Reproductive System PDF

Reproductive System DR EMILY WONG Sex organs Testes secrete testosterone ◦ Testosterone: male hormone for development of typical male characteristics (e.g. deep voice) Male hormones are called androgen Ovaries secrete estrogen, progesterone and relaxin ◦ Estrogen: gives a woman female characteristic...

Reproductive System DR EMILY WONG Sex organs Testes secrete testosterone ◦ Testosterone: male hormone for development of typical male characteristics (e.g. deep voice) Male hormones are called androgen Ovaries secrete estrogen, progesterone and relaxin ◦ Estrogen: gives a woman female characteristics ◦ Progesterone: helps prepare the uterus for pregnancy and important in the menstrual cycle ◦ Relaxin: helps enlarge the pelvic opening during childbirth 2 Synthesis of Sex Hormones 3 Controlled by the pituitary ◦ Follicle-stimulating hormone (FSH): cause testes to produce sperm or development of egg ◦ Luteinizing hormone (LH): cause testes to produce testosterone or ovulation (release of egg from the ovary) 4 Gametogenesis 5 Sex Determination Gender is determined by genetic inheritance of two chromosomes known as the sex chromosomes (X and Y). Males possess one X and one Y. Females possess two X. 6 External Sex Differentiation 7 Differentiation of the Gonads During the seventh week of fetal development the SRY gene located on the Y chromosome is expressed, leading to the development of testes in males. 8 Internal Sex Differentiation 9 Stages in the Control of Reproductive Function 10 Male Reproductive Physiology 11 Anatomy 12 Spermatogenesis 13 Spermatogenesis 14 Erection 15 Ejaculation Ejaculation is a spinal reflex mediated by afferent pathways from penile mechanoreceptors leading to contraction of smooth muscle in the epididymis, vas deferens, ejaculatory ducts, prostate, seminal vesicles, and urethra, causing sperm and glandular secretions to be released from the penis. 16 Control of the Testes 17 Testosterone 18 Puberty Puberty, which is the period during which the reproductive organs mature and reproduction becomes possible, usually occurs between 12 and 16 years of age in the male. 19 Andropause Andropause is the steady decrease in testosterone secretion beginning at about 40 years of age. It may include a decrease in libido (desire for sex) and depression. 20 Female Reproductive Anatomy 21 Ovarian Functions Oogenesis Maturation of the oocyte Ovulation Secretion of the female sex steroid hormones 22 Oogenesis 23 24 Tortora. Principles of Anatomy & Physiology. 10th Edn. Fig 28.26 Ovarian Cycle 25 Menstrual cycle The average menstrual cycle is 28 days long Is a 21-35 day cycle in which the female’s ovaries produce an egg and hormonal changes take place that prepare the uterus for pregnancy. When the egg is not fertilized the uterus sheds the lining  menstruation 26 6 Phases Phase 1: ◦ Occurs during the first five days of the cycle ◦ The hypothalamus senses low levels of estrogen and progesterone and signals the pituitary gland to secrete FSH and LH ◦ The ovaries produces larger amounts of estrogen and progesterone, which prepare and release the egg 27 Phase 2: ◦ The hypothalamus detects that the ovaries are secreting the right amount of estrogen for ovulation ◦ Shuts down the pituitary gland’s large production of FSH, and begins producing more LH ◦ Occurs during days 6-12 of the cycle Phase 3: ◦ The estrogen levels reaches a high point, which signals the pituitary gland to release a very large amount of LH, which cause the release of the egg from the ovary ◦ Occurs during days 12-13 of the cycle 28 Phase 4: ◦ Is on 14th day ◦ egg is released and begins its journey down the fallopian tube to the uterus ◦ Left behind with corpus luteum, which produces large amount of progesterone ◦ The progesterone produces the uterine lining ◦ When a sperm fertilize an egg and the woman becomes pregnant 29 Phase 5: ◦ The last two weeks of the 28-day cycle ◦ If fertilization of the egg has not occurred, the pituitary hormones FSH and LH drop ◦ The corpus luteum shrinks, substantially lowering its production of progesterone ◦ The decrease of progesterone causes the breakdown of the lining Phase 6: ◦ The whole cycle begins again on the 28th day 30 31 Follicle Growth 32 Formation of the Corpus Luteum 33 Summary of Hormonal Control of the Ovaries 34 LH Surge and Ovulation 35 The Luteal Phase 36 Uterine Changes in the Menstrual Cycle 37 Other Effects of Estrogen and Progesterone 38 Puberty Puberty, which is the period during which the reproductive organs mature and reproduction becomes possible, generally usually occurs between 10 and 12 years of age in the female. However, there have been reports recently that girls as early as 8 years of age are undergoing puberty. 39 Pregnancy If the egg is fertilized by a sperm on the 14th day of the cycle, the female becomes pregnant The corpus luteum continues to produce progesterone The uterus lining (endometrium) becomes much thicker Ready for implantation (the embryo adheres to the wall of the uterus) 40 Pregnancy Egg Transport Intercourse, Sperm Transport, and Capacitation Fertilization 41 Fertilization 42 Fertilization 43 Migration 44 Early Development, Implantation, and Placentation 45 Formation of the Placenta 46 Development 47 Hormonal and Other Changes During Pregnancy 48 Parturition 49 Parturition 50 Lactation 51 Lactation 52 Melasma Mask of pregnancy Melasma is particularly common in women, especially pregnant women and those who are taking oral or patch contraceptives Is a condition in which the skin develops significant hyperpigmentation Caused by a hormone secreted by the placenta that stimulates the melanocytes in the skin 53 54 Infertility Approximately 12 percent of men and women of reproductive age in the United States are infertile. In many cases, infertility can be successfully treated with drugs, artificial insemination [intrauterine insemination (IUI)], or corrective surgery. When the cause of infertility cannot be treated, it can sometimes be circumvented in women by the technique of in vitro fertilization (IVF). The success rate of this procedure, when one egg is transferred, is only about 15 to 20 percent. 55 Sperm Count 1. Quantity: the number of sperm 2. Morphology: the shape of the sperm 3. Motility: the movement of the sperm (progressive and non-progressive) Menopause Around the age of 50 menstrual cycles become less regular, and ultimately they cease entirely. Menopause and the irregular function leading to it are caused primarily by ovarian failure. The ovaries lose their ability to respond to the gonadotropins, mainly because most, if not all, ovarian follicles and eggs have disappeared by this time through atresia. The hypothalamus and anterior pituitary continue to function relatively normally as demonstrated by the fact that the gonadotropins are secreted in greater amounts. The main reason for this is that the decreased plasma estrogen and inhibin do not exert as much negative feedback on gonadotropin secretion. 57