Unit 4: Reproduction

sprem cells that are not chosen by the egg are

have their heads cut off

sperm is _____ to the egg

attracted to the egg by chemoattractants that the egg secretes

genotypic sex

sex chromosomes

XX or XY

gonadal sex

having testis vs ovaries

• where gametes are stored

phenotypic sex

if something upstream goes wrong

DSD

differences in in sex development

• ex: being intersex, which can involve having XXX, XYY, or just a single chromosome

• so you can be insensitive to male hormones and have atypical testes or be XX but receive male hormones leading to ambiguous genitalia

mammalian sex determination

SRY protein

a protein that is sex-determining and stimulates production of the H-Y antigen, leading to differentiation of gonads into testes (so male parts)

• so makes the fetus a male fetus (default is for the fetus to become female)

anti-mullerian hormone

aka mullerian-inhibiting factor

• causes degeneration of the mullerian ducts (which create female parts normally)

testesterone

causes the wolffan ducts to become the epididymus, ductus deferens, ejaculatory ducts, seminal vesicles 

• so the internal male parts develop from the wolffan ducts

dihydrotestesterone

DHT

• promotes development of male external anatomy

• so penis, scrotum

what happens if the SRY protein is nonfunctional?

then male tissue will not develop

mullerian ducts when developed cause

development of internal female parts

• oviducts, uterus

absence of testosterone causes ____ in development of a fetus

degeneration of the wolffan ducts, s female external parts develop instead

• clitoris

• labia

what determines the baby’s gender

the sperm since it either adds a X or a Y to the preexisting X

what happens if the fetus lacks the H-Y antigen

the previously undifferentiated gonads will develop into the overies

female is the default

gender

genetic sex is determined by

the chromosomes

• either XX or XY

undifferentiated gonads develop into

ovaries

everyone is ____ at conception

identical

• so has a bipotential stage

• since the cell lacks differentiated sex organs here and doesn’t differentiate until about 7 weeks

if there is a problem with the anti-mullerian hormone, then

you could have both mullerian ducts and wolffan ducts

sex differentiation

if you are “6 weeks pregnant” you have only missed your period for

2 weeks

• so the fetus has only actually existed for 4 weeks

male sex differentiation

• starts if you have an XY chromosome with a functional SRY protein

• so functional SRY protein causes gonads to develop into the testes

• leydig cells: secretes T, causing development of the wolffian ducts, causing development of male external genitalia

• sertoli cells: secretes anti-mullerian hormone, causing regression of mullerian duct, so you don’t develop internal female anatomy

higher T corresponds to higher

sex drive

evolution wants males to have

• large numbers of gametes that are healthy and can live for a bit in the female reproductive tract

sperm is produced in the

testes

sperm need to be at a temp

about 3º C lower than body temp

male anatomy

accessory structures of male anatomy

• prostate

• seminal vesicles

• Bulbouerthral duct

• as help the semen get delivered safl;y to the female party

cremaster muscle

moves the testes closer and farther from the body to regulate theor temp

testes make

sperm

where are the gametes from a male?

in the sperm

there is a spike in ____ after ejaculation in males

vasopressin

• which helps bring the fluid volume back up after you lost some

sperm can live for _____ in the vagina

5 days

• so need nourishment from fructose and vitamins to last until then

vasectomy

vas deferens is clamped or snipped off so sperm cannot enter semen

• so semen has everything else besides the sperm that it would normally have

zinc in semen

has an unknown function, but is possibly associated with fertility

enzymes help the sperm

clot then liquify so it can swim to the egg

peristaltic contractions on semen

helps aid in sperm transport

peristaltic contractions in women help

induce contractions

sperm is developed in the

seminiferous tubules

mucus in sperm is developed

in the bulbourethral glands

water in semen is developed in

all the accessory glands

nutrients for sperm are developed

in

• seminal vesicles

• prostate

• seminal vesicles

• epididymis

enzymes for semen are from

seminal vesicles and the prostate

prostaglandins that induce peristaltic contractions to aid in sperm transport are generated in the

seminal vesicles

testes anatomy

• coiled tubes are the seminiferous tubules, which make sperm

• they then merge into the epididymis, which then merges into the vas deferens

• the seminiferous tubules have both sertoli cells and spermatogonia

urine and semen both exit via

the urethra

the vas deferens merges with

the ejaculatory duct

seminiferous tubule anatomy

• leydigs cells are on the exterior of the tubule: make T

• sertoli cells are in the middle part of the tubule: excrete anti-mullerian hormone

• spermatogonium cells cluster in the tubule and produce new sperm cells

____ close the bladder off during sex

internal urethral spincter

sperm production starts at

puberty

once sperm is in the ____ of the seminiferous tubule, it is ready to go

middle of the tubule

GnRH

gonadotropin releasing hormone

• comes from the hypo

• causes release of LH and FSH

FSH

follicle stimulating hormone

• released from AP

• stimulates the production of sperm within the testicles by acting on Sertoli cells

LH

luteinizing hormone

• released from PP

• causes leydig cells to secrete T

gonadotropic hormones

LH and FSH

FSH is the same

in males and females

inhibin

inhibits FSH release from AP in males, so causes less sperm

ABP

androgen-binding protein

• keeps T in tubules instead of exiting since T is lipid soluble

FSH

promotes development of sperm cells

T comes from ____ and gets released to ____

come from leydig cells and gets released to sertoli cells and to the body for secondary effects

anabolic steroids

• mimic T to help incr muscle mass

• decr the affects that T would normally have, and can cause infertility since sertoli cells are not stimulated and the sperm don’t develop correctly

• also makes the testicles shrink

  • normal testes are egg sized and w steroids are grape sized

male sex act

• thoughts of sex/ visual/physical stimuli trigger IC in brain

• descending sensory pathway stimulates parasympathetic pathway

• para causes penile arterioles to vasodilate, causing an erection

• tactile stimuli in penis cause sensory neuron to trigger IC in spinal cord, which affects brain IC

male sex stimuli comes from

various sources

• thoughts of sex

• physical stimuli in penis

• since IC in spinal cord, a spinal cord injury can impact erection

to promote an erection, you want to stimulate the ____ response and inhibit the ____ response

promote para and inhibit sympathetic

• this is why stress and cardio problems can impede erections and make it hard to maintain them

how alcohol affects erections

• alcohol decr vasopressin, so you get dehydrated and can impede erections

penis anatomy

corpus cavernosum: 2 large parts inside shaft of penis where 90% of blood for the erection is

• aka the body containing cavern

corpus spongiosum: soft spongey thing surrounding urethra and tightens to help ejaculate come out more forcefully

during an erection, you experience ____ which keeps the blood in the penis

veno-occlusion

erections are based mostly on

hydrostatic pressure

• pressure of blood maintained in the penis

3 steps of male sex act

• excitement

• plateau (maintaining erection)

• orgasm/ejaculation (largely involves spinal cord, and during this, sympathetic response takes over)

speed of ejaculate

10-20 mph

parasympathetic control of vasodiation in penis

• parasympathetic stimulation causes NANC (nonadrenergic-noncholinergic nerve cells) cells to release NO

• NO causes guanylate cyclase to product cGMP

• cGMP promotes relaxation of smooth muscles, allowing for vasodilation of penis

• PDE a phosphodieterase converts cGMP back to GTP to maintain vasodilation of the cycle

what happens if the arteries of the penis do not dilate enough?

you have erectile dysfunction

• could occur due to atherosclerosis

NO in women causes

incr blood flow to clitoris

post nut clarity

due to spike in prolactin after ejaculation

____ drops right after ejaculation in men

dopamine

it is easier for ___ to orgasm multiple times in a row because

easier for women

• because their T incr after orgasm, while it decr for men after ejaculation (so they have time to regenerate sperm)

estrogen upregulates the effects of

oxytocin

oxytocin spikes when

women orgasm

viagra

• prolongs the effects of NO by eliminating PDE so CGMP never decomposes to GTP and you can maintain an erection by promoting prolonged vasodilation

• only effects PDE5 and PDE6 a little bit

  • 6 is used in cone cells in retina, so you have slightly blue vision when you take viagra

bipotential tissue turns into either

vulva or penis and scrotum

you rbody has ___ diff PDEs

11

• penis has PDE5 and retina has 6

why would an erection longer than 4 hours become medically emergent?

since the blood has been in your penis for so long that it is super low in oxygen and the penis cells will start to die

• called priapism

female internal reproductive anatomy

most of these parts came from mullerian duct development

ovarian ligament supports

the ovary

the cervix is usually

closed

• except during childbirth

endometrium

the epithelial layer of cells that sloughs off during menstruation

myometrium

muscle in the uterus, does NOT get shed like the endometrium does

menstrual cycle

• follicular phase in ovaries: the follicle develops, stimulated by FSH

• ovulation occurs and an egg is released (lasts 15 min to 1 hr)

• luteal phase in ovaries: corpus luteum produces estrogen, progesterone, inhibin

• menstrual phase in the uterus occurs during the follicular phase of the ovaries

• then proliferative phase builds the endometrium back up

• during secretory phase of the uterus, the endometrium is fully developed with lush lining, ready to support pregnancy

corpus luteum

• develops during the luteal phase of the ovaries, while the endometrium builds back up in the uterus

• causes body temp to incr a bit

• produces estrogen, progesterone, and inhibin

• inhibin inhibits FSH

• this phase lasts about 2 weeks

every cycle, your body develops a new

lush lining

eggs work to be

dominant, and all the other eggs die off

what separates the follicular phase and the luteal phase?

ovulation

why are twins so rare?

since you usually just release 1 egg during your cycle

• but about 40 total follicles develop, just all the eggs don’t survive

LH

luteinizing hormone

• helps release an egg, so spikes before ovulation

development of a follicle steps

• a primary oocyte has just a single layer of granulosa cells (which secrete estrogen)

• as the oocyte develops, the granulosa cells divide, and therefore can produce more and more estrogen

• granulosa cells proliferate and grow into the peripheral cells, which become the thecal cells

• thecal cells on the surface of the oocyte secret androgens, which turn into estrogen later

• this primary oocyte can develop into the dominant follicle

all hormones released in a woman

• hypo sceretes GnRH

• GnRH stimulates secretion of LH and FSH by AP

• LH stimulates thecal cells to produce androgens, which convert to estrogen

• FSH stimulates granulosa cells to convert androgens to estrogens

• estrogen and FSH further stimulate granulosa cell proliferation in the follicle

___% of eggs undergo atresia

99

• so only less than 1% actually becomes the dominant oocyte and all others dies

difference in male vs female gametes

women are born with all the eggs they will ever have but men produce thousands of sperm each day