The endocrine system is a collection of glands that secrete hormones directly into the bloodstream. Hormones are chemicals that act on their target organs to increase or decrease the target’s activity level.
The endocrine system is instrumental in maintaining homeostasis.
Types of Glands
The body has two types of glands: Endocrine glands and Exocrine glands
Endocrine glands release hormones directly into the bloodstream. Since they have no ducts, they are also called ductless glands.
Exocrine glands release their secretions into a duct that carries them to the outside of the body.
Glands of the Endocrine System
2 adrenal glands
2 ovaries in the female
4 parathyroid glands
2 testes in the male
Two Adrenal Glands
They are located above each of the kidneys.
Each gland is composed of two sections:
Adrenal Cortex- the outer portion of the adrenal glands; secretes several families of hormones: mineralocorticoids, glucocorticoids, and steroid sex hormones .
Adrenal medulla- the inner portion of the adrenal gland. It secretes epinephrine and norepinephrine.
The 2 ovaries are located in the lower abdominopelvic cavity of the female. They are female gonads. Gonads are organs that produce gametes, or the reproductive sex cells. In females, the gamets are in the ova.
The ovaries produce the female sex hormones, estrogen and progesterone.
Estrogen is responsible for the apperance of the female sexual characteristics and regulation of the menstrual cycle.
Progesterone helps to maintain a suitable uterine environment for pregnancy.
It is located along the lower curvature of the stomach.
It is the only organ in the body that has both the endocrine and exocrine functions. The exocrine portion releases digestive enzymes through a duct into the duodenum of the small intestines.
The endocrine sections of the pancreas, islets of Langerhans, produce insulin and glucagon.
4 tiny glands located on the dorsal surface of the thyroid gland.
The parathyroid hormone (PTH) secreated by these glands regulates the amount of calcium in the blood.
Small pine-cone shaped gland that is part of the thalamus region of the brain.
The pineal gland secretes melatonin.
It also plays a role in regulating the body’s circadian rhythm.
This is the 24-hour clock that governs our periods of wakefulness and sleepiness.
Located underneath the brain.
The small marble-shaped gland is divided into an anterior lobe and a posterior lobe.
Both lobes are controlled by the hypothalamus in the brain.
Two oval glands located in the scrotal sac of the male.
They are the male gonads, which produce the male gametes, sperm, and the male sex hormone, testosterone.
Testosterone produces the male secondary sexual characteristics and regulates sperm production.
It is part of the immune system, the thymus is also one of the endocrine glands because it secretes the hormone thymosin, which is important in development in the immune system.
It is located in the medialstinal cavity anterior and superior to the heart.
The Thyroid Gland
It resembles a butterfly in shape, has right and left lobes.
It is located on either side of the trachea and larynx.
It produces the hormones thyroxine also known as T4, and triiodothyronine which is called T3.