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BGYB30H3 Lecture 24 Notes Reproduction and Development 4-Dec 1

Biological Sciences
Course Code
Ingrid L.Stefanovic

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BGYB30H3 Lecture 24 Notes
-estrogen causes secondary sex characteristics such as the development of the breasts and fat
distribution in hips and upper thighs
-androgens from the adrenal cortex cause hair growth such as armpit, pubic hair
-four phases of sexual response
-excitement phase involves stimulation of erection reflex in women and men
-excitement phase causes
x Increased blood flow into the penis through corpus cavernosa and corpus spongiosum
x Increased blood flow to the vagina and uterus
x Lubrication of vagina and penis
-plateau is the sexual intercourse
-orgasm is the peak of the plateau phase in which there is ejacuation in men and orgasm in
-orgasm in women is not required for fertilization
-orgasm phase causes contractions in the lower pelvic muscles
-resolution is where body returns back to homeostasis through decreased blood pressure and
respiration rate
-in erection reflex, tactile stimuli activate mechanoreceptors, which send info to spinal cord
-spinal cord inhibits sympathetic nervous system and activates parasympathetic nervous
-stimulating parasympathetic nervous system causes penile arterioles to dilate to increase
blood flow
-erotic stimuli (erogenous zones) and thoughts can cause erection reflex through ascending and
descending pathways to and from the brain; not a reflex mechanism
-REM sleep can cause non-sexual erections and orgasm
-capactiation allows sperm to swim rapidly and fertilize the egg
-when fertilizing the egg, enzymes cause acrosomal reaction by dissolving the outer portions of
the egg casing
-fertilization takes place in the distal portion of the Fallopian tube
-second meiotic division is suspended in the egg until sperm fertilizes the egg
-sperm membrane fuses with oocyte membrane during penetration and the nucleus is released
into the cytoplasm of the egg
-cortical reaction after fertilization prevents penetration of other sperm; prevents polyspermy
-as zygote moves to the uterus, it divides until day 5 when it reaches the uterus as a blastocyst
-chorion of the blastocyst and endometrial cells help it to connect to the endometrium wall
-chorion becomes the placenta; its villi break down blood vessels to bathe the embryo in
maternal blood
-allantois becomes the umbilical cord while amnion secretes fluid
-hCG is secreted from developing chorionic villi and placenta; similar to LH and binds to LH
receptors in the corpus luteum;
-hCG keeps the endometrium intact through secreting progesterone
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