Reproductive System Notes.docx

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Biological Sciences Program
BSCI 201
Justicia Opoku

The Reproductive System The Reproductive System Gonads are the primary sex organs Testes in males Ovaries in females We start of life as bipotential (the ability to form male and/or female genitalia) 1 Gene: SRY Gee determines male or female Default is female Gonads produces gametes (sex cells) and secrete hormones (makes gonads endocrine glands) Sperm are the male gametes Ova( Eggs are the female gametes) Determinants for male or female: If there is a smaller gamete, than it is male. If it is female, it will produce larger gametes. If one starts by creating larger gametes which takes more time, this one will start with the birthing process Sexual reproduction involves the fusion of gametes from two parents resulting in genetic variation among offspring Disadvantage: Takes time to find a mate Also chance of failure May enhance reproductive success in changing environments Allow for variety of phenotypes Both sexes in human Have a set of gonads where gametes are produced Have ducts for delivery of the gonads and structures for copopulation Male Reproductive System Testes Duct System Epididymis Ductus (vas) deferens Urethra Accessory Organ Seminal vesicles Prostate Bulbourethral glands External Genitalia – makes males vulnerable. External Genitalia allows processes to happen at lower temperature Penis Scrotum Testes Covering of the testes TunicaAlbuginea is the capsule that surrounds each testis Septa are the extensions of the capsule that extend into the testis and divide it into lobules Each lobule contains one to four seminiferous tubules Tightly coiled structures Sperm producing factors Empty sperm into 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 as testosterone Females also produce testosterone 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 includes the ductus deferens, blood vessels, and nerves in a connective tissue sheath Ends in the ejaculatory duct which unites with the urethra Expanded end in called the ampulla Ejaculation is the smooth muscle is the walls of the ductus deferens create peristaltic waves to squeeze sperm forward Vasectomy occurs by cutting of the ductus deferens at the level of the testes to prevent transportation. Urethra Extends from the base to the urinary bladder to the tip of the penis Carries both urine and sperm Helps because it saves space Sperm enters from the ejaculatory duct Regions of the urethra Prostatic urethra – surrounded by prostate Membranous urethra – from prostatic urethra to penis Spongy (penile) urethra – run the length of the penis Accessory Organs help produce Semen Semen is a mixture of sperm and accessory gland secretions from: Seminal vesicles Prostate Bulbourethral glands Seminal vesicles Located at the base of the bladder Produces a thick, alkaline yellowish secretion (60% of semen) Fructose (sugar) Vitamin C, a potent antioxidant Prevent free radicals Antioxidant undoes the processes of free radicals Protects semen from mutation Prostaglandins promote smooth muscle contraction Might cause worse environment Other substances that nourish and activate sperm Prostate Encircles the upper part of the urethra Secretes milky fluid Help to activate Semen Fluid enters the urethra through several small ducts Bulbourethral Glands Pea-sized gland inferior to the prostate Produces a thick, clear mucus known as pre-ejaculate Cleanses the urethra of acidic urine Serves as a lubricant during sexual intercourse Secreted into the penile urethra External Genitalia Scrotum Divided sac of skin outside the abdomen Maintains testes at ~3 degrees celcius lower than normal body temperature to protext sperm viability. 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 that may be removed by circumcision Descending Testes Aboys’s testes normally develop in the abrdomen Before birth at round 32-36 weeks, they normally descend through a flexiblte tube, called the inguinal canal, and end up in the scrotum Undescended testes can occur in premature boys and may be corrected with surger. External Genitalia Internally there are three areas of spongy erectile tissue around the urethra Erections occurs when the erectile tissue fills with blood during sexual excitement Spermatogenesis Production of sperm cells Begins at puberty and continues throughout life. Occurs in the seminiferous tubules Spermatogonia (stem cells) undergo rapid mitosis to produce more stem cells before puberty Disadvantage: we need another set of chromosomes for a birth because we give half and the mate gives the other half. Follicle-stimulating hormone (FSH) modulates spermatogonia division One cell produced is a steam cell, called a typeAdaughter cell The other cell produced becomes a primary spermatocyte, called a type B daughter cell. Spermatogenesis Primary Spermatocytes undergo meiosis One primary spermatocyte produces four haploids spermatids Spermatids have 23 chromosomes (half as much material as other body cells) Late spermatids are produced with distinct regions: Head, midpiece, tail Tail Sperm cells result in maturing of spermatids Spermatogenesis ( Entire process, including spermatogenesis, the final stages) Takes 65-75 days. Males are at any given phase at all time. It takes 65 days but every single one is one day apart. Anatomy of the mature Sperm Cells The only flagellated cell Head Contains DNA Acrosome is a “helmet” protecting the nucleus, similar to a large lysosome which breaks down and releases enzymes to help the sperm penetrate an egg Midpiece wrapped by mitochondria forATP generation Tail allows for motion, contains mitochondrion. Testosterone Production The more important hormones of tests Produced by interstitial cells During puberty, luteinizing hormone (LH) activates the interstitial cells In turn, testosterone is produced Function of testosterone Stimulates reproducing organ development Underlies sex drive Causes secondary sex characteristics Deepening of voice Increased hair growth Enlargement of skeletal muscles Thickening of bones If taking Anabolic Steroids Contains testosterone This tells your pituitary gland to stop making your own testosterone so the gonads shrink and stop making hormones. Testes will shrink. Your muscle growth outpaces bone growth so bone breakages occur often Female Reproductive System: Awoman’s ovaries contain follicles in the ovaries that nurture eggs and produce sex hormones Oviduct (Fallopian tubes convey eggs to the uterus) The uterus opens into vagina which receives the penis during intercourse and forms the birth canal Orgasms Makes sex pleasurable so that the biological standard (having the most children) can be reached Wave of Contraction: Propel sperm in the proper direction Role of female duct work is to accept gametes and nurture a child. Males: Donators. Females:Acceptors Viral Infections – linked to cancer. Viruses are linked to uncontrolled cell growth which leads to cancer Vaccinations are the best way to prevent viruses Fertilization takes place in oviduct Ovaries: Each follicle consist of Oocyte (immature egg) Follicular cells surround the oocyte. Day 1: Follicle: Cells that surround the egg. Follicle Stimulating Hormone: Picks an egg at random from FSH If 2 eggs are selected, they wil be known as fraternal twins Cells around the egg will grow and secrete hormones. More Cells: More hormones to release This leads to more estrogen to being released. Brain sends luteinizing hormones: Time to ovulate. Some cells stay behind and become the corpus leutuem. These secrete progesterone. They are waiting fertilization and implantation. If there is no fertilized egg: It degeneratus where the letuem degenerates Duct System: Uterine Tubes (Fallopian Tubes) Receive the ovulated oocyte Provide a site for fertilization Attach to the uterus Little or no contact between Ovaries and uterine tubues Supported and enclosed by the broad ligament. Because the ovaries are not connected to the fallopian tubues, fertilized eggs are possible outside of the uterus. Uterus Located between the Urinary Bladder and rectum Hollow Organ Functions of the uterus Recieves a fertilized Egg Retains the fertilized egg Nourishes the fertilized egg Vagina Uterine Tube and Uterus Fimbriae are finger-like projections at the distal end of the uterine tube that receive the oocyte from the ovary Cilia are located inside the uterine tube and slowly move the oocyte towards the uterus (takes 3-4 days) Fertilization Cervix is the narrow outlet that protrudes into the vagina Becomes vasulatized during pregnancy Walls of the Uterus Endometrium: Inner layer Allows for implantation of a fertilized egg Sloughs off if no pregnancy occurs (menses) Endometriosis: Condition in which the tissue that behaves like the cells lining the uterus (endometrium) grow in other areas of the body, causing pain, irregular bleeding, and possible infertility. Changes it’s shape throughout the 28 day cycle Myometrium is the middle layer of smooth muscle Perimetrium (visceral peritoneum) is the outermost serous layer of the uterus. Vagina Extends from cervix to exterior of body Located between bladder and rectum Serves as the birth canal Receives the penis during sexual intercourse The hymen partially closes the vagina until the hymen is ruptured. External Genitalia Mons pubis Fatty area overlying the pubic Symphysis Covered with pubic hair after puberty Labia are skin folds Labia are skin folds Labia majora: Hair-covered skin folds Labia Minora: Delicate, hair-free folds of skin. Clitoris: Contains erectile tissue Corresponds to the male penis The clitoris is similar to the penis that it is hooded by a prepuce, composed of sensitive erectile tissue, becomes swollen with blood during sexual excitement Removed during female circumcisions now called female genital mutilation Urethral orifice and vaginal orifice Great vestibular glands (bartholin’s glands. Perineum Diamond-shaped region between the anterior ends of the labial folds, anus posteriorly, and ischial tuberosity laterally 2 Pound baby: low chance of survival: Not full developed 10 Pound baby (overweight) – you can’t get out which is why it affects infant mortality. Large babies come out from C-section. Oogenesis and the Ovarian Cycle The total supple of eggs are present at birth Ability to release eggs begins at puberty Reproductive ability ends at _______ Oocytes are matured in developing ovarian follicles Oogonia are the female stem cells found in a developing fetus and no longer active by the time of birth Oogonia undergo mitosis to produce primary oocytes Primary oocytes are surrounded by cells that form primary follicles in the ovary. Oogenesis and the Ovarian Cycle Primary oocytes are inactive until puberty Follicle stimulating hormone (FSH) causes some primary follicles to mature each month Cyclic month changes constitute the ovarian cycle Meiosis restarts 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 and zona pellucida. Oogenesis Meiosis is completed after ovulation only if sperm penetrates Ovum is produced Two additional polar bodies may be 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. Polar Bodies: Extra chromosomes that we get rid of. We throw away the chromosomes into the polar bodies Oogenesis: Females only have primary oocytes Have meiosis 1 and forma polar body When Meiosis II of polar Body May or May not occur because no one has actually studied it. No one needs to study because it has no effect on physiology. Spermatogonium vs. Oogonium Men: Have bunches of sperm factories. Factories always active. Not very large. Just DNA. No real stimulus to complete this process. Females: Females only have primary oocytes. One per month: Primary oocyte becomes secondary oocyte. Polar body dumps the left over chromosomes Second polar body forms only if you aren’t fertilized? It disintegrates if there is fertilization Hormones: The ovarian cycle includes changes in the ovary that occur about every 28 days The menstrual/uterine cycle involves changes that occur in the uterus. Spike in Luteinizing hormone means: Women will ovulate Hormone that say we’re waiting for fertilization: Progesterone. Keeps the uterine lining where it is. New lining is formed by sloughing off the old ones. Follicular Phase is similar to the proliferating phase. Luteal Phase: Waits for the fertilized egg. Females have difefering hormones levels while men have a steady level of testosterone. Ovarian Follicle Stages Primary Follicle contains an immature oocyte Graafian (vesicular) follicle is the growing follicle with a maturing oocyte Ovulation occurs when the egg is mature, the follicle ruptures; occurs about every 28 days. The ruptured follicle is transformed into a corpus Luteum. Ovulation Hormonal Events before ovulation They hypothalamus signals the anterior pituitary to secrete FSH and LH FSH triggers thr growth of a follicle AS the follicle grows, it
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