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REPRODUCTIVE SYSTEM MALE AND FEMALE

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Presentation on theme: "REPRODUCTIVE SYSTEM MALE AND FEMALE"— Presentation transcript:

1 REPRODUCTIVE SYSTEM MALE AND FEMALE

2 Human Life Cycle Adult has 46 chromosomes 23 pairs = diploid
meiosis occurs in gonads -- leads to gametes -- each is haploid, has 23 chromosomes --each is unique because of certain steps in meiosis that create genetic variation -- meiosis is not mitosis ZYGOTE = FERTILIZED EGG

3 Each pair is called a homologous chromosome
KARYOTYPE Each pair is called a homologous chromosome 22 autosomes and one pair of sex chromosomes XX = female; XY = male Each pair has 2 alleles of each gene Alleles are variant forms of a gene XY Both alleles may be active or one may be silenced by “genomic imprinting” which refers to epigenetic changes (DNA methylation or modification of histones)

4 BARR BODIES In females, one of the two X chromosomes is inactive. This produces a visible Barr Body. An easy way to visually determine the sex of a cell.

5 Sex Determination A gene of the Y chromosome codes for sex-determining factor, which leads to the development of testes before day 50 Rare XX males: scientists discovered they had a region of Y chromosome inserted into X chromosome SRY for sex-determining Region of Y Develop w/in 50 days

6 Klinefelter Syndrome 47 instead of 46 chromosomes XXY Due to nondisjunction Failure of XY to separate in the father Person is male, infertile Lower than normal testosterone

7 Fetus gets only one chromosome, the X, from the mother
Turner’s Syndrome Fetus gets only one chromosome, the X, from the mother Nondisjunction results in O from father Infertile Lower than normal estrogen Turner’s Syndrome XO

8 TESTICULAR FEMINIZATION SYNDROME
Normally functioning testes (inside body cavity); testosterone is normal, but is not under negative feedback control, and so a lot of it is produced and turns into estrogen Cells lack testosterone receptor Female genitalia develop Vagina ends blindly Uterus and fallopian tubes do not develop

9 Endocrine Regulation Hypothalamus secretes GnRH GnRH stimulates anterior pituitary to release LH + FSH (gonadotropins) “tropin” means “stimulating effect” gonads are stimulated with release of LH when puberty begins. This stimulates the formation of sex hormones. person becomes sexually mature, not necessarily emotionally mature.

10 OVERVIEW OF HORMONAL CONTROL

11 Female Reproductive Organs

12 Oogenesis At 4-5 months of gestation, ovaries contain 6-7 million oogonia (egg-forming cells) Most die Others begin meiosis and become primary oocytes toward end of gestation Oogenesis is arrested at prophase I of meiosis Follicle = hollow ball of cells containing oocyte 400 will ovulate during lifespan

13 Oogenesis In response to FSH stimulation, follicles get larger, becoming secondary follicles Graafian follicle = the follicle that forms an antrum (fluid filled sac) and is ovulated The primary oocyte completes meiosis I and is called secondary oocyte Meiosis II begins, but is arrested at metaphase II

14 Zona pellucida is a barrier to sperm penetration
Oogenesis After the secondary oocyte forms, layers of cells form around it (zona pellucida and corona radiata) Zona pellucida is a barrier to sperm penetration Corpus luteum forms (yellow body) Secretes estrogen and progesterone Negative feedback to hypothalamus and pituitary shuts off further ovulation Birth control pill is like the corpus luteum

15 Oogenesis By the 10th – 14th day of cycle, ovulation occurs If it is not fertilized, it degenerates in 1-2 days If it is fertilized, it completes the second meiotic division Fertilized egg is called the zygote

16 Menstrual Cycle Approximately 28 days Day 1 = first day of blood flow Menstruation = shedding of endometrium, which becomes thickened due to estrogen and progesterone

17 Menstrual Cycle Changes occur in cycle
Follicular phase – day 1-13 – primary follicle grows (stimulated by FSH), ovary secretes estrogen; estrogen reaches a peak at day 13 – 14, which stimulates the pituitary to secrete LH (LH surge), which causes ovulation Luteal phase – corpus luteum makes progesterone and estrogen

18 Changes occur in endometrium
Menstrual Cycle Changes occur in endometrium Proliferative phase – day 1-13 – increasing estrogen from ovary stimulate proliferation of endometrium Secretory phase – combined action of estrogen and progesterone thickens the endometrium Menstrual phase – absence of fertilization causes hormones to fall. Endometrium is not maintained.

19 Menstrual cycle

20 Additional information
Rhythm method of birth control – rise in temperature from LH (not reliable) Ovulation test kit – based on the LH surge; LH is found in urine Fertility pills – combinations of LH and FSH cause ovulation; may result in multiple eggs released Women living together – pheromones released from nasal cavity may trigger hypothalamus to release hormones simultaneously

21 Additional information
Amenorrhea – lack of menstruation; possible causes: few energy stores (adipocytes). Adipocytes release leptin which stimulates GnRH. Stress also shuts off GnRH Menopause – ovaries stop working; 50 is an average age, but differs among women

22 Over 300 million sperm enter the female at ejaculation.
Fertilization Over 300 million sperm enter the female at ejaculation. Only about 100 of these live to enter the fallopian tube. Fertilization occurs in fallopian tube (aka oviduct or uterine tube)

23 pH, Ca2+ and cAMP in sperm increases higher pH activates the flagellum
Capacitation of sperm In order to fertilize the ovum, a sperm must become capacitated. This takes at least 7 hours after ejaculation. pH, Ca2+ and cAMP in sperm increases higher pH activates the flagellum Capacitated sperm are guided to the oocyte by chemotaxis and thermotaxis

24 Sperm Sperm Oocyte Sperm
(b) Sperm surround the oocyte, attacking its defensive barriers. Oocyte Sperm

25 Sperm must degrade zona pelucida (acrosome reaction)
Only nucleus enters egg Zygote mitochondria are from the mother Cytoplasmic RNA establish polarity

26 Ca2+ has several effects:
Acrosome reaction When the sperm enters the oocyte, Ca2+ is released from endoplasmic reticulum. A Ca2+ wave travels through the oocyte to the opposite side from the entry of the sperm Ca2+ has several effects: Prevents other sperm from entering the oocyte (polyspermy) Activates oocyte to finish meiosis to become a haploid ovum

27 Journey of fertilized egg
Identical twins? 4-5 days 6-7 days

28 Human Chorionic Gonadotropin
During implantation, blastocyst releases hCG hCG keeps the corpus luteum alive to continue releasing estrogen and progesterone. Keeps the endometrium thick and vascular to house the blastocyst; prevents menstruation Secretion of hCG declines by 10th week as placenta takes over hCG production to maintain the pregnancy. hCG antibody is used in early pregnancy test kits.

29 Implantation Trophoblast cells form the chorion Trophoblast will help form placenta, and secretes hCG DAY 6 DAY 9-10 DAY 6 – blastocyst attaches to uterine wall; trophoblast produces enzymes that penetrate wall DAYS 9-10 – blastocyst is completely buried in endometrium; inner cell mass becomes disc

30 Inner cell mass begins to differentiate
1-2 weeks 16 DAYS Inner cell mass begins to differentiate Ectoderm – epidermis and neural tissue Mesoderm – connective tissue and muscle Endoderm – epithelium of lungs and gut

31 Gastrulation: germ layers form
Weeks 2-8 Yolk sac Forms at Week 2 23-13

32 Bird – yolk feeds bird; allantois is for waste
A Comparison of Human with Bird Sacs HUMAN BIRD Bird – yolk feeds bird; allantois is for waste Human – yolk and allantois become umbilical cord

33 Cytotrophoblast forms projections called chorionic villi
1-2 weeks 16 DAYS Formation of placenta: Cytotrophoblast forms projections called chorionic villi Chorionic villi produce the chorion frondosum (next slide)

34 Chorion frondosum = contributes to the placenta

35 Decidual Reaction Decidual reaction = formation of decidua basalis from endometrium Decidua basalis contributes to the placenta; Joins with chorion frondosum to form placenta

36 Circulation of blood in the placenta
Umbilical arteries – send deoxygenated blood from fetus to placenta Oxygenated blood returns to fetus through umbilical vein Maternal blood is also delivered to/from placenta. Maternal and fetal blood do not mix, but are separated by only two cell layers. Molecules diffuse across tissues of the placenta for exchange.

37 Circulation of blood in the placenta
Umbilical arteries – send deoxygenated blood from fetus to placenta Oxygenated blood returns to fetus through umbilical vein Maternal blood is also delivered to/from placenta. Maternal and fetal blood do not mix, but are separated by only two cell layers. Molecules diffuse across tissues of the placenta for exchange.

38 Amniocentesis Samples from the amniotic fluid can help diagnose genetic abnormalities such as Down syndrome. Samples are taken at week 16

39 Chorionic Villi Sampling can be done at 10 – 12 weeks and provides a larger number of fetal cells

40 Pregnancy Averages 38 weeks from fertilization Takes 2 weeks for blastocyst to form Weeks 3 to 8: embryonic period Weeks 9 to birth: fetal period

41 release from pituitary
LABOR Labor is initiated by rising levels of corticotropin-releasing hormone (CRH) from fetus and placenta CRH triggers ACTH release from pituitary ACTH triggers cortisol and DHEAS release from adrenal cortex Cortisol increases the secretion of more cortisol (pos. fdbk)

42 Production of surfactant.
LABOR Cortisol causes Fetal lung maturation Production of surfactant.

43 Stretching triggers release of oxytocin
LABOR Stretching triggers release of oxytocin Cortisol and DHEAS trigger reactions that lead to: increased sensitivity of uterus to oxytocin, prostaglandins, trigger gap junction formation.

44 Male Reproductive System

45 Vasectomy

46 Changes in Blood Flow Cause Erection
Cross section through relaxed penis (a) Normally, smooth muscles encircling the arterioles leading into the penis are contracted, limiting blood flow.

47 Changes in Blood Flow Cause Erection
Cross section through erect penis Sexual stimulation triggers the release of NO from parasympathetic axons into the corpora cavernosua and penile arteries and smooth muscle. NO activates guanylate cyclase, which converts GTP to cGMP, which closes Ca2+ channels. The lowered Ca2+ causes the relaxation of smooth muscles and vessel dilation, leading to erection. (b) During sexual excitement, these muscles relax, and blood flows into spaces within the penis. The swelling penis squeezes off the veins leaving the penis, thereby increasing the pressure produced by fluids within the penis and causing it to become elongated and firm.

48 Nitric Oxide and Erection

49 Semen = Sperm + Secretions
Secretions from epididymis aid sperm maturation Seminal vesicle secretes fructose and prostaglandins Prostate-gland secretions buffer pH in the acidic vagina Bulbourethral gland secretes mucus

50 The Structures Involved in Spermatogenesis
Section of the testis Seminiferous tubules Epididymis Vas deferens Cross section of a seminiferous tubule Sertoli cells: Nourish the developing sperm Spermatogonia Leydig cells Lie between the seminiferous tubules Secrete testosterone (a) A section of the testis, showing the location of the seminiferous tubules, epididymis, and vas deferens. (b) Cross section of a seminiferous tubule. The walls of the seminiferous tubules are lined with Sertoli cells and spermatogonia. As spermatogonia undergo meiosis, the daughter cells move inward, embedded in infoldings of the Sertoli cells. There they differentiate into sperm (spermatazoa), drawing on the Sertoli cells for nourishment. Mature sperm are freed into the central cavity of the tubules for transport to the penis. Testosterone is produced by the interstitial cells in the spaces between tubules.


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