Reproductive Systems Flashcards
reproductive system functions
- produce gametes
- transport gametes
- maintain gametes
- maintain developing zygote/fetus (F)
- produce sex hormones (M=testosterone; F=estrogen/progesterone)
meiosis
cell division that results in gametes that produce half the number of the parent cell e.g. sperm (haploid) = 23 chromosomes, egg (haploid) = 23 chromosomes, fertilization = 46 chromosomes
diploid
in humans, 46 chromosomes or 23 pairs
haploid
in humans, 23 chromosomes
simplified meiosis
- one parent cell: two sets of duplicated chromosomes
- two daughter cells: one set of duplicated chromosomes
- four gametes: one set of chromosomes
spermatogenesis
- meiosis in male (testes); results in 4 sperm
2. before puberty, diploid; after puberty, haploid
oogenesis
meiosis in female (ovaries); results in 1 ovum due to unequal cytokinesis
interphase I
chromosomes replicate in parent cell, 23 pairs of duplicated chromosomes
meiosis I
reduction division
prophase I
chromosomes shorten/thicken, nuclear envelope disappear, mitotic spindle appears, chromosomes form tetrads (synapsis)
tetrads
homologous pairs arranged together
metaphase I
homologous pairs line up along metaphase plate
karyokinesis
nucleus division
cytokinesis
cytoplasm division
anaphase I
homologous pairs separate; one member of each pair moves to opposite pole; cleavage furrow forms
telophase I
cleavage furrow complete (cytokinesis); 2 daughter cells containing half the chromosome number of parent cell (23 duplicated chromosomes)
meiosis II
equatorial division; results in 4 gametes with 23 chromosomes
testes function
produce sperm and male sex hormones
testes structure
- ovoid structures within scrotum
2. divided into lobules which contain seminiferous tubules and interstitial cells of Leydig
seminiferous tubules
production of sperm cells under the influence of FSH; lined by stratified epithelium (germinal)
interstitial cells of Leydig
production of testosterone under the influence of LH or ICSH
epididymis
- where seminiferous tubules unite on the outer surface of the testes
- tightly coiled tubule leads to vas deferent
- storage of sperm
germinal epithelium
- spermatogenic cells
2. supporting cells
spermatogenic cells
give rise to sperm cells
supporting cells
aka sustentacular, sertoli, or nurse cells which support and nourish spermatogenic cells
scrotum
- pouch of skin and fat that holds testes
2. keeps testes 2 degrees cooler than core temp for viable sperm
male spermatogenesis
- one spermatogonium (23 pairs of chromosomes) duplicates DNA
- one primary spermocyte (23 duplicated pairs of chromosomes) undergoes meiosis I
- two secondary spermatocytes (each with 23 duplicated chromosomes) under meiosis II
- four spermatids (each with 23 chromosomes) mature
- four sperm cells collect in the lumen of seminiferous tubules
- travel to, mature, stored in epididymis
sperm structure
- head: 23 chromosomes covered by acrosome
- body: contains mitochondria needed to produce ATP for energy
- tail: flagellum that provides locomotion
acrosome
contains enzymes to help penetrate oocyte
hormonal control of testes
hypothalamus: GnRH to pituitary
anterior pituitary: secretes FSH, LH
FSH
follicle stimulating hormone stimulates spermatogenesis in germinal epithelium of seminiferous tubules
LH
luteinizing hormone stimulates interstitial cells of Leydig to produce testosterone
testosterone
- begins at puberty
- increased growth of body hair e.g. facial, axillary, inguinal
- vocal cords of larynx lowering pitch
- increased muscular growth
- increased bone strength
- increase in sebaceous gland secretions
vas (ductus) deferens
muscular tube which passes upward from testes, through parietal peritoneum (inguinal canal) into abdominal cavity; site of vasectomy
spermatic cord
vas deferens, testicular vessels, autonomic nerves, lymphatic vessels, cremaster muscle
ejaculatory duct
within prostate gland, fusion between seminal vesicle and vas deferens
seminal vesicle
- sac-like structure attached to vas deferens
- approximately 2/3 volume of semen
- secretes alkaline viscous fluid that contains fructose, for sperm energy, prostaglandins for motility, and clotting proteins (vesiculase) for initial semen coagulation
prostate gland
- surrounds urethra beneath bladder
- secretes milky, acidic fluid which enhances motility
- constitutes 1/4 volume of semen