Transcript The Reproductive System

The Reproductive System
The Male Reproductive System
• The male reproductive system
includes two testes, two
epididymides, two vasa
deferenta, the urethra, and
the penis.
• The testes are contained in the
scrotum, where the cooler
temperature allows normal
sperm development.
• Sperm form in the
seminiferous tubules of the
testes. Meiosis reduces the
number of chromosomes in
sperm to 23.
• A mature sperm consists of a
head, which contains the
nucleus and chromosomes; a
midpiece, which contains
mitochondria; and a tail, which
consists of flagellum.
• Sperm take the following path
to exit the body: seminiferous
tubules of the testes 
epididymis vas deferens 
urethra.
• Fluids that are secreted by
various exocrine glands are
mixed with sperm to produce
semen.
Male Reproductive Structures
•bladder- stores urine
•pubis-protects area & supports
muscles
•testis- makes sperm
•vas deferens- carries the sperm
•seminiferous tubules- where
meiosis occurs
•epididymis- where sperm
matures
•seminal vesicle- creates a
solution of sugars
•anus- releases waste
The Formation of Sperm
•Males begin to make sperm during
puberty.
•Two hormones released by the
anterior pituitaries regulate the
function of the testes:
•LH stimulates the secretion of
testosterone, the main male
sex hormone, or androgen,
from cells located between the
seminiferous tubules.
•FSH + testosterone
stimulate
sperm
production in the seminiferous
tubules.
•Sperm are haploid and are
produced by meiosis.
•4 sperm cells result from each
cell that begin meiosis.
•The structure of a mature sperm cell
consists of 3 regions- a head, a
midpiece, and a tail:
•head:
•contains enzymes
•help sperm penetrate
the protective layers
surrounding an egg cell
during fertilization
•contains 23 chromosomes
which will be delivered to the
egg
•midpiece:
• contains mitochondria
•supply the energy that
is required for a sperm
cell to reach an egg
•tail• consists of a single,
powerful flagellum
• used to propel the
sperm
Path of Sperm Through the Body
•The path that sperm
following leaving the
body is: somniferous
tubules  testes 
epididymis  vas
deferens  urethra 
seminal vesicles 
prostate glands 
bulbourethral gland
penis. (see diagram)
The Female Reproductive System
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The female reproductive structures
include two ovaries, two fallopian
tubes, the uterus, the cervix, the
vagina, the two labia, and the
vulva.
Eggs form in the ovaries. Meiosis
reduces the chromosome number
in eggs to 23. Eggs are about
75,000 times larger than sperm.
Starting at puberty, the ovarian and
menstrual cycles occur
approximately every 28 days.
The ovarian cycle consists of three
phases: follicular phase, ovulation,
and luteal phase.
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In follicular phase, FSH causes a
follicle to grow. Estrogen produced
by the follicle causes an egg to
mature and the uterine lining to
build up.
Ovulation occurs midway through
the ovarian cycle, when LH causes
the follicle to rupture and release
its egg.
In the luteal phase, the follicle
becomes a corpus luteum. The
corpus luteum secretes
progesterone, which stimulates
further buildup of the uterine
linning.
Menstruation occurs at the end of
the menstrual cycle, when a corpus
luteum stops secreting hormones.
•ovary- makes eggs
•ovaduct/fallopian
tubes- moves egg
from ovary to uterus
with the use of
contractions and cillia;
where fertilization
occurs
•uterus- where
offspring develops
•cervix- the sphincter that closes the
uterus
•vagina- where the penis enters
•bladder- where urine is stored
•labia- to protect the vagina from the
entry of pathogens
•pubis- protects and supports muscles
•rectum-where waste is released
Formation of Eggs
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A female is born with more that
400,000 eggs in her ovaries which are
immature and cannot be fertilized.
Most females release 300 to 400
mature eggs in their lifetime.
Mature eggs are released about once
every 28 days from puberty until
about age 50.
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Egg formation occurs through
meiosis.
Each mature egg cell is haploid and
contains 23 chromosomes.
Egg formation results in one
functional egg from each cell that
begins meiosis (1 in 4).
Sex hormones stimulate egg
maturation during puberty.
Meiosis II cannot occur in egg cells
until they are fertilized.
An egg is about 75,000 times larger
than sperm and is visible to the
unaided eye.
Preparation for Pregnancy
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Each month the female reproductive
system prepares and releases an
ovum in a series of events called the
ovarian cycle, during which, the egg
matures, enters the fallopian tube,
and fuses with a sperm; if the egg
does not fuse with a sperm it
degenerates and is discarded with
menstruation. During this period the
menstruation cycle also prepares for
possible pregnancy.
An immature egg cell completes it’s
first meiotic division during the
follicular phase in which FSH
stimulates cell division in a follicle,
which provides nutrients for the egg.
Estrogen is also secreted, stimulating
mitotic divisions of cells in the lining
of the uterus.
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The sharp LH level that occurs
midway through the ovarian cycle
causes the follicle to rupture and
release it’s egg which is know as
ovulation.
Following ovulation, an egg
travels through the fallopian tube
where it awaits fertilization on it’s
way to the uterus.
Once ovulation has begun, an egg
must be fertilized within 24 hours
(before the disintegration process
begins).
The luteal phase occurs when the
cells of the ruptured follicle grow
larger and fill the cavity of the
follicle, forming a corpus luteum.
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The corpus luteum secretes progesterone and
estrogen which causes the body to begin
storing nutrients and preparing for possible
pregnancy and decreases the amount of LH
and FSH to prevent other eggs from being
released.
If an egg is fertilized, it attaches to the lining of
the uterus and the chemicals of progesterone
and estrogen are continually released; if the
egg is not fertilized, the release of estrogen
and progesterone stop, the thick lining of the
uterus cannot be maintained and is expelled
through the vagina during menstruation.
Menstruation lasts from 5 to 7 days.
At around age 50, a woman no longer ovulates
due to the maturation, rupturing, or
degeneration of her follicles causing the
menstruation cycle to cease through a process
known as menopause.
Gestation
• Fertilization occurs in the
fallopian tube. Pregnancy begins
when a blastocyst implants itself
in the lining of the uterus.
• The three primary germ layersthe ectoderm, mesoderm, and
endoderm- form early in
embryonic development. Four
membranes- the amnion, yolk
sac, allantois, and chorion- also
form early in embryotic
development.
• Nutrients, gases, and other
substances pass through the
placenta by diffusion from the
mother to the fetus.
• For the first eight weeks of
pregnancy, the developing human
is called an embryo. From the
eighth week until birth, a
developing human is known as a
fetus.
• Unnecessary drug use can
negatively affect an embryo or
fetus.
• During childbirth, contractions of
the uterus initiated by
prostaglandins and oxytocin push
the baby from the mother’s body
through the vagina.
•During fertilization an egg completes
meiosis II (in which the nucleus of the
egg & the nucleus of the sperm fuse)
and form a zygote.
•Fertilization  mitotic division
(cleavage)  help create a ball of cells
(morula) which divide and release fluid
 blastocyst.
•Implantation- when the blastocyst
burrows and imbeds itself into the
lining of the uterus.
•Implantation occurs about a week
after fertilization and begin pregnancy.
•Once sperm are released into the
female body, they swim: vagina 
cervix  uterus  fallopian tubes.
•Sperm may encounter an egg if
ovulation occurs between 72 hours
before and 48 hours after
ejaculation.
•Fertilization = sperm + egg
fuse zygote
•Digestive enzymes from the head
of the sperm break down the egg’s
outer layers & enable the cell
membrane of the egg to fuse with
the cell membrane of the sperm.
•The sperm’ head & midpiece are
the only parts to enter the egg.
•Electrical charges that occur in an
egg’s cell membrane after a sperm
enters the egg help keep other
sperm from penetrating the egg.
Pregnancy
1st Trimester (1-3 months)
•first 2-3 weeks: human embryo resembles
that of other animals
•embryo develops from cells on the inner
part of the blastocyst
•cells reorganize into three distinct type of
cells forming the 3 germ layers: the
ectoderm, mesoderm, & endoderm;
different parts of the body result from
•For the first 8 weeks of pregnancy, the developing human is
each
called an embryo.
•4 development-aiding membranes form •Blood vessels that form in the chorionic villi originate in the
allantois.
•Blood from the mother/fetus never mixes; materials are
•surrounds the embryo (cushions embryo
exchanged across the placenta.
from injury & keeps embryo moist)
•Embryo produces HCG which stimulates the corpus luteum and
•yolk sac- does not contain a yolk; where prevents menstruation.
•amnion-forms fluid filled amniotic
first blood cells originate
•allantois
•chorion-surrounds all other membranes;
forms chorionic villi
•chorionic villi + uterine lining = placenta
•nutrients, gases, pathogens, and other
substances pass to nourish the baby
•attached to baby by umbilical chord
•grow to 2 in.
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Fetal Development (by trimester)
1.
2nd Trimester (3-6 months)
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mother’s uterus enlarges
mother begins to feel movement
grows to 2lbs (34 in.)
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3rd Trimester (6-9 months)
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fetus grow quickly so that it is
prepared to survive outside its mother
fetus develops fat deposits under its
skin
– insulate the body so it can
maintain a steady temperature
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(1-3 months)
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brain/spinal cord/nervous system (3 weeks)
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heart begins to beat (21 days)
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arms/legs/eyes/ears/finger & toes (5 weeks)
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brain activity (5 weeks)
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embryo movement (5 weeks)
(3-6 months)
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audible heartbeat
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skeleton
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layer of soft hair (lanugo)
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begins to wake/sleep
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swallows/sucks thumb/make a
fist/hiccup/kick/curl toes
(6-9 months)
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can see light/dark
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can react to music/loud noise
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develops fat deposits (during 2nd half of 3rd
trimester)
•From 8 weeks until
birth the developing
human is called a
fetus.
Birth
Processes
in order 
(labor)
•occurs at about 270 days (after fertilization)
1.
hormones produced by fetus & mother initiate
birth
2. high levels of estrogen, prostaglandins, &
oxytocin cause the uterus to contract
3. Amniotic sac breaks (a.k.a. “breaking water”)
4. muscles in the cervix & vagina relax enabling
them to enlarge so that the fetus can pass
through them
5. contractions push the fetus through the vagina &
cervix (childbirth)
6. placenta, amnion, & uterine lining are expelled
(afterbirth)
7. baby begins breathing on it’s own
8. umbilical chord is cut & tied
9. umbilical arteries/veins close of (within 30 min
after birth)
10. baby’s respiratory/excretory systems become
fully functional
Key Vocabulary Terms
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afterbirth- the remains of the placenta and the
membranes, which are expelled from the mother’s
body following birth
amniotic sac-a sac formed by the amnion
blastocyst- the modified blastula stage of
mammalian embryos
bulbourethral gland- one of the two glands in the
male reproductive system
cervix- the neck of the uterus
chorionic villius- fingerlike projections of the
chorion that extend into the uterine lining
corpus luteum- the structure that forms from the
ruptured follicle in the ovary after ovulation; it
releases hormones
ejaculation- the expulsion of seminal fluids from the
urethra of the penis during sexual intercourse
embryo- an organism in an early stage of
development of plants and animals; in humans, a
developing individual is referred to as an embryo
from the second through the eighth week of
pregnancy
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epididymis- the long, coiled tube that is on the
surface of a testis and in which sperm mature
fallopian tube- a tube through which eggs move
from the ovary to the uterus
fetus-a developing human during the period from the
eighth week after fertilization until birth
follicle- a small, narrow cavity or sac in an organ or
tissue, such as the ones in the ovaries that contain the
developing eggs
follicular phase- the stage in which an immature egg
completes its first meiotic division
gestation- in mammals, the process of carrying
young from fertilization to birth
human chorionic gonadotropin- a hormone that is
secreted by the placenta and that stimulates
ovulation and secretion of progesterone or
testosterone
implantation- the process by which the newly
fertilized egg in the blastocyst stage embeds itself in
the lining of the uterus
labium- in some animals, one of a pair of lips around
the mouth; also, in some female animals, one of two
pairs of folds of skin and mucous membranes that
cover and protect the openings of the vulva
labor- the process by which the fetus and the
placenta come out of the uterus
…Vocabulary
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luteal phase- the menstrual stage in which the corpus
luteum develops
menopause- the termination of the menstrual cycle,
occurs between the ages of 45 and 55
menstrual cycle- the female reproductive cycle,
characterized by a monthly change in the lining of
the uterus and the discharge of blood
menstruation- the discharge of blood and discarded
tissue from the uterus during the menstrual cycle
ovarian cycle- a series of hormone-induced changes
in which the ovaries prepare and release a mature
ovum each month
ovary- in the female reproductive system of animals,
an organ that produces eggs
ovulation- the release of an ovum from the follicle of
an ovary
ovum- a mature egg cell
penis- the male organ that transfers sperm to the
female reproductive tract during sexual intercourse
and that carries urine out of the body
placenta- the structure that attaches a developing
fetus to the uterus and that enables the exchange of
nutrients, wastes, and gasses between the mother and
the fetus
pregnancy- the period of time between implantation
and birth
prostate gland- a gland in males that contributes to
the seminal fluid
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scrotum- the sac that contains the testes in
most male mammals
semen- the fluid that contains the sperm and
various other secretions produced by the male
reproductive organs
seminal vesicle- one of two glandular
structures in male vertebrates that hold and
secrete seminal fluid
seminiferous tubule- one of many tubules in
the testes where sperm are produced
testis- the primary male reproductive organs,
which produce sperm cells and testosterone
trimester- one of the three equal periods of
about 12 weeks into which the human
gestation period is divided
umbilical cord- the structure that connects an
embryo and then the fetus to the placenta and
through which blood vessels pass
uterus- in female mammals, the hollow,
muscular organ in which a fertilized egg is
embedded and in which the embryo and fetus
develop
vagina- the female reproductive organ that
connects the outside of the body to the uterus
and that receives sperm during reproduction
vas deferens- a duct from which sperm move
from the epididymis to the ejactory duct at the
base of the penis
vulva- the external part of the female
reproductive organs