BIO 094 Chapter 16

The Reproductive System : The Reproductive System

The Reproductive System : The Reproductive System Gonads—primary sex organs Testes in males Ovaries in females Gonads produce gametes (sex cells) and secrete hormones Sperm—male gametes Ova (eggs)—female gametes

Male Reproductive System Overview : Male Reproductive System Overview Testes Duct system Epididymis Ductus (vas) deferens Urethra

Male Reproductive System Overview : Male Reproductive System Overview Accessory organs Seminal vesicles Prostate Bulbourethral glands External genitalia Penis Scrotum

Male Reproductive System : Male Reproductive System Figure 16.2a

Male Reproductive System : Male Reproductive System Figure 16.2b

Testes : Testes Figure 16.1

Testes : Testes Each lobule contains one to four seminiferous tubules Tightly coiled structures Function as sperm-forming factories Empty sperm into the rete testis (first part of the duct system) Sperm travels through the rete testis to the epididymis Interstitial cells in the seminiferous tubules produce androgens such as testosterone

Duct System : Duct System Epididymis Ductus (vas) deferens Urethra

Epididymis : Epididymis Comma-shaped, tightly coiled tube Found on the superior part of the testis and along the posterior lateral side Functions to mature and store sperm cells (at least 20 days) Expels sperm with the contraction of muscles in the epididymis walls to the vas deferens

Epididymis : Epididymis Figure 16.1

Ductus Deferens (Vas Deferens) : Ductus Deferens (Vas Deferens) Carries sperm from the epididymis to the ejaculatory duct Passes through the inguinal canal and over the bladder Moves sperm by peristalsis Spermatic cord—ductus deferens, blood vessels, and nerves in a connective tissue sheath

Ductus Deferens (Vas Deferens) : Ductus Deferens (Vas Deferens) Ends in the ejaculatory duct which unites with the urethra Expanded end is called the ampulla Ejaculation—smooth muscle in the walls of the ductus deferens create peristaltic waves to squeeze sperm forward Vasectomy—cutting of the ductus deferens at the level of the testes to prevent transportation of sperm

Urethra : Urethra Extends from the base of the urinary bladder to the tip of the penis Carries both urine and sperm Sperm enters from the ejaculatory duct

Urethra : Urethra Regions of the urethra Prostatic urethra—surrounded by prostate Membranous urethra—from prostatic urethra to penis Spongy (penile) urethra—runs the length of the penis

Urethra : Urethra Figure 16.2b

Seminal Vesicles : Seminal Vesicles Located at the base of the bladder Produces a thick, yellowish secretion (60% of semen) Fructose (sugar) Vitamin C Prostaglandins Other substances that nourish and activate sperm

Prostate : Prostate Encircles the upper part of the urethra Secretes a milky fluid Helps to activate sperm Enters the urethra through several small ducts

Prostate : Prostate Figure 16.2a

Bulbourethral Glands : Bulbourethral Glands Pea-sized gland inferior to the prostate Produces a thick, clear mucus Cleanses the urethra of acidic urine Serves as a lubricant during sexual intercourse Secreted into the penile urethra

Semen : Semen Mixture of sperm and accessory gland secretions Advantages of accessory gland secretions Fructose provides energy for sperm cells Alkalinity of semen helps neutralize the acidic environment of vagina Semen inhibits bacterial multiplication Elements of semen enhance sperm motility

External Genitalia : External Genitalia Figure 16.2a

External Genitalia : External Genitalia Scrotum Divided sac of skin outside the abdomen Maintains testes at 3°C lower than normal body temperature to protect sperm viability

External Genitalia : External Genitalia Penis Delivers sperm into the female reproductive tract Regions of the penis Shaft Glans penis (enlarged tip) Prepuce (foreskin) Folded cuff of skin around proximal end Often removed by circumcision

External Genitalia : External Genitalia Internally there are three areas of spongy erectile tissue around the urethra Erections occur when this erectile tissue fills with blood during sexual excitement

Spermatogenesis : Spermatogenesis Production of sperm cells Begins at puberty and continues throughout life Occurs in the seminiferous tubules

Spermatogenesis : Spermatogenesis Figure 16.3

Spermatogenesis : Spermatogenesis Figure 16.3 (1 of 2)

Spermatogenesis : Spermatogenesis Figure 16.3 (2 of 2)

Human Life Cycle : Human Life Cycle Union of a sperm (23 chromosomes) with an egg (23 chromosomes) creates a zygote (2n or 46 chromosomes)

Human Life Cycle : Human Life Cycle Figure 16.4

Anatomy of a Mature Sperm Cell : Anatomy of a Mature Sperm Cell The only human flagellated cell Head Contains DNA Acrosome—“helmet” on the nucleus, similar to a large lysosome Breaks down and releases enzymes to help the sperm penetrate an egg Midpiece Wrapped by mitochondria for ATP generation

Structure of a Sperm : Structure of a Sperm Figure 16.5b

Structure of a Sperm : Structure of a Sperm Figure 16.5a

Testosterone Production : Testosterone Production The most important hormone of the testes Produced in interstitial cells During puberty, luteinizing hormone (LH) activate the interstitial cells In turn, testosterone is produced

Testosterone Production : Testosterone Production Functions of testosterone Stimulates reproductive organ development Underlies sex drive Causes secondary sex characteristics Deepening of voice Increased hair growth Enlargement of skeletal muscles Thickening of bones

Female Reproductive System : Female Reproductive System Ovaries Duct System Uterine tubes (fallopian tubes) Uterus Vagina External genitalia

Female Reproductive System : Female Reproductive System Figure 16.8a

Ovaries : Ovaries Composed of ovarian follicles (sac-like structures) Each follicle consists of Oocyte (immature egg) Follicular cells—surround the oocyte

Ovaries : Ovaries Figure 16.7

Ovarian Follicle Stages : Ovarian Follicle Stages Primary follicle—contains an immature oocyte Graafian (vesicular) follicle—growing follicle with a maturing oocyte Ovulation—when the egg is mature, the follicle ruptures; occurs about every 28 days The ruptured follicle is transformed into a corpus luteum

Support for Ovaries : Support for Ovaries Suspensory ligaments—secure ovary to lateral walls of the pelvis Ovarian ligaments—attach to uterus Broad ligament—a fold of the peritoneum, encloses suspensory ligament

Female Reproductive System : Female Reproductive System Figure 16.8b

Uterine (Fallopian) Tubes : Uterine (Fallopian) Tubes Receive the ovulated oocyte Provide a site for fertilization Attach to the uterus Little or no contact between ovaries and uterine tubes Supported and enclosed by the broad ligament

Uterine Tube Anatomy and Physiology : Uterine Tube Anatomy and Physiology Fimbriae Finger-like projections at the distal end of the uterine tube Receive the oocyte from the ovary Cilia Located inside the uterine tube Slowly move the oocyte towards the uterus (takes 3–4 days) Fertilization occurs inside the uterine tube since oocyte lives about 24 hours

Uterus : Uterus Located between the urinary bladder and rectum Hollow organ Functions of the uterus Receives a fertilized egg Retains the fertilized egg Nourishes the fertilized egg

Female Reproductive System : Female Reproductive System Figure 16.8b

Regions of the Uterus : Regions of the Uterus Body—main portion Fundus—superior rounded region above where uterine tube enters Cervix—narrow outlet that protrudes into the vagina

Walls of the Uterus : Walls of the Uterus Endometrium Inner layer Allows for implantation of a fertilized egg Sloughs off if no pregnancy occurs (menses) Myometrium—middle layer of smooth muscle Perimetrium (visceral peritoneum)—outermost serous layer of the uterus

Vagina : Vagina Extends from cervix to exterior of body Located between bladder and rectum Serves as the birth canal Receives the penis during sexual intercourse Hymen—partially closes the vagina until it is ruptured

Female Reproductive System : Female Reproductive System Figure 16.8b

External Genitalia (Vulva) : External Genitalia (Vulva) Mons pubis Labia Clitoris Urethral orifice Vaginal orifice Greater vestibular glands

External Genitalia (Vulva) : Figure 16.9 External Genitalia (Vulva)

Labia : Labia Labia—skin folds Labia majora—hair-covered skin folds Labia minora—delicate, hair-free folds of skin

Vestibule and Greater Vestibular Glands : Vestibule and Greater Vestibular Glands Vestibule Enclosed by labia majora Contains external openings of the urethra, vagina Greater vestibular glands One is found on each side of the vagina Secretes lubricant during intercourse

Clitoris : Clitoris Contains erectile tissue Corresponds to the male penis The clitoris is similar to the penis in that it is Hooded by a prepuce Composed of sensitive erectile tissue Becomes swollen with blood during sexual excitement

Perineum : Perineum Diamond-shaped region between the anterior ends of the labial folds, anus posteriorly, and ischial tuberosities laterally

Perineum : Perineum Figure 16.9

Oogenesis and the Ovarian Cycle : Oogenesis and the Ovarian Cycle The total supply of eggs are present at birth Ability to release eggs begins at puberty Reproductive ability ends at menopause Oocytes are matured in developing ovarian follicles

Oogenesis and the Ovarian Cycle : Oogenesis and the Ovarian Cycle Primary oocytes are inactive until puberty Follicle stimulating hormone (FSH) causes some primary follicles to mature each month Cyclic monthly changes constitute the ovarian cycle

Oogenesis and the Ovarian Cycle : Oogenesis and the Ovarian Cycle Meiosis starts inside maturing follicle Produces a secondary oocyte and the first polar body Follicle development to the stage of a vesicular follicle takes about 14 days Ovulation of a secondary oocyte occurs with the release of luteinizing hormone (LH) Secondary oocyte is released and surrounded by a corona radiata

Ovulation : Ovulation Figure 16.11

Oogenesis and the Ovarian Cycle : Oogenesis and the Ovarian Cycle Meiosis is completed after ovulation only if sperm penetrates Ovum is produced Two additional polar bodies are produced Once ovum is formed, the 23 chromosomes can be combined with those of the sperm to form the fertilized egg (zygote) If the secondary oocyte is not penetrated by a sperm, it dies and does not complete meiosis to form an ovum

Male and Female Differences : Male and Female Differences Meiosis Males—produces four functional sperm Females—produces one functional ovum and three polar bodies Sex cell size and structure Sperm are tiny, motile, and equipped with nutrients in seminal fluid Egg is large, non-motile, and has nutrient reserves to nourish the embryo until implantation

Oogenesis : Oogenesis Figure 16.10

Uterine (Menstrual) Cycle : Uterine (Menstrual) Cycle Cyclic changes of the endometrium Regulated by cyclic production of estrogens and progesterone FSH and LH regulate the production of estrogens and progesterone Both female cycles are about 28 days in length Ovulation typically occurs about midway through cycle on day 14

Ovarian Cycle : Ovarian Cycle Figure 16.12c

Uterine (Menstrual) Cycle : Uterine (Menstrual) Cycle Figure 16.12d

Hormone Production by the Ovaries : Hormone Production by the Ovaries Estrogens Produced by follicle cells Cause secondary sex characteristics Enlargement of accessory organs Development of breasts Appearance of axillary and pubic hair Increase in fat beneath the skin, particularly in hips and breasts Widening and lightening of the pelvis Onset of menses (menstrual cycle)

Hormone Production by the Ovaries : Hormone Production by the Ovaries Progesterone Produced by the corpus luteum Production continues until LH diminishes in the blood Does not contribute to the appearance of secondary sex characteristics Other major effects Helps maintain pregnancy Prepare the breasts for milk production

Mammary Glands : Mammary Glands Present in both sexes, but only function in females Modified sweat glands Function is to produce milk Stimulated by sex hormones (mostly estrogens) to increase in size

Anatomy of Mammary Glands : Anatomy of Mammary Glands Areola—central pigmented area Nipple—protruding central area of areola Lobes—internal structures that radiate around nipple Lobules—located within each lobe and contain clusters of alveolar glands Alveolar glands—produce milk when a woman is lactating (producing milk) Lactiferous ducts—connect alveolar glands to nipple

Female Mammary Glands : Female Mammary Glands Figure 16.13a

Female Mammary Glands : Female Mammary Glands Figure 16.13b

Mammography : Mammography X-ray examination that detects breast cancers too small to feel Recommended every 2 years for women between 40 and 49 years old and yearly thereafter

Mammograms : Mammograms Figure 16.14

Stages of Pregnancy and Development : Stages of Pregnancy and Development Fertilization Embryonic development Fetal development Childbirth

Fertilization : Fertilization The oocyte is viable for 12 to 24 hours after ovulation Sperm are viable for 24 to 48 hours after ejaculation For fertilization to occur, sexual intercourse must occur no more than 2 days before ovulation and no later than 24 hours after Sperm cells must make their way to the uterine tube for fertilization to be possible

Mechanisms of Fertilization : Mechanisms of Fertilization When sperm reach the oocyte, enzymes break down the follicle cells of the corona radiata around the oocyte Once a path is cleared, sperm undergo an acrosomal reaction (acrosomal membranes break down and enzymes digest holes in the oocyte membrane) Membrane receptors on an oocyte pull in the head of the first sperm cell to make contact

Mechanisms of Fertilization : Mechanisms of Fertilization The membrane of the oocyte does not permit a second sperm head to enter The oocyte then undergoes its second meiotic division to form the ovum and a polar body Fertilization occurs when the genetic material of a sperm combines with that of an oocyte to form a zygote

The Zygote : The Zygote First cell of a new individual The result of the fusion of DNA from sperm and egg The zygote begins rapid mitotic cell divisions The zygote stage is in the uterine tube, moving toward the uterus

Cleavage : Cleavage Rapid series of mitotic divisions that begins with the zygote and ends with the blastocyst Zygote begins to divide 24 hours after fertilization Three to 4 days after ovulation, the preembryo reaches the uterus and floats freely for 2–3 days Late blastocyst stage—embryo implants in endometrium (day 7 after ovulation)

Cleavage : Figure 16.15 Cleavage

Developmental Stages : Developmental Stages Embryo—developmental stage until ninth week Morula—16-cell stage Blastocyst—about 100 cells Fetus—beginning in ninth week of development

The Embryo : The Embryo The embryo first undergoes division without growth The embryo enters the uterus at the 16-cell state (called a morula) about 3 days after ovulation The embryo floats free in the uterus temporarily Uterine secretions are used for nourishment

The Blastocyst (Chorionic Vesicle) : The Blastocyst (Chorionic Vesicle) Ball-like circle of cells Begins at about the 100-cell stage Secretes human chorionic gonadotropin (hCG) to induce the corpus luteum to continue producing hormones Functional areas of the blastocyst Trophoblast—large fluid-filled sphere Inner cell mass—cluster of cells to one side

The Blastocyst (Chorionic Vesicle) : The Blastocyst (Chorionic Vesicle) Primary germ layers are eventually formed Ectoderm—outside layer Mesoderm—middle layer Endoderm—inside layer The late blastocyst implants in the wall of the uterus (by day 14)

Derivatives of Germ Layers : Derivatives of Germ Layers Ectoderm Nervous system Epidermis of the skin Endoderm Mucosae Glands Mesoderm Everything else

Development After Implantation : Development After Implantation Chorionic villi (projections of the blastocyst) develop Cooperate with cells of the uterus to form the placenta Amnion—fluid-filled sac that surrounds the embryo Umbilical cord Blood-vessel containing stalk of tissue Attaches the embryo to the placenta

Embryo of Approximately 18 Days : Embryo of Approximately 18 Days Figure 16.16

The 7-week Embryo : The 7-week Embryo Figure 16.17

Functions of the Placenta : Functions of the Placenta Forms a barrier between mother and embryo (blood is not exchanged) Delivers nutrients and oxygen Removes waste from embryonic blood Becomes an endocrine organ (produces hormones) and takes over for the corpus luteum (by end of second month) by producing Estrogen Progesterone Other hormones that maintain pregnancy

The Fetus (Beginning of the Ninth Week) : The Fetus (Beginning of the Ninth Week) All organ systems are formed by the end of the eighth week Activities of the fetus are growth and organ specialization This is a stage of tremendous growth and change in appearance

Photographs of a Developing Fetus : Photographs of a Developing Fetus Figure 16.18a

Development of the Human Fetus : Table 16.1 (1 of 2) Development of the Human Fetus

Development of the Human Fetus : Development of the Human Fetus Table 16.1 (2 of 2)

Flow Chart of Events that Must Occur to Produce a Baby : Flow Chart of Events that Must Occur to Produce a Baby Figure 16.21 (1 of 2)