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Natural Science
NATS 1675
Barbara Czaban

LECTURE 24 – FEMALE REPRODUCTIVE SYSTEM Female organs more CYCLIC than male reproductive system – complex Gonads – two ovaries - make eggs through oogenesis - produce hormones estrogen & progesterone UTERINE WALL – accommodate developing baby; contract during childbirth UTERUS – houses & nourishes developing baby; embryo -> fetus ENDOMETRIUM – lining of uterus; menstrual flow; site of implantation CERVIX – opening of uterus VAGINA – muscular tube; receives penis OVIDUCT – ciliated tube; conduct egg/embryo toward uterus (site of fertilization) OVARY – produce eggs & sex hormones CLITORIS – small organ, sensory nerves for sexual arousal LABIUM MAJORA – outer skin fold, part of external genitalia LABIUM MINORA – inner skin fold, part of external genitalia OVARIES PRODUCE EGG CELLS (OVA) & SEX HORMONES TUNICA ALBUGINEA covers surface Divided into inner medulla & outer cortex - OVARIAN MEDULLA loose connective tissue; contains blood vessels etc. - OVARIAN CORTEX germ cells develop, contains compact tissue, granular appearance, cells called ovarian follicles - Egg develops own fluid-filled follicle - Ovulation bursting of follicle & releasing egg LIGAMENTS hold each ovary in place BROAD LIGAMENT – attaches uterine tubes & uterus to walls and floor of pelvis SUSPENSORY LIGAMENTS – attaches ovary to pelvic wall has blood vessels & nerves OVARIAN LIGAMENTS – attached ovary to uterus OOGENESIS produce haploid gametes (contain half number of DNA molecules) OOGENSIS a CYCLIC event PRODUCES one egg each month OVULATION a CYCLIC event RELEASES one egg each month PART 1 – EMBRYONIC DEVELOPMENT OF OVARY - Germ cells arise from yolk sac; - Colonize gonadal ridges in fetal abdominal region by 5-6 weeks - Differentiate into oogonia and multiply until 5 month; 5-6 million - Transform into primary oocytes - Stay this way until puberty - Sits in center of follicular cells; eventually hormonally stimulated to develop alongside oocyte PART 2 – EGG DEVELOPMENT RESUMES IN ADOLESCENCE - Primary follicle, 1-7 layers follicle cells surrounding primary oocyte - FSH & LH released by anterior pituitary gland stimulates primary follicle to become secondary follicle matures into blister like graafian follicle - Graafian follicle bursts during ovulation - Release secondary oocyte into pelvic cavity; viable for 24 hours FOLLICULOGENESIS development of follicles around egg undergoes oogenesis PRIMORDIAL FOLLICLES – primary oocyte surrounded by follicular cells - concentrated in cortex, follicular cells pass nutrients & chemical signals to developing oocyte, secrete estrogen PRIMARY FOLLICLES – grow into larger oocytes and follicular cells SECONDARY FOLLICLES – larger oocytes & follicular cells (granulosa cells) - Thecal & granulosa cells secrete follicular fluid containing estrogen into antrum - Together, forms secondary follicles - Zona Pellucida protein gel secreted by cells around oocyte - Corona Radiata inner most layer of cells surrounding zona pellucida & oocyte MATURE (GRAAFIAN) FOLLICLES – normally one follicle from each month group becomes mature follicle destined to ovulate, others degenerate OVULATION TRIGGERED BY LH FROM ANTERIOR PITUITARY - During follicle maturation: primary oocyte develop into secondary oocyte - Ovulation releases secondary oocyte from follicle - Graafian follicle (mature follicle) swells & bursts - Follicular fluid & secondary oocyte released - After ovulation, secondary oocyte propelled to uterine tube STEP 1: Primary follicle contains primary oocyte. Follicle cells secrete sex hormone estrogen STEP 2: Layer of follicle cells thickens. Estrogen containing fluid accumulates, formulation of cavity STEP 3: Mature (graafian) follicle from rapid growth. Meiosis I forms secondary oocyte & polar body STEP 4: At ovulation, mature follicle ruptures, releases secondary oocyte STEP 5: Corpus luteum forms from follicle cells that remain in ovary. Secretes sex hormones estrogen and progesterone STEP 6: No pregnancy, corpus luteum degenerates. LECTURE 25 – FEMALE REPRODUCTIVE SYSTEM INTERNAL ACESSORY ORGANS – pair of uterine tube, uterus & vagina UTERINE TUBES - Open into uterus (oviduct, fallopian tube); 10 cm long & 0.7 cm in diameter - Muscular tube lined with ciliated cells; outer connective tissue; fertilization in upper 3 of uterine tube - Inner wall of uterine tube folded and lined with cilia; beat towards uterus and transport egg toward uterus; secretion transport sperm & egg; - Mucous, calcium, salts, glucose, proteins, bicarbonates, lactic acid UTERUS – Pear shaped organ; thick muscular chamber, opens roof of vagina, harbors fetus, expels fetus FUNDUS – broad superior; curvature BODY (corpus) – middle portion CERVIX – cylindrical inferior end LUMEN is triangular, two corners opening to uterine tube CERVICAL CANAL connects lumen to vagina CERVICAL GLANDS secrete mucus, prevents spread of microorganisms UTERINE WALL Perimetrium– external layer of loose connective tissue Myometrium – middle muscular layer, smooth muscle, most of uterine wall Endometrium – inner layer Stratum functional–sshed each menstrual period Stratum basali– regenerates new stratum functionalis each menstrual cycle During pregnancy– endometrium site of attachment of embryo; forms maternal part of placenta from which fetus nourished VAGINA (birth canal) 8-10cm distensible muscular tube -Discharge of menstrual fluid; receipt penis & semen; birth of baby VAGINAL LINING – childhood: single layer of cubed-shaped cells - puberty: estrogens transform to multi-layered flat cells VAGINAL RUGAE – folds for stretching FORNICES – spaces from vagina extending slightly beyond cervix BACTERIA – ferment glycogen, produce acidic pH in vagina EXTERNAL REPRODUCTIVE ORGANS: EXTERNAL GENITALIA AKA VULVA/PUDENDUM PUBIC SYMPHYSIS – cartilaginous joint uniting pubic bones LABIA MAJORA – pair of thick folds skin; external genitalia LABIA MINORA – pair of thin folds skin; space between forms vestibule VESTIBULE – space between labia minora encloses vaginal & urethral openings - VESTIBULAR BULBS – erectile tissue causes vagina to tighten around penis - VESTIBULAR GLANDS & PARAURETHRAL GLANDS - secrete mucus into vestibule SUMMARY OVARY – produces oocytes & female sex characteristics UTERINE TUBE – conveys secondary oocyte towards uterus; site of fertilization; conveys embryo towards uterus UTERUS – produces & sustains embryo VAGINA – conveys uterine secretions; receives penis; open channel for birth LABIA MAJORA – enclose & protect external reproductive organs LABIA MINORA – form vestibule; protect opening of vagina & urethra CLITORIS – sensory nerve endings in glans VESTIBULE – space between labia minora contains vaginal & urethral openings VESTIBULAR GLANDS – secrete fluids LECTURE 26 – FEMALE REPRODUCTIVE SYSTEM OVARIAN CYCLE - Series of events in ovary as eggs mature & ovulate - Managed by hormones from anterior pituitary gland UTERINE CYCLE - Series of events in uterus in preparation for receipt of fertilized egg - Managed by ovarian hormones; affect endometrium of uterus PREGNANT – development of endometrium for implantation NON-PREGNANT – “menstrual flow” shedding of endometrium FEMALE HORMONE SUMMARY ESTROGEN (ovaries) – mature eggs, development & maintenance of female reproductive structures & secondary sex characteristics, Thickness of endometrium PROGESTERONE (ovaries) – prepares uterus for implantation of embryo, maintains endometrium FSH (anterior pituitary) – development of follicle in ovary LH (anterior pituitary) – ovulation; formation of corpus luteum SUMMARY OF OVARIAN CYCLE DAY 1-13 follicle develops caused by FSH, follicle cells produce estrogen DAY 14 ovulation triggered by LH DAY 15-21 corpus luteum forms, secretes estrogen & progesterone DAY 22-28 corpus luteum degenerates, estrogen & progesterone levels drop SUMMARY OF UTERINE CYCLE DAY 1 onset of menstrual flow (breakdown of endometrium) DAY 6 endometrium gets thicker DAY 15-23 endometrium prepared for implantation by estrogen & progesterone DAY 24-18 endometrium begins to degenerate because of decline in progesterone STEP 1: Low progesterone & estrogen → GnRH → FSH STEP 2: FSH → follicles in ovary STEP 3: follicle cells → estrogen STEP 4: LH → ovulation → LH → transformations of follicle cells in corpus luteum STEP 5: Corpus luteum → estrogen & progesterone STEP 6: estrogen & progesterone → uterine lining (endometrium) in preparation for pregnancy STEP 7: if NO fertilization: corpus luteum degenerates; progesterone level drop → menstruation Estrogen level drop, FSH & LH drop; cycle starts again if Fertilization: embryo produces human chorionic gonadotropin (HCG) maintain corpus luteum → Progesterone & estrogen levels high, prevents menstruation DAY 1-14: follicular phase; DAY 15-28: luteal phase Corpus luteum → involution → corpus albicans → new primordial follicles LECTURE 27 – CELL REPRODUCTION Fertilization – combination of DNA from 2 parents creates genetic diversity Fertilized egg: zygote; human adults ~10 to 65 to 100 trillion living cells Cell size– DIVIDE instead of growing larger to LIMIT their SURFACE AREA TO VOLUME RATIOS SA of cell is its cell membrane as cells get larger, V increase faster than SA SA/V ratio decreases = less SA per unit volume therefore less SA for nutrient/waster diffusion CELLS SOLVE THIS BY: dividing; getting thinner; forming microvilli; storing nutrients CELL CYCLE G1 – cell growth S – duplication of DNA G2 – forming materials required for cell division M – mitosis; nuclear & cytoplasmic division; formation of 2 daughter cells INSIDE CELL: DNA molecules associate with various proteins CHROMATIN: non-dividing; DNA long & thin; wrapped around histone proteins CHROMOSOME: when dividing; coiled tightly ; shortened - Both same materials but called differently at different times CHROMOSOME STRUCTURE One duplicated chromosome - Two replicated DNA molecules; 2 sister chromatids - Both are identical; still ONE chromosome - Chromatids are still joined to each other Chromatids separate during cell division - Called chromosomes again - Each unduplicated chromosome For a diploid human cell, 2 complete sets of chromosomes from a single cell constitute a karyotype of that cell Pair of sister chromatids have CENTROMERE (DNA that is hidden beneath the kinetochore proteins) - Kinetochore (proteins attached to the centromere) - NOT ALWAYS AN “X” SHAPE Human SOMATIC CELLS (body cells) – 2 sets of each type (23 pairs) – humans have 23 different type chromosomes ▪Each pair = 2 HOMOLOGOUS CHROMOSOMES ▪Total of 46 chromosomes - 22 pairs of AUTOSOMES - 1 pair of SEX CHROMOSOMES (Female – XX, Male – XY) Human GAMETES (sperm or egg) 1 set = total of 23 (22 autosomes, 1 sex chromosome) DIPLOID number (2n) Refers to 2 members of each pair (total number of chromsomes) General body cells (somatic cells) – ensure by mitosis HAPLOID number (n) Refers to 1 member of each pair of chromosomes Only in sex cells (egg/sperm) – produced by meiosis HOMOLOGOUS CHROMOSOMES - Contains DNA that codes for the same genes – same genes in the same location by different ‘versions’ of those genes – sister chromatids are exact same replicas but chromosomes are not - Produces of fertilizations, one chromosome pair originated from femal parent, second chromosome of pair originated from male parent - Fertilization restores homologous pairs in zygote (cell is diploid) Chromosomal composition found in most femal human cells (46 chromosomes) when not dividing Chromosomal composition found in most human gametes (23 chromosomes) LECTURE 28 – CELL REPRODUCTION 3 different types oCELL DIVISION ▪REPLICATION – duplication of genetic material (DNA) ▪MITOSIS – equal distribution of genetic material to each of 2 daughter cells ▪CYTOKINESIS – divison of cytoplasm PREPARATION FOR CELL DIVISION - DNA replicated; sister chromatids with 2 identical copies of DNA with associated proteins - Tightly associated at CENTROMERE – serves as attachment site for KINETOCHORE MIOTIC SPINDLE APPARATUS (MIOTIC SPINDLE) organizes and sorts chromsomes during mitosis ▪ CENTROSOMES – microtube organizing center (MTOC) – single centrosome duplicates at the beginning of M Phase – each define spindle “pole” ▪ SPINDLE FORMED FROM MICROTUBLES – polymers of tublin proteins -ASTRAL: position spindle in cell -POLAR: separate 2 poles -KINETOCHORE: attached to kinetochore bound to centromeres of each chromosome ① PROPHASE ▪ Duplicated chromosome condense & become visible ▪ Nuclear envelope starts to break down ▪ Centrosome move apart & miotic spindle begins to form ② PROMETAPHASE ▪ Nuclear membrane gone; Bipolar miotic spindle forms - “Poles” at opposite ends; cytoplasm cleared ▪ Chromosomes develop kietochore at centromere - Attach to kinetochore microtubles (kMT) ▪ Chromosomes move along spindle - Homologous chromosomes move independent of one another ③ METAPHASE ▪ Chromosomes at their most compact ▪ Positioned at equatorial plate half-way between poles ▪ Each kinetochore of a duplicated chromosome is connected to one fo the 2 poles by kMTs ④ ANAPHASE ⑤ TELEPHASE ▪ Kinetochore separate; sister chromatids separate ▪ Miotic spindle disperses ▪ Sister chromatids move to opposite poles ▪ Chromosomes unwinde and lose distinct - Separated chromatids now are separate identity Chromosomes ▪ Nuclear envelope forms; 2 nuclei ▪ Kinetochore microtubles shorten - each with same # of chromsomes as ▪ Poles move apart and spindle elongates parent cell ▪ Motor proteins involved ▪ Cytoplasm begins to divide ▪ TWO MECHANISMS AT ONCE A) kinetochore microtuble shortening - Motor proteins involved B) Sliding of overlapping non-kMT - Spindle enlongation - Motor proteins involved CYTOKINESIS – Clevage in animal cell Cell plate in plant cells CLEVAGE FURROW LECTURE 29 – MEIOSIS Meiosis involves TWO CELL DIVISIONS in formation of 4 HAPLOID GAMETES - Keeps chromosome numbers constant: haploid gametes (egg cells, sperm); fertilization restores diploid # - Increases genetic variability: crossing over & independent assortment - Failure of chromosomes to separate during meiosis creates: nondisjunction GERM CELLS – diploid (2n) Found in GONADS – ovary testis, anther Each cell has a pair of homologous chromosomes; formed by mitosis Undergo meiosis to produce haploid gametes GAMETES – haploid (n or 1n) Each has ONE member of each homologous pair Sex cells – egg (ovum) sperm – formed by meiosis; participate in fertilization FERTILIZATION is the union of gametes and restores diploid number in zygote OVERVIEW OF MEIOSIS ① The DIPLOID PARENT CELL contains two homologous pairs of chromosomes ② DNA REPLICATION during interphase forms two copies of each chromosome, copies remain ATTACHED ③ During MEIOSIS I homologous chromosomes separate into TWO HAPLOID cells, each one member of each pair ④ During MEIOSIS II sister chromatids separate and FOUR HAPLOID daughter cells will develop into gametes SUMMARY OF MEIOSIS I ▪ Duplicated homologous pair, align, separate ▪ Result in two HAPLOID daughter cells ▪ 2 chromatids/chromosome – REDUCTION DIVISION INTERPHASE – DNA replicates; Copies remain attached to one another by centromere; Each copy is called chromatid PROPHASE I – Chromosomes condense; SYNAPSIS occurs (homologous chromosomes pair and become perfectly aligned with one another) Crossing over takes place METAPHASE I – homologous pairs line u at the midline of the cell; Spindle fiber from one pole attaches to one member of each pair Spindle fiber from opposite pole attaches to the homologue TELOPHASE I – One member of each homologous pair is at each pole CYTOKINESIS occurs and forms two haploid daughter cells Each chromosome still consists of two chromatids HOMOLOGOUS CHROMOSOMES COME TOGETHER - form a tetrad (bivalent) – 4 chromatids CROSSING OVER takes place at chiasma between nonsister chromatids – during prophase I - Exchange chromosome segments; Genetic recombination mixture of DNA from two parents - Creates genetic variety INDEPENDENT ASSORTMENT occurs during metaphase I – random alignment - Maternal & paternal member of homologous pairs align randomly at equatorial plate - Creating a random assortment of maternal and parental chromosomes in daughter cells - Creates genetic variety SUMMARY OF MEIOSIS II ▪ Duplicated chromosomes align, separate ▪ Result in four HAPLOID daughter cells ▪ 1 chromatids/chromosome INTERKINESIS – A brief interphase-like period; No DNA replication; DNA is chromatin PROPHASE II – Chromosomes condense; Occurs in both daughter cells METAPHASE II – Chromosomes line up on equatorial plate independently as in mitosis TELOPHASE II – One complete set of chromosomes is located at each pole CYTOKINESIS occurs in both daughter cells, forms four haploid daughter cells LECTURE 30 – GAMETES AND GENETIC VARIATION REVIEW OF MEIOSIS IN HUMANS 46 CHROMOSOMES, EACH WITH 2 CHROMATIDS: DIPLOID AFTER FIRST MIOTIC DIVISION – 23 CHROMOSOMES, EACH WITH 2 CHROMATIDS: HAPLOID AFTER SECOND MIOTIC DIVISION – 23 CHROMSOMES, EACH CHROMATID INDEPENDENT CHROMSOME: HAPLOID SPERMATOGENESIS GROWTH – SPERMATOGONIUM (diploid male reproductive cell) MEIOSIS I – PRIMARY SPERMATOCYTE (diploid) becomes SECONDARY SPERMATOCYTES (haploid) MEIOSIS II – SECONDARY SPERMATOCYTE (haploid) becomes SPERMATIDS (haploid) DEVELOPMENT OF SPERM CELLS Nucleus + mitochrondria + golgi apparatus → develops a flagellum → excess cytoplasm and most organelles including golgi apparatus is lost → mitochondria and centriole (MIDPIECE) develops → tale, midpiece, and head (nucleus + acrosome) is formed. OOGENESIS begins before birth ▪During early fetal development - diploid oogonia numbers increase in ovaries by mitosis ▪ During month 3 - oogonia enlarge and store nutrients - start becoming primary oocytes - enter MEIOSIS I but not completed
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