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2 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Sylvia S. Mader Immagini e concetti della biologia

3 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 C11 - Reproduction and development

4 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Reproduction in animals is varied Both asexual and sexual reproduction occur in among animals. Asexual reproduction (some invertebrates, sponges, cnidarians, flatworms, annelids and echinoderms): single parent give rise to offspring that are identical to the parent.

5 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Reproduction in animals is varied Sexual reproduction (some invertebrates, earthworms, plants and animals): sex cells, or gametes, produced by the parents unite to form a genetically unique individual. Copulation is the sexual union to facilitate the reception of sperm and to protect sperm from drying out.

6 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The male reproductive system The gonads are the organs that make gametes. Testes are male gonads. The human male reproductive system also includes epididymides, vasa deferentia, ejaculatory duct and urethra.

7 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The human reproductive system The penis is the organ of sexual intercourse. The semen is composed of sperm and secretions from the seminal vesicles, prostate gland and bulbourethral glands. Orgasm (sexual climax) is the discharge of accumulated sexual tension resulting from ejaculation of semen and ending in rhythmic muscular contractions in the pelvic region.

8 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Production of sperm Testes contain seminiferous tubules where spermatogenesis occurs. Seminiferous tubules produce: Sperm Interstitial cells

9 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Spermatogenesis Spermatogenesis is the process by which spermatozoon (male sperm cell) are produced through meiosis.

10 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Sex hormones The anterior pituitary secretes hormones that: 1.trigger the spermatogenesis, as the follicle-stimulating hormone (FSH); 2.control the production of testosterone, as the luteinizing hormone (LH). Testosterone is a steroid hormone that influences the sex organ function, sperm maturation and male secondary sex characteristics.

11 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The female reproductive system The female gonads are the ovaries and the reproductive system also includes oviducts, uterus and vagina.

12 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The female reproductive system The clitoris is a sexual organ located near above the opening of the urethra. Unlike the penis, the clitoris is the female's most sensitive sexual organ. The female external genital area also includes the vaginal opening, labia minora and labia majora. Female orgasm culminates in uterine and oviduct contractions.

13 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Production of oocytes The production of an egg occurs as an ovarian follicle (aggregation of cells) changes from primary to secondary to a vesicular follicle.

14 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Production of oocytes Before ovulation, the oocyte maturation requires the oogenesis, a meiotic process whose completion is triggered by the fertilization by a spermatozoon. When the two gamete nuclei melt, the zygote (46 chromosomes) forms.

15 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Female sex hormones Ovaries produce: Estrogen: promotes the development of female secondary sexual characteristics. Progesterone: involved in the menstrual cycle, pregnancy and embryogenesis.

16 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The ovarian cycle The ovarian cycle starts with the production of follicle- stimulating hormone (FSH) in the anterior pituitary. FSH causes maturation of a follicle that secretes estrogen and some progesterone. During the luteal phase, LH promotes development of the corpus luteum.

17 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The uterine cycle The uterine cycle starts with menstruation, the endometrium cleavage occurs and the blood vessels break. During the proliferative phase estrogen causes uterine lining to thicken. Progesterone causes the lining to become secretory.

18 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The ovarian cycle

19 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Sexually transmitted diseases AIDS: disease of the immune system caused by the human immunodeficiency virus (HIV). Herpes Simplex Virus (HSV): transmitted during reactivation phase of the virus. Human Papilloma Virus (HPV): causes infections of the skin or mucous membranes. Other STD are chlamydial infection, syphilis and gonorrhea.

20 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Contraceptives Numerous birth control methods are available before and after sexual intercourse.

21 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Technologies to help fertility Assisted reproductive technologies include: artificial insemination by a donor in vitro fertilization gamete intra-fallopian transfer intra-cytoplasmic sperm injection

22 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Embryonic development The first step of the embryogenesis is the cellular stages. The zygote undergoes rapid mitotic divisions. This cleavage results in a multicellular mass (called morula) and then a single- layered blastula forms.

23 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Embryonic development The second embryogenesis step is the tissue stages. The gastrulation leads to the formation of a three-layered structure called gastrula

24 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Gastrulation A mature gastrula has three germ layers: ectoderm, mesoderm and endoderm.

25 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Gastrulation The three germ layers will develop into specific organs.

26 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Extraembryonic membranes The amnion protects and moisturize the embryo in a sac filled with amniotic fluid. The yolk sac contains the source of food until hatching. The chorion is below the shell and provides gas exchanges with the outside air. The allantois collects metabolic wastes of the embryo.

27 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Embryonic development Embryonic development spans the first two months of the gestation, from fertilization through the acquisition of organ systems.

28 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Embryonic development

29 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Embryonic development Eight weeks after fertilization the embryo is completed and becomes fetus. It has recognizable external features.

30 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Fetal development Fetal development occurs after the third month. Exchanges at the placenta supply the fetus with O 2 and nutrients and collect CO 2 and wastes. During the third and fourth month, the skeleton ossifies and the fetus sex becomes distinguishable. During the fifth, sixth and seventh month fetal movements begins, the fetus continues to grow and gain weight-

31 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Fetal development Nine months after the fertilization, the pregnancy ends with the birth of the newborn.

32 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Childbirth 1.Dilatation: uterine contractions begins. 2.Expulsion: uterine contractions occur every 1-2 minutes. The baby is born and the umbilical cord is cut. 3.Dislodging: uterine muscle contractions shrink the uterus and dislodge the placenta, which is expelled.