Reproductive System PPT.pptx

THE REPRODUCTIV E SYSTEMS How are the reproductive systems divided? Divided into male and female systems Each reproductive system has… Gonads- primary sex organs responsible for producing gametes and secreting sex hormones (testes & ovaries) Accessory reproductive organsstructures used to transport...

THE REPRODUCTIV E SYSTEMS How are the reproductive systems divided? Divided into male and female systems Each reproductive system has… Gonads- primary sex organs responsible for producing gametes and secreting sex hormones (testes & ovaries) Accessory reproductive organsstructures used to transport and nourish gametes prior to fertilization How do sperm travel through the male reproductive system? Sperm are formed in the testes. Each testis has many tightly coiled seminiferous tubules where sperm are produced. After production, sperm are transported into the rete testis and then to the epididymis. The epididymis is a highly coiled tube (6 m long). The sperm mature during the 20 days it takes to travel through the epididymis before reaching the ductus deferens (vas deferens). Sperm are stored in the enlarged ampulla of the ductus deferens and, when a man is sexually stimulated, are What glands are associated with the male reproductive system? During this journey, sperm also pass 3 accessory glands, which produce secretions that form semen. Semen dilutes the sperm and protects them as they travel. Seminal vesicles: nutrition, mobility through muscular contraction, clotting of ejaculate Prostate gland: thins semen for easier sperm movement & citric acid for energy Bulbourethral glands (Cowper’s glands)alkaline fluids to neutralize the urethra and lubricate the penis Summary The male reproductive system produces sperm, which are transported from the testes through the epididymis and ductus deferens before being ejaculated through the urethra. Sperm are joined by secretions from 3 accessory glands that add fluid to produce semen. What are the external structures of the male reproductive system? Two 1. major external structures: Scrotum- Flap of skin between the legs that contains the testes. The scrotum maintains an ideal temperature for sperm survival, which is 2-3⁰C lower than normal body temperature. Cremaster muscles control how near the testes are to the body based on external temperature. 2. Penis- the structure that delivers sperm into the female reproductive tract. Composed of… Shaft Glans penis (tip) Erectile tissue- spongy internal tissue that fills with blood during sexual excitement causing an erection During sexual intercourse, the erect penis is inserted into the female vagina and the semen is ejaculated, propelling the sperm into the female reproductive tract. How do sperm develop? Spermatogenesis, the process of sperm production, begins with stem cells called spermatogonia. Diploid spermatogonia divide through meiosis to create 4 spermatids with only 23 chromosomes each (half the number of necessary chromosomes). In a final process called spermiogenesis, the spermatids take the final shape of mature sperm. As the sperm develop, they migrate closer to the lumen of the seminifero us tubule, where they Sperm Head, cells have 3 main sections: midpiece, tail The head contains the nucleus and has an acrosome on the front portion, which contains enzymes to break into the egg cell during fertilization. The midpiece is surrounded by mitochondria, giving the sperm ample energy to swim. The tail (flagellum) provides the movement. Summary Sperm are produced through spermatogenesis, in which one spermatogonium divides to create 4 spermatids, which eventually develop into sperm. The scrotum keeps the sperm at the ideal temperature while the penis delivers them into the female reproductive tract. How do eggs travel through the female reproductive system?     The primary reproductive organs of the female reproductive system are the ovaries. The ovaries release egg cells (ova) to be fertilized by sperm. The ovaries contain about 400,000 follicles (clusters of cells surrounding an egg) at a female’s birth. Only about 400 of these follicles will Ova within mature and be releasedthe asovary eggs. This release of a mature egg is known as ovulation. The ovaries release the mature ovum into the finger-like fimbriae that extend from the uterine tubes (Fallopian tubes). The ovum is funneled into the infundibulum before entering the uterine tubes. The ovum is carried through the uterine tubes by cilia towards the uterus. What is the structure of the uterus? The uterus is a hollow, muscular structure that receives and nourishes an egg as it develops into a baby. The uterus has three major portions: the fundus (superior), the body (hollow middle portion), and the cervix (inferior). The 1. thick walls of the uterus have 3 layers: Endometrium- mucosal layer If an egg is fertilized by sperm in the uterine tubes, the developing embryo will implant in this layer. If the egg is unfertilized, the endometrium will slough off (called menstruation). 2. 3. Myometrium- muscular layer responsible for contractions during childbirth Perimetrium- outer uterine wall The vagina is a thin-walled tube located inferior to the cervix. It receives the penis during intercourse and is the passageway for menstruation and delivery of a baby during childbirth. Summary Follicles that mature into eggs are released from the ovaries and travel through the uterine tubes to the uterus. If the egg is fertilized by a sperm cell, it will implant into the endometrium of the uterus. After development, the baby will exit through the vagina. What are the external structures of the female reproductive system? The external female genitalia is also called the vulva. It includes: Mons pubis- fatty area covered with pubic hair Labia majora & labia minora- skin folds which protect the area known as the vestibule The vestibule contains several structures: Clitoris- like the male penis, this swells when sexually stimulated Urethral openingpurely for urine in female anatomy Vaginal opening Vestibular glands- lubricate How do eggs develop? Oogenesis, like spermatogenesis, begins with stem cells (oogonia). Before birth, the oogonia divide and develop into primary oocytes, which are housed in follicles. At puberty, hormones stimulate a small number of follicles to mature and make the first meiotic division. This division is unequal- a large secondary oocyte and a tiny polar body are produced. The polar body, along with its chromosomes, degenerates. One follicle will release the secondary oocyte (called ovulation). If the secondary oocyte is fertilized, the second meiotic division will occur. This produces another polar body and reduces the female chromosome number to 23. The male and female nuclei join to form a zygote with 46 chromosomes. After ovulation, the follicle degenerates into the corpus luteum. Summary The vaginal opening and urethra are found within the vestibule of the female genitalia. Within the ovaries, hormones causes the maturation of follicles and eventual release of a secondary oocyte during ovulation. How do hormones affect the male reproductive system? The male reproductive system is dependent on 3 hormones: Testosterone- produced in the interstitial cells of the testes; responsible for maturation of reproductive organs & secondary sex characteristics Luteinizing hormone (LH)produced in anterior pituitary; stimulates release of testosterone Follicle-stimulating hormone (FSH)- produced in anterior pituitary; Secondary sex characteristics in males include: Increased muscle mass & strength Increased bone mass Facial and pubic hair growth Deepening of voice Increased sex drive How do hormones affect the female reproductive system? Luteinizing hormone (LH) and folliclestimulating hormone (FSH) are also produced in females when stimulated by the anterior pituitary gland. Additionally, estrogens are secreted by the ovaries, causing female secondary sex characteristics. Progesterone is produced by the corpus luteum after ovulation. It helps to maintain the menstrual cycle. Female secondary sex characteristics include: Breast development Pubic hair growth Increased fat deposits on hips and breasts Widening of hips Onset of menstrual cycle Male pelvis Female pelvis What is the anatomy & physiology of mammary glands? Both sexes have mammary glands, but estrogens cause female mammary glands to increase in size during puberty. Within the center of each breast is a darker areola surrounding a nipple. Beneath the skin, 15-25 lobes of alveolar glands are connected by connective tissue and fat. When lactating, the alveolar glands produce milk and Summary Luteinizing hormone and folliclestimulating hormone are produced in the anterior pituitary and affect both males and females. Testosterone (produced in the testes) and estrogens (produced in the ovaries) cause secondary sex characteristics like muscle and bone growth and breast maturation. How do hormones control the uterine cycle? The uterine (or menstrual) cycle involves recurring changes to the endometrium of the uterus due to hormone fluctuations. On average, the cycle is 28 days long with ovulation occurring on day 14. The uterine cycle occurs in 3 stages: Days 1-5: Menstruation Days 6-14: Proliferative phase Days 15-28: Secretory phase The corpus luteum secretes progesteron e, which causes uterine lining to further thicken. Glands within the endometrium secrete nutrients to sustain an embryo. If the egg is unfertilized, estrogen and progesterone Endometrium is shed through the vagina (called a period). The follicles in the ovaries grow and produce estrogens, which cause the endometrial lining to thicken again. One of the Day 14- Ovulation mature follicles LH and FSH levels peak, an releases causing the egg egg. to be released from the ovary into the Summary The hormones estrogen and progesterone control the uterine cycle. Estrogen causes the endometrium to thicken in the proliferative phase, while progesterone secreted from the corpus luteum causes the endometrium to secrete nutrients in the secretory phase. If the ovulated egg is unfertilized, the endometrium will shed during the menstrual phase. HUMAN DEVELOPMENT & BIRTH How does fertilization occur? Due to the viability of the oocyte and spermatozoa, fertilization must occur 2 days before ovulation up to 1 day afterwards. Hundreds of millions of sperm cells are chemically attracted to the oocyte and travel through the uterine tubes until they reach it. Only a few hundred sperm reach the oocyte. When they do, they all swarm around it simultaneously. The acrosome on the tip of the sperm cells release enzymes that break down the protective layer around When one sperm penetrates the oocyte. the barrier, the ovum releases granules that coat the outside of the ovum, preventing other sperm from penetrating. After fertilization, the oocyte nucleus completes the 2nd meiotic division and the chromosomes of the ovum and sperm unite, making a full What are the stages of embryonic development? Two major stages in development occur: Embryonic development: Fertilization – week 8 Fetal development: Week 9 – birth As the embryo moves down the uterine tube, it already begins to divide (known as cleavage). The embryo is made of 16 cells by the time it reaches the uterus. It is now known as a morula. The morula divides further and at 100 cells, it is known as a blastocyst. The blastocyst implants itself into the uterine wall 6-7 days after Summary When one sperm cell penetrates the outer barrier of an oocyte, fertilization occurs. The oocyte goes through one meiotic division, then many mitotic divisions to form a small ball of cells called a morula. After more divisions, the embryo (now called a blastocyst) implants in the uterus. How does the blastocyst develop? During the first two weeks, the blastocyst arranges itself into two layers- an inner cell mass and an outer trophoblast. The trophoblast forms projections (chorionic villi) that embed it into the uterus, eventually becoming the placenta. The inner cell mass is made of embryonic stem cells which differentiate into 3 germ layers: Ectoderm After 8 weeks, the clearly recognizabl e human embryo is called a fetus. What are the stages of labor? After 40 weeks, oxytocin and prostaglandins cause powerful contractions of the uterus through a positive feedback mechanism. Labor follows in 3 stages: Dilation stage: Amniotic sac ruptures (aka. water breaking) and cervix becomes thinner and widens, eventually up to 10 cm. Expulsion stage: Baby is pushed out through the vagina and cervix. Placental stage: Within 15 minutes after the baby is delivered, the uterus contracts again to expel the placenta. Summary The blastocyst differentiates into three germ layers, which will become the body systems for the baby. The embryo grows into a fetus, eventually being expelled through contractions of the uterus.