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Chapters 46 and 47 Campbell 9th Oviduct Ovary Uterus (Urinary bladder) (Pubic bone) (Rectum) Cervix Vagina Urethra Body Clitoris Glans Prepuce Labia minora Labia majora Major vestibular (Bartholin’s) gland Vaginal opening Ovaries Oviduct Follicles Corpus luteum Uterus Uterine wall Endometrium Cervix Vagina (Urinary bladder) Seminal vesicle (Urinary duct) (Rectum) Vas deferens Ejaculatory duct Prostate gland Bulbourethral gland (Pubic bone) Vas deferens Epididymis Testis Scrotum Erectile tissue Urethra Glans Prepuce Penis Gametogenesis, the production of gametes, differs in male and female, reflecting the distinct structure and function of their gametes Sperm are small and motile and must pass from male to female Eggs are larger and carry out their function within the female © 2011 Pearson Education, Inc. Spermatogenesis, the development of sperm, is continuous and prolific (millions of sperm are produced per day; each sperm takes about 7 weeks to develop Oogenesis, the development of a mature egg, is a prolonged process Immature eggs form in the female embryo but do not complete their development until years or decades later © 2011 Pearson Education, Inc. Spermatogenesis differs from oogenesis in three ways ◦ All four products of meiosis develop into sperm while only one of the four becomes an egg ◦ Spermatogenesis occurs throughout adolescence and adulthood ◦ Sperm are produced continuously without the prolonged interruptions in oogenesis © 2011 Pearson Education, Inc. Epididymis Seminiferous tubule Testis Primordial germ cell in embryo Cross section of seminiferous tubule Mitotic divisions Spermatogonial stem cell 2n Mitotic divisions Sertoli cell nucleus Spermatogonium 2n Mitotic divisions Primary spermatocyte 2n Meiosis I Secondary spermatocyte Lumen of seminiferous tubule Neck Tail Plasma membrane n n Meiosis II Spermatids (two stages) Early spermatid n n n n Differentiation (Sertoli cells provide nutrients) Midpiece Head Acrosome Nucleus Mitochondria Sperm cell n n n n Primordial germ cell in embryo Mitotic divisions 2n Spermatogonial stem cell Mitotic divisions Spermatogonium 2n Mitotic divisions Primary spermatocyte 2n Meiosis I Secondary spermatocyte n n Meiosis II Early spermatid Sperm cell n n n n Differentiation (Sertoli cells provide nutrients) n n n n Primary oocyte within follicle Ovary Primordial germ cell Growing follicle In embryo Mitotic divisions 2n Oogonium Mitotic divisions Primary oocyte (present at birth), arrested in prophase of meiosis I 2n First polar body Completion of meiosis I and onset of meiosis II n n Secondary oocyte, arrested at metaphase of meiosis II Ovulation, sperm entry Mature follicle Ruptured follicle Ovulated secondary oocyte Completion of meiosis II Corpus luteum Second polar n body n Fertilized egg Degenerating corpus luteum Primordial germ cell Mitotic divisions 2n In embryo Oogonium Mitotic divisions Primary oocyte (present at birth), arrested in prophase of meiosis I 2n First polar body Completion of meiosis I and onset of meiosis II n n Secondary oocyte, arrested at metaphase of meiosis II Ovulation, sperm entry Completion of meiosis II Second polar n body n Fertilized egg Stop Here and Do the Handout first Human reproduction is coordinated by hormones from the hypothalamus, anterior pituitary, and gonads Gonadotropin-releasing hormone (GnRH) is secreted by the hypothalamus and directs the release of FSH and LH from the anterior pituitary FSH and LH regulate processes in the gonads and the production of sex hormones © 2011 Pearson Education, Inc. In females, the secretion of hormones and the reproductive events they regulate are cyclic Prior to ovulation, the endometrium thickens with blood vessels in preparation for embryo implantation If an embryo does not implant in the endometrium, the endometrium is shed in a process called menstruation © 2011 Pearson Education, Inc. (a) Control by hypothalamus GnRH 1 Anterior pituitary 2 (b) Inhibited by combination of estradiol and progesterone Hypothalamus FSH Stimulated by high levels of estradiol Inhibited by low levels of estradiol LH Pituitary gonadotropins in blood 6 LH FSH 3 (c) Ovarian cycle 7 Growing follicle Maturing follicle 8 Follicular phase Corpus luteum Ovulation Ovarian hormones in blood Degenerating corpus luteum Luteal phase Estradiol secreted by growing follicle in increasing amounts 4 (d) LH surge triggers ovulation FSH and LH stimulate follicle to grow Progesterone and estradiol secreted by corpus luteum Peak causes LH surge (see 6 ) 5 10 9 Estradiol Progesterone Progesterone and estradiol promote thickening of endometrium Estradiol level very low Uterine (menstrual) cycle (e) Endometrium Days Menstrual flow phase Proliferative phase 0 5 10 14 15 Secretory phase 20 25 28 Hypothalamus GnRH FSH LH Leydig cells Sertoli cells Inhibin Spermatogenesis Testis Testosterone Negative feedback Negative feedback Anterior pituitary During its first 2 to 4 weeks, the embryo obtains nutrients directly from the endometrium Meanwhile, the outer layer of the blastocyst, called the trophoblast, mingles with the endometrium and eventually forms the placenta Blood from the embryo travels to the placenta through arteries of the umbilical cord and returns via the umbilical vein © 2011 Pearson Education, Inc. Maternal arteries Placenta Umbilical cord Maternal veins Maternal portion of placenta Chorionic villus, containing fetal capillaries Fetal portion of placenta (chorion) Maternal blood pool Uterus Fetal arteriole Fetal venule Umbilical cord Umbilical arteries Umbilical vein from ovaries Oxytocin from fetus and mother’s posterior pituitary Activates oxytocin receptors on uterus Stimulates uterus to contract Stimulates placenta to make Prostaglandins Stimulate more contractions of uterus Positive feedback Estradiol Placenta Umbilical cord Uterus Cervix 1 Dilation of the cervix 2 Expulsion: delivery of the infant Uterus Placenta (detaching) Umbilical cord 3 Delivery of the placenta The importance of cell-cell communication. Zygote 2-cell stage forming Gray crescent 0.25 mm 8-cell stage (viewed from the animal pole) 4-cell stage forming 8-cell stage Animal pole 0.25 mm Blastula (at least 128 cells) Vegetal pole Blastula (cross section) Blastocoel Gastrula Morula Blastula Zygote ZYGOTE MORULA SOLID BALL BLASTULA (BLASTOCYST IN MAMMALS) GASTRULA EMBRYO After cleavage, the rate of cell division slows and the normal cell cycle is restored Morphogenesis, the process by which cells occupy their appropriate locations, involves ◦ Gastrulation, the movement of cells from the blastula surface to the interior of the embryo ◦ Organogenesis, the formation of organs © 2011 Pearson Education, Inc. Gastrulation rearranges the cells of a blastula into a three-layered embryo, called a gastrula © 2011 Pearson Education, Inc. The three layers produced by gastrulation are called embryonic germ layers ◦ The ectoderm forms the outer layer ◦ The mesoderm partly fills the space between the endoderm and ectoderm ◦ The endoderm lines the digestive tract Each germ layer contributes to specific structures in the adult animal © 2011 Pearson Education, Inc. ECTODERM (outer layer of embryo) • Epidermis of skin and its derivatives (including sweat glands, hair follicles) • Nervous and sensory systems • Pituitary gland, adrenal medulla • Jaws and teeth • Germ cells MESODERM (middle layer of embryo) • Skeletal and muscular systems • Circulatory and lymphatic systems • Excretory and reproductive systems (except germ cells) • Dermis of skin • Adrenal cortex ENDODERM (inner layer of embryo) • Epithelial lining of digestive tract and associated organs (liver, pancreas) • Epithelial lining of respiratory, excretory, and reproductive tracts and ducts • Thymus, thyroid, and parathyroid glands The four extraembryonic membranes that form around the embryo arise from the amniotic egg ◦ ◦ ◦ ◦ The chorion functions in gas exchange The amnion encloses the amniotic fluid The yolk sac encloses the yolk The allantois disposes of waste products and contributes to gas exchange © 2011 Pearson Education, Inc. During organogenesis, various regions of the germ layers develop into rudimentary organs Early in vertebrate organogenesis, the notochord forms from mesoderm, and the neural plate forms from ectoderm © 2011 Pearson Education, Inc. Eye Neural folds Neural fold Tail bud Neural plate SEM 1 mm Neural fold Somites Neural tube Neural plate Notochord Neural crest cells 1 mm Neural crest cells Coelom Notochord Somite Ectoderm Mesoderm Endoderm Neural crest cells Outer layer of ectoderm Archenteron (a) Neural plate formation Neural tube (b) Neural tube formation Archenteron (digestive cavity) (c) Somites The neural plate soon curves inward, forming the neural tube The neural tube will become the central nervous system (brain and spinal cord) © 2011 Pearson Education, Inc. Neural crest cells develop along the neural tube of vertebrates and form various parts of the embryo (nerves, parts of teeth, skull bones, and so on) Mesoderm lateral to the notochord forms blocks called somites Lateral to the somites, the mesoderm splits to form the coelom (body cavity) © 2011 Pearson Education, Inc. Eye SEM Neural tube Notochord Coelom Somites Tail bud 1 mm Neural crest cells Somite (c) Somites Archenteron (digestive cavity) The embryonic cells in a limb bud respond to positional information indicating location along three axes ◦ Proximal-distal axis ◦ Anterior-posterior axis ◦ Dorsal-ventral axis © 2011 Pearson Education, Inc. 2 Digits Anterior 3 4 Ventral Distal Proximal Dorsal Posterior (b) Wing of chick embryo EXPERIMENT Anterior New ZPA Donor limb bud Host limb bud ZPA Posterior RESULTS 4 What role does the zone of polarizing activity (ZPA) play in limb pattern formation in vertebrates? 3 2 2 4 3 Sonic hedgehog is an inductive signal for limb development Hox genes also play roles during limb pattern formation Read Cell Fate Determination and Pattern Formation 1039-1051 © 2011 Pearson Education, Inc. Ciliary function is essential for proper specification of cell fate in the human embryo Motile cilia play roles in left-right specification Monocilia (nonmotile cilia) play roles in normal kidney development ◦ Almost every cell has one that acts as a transporter and an antenna to receive info from other cells © 2011 Pearson Education, Inc. Lungs Heart Liver Spleen Stomach Large intestine Normal location of internal organs Location in situs inversus Epididymis Seminiferous tubule Testis Primordial germ cell in embryo Cross section of seminiferous tubule Mitotic divisions Spermatogonial stem cell 2n Mitotic divisions Sertoli cell nucleus Spermatogonium 2n Mitotic divisions Primary spermatocyte 2n Meiosis I Secondary spermatocyte Lumen of seminiferous tubule Neck Tail Plasma membrane n n Meiosis II Spermatids (two stages) Early spermatid n n n n Differentiation (Sertoli cells provide nutrients) Midpiece Head Acrosome Nucleus Mitochondria Sperm cell n n n n Primary oocyte within follicle Ovary Primordial germ cell Growing follicle In embryo Mitotic divisions 2n Oogonium Mitotic divisions Primary oocyte (present at birth), arrested in prophase of meiosis I 2n First polar body Completion of meiosis I and onset of meiosis II n n Secondary oocyte, arrested at metaphase of meiosis II Ovulation, sperm entry Mature follicle Ruptured follicle Ovulated secondary oocyte Completion of meiosis II Corpus luteum Second polar n body n Fertilized egg Degenerating corpus luteum