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
Chemicals released in one part of the body
that travel through the bloodstream and
affect the activities of target cells.

Hormones are made in
endocrine glands. The glands
release the hormones directly
into the bloodstream.

Hormones travel to their site of
action to perform their function.

Endocrine glands are scattered
throughout the body.


Glands can secrete one
or more hormones
each with different
functions
Lets look at some
examples to
demonstrate the
diversity of functions

Hypothalamus
 Portion of the brain that
connects the nervous
system with the endocrine
system
 Controls the secretions of
the pituitary gland

Pituitary Gland
 Secretes 9 hormones!
▪ Some are involved in production of
sperm and egg
▪ Others are involved in water
absorption

Parathyroids
 Secretes Parathyroid
Hormone (PTH) to
regulate calcium levels in
the blood

Thyroid
 Regulates the body’s
metabolism

Adrenals
 “Fight or flight” response
▪ Release of epinephrine &
norephinephine

Pancreas
 An organ made up of two types of
glands
▪ Exocrine gland- releases digestive
enzymes into stomach
▪ Endocrine gland-releases the hormones
insulin and glucagon into bloodstream

Testes
 Produce testosterone

Ovaries
 Produce estrogen & progesterone


By the union of a male and a female gamete.
Gametes are produced in the sex organs.
 Males produce sperm in the testes.
 Females produce eggs in the ovaries.
 Are you born with the capability to
reproduce? No!
 What has to happen first?
PUBERTY!
Two hormones released from the pituitary
gland causes the onset of puberty.
Testes begin making
testosterone.
 Results in
development of male
characteristics

Ovaries begin making
estrogen.
 Results in the
development of female
characteristics.


Follicle stimulating
hormone (FSH) and
testosterone
stimulates the
production of sperm.

Sperm are haploid.


Follicle stimulating
hormone (FSH) and
testosterone stimulates
the production of sperm.
Sperm are haploid.

Born with all the egg
cells they will ever
produce.

Eggs are haploid.

FSH causes maturation
of the egg.

Progesterone signals for
a thickening of the
uterus lining.
 When the sperm is
deposited in the female
reproductive system, the
sperm swim until they
encounter an egg, or until
they die.
 If sperm does not reach the
egg, fertilization does not
occur.
 If the egg is not fertilized
within 24-48 hours, it
dies.


Sexual
Why?
HAPLOID + HAPLOID = DIPLOID

Aquatic animals release
male and female gametes
near one another in the
water, where fertilization
occurs.

This is called external
fertilization because the
egg is fertilized outside
the female body.


Most land animals reproduce sexually by
internal fertilization, the union of sperm and
egg within the female’s body.
Once fertilization occurs, developing eggs
must be kept moist. How?
 Shells protect them from drying out!
OR
 Eggs develop internally.