PowerPoint Summary of Chapters 23-25

1. PowerPoint Summary of Chapters 23-25 • Use this PowerPoint along with the outline notes • If a term appears in bold and is not defined, be sure to go look on the text for it • Refer back to the text for any additional info you would like to have • Have fun!

2. Chapter 23Reproductive System • Meiosis • A form of cell division specific to gametes that results in only half the number of original chromosomes (fig 21-1) • Stem cells (46 chromosomes) divide into functional gametes which only have 23 chromosomes • For males, this process doesn’t start until puberty and continues throughout the rest of their life • Once started, males will produce 500,000 spermatozoa per day.

3. Spermatogenesis – creation of sperm • A single stem cell divides twice to produce four spermatozoa (sperm cell) • This process occurs along the nearly half mile of seminiferous tubules in each testis • The seminiferous tubules drain into the epididymus. There spermatozoa mature up to 2 weeks in the super coiled 23 ft of tubule. • The next part of the pathway is the ductus deferens (vas deferens) that runs from the posterior of each testis to a single ejaculatory duct. • Sperm can be stored in the ductus deferens for several months

4. Spermatogenesis – (cont’d) • Accessory glands add to the seminal fluid at the ejaculatory ducts and proximal end of the urethra. • Seminal Vesicles • Prostate Gland • Bulbourethral (see fig 23-1 for location of these glands) • What are the functions of semen?

5. Spermatogenesis – (cont’d) • The urethra is the final path for seminal fluid as it travels through the penis and is ejaculated out of the body • A typical ejaculate is 2 to 5 ml of semen and contains 50-100 million sperm per ml • Interstitial cells between the seminiferous tubules produce the hormone testosterone. • This production increase dramatically after puberty in the presence of FSH and LH • Refer back to Chapter 12 about the regulation and production of these hormones

7. Oogenesis – formation of an egg (ovum) • Stem cells during prenatal development divide twice to produce an ovum with 23 chromosomes • Each female is born with nearly 2 million ovum, but by the time they will start being released at puberty, the number withers down to ~200,000. All are stored in a pair of ovaries. • Levels of FSH and LH stimulate the development and release • Even so, she will only release less than 400 in a lifetime. One per month, alternating from the right or left ovary. • This process will end with menopause.

8. Oogenesis – formation of an egg (ovum) • One ovum from the left or right ovary is ovulated into the fimbriae of the 5 inch uterine tube • Cilia in the tube draw the ovum towards the uterus; a trip that takes 3-4 days • This cycle usually lasts about 28 days, but can be longer or shorter per individual • Increased LH levels stimulate the development of a follicle, which will then release its ovum in 14days • Fertilization needs to occur in the first 48 hrs after ovulation or the ovum will disintegrate in the uterus and be flushed out during menstration. • If fertilizations does occur, then the cycle is stopped until after birth

10. Read both the menstrual cycle which starts on page 466 • Review fig. 23-13 which summarizes the hormonal events and uterus development for this cycle. • Read the Hot Topic (Box 23-3) and Birth Control Strategies on pages 468 and 469 • Be familiar with the types of cancer of this system • Prostatic, Testicular, Breast, Endometrial, Ovarian, Cervical

11. Chapter 24Development • Begins at fertilization, or conception and ends at birth • Gestation lasts approximately 38 weeks • Prenatal development is divided into two stages • Embryo for the first two months • Fetus from the ninth week to birth

12. Fertilization • Fusion of egg and sperm • Each contain 23 chromosomes to form a zygote containing 46 chromosomes • 200 million sperm are released into the vagina, 10,000 make it into the uterine tube, and about 100 may actually make it to the egg. • Penetration of the egg by a single sperm allows the chromosomes to combine

14. Gestation • Average prenatal period is 38 weeks or 266 days (divided into three trimesters) • First Trimester • 40% of the eggs that are fertilized produce embryos that survive the first trimester • Embryo formation • Zygote undergoes rapid cell divisions called cleavage • By day 5, the cells have entered the uterus, and developed into a blastocyst

15. First Trimester continued • Implantation • About day 7, the blastocyst adheres to the surface of the uterus and will become completely embedded within its membrane • The outer cells of the blastocyst develops into the placenta • The placenta begins secreting human chorionic gonadotropin (hGC) which signals the corpus luteum to maintain production of estrogens and progesterone • This hormone maintains a functional endometrial lining • The inner cell mass of the blastocyst becomes organized into three germ layers that will form different body tissues

16. First Trimester continued • Placenta (fig 24-2) • Extensions from the chorion extend into maternal tissue where chorionic blood vessels develop • These chorionic villi enlarge as the heart starts beating and extend further into the endometrium where they will come in close proximity of maternal blood vessels • The vessels develop into two umbilical arteries and a single umbilical vein • The chorionic villi provide the surface area for the exchange of gasses, nutrients and wastes between maternal and fetal blood flow.

17. First Trimester continued • Placenta (cont’d) • Also releases hormones (progesterone and estrogen) which will take over for the declining corpus luteum • Prevents menstration, prepares mammary glands to produce milk, and prepare the body for delivery • The following slide shows embryos at different stages and an early fetus • Interesting note: Picture b is during a phase where we don’t look too much different from fish or chicken embryo

19. Second and Third Trimester • The framework for the major organ systems have formed by the start of the second trimester • The fetus grows from ~1oz to 1.4lbs • Those organ systems become mostly functional in the third trimester • The fetus gains most its weight and shoots up to an average of 7lbs

20. Changes • The fetus is totally dependant on the mother’s organ systems • That means that the mother has to increase all her norms to provide proper nutrition to the developing fetus • Increase CV activity, blood volume, Respiratory Rate, appetite, and excretion

21. Changes • Early contractions of uterine smooth muscle are weak, short and painless • Late in development rising estrogen levels increase smooth muscle sensitivity and stimulate an rise in oxytocin levels. • Oxytocin increases the force and frequency of contractions in response to a stretch in the uterine cervix • Uterine tissues also produce prostaglandins that increase contractions as well • Typically at 9 months, these changes lead to labor contractions that continue until delivery has been completed.

22. Stages of Labor (Parturition) • First Stage • Cervix dilates and the fetus begins to slide down the cervical canal • Labor contractions are once every 10 to 30 min and at some point the amnion will rupture releasing amniotic fluid (“water break”) • Second Stage • Starts after the cervix has dilated completely and concludes when the fetus emerges from the vagina • Time varies but usually lasts two hours or less

23. Stages of Labor (Parturition) • Third Stage • This stage ends with the ejection of the placenta (“afterbirth”) and an associated blood loss of 500-600ml. • Along with the placenta, the amniotic sac membranes, and the umbilical cord (except the part attached to the baby which forms the umbilicus) are ejected • Fourth Stage • The period the body controls the bleeding after the birth • Involves uterine contractions and repair of an episiotomy, if conducted.

24. Stages of Labor • An episiotomy can be performed to prevent perineal tearing if the vaginal opening is too small • This procedure enlarges the vaginal opening by placing an incision through the perineal musculature between the vagina and anus. It can be repaired with sutures after delivery • A Cesarean (C) section can be performed if complications arise • Here the abdominal wall is opened and a 6-7 inch incision is made in the uterus to allow the head (the widest part) to pass through

25. Multiple Births • New stats on births reveals that twins occur 1 in 100 births and with African-Americans, the rate is greater (1 in 77) • Fraternal twins are created when two eggs are released and fertilized at the same time. May or may not be the same gender. • Identical twins are produced when the fertilized zygote cells split apart during development. The offspring’s genetic makeup is exactly the same. • Fraternal twins are twice as common as identical twins and are increasing with the practice of fertility medicine.

26. Genetics and InheritanceChapter 25 • Genetics is the study of heredity, or how different traits are inherited. • Families have similar traits because they are passed on from generation to generation through their chromosomes

28. Genes and Chromosomes • Chromosomes contain DNA (Chapter 2 if you forgot) • No cell uses every bit of its genetic information • Genes are functional segments of DNA • Every somatic cell carries copies of the 46 original chromosomes that were in the zygote • Except gametes / RBCs figure 2

29. Genotype – Chromosomes and their component genes Phenotype – physical expression of the genotype Arrangement of nucleotide bases – ATGCGCCCCATA or AGCCGCATAGCG… Hair color, skin tone, vision, bone structure Genes and Chromosomes * The genotype dictates the phenotype

30. A gene’s position on a chromosome is called a locus • The locushelps map the DNA strand to indicate which section is responsible for certain traits • Each DNA strand has a “partner” within the nucleus • This pairing is referred to as Homologous Chromosomes, with one strand coming from paternal DNA and the other from maternal DNA

31. Karyotyping • a sample of amniotic fluid is taken (amniocentesis) and fetal DNA is analyzed • aKaryotypedisplays homologous pairs of chromosomes

32. Sampling procedures can be dangerous to the fetus and mother • Amniocentesis is only performed when known risk factors are present • I.e. Family history, age complications, drug user, etc. • Amniotic fluid has to be sufficienct enough to be taken without implication to the fetus • Usually at a gestational age of 14 weeks • Results take several weeks

33. Patterns of inheritance • Somatic cells contain 23 pairs of chromosomes • All 23 are Homologous chromosomes • 22 pair of autosomal and one pair of sex chromosomes

34. Various forms of a gene are called alleles • Homozygous if homologous chromosomes carry the same alleles - AA, or aa • Heterozygous if homologous chromosomes carry different alleles - Aa • Alleles are either dominant • Always expressed in the phenotype • Usually represented by a capital letter (A) • or recessive • Expressed only when both alleles are present • Usually represented by a lowercase letter (a)

35. Incomplete Dominance • Phenotype that is different from phenotypes of homozygous for either allele • Example: Sickle cell • Recessive trait (s) that causes RBCs to fold • ss: individual has the sickle cell disorder • Ss: individual has RBCs that fold only when tissue O2 levels drop

36. Codominance • Heterozygous allele that shows both traits in its phenotype • Example: Blood type • IA: antigen A present • IB: antigen B present • i: no antigen present • ii = Type O • IB IB or IB i = Type B • IA IA or IA i = Type A • IA IB = Type AB

37. Teratogens • factors that disrupt normal development by damaging cells, altering chromosome structure, or by changing the pattern of gene activation and expression. • Examples are nicotine, radiation, and alcohol • Fetal alcohol syndrome (FAS) produces developmental defects caused by mothers who drink during pregnancy • Number 1 cause of mental retardation in the U.S.

38. Punnett square diagram predicts probabilities of traits • A = normal color, a = albino (see next slide)

39. In diagram A, a homozygous dominate male mates with a homozygous recessive female • The probability of them having offspring with normal pigment is 100% (all are heterozygous dominant) • In diagram B, a heterozygous dominant male mates with a homozygous recessive female • The probability that they will have normal pigment offspring is 50%, the other 50% have albinism

40. Inheritance • Simple inheritance • Phenotypic characteristics are determined by interactions between single pair of alleles • Polygenic inheritance • Phenotypic characteristics are determined by interactions among alleles on several genes

42. Inheritance • More than 1200 inherited conditions have been identified that are linked to 1 or 2 abnormal alleles for a single gene

44. Sources of Individual Variation • Genetic recombination • Gene reshuffling, common, creates variations within a gene pool • Crossing over and translocation (fig next slide) • Occurs during meiosis • May produce abnormal chromosomes • The production of chromosomes with extra or missing segments • Most result in miscarriages but some result in developmental disorders

45. Crossover and Translocation

46. Spontaneous mutations • Random errors in DNA replication where extra or missing code occurs • Many of these errors are hidden as the recessive trait, and some don’t make it past the embryo stage • Heterozygous for the abnormal trait would be a carrier

47. Sex-Linked Inheritance • Sex chromosomes are X chromosome and Y chromosome • Male = XY • Female = XX • X chromosome carries X-linked (sex linked) genes • Affect somatic structures • The X chromosome is longer therefore no corresponding alleles on Y chromosome (i.e. no competition for traits)

48. Sex-linked Punnett

49. Human Genome Project • Mapped ~24,000 of our genes • Including some responsible for inherited disorders click for more Human Genome info click for DNA sequence list

50. DNA Map