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Lecture 4

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Animal Sciences
ANS 217

Male/Female Repro Systems / head formation 1/29/13 1:01 PM Reproduction • Def: Creating the next generation, making of offspring Avian repro • Sexual reproduction o 2 genders, male and female  Both provide input in the process, almost equal  Value of this? Genetic variation  Asexual reproduction in mammals would result in problems due to no genetic variation o Internal fertilization  Some development occurs inside the reproductive system  External development (after “gastrulation” creation of the mesoderm, pre-gastrulation is just a ball of cells)  Hard shelled egg  Eggs go into a suspended “quiescent” state while they wait for the right temperature • Male repro system o Male possesses 2 testes, both are functional o Situated in center of body cavity, along the back, attached by ligaments, between the lungs and kidneys  Egg development  Primordial streak  Fertile crescent (where germ cells develop, outside the testes or ovaries) o Teste color: creamy yellow/orange o At hatch: 2-4 grams at sexual maturity 25-35 grams o Left one is larger than right ~ 3-5 grams  This way due to early development, females only use the right ovary, so early in life both sexes develop the same for the first week or so o At hatch, rod shaped and size of a grain of rice, at maturity they are bean shaped and thumb sized  Image: Male reproductive system, on BB  In males, the epididymis is curly and close to the ureter, ureter is for uric acid only, epid. For germ cells  When birds reproduce, no penis like mammals, just a papillae and groove to disperse sperm during the “cloacal kiss”  Testis: no discernible structure to the naked eye, all the sperm goes to the rete teste for maturation, then epididymis, then vas deferens o Spermatogenesis (the process)  Occurs in seminiferous tubules (ST)  2 primary cell types in the ST • sertoli cells (nurse cells) o Help the production process • Spermatogonial cells (the source of the sperm cells, basically stem cells) o These cells go though the process and change names as they go form the outside of the tubule inwards towards the lumen o Reproduce by mitosis, constant supply of stem cells o Require 13 to 14 days to differentiate into spermatozoal cells- meiosis, where the cells differentiate o Mitosis, then meiosis: undergo reduction division so the reproductive cells only have half the DNA • Transport of spermatozoal cells o Leave seminiferous tubules to the rete teste, move from epidimus then vas deferens, from rete to vas deferens motility abd fertilization capacity is acquired, movement through is by peristalsis, ejaculation of the cells through the vas deferens into the cloacal cavity, cells are mixed with lymphatic fluid due to no accessory sex glands, transferred to the female oviduct through inversion  Male hormones come from the space between the tubules o Anatomy of an avian sperm cell  Head: pointed vs. round  Contains the acrosome (contains enzymes and substances for chemical reactions) and male pronucleus  Midpiece: contains mitochondria  Tail piece: contains flagella for locomotion o Semen structure  Includes semen and fluid  White creamy white  Thick not watery  96%+ motility when viewed through microscope  Abnormal cells have swollen heads, bent tails  Cell con
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