Glands are studied as a part of human anatomy and physiology.
They are sac-like tissue structures in the body which play a vital role in the physiology and homeostasis.
Anatomically they are made of secretory cells and also situated in a safe yet prominent location inside the body.
Glands are quite numerous and regulate different physiological functions and activities.
The glands can be differentiated based on their locations, based on their type of secretions, based on the organ systems they control, etc.
These glands mostly perform their function through the release of secretions. These secretions can be hormones, enzymes and sometimes just fluid yet all of them have some essential functions.
Without their secretions, there can arise enzyme and hormone deficiency diseases.
Different Types of Glands in the human body:
Based on the way of secretion: Glands are two types based on secretion as
1. Exocrine glands: They secrete into a location or region of the body through a duct, and their secretions are called enzymes mostly while some are non-enzymes.
Types of exocrine glands and their secretions include
- Salivary gland: In the buccal cavity secrete saliva. This saliva has many functions.
- Pancreas: Secretes enzyme amylase, trypsin, and lipase. These enzymes digest carbohydrates, proteins, and fats respectively.
- Sperm: Sperms produce Hyaluronidase enzyme by which they swim in the uterine tissue to reach ova. The other application of this enzyme is to help the drug reach inner most tissues of the body.
- Sweat glands: secrete sweat which acts to regulate body temperature and also excretion.
- Sebaceous gland: secrete sebum in the skin and the ear.
- Lachrymal glands: In eye secrete water to moisten the eye.
2. Endocrine glands: Secrete into blood flowing through them, to let the secretion function at distant parts of the body from the gland. They are ductless glands. Their secretions are called as hormones.
They are classified under an endocrine system of the 12 body systems.
Based on their location there are broadly two types of endocrine glands viz.
a) Pituitary Gland (of the hypothalamus): This is a gland located below the hypothalamus in the brain.
For more about anatomy refer to the pituitary structure.
The gland is differentiated as anterior and posterior gland and has definite secretions for each type i.e.
i) Anterior pituitary gland: Located in the front part of the pituitary
- Prolactin: Stimulates milk production in mothers.
- Somatotrophin: A hormone which regulates the growth of the body and tissues.
- Luteinizing hormone: Stimulates ovulation (egg formation) in females and testosterone production in males.
- Thyroid stimulating hormone: Stimulates thyroid gland to produce T3 & T4 hormones.
- Adrenocorticotrophic hormone: Stimulates secretion of glucocorticoids and mineralocorticoid hormones.
- Follicle stimulating hormone signals formation of estrogen and progesterone by the female reproductive system.
ii. Posterior pituitary Present behind the front part of pituitary as shown in the diagram above.
- Vasopressin (anti-diuretic hormone) It controls water loss from kidneys. So minimizes urine formation and saves water in the body.
- Oxytocin It signals uterus for delivery in pregnant women after the period of gestation. It also stimulates milk secretion in mother.
b) Thyroid gland: Produces thyroid hormones T3 & T4.
c) Parathyroid gland: Produces parathormone.
Both thyroid and parathyroid glands are examples for types of glands in the neck.
d) Adrenal gland: located on the two kidneys. It has an outer cortex and inner medulla regions.
- Cortex: secretes glucocorticoids and mineralocorticoids.
- Medulla: secretes nor-adrenalin. This is one of the neurotransmitters and is called a flight or fight hormone.
e) Pancreas: Pancreatic gland has both exocrine and endocrine functions. It secretes multiple hormones which control body glucose metabolism. Its endocrine function release secretions like insulin, glucagon, somatostatin.
f) Kidneys: produce Renin-angiotensin (controls blood pressure).
g) Pineal gland: Located inside the brain and called as natural body clock. One can see jet-lag effects due to its secretions. Melatonin (sleep hormone).
You may also like………> Hormones in the human body.
h) Testes: Secrete Testosterone. Produced only in males to a large extent and to a minimum extent in women. It signals male characters like the beard, heavy muscles, etc.
i) ovaries: Produce Estrogen, progesterone. Secreted only in women and regulate reproduction cycle.
Reference: Principles of Anatomy and Physiology by Gerard J. Tortora
All the glands are located in distinct locations in the human body. They regulate the physiology to a large extent by receiving stimulus from the brain. So we can notice that those glands present in the brain secrete hormones which go outside the brain and act on other glands distributed in different parts of the body. They travel through the blood to the target organs after being released.