Biology 240 Exam 1 Tutorial Review

Biology 240 Exam 1 Tutorial Review - Biology 240 Exam 1...

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Biology 240 Exam 1 Tutorial Review Tutorial #2: Early Animal Development I—Gametogenesis and Fertilization The Mammalian Testes -sperm production [ spermatogenesis ] takes place in the  testes -each testis consists of series of convoluted tubes,  seminiferous tubules , which is where sperm  development begins -seminiferous tubules are surrounded by layer of interstitial tissue comprised of blood vessels and  specialized endocrine cells,  Leydig cells , which secrete testosterone; hollow tubes with lumen at  the center and several cell layers around the periphery -cells at the periphery consist of: 1. support cells— Sertoli cells : quite large, provide nutritional and structural support for  developing sperm cells; can also secrete hormone inhibin, which participates in endocrine  control of male reproductive cycles 2. developing sperm cells ( spermatocytes ) which initiate meiosis and give rise to  spermatids which collect in the lumen of seminiferous tubules 3. a pool of undifferentiated cells ( spermatogonia ) -seminiferous tubules lead to another tubular network known as  epididymis  [where final stages  of sperm maturation take place] which then leads to collecting ducts, the  vas deferens , which  carry sperm to the ejaculatory duct during sexual arousal Spermatogenesis -spermatogonia reside in outer regions of seminiferous tubules; at puberty, they begin to divide; cells  termed A1 spermatogonia divide and can remain A1 or become A2 -A2 undergo 2 additional rounds of mitosis giving rise to A3 and A4 -cytokinesis is not complete, resulting in a multinucleated mass of interconnected cells termed a  synctium -sharing of cytoplasm helps the cells to coordinate with one another -A4 begin spermatogenesis, continue proliferating or commit suicide by apoptosis; if spermatogenesis,  they undergo 2 subsequent rounds of mitosis, giving rise to B spermatogonia and  primary  spermatocytes  which enter meiosis, giving rise to 4 haploid spermatids -mature sperm highly specialized for locomotion: compact, well protected, highly motile - spermiogenesis  (maturation process from spermatid to mature sperm) involves dramatic morphological  transformation; spermatids shed cytoplasm, package chromatin, build flagella, and construct  acrosome  for ovum recognition and penetration -spermatogenesis=highly efficient Oogenesis
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- oogenesis  is production of mature ova in ovaries  -similar to spermatogenesis because results in formation of haploid gametes -unlike spermatogenesis, there are at least 3 different strategies of ovum production: 1.  Some produce ova continuously throughout reproductive life (i.e. sea urchins) 2.  Some produce a cohort of ova periodically (i.e. frogs)
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