Transcript Human Reproduction - Salisbury Composite High School

Human Reproduction
Human Reproduction
Human Reproduction
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Male Reproductive Anatomy
Spermatogenesis and Male Hormones
Male Reproductive Technologies and Birth Control
Female Reproductive Anatomy
Oogenesis and Female Hormones
Uterine and Ovarian Cycles
Development of the Fetus
Parturition and Lactation
Teratogens and Birth Defects
Reproductive Technologies
Human Reproduction
Reproduction
• ensures the survival of a species
• Sexual reproduction produces offspring with
new and unique characteristics that may
increase their chance of survival.
Reproduction
• 2 types of gametes (sex cells)
• Males: 1 billion sperm each day from the ages
13-90
• Females: born with 400, 000 eggs, 400 mature
from ages 12 to 50
Reproduction
• The average gestational period for a human is
266 days.
Male Reproductive System
• The male reproductive structures are
responsible for:
 producing sperm
 storing sperm
 delivering sperm
to the female
Male Reproductive System
Male Reproductive System
• Scrotum
– holds the testes away from the body to keep them
cool.
– Sperm production only occurs at temperatures
about 3 degrees below body temperature.
Male Reproductive System
Testis
• descend about 2 months before birth
• spermatogenesis
• seminiferous tubule that produce sperm
Male Reproductive System
• Epididymis – holds sperm for about 2-4
days while they mature
Male Reproductive System
Vas Deferens
• conducts sperm during ejaculation
• vasectomy: the vas deferens cut and tied off, to
prevent conduction of sperm.
Male Reproductive System
• Ejaculatory Duct –propels semen and sperm
through the urethra.
• Urethra –conduction of urine and semen out of
the penis.
– a sphincter muscle closes off the bladder,
preventing urine from exiting the urethra.
Male Reproductive System
Penis
• male organ for copulation. Beneath the skin,
lies the urethra surrounded by spongy
protective tissue that expands to form the glans
penis.
• Prepuce (foreskin) – is a loose sheath of skin
covering the glans penis of uncircumcised
males. The foreskin produces an oily secretion
known as smegma.
Seminal Fluid
Is produced by three different glands:
• Seminal Vesicles
– fluid high in fructose that provides energy sperm
need to swim
– Prostaglandins which cause contractions of muscles
in the female reproductive tract to help move sperm
in
Seminal Fluid
• Prostate Gland
– milky white alkaline fluid that neutralizes the
acidity of the vagina
• Cowper’s Gland
– buffered fluid that cleanses and neutralizes
the acidity in the urethra
Spermatogenesis
• Spermatozoa –
are the smallest
cells in the
body. They
have very little
cytoplasm in
the head, and a
large tail
(flagellum).
Spermatogenesis
• Spermatogonia – undifferentiated germ cells
that have 46 chromosomes
• Primary Spermatocytes – larger cells that
undergo meiosis I
• Secondary spermatocytes – cells that
undergo meiosis II
• Spermatids – cells with 23 chromosomes,
that are ready to mature in the epididymis
• Spermatozoa – mature sperm cells
• Sertoli Cells- nourish sperm cells
Terminology
Erection
• parasympathetic nerve impulses dilate the
arteries of the penis, allowing blood to flow
rapidly into the highly vascular penile tissue
• veins are compressed preventing blood from
leaving the penis.
Terminology
• Ejaculation – occurs when sexual stimulation
forces semen to the urethra, where rhythmical
muscle contractions cause the semen to be
expelled from the penis.
• Infertility – the inability to produce viable
sperm.
• Impotency – the inability to achieve a sustained
erection.
Regulation
of the Male
Reproductive
Hormones
Male Reproductive Hormones
• GnRH : gonadotropic releasing hormone
– released from hypothalamus
– stimulates the anterior pituitary to release LH and
FSH
• LH : luteinizing hormone
– stimulates the interstitial cells (cells in between
seminiferous tubules) of the testes to produce
testosterone
Male Reproductive Hormones
• Testosterone – responsible for male
secondary sex characteristics, required for
sperm production
• FSH: follicle stimulating hormone
– stimulates production of sperm in the
seminiferous tubules
Male Reproductive Hormones
• Inhibin
– produced by Sertoli cells when sperm count is high
– Sends feedback to inhibit FSH and GnRH
Female Reproductive
Structures
• The female reproductive structures are
responsible for
• reception of sperm
• producing an egg
• nourishing and protecting the fetus
• delivering the baby
Female Reproductive Structures
Female External Structures
(Vulva)
• Labia majora – large, fatty, hair covered folds
that protect the genitals
• Labia minora – smaller folds of skin inside the
labia that are kept moist by secretions
• Clitoris – small shaft of erectile tissue
Female Internal Structures
• Vagina
– intercourse : accepts the penis
– birth canal during labor
– pH is generally acidic
Female Internal Structures
• Cervix
– Thick muscular tissue
– plugs closed with mucous during
pregnancy
– prevents material from getting into the
uterus, and holds the baby in
Female Internal Structures
• Uterus (womb)
– pear shaped muscular organ (5 cm wide)
– houses the developing fetus during
pregnancy (30 cm wide)
– strong contractions help push the baby out
during birth
Female Internal Structures
• Ovaries
– produce the ovum from follicles found
in the outer cortex
Female Internal Structures
• Oviducts /Fallopian tubes
– conduction of the ovum (egg) from the
ovaries to the uterus
– where fertilization usually takes place
– If egg implants here = ectopic
pregnancy
frequency
Female Internal Structures
• Fimbriae
– small fingerlike projections at the ends of the
oviducts that sweep to draw the egg into the
fallopian tube
Female Internal Structures
Ovarian Structures
• Follicle
– cells that support and protect the ovum
– secrete estrogen to mature the ovum
– become a corpus luteum following
ovulation.
• Ovum – egg cell, viable for about 24 hours
after release.
Ovarian Structures
• Corpus Luteum
– cells remaining after a follicle has ruptured
during ovulation
– secretes progesterone and some estrogen for
about 3 months if fertilization and
pregnancy occurs
– deteriorates after about 14 days if
fertilization does not occur.
Oogenesis
Regulation of the Female
Reproductive Hormones
• GnRH – stimulates the anterior pituitary to
produce FSH and LH
• FSH – stimulates development of the follicle
and the production of estrogen within the
ovary
Regulation of the Female
Reproductive Hormones
• LH – causes ovulation, development of the
corpus luteum which secretes
progesterone
Reproductive Hormones
• Estrogen
– secreted by the follicles in the ovaries
– causes maturation of the egg
– stimulates growth of the endometrium
(uterus lining)
– Female secondary sex characteristics
– Inhibits FSH
Reproductive Hormones
• Progesterone
– secreted by the corpus luteum
– continues preparation of endometrium
– inhibits both FSH and LH to prevent
ovulation
– prevents uterine contractions
– firms the cervix
P 525 Fig 6
The
Uterine
and
Ovarian
Cycles
Day 1-5: Menstruation/Flow Phase
– Estrogen and progesterone levels are low
– endometrium is sloughed off and shed
Day 1-13: Follicular Phase
– FSH secreted from ant. pit. promotes
development of the follicle
– follicle releases estrogen, which promotes
growth of the endometrium.
Day 14: Ovulation
– An increase in LH causes the ovum to be
released
– FSH is lowered
Day 15 – 28: Luteal Phase
– LH promotes formation of the corpus
luteum
– corpus luteum produces progesterone,
inhibits GnRH, LH and FSH, preventing
subsequent ovulation.
• Many birth control pills are high in
progesterone which prevents ovulation
• cancer
• No Fertilization  corpus luteum degenerates,
estrogen and progesterone levels drop, and
menstruation occurs.
The Uterine Cycle
Menstrualcycle
Fertilization
Fertilization
-union of sperm and secondary oocyte in the
fallopian tube
– Only one spermatozoa will fertilize an egg
– Now called a zygote
– fertilization
Early Embryonic Development
Zygote –fertilized egg, divides by cleavage,
mitosis with no increase in size
• 36 hours: 1st division (2 cells)
– 60hours: 4 cells
– 72h: 8 cells
Morula – solid ball of cells the same size as
the fertilized egg (day4-5)
Early Embryonic Development
Blastocyst
• hollow ball of cells filled with fluid,
• outer layer forms the chorion, inner layer
forms the embryo
• Implants day 7-10
Early Embryonic Development
Implantation
• embryo embeds itself in the endometrium.
• produces HCG (human chorionic
gonadotropic hormone): maintains the corpus
luteum for about 2-3 months.
Reminder: corpus luteum produces progesterone and
estrogen to maintain the endometrium and prevent
ovulation)
• HCG detected in blood or urine with a
pregnancy test
• hCG Pregnancy Test ELISA
Early Embryonic Development
Gastrula
• the blastocyst pushes in (invaginates) and
forms the 3 primary germ layers
• the hollow space forms a primitive gut
• 2nd week
Gastrulation
Germ Layers
Ectoderm – nervous system and epidermis
of the skin
(hair, nails,retina, lens, inner ear, lining of the nose, mouth,
anus and tooth enamel)
Neurula- notochord/neural tube forms from
the ectoderm layer (forms in 3rd to 4th
week)
Germ Layers
Germ Layers
Mesoderm – skeleton, muscles, reproductive
organs
(connective tissue,cartilage, blood, blood vessels,
kidneys)
Endoderm –lining of the digestive and
respiratory system, endocrine glands
(trachea, bronchi, lungs, gallbladder, urethra, liver,
pancreas, thyroid,bladder)
• Gastrulation
• Embryonic development
Embryo at 4 weeks
Extra Embryonic Membranes
• Amnion – inner membrane filled with fluid to
provide protection, maintain temperature,
swallowing
• Chorion-outer membrane, contributes to
placenta
• Extraembryonic coelom – fluid filled space
between amnion and chorion
Extra Embryonic Membranes
• Allantois – collects nitrogenous wastes
and forms the umbilical blood vessels
• Yolk Sac – surrounds embryo, first site of
blood cell formation, becomes part of the
primitive gut
Extra Embryonic Membranes
Placenta
• forms around the fetus
• exchange of gases, delivery of nutrients and
removal of wastes for the fetus
Extra Embryonic
Membranes
• no blood shared between the mother and
the fetus
• Produces progesterone and estrogen at
about 4 months
How Old Are You?
Gestational age
-calculated from the first day of the mother’s last
menstrual period.
–length of pregnancy is 40 weeks
How Old Are You?
Fertilization age –actual age of the fetus
- estimated to be about two weeks after the date of
the last menstrual period.
• To calculate due date: LMP –3 months + 7 days
• calculator
• Weeks 1 -9
Trimesters
• 1rst : until end of third month
• 2nd: 4-6months
• 3rd : 7-9 months
Developmental Milestones
• 1 week – fertilization, cleavage, blastocyst
• 2 weeks – implantation, chorion secretes HCG,
3 germ layers form
Developmental Milestones
• 3 weeks – nervous system is evident, heart
begins to form (2 tubes), heart beats
around day 22
• 4-5 weeks – limb buds appear, eyes, ears
and nose develop, umbilical cord is
attached to placenta
Developmental Milestones
• 6-8 weeks – fetus is recognizable as a human,
all organ system are developed, reflexes begin
(size = 1.5”, 0.5 g)
• 8th week = fetus
• 9-16 weeks – heartbeat is audible with a
stethoscope, bone replaces cartilage,
eyelashes formed, fetus can suck and
swallow (size = 6”, 0.5 lb)
Developmental Milestones
• 17-28 weeks – movement is felt by mother,
eyelids open (size = 12”, 3lb)
– Week 25: premature baby has 50% chance of
survival
Developmental Milestones
• 32 weeks: fetus moves to head down
position and lungs mature
– (good survival rate if born)
Developmental Milestones
• after about 32 weeks significant weight
gain
• 40 weeks: full term (size = 21”, 7.5 lbs)
• See summary chart on page 534
Developmental Milestones
Virtual Development
Conception to Birth
Visible Embryo
Teratogens
• Teratogens - chemical substances or infections
that cause specific birth defects
Teratogens
-Thalidomide-prescribed for morning sickness in the late 50’s
and early 60’s
-rubella during the first 12 weeks of pregnancy: eye problems,
hearing problems and heart damage.
Parturition: Birth
Hormones:
-relaxin: made by placenta, loosens pelvis
ligaments
-prostaglandins – contractions
-oxytocin from Post. Pit - contractions
Parturition
Stage 1 – dilation and effacement(thinning) of the
cervix, mucous plug dislodges, uterine
contractions open the cervix
Stage 2 – delivery of the baby, cervix is dilated to
about 10 cm, intense contractions every 1-2
min push the baby down the birth canal
Stage 3 – delivery of the placenta
Parturition
• The average labor lasts about 12 hours, but can
range from 1 hour to 36 hours.
• caesarean section may be required.
– involves removing the baby from an incision in the
front of the abdomen.
Lactation
• prolactin stimulates the glandular tissue in the
breasts to produce fluids, colostrum, and milk.
• Colostrum is a rich fluid containing mostly
sugar and proteins. This first milk is believed
to play a role in early immunity.
Lactation
• Regular suckling stimulates the pituitary gland
to release oxytocin
– causes weak uterine contractions to return it to its
pre pregnancy shape
– causes “let down” of milk
– 1.5 L of milk each day
Reproductive Technologies
and Health
• Pap Smear – a sample of cervical cells are
taken and examined for abnormal growth
(cancer)
• Ultrasound – uses sound waves to view the
baby in the womb
Ultrasound Scan Fetal Video Clips
Reproductive Technologies
and Health
• Amniocentesis – sampling of the cells from the
amniotic fluid at about 16 weeks to check for
genetic abnormalities
Amniocentesis Flash Animation
Reproductive Technologies
and Health
• Chorionic Villus Sampling – sampling of cells
from the chorion at about 5 weeks to check for
genetic abnormalities
http://www.pbs.org/wgbh/nova/miracle/w
indows.html
Fertility Technologies
• IVF – in vitro (in glass) fertilization –
fertilizing the egg in a petri dish, and
implanting the embryo 2-4 days later
Life Changine Science - Program 3: IVF
• AID – artificial insemination by donor, sperm
is artificially placed in the vagina.
Fertility Technologies
• Egg Screening – testing and selecting eggs to
be fertilized, fertility drugs produce eggs that
are collected using a needle biopsy
• TSE – testicular sperm extraction
– removal of sperm via biopsy (not ejaculation)
• ICSI – intracytoplasmic sperm injection
– sperm head is injected directly into the egg
Fertility Technologies
• GIFT – gamete intra-fallopian transfer
– sperm and egg are transferred to the fallopian tube
for fertilization
• AH – assisted hatching
– a chemical solution is dripped over the egg to
allow the sperm to penetrate more easily
Fertility Technologies
• Embryo Transfer – implantation of an embryo
(at blastocyst stage) into the womb or fallopian
tube, may be frozen or unfrozen
• Fertility Drugs – induce ovulation, usually
many ova are produced at one time, often
results in multiples
Fertility Technologies
Human Reproduction