Behavioural Biology Lecture 11: The Reproductive System PDF

Behavioural Biology Lecture 11 The Reproductive System Lecture Objectives  Anatomy of the male and female reproductive systems.  Functions of the components of the reproductive systems.  Introduction to hormone regulation of reproductive function. Textbook Chapter 17 Functions of the...

Behavioural Biology Lecture 11 The Reproductive System Lecture Objectives  Anatomy of the male and female reproductive systems.  Functions of the components of the reproductive systems.  Introduction to hormone regulation of reproductive function. Textbook Chapter 17 Functions of the Reproductive System: 1. Produce gametes (sperm and eggs) 2. Bring gametes together where they may fuse (fertilization), producing a single cell (zygote) from which all cells are derived from to form a new individual. 3. Nurture the development of the zygote into an embryo then fetus as well as nurture the baby postpartum through the production of milk. Primary Sex Organs: The Gonads The gonads are the testes in males and the ovaries in females. The gonads produce 2 essential products: 1. Gametes (sperm & egg) made through a specialized cell division process called Meiosis Sperm are made in the testes Eggs are made in the ovaries 2. Sex hormones Testosterone (males) Estrogen (females) Progesterone (females) The activity of the gonads is ultimately regulated by the hypothalamus. Recall: The Hypothalamus, Pituitary, Gonad (HPG) Axis Gonadotropin releasing hormone (GnRH) from the hypothalamus stimulates the anterior pituitary to release luteinizing hormone (LH) and follicle stimulating hormone (FSH) which both affect the activity (gamete & sex hormone production) occurring within the gonads. Male Reproductive Strategy Produce millions of sperm cells and deliver them to the female reproductive system. A sperm cell requires a lot less energy to produce than an egg cell so males can produce many! Male Reproductive System 1. Organs Testes within the scrotum Penis 2. Ducts Epididymis Ductus deferens Ejaculatory duct Urethra 3. Accessory Glands Seminal glands (2) Prostate (1) Bulbo-urethral glands (2) Male Reproductive System Scrotum contains the testes Both testes and their associated epididymis and initial section of ductus deferens are contained within a sac of skin located outside of the pelvic cavity called the scrotum. Why are testes in such a vulnerable location? Optimal temperature for producing viable sperm is lower than internal body temperature. Position of the scrotum and its surface area can be altered through the contraction of muscles which raise or lower the testes as well as wrinkle or relax its surface in response to temperature change. Spermatogenesis Immature sperm cells are created in the testes by a specialized cell division process called meiosis starting at puberty. (about 100 million per day!) Testis to Epididymis Immature sperm are made (Spermatogenesis) within each testis, but complete their maturation process in the epididymis. Mature sperm are also stored within the epididymis until ejaculation. Immature sperm must make their way to the epididymis where they complete their development to become fully functional mature sperm cells. What happens? 1. Form an acrosome. 2. Cytoskeleton extends to form a flagellum (tail). 3. Produce extra mitochondria. 4. Lose extra cytoplasm to streamline. Parts of a mature Sperm Cell: Male Accessory Glands Three different glands produce fluids which are released into the system of ducts through which sperm travel. Sperm and fluids combined create semen. 1. Seminal glands (2) Located on the posterior surface of the urinary bladder Duct merges with the ductus deferens to form the ejaculatory duct Contribute the majority of seminal fluid during ejaculation and contains nutrients for the sperm. 2. Prostate gland Doughnut shaped gland that encircles the origin of the urethra Fluid released through duct into the urethra during ejaculation. Fluid activates sperm and counteracts the acidity of the female reproductive tract. 3. Bulbo-urethral glands (2) Pea sized, located below the prostate gland. Ducts empty into the urethra. Fluid flushes out any urine. This precedes ejaculation, occurs at same time as erection. Penis An organ that serves a dual function, reproductively it is the copulatory organ delivering sperm to the female reproductive tract, but it also serves in the elimination of urine. Contains erectile tissue (corpus spongiosum and corpora cavernosa). This tissue fills with blood during arousal causing an erection. The urethra passes through the erectile tissue and is the duct through which semen and urine travel to outside the body. Pathway for Sperm During ejaculation, semen is propelled through the duct system. This is under sympathetic control which causes smooth muscle contraction which, propels sperm from the epididymis through duct system, ejects seminal fluid from the seminal glands and fluids from the prostate gland. Epididymis Ductus (Vas) Deferens Ejaculatory duct Urethra Which of the above structures only contain sperm and which ones semen? Hypothalamus-Pituitary- Gonad Axis Regulates Sperm Production and the Release of Testosterone The hypothalamus secretes a releasing hormone called Gonadotropin Releasing Hormone (GnRH) when the concentration of testosterone in the blood is low. GnRH travels to the anterior pituitary via portal blood vessels. The anterior pituitary releases Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH) which are transported in the blood and target the testes. Testosterone Level Regulation LH activates secretory cells within the testes to release testosterone. Testosterone stimulates spermatogenesis within the testes as well as affecting other body sites. As levels of testosterone increase within the blood it acts as an inhibitor of the pathway. the hypothalamus stops releasing GnRH and the anterior pituitary stops releasing LH. This is an example of a negative feedback homeostatic mechanism.  Sperm Production FSH and testosterone together stimulate spermatogenesis in the testes. When the sperm count is getting high, special secretory cells within the testes release a hormone called Inhibin into the blood. Inhibin acts on the hypothalamus and anterior pituitary, it inhibits the release of GnRH and FSH shutting off the system.  Recall: Testosterone A steroid hormone that increases dramatically at the time of puberty in males. Stimulates spermatogenesis in the testes Causes growth of reproductive ducts, glands and the penis Causes the development of secondary sex characteristics Pubic, axillary and facial hair Increased hair on chest and other areas Increased size of larynx causing voice drop Increased bone size and density Increased skeletal muscle mass Increases metabolic rate Responsible for sex drive Testosterone is also found in females, at a much lower level, as the adrenal glands also produce it. Female Reproductive Strategy The reproductive strategy of females is to produce a few nutrient rich eggs (about 500 in their lifetime). Egg cells are the largest cells found in the human body and sperm cells are the smallest. Functions of the Female Reproductive System: 1. Produce eggs 2. Produce sex hormones Estrogens Progesterone 3. Nurture the development of the zygote into an embryo then fetus in utero as well as nurture the baby postpartum through the production of milk Overview of System Female Reproductive System Ovaries Paired, one on left and right Located on either side of the uterus. Produce and release eggs. Produce and release female sex hormones estrogen and progesterone which regulate the menstrual cycle as well as other things. Ovaries Within each ovary are many tiny ovarian follicles. Each ovarian follicle consists of an immature egg enclosed by support cells which are called follicle cells. A woman is born with all of the immature eggs she will have in her lifetime (within primary follicles). How is this different from males? Follicles are selected for maturation each month, and some will never go through the process. The follicle cells surrounding the developing egg each month make and release female sex hormones. Oviducts and Uterus The oviduct is the passageway for an ovulated egg to travel to the uterus, it is also the most common site of fertilization. The uterus is where implantation of an embryo occurs and completion of the development of a baby. Important Uterine Structures: 1. Uterine wall has a thick layer of smooth muscle which will contract during labour and delivery in response to oxytocin hormone. 2. Endometrium, the inner blood rich layer where implantation occurs. If a pregnancy has not occurred, this layer is shed during menstruation. 3. Cervix. The narrow opening of the uterus. Closed most of the month and sealed with thick mucous, opens and mucous Vagina A thin-walled tube connecting the uterus to outside the body. Located between the bladder and rectum. Functions: Passageway for delivery of menstrual flow and infants Site of sperm deposition during intercourse. Female Reproductive Tract The path an ovulated egg takes and eventually the birth of the fetus: Ovary Oviduct (fallopian tube) Uterus (including cervix) Vagina External Genitalia (Vulva) The opening of the vagina may be covered by a partial membrane called the hymen which typically ruptures by first tampon usage or sexual intercourse. Anterior to the vaginal orifice is the opening of the urethra and clitoris, erectile tissue which is highly innervated and sensitive to touch. Homologous to the penis in males. The vaginal orifice is protected by 2 skin folds: the labia minora and Note the that labia the passage of urine is separate from the majora. reproductive tract in females unlike in males. Hypothalamus-Pituitary- Gonadal Axis What happens each GnR month in the H ovaries and in the uterus is regulated by hormones and ultimately by the hypothalamus. Monthly Cycle Female monthly cycles are on average 28 days long. What happens in the ovary and uterus during this monthly cycle? Day 1 of your period is the first day of your monthly cycle, ovulation typically occurs halfway through your cycle so around day 14. Menstruation is extremely variable between women, duration of time, amount of blood lost, cramps, clots etc…. If you have heavy periods be mindful of your energy level and if you feel tired often get tested for iron deficiency anemia.  Day 1. Low Maturing follicle produces estrogen & an increasing amount of progesterone levels estrogen as ovulation cause nears. This estrogen menstruation. rebuilds the FSH from ant. endometrium in the Pituitary starts uterus. follicle development. Around Day 14. Surge in Around Day 28. LH from the Remaining follicle ant. Pituitary cells degrade, and leads to estrogen and ovulation progesterone levels drop. After ovulation. Remaining follicle cells of the ovulated egg in the ovary release progesterone and estrogen, thickening the Recall: Estrogen A steroid hormone analogous to testosterone in males. Estrogen increases at the time of puberty and has many effects on the female body. 1. Promotes embryonic female sexual development and primary follicles. 2. At Puberty causes: Maturation of the female reproductive tract (enlarges & become functional). Start of menstrual cycle Growth spurt Breast development Adipose tissue to increases in hips and breasts Pelvis to widen 3. Helps maintain ideal blood cholesterol levels 4. Facilitate calcium uptake Progesterone The pregnancy hormone Progesterone levels rise after ovulation and are maintained throughout pregnancy. If pregnancy did not occur progesterone levels drop at the end of the monthly cycle. Functions of progesterone: Enrich and maintain the endometrial lining of the uterus. This will become the placenta during pregnancy where exchange occurs between the mom and baby. Increase the thickness of cervical mucus Inhibit egg development and ovulation from the ovaries by blocking the hypothalamus and anterior pituitary glands from secreting their hormones. (GnRH, LH and FSH) Inhibit uterine muscle contractions.  Pre-Menstrual Syndrome (PMS) A combination of emotional and physical changes that occur during the week to 2 weeks leading up to your period. These typically resolve after the period commences. Possible emotional experiences include: More sensitive (quick to cry) Mood swings Less motivated to do activities you normally like Feeling hopeless, anxious and or overwhelmed Irritable, quick to temper Difficulty concentrating Possible physical symptoms: Cause: Breast tenderness or swelling Most women that experience Achy muscles and joints PMS have similar fluctuations in Headaches progesterone and estrogen as Feeling bloated other women, however they Difficulty sleeping are more sensitive to these changes. Premenstrual Dysphoric Disorder (PMDD) Symptoms in PMDD are so severe that they stop one from doing usual activities at school, home or work. Recent studies have found that women with PMDD likely have increased sensitivity to progesterone in particular causing increased activity in the limbic system of their brains. https://www.mind.org.uk/information-support/types-of-mental- health-problems/premenstrual-dysphoric-disorder-pmdd https://www.ementalhealth.ca/Canada/Premenstrual- Dysphoric-Disorder-PMDD-Information-for-Patients-and- Families/index.php?m=article&ID=76638 What to do if you have PMS or PMDD 1. Get to know your cycle Track when your symptoms typically begin and end. This way you can anticipate when they will occur in the future. Try not to overload your schedule during these times. 2. Look after your emotional wellbeing Spend time in nature, try relaxation techniques such as meditation/mindfulness, or yoga. Oral Contraceptives and Progesterone Birth control pills supplement your body with progesterone or a combination of progesterone and estrogen. Hormone(s) is/are present in pills days 1-21 and absent in pills 22- 28. How does this work? Progesterone (or progesterone/estrogen combination) tricks your body into thinking it’s pregnant! On days 22-28 no hormones This inhibits egg development are in the pills (placebo) and ovulation by blocking the causing menstruation to release of GnRH from the occur. hypothalamus and LH and FSH from the ant. Pituitary gland. It also thickens your cervical mucous making it harder for