L17 Fertilization

when to terminate pregnancy and / or not to invest in offspring?

-resources (current and future)

-chance of future reproduction (age and mating opportunities)

Pregnancy rates highest

ages 20-29

abortion rates highest 

ages 15-19 and ages 35+

Cross cultural reasons for abortion, abandonment, and infanticide 

-poor infant quality (deformed or very ill)

-inadequate parental resources (twins, birth too soon/many, no male support, mother dead, etc)

Safe Haven Baby Boxes

secure, drop-off boxes designed to prevent illegal infant abandonment. typically in fire stations or hospitals

foundlings

an infant that has been abandoned by it’s parents and is discovered and cared for by others 

why choose abandonment?

-unwed and poor mothers 

-middle class (needed to work and couldn’t afford to raise a child)

-similar reasons as abortion / infanticide, but here there’s generlaly a belief that the infant has a chance of survival 

Why choose to neglect an infant?

similar reasons as abandonment, abortion, and infanticide, but different in that 

-more prevalent where abortion, infanticide, and abandonment are not options 

-the parent already has one child 

-the child is the “wrong” sex 

not having safe options for women to terminate pregnancies results in

less safe options, not greater parenting 

Conception

the moment a sperm cell fertilizes and egg cell, marking the beginning of pregnancy

oocyte 

a cell in the ovary which might undergo meiotic division to form an ovum

ovum 

mature egg that is ready for fertilization

ovulation

ovum is released from the ovary in response to high LH levels 

Fallopian tubes 

the tube that an egg travels through after release from the ovary

fimbria

in response to estrogen, fimbria of the fallopian tube sweep the surface of the ovary to draw in the ovary

peritoneal cavity 

sometimes the egg doesn’t get picked up by the fallopian tube and enters this cavity. Typically this means the egg won’t be fertilized or will be reabsorbed. in some cases, it can result in ectopic pregnancy, this is a serious medical condition 

cilia

line the ampulla of the fallopian tubes and create a current of fluid to move the oocyte from the end of the fallopian tube to the center

corona radiata

made up of granulosa cells, and begins to wash away in the fallopian tube to prepare for fertilization

Ejaculate

made up of spermatozoa and seminal plasma; 200-300 million sperm in ejaculate

seminal plasma 

everything in ejaculate separate from sperm; it contains nutrients, alkalizing factors, prostaglandins, and possible viruses

sperm is produced…

in the testes 

after production, sperm travel to and are stored in…

the epididymis, where they mature and become mobile 

from the epididymis, sperm travels through the…

vas deferens

the vas deferens joins with the duct of the seminal vesicles to…

form the ejaculatory duct

the ejaculatory duct passes through the... 

Prostate and Cowper’s gland on the way to the urethra

the ejaculatory duct empties into the urethra, where sperm…

mix with fluids from the prostate gland and seminal vesicles to form semen

vasectomy

the vas deferens are cut and sealed preventing the sperm from traveling from testicles to the urethra 

ejaculate is composed of 

sperm, seminal vesicle fluid, prostate fluid, cowper’s gland fluid

head of sperm 

contains DNA of sperm 

Acrosome of sperm 

contains enzymes to help sperm penetrate the ovum 

how do sperm get into the cervix?

-opening of cervix has cilia to waft sperm through

-components of seminal fluid, stimulate contractions in upper vagina to propel sperm into cervix

-role of female orgasm possible?

cervical mucous 

the fibers line up at ovulation and thin out so sperm can get through, the mucous helps nourish the sperm

sperm in the fallopian tube

the downward current of cilia in ampulla (middle of fallopian tube) helps orient sperm towards the egg

isthmus 

glands here secrete enzymes causing ‘capacitation’ of sperm

Capacitation

stripping of glycoprotein coating from surface of sperm; this changes the sperm into a hyperactivated motility pattern— whip-like beats of the tail

sperm beat their tails causing the ovum to rotate counter-clockwise in order to…

drill through granulosa cells

a single sperm will bind to the outside of the…

zona pellucida (clear membrane inside corona radiata)

one of the proteins of zona pellucida binds to…

molecules on sperm.

acrosome reaction 

when the sperm binds to the zona pellucida and becomes activated; the acrosome membrane fuses with the plasma membrane of sperm, which releases the acrosome’s content

acrosome contains enzymes that are responsible for…

breaking through the egg’s tough coating

perivetelline space

space between the zona and the egg that the sperm enters.

fusion of egg and sperm 

-egg sends out microvilli that engulf sperm head 

-egg’s plasma membrane and sperm fuse

-enzymes released by the egg harden the zona so that other sperm cannot fuse

-final division of oocyte occurs