Biology Notes (Reproduction System) PDF

BIOLOGY NOTES Reproduction System: Introduction: Definition: Reproduction is one of the 7 life processes. Humans use sexual reproduction to produce their young. Two parents (M and F) have different reproductive systems and organs that produce different sex cel...

BIOLOGY NOTES Reproduction System: Introduction: Definition: Reproduction is one of the 7 life processes. Humans use sexual reproduction to produce their young. Two parents (M and F) have different reproductive systems and organs that produce different sex cells Types of Reproduction: a. Asexual Usually done by animals and plants (vegetative) b. Sexual Can be done by all living things but in plants it’s called generative. Sexual Reproduction 2 individuals generate a new individual that inherits characteristics from both parents. Requires gametes which are formed in Gonad by gametogenesis. The key mechanism to gametogenesis is Meiosis. Gametes are formed haploid (half the genetic content ‘n’) Gametes -> 2 specialized cells (female n male) or sexcells (sperm n ovum) Gonad -> Sex organs Meiosis -> A special cell division in which the daughter cells receive half of the genetic content of parent cell  Human Reproductive System: Male Reproductive System: Divided into 3 parts; main organ, duct and accessory glands Most of the male reproductive system is located outside the body Main sex organs: Penis and Testes Male Reproductive System: 1. Main Organ a. Testes Produce sperm and male hormone called testosterone. Oval shaped organ where sperm are produced and matured. Seminiferous tubules -> Tightly coiled tubes within the testes where sperm are created 2. Duct a. Epididymis Located at the top of testes. Sperm are stored here for 6 weeks until they ripen to maturity after being created in the testes. Tightly coiled tube that stores sperm b. Sperm Duct/Vas Deferens Two long thin muscular tubes that serve as a passageway for sperms from testes to urethra. Rapid transport of sperm. Transport sperm from epididymis to urethra c. Urethra A dual purpose tube that semen and urine pass through when discharged from the body Semen (seminal fluid) -> fluid that is emitted from the male reproductive tract and that contains sperm cells, which are capable of fertilizing the female's eggs.  d. Penis A copulation organ. The male organ for sexual intercourse, reproduction and urination. Reproductive purpose is to deposit semen to the vagina e. Ejaculatory Duct Conducts sperm to penis. Transport liquid from seminal vesicle into the prostate gland 3. Accessory Glands a. Scrotum A sac-like pouch made of skin located behind the penis. Hold the testicles and keep them at a cooler temperature. Contains the testicle and epididymis. b. Seminal Vesicles 2 small glands that secrete a thick fluid that nourishes and enables/the sperm to move. Secretes most fluid in semen c. Prostate Glands Surround the urethra beneath the bladder. A large gland which adds fluid to sperm to create semen. Secretes some fluid in semen. About the size of a walnut. d. Cowper Gland (Bulbourethral Gland) 2 small pea-sized glands located beneath the prostate gland. It secrete a sticky fluid that helps to neutralize the acidity of the urethra Male Hormones: Leydig Cells -> the cell that produces testosterone but are stimulated by Luteinizing Hormones (LH) located in tissues between seminiferous tubule Functions of testosterone: a. Governs growth, form, and functions of the male reproductive tract b. Stimulates sexual behavior c. Promotes secondary sexual traits (facial hair, deepening of voice) Structure of sperm: Mature sperm: 9-10 weeks of processing Nourished with secretion from sertoli cells Tail (flagellum) Midpiece (contain mitochondria) Head ○ Nucleus with DNA organized into chromosomes ○ Acrosome: cap with enzymes to penetrate egg Female Reproductive System Female Reproductive System: 1. Main Organ a. Ovary Organ that produces eggs and stores female egg cells (oocytes). They produce sex hormones called estrogen and progesterone. Adds secondary sexual traits (fat deposit in breast, hips and buttlocks). Contains hormones that cause egg to mature Oocytes -> Immature eggs, released into oviduct and travel to uterus Estrogen -> Repairs endometrium and controls secondary sexual traits  2. Duct a. Fallopian tube/Oviduct The tubes that carry an egg from the ovary to the uterus. A site for fertilization. 3. Accessory Glands a. Fimbriae Eggs are “catched” by fimbriae and passed to the oviduct, which conveys them to the uterus. b. Uterus / Womb Internal cavity here a fertilized egg will implant and develop into an embryo. It’s well-supplied with blood and is part of the uterus, into which the embryo implants during pregnancy and is shed during menstruation. Chamber where a new individual develops. Nourished the fetus Myometrium -> Thick layer of smooth muscle Endometrium -> The lining of the uterus c. Cervix (lower portion of the uterus) The ‘neck’ of the uterus. The opening of the uterus into the vagina. A ring of muscle. Secretes mucus that enhances sperm movement into uterus and reduces the embryo’s risk of bacterial infection d. Vagina A muscular tube which connects the uterus with the outside of the body. Where sperms are deposited during sexual intercourse. Birth canal. Structure of Ovum: The size of an ovum is much bigger than a sperm. The nucleus contains DNA. Outside the membrane of the ovum, there is a jelly layer called zona pellucida. Menstrual Cycle Occurrence: 28 days Starts: between 10 and 14 years old 4 phases of the menstrual cycle: a. Menstrual Phase First stage of the menstrual cycle, when you get your period. The egg from the previous phase isn’t fertilized so the level of hormones (estrogen n progesterone) drop. The thickening of uterus lining for pregnancy is shed through your vagina. During this period, you release blood, mucus and tissues from the uterus. Average menstrual cycle: 3 - 7 days Symptoms: Cramps Bloating Mood Swings Irritability Headaches Tiredness Low back pain b. Follicular Phase Starts on the first day of period and ends during ovulation. Starts when the hypothalamus sends signals to the pituitary gland to release FSH. Only the healthiest egg will mature, the rest will be reabsorbed by the body. The maturing follicle sets off a surge in estrogen to thicken the lining of the uterus (creates a nutrient-rich environment for embryo) FSH -> follicle-stimulating hormone. Stimulates your ovaries to produce around 5-20 sacs called follicles which contain an immature egg. Stimulates follicle growth Average follicular phase -> 16 days c. Ovulation Phase When your ovary releases a mature egg. The egg travels down the fallopian tube towards the uterus to be fertilized by sperm. Rising estrogen levels trigger the pituitary gland to release LH; this is what starts ovulation. The only time during your menstrual cycle when you can get pregnant LH -> Luteinizing Hormone Symptoms: A slight rise in basal body temperature Ovulation Phase -> during 14 days (last for 24 hours) Hormones during ovulation: Ovarian Cycle ○ Born with ~300 oocytes arrested in meiosis I ○ 1 primary oocytes mature / month during the female’s menstrual cycle Primary Oocytes ○ Surrounded by a layer of nourishing cells ○ Forms the follicle, grows due to FSH and LH ○ Level of estrogen increase ○ Oocytes complete meiosis I before ovulation  Secondary Oocytes ○ Gets most of the cytoplasm; begins undergoing meiosis II ○ Surges of LH ○ Ovulation: release of secondary oocytes from the ovary Enters the oviduct ○ Fimbriae helps sweep it in ○ If fertilization occurs, meiosis II is completed d. Luteal Phase After the follicle releases it’s egg, it changes into corpus luteum.This structure releases hormones (progesterone n estrogen) The rise in hormone keeps your uterine lining thick and ready for fertilized egg to implant. Symptoms of premenstrual syndrome (PMS): Bloating Mood changes Headache Weight Gain Changes in sexual desire Food cravings Trouble sleeping Luteal Phase -> 14 days If you get pregnant Your body produce human chorionic gonadotropin (hCG) hCG -> The hormone detected by pregnancy test. Helps maintain the corpus luteum and keeps the uterine lining thick Also the hormone to prevent menstruation. If you don’t get pregnant The corpus luteum shrinks away and gets reabsorbed, which leads to decrease of estrogen and progesterone levels (causes onset of your period). Uterine lining will shed during the period. Menarche -> First menstruation (age 10-16) Menopause -> Cessation of menstruation, fertility ceases (between 40s and 50s). Temporary symptoms of decline estrogen Endometriosis -> Tissues spread and grow outside of the uterus, leading to scarring, symptoms and treatment. Painful during menstruation Fertilization The process when sperm and oocytes unite Germ cells -> produce gametes Zygote -> Sperm enters a secondary oocytes Capacitation -> Acrosome membrane is weakened Conception -> fertilization of an egg by a sperm, occuring in the oviduct Cleavage -> The process of zygote beginning to divide Blastocyst -> A ball of cell with a central cavity Implantation -> The process from the zygote is formed till the embryo sinks in the endometrium. After blastocyst formation, the embryo implants into the endometrium. The embryo releases hCG. Duration of pregnancy in other species correlates with body size and maturity of the young at birth hCG -> human chorionic gonadotropin, prevents menstruation Pregnancy/Gestation -> The condition of carrying one or more embryos in the uterus Twins 2 types of twins: a. Identical (monozygotic) Occurs when 1 sperm fertilizes 1 egg. Blastocyst splits into 2 cells, then develops into 2 different embryos. Since the twin comes from the same fertilized egg, they’ll share identical features Types of identical twins: DCDA Twins (dichorionic diamniotic) Have their own placenta, inner membrane, and outer membrane MCMA Twins (monochorionic monoamniotic) Share everything MCDA Twins (monochorionic diamniotic) Share the same placenta and chorion but different amnion Conjoint / Siamese Twins  Twin-twin transfusion syndrome (TTTS): Blood flows from one twin to the other, resulting in one baby getting too much blood and the other baby not getting enough. (one baby rakus the other not enough food). Most likely to happen to MCDA and MCMA twins. What do they do when it happens? b. Fraternal (dizygotic) Occurs when sperm fertilize distinct eggs. The mother releases multiple eggs. Fertilization of separate eggs in different embryos. The placenta will fuse if the babies get too close. Not even a bit identical. Gamete (Sex Cell) Production The formation of gametes is called gametogenesis. In females it’s called oogenesis and male it’s called spermatogenesis. The process involves mitosis and meiosis. a. Spermatogenesis The forming process of male gamete (sperm). Occurs in the seminiferous tubule and it needs testosterone. Starts as puberty around 13-17 years old. Equal division of cells and is involved in gamete production. Lifelong and continuous release 1. Differentiation of primordial germ cells into spermatogonium [Mitosis] 2. Spermatogonium differentiate into primary spermatocytes (2n = diploid) [Meiosis I] 3. Primary spermatocytes divide and produce secondary spermatocytes (n = haploid) [Meiosis II] 4. Secondary spermatocytes produce spermatids 5. Spermatids turn into functional sperm cells (4 sperms) Andropause -> when a male stops producing sperm  b. Oogenesis The formation of female gametes. Occurs in the ovary. Begins in the fetus (400 oocytes) and released during puberty (menstrual cycle). Continuously releasing for 400 months (33-35 years) then ovulation stops (menopause). Ovulation happens in the Ovum Menopause -> the time that marks the end of your menstrual cycle 1. Diploid oogonium (oogonia) develops into primary oocytes [Mitosis] 2. Primary oocytes (develops in the follicle) divides into haploid secondary oocytes and a polar body [Meiosis I] 3. Secondary oocytes divides into a mature ovum and another polar body (won’t happen unless fertilized by a sperm) [Meiosis II]  Cell Division: Introduction: Definition: Process by which a cell divides into 2 new cells. Life begins as a zygote (fusion of egg cells and sperm). Each nuclei contains 23 sets of chromosomes and 46 sets when fused. Haploid -> single set of chromosomes Diploid -> two sets of chromosomes Why do cells need to divide?: Living things grow by producing more cells Repair of damaged cells If cell gets too big, it cannot get enough nutrients into the cell and wastes out of the cell Mitosis: Definition: Division of the nucleus into 2 nuclei, each with the same number of chromosomes, occurs in all the somatic cells. Produces genetically identical cells Mitosis occurs -> so each new daughter cell has nucleus with a complete set of chromosomes Function of Mitosis: Growth Tissue repair/ replacing damaged cells Asexual reproduction How mitosis works: Cell Cycle: Series of events cells go through as they grow and divide. Cells grow, prepare for division, divide to form 2 daughter cells (perfect copy) then repeat. An ordered sequence of events that extends from the time a cell is first formed from a dividing parent cell until its own division. When cells become old they die and get replace with new cells Interphase: Period of cell growth and development. The longest phase in mitosis. 3 Phases: a. G1 Phase Where cells do most of the growing, increase in size and synthesize new proteins and organelles. b. S Phase Chromosomes replicate and the synthesis of DNA molecules takes place. If a cell enters S phase, it completes the rest of the cycle c. G2 Phase Organelles and molecules needed in cell division are produced, shortest of the 3 phases. What occurs during Interphase: DNA replication Cells grow, carries out cell activities, replicates all other organelles Where cells spends most of their life Phases of Mitosis:  1. Prophase Chromosomes coil up Nuclear envelope disappear Spindle fibers formed by centriole 2. Metaphase Chromosome line up in the middle of cell Spindle fiber connects to chromosomes No longer a nucleus present 3. Anaphase Chromosomes copies divide Spindle fiber pulls chromosomes to opposite poles 4. Telophase Chromosomes uncoil Nuclear envelope form 2 new nuclei are formed Spindle fibers disappear Divide into 2 cells at opposite poles Cytokinesis: The division of the rest of the cell (cytoplasm and organelles) after the nucleus finishes dividing. The final process, splitting of cytoplasm. After cytokinesis, cells return to interphase. Animal Plants Summary of Mitosis: Meiosis: Definition: The process of making gametes (sperm/egg cells). Basis of sexual reproduction. Only germ cells undergo meiosis. Produce non-identical cells. Division of cells in the ovaries and testes. 3 ways genetic diversity is increased by mitosis: 2 parents contribute ½ of genetic material to offspring Crossing-over in Prophase I Chromosome alignment in Metaphase I Interphase: Similar to Mitosis Interphase Chromosomes replicate in S phase Each duplicated chromosome consists of two identical sister chromatids attached at their centromeres. Centriole pairs also replicate Nucleus and nucleolus visible Meiosis I (4 phases): Cell division that reduces the number of chromosomes by half (haploid). a. Prophase I Longest and most complex phase (90%) Chromosomes condense Synapsis occurs - Homologous chromosomes come together and form tetrad Tetrad -> 2 chromosomes/4 chromatids Homologous Chromosomes aka Tetrad ○ Pair of chromosomes that are similar in shape and size ○ Tetrad carry genes controlling the same inherited traits ○ Each locus is in the same position  ○ Humans has 23 pairs of tetrads 22 pair of autosomes 1 pair of sex chromosomes Locus -> position of genes Crossing-over ○ Occur between non-sister chromatids at sites called chiasmata ○ Segments of non-sister chromatids break and reattach to the other chromatid. ○ Chiasmata are where chromosomes touch each other and exchange genes ○ Causes genetic recombination Genetic Recombination Sex Chromosomes Nucleus & Nucleolus disappear Spindle forms Chromosome coils & synapsis occurs Tetrads form & crossing-over occurs  b. Metaphase I Shortest phase Tetrads align on the equator Independent assortment occurs - chromosomes separate randomly causing genetic recombination Formula: 2n c. Anaphase I Homologous Chromosomes separates and moves towards the poles Sister chromatids remain attached at their centromeres d. Telophase I Each pole now has a haploid (1n) set of chromosomes. Cytokinesis occurs and two haploid daughter cells are formed. Meiosis II (4 phase): Doesn’t have an interphase so it’s very short, No DNA replication. Similar to mitosis. a. Prophase II Same as prophase in Mitosis ○ Nucleus & nucleolus disappear ○ Chromosomes condense ○ Spindle forms b. Metaphase II Same as metaphase in Mitosis c. Anaphase II Same as anaphase in Mitosis ○ Sister chromatids separate  d. Telophase II Same as Telophase in Mitosis ○ Nuclei and Nucleoli reform ○ Spindle disappear ○ Cytokinesis occurs ○ 4 haploid daughters are produced called gametes Variation aka Genetic Recombination Important to the population as the raw material for natural selection All organisms are not alike Strongest “most fit” survive to reproduce & pass on traits Summary of Meiosis Meiosis I A reduction division Early prophase → late prophase → metaphase → anaphase → telophase Meiosis II A copying division Late prophase → metaphase → anaphase → telophase → cytokinesis Comparison  Contraception/Birth Control: Definition The use of medicines, devices, or surgery to prevent pregnancy. Important to keep family size small and to control the increase in human population. Natural Method Rhythm Calendar Avoid sexual intercourse when the woman has an egg in her oviduct. To predict her ovulation period and avoid sexual intercourse 3/4 days before and after ovulation. Chemical Method Spermicide Used to kill sperm when they enter vagina for female Contraceptive Pill Contains progesterone and estrogen that can stop eggs from being produced in ovaries for females. Daily doses Injection Contains progesterone and estrogen which can prevent the process of egg maturation and ovulation for females. One each month. IUS (Intra Uterine System) A type of IUD that contains hormones that prevents implantation Mechanical Method Condom Placed over the erect penis to trap semen when released and to stop it entering the vagina for male. Prevent pregnancy. Diaphragm / Cap A circular rubber sheet which is placed over the cervix on the top of vagina so sperm can’t pass into the uterus for females and males. Prevent pregnancy by killing sperm.  IUD (Intra Uterine Device) A device placed inside the uterus to prevent implantation for females. Surgical Method Permanent Effect Vasectomy A procedure in which the 2 vas deferens that carry sperm are surgically altered (cut or tied) so sperm can’t pass through to fertilize a woman’s egg. Used by male Tubectomy Contraception where the fallopian tubes are cut and tied so the eggs are prevented from traveling to the uterus. Used by females  Sexually Transmitted Disease: Viruses: 1. HIV Human Immunodeficiency Virus (Retrovirus) Invades and destroys the helper T cells to replicate itself No cure Slowly destroys the immune system Transmitted by: Sexual Contact, Sharing needles, Heredity(Placenta), Direct contact of body fluids (blood) Not transmitted by: Air/Water, Insect/Pets, Sharing, Saliva/Sweat/Tears/Kissing 2. AIDS Acquired Immunodeficiency Syndrome Symptoms may appear ~10 years after HIV infection HIV is the virus that cause AIDS Limits the body’s ability to fight infection No cure How to Prevent: ○ Use Condoms ○ Avoid usage of needles & drugs ○ Intake of nutritious food ○ Avoid breast-feeding ○ Avoid intercourse w/ sex workers & addicted drug users ○ Keeping yourself healthy 3. Genital Herpes (herpes simplex) Caused by Herpes Simplex Periodic eruption of small, painful blisters in genitals Infection: Contact with fluid from there sores Type 1: infects the lips, tongue, mouth and eyes Type 2: Genital Infections No cure but antiviral drugs can reduce pain Similar to chicken pox  4. Endometriosis Tissues spread and grow outside of the uterus, leading to scarring, symptoms and treatment. Painful during menstruation Surgery 5. Cervical Cancer Caused by Human papilloma virus (HPV) Infects the Cervix Continuous bleeding Extremely Contagious Anti-HPV vaccine Painless growth in genital area Bacterium: 1. Gonorrhea (Neisseria gonorrhoeae) May have no symptoms at first (female) Caused by Neisseria Gonorrhoeae Antibiotic Resistance Males discharge pus (kencing nanah) Cause sterility if untreated Infects Genital Organs 2. Syphilis (Treponema pallidum) Early symptoms may be painless and develop into extensive rash Caused by Treponema Pallidum Tertiary stage can appear after 5-20 years from initial infection Infection of newborn Can be heredity Infects genital organs normally in female Fungi: 1. Candidiasis Caused by candida albicans Yeast Infection Healthy woman has small numbers in vagina Causes problems: ○ Vaginal Itching ○ Burning ○ Heavy Curdy white discharge 2. Pubic Lice Caused by Arachnid Crabs 3. Trichomoniasis Caused by Trichomonas Vaginalis Protozoan Good luck