lecture 14: Reproduction I Flashcards
Asexual reproduction
single parent -> 2+ offspring, identical to parent, clones each other
has no meosis, gamete fusion, or recombination
budding
- grows a little offspring (bud)
- GETS BIGGER
- pinches off
- individual (mitosis)
fission
one organism -> 2 organisms ( aprox. equal size)
fragmentation
cut the organisms into pieces. each piece grows into an adult
parthenogenesis
the queen lays eggs. can be fertilized ( bes, termites, ants)
asexual reproduction advantages
- rapid, many offspring in short time
- dont need to find a mate
sexual reproduction is
reproduction involving production and fusion of gametes = crossing
involves fertilization: fusion of sperm (n) + egg(n) -> zygote (2n)
sperm
small, motile, flagellated
egg (ovum)
large, nonmotile, contains nutrients for embryo ( mitochondria)
what are some disadvantages of sexual reproduction
- reproductive cost -> only 1/2 of population can actually reproduce
- 50% male 50% female - only females can reproduce ( produce offspring)
- asexual- doubles every generation
- sexual - stays the same
advantages of sexual reproduction
- promotes genetic diversity through meiosis
- new combos of alleles through recombination
sexual recombination
- gets rid of harmful alleles or combos of alleles
- offspring may be more fit than parents
- having greater diversity, most likely some population can survive environmental changes
what are the 2 functions of the male reproductive system
- produce sperm ( spermtogenesis)
2. deliver sperm to female reproductive tract
testes
- singular = (testis)
- male gonads ( reproductive organs) - site of gametogenesis
seminferous tubes
- site of spermatogenis
- long hollow tubes, very small diameter ( coiled up back and forth within testes -> increase surface area for production) can do more process
- testes
leydig cells
- produce testosterone, other male sex horomones
- scattered between seminiferous tubules ( floating arounf, surrounding tubules)
- testes
epididymis
- Coiled tube, several functions:
a) Transport sperm - takes about 3 weeks for sperm cell to move through the epididymis once enters
b) Maturation of sperm finishes in epididymis
c) Storage of sperm until its releases
scrotum
Skin covered sac that contains the testes and epididymis
Suspended from the groin so it as a cooling unit (this is because sperm cells cannot develop at body temperature)
penis
- copulatory organ
- delivers sperm into female reproductive tract
- urethra down middle of penis
- excretory system, how you pee
Erectile tissue
3 parallel columns of tissue
glans
tip of penis, contains most sensory nerves
prepuce
foreskin, cuff of loose fitting skin, often removes
penis anatomy
b) During sexual stimulation - NO released → smooth muscle relaxes (than surrounds blood vessels leading into erectile tissue) → more blood flow and fluid retained in tissue
(1) Tissue swells as blood flows in, veins compressed (liquid stays in there)
(2) Blood enters faster than it leaves - hydrostatic skeleton (erect penis)
seminal vesicles produce fluid rich in
- fructose: E for sperm after ejaculation ( need to swim, semen has food source)
- prostaglandins: stimulate contracts of uterus: helps move sperm up the female reproductive tract
seminal vesicles secrete ..
into vas defrans
semen volume has …
60% has yellow pigment, fluoreces under UV light- foresnically important
the prostate gland contains …
a) Contains anticoagulant enzymes (don’t want semen to be thick, prevents sperm from swimming) and citrate (nutrient) have to swim a lot, need food)
prostate glands secrete into
urethra ( surrounds it)
the prostate gland is a common site to what disease
- cancer in men over the age 50
- 1/2 of men over age 40 have enlarges prostate
- 3% of men die form prostate cancer
bulbouretheral glands
- 2 small glands (pair) on either side of urethra
- 1st gland secretes into urethra during sexual arousal ( bulbourethral fluid)
mucus in bulbourethral gland
neutralizes any acidic urine thats in urethra
(1) Acidity would damage or kill sperm
(2) Need to neutral so sperm can be successful
semen
a) Mixture of sperm and fluid from accessory glands
Secretion of 3 glands + Sperm from epididymis = Semen
sperm moves through
- conducting tubes
- mixed with secretions from the 3 accessory glands
sperm paths
testes contains seminiferous tubules, go to epididymis, travels through/stores/ mature in epididymis
vas deferens
- sperm ducts - 1 from each epididymis
- extend from scrotum to pelvic cavity ( all the way around bladder)
ejaculatory duct
- passes through prostate gland, joins urethra
urethra
carries urine and semen out through penis
spermatogenesis
- production of mature sperm cells
- takes - 7 weeks, occurs continuosly in males
embryonic
primordial germ cells divide, differentiate into spermatogonial stem cells ( dont do anything untill puberty )
mature testes
a) Spermatogonia stem cells divide via mitosis
→ Spermatogonia (2n)
(1) Undifferentiated cells in walls of seminiferous tubules
(2) Maintained via mitotic divisions (can stay spermatogonium or specialize →
b) Some become 1° spermatocytes (about 3 million/day) in avg. male
process of sprematogenesis
- 1 degree sprematocyte
- divides via meosis
- meiosis 1 - 2 degree spermatocyte (n) 2 of them
- meisosis 2 - spermatids (n) 4 of them
- each differentiates into mature spem cell
mature sperm cell
head: haploid nucleus , acrosome
midpiece: all the mitochondria ( need alot to swim) , mitochondria from mothers in zygote ( only head fuses)
tail: allows to swim
male endocrinology
hormonal regulation of male reproduction
adrogens
- princible sex hormones in males
- testosterone most important
signaling pathway
Same as thyroid hormone and adrenal cortex
1. Hypothalamus secretes gonadotropin-releasing hormone (GnRH)
→ AP releases 2 gonadotropins (tropic hormones that target gonads) - luteinizing hormone (LH) , follicle stimulating hormone (FSH)
Luternizing hormone ( LH)
- targets leydig cells ( testes, gonads for males)
leydig cells
produce, secrete testosterones, and other androgens
testosterone
(1) High levels in testes required for spermatogenesis to work correctly.
If don’t have enough testosterone → less spermatogenesis
(2) 15-200 million sperm/mL semen - healthy
(3) <15 million/mL - low sperm count (low levels of testosterone)
period of sexual maturation
- adolecent growth spurt
- growth of 1 ° male charecteristics - growth of sex orgrans (penis and tetstes)
- growth of 2° male sex xharecterisitc
what are the 2° sex charecteristics in males
physical, behavorial differencces between males & females not related to reproduction
- facial/body hair, deep voice, muscle development
follicle stimulating hormone (FSH)
- stimulates development of seminiferous tubules
- stimulates sertoli cells 9 found in testes) to produce, secrete androgen binding protiens (ABP)
ABP
(1) Binds testosterone
(2) Helps maintain high testosterone levels (spermatogenesis occur correctly)
(3) Allows testosterone to be sequestered
(4) FSH secretion inhibited by inhibin - peptide hormone secreted by Sertoli cells (inhibits FSH) negative feedback
