Download Male Reproductive System

Male Reproductive System
The function of the male reproductive system is to:
 Produce, maintain and transport sperm (gamete) and protective fluid (semen).
 Discharge sperm within the female reproductive tract during sex.
 Produce and secrete male sex hormones responsible for maintaining the male reproductive
system.
MALE Anatomy & Physiology
Testes – Each testis is divided internally into wedge-shaped
lobules. Each lobule contains tightly coiled seminiferous tubules
which are responsible for producing sperm cells. Surrounding
the tubules are interstitial cells that produce testosterone. The
scrotum is a sac of skin that contains the testes, nerves and
blood vessels. Special muscles in the scrotum allow it to
contract and relax, moving the testicles closer to the body and
farther away from the body to regulate temperature. For healthy
sperm development, the testes must be at a temperature
slightly cooler (3o C) than body temperature.
Epididymis – These slightly coiled tubes transport and store sperm cells that are produced in the
testes. The sperm emerge from the testes immature and incapable of fertilization. Immature sperm
travel through the tubes for about 20 days as they mature and gain the ability to swim and fertilize an
egg. During stimulation, the epididymis walls contract to expel sperm into the ductus deferens.
Ductus Deferens or Vas Deferens – The vas deferens is a long, muscular tube that extends from
the epididymis into the pelvic cavity, just behind the bladder. This tube, blood vessels and nerves are
surrounded by a connective tissue sheath called the spermatic cord. The vas deferens transport
mature sperm to the ejaculatory duct which merges with the urethra. The bladder sphincter constricts
to allow semen to travel through the urethra.
Penis – External genitalia designed to deliver
sperm into the female reproductive system.
The penis consists of a shaft, glans penis (tip),
and the prepuce (foreskin). The foreskin can
be surgically removed by circumcision.
Internally, the urethra is surrounded by erectile
tissue, a spongy tissue that fills with blood
during sexual excitement to create an erection.
Seminal Vesicles – This gland attaches to the
vas deferens near the base of the bladder.
These vesicles produce a sugar-rich fluid
(fructose) and other substances which nourish
and activate the sperm passing through the
tract. Sperm and seminal fluid enter the urethra
together during ejaculation. Secretions make
up 60% of the fluid volume of semen.
Prostate Gland – This gland is located below the bladder and produces a milky fluid that plays a role
in activating sperm.
Bulbourethral glands (Cowper’s gland) – This gland is located inferior to the prostate and produces
thick, clear mucus that empties directly into the urethra. This fluid serves to lubricate the urethra and
to neutralize any acidity that may be present due to residual drops of urine in the urethra. This
secretion is the first to pass down the urethra when a man is sexually excited.
Semen – A mixture of sperm and glandular secretions is expelled through the end of the penis when
the man reaches sexual climax (orgasm). The alkalinity of semen (pH 7.2-7.6) helps neutralize the
acidic environment of the female’s vagina, protecting the sperm. In a single ejaculation, there is only
about 2-5 mL of semen and 50 – 150 million sperm in each mL.
Hormones
The follicle-stimulating hormone is necessary for sperm
production (spermatogenesis) and luteinizing hormone
stimulates the production of testosterone, which is also
needed to make sperm. Testosterone is responsible for the
development of male secondary characteristics such as
deepening of the voice, increased hair growth, increase
muscle and bone density.
Spermatogenesis
Sperm production begins at puberty and continues
throughout life. Males produce about 400 million sperm per
day. Stem cells undergo meiosis to produce 4 haploid
spermatids which will mature into functional sperm. The
sperm’s head contains the DNA and an acrosomal
membrane that releases enzymes that helps the sperm
penetrate through the egg.
Female Reproductive System
The function of the female reproductive system is to:
 Produce the eggs necessary for reproduction and transport the eggs to the site of fertilization.
 To be fertilized by sperm & implant the fertilized egg into the uterine walls.
 Produce and secrete sex hormones that maintain the reproductive cycle.
FEMALE Anatomy & Physiology
Ovaries – These small, oval-shaped glands produce eggs and hormones. Internally, ovarian follicles
contain immature eggs called oocytes surrounded by follicle cells. As an egg matures, the follicle
enlarges awaiting ovulation which is the ejection of the egg. After ovulation, the ruptured follicle is
transformed into a corpus luteum which degenerates. The ovaries are supported by a suspensory
ligament to the lateral wall of the pelvis.
Fallopian Tubes – These narrow tubes carry the ova from the ovaries to the uterus. The uterine
tubes expand in fingerlike-projections called fimbriae that partially surround each ovary. During
ovulation, the waving fimbriae create a fluid current to help carry the oocyte into the tube. The journey
to the uterus takes 3 to 4 days and the oocyte is viable for up to 24 hours after ovulation. Fertilization
of the egg by the sperm will occur in the tubes.
Uterus – The uterus functions to receive, retain and
nourish the developing egg. This hollow organ is
divided into two parts: the cervix (opening of uterus)
and the corpus (body of uterus). Both the uterus and
the fallopian tubes are suspended by ligaments. The
uterine wall is composed of three layers: the inner
mucosa called the endometrium, the smooth muscle
called the myometrium, and the outer serosa layer
called the perimetrium (visceral peritoneum). If
fertilization occurs, the fertilized egg burrows into the
endometrium (implantation) and resides for the rest of
its development. When a woman isn’t pregnant, the
endometrial lining shed about every 28 days due to
changing hormone levels.
Vagina – This canal is passageway for the delivery of the infant, for menstrual flow and receives the
penis. The distal end is partially closed by a thin fold of highly vascular mucosa called the hymen.
External Genitalia – The mons pubis is a fatty area overlying the
pubic symphysis. The labia majora are larger folds containing sweat
and oil-secreting glands. At puberty, the mons pubis and labia majora
are covered with hair. The labia minor surround the opening of the
vagina and urethra. These folds protect internal genital organs from
infectious organism. The clitoris is a small sensitive protrusion that
can become erect during stimulation. Bartholin’s glands are located
next to the vaginal opening and produce mucus secretions.
Oogenesis
During fetal development, there are about 7 million
eggs and no new eggs are produced after this time.
At birth, there are one million eggs. The majority of
eggs steadily die until they are depleted at
menopause. The fetal stem cells, oogonia, multiply
rapidly to produce primary oocytes. Primary oocytes
remain in a suspended state until puberty.
 At puberty, about 400,000 oocytes remain and
at this time a small number of oocytes are
activated each month.
 Meiosis I occurs to produce a secondary
oocyte and a polar body. If the secondary
oocyte is penetrated by a sperm, it undergoes
meiosis II to produce another polar body and
the ovum. The ovum combines its 23
chromosomes with the sperms 23
chromosomes. The polar bodies don’t have
enough cytoplasm and die. If fertilization
doesn’t occur, the secondary oocyte
deteriorates without completing meiosis II to
form a functional egg.
Ovarian Cycle
At puberty, females experience hormonal cycles that repeat once a month. With each cycle, a
woman’s body prepares for potential pregnancy regardless. The average cycle takes 28 days and
occurs in 3 phases: follicular phase, ovulatory phase (ovulation), luteal phase. Four hormones
stimulate and regulate the activities: follicle-stimulating hormone, luteinizing hormone, estrogen,
progesterone.
 Follicular phase – Starts on day one of menstruation. FSH and LH are released from the brain
and travel to the ovaries to stimulate the growth of about 15-20 eggs in follicles of the ovaries.
These hormones trigger the production of estrogen. When estrogen levels rise, the production
of FSH stops allowing the body to limit the number of follicles that complete maturation. One
follicle in one ovary becomes dominant, continues to mature and suppresses all the other
follicles and they die. The dominant follicle continues to produce estrogen.
 Ovulatory phase – Starts about day 14. The rise of estrogen triggers a surge of LH which
causes the dominant follicle to release its egg from the ovary. As the egg is released, the
fimbriae sweep the egg into the fallopian tube. An increase of mucus is produced by the cervix
to capture the male’s sperm, nourish it and help it move towards the egg for fertilization.
 Luteal phase – The empty follicle develops into the corpus luteum which secretes
progesterone to prepare the uterus for a fertilized egg to implant. If fertilization occurs, the egg
will implant in the uterus. If no fertilization occurs, the egg passes through the uterus, the
endometrium is shed and the next menstrual period begins.
Embryonic & Fetal Development
Embryonic development begins with the fertilization of the egg in the female’s fallopian
tube. Following fertilization, the egg is now called a zygote. The developing zygote
migrates through the fallopian tubes until it reaches the females uterus and implants
itself in to the endometrial wall approximately 6 days later.
Along its journey the zygote has developed into a hollow ball of cells that is called a
blastocyst. As this blastocyst develops over the next few days its cells will be used to
form not only the embryo but the structures that will nourish and attach it to the mother.
As the cells within the blastocyst continue to grow the process of differentiation begins to occur where cells
start taking on the characteristics of specific types of cells, ie blood, kidney, nerve cells, etc… During this time
of development often called the first “trimester,” the embryo is most susceptible to damage from factors such
as: chemicals, infections, radiation, nutritional deficiencies, etc…
Stage 1: Embryonic Developmental Stages
Body
Circulatory
Digestive
Nervous
Skeletal
Muscular
Urinary, Reproductive,
Respiratory, Skin
0-8 Weeks

head nearly as large as the body ….. 1.2 inches, 2 grams (0.06 oz)

limbs are present, digits are webbed @ first but free by 8 weeks
fully functional & heart pumps blood starting at week 4
liver is disproportionately large and forms RBC’s
all brain regions are present
ossification just begins @ the end of 8 weeks
weak spontaneous muscle contractions
*Are all present but in a very rudimentary form
Stage 2: Fetal Development
While all the body systems begin to develop in embryonic dev. over the next 32 weeks, they will continue to differentiate and
mature.
Weeks 9-12
Weeks 13-16
Weeks 17-20
Body
head is ½ size of the body
Limbs & torso grow so the body is

Limbs reached final proportions
more proportional in size.

assumes the “Fetal” Position
Circulatory

Erythropoesis begins in the liver
Fetus’s heart beat can be detected
& proceeds to the bone marrow
with a stethoscope

Heart continues to develop.
Skin

All layers are formed
Lanugo “fine hair” develops on the

Lanugo (hair) & Vernix Caseosa

Glands are forming
head
(fatty secretions of sebaceous
glands) cover the body

Eyelashes/eyebrows appear
Digestive

GI Tract is Formed

Glands develop in GI Tract

Tooth Buds form

Pancreas & liver release
secretions

Meconium is developing
Nervous

Brain & Spinal cord develops

Cerebellum is prominent

Retina Forms & Eyelids will shut

Sensory organs differentiate
until about 28 weeks

Eyes & ears in correct
position & shape
Skeletal
Ossification of the spine and limbs
Bones & joints are forming
Ossification continues
Muscular
Make a fist
Eyes Blink and Sucks thumb
“Quickening” - feel the baby move
Urinary
Structures present but
Kidneys attain their typical shape
unrecognizable
Reproductive Recognizable at the end of 12 weeks
Respiratory
Cells are present and organize into lungs however the most immature of all the systems
21-30
Body
Circulatory
Skin
Digestive
31-40
19-21 inches & 6-10 lbs
15-16 inches & 3-3½ lbs
Skeletal
Fingerprints and footprints are forming “dermal papillae”

GI Tract is formed & fetus swallows amniotic fluid

teeth enamel forms

Eyes have completely formed & Rapid brain
development

Hypothalamus immature to control body temp
Erythropoiesis only in the marrow
Muscular
reflexes are present & open and closes eyes
Urinary
Reproductive
Respiratory
Kidneys begin to filter blood
in month 7 testes move to the scrotum

Alveoli begin to develop

If born premature limited gas exchange would be
possible; however surfactant is not usually produced
until at least week 27/28.
Nervous
Skin is pinkish & melanocytes may begin to activate
Completely formed & ready for milk
Completely Formed

Completely formed, soft and pliable,

Ossification continues

Begins to store iron, calcium, and phosphorus
Completely formed and movement continues;
however hindered due to space constraints
completely formed
Breast Buds are present in both sexes
Rhythmic breathing movements occur.
NOT mature until 37 weeks.
Labor and Delivery
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Estrogen
From ovaries
Induces oxytocin
receptors on uterus
Oxytocin
From fetus and mother’s posterior
pituitary
Stimulates uterus to contract
Stimulates placenta to make
Prostaglandins
Stimulates more vigorous
contractions of uterus
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