Co 20 Fig Copyright McGraw-Hill Education. Permission required for reproduction or display Oocyte nucleus Cumulus cells Sperm cell contacting oocyte cell membrane Head of sperm cell Single nucleus The two nuclei fuse to form a single nucleus. Fertilization is complete, and a zygote results. The head of the sperm, carrying the genetic material, enters the oocyte, which completes the second meiotic division. Many sperm cells come in contact with the cumulus cells of the secondary oocyte, but only one sperm cell will penetrate the oocyte's cell membrane. Fig Copyright McGraw-Hill Education. Permission required for reproduction or display. Meiosis XX XY (XX)(XY) Male Sperm cells Oocytes XY 50% female 50% male Female Possible combinations X X XY XX Meiosis Fig Copyright McGraw-Hill Education. Permission required for reproduction or display. Ovulation (a) (b) (c) (d) (e) 4 cells (day 2) 2 cells (day 1) Fertilization Cells that become the embryo proper Blastocyst (day 6) Inner cell mass Blastocele Trophoblast Morula (day 5) Implantation (all): Dr. Yorgus Nikas/Jason Burns/Phototake Fig Copyright McGraw-Hill Education. Permission required for reproduction or display. GnRH LH Menses Pituitary gland Ovary Progesterone Estrogen Developing folliclesOvulation Corpus luteum Degenerating corpus luteum Pituitary gland FSH Hypothalamus Endometrium Uterus Proliferative phase Secretory phase 28 days Fig Copyright McGraw-Hill Education. Permission required for reproduction or display. Lacuna Connecting stalk Chorion Endometrium of uterus Amniotic sac Amniotic cavity Epiblast Hypoblast Yolk sac Blastocele Uterine epithelium Develops from the inner cell mass Embryonic disk Fig Copyright McGraw-Hill Education. Permission required for reproduction or display. Amnion Primitive streak Connecting stalk Caudal (towards the tail) Cells in the surface epiblast move toward the primitive streak and migrate through the streak (blue arrow tails). Cells of the epiblast that migrate through the primitive streak become endodermal and mesodermal cells (red arrows). The mesoderm (pink) lies between the ectoderm (blue) and the endoderm (yellow). Cephalic (towards the head) Embryonic disk Yolk sac Endoderm Mesoderm Ectoderm Notochord Table 20.1 Fig Copyright McGraw-Hill Education. Permission required for reproduction or display. Skin Neural plate Notochord Neural fold Neural groove Crest of the neural fold Neural fold Crest of the neural fold Neural crest cells Neural tube Notochord The neural plate forms from ectoderm. Neural folds form as parallel ridges along the embryo. Neural crest cells begin to form from the crest of the neural folds. The neural folds meet at the midline to form the neural tube, and neural crest cells separate from the neural folds. Fig Copyright McGraw-Hill Education. Permission required for reproduction or display. (a) (b) (c) a-b: Petit Format/NestleScience Source; c: TissuepixScience Source Fig Copyright McGraw-Hill Education. Permission required for reproduction or display. Progesterone Estrogen Progesterone Estrogen hCG Progesterone Estrogen Hormone concentration Progesterone Estrogen hCG Human chorionic gonadotropin (red line) (hCG) increases until it reaches a maximum concentration near the end of the first 3 months of pregnancy and then decreases to a low level thereafter. Progesterone (blue line) continues to increase until it levels off near the end of pregnancy. Early in pregnancy, progesterone is produced by the corpus luteum in the ovary; by the second trimester, production shifts to the placenta. Second trimester Ovary Third trimester Placenta Ovary Placenta Ovary First trimester Placenta Estrogen (green line) increases slowly throughout pregnancy but increases more rapidly as the end of pregnancy approaches. Early in pregnancy, estrogen is produced only in the ovary; by the second trimester, production shifts to the placenta. First trimester (first 3 months) Second trimester (second 3 months) Third trimester (third 3 months) 2 3 Fig Copyright McGraw-Hill Education. Permission required for reproduction or display. Umbilical cord Maternal venule Chorionic villi Umbilical vein Umbilical arteries Separation between maternal and embryonic blood Embryonic blood in capillary Basement membrane Chorion Maternal blood in lacuna Maternal arteriole Endometrium Maternal blood in lacuna Fetal arteriole Fetal venule Placenta (b) (c) (a) Fig Copyright McGraw-Hill Education. Permission required for reproduction or display. Progesterone Estrogen Progesterone Estrogen hCG Progesterone Estrogen Hormone concentration Progesterone Estrogen hCG Human chorionic gonadotropin (red line) (hCG) increases until it reaches a maximum concentration near the end of the first 3 months of pregnancy and then decreases to a low level thereafter. Progesterone (blue line) continues to increase until it levels off near the end of pregnancy. Early in pregnancy, progesterone is produced by the corpus luteum in the ovary; by the second trimester, production shifts to the placenta. Second trimester Ovary Third trimester Placenta Ovary Placenta Ovary First trimester Placenta Estrogen (green line) increases slowly throughout pregnancy but increases more rapidly as the end of pregnancy approaches. Early in pregnancy, estrogen is produced only in the ovary; by the second trimester, production shifts to the placenta. First trimester (first 3 months) Second trimester (second 3 months) Third trimester (third 3 months) 2 3 Fig Copyright McGraw-Hill Education. Permission required for reproduction or display. Placenta Umbilical cord First stage. The cervix dilates, and the amnion ruptures. Ruptured amnion Second stage. The fetus is expelled from the uterus. Uterus Placenta Third stage. The placenta is expelled. Fig Copyright McGraw-Hill Education. Permission required for reproduction or display. In the placenta, the adrenal cortical steroids cause progesterone synthesis to level off and estrogen and prostaglandin synthesis to increase, making the uterus more excitable. Oxytocin causes the uterine smooth muscle to contract Maternal posterior pituitary Maternal hypothalamus Uterine stretch stimulates sensory neurons. Progesterone synthesis levels off. Estrogen and prostaglandin synthesis increases. Placenta Uterine smooth muscle contractions ACTH from fetal pituitary Releasing hormone from fetal hypothalamus Stress Adrenal cortical steroids The fetal hypothalamus secretes a releasing hormone that stimulates adrenocorticotropic hormone (ACTH) secretion from the pituitary. The fetal pituitary secretes ACTH in greater amounts near parturition. ACTH causes the fetal adrenal gland to secrete greater quantities of adrenal cortical steroids. Adrenal cortical steroids travel in the umbilical blood to the placenta. The stretching of the uterus produces action potentials that are transmitted to the brain through ascending pathways. Action potentials stimulate the secretion of oxytocin from the mothers posterior pituitary. Oxytocin Fig Copyright McGraw-Hill Education. Permission required for reproduction or display. Stimulation of the nipple by the babys suckling initiates action potentials in sensory neurons that connect with the hypothalamus Oxytocin Prolactin Spinal cord Mammary gland Posterior pituitary Oxytocin (milk letdown) Prolactin (milk production) Anterior pituitary Hypothalamus In response, the hypothalamus stimulates the posterior pituitary to release oxytocin and the anterior pituitary to release prolactin. Oxytocin stimulates milk release from the breast. Prolactin stimulates additional milk production. Fig a Copyright McGraw-Hill Education. Permission required for reproduction or display. (a) Foramen ovale Pulmonary trunk Ductus arteriosus Aortic arch Superior vena cava Inferior vena cava Liver Ductus venosus Hepatic portal vein Umbilical vein Fetal umbilicus Umbilical cord Umbilical arteries Deoxygenated blood is carried from the fetus to the placenta through the umbilical arteries. Oxygenated blood from the placenta is passed to the fetus by the umbilical vein. Blood bypasses the liver sinusoids by flowing through the ductus venosus. Blood also bypasses the lungs by flowing from the right to the left atrium through the foramen ovale. Blood bypasses the lungs by flowing from the pulmonary trunk through the ductus arteriosus to the aorta. Internal iliac arteries Common iliac artery Kidney Abdominal aorta Fig b Copyright McGraw-Hill Education. Permission required for reproduction or display Superior vena cava Aortic arch Closed ductus arteriosus Pulmonary trunk Fossa ovalis (foramen ovale closed) Inferior vena cava Liver Ligamentum venosum (degenerated ductus venosus) Hepatic portalvein Round ligament of liver (degenerated umbilical vein) Umbilicus Degenerated umbilical arteries Abdominal aorta Kidney Common iliac artery Internal iliac arteries When air enters the lungs, blood is forced through the pulmonary arteries to the lungs. The ductus arteriosus closes (gray). The foramen ovale closes and becomes the fossa ovalis. Blood can no longer flow from the right to the left atrium. The ductus venosus degenerates and becomes the ligamentum venosum (gray). The umbilical arteries and vein are cut. The umbilical vein becomes the round ligament of the liver (gray). The umbilical arteries also degenerate (gray). (b) Fig. 20A Copyright McGraw-Hill Education. Permission required for reproduction or display. Chromosome pairs *Gene responsible for only some cases XY a. Diabetes* b. Osteogenesis imperfecta c. Cystic fibrosis d. Obesity* a. Werner syndrome b. Burkitt lymphoma a. Malignant melanoma b. Friedreich ataxia c. Tuberous sclerosis b. Gyrate atrophy a. Sickle-cell anemia b. Multiple endocrine neoplasia a. Zellweger syndrome b. Phenylketonuria (PKU) a. Breast cancer* b. Retinoblastoma c. Wilson disease a. Alzheimer disease* a. Marfan syndrome b. Tay-Sachs disease a. Polycystic kidney disease b. Crohn disease* a. Tumor suppressor protein b. Breast cancer* c. Osteogenesis imperfecta a. Amyloidosis b. Pancreatic cancer* a. Familial hypercholesterolemia b. Myotonic dystrophy a. Amyotrophic lateral sclerosis* a. DiGeorge syndrome b. Neurofibromatosis, type 2 b. Menkes syndrome X a. Gaucher disease b. Prostate cancer c. Glaucoma d. Alzheimer disease* a. Familial colon cancer* b. Waardenburg syndrome a. Lung cancer b. Retinitis pigmentosa* a. Huntington disease b. Parkinson disease a. Cockayne syndrome c. Asthma a. Spinocerebellar ataxia b. Diabetes* c. Epilepsy* a a a b b b c d a a b d c a a a a a b b b b b c c a a c d c b b c b a a a a a b b b b a b c b a a a a b b a b. Familial polyposis of the colon a. Multiple endocrine neoplasia, type 2 a. Severe combined immunodeficiency a. Duchenne muscular dystrophy c. X-linked severe combined immunodeficiency d. Factor VIII deficiency (hemophilia A)