Copy of Block 2 MicroAna LOs PDF

1. Trace the development from zygote through gastrulation. a. Once the fusion of 2 haploid gametes happens a diploid zygote develops. b. The zygotes then divide by mitosis to create blastomeres, daughter cells. There is no increase in the size of the zygote, this is known as...

1. Trace the development from zygote through gastrulation. a. Once the fusion of 2 haploid gametes happens a diploid zygote develops. b. The zygotes then divide by mitosis to create blastomeres, daughter cells. There is no increase in the size of the zygote, this is known as cleavage. c. The blastomeres will continue to divide until it becomes a morula, once there are 16-32 daughter cells. d. The morula will develop a blastocoele, which is a cavity, and this is known as the blastocyst stage. The blastocoele consists of an inner cell mass surrounded by a trophoblast. e. The inner cell mass forms a bilaminar disc consisting of an epiblast and hypoblast, this establishes the dorsoventral axis. f. Cells from the epiblast migrate to form a primitive streak that establishes the craniocaudal axis. g. With the creation of the primitive streak, 3 germs layers are also created, ectoderm, mesoderm, endoderm. h. The 3 new germs layers are what gives rise to all of the tissues in the body, this is known as gastrulation. 2. Define: male and female pronuclei, cleavage, morula, blastocyst, inner cell mass, epiblast, hypoblast, trophoblast, gastrulation, ectoderm, mesoderm, endoderm, and teratogen. a. Male pronuclei:male gamete after meiosis(1n) b. Female pronuclei: nucleus of the ovum after fertilization but before fusing with sperm c. Cleavage: zygote divides by mitosis many times to create blastomeres( many blastomeres=morula). No increase in cell size d. Morula: 16-32 cells(blastomeres) in the zona pellucida—> what the zygote becomes e. Blastocyst: the cavity that’s created inside the morula (the cavity itself is called a blastocele) f. Inner cell mass(embryoblast): cells that give rise to the embryo g. Trophoblast: outer cells of the blastocyst- gives rise to placenta h. Epiblast: dorsal side of the bilaminar disc created from the embryoblast i. Hypoblast: ventral side of the bilaminar disc created from the embryoblast j. Gastrulation: when the epiblast rotates to create a primitive streak and create a trilaminar disc (ectoderm, mesoderm, endoderm) k. ECTODERM: Epidermal structures (skin), lining of oral, nasal cavity and anus. Nervous system (neuroectoderm - specialized ectoderm). l. MESODERM: Connective tissues, muscle tissue, mesothelium,cardiovascular system, urogenital tract m. ENDODERM: Epithelial lining and glands of digestive and respiratory systems n. Teratogens: any agent, or factor that can cause congenital (present at birth) anomalies in an embryo or fetus. 3. Briefly Explain: pluripotent, totipotent, differentiation and developmental anomaly a. Totipotent - can form any cell of the embryo or placenta b. Pluripotent - can become and cells of the embryo  c. Multipotent - can form cells of organs and different tissues d. Unipotential - can only form ONE cell type e. Differentiation - a complex interaction controlled by gene interactions and cell signalling 4. Give some derivative examples of ectoderm, mesoderm, endoderm. a. Ectoderm - epithelium, nervous tissue b. Mesoderm - connective tissue, muscle, urogenital tract, cardiovascular system c. Endoderm - endothelium, gland of the digestive and respiratory systems 5. List the four divisions of mesoderm based on their position in the embryo. List the derivatives of a somite. a. Axial part - forms the notochord b. Paraxial part - forms somites that differentiate further c. Intermediate part - forms the urogenital system d. Lateral plate - forms somatic and splanchnic mesoderm e. Somite derivatives i. Dermatome - dermis ii. Myotome - muscles iii. Sclerotome - vertebrae and ribs 6. List some common developmental anomalies and teratogens. a. Teratogens - any agent or factor that can cause congenital anomalies in the embryo/fetus. Ex: genetic factors, radiation, chemical agents, infectious agents, hormones b. Teratogen influences on development i. At pre-differentiation stage: Embryo dies  ii. During organogenesis stage: Structural defects (major morphological defects) iii. During fetal growth stage: Affects functional maturation (and minor structural defects) 7. Briefly describe the embryology of the gonads a. Primordial germ cells from yolk sac and allantois migrate to genital ridge via dorsal mesentery → become bipotential gonad b. Bipotential gonad - neither a sperm or ova at this stage c. Default sex for every embryo is female. d. Sertoli cells produce the Anti-Mullerian hormone which inhibits the development of the mullerian duct and then the embryo will develop as a male e. Gonad development: i. Males (XY)- Mesonephric ducts (Wolffian duct). Will form epididymis and ductus deferens ii. Females (XX)- Paramesonephric ducts (Mullerian duct). Will form the uterus, uterine tubes and cervix 8. Trace the steps in gametogenesis, in particular define and compare the features of mitosis and meiosis a. Gametogenesis - production of haploid (1N) gametes (sperm and ovum) b. Mitosis - formation of 2 diploid daughter cells, identical to original cell c. Meiosis - formation of 4 haploid cells, genetic crossover d. Male Gametogenesis i. Spermatogonia divide by mitosis to produce primary spermatocytes ii. Primary spermatocytes divide by meiosis into secondary spermatocytes iii. Secondary spermatocytes and spermatids divide by meiosis again into mature spermatozoa e. Female Gametogenesis i. Females are born with a set number of primordial oocytes  ii. Primordial oocytes divide by mitosis to form primary oocytes and those start meiosis, stops iii. Primary oocytes then start meiosis I, but stops after prophase I iv. Once puberty hits, meiosis I is finished and meiosis II starts, but as a secondary oocyte v. Meiosis II will not be completed until the sperm comes into contact with the secondary oocyte vi. Once Meiosis II is completed a mature ovum can be ovulated and developed into a embryo 9. Identify the differences in the processes of spermatogenesis and oogenesis a. What’s the same? i. Occur in specialized sexually dimorphic organs (testis/ovary) ii. Multiplication of spermatogonia & oogonia by MITOSIS iii. Formation of gametes by MEIOSIS – importance of crossing over and independent assortment for variability = extensive morphological variation (evolution) iv. Incapacity of surviving for very long if fertilization does not occur 10. Relate the steps in gametogenesis to the microanatomy of the male and female reproductive system microanatomy 11. Define the steps in fertilization a. Capacitation i. Occurs in the uterine environment in response to uterine secretions -> spermatozoon hyperactivity b. Acrosome reaction i. Enzymes in the acrosome are released from the sperm to digest the zona pellucida of the oocyte c. Cortical reactions i. The sperm contacts the plasma membrane of the oocyte, cortical granules are released from the oocyte, the zona pellucida acts as a barrier against other sperm