2. Learning outcomes
At the end of this session you will be able to:
Explain how the structure of the main
features of the human reproductive system in
males and females is related to their
functions
Explain the structure of ovaries and testes in
relation to their functions
Describe gamete formation
3. The reproductive system
Reproduction is crucial for the survival of our species,
the basic purpose of our species is to reproduce but the
equipment that differs men and women biologically is our
reproductive organs
They become functional after the onset of puberty, the
male system remain functioning from then until death,
women however, are only functional until menopause.
The male system ends at intercourse, women’s
reproductive role extends from intercourse until childbirth
5. Function
The functions of the male reproductive
organs are the production of male gametes
(spermatozoa) and the transportation of
sperm to the female reproductive tract and
production of the male sex hormone
testosterone, which controls the secondary
male sexual characteristics (body and facial
hair, male physique, vocal chords)
6. The penis
The outer foreskin layer is a
continuation of the skin of the shaft
of the penis.
The inner foreskin layer is not just
"skin," but mucocutaneous tissue of
a unique type found nowhere else
on the body.
The ridged band is the interface
(join) between the outer and inner
foreskin layers. When the penis is
not erect, it tightens to narrow the
foreskin opening. During erection,
the ridged band forms ridges that go
all the way around, about halfway
down the shaft.
The reddish or purplish glans or
glans penis (head of the penis) is
smooth, shiny, moist and extremely
sensitive.
The frenulum, or frenum, is a
connecting membrane on the
underside of the penis, similar to
that beneath the tongue.
7. Testicles
The scrotum
This is a pouch of loose skin and muscle that contains the testes, a
septum divides the scrotum internally for the right and left testes. The
scrotum is located outside of the body as the sperm need to be cooler
than normal body temperature. Muscle fibres help to maintain
temperature control by contracting (to elevate the testes in cold
weather) and relaxing (to lower the testes and to increase the surface
area of the scrotum)
The Testes
These are the glands that produce the male reproductive cells (the
sperm) each testis is surrounded by connective tissue that divides it into
approximately 200 lobules. In each lobule there are between one and
three tiny tubules called seminiferous tubules, these produce sperm
by the process of cell division (mitosis). This process is called
spermatogenesis and continues through life.
It takes approximately 72 days to produce a semi-mature sperm, which
is then released into the tubule for transport to the outside of the testis
8. Sperm
A sperm comprises of a head,
mid piece and a tail
the mid piece is the motor that
provides the energy to make
the tail spin and propel the
sperm.
The head is covered with a
sheath of digestive material
that allows it to penetrate the
wall of the female ovum; under
this is the genetic material
(chromosomes).
There are 23 single
chromosomes including the
male sex chromosome (Y) and
female sex chromosome (X)
9. The Epididymis
The convoluted seminiferous tubules lead to straight
tubules, the straight tubules join together to form the
efferent ducts, these lead to into a convoluted tubule
called the Epididymis. The Epididymis sits on top of the
scrotum and can be felt through the scrotum, the sperm
undergo further maturation and after 14 days the sperm
acquire the ability to move (motility)
The Spermatic Cord
Also known as The Vas Deferens, the mature sperm are
propelled by rapid smooth muscle contractions
(ejaculation) which convey the sperm into the Urethra,
the spermatic cord passes into the abdominal cavity
through the inguinal canal. The two spermatic cords
pass above and behind the urinary bladder before
entering the prostate gland to join the urethra
10. The Seminal Vesicles
These gland sit on the posterior wall of the urinary bladder, they
each have an ejaculatory duct that enters the prostate gland. The
seminal vesicles are lined with epithelium; this produces a viscous
alkaline fluid containing glucose, amino acids, ascorbic acid
(vitamin C) clotting enzymes and prostaglandins. This fluid forms
most of the volume of semen, the fluid that is produced at
ejaculation.
The Prostate Gland
The first part of the male urethra is surrounded by prostate gland;
this is several glands enclosed within a capsule. Within the
prostate gland the ejaculatory duct joins the urethra, the prostate
gland secretes a milky substance that contains chemicals and
enzymes that are needed by the sperm for motility and for
modifying vaginal acidity, and this is added to the semen during
ejaculation
12. External genitalia: the vulva
The Mons pubis is a pad of fat
covered with skin, and after puberty,
hair. Below and to the rear of this
are two folds of fatty tissue covered
with skin called the labia Majora,
this protects the other external
genitalia from injury and infection
Pubic hair grows on the outer part,
the inner part is smooth.
Inside the Labia Majora are two
folds of skin called the Labia
Minora, they meet to form a hood
like structure that covers and protect
the Clitoris. The Labia Minora
contains several sebaceous glands
that lubricate the surface. The
clitoris is a small sensitive organ that
is made of erectile tissue and
nerves, the exposed part of the
clitoris is called the glans
13. Vagina and uterus
The Vagina is a muscular passage which is lubricated by
Bartholin’s glands, prior to sexual intercourse, the vagina is
blocked by a double fold of mucous membrane called the
Hymen. The vagina runs to the cervix, this is lined with mucus
membranes and is folded and puckered, these folds are called
fornices. This allows for stretching during childbirth. The mucus
membranes store glycogen and secrete an organic acid, this
maintains the acidic environment that prevents micro bacterial
growth and is harmful to sperm
The Uterus is a hollow, pear shaped muscular organ situated in
the pelvic cavity, and the rounded top is called the fundus, the
mid section is called the body and it contains a triangular cavity
called the uterine cavity, the two fallopian tubes enter the
uterus at the upper right angles of the cavity
14. Structure of the uterus
The walls of the uterus contain the
myometrium which is made of longitudinal,
transverse and circular smooth muscle that
produces coordinated contractions to help
expel the foetus
And an inner lining of endometrium, this
layer is either shed every 28 days or nurtures
the growing foetus
15. Fallopian tubes
The Fallopian tubes
convey the ovum from
the ovary to the uterus;
the ovaries are two
small almond shaped
glands that produce
secondary oocytes
(which mature into ova)
and the hormones
progesterone and
oestrogen
16. The ovaries
At birth around 400 000
cells in primordial follicles
have reached prophase of
the first meiotic division
and are called primary
oocytes. Each month
after puberty, one of these
cells completes its
development into an ovum
(secondary oocyte).
18. Function of the reproductive system
For pregnancy to occur a sperm must fertilise the egg. The
sperm travel from the epididymis into the Vas Deferens by waves
of contractions along the walls of the tubes. Sexual stimulation
triggers contractions in the wall of the Vas Deferens. Sperm are
swept along, past the prostate gland and the seminal vesicles,
which secrete fluid to maintain the sperm in a viable state. The
resulting mixture, called semen, is expelled from the end of the
penis during ejaculation. The alkaline semen is deposited at the
top of the acidic vagina.
A layer of mucus blocks the cervix. It is thinnest, and therefore
easiest for the sperm to penetrate at the beginning of the
menstrual cycle. The sperm move by a combination of swimming
using their tails, muscular contractions of the uterus and/or
oviducts, and the action of cilia lining the uterus and the oviducts.
