UTS L6.1 Reproductive System PDF

Adolescents have unique reproductive and sexual health needs. Teen sex, sexually transmitted infections, birth control, sexual education, and teen pregnancy are a few of the clinical and social issues. The Reproductive System  The Reproductive System Gonads – primary sex organs...

Adolescents have unique reproductive and sexual health needs. Teen sex, sexually transmitted infections, birth control, sexual education, and teen pregnancy are a few of the clinical and social issues. 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 Consists of: Testes Duct system Epididymis Ductus deferens Urethra  Male Reproductive System Accessory organs Seminal vesicle Prostate gland Bulbourethral gland External genitalia Penis Scrotum  Each lobule contains one to Testes 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  Comma-shaped, tightly coiled tube Epididymis Location: Found on the superior part of the testis and along the posterior lateral side Function To mature and store sperm cells (at least 20 days) Expels sperm with the contraction of muscles in the the epididymis walls to the vas deferens  Ductus Deferens (Vas Deferens) Carries sperm from the epididymis to the ejaculatory duct Passes over the bladder Moves sperm by peristalsis Ends in the ejaculatory duct which unites with the urethra Expanded end is called the ampulla Vasectomy : cutting of the ductus deferens at the level of the testes to prevent transportation of sperm  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 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  Accessory Organs Seminal vesicles Prostate Bulbourethral glands  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 Gland Encircles the upper part of the urethra Secretes a milky fluid Helps to activate sperm Enters the urethra through several small ducts  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 Mixture of sperm and accessory gland secretions of Seminal vesicle Prostate gland Bulbourethral gland Advantages of accessory gland secretions Fructose provides energy for sperm cells Alkalinity of semen helps neutralize the acidic environment of vagina Semen contains seminalplasmin, an antibiotic chemical that inhibits bacterial multiplication Semen releases hormones and enzymes that enhance sperm motility  External Genitalia Scrotum Penis  External Genitalia Scrotum Is a divided sac of skin hangs outside the abdomen between legs and at the root of the penis Maintains testes at 3° C lower than normal body temperature to protect sperm viability  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  Produce sperm And Testosterone hormone Spermatogenesis Production of sperm cells Begins at puberty and continues throughout life Occurs in the seminiferous tubules  Human Life Cycle Union of a sperm (23 chromosomes) with an egg (23 chromosomes) creates a zygote (2n or 46 chromosomes)  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 needed for the movement of tail  Testosterone Production The most important hormone of the testes During puberty, luteinizing hormone (LH) activate the interstitial cells And testosterone is produced in interstitial cells 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 Hormonal Control of the Testis  Female Reproductive System Ovaries Duct System Uterine tubes (fallopian tubes) Uterus Vagina External genitalia  Ovaries Composed of ovarian follicles (sac-like structures) Structure of an ovarian follicle Oocyte (immature egg) Follicular cells —surround the oocyte  Uterine (Fallopian) Tubes Receive the ovulated oocyte Provide a site for fertilization Attaches to the uterus Does not physically attach to the ovary Supported by the broad ligament  Uterine Tube Function 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 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  Regions of the Uterus Body – main portion Fundus – area where uterine tube enters Cervix – narrow outlet that protrudes into the vagina  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 Serous layer – outer visceral peritoneum  Vagina Extends from cervix to exterior of body Behind bladder and in front of rectum Serves as the birth canal Receives the penis during sexual intercourse Hymen – partially closes the vagina until it is ruptured  External Genitalia (Vulva) Mons Pubis Fatty area overlying the pubic symphysis Covered with pubic hair after puberty Labia – skin folds Labia majora— hair-covered skin folds Labia minora— delicate, hair-free folds of skin  External Genitalia Vestibule Enclosed by labia majora Contains external openings of the urethra, followed by vagina Greater vestibular glands One is found on each side of the vagina Secretes lubricant during intercourse Clitoris Contains erectile tissue Corresponds to the male penis  Oogenesis 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 Primary oocytes are inactive until puberty Follicle stimulating hormone (FSH) causes some primary follicles to mature each month Meiosis starts inside maturing follicle Produces a secondary oocyte and the first polar body  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  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  Uterine (Menstrual) Cycle Stages of the menstrual cycle Menstrual phase Proliferative stage Secretory stage  Uterine (Menstrual) Cycle Menstrual phase Days 1–5 Functional layer of the endometrium is sloughed Bleeding occurs for 3–5 days By day 5, growing ovarian follicles are producing more estrogen  Uterine (Menstrual) Cycle Proliferative stage Days 6–14 Regeneration of functional layer of the endometrium Estrogen levels rise Ovulation occurs in the ovary at the end of this stage  Uterine (Menstrual) Cycle Secretory stage Days 15–28 Levels of progesterone rise and increase the blood supply to the endometrium Endometrium increases in size and begin secreting nutrients into the uterine cavity and sustain a developing embryo If fertilization does occur Embryo produces a hormone that causes the corpus luteum to continue producing its hormones If fertilization does NOT occur Corpus luteum degenerates as LH blood levels decline Endometrial cells die Sets the stage for menses again on day 28 Hormonal Control of the Ovarian and Uterine Cycles  Hormone Production by the Ovaries Estrogens Produced by follicle cells Cause secondary sex characteristics Enlargement of accessory organs Development of breasts Appearance of pubic hair Increase in fat beneath the skin Widening and lightening of the pelvis Onset of menses  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 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 Areola – central pigmented area Nipple – protruding central area of areola Lobes – internal structures that radiate around nipple Alveolar glands – clusters of milk producing glands within lobules Lactiferous ducts – connect alveolar glands to nipple  Stages of Pregnancy and Development Fertilization Embryonic development Fetal development Childbirth  Fertilization The oocyte is viable for 12 to 24 hours after ovulation Sperm are viable for 12 to 48 hours after ejaculation Sperm cells must make their way to the uterine tube for fertilization to be possible  Mechanisms of Fertilization Membrane receptors on an oocyte pulls the head of the first sperm cell to make contact The membrane of the oocyte does not permit a second sperm head to enter The oocyte then undergoes its second meiotic division Fertilization occurs when the genetic material of a sperm combines with that of an oocyte to form a 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  The Embryo Developmental stage from the start of cleavage until the ninth week The embryo first undergoes division without growth The embryo enters the uterus at the 16-cell state (called morula) The embryo floats free in the uterus temporarily Uterine secretions are used for nourishment  The Blastocyst Ball-like circle of cells Begins at about the 100 cell stage Secretes human chorionic gonadotropin (hCG) to produce the corpus luteum to continue producing Hormones progesterone and estrogen Functional areas of the blastocyst Trophoblast – large fluid-filled sphere Inner cell mass  The Blastocyst 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 Ectoderm Nervous system Epidermis of the skin Endoderm Mucosae Glands Mesoderm Everything else  Development After Implantation Chorionic villi (projections of the blastocyst) develop Cooperate with cells of the uterus to form the placenta The embryo is surrounded by the amnion (a fluid filled sac) An umbilical cord forms to attach the embryo to 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 producing Estrogen Progesterone Other hormones that maintain pregnancy  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 change in appearance  The Effects of Pregnancy on the Mother Pregnancy – period from conception until birth Anatomical changes Enlargements of the uterus Accentuated lumbar curvature Relaxation of the pelvic ligaments and pubic symphysis due to production of relaxin Effects of Pregnancy on the Mother Physiological changes Gastrointestinal system Morning sickness is common due to elevated progesterone Heartburn is common because of organ crowding by the fetus Constipation is caused by declining motility of the digestive tract Urinary System Kidneys have additional burden and produce more urine The uterus compresses the bladder Effects of Pregnancy on the Mother Respiratory System Nasal mucosa becomes congested and swollen Vital capacity and respiratory rate increase Cardiovascular system Body water rises Blood volume increases by 25 to 40 percent Blood pressure and pulse increase Varicose veins are common  Childbirth (Partition) Labor – the series of events that expel the infant from the uterus Initiation of labor Estrogen levels rise Uterine contractions begin The placenta releases prostaglandins Oxytocin is released by the pituitary Combination of these hormones produces contractions  Stages of Labor Dilation Cervix becomes dilated Uterine contractions begin and increase The amnion ruptures (breaking the water) Expulsion Infant passes through the cervix and vagina Normal delivery is head first Placental stage Delivery of the placenta Stages of Labor Developmental Aspects of the Reproductive System Gender is determined at fertilization Males have XY sex chromosomes Females have XX sex chromosomes Gonads do not begin to form until the eighth week Testosterone determines whether male or female structures will form Developmental Aspects of the Reproductive System Reproductive system organs do not function until puberty Puberty usually begins between ages 10 and 15 Males Enlargement of testes and scrotum signals onset of puberty (often around age 13) Females Budding breasts signal puberty (often around age 11) Developmental Aspects of the Reproductive System The first menses usually occurs about two years after the start of puberty Most women reach peak reproductive ability in their late 20s Menopause occurs when ovulation and menses cease entirely Ovaries stop functioning as endocrine organs There is a no equivalent of menopause in males, but there is a steady decline in testosterone Puberty is the time in which sexual and physical characteristics mature.The exact age a child enters puberty depends on a number of different things, such as genes, nutrition and sex. Most girls and boys enter puberty between 10-16 years of age although some start earlier or later. Girls tend to enter puberty two years before boys.  Changes during Adolescence Physical changes observed in females: Skin becomes oily, sometimes with pimples and acne Hair grows under arms, pubic area, legs Breasts grow Hips broaden, weight and height increase, hands, feet, arms, and legs become larger Perspiration increases and body odor may appear Voice deepens Menstruation begins, more wetness in the vaginal area.  Physical changes observed in males: Skin becomes oily, sometimes with pimples and acne Hair grows under arms, pubic areas, legs, chest, face Muscles especially in legs and arms get bigger and stronger Shoulders and chest broaden, weight and height increase, hands, feet, arms and legs become larger  Perspiration increases and body odor may appear Voice cracks and then deepens Penis and testicles grow and begin to hang down Wet dreams and erection occur frequently Ejaculation occurs during sexual climax. Thank You!