Reproduction and Egg Laying - Reproduction and Egg Laying...

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Reproduction and Egg Laying Cryptorchidism is a condition in which one or both testicles are absent from the scrotum. In unilateral cryptorchidism, only one testicle is not descended from the inguinal canal, which results in somewhat reduced fertility. In bilateral cryptorchidism, neither testicle is descended from the inguinal canal; this causes a definite decrease in testosterone levels and significantly lowers fertility. The epipdymis has three sections: head, body, and tail. It is a tightly-coiled tube connecting the efferent ducts to the vas deferens. The epididymis functions to store sperm cells, provide maturation space for sperm cells, and also provide nutrients to sperm cells via secreted substances. The vas deferens carries sperm cells and substances from the epididymis to the urethra. Some species have an ampulla, or an enlarged portion, at the end. There are three accessory sex glands in mammalian males: a pair of seminal vesicles, one prostate, and two Cowper’s glands (bulbo-urethras). The seminal vesicles secrete nutrients to nourish the sperm cells. The prostate secretes buffers to maintain an acceptable pH. The Cowper’s glands secrete substances to clean and lubricate the urethra. The size of these glands depends on the amount of semen produced; larger amounts of semen are associated with larger accessory sex glands. The seminiferous tubules of the testes are the site of spermatogenesis. The seminiferous tubules are very long, stretching up to a mile if uncoiled. Interstitial tissue contains the cells of Leydig, which produce testosterone to give male characteristics. Male characteristics include antlers on deer or crested necks of bulls. In a mammalian female, the ovaries are located just back of the kidneys. A mammalian ovary produces estrogen, progesterone, and relaxin; as well as being the site of oogenesis (egg production. An avian ovary is somewhat similar, located near the kidneys. However, in birds, only one ovary will function; and many follicles at varying stages of growth will be present simultaneously. The structures of the oviduct are unique in avian females. The oviduct is defined in five separate sections. The infundibulum is first; the infundibulum is 3”. The infundibulum receives the yolk, secretes the chaliziferous layer, and the vitelline membrane to surround and protect the yolk. The magnum is the second structure of the oviduct. The magnum is 15” long and secretes most of the albumen layers in the egg. The third structure of the oviduct is the isthmus. The isthmus is 4” long and secretes the inner and outer shell membranes. The fourth structure is the shell gland or uterus of the avian oviduct. The shell gland secretes the shell in a process that takes roughly 12 hours.
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The fifth and final section of the oviduct is the vagina. The vagina secretes the substances that eventually become the cuticle of the shell. The vagina also has crypts to catch and store sperm cells. The entire process of egg formation takes 25-26 hours.
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This note was uploaded on 04/01/2008 for the course AN SC 001 taught by Professor Olver,dalehagen,danielr during the Fall '07 term at Pennsylvania State University, University Park.

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Reproduction and Egg Laying - Reproduction and Egg Laying...

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