Reproduction I Flashcards
asexual reproduction
- single parent -> 2+ offspring
- identical
- clones
- no meiosis
- no gamete fusion
list the types of asexual reproduction
- budding
- fission
- fragmentation and regeneration
- parthogenesis
what are the advantages to asexual reproduction?
- rapid - many offspring in a short time
- all of organism’s genes passed on
- don’t need to find a mate (great if sessile, low population density)
sexual reproduction
- reproduction involving production and fusion of gametes
- sperm: small, motile, flagellated
- egg (ovum): large, non-motile, contains nutrients for embryo
- involves fertilization: fusion of sperm and egg = zygote (2n)
what are the disadvantages of sexual reproduction
- “reproductive handicap” - only 1/2 of population can actually reproduce
- only 1/2 of organism’s genes passed on
what are the advantages of sexual reproduction
- promotes genetic diversity
- new combinations of alleles
(1) get rid of harmful alleles or combinations of alleles
(2) offspring may be more fit than parents
(3) more likely that some of population can survive environmental changes
what are the functions of the male reproductive system
- make sperm (spermatogenesis)
2. deliver sperm to female reproductive tract
pathway of sperm
Seminiferous tubules Epididymis Vas deferens Ejaculatory duct n(othing)
Urethra
Penis
testes
- male gonads
- endocrine gland
- seminiferous tubules
- ley dig cells
seminiferous tubules
- site of spermatogenesis
- long hollow tube, very small diameter
ley dig cells
- produce testosterone and other sex hormones
- scattered between seminiferous tubules
epididymis
- coiled tube above testes ~ 6m long
- transport sperm - takes ~ 3 weeks
- maturation of sperm
- storage of sperm
scrotum
- skin-covered sac - contains testes and epididymis
- external in most mammals - suspended from body -> cooler than body -> temp improves sperm production and longevity
ducts
- Vas deferens
- extend from scrotum to behind the bladder
- ejaculatory duct
penis
- copulatory organ
- delivers sperm into female reproductive trait
- urethra
Vas deferens
sperm ducts - one from each epididymis
ejaculatory duct
passes through prostate gland, joins urethra
urethra
carries urine and semen through penis
what are the parts to the penis anatomy?
erectile tissue, glans, and prepuce
erectile tissue
3 parallel columns of tissue
during sexual stimulation:
- NO released from endothelial cells
- arterial smooth muscles relax
- dilate arteries/compress veins -> blood enters faster than it leaves
glans
tip of penis, contains most sensory nerves
-homologous with clitoris in females
prepuce (foreskin)
cuff of loose fitting skin, removed in circumcision
semen
sperm and fluids from accessory glands
accessory glands
- secrete fluids into vas deferens
- ~ 60% of semen volume -> fluoresces - forensically important
- produce fluids rich in:
(1) fructose - E for sperm after ejaculation
(2) Prostaglandins - stimulate contractions of uterus - help more sperm up female reproductive tract
prostate gland
- contains anticoagulant enzymes and citrate (nutrient)
- secretes into urethra
- common site of cancer in men > 50
- > 1/2 of men > 40 have enlarged prostate
- ~ 3% of men die of prostate cancer`
bulbourethral gland
- 2 smalls round glands on either side of urethra
- BEFORE ejaculation: secrete bulbourethral fluid into urethra-clear mucus to neutralize only acidic urine (contains some sperm as well - “pulling out” is ineffective)
describe the sperm path
- produced in seminiferous tubules in testes
- travels through/stored in epididymis
- during ejaculation, travels from epididymis through vas deferens
describe the process of spermatogenesis
- Spermatogenesis = production of mature sperm cells, ~ 7 weeks in humans, continuous after puberty
- in embryonic testes (before male is born)
- primordial germ cells divide, differentiate into spermatogonial stem cells
what happens in the mature testes at/after puberty
- spermatogonial stem cells divide via mitosis -> spermatogonia (2n)
- undifferentiated cells in walls of seminiferous tubules
- maintained via mitotic divisions
- some become 1° spermatocytes (~ 3 million/day)
1° spermatocyte (2n)
divides via meiosis
SEQ spermatogenesis
1° Spermatocyte (2n) -> meiosis I -> 2° Spermatocyte (n) -> meiosis II -> spermatids (n) -> differentiation -> mature sperm cells
what are the parts to a mature sperm cell?
head, midpiece, tail
androgens
principle sex hormones in males
testosterone
- needed for spermatogenesis
- growth of primary male sex characteristics - sex organs
- stimulates puberty -> secondary sex characterisitics
(1) physical, behavioral differences between males and females, not directly related to production
(2) facial/body hair, deep voice, muscle development - 10x more testosterone in males than females
Signaling Pathway
- hypothalamus: gonodotropin - releasing hormone (GnRH)
- anterior pituitary: luteinizing hormone or follicle stimulating hormone
- leydig cells: testosterone
- sertolic cells: androgen binding protein and inhibin
follicle stimulating hormone (FSH)
- stimulates development of seminiferous tubules
- stimulates sertoli cells to produce, secrete androgen binding protein (ABP)
- FSH secretion inhibited by inhibin
androgen binding protein (ABP)
- binds testosterone
- helps maintain high testosterone levels in testes
inhibin
peptide hormone secreted by sertoli cells
