Copyright © 2016 by Elsevier Inc. All rights reserved. Reproductive Systems Chapter 21 Copyright © 2016 by Elsevier Inc. All rights reserved.

Learning Objectives Lesson 21.1: Reproductive Systems List the essential and accessory organs of the male and female reproductive systems and give the general function of each. Describe the gross and microscopic structure of the gonads in both sexes and explain the developmental steps in spermatogenesis and oogenesis. Discuss the primary functions of the sex hormones and identify the cell type or structure responsible for their secretion. Copyright © 2016 by Elsevier Inc. All rights reserved.

Learning Objectives Lesson 21.1. Reproductive Systems (Cont.) Identify and describe the structures that constitute the external genitals in both sexes. Identify and discuss the phases of the endometrial or menstrual cycle and correlate each phase with its occurrence in a typical 28-day cycle. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Sexual Reproduction Producing offspring Sexual reproduction requires two parent organisms, a male and a female Advantage: New mixture of genes in each offspring increases the variety of genetic characteristics in the population Reproductive system of each parent produces the sex or reproductive cells (called gametes) Ovum (female); sperm (male) Asexual reproduction requires only one parent Sexual maturity and the ability to reproduce occur at puberty In sexual reproduction, each of the female and the male contribute half of the nuclear chromosomes needed to form the first cell of an offspring organism. In asexual reproduction, one parent produces an offspring genetically identical to itself. Copyright © 2016 by Elsevier Inc. All rights reserved.

Sexual Reproduction (Cont.) Male and female systems Common general structure and function can be identified between the systems in both sexes Systems adapted for development of sperm or ova followed by successful fertilization, development, and birth of offspring Sex hormones in both genders is important in development of secondary sexual characteristics and normal reproductive system activity The production of sex hormones is required not only for development of the secondary sexual characteristics but also for the normal reproductive functions in both sexes. Copyright © 2016 by Elsevier Inc. All rights reserved.

Male Reproductive System Structural plan Essential organs of reproduction Gonads (testes), which produce sex cells (sperm or spermatozoa) Accessory organs of reproduction Ducts Passageways that carry sperm from testes to exterior Sex glands Produce protective and nutrient solution for sperm External genitals The urethra has a dual function. It serves as a passageway for both urine and semen from the body. Copyright © 2016 by Elsevier Inc. All rights reserved.

Organization of the Male Reproductive Organs Figure 21-1 shows the organization of the male reproductive organs. Copyright © 2016 by Elsevier Inc. All rights reserved.

Male Reproductive System (Cont.) Testes: Gonads of men Structure and location Testes in scrotum Lower temperature Covered by tunica albuginea, which divides testis into lobules containing seminiferous tubules Interstitial cells produce testosterone The tunica albuginea is tough and whitish. Copyright © 2016 by Elsevier Inc. All rights reserved.

Tubules of the Testis and Epididymis Figure 21-2: The ducts and tubules are exaggerated in size. In the photograph (left), the testicle is the darker sphere in the center. Lennart Nilsson, Albert Bonnier Forlag A, Stockholm, Sweden. Copyright © 2016 by Elsevier Inc. All rights reserved.

Male Reproductive System (Cont.) Testes Testis functions Spermatogenesis: Process of sperm production Sperm precursor cells called spermatogonia Meiosis produces primary spermatocyte, which forms four spermatids with 23 chromosomes Spermatozoa: Highly specialized cells Head contains genetic material Acrosome contains enzymes to assist sperm in penetration of ovum Mitochondria in midpiece provide energy for movement From puberty on, the seminiferous tubules continuously form spermatozoa (sperm). Most men continue to produce significant numbers throughout life, although the number of sperm diminishes with increasing age. Copyright © 2016 by Elsevier Inc. All rights reserved.

Male Reproductive System (Cont.) Testes Testis functions Production of testosterone by interstitial cells Testosterone “masculinizes” and promotes development of male accessory organs Promotes and maintains development of male accessory organs Stimulates protein anabolism and development of muscle strength Testosterone is an anabolic steroid hormone. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Spermatogenesis Figure 21-4 shows spermatogenesis. A, Cross section of seminiferous tubule shows layers of cells undergoing the process of spermatogenesis. B, Steps of spermatogenesis. Copyright © 2016 by Elsevier Inc. All rights reserved.

Male Reproductive System (Cont.) Reproductive ducts: Ducts through which sperm pass after exiting testes until they exit from the body Epididymis: Single, coiled tube about 6 m in length; lies along the top and behind the testis in the scrotum Sperm mature and develop the capacity for motility as they pass through epididymis Sperm are formed within the walls of the seminiferous tubules of the testes. Copyright © 2016 by Elsevier Inc. All rights reserved.

Male Reproductive System (Cont.) Reproductive ducts Vas deferens (ductus deferens) Receives sperm from the epididymis and transports them from scrotal sac through the abdominal cavity Passes through inguinal canal Joins duct of seminal vesicle to form the ejaculatory duct Ejaculatory duct and urethra Vas deferens joins the duct from the seminal vesicle to form the ejaculatory duct Each vas deferens is thick, smooth, and very muscular. The ejaculatory duct permits sperm to empty into the urethra. Copyright © 2016 by Elsevier Inc. All rights reserved.

Male Reproductive System (Cont.) Accessory glands Semen Mixture of sperm and secretions of accessory sex glands; averages 3 to 5 mL per ejaculation, with each milliliter containing about 100 million sperm Seminal vesicles Pouchlike glands that produce about 60% of seminal fluid volume Secretion is yellowish, thick, and rich in fructose to provide energy needed by sperm for motility Semen protects sperm from the acidic environment of the female reproductive tract. Copyright © 2016 by Elsevier Inc. All rights reserved.

Male Reproductive System (Cont.) Accessory glands Prostate gland Shaped like a doughnut and located below bladder Urethra passes through the gland Secretion represents 30% of seminal fluid volume; thin and milk-colored Activates sperm and is needed for ongoing sperm motility Bulbourethral (Cowper) glands Resemble peas in size and shape Secrete mucus-like fluid constituting less than 5% of seminal fluid volume The mucuslike secretions of the bulbourethral glands neutralize any residue of sperm-damaging acidic urine in urethra. They also lubricate the urethra to protect sperm from friction damage, and they add to the external lubrication of the penis needed for intercourse. Copyright © 2016 by Elsevier Inc. All rights reserved.

Male Reproductive System (Cont.) External genitals Penis and scrotum called genitalia Penis has three columns of erectile tissue Two dorsal columns called corpora cavernosa One ventral column surrounding urethra called corpus spongiosum Glans penis covered by foreskin (prepuce) Surgical removal of foreskin called circumcision Most circumcisions are elective and performed at the discretion of the parents. The scrotum is internally divided into two sacs by a septum. Copyright © 2016 by Elsevier Inc. All rights reserved.

Female Reproductive System Structural plan: Organs classified as essential or accessory Essential organs: Gonads (ovaries), which produce sex cells (ova) Accessory organs Ducts or modified ducts Including oviducts, uterus, and vagina Sex glands Including the breasts External genitals The ovaries produce estrogen and progesterone. Copyright © 2016 by Elsevier Inc. All rights reserved.

Organization of the Female Reproductive System Figure 21-8 shows the organization of the female reproductive system. Copyright © 2016 by Elsevier Inc. All rights reserved.

Female Reproductive System (Cont.) Ovaries Structure and location Paired glands weighing about 3 g each Resemble large almonds Attached to ligaments in pelvic cavity on each side of uterus Microscopic structure Ovarian follicles contain an oocyte, which is an immature sex cell (about 1 million at birth) Primary follicles, about 400,000 at puberty, are covered with granulosa cells About 350 to 500 mature follicles (often called graafian follicles) ovulate during the reproductive lifetime of most women Secondary follicles have a hollow chamber called the antrum Corpus luteum forms after ovulation The mature ovarian follicle is often called a graafian follicle in honor of the Dutch anatomist Regnier de Graaf who discovered it some 300 years ago. Corpus luteum is a Latin phrase meaning “yellow body” – an appropriate name to describe the yellow appearance of this glandular structure. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Ovary Figure 21-9 shows a cross section of an ovary that depicts successive stages of ovarian follicle development. Copyright © 2016 by Elsevier Inc. All rights reserved.

Female Reproductive System (Cont.) Ovaries Ovary functions Oogenesis This meiotic cell division produces daughter cells with equal chromosome numbers (23) but unequal cytoplasm; ovum is large; polar bodies are small and degenerate Production of estrogen and progesterone Granulosa cells surrounding the oocyte in the mature and growing follicles produce estrogen Corpus luteum produces progesterone Estrogen causes development and maintenance of secondary sex characteristics Progesterone stimulates secretory activity of uterine epithelium and assists estrogen in initiating menses Progesterone is produced by the corpus luteum, usually for about 11 days after ovulation. Copyright © 2016 by Elsevier Inc. All rights reserved.

Female Reproductive System (Cont.) Reproductive ducts Uterine (fallopian) tubes (oviducts) Extend about 10 cm from uterus into abdominal cavity Expanded distal end surrounded by fimbriae Mucosal lining of tube is directly continuous with lining of abdominal cavity Uterus Composed of body, fundus, and cervix Lies in pelvic cavity just behind urinary bladder Myometrium is muscle layer Endometrium lost in menstruation Menopause: End of repetitive menstrual cycles (about 45 to 50 years of age) Each uterine tube is about 10 cm in length. Infections of the vagina or uterus such as gonorrhea may pass into the abdominal cavity via the uterine tube, where they may become life-threatening. The changes in the uterine lining repeat themselves and are spoken of as the menstrual cycle. Copyright © 2016 by Elsevier Inc. All rights reserved.

Female Reproductive System (Cont.) Reproductive ducts Vagina Distensible tube about 10 cm long Located between urinary bladder and rectum in the pelvis Receives penis during sexual intercourse and is birth canal for normal delivery of baby at end of term of pregnancy The vagina is an accessory or supportive sex gland. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Uterus Figure 21-11 shows a sectioned view of the uterus, which shows the muscle layers of the uterus and its relationship to the ovaries and vagina. Copyright © 2016 by Elsevier Inc. All rights reserved.

Female Reproductive System (Cont.) Accessory glands Vestibular glands Secrete mucus lubricating fluid Ducts open between labia minora Breasts Located over pectoral muscles of thorax Size determined by fat quantity more than amount of glandular (milk-secreting) tissue Lactiferous ducts drain at nipple, which is surrounded by pigmented areola Lymphatic drainage important in spread of cancer cells to other body areas The greater vestibular glands are also called Bartholin glands and the lesser vestibular glands may be called Skene glands or female prostate. Mucus from vestibular glands may contribute to lubrication during sexual intercourse. Copyright © 2016 by Elsevier Inc. All rights reserved.

Lateral View of the Breast Figure 21-12 shows a lateral view of the breast. The inset shows one of the milk-producing alveoli of the mammary gland. Copyright © 2016 by Elsevier Inc. All rights reserved.

Female Reproductive System (Cont.) External genitals Vulva: Several structures, which includes mons pubis, clitoris, external urinary meatus, labia minora, hymen, openings of vestibular gland ducts, orifice (opening) of vagina, and labia majora Perineum Area between vaginal opening and anus Surgical cut during childbirth called episiotomy The space between the labia minora is the vestibule. Situated between the glans clitoris and the vaginal opening is the external urethral meatus. Copyright © 2016 by Elsevier Inc. All rights reserved.

External Genitals of the Female Figure 21-13 shows the external genitals of the female. Copyright © 2016 by Elsevier Inc. All rights reserved.

Female Reproductive System (Cont.) Menstrual cycle: Involves many changes in the uterus, ovaries, vagina, and breasts Length: About 28 days, varies from month to month among individuals and in the same individual Phases Menses About the first 4 or 5 days of the cycle, varies somewhat; characterized by sloughing of bits of endometrium (uterine lining) with bleeding The first menstrual flow is referred to as the menarche. Copyright © 2016 by Elsevier Inc. All rights reserved.

Female Reproductive System (Cont.) Menstrual cycle Phases Proliferative phase Days between the end of menses and secretory phase; varies in length; the shorter the cycle, the shorter the proliferative phase; the longer the cycle, the longer the proliferative phase Secretory phase Days between ovulation and beginning of next menses; secretory about 14 days before next menses; characterized by further thickening of endometrium and secretion by its glands in preparation for implantation of fertilized ovum; combined actions of the anterior pituitary hormones FSH and LH cause ovulation; sudden sharp decrease in estrogens and progesterone bring on menstruation if pregnancy does not occur The proliferative phase begins after the menstrual flow ends and lasts until ovulation. FSH, Follicle-stimulating hormone. LH, Luteinizing hormone. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. A 28-Day Menstrual Cycle Figure 21-14 shows the phases of a typical 28-day menstrual cycle. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Human Menstrual Cycle Figure 21-15: Diagram illustrates the interrelationship of pituitary, ovarian, and uterine functions throughout a typical 28-day cycle. Copyright © 2016 by Elsevier Inc. All rights reserved.

Female Reproductive System (Cont.) Menstrual cycle Ovulation: Typically occurs 14 days before the next menses begins Timing of ovulation has great practical importance because of the possibility of fertilization Most sperm retain their fertilizing power for only 24 to 72 hours after being deposited into female reproductive tract A woman's fertile period lasts only a few days each month In a typical 28-day cycle, ovulation occurs around day 14. In a 30-day cycle, ovulation occurs around day 16. A woman's fertile period is typically 3 to 5 days before, and no later than 24-hours after, ovulation. Copyright © 2016 by Elsevier Inc. All rights reserved.

Female Reproductive System (Cont.) Menstrual cycle Control of the menstrual cycle Secretion of gonadotropin-releasing hormone (GnRH) stimulates the secretion of FSH and LH from the anterior pituitary gland Ovulation occurs because of the combined actions of the two anterior pituitary hormones Birth control pills that contain estrogen substances suppress FSH secretion With a low level of FSH, no follicles start to grow, and therefore none become ripe enough to ovulate. Copyright © 2016 by Elsevier Inc. All rights reserved.

Summary of the Reproductive Systems Reproductive systems in both sexes revolve around the production of reproductive cells (gametes) Production of sex hormones is required for development of secondary sex characteristics and for normal reproductive functions in both sexes Both men and women have similar structures to accomplish complementary functions Gametes, or reproductive cells, are sperm or ova. The female reproductive system permits development and birth of the offspring. Copyright © 2016 by Elsevier Inc. All rights reserved.

Summary of the Reproductive Systems (Cont.) Table 21-3 shows analogous features of the reproductive systems, both male and female. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Questions? Copyright © 2016 by Elsevier Inc. All rights reserved.