Endocrine System

Prepared by : Nha Nit

Contents
1. General lesson about endocrine system
2. Anatomy and hormones
1.General lesson about endocrine system

❖ The endocrine system is in charge of creating and releasing hormones

to maintain countless bodily functions. Endocrine tissues include the
pituitary gland, thyroid, pancreas and others. There are several
conditions related to endocrine system issues usually due to a
hormone imbalance or problems directly affecting the tissue.
What is the endocrine system?
• The endocrine system consists of the tissues (mainly glands) that
create and release hormones.
• Hormones are chemicals that coordinate different functions in the
body by carrying messages through the blood to the
organs, skin, muscles and other tissues. These signals tell the body
what to do and when to do it. Hormones are essential for life and the
health.
What is the function of the endocrine system?
• The main function of the endocrine system is to release hormones into
the blood while continuously monitoring the levels. Hormones deliver
their messages by locking into the cells they target so they can relay
the message. A person has more than 50 different hormones, and they
affect nearly all aspects of the health — directly or indirectly. Some
examples include:
➢ Metabolism.
➢ Homeostasis (constant internal balance), such as blood pressure and blood
sugar regulation, fluid (water) and electrolyte balance and body temperature.
➢ Growth and development.
 ➢ Sexual function.
➢ Reproduction.
➢ Sleep-wake cycle.
➢ Mood.
Very small amounts of hormones can trigger significant responses and
changes in your body. If your body has too little or too much of a
hormone, it affects your health. This often causes noticeable symptoms.
What are the endocrine system organs?
The endocrine system consists of three types of tissues:
• Endocrine glands.
• Organs.
• Endocrine-related tissues.
❖Endocrine system glands
Glands are special tissues in your body that create and release substances. Endocrine
glands make and release hormones directly into your bloodstream. The endocrine
glands in your body from head to toe include:
• Pineal gland: This is a tiny gland in your brain that’s beneath the back part of
your corpus callosum. It makes and releases the hormone melatonin.
• Pituitary gland: This is a small, pea-sized gland at the base of your brain below
your hypothalamus. It releases eight hormones, some of which trigger other
endocrine glands to release hormones.
• Thyroid gland: This is a small, butterfly-shaped gland at the front of your neck
under your skin. It releases hormones that help control your metabolism.
• Parathyroid glands: These are four pea-sized glands that are typically behind
your thyroid. Sometimes they exist along your esophagus or in your chest (ectopic
parathyroid glands). They release parathyroid hormone (PTH), which controls the
level of calcium in your blood.
• Adrenal glands: These are small, triangle-shaped glands on top of each of your
two kidneys. They release several hormones that manage bodily processes, like
metabolism, blood pressure and your stress response.
❖Notes: You have other glands in your body that aren’t endocrine glands, such as
sweat glands (a type of exocrine gland).
❖Endocrine system organs
Certain organs in your body also make and release hormones. An organ is a group of
tissues that form a structure that performs specific important functions in your body.
The organs that are part of your endocrine system include:
• Hypothalamus: This is a structure deep within your brain (which is an organ). It’s
the main link between your endocrine system and your nervous system. It makes
two hormones that your pituitary gland stores and releases (oxytocin and
vasopressin) and makes and releases two hormones (dopamine and somatostatin).
• Pancreas: This organ is in the back of your abdomen (belly). It’s both an organ
and a gland and is also part of your digestive system. It releases two hormones that
are essential to maintaining healthy blood sugar levels: insulin and glucagon.
• Adipose tissue (body fat): This is a connective tissue that extends throughout
your body. It’s found under your skin (subcutaneous fat), between your internal
organs (visceral fat) and in the inner cavities of bones (bone marrow adipose
tissue). Adipose tissue releases many different hormones,
including leptin, angiotensin and adiponectin.
• Ovaries: These are small, oval-shaped glands located on either side of
your uterus. They produce and store your eggs (also called ova) and make sex
hormones that control your menstrual cycle and pregnancy.
• Testicles (testes): These are small, round organs underneath your penis in your
scrotum. They make sperm and sex hormones, particularly testosterone.
❖Other tissues that release hormones
Other tissues in your body release hormones. But we don’t typically think of them
as endocrine system tissues because they have other, more significant functions or
roles. They include:
• Digestive tract (stomach and small intestine): Your digestive tract is the largest
endocrine-related organ system. It makes and releases several hormones that play
a role in your metabolism. Examples include gastrin and ghrelin.
• Kidneys: Your kidneys are two bean-shaped organs that filter your blood. They’re
part of your urinary system, but they also produce hormones, like erythropoietin
and renin.
• Liver: Your liver is part of your digestive system, but it also produces hormones,
including insulin-like growth factor 1 (IGF-1) and angiotensinogen.
• Heart: When your blood pressure rises, your heart releases two hormones called
A-type natriuretic peptide and B-type natriuretic peptide.
• Placenta: The placenta is a temporary endocrine organ that forms during
pregnancy. It produces hormones that are important for maintaining a healthy
pregnancy and preparing your body for labor and breastfeeding (chestfeeding).
2.Anatomy and hormones
❖Hypothalamus produces hormones:
• Anti-Diuretic Hormone (Vasopressin) (ADH)
• Corticotropin-Releasing Hormone (CRH)
• Oxytocin
• Gonadotropin-Releasing Hormone (GnRH)
• Somatostatin
• Growth Hormone-Releasing Hormone (GHRH)
• Thyrotropin-Releasing Hormone (TRH)
• Dopamine
❖Mechanism
• Anti-Diuretic Hormone (Vasopressin) – regulates water levels and influence blood volume and
blood pressure.
• Corticotropin-Releasing Hormone – acts on the pituitary gland causing the release
of hormones in response to stress.
• Oxytocin – influences sexual and social behavior.
• Gonadotropin-Releasing Hormone – stimulates the pituitary to release hormones that influence
the development of reproductive system structures.
• Somatostatin – inhibits the release of thyroid-stimulating hormone (TSH) and growth hormone
(GH).
• Growth Hormone-Releasing Hormone – stimulates the release of growth hormone by the
pituitary.
• Thyrotropin-Releasing Hormone – stimulates the pituitary to release thyroid-stimulating
hormone (TSH). TSH regulates metabolism, growth, heart rate, and body temperature.
• Dopamine – important signaling molecule in the hypothalamus.
❖Pituitary gland is divided :
•Anterior pituitary gland
•Posterior pituitary gland
Anterior pituitary gland has hormones:
➢ Growth hormone (GH)
➢ Thyroid-stimulating hormone (TSH)
➢ Follicle-stimulating hormone (FSH)
➢ Luteinizing hormone (LH)
➢ Adrenocorticotropin hormone (ACTH)
➢ Prolactin (PRL)
➢ Melanocyte stimulating hormone (MSH)
• The anterior pituitary releases hormones in response to hormones secreted from
the hypothalamus.
• The hypothalamus releases hormones into its surrounding interstitial fluid, which
permeate into nearby fenestrated capillaries. These capillaries form the
hypophyseal portal system that extends into the anterior pituitary. They are
histologically similar to veins. However, they connect to each other, rather than to
arteries and veins, and provide a rich supply to the pituitary endocrine cells.
• The hormones released by the hypothalamus into the anterior pituitary are
either releasing hormones (RH) that stimulate the secretion/synthesis of
hormones or inhibiting hormones (IH) that inhibit the synthesis/secretion of
hormones.
❖Posterior pituitary gland:
➢ Anti-diuretic hormone (ADH) : is made by a part of the brain called the
hypothalamus and is secreted into the blood by the pituitary gland. Certain
types of tumors may release high amounts of antidiuretic hormone, which can
cause low levels of sodium in the blood and the body to retain water.
➢ Oxytocin : produces by hypothalamus, but it stores in posterior pituitary gland
and release it into the bloodstream.
Posterior pituitary gland:
1. Antidiuretic Hormone (ADH).
➢This maintains water homeostasis.
➢It increases water reabsorption by the distal tubules and collecting ducts of the
kidneys, increasing urine concentration.
➢This also leads to vasoconstriction, which increases blood pressure.
2. Oxytocin:
➢This will stimulate uterine contraction during labor.
➢This may be used to induce labor.
➢It helps the breasts to release milk from the mammary ducts.