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Mammal reproduction
characteristics of mammalian reproduction
| Term | Definition |
|---|---|
| Dioecious | each sex must make a gamete: male spermatozoa, female ova produced by primary sex organs (gonads): male testes, female ovaries, also important for hormone production: male testosterone, female progesterone/estrogen |
| Viviparous | bear live-young with the exception of monotremes (oviparous) |
| Male reproductive system | testes, epididymis, ductus (vos) deferans, seminal vesicle, urethra, penis, scrotum |
| positions of testes (variable)- optimal for sperm production | abdominal cavity (monotremes, armadillos, tree sloths), seasonally descended in scrotum (breeding season-many rodents, some bats), permanently descended (primates, carnivores, artiodactyls, perrisodactyls) |
| spermatogenesis | sperm production: seminiferous tubules surrounded by leydig cells (testosterone production) send to epididymis as collection site of sperm to nourish |
| semen | sperm + secretions of epididymis, seminal vesicles, prostate gland, bulbourethral glands (under prostate). Semen nourishes sperm and increases alkilinity to neutralize acidity and lubricates during copulation |
| Penis | copulatory organ often includes baculum: bony structure in penis of carnivores, many primates, rodents, bats. May help maintain stiffness for prolonged copulation (maybe for induced ovulation) |
| Female reproductive system functions | produce ova, receive sperm, nourish young, protect and nourish developing embryo, birth of young |
| Female reproductive system structures | ovaries (ova and certain hormones), oviducts (fallopian tubes), uterus (site of embryonic development), cervix (connects uterus and vagina), vagina (receives penis) |
| Ovaries and ova | 1-2 million follicles with ova, ovulation-release of egg: follicle stimulating horomone- follicle and ovum enlarge, follicle moves to surface, lysis hormone- causes rupture of follicle, ovum passes to oviduct |
| Ovum fertilization | if ovum fertilized the ruptured follicle becomes corpus luteum, produces progesterone which stimulates growth of the uterine lining and mammary gland growth |
| Oviducts | receive mature eggs, site of fertilization, cilia move ovum to uterus |
| Monotreme uterus | urogenital sinus and cloaca, 2 cervices, paired uteri |
| Didelphous uterus | paired uteri, oviducts and vaginal canals, paired cervices |
| Eutherian (4 types) | Duplex 2 uteri &cervices lagomorph, rodent Bipartite 2 uteri, 1 cervix carnivore, cetacean, Bicarnuate most, horns fused distally not proximally insectivore, some bat, artiodactyl, perissodatyl, Simplex no separation horn primate, anteater, pangolin |
| Eutherian placenta functions | anchors embryo, transport nutrients, remove waste metabolites, produce hormones to regulate organs of mom and fetus, suppress mom immune system so not reject fetus |
| Choriovitelline placenta | most marsupials, weak connection (no villi) to uterus- inefficient nutrient/waste exchange, greatly enlarged yolk sac, short gestation, long lactation, altricial young |
| Chorioallantoic placenta | Eutherian & bandicoot, strong connection (villi) results in efficient transfer of nutrients & waste, reduce yolk sac, uterus highly vascularized, long gestation, short lactation, 4 types based on villi distribution |
| Estrus | brief period of receptivity shortly before and after ovulation "heat" monestrous: 1/yr polyestrous: several/yr (rodents) |
| fertilization of most mammals | fertilized within 1st several hours after copulation, fertilized egg implanted in uterus, develop until birth |
| delayed fertilization | usually from food supply, delay in ovulation and fertilization after copulate, common in hibernating northern bats: copulation fall and store sperm until spring |
| delayed development | Very reduced growth rate of embryo following implantation, copulation->fertilization-> slow development |
| delayed implantation | postponement of embedding of blastocyst in uterine epithelium by several day or month, insectivore, rodents, bears, mustelids, seals, armadillos, some bats, roe deer, ovulation->copulation->fertilization->delay->implantation |
| embryonic diapause | period of arrested/slowed development of the embryo at the blastocyst stage, many marsupials including wallabies and kangaroos, ~33 day gestation->pouch to nipple->stays, suckling of 1st joey arrests development of 2nd blastocyst up to 240 days |
| Lactation | birth expulsion placenta, estradiol down, anterior pituitary signal secrete prolactin, milk produced, newborn stimulate nerve receptors in nipples, stimulate hypothalmus, signal posterior pituitary, oxytocin released, alveoli breast milk to milk duct |
| Milk constituents | Fats: 0.2%-61%, Lactose (milk sugar), Protein, various enzymes ward off infections, antibodies (immunities), variation dependency of young, bats and primates ~50% longer lactation than other mammals of similar size |
Created by:
jebeard
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