The Endocrine System

COMPILED BY HOWIE BAUM

THE ENDOCRINE SYSTEM The Endocrine system sends hormones through the Circulatory system to control and
coordinate body functions in much the same way as the nervous system uses tiny electrical
Although often overshadowed by the brain and nerves, the Endocrine system is also signals.
involved in the information business. Hormones carry essential messages that have far-
reaching effects.  The Endocrine system and the Nervous system work together to integrate in the
brain and complement each other, but they tend to work at different speeds.
They control body processes at every level, from energy uptake of a single cell to the whole
body’s rate of growth and development.  Nerves respond within split-seconds but their action soon fades

There are 50 of hormones, which are the body’s chemical messengers and they  Some hormones have longer lasting effects and act over hours, weeks, and
are made by 12 different Endocrine glands. years.

These glands have no ducts but secrete their hormones directly into the blood, by
which means they reach every cell in the body. Hormones regulate processes such as:

Hormones affect certain target tissues or organs and regulate their activities.  The breakdown of chemical substances in metabolism of what we eat and drink

 Fluid balance and urine production

 The body’s growth and development

 Sexual reproduction.

THE 12 PARTS OF THE The hypothalamus and the pituitary gland are part of the diencephalon region of the brain.
ENDOCRINE SYSTEM The hypothalamus connects the nervous system to the endocrine system. It receives and
processes signals from other brain regions and pathways and translates them into hormones,
the chemical messengers of the endocrine system.

These hormones flow to the pituitary gland, which is connected to the hypothalamus by the
infundibulum. Some hormones are stored in the pituitary stores for later release; others
spur it to secrete its own hormones. The hormones released by the pituitary gland and the
hypothalamus control the other endocrine glands and regulate all major internal functions.
 The thymus gland produces THE ADRENAL GLANDS REGULATE SUBSTANCE LEVELS IN THE BLOOD AND
progenitor cells, which RELEASE “FIGHT-OR-FLIGHT” HORMONES
mature into T-cells (thymus-
derived cells). The body
uses T-cells to help destroy
infected or cancerous cells.

T-cells created by the

thymus also help other
organs in the immune
system grow properly.

These cells are so vital,

they are often donated to
those in need. The
Thymus gland is the
primary donor of cells for
the lymphatic system,
much as bone marrow is
the cell donor for the
cardiovascular system. https://www.youtube.com/watch?v=FW2Jat00lEs

The adrenal glands are pyramid-shaped

organs that sit at the top of each kidney.

Each adrenal gland consists of two structures: an

outer adrenal cortex and an inner adrenal medulla.

The adrenal cortex is a network of fine connective

tissues that makes up most of the gland. It
secretes a range of steroid hormones.

Cortisol which manages protein and

glucose levels.

Aldosterone which adjusts our levels of

water and salt.

Androgens and estrogens are secreted by

the adrenal cortex in small amounts by
both sexes.

The adrenal medulla (inside the gland)

produces epinephrine and nor-epinephrine The left kidney is located slightly higher
(NE). These chemicals promote “fight-or- than the right kidney due to the larger
flight,” the body’s initial response to stress. size of the liver on the right side of the
body

2 HORMONES MADE BY THE KIDNEYS

The kidneys make two main hormones, vitamin D and erythropoietin.

Vitamin D is essential for a number of different functions in the body.

Most of the vitamin D that is in the blood is inactive and it is modified by the
kidney and other tissues to activate it.

Active vitamin D stimulates the uptake of calcium from food, is important for the
maintenance of healthy bones and also helps to regulate the response of the
immune system to infection.

Erythropoietin is produced when oxygen levels in the blood are low.

It acts in bone marrow to stimulate the production of mature red blood cells and
to maintain healthy oxygen levels in our tissues.
 SEX GLANDS AND HORMONES

The main sex glands are the ovaries in

females and testes in males.

The sex hormones they produce stimulate

the production of eggs and sperm
respectively and influence the early
development of the embryo into a boy or
girl.

After birth, the circulating levels remain low

until puberty.

Then, in males, the testes increase their

output of androgens (male sex hormones),
such as testosterone.

In females, the ovaries produce more

oestrogens and progesterone.

MASTER GLAND
THE PINEAL GLAND The pituitary is the most
influential gland in the endocrine
The pineal gland is small and pine cone- system.
shaped, (which is how it got its name)
located at the back of the diencephalon It is actually two distinct glands in
region in the brain. one.

At night, in the absence of light, the Its front, or anterior lobe

pineal gland secretes the hormone manufactures 7 major hormones
melatonin. and releases them into the
bloodstream.
Melatonin regulates the body’s
sleep patterns in both circadian Behind it is the posterior (back) lobe
(daily) and seasonal patterns. which receives its two main
hormones from the hypothalamus,
In the morning, when light hits the eye, which lies above it and then it
photo receptors in the retina send releases 3 hormones, as shown.
signals to the pineal gland, which then
decreases melatonin production and we https://www.visiblebody.com/learn/endocrin
wake up. e/hormones#anterior-pituitary

THE THYROID AND PARATHYROID GLANDS INCREASE METABOLISM

AND REGULATE CALCIUM LEVELS

PITUITARY
GLAND

The Hypothalamus Sends

Hormones to the Pituitary Gland to
Control the Endocrine System
 THYROID GLAND

The thyroid gland sits in the throat region, just

below the larynx, served by large arteries with
many branches and a dense network of capillaries.

The hormones it secretes, travel in the

bloodstream throughout the body to:

 Increase metabolism

 Regulate glucose use

 Protein synthesis

 Nervous system development.

 It also releases Calcitonin, which helps

maintain blood calcium homeostasis by
causing calcium to be removed from the https://www.visiblebody.com/learn/endocrine/glands
blood and deposited into bones when blood
(calcium) levels are too high.

Parathyroid Glands Iodine is an element that's required for

the thyroid gland to produce thyroid
On the posterior (back) surface of the thyroid sit hormones.
much smaller, separate glands: the parathyroids.
Since the body does not produce iodine on
Typically there are four parathyroid glands, a its own, it needs to come from dietary
superior and inferior pair on the left and right sources—and striking the right balance is key.
sides of the thyroid.
The Importance of Iodine
They secrete parathyroid hormone (PTH),
which stimulates bones to release calcium into When you consume iodine, it is quickly
the blood when blood (calcium) levels are low. absorbed and entered into your bloodstream.

PTH also causes the kidneys to reduce calcium Your thyroid, which has tiny cells that capture
secretion into urine to further elevate calcium the circulating iodine, takes in and oxidizes it
levels in the blood. so it can begin to be used to create
T3 and T4—thyroid hormones that make their
Together, calcitonin and PTH act in way throughout the body to regulate
complementary ways to maintain blood metabolism and ensure healthy functioning of
calcium homeostasis, which is one of the most the heart, brain, and other organs.
tightly controlled physiological parameters in Go to 50 sec
the body. https://www.youtube.com/watch?v=qjHwOnV9K8A

THE ROLE THAT SOME OF THESE HORMONES PLAY IS OUTLINED BELOW:

GUT HORMONES Ghrelin is produced in the stomach, and its function is to tell the brain that the body has to
be fed. It increases appetite.
The gut hormones work in association
with the gut’s extensive nervous Gastrin is produced in the stomach when it is stretched. It stimulates the release of gastric
system (enteric nervous system) and juice rich in pepsin and hydrochloric acid.
play a coordinating role in:
Secretin is produced in the duodenum and has the effect of stimulating the pancreas to
 The control of appetite produce alkaline secretions as well as slowing the emptying of the stomach.

 The digestion of food Cholecystokinin (CCK) is produced in the duodenum. It reduces appetite, slows down the
emptying of the stomach and stimulates the release of bile from the gall bladder.
 The regulation of energy balance
Peptide YY (PYY) is produced in the last part of the small intestine known as the ileum as
 The maintenance of blood glucose well as parts of the large intestine. It plays a role in slowing down the passage of food along
levels. the gut, which increases the efficiency of digestion and nutrient absorption after meal.

The gut continuously sends information Glucagon-like peptide 1 (GLP-1) is produced in the small intestine and colon and has
to the brain regarding the quality and multiple actions including inhibition of gastric emptying and appetite as well as the
quantity of the food that is consumed. stimulation of insulin release.
 PANCREAS – A DUAL-PURPOSE GLAND
It is also a part of the digestive system.

It excretes pancreatic juice into the small intestine via

the pancreatic duct.

Scattered within the pancreas there are also tiny

cell clusters called pancreatic islets (or islets of
Langerhans) that release hormones into the
bloodstream.

These islets make up less than 2% of pancreatic tissue,

but their specialized cells regulate blood glucose levels
(or blood sugar).

When blood sugar is low, alpha cells in the islets

release glucagon. Glucagon spurs the liver to The Pancreas Regulates Blood Sugar
break down glycogen and release more glucose
into the blood. Surrounded by enzyme-producing acini
cells, the tiny pancreatic islets contain
When blood sugar is high, beta cells in the islets three types of cells: alpha, beta, and
release insulin, which increases glucose reuptake. delta. The secretions of the latter help
regulate insulin and glucagon production.
https://www.youtube.com/watch?v=qzjjW--I-2Q

A SUMMARY ABOUT THE

ENDOCRINE SYSTEM

https://www.youtube.com/watch?v=nCwRX7seya0
4.5 minutes