the seminal vesicles,(become mobile 2) exposed to conditions in the female reproductive tract(become capable of fertilization)

23 The Epididymus

24 Ductus deferens AKA vas deferens Begins at epididymus Passes through inguinal canal Enlarges to form ampulla Peristaltic contractions propel spermatozoa and fluid along the duct Functions of Duct Deferens: Transport spermatozoa, Store spermatozoa (for several months) The junction of the ampulla with the duct of the seminal vesicle marks the start of the ejaculatory duct Ejaculatory duct is a short passageway that penetrates the muscular wall of the prostate gland and empties into the urethra

25 Urethra This passageway is used by both urinary and reproductive systems This passageway begins at the urinary bladder and ends at the tip of the penis Urethra divides into three regions Prostatic Membranous Penile

26 Accessory glands Important glands include the seminal vesicles, the prostate gland, and the bulbourethral glands Seminal vesicles Contributes about 60% of the total volume of semen Secretions of seminal vesicle contain fructose, prostaglandins, fibrinogen Fructose is metabolized by spermatozoa and used as a source of energy Prostaglandins stimulates smooth muscle contractions along the reproductive tracts (e.g. vagina), thus it helps spermatozoa to move Fibrinogen forms a temporary clot within the vagina to prevent damage to the spermatozoa by the acidic environment of vagina. Spermatozoa become mobile after mixing with seminal vesicles secretion

27 Accessory glands Prostate gland Secretes an alkaline prostatic fluid that accounts for about % of semen volume Contains seminalplasmin (an antibiotic that prevents urinary tract infection) The alkaline secretion helps to neutralizes acid along the urethra and in the vagina Bulbourethral glands Secrete alkaline mucus with lubricating properties

28 The Ductus Deferens and Accessory Glands

29 Contents of Semen Typical ejaculate = 2-5 ml fluid that contain: 1) Contains between million spermatozoa per ml 2) Seminal Fluid about 60% 3) Prostatic Fluid about % 4) Enzymes such as: Protease helps dissolve mucous secretion in the vagina Seminalplasmin antibiotic enzyme that kills bacteria Enzymes that convert fibrinogen to fibrin that will clot the semen Fibrinolysis liquefies the clotted semen after the virginal environment is neutralized

30 External genitalia Male external genitalia consist of the scrotum and the penis Skin overlying penis resembles scrotum Penis Contains three masses of erectile tissue 2 corpora cavernosa beneath fascia 1 corpus spongiosum surrounding urethra Dilation of erectile tissue produces erection

31 The Penis

32 Hormones of male and female reproductive system At puberty Hypothalamus produces GnRH (Gonadotropin releasing hormone) GnRH stimulates production of FHS and LH by the pituitary gland FSH (Follicle stimulating hormone) In male FSH targets sustentacular cells of testes and stimulates spermatogenesis (production of sperm) In female FSH stimulates development of follicle (egg) Developing follicle produces estrogen LH (leutinizing hormone) In male LH causes secretion of testosterone and other androgens by the interstitial cells In female LH stimulates secretion of progesterone by corpus luteum In female LH surge leads to ovulation

33 Hormones of male and female reproductive system Testosterone 1) stimulating spermatogenesis 2) affect sexual drive(libido) 3) stimulate metabolism 4) stimulate the male secondary sexual characteristics 5) maintaining accessory glands and organs of male reproductive tract Progesterone Stimulate endometrial growth and secretion Estrogen 1) stimulating bone and muscle growth 2) stimulate female secondary sexual characteristics 3) initiating the repair and growth of the endometrium

34 Hormonal Feedback and the Regulation of the Male Reproductive Function

35 The Hormonal Regulation of Ovarian Activity

36 The Reproductive System of the Female Principle organs of the female reproductive system Ovaries Uterine tubes Uterus Vagina

37 The Female Reproductive System

38 The ovaries Held in position by ovarian and suspensory ligaments Blood vessels enter at ovarian hilus Tunica albuginea covers ovary

39 The Ovaries and Their Relationships to the Uterine Tube and Uterus

40 Oogenesis Oogenesis is the process of ovum production It occurs monthly in ovarian follicles Part of ovarian cycle Follicular phase (preovulatory) Luteal phase (postovulatory)

41 The ovarian cycle Steps in the ovarian cycle 1) Formation of primary, secondary, and tertiary follicles 2) Ovulation 3) Formation and degeneration of the corpus luteum Corpus luteum begins to degenerate roughly 12 days after ovulation if fertilization does not occur 4) Degradation of the corpus luteum

42 The Ovarian Cycle

43 The Ovarian Cycle

44 The Uterine tubes Uterine tubes (Fallopian tubes or oviducts) is divided into: 1) Infundibulum End of infundibulum closest to the ovary has numerous fingerlike projections called fimbriae 2) Ampulla The middle portion 3) Isthmus A short segment connected to the uterine wall Each uterine tube opens directly into uterine cavity Fertilization occurs in uterine tube hours after ovulation

45 The Uterine Tubes

46 The uterus The uterus is a muscular organ Its functions are: 1) Mechanical protection 2) Nutritional support 3) Waste removal for the developing embryo and fetus Major anatomical landmarks of uterus Body Isthmus Cervix Cervical os (internal orifice) Uterine cavity Cervical canal Internal os (internal orifice)

47 The Uterine Wall Uterine wall consists of 3 layer: Myometrium outer muscular layer Endometrium a thin, inner, glandular mucosa Perimetrium an incomplete serosa continuous with the peritoneum

48 Uterine cycle Repeating series of changes in the endometrium Uterine cycle continues from menarche (the first minstruation) to menopause (the last minstruation) Uterine cycle is divided into 3 phases: 1) Menses Degeneration of the endometrium Menstruation 2) Proliferative phase Restoration of the endometrium 3) Secretory phase Endometrial glands enlarge and accelerate their rates of secretion

49 The Uterine Cycle

50 The vagina Vagina is an elastic, muscular tube Major functions of vagina are: 1) Passageway for elimination of menstrual fluids 2) Receives the penis during sexual intercourse Also hold spermatozoa prior to their passageway into the uterus 3) Forms the inferior portion of the birth canal

51 External genitalia Vulva Vestibule Labia minora Labia majora Paraurethral glands Clitoris Lesser and greater vestibular glands

52 The Female External Genitalia

53 Hormones of the female reproductive cycle Control the reproductive cycle Coordinate the ovarian and uterine cycles

54 The Hormonal Regulation of the Female Reproductive Cycle

55 The Hormonal Regulation of the Female Reproductive Cycle Animation: Regulation of the Female Reproductive Cycle (see tutorial)

56 The Physiology of Sexual Intercourse: Male sexual function Arousal Leads to erection of the penis Parasympathetic outflow over the pelvic nerves Emission and ejaculation Occur under sympathetic stimulation Results in semen being pushed toward external urethral opening Detumescence Subsidence of erection Mediated by the sympathetic nervous system

57 Female sexual function Stages are comparable to those of male sexual function Arousal causes clitoral erection Vaginal surfaces are moistened Parasympathetic stimulation causes engorgement of blood vessels in the nipples

58 Aging and the Reproductive System Menopause The time that ovulation and menstruation cease Typically around age Accompanied by a decline in circulating estrogen and progesterone Rise in GnRH, FSH, LH

59 Male climacteric Levels of circulating testosterone begin to decline FSH and LH levels rise Gradual reduction in sexual activity

60 You should now be familiar with: The components of the reproductive system, and their functions The components of the male and female reproductive systems The processes of meiosis and gametogenesis in both sexes

61 You should now be familiar with: The roles played by the male reproductive tract and accessory glands in the functional maturation, nourishment, storage, and transport of spermatozoa The anatomical, physiological, and hormonal aspects of the male and female reproductive cycles The physiology of sexual intercourse

The Reproductive System

Essentials of Anatomy & Physiology, 4th Edition Martini / Bartholomew The Reproductive System PowerPoint Lecture Outlines prepared by Alan Magid, Duke University Slides 1 to 84 Overview of Reproduction