Transcript Human Reproduction Notes

Reproduction
a Dr.
Production
• Does a 5 year old boy
have mitotic divisions
occurring?
• Does a 5 year old boy
have meiotic divisions
occurring?
• Does a 5 year old girl
have mitotic divisions
occurring?
• Does a 5 year old girl
have meiotic divisions
occurring?
• Mitosis vs Meiosis
Purpose of Male Reproductive System
• Spermato genesis
• Propel sperm to egg
And now located in a side view of a more complete
male anatomy:
The testes, within the
scrotum, both respond to
and manufacture
hormones. FSH from the
anterior pituitary
stimulates spermatocytes
in the seminiferous
tubules to undergo
meiosis and maturation
to become active sperm.
Testis
• Each testicular lobule
contains several
coiled seminiferous
tubules (ST), site of
sperm production
• Each ST ~ 1.3 ft in
humans. Total length
of ST almost the
length of a football
field
LH from the anterior
pituitary stimulates
interstitial cells,
clusters of cells
wedged in among the
seminiferous tubules,
to produce and
secrete androgens
(male hormones),
particularly
testosterone.
Sperm that are nearly
mature are at the
center (the lumen) of
seminiferous tubules.
They are collected
from individual
tubules into the
epididymus, where
they complete
maturation. Passage
takes about 20 days.
They are pushed from the epididymus into the vas
deferens, which is the duct carrying them to the
rear end of the penis, at the time of ejaculation.
Before entering the penis to be ejaculated, three
other sets of glands contribute fluids to what
will be semen.
The seminal vesicles secrete a fluid (60% of semen)
that contains vitamins and fructose to nourish sperm.
The fluid also contains prostaglandins, hormones that
are believed to cause contractions in the female
reproductive tract to help get sperm to their ‘target’.
The prostate gland
makes an opaque
whitish alkaline
fluid that helps
protect sperm from
any residual urine
in the male tract
and potential
problems with pH
in the female tract.
20% of semen.
• The bulbourethral
glands (called
Cowper’s
gland) secrete a
clear mucous
alkaline
lubricant, which
sometimes
makes up preejaculatory
fluid, 10% of
semen.
Ejaculation is a carefully controlled event.
It occurs in at least two steps:
1) as sexual arousal peaks, muscles in the
epididymus, seminal vesicles, vas deferens, and
prostate all contract. As well, two sphincters
associated with the prostate contract. One blocks
passage of urine into the urethra. The other,
further ‘downstream’, blocks flow of semen.
2) In phase 2 the second sphincter relaxes, and
muscular contractions in the base of the penis
moves the semen through the urethra and ejects
it. Packing semen tightly between the sphincters
then propelling it makes for forceful ejaculation.
The male penis is erectile, and so are the female labia
(majora and minora), clitoris, and, in case you aren’t
aware, also the lips and parts of the nose in both
sexes.
The most densely innervated and sensitive parts in
both males and females are their respective glans and
prepuces.
In males, the prepuce is frequently surgically
removed (called circumcision).
Purpose of Female Reproductive
System
• Oogenesis
• Nurture egg
The ovary is the female gonad. In it oogonia (cells
that will undergo meiosis) are randomly chosen
(usually 1 per month) to undergo meiosis and
develop into mature eggs.
The ovary (about the size of an almond) has a bumpy
surface. Each bump is a follicle, with one oocyte (a
cell undergoing meiosis to become an egg) and a
large number of nurse (follicle) cells. It is the follicle
cells that are stimulated by FSH to produce estrogen.
At ovulation (occurring with the stimulus of LH) the
mature egg bursts from the follicle, and is drawn
into the oviduct (Fallopian tube) by the beating of
cilia in the fringed end of the tube.
Eggs generally are fertilized by sperm in the upper
oviduct, and the zygote goes through a number of
mitotic divisions while it passes down the oviduct,
becoming what is called an embryo.
When the embryo reaches the uterus, it burrows into
the uterine wall and implants. The uterus was
prepared for this by hormones: progesterone and
estrogen from the ovaries.
LH stimulates follicle cells to secrete the progesterone
through the time when a fertilized egg might implant
in the uterus. If a fertilized embryo implants,
progesterone (stimulated by HCG) is secreted
throughout the pregnancy.
Since the ovary and fallopian tube are not joined,
things can go wrong. The egg may not enter the
oviduct. If so, it is broken down by phagocytes.
A fertilized egg may not be drawn properly into or
down the oviduct. If so, it will implant in the oviduct,
or even in the body wall. This is called an ectopic
pregnancy, and has to be fixed by surgery.
.
The Menstrual Cycle
Sex hormones in males are regulated, but do not go
through monthly cycles.
Sex hormones and tissues in females go through
monthly cycles. Those cycles affect the ovaries, the
uterus, and also the mammary glands.
The repeated cycles of cell division in the female
breast milk gland tissue is the probable reason why
female breast cancer is much more common than
cancer of the male breast.
Hormonal Cycle
FSH (pituitary gland) stimulated follicle (in ovary)
Estrogen (ovary) stimulates endometrium (in uterus)
LH (pituitary gland) stimulates follicle rupture
Progesterone (ruptured follicle)stim.endometrium
Follicular (Ovarian) Cycle
Pregnancy – condition of carrying embryo(s) in the uterus;
culminates in birth brought about by strong uterine contractions
Ectopic Pregnancy
• Implantation of blastocyst anywhere other
than within the uterus.
• Causes & Risk Factors:
– Physical blockage of uterine tube.
– Scarring of uterine tube by prior tubal
infection (pelvic inflammatory disease).
– Pregnancy following tubal ligation
reversal or despite oral contraceptive use.
• Symptoms:
– Lower abdominal or pelvic pain.
– Mild cramping on one side of pelvis.
– Abnormal vaginal bleeding (spotting).
The Embryo Takes Shape
Gastrulation
• Preembryo becomes embryo as three
primary germ layers form.
Prembryo
Embryo
Triploblastic
Layers
• Ectoderm
• Mesoderm
– Fetal Skeletons
• Endoderm
Developmental Events-Table 28.2
Feeding the Growing Fetus
The Third Trimester
Fetal Development, US
Forceps
Natural Delivery
Caesarean
Parturition
Stage 1 full cervical dilation
Latent, active, deceleration
Stage 2 delivery of infant
Stage 3  delivery of placenta
Resources
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Human Body Systems: Reproductive System
Human Anatomy Reproduction Animations
NOVA Online “Life’s Greatest Miracle”
Craniopagus parasiticus Video , 2
Male Reproductive Histology
Female Reproductive Histology
The Biology of Sex
Animal Fertilization & Cleavage
A&P Lessons
3D Medical Animations
Fetal Development Timeline
Egg & Sperm Anatomy
Reproductive System Information
Menstrual Cycle Tutorial
ADAM C-Section
C-Section 1
C-Section 2