Exam 3 Anatomy and Physiology Part 2

Male & female reproductive systems are connected sets of organs, including glands Secrete hormones vital to development & maintenance of secondary sex characteristics and regulation of reproductive functions Produce & nurture sex cells (sperm & eggs/oocytes) and transport them to site of fertilization

23 pairs of chromosome Somatic cells – diploid (2n chromosomes = 46) Gametes (sperm & eggs) – haploid (n chromosomes = 23)

Meiosis I – halves chromosome number in each daughter cell Meiosis II – halves chromatid number in each chromosome

1.Synapsis – condensed homologous chromosomes pair along their lengths, aligned locus by locus Crossing over – corresponding segments of DNA molecules are exchanged by non-sister chromatids Homologues remain attached at chiasmata (X-shaped regions formed during crossing over)

1.of homologous chromosomes are arranged on metaphase plate with one chromosome in each pair facing each pole both chromatids of each homologue are attached to microtubules from one pole2.Chromosomes arranged on the metaphase plate Sister chromatids of each chromosome are not genetically identical (due to crossing over)

1.Homologous chromosomes pulled toward opposite poles of the cell2.Sister chromatids pulled apart toward opposite poles of the cell

1.Each daughter cell has a haploid set of replicated chromosomes, each composed of two sister chromatids with non-sister chromatid DNA (due to crossing over)2.Each daughter cell has a haploid set of unreplicated chromosomes, each composed of one chromatid

No replication occurs between meiosis I and meiosis II

Mutations-original Independent assortment of chromosomes Random orientation of homologous pairs of chromosomes in metaphase 2ⁿ possible chromosome combinations in gametes Crossing over Random fertilization

Primary sex organs – 2 testes (the gonads); produce sperm cells & male sex hormones Accessory sex organs – nurture and transport sperm cells Internal – ducts & glands External – scrotum & penis

1-2 months before birth descend to the lower abdominal cavity and pass through inguinal canal (in abdominal wall) into scrotum

is due to stimulation by (male sex hormone) testosterone guided by gubernaculum – a fibromuscular cord Ductus deferens, blood vessels, and nerves form spermatic cord which suspends each testis in scrotum If testes fail to descend into scrotum, they will not produce sperm – t° in abdominal cavity too high

Each enclosed by tunica albuginea – tough, fibrous capsule Subdivided by septa into 250 lobules, each containing 1-4 seminiferous tubules lined with spermatogenic cellsunite posteriorly to form rete testis surrounding interstitial cells join epididymis and becomes ductus deferens

spermatogenic cells- give rise to sperm cells interstitial cells – secrete male sex hormones

At puberty, due to increased testosterone levels new spermatogonia form each diploid primary spermatocyte undergoes meiosis I, giving rise to 2 secondary spermatocytes, which undergo meiosis II, giving rise to 4 haploid spermatids, which mature into sperm cells