VT106_reproductive - VT 106 Comparative Anatomy and...

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VT 106 Comparative Anatomy and Physiology Reproductive System REPRODUCTIVE SYSTEM Functions of Reproductive System production of offspring – continuation of species genetic recombination – individual variation, adaptation SEXUAL REPRODUCTION gametogenesis – production of gametes (reproductive cells) female – oogenesis produces oocytes (ovum) male – spermatogenesis produces spermatozoa (sperm) copulation – male gametes transmitted to female fertilization – ovum and sperm united gestation – development of offspring from fertilization till birth parturition – giving birth GAMETOGENESIS gonads – site of gamete production female – ovaries male – testes somatic cells – all cells throughout body diploid (2N) – contain pairs of chromosomes (N depends on species) one member of pair from each parent 1 pair of sex chromosomes X chromosome, Y chromosome XX = female XY = male gametes – ovum and sperm haploid (1N) – contain unpaired chromosomes from sire or dam ovum always contains X chromosome sperm – 50% contain X chromosome 50% contain Y chromosome sperm determines sex of offspring zygote – cell produced by fertilization; divides and differentiates into offspring diploid – pairs of chromosomes combined chromosomes from ovum and sperm Mitosis – cell division which produces 2 identical, diploid daughter cells 1
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MEIOSIS – 2 stage cell division which produces 4 haploid gametes occurs in gonads gametes produced are not genetically identical to parent cell Stages of Meiosis: meiosis I – a diploid cell divides and forms 2 haploid cells genetic recombination haploid cells randomly receive 1 chromosome from each chromosome pair crossing-over – random exchange of genes between chromosome pairs meiosis II – the 2 haploid cells divide again, forming 4 haploid cells each is genetically unique due to genetic recombination MALE REPRODUCTIVE SYSTEM TESTES – male gonads site of spermatogenesis – production of spermatozoa produce androgens – masculinizing hormones testes develop in abdominal cavity near kidneys normal sperm production requires a temperature below body temperature Descent of the Testes – testes move out of abdomen and into scrotum scrotum – sac of integument and superficial fascia inguinal canals – tunnels through anterior abdominal wall gubernaculum – connective tissue cord that pulls testis through inguinal canal into scrotum spermatic cord – ductus deferens, blood vessels, and nerves running through inguinal canal to testis Regulation of Testicular Temperature vascular heat exchange mechanism cools testes pampiniform plexus (venous network) cools testicular artery cremaster muscle – skeletal muscle in spermatic cord elevates testes close to body when too cold drops testes away from body when too warm cryptorchidism – one or both testes fail to descend completely animal is sterile – can’t produce normal sperm still produces androgens – normal male appearance and behaviors ANATOMY OF TESTES
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VT106_reproductive - VT 106 Comparative Anatomy and...

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