Definition of Gland
A gland is a group of cells or a “secretory organ” that excretes a chemical substance. This substance can take the form of hormones, sweat, saliva, mucus, or acids (ie HCl acid in gastric glands). The glands are tasked with helping to create the substance they secrete for later use or complete elimination from the body.
The image shows the different ways in which cells secrete substances
Now, let's discuss the actual development of a gland. Each gland can be thought of as an internal growth of the top layer of the skin called the epithelium. It is the most superficial layer of our skin. This ingrowth is remarkably tubular and may begin as a column of cells or as a tubular prestructure. Over time, the column of cells divides or gives off branches that help formcomposedglands. This branching is particularly useful in creating large, heavily branched glands, such as the salivary and pancreatic glands in the body, which contain an impressive surface area. These formations (simple, branched, and compound) make up a variety of glandular structures.
However, shape is the final determinant of gland classification. If the gland maintains a tubular shape during growth, it is called atubulargland. If the secretory part of the gland increases in size, it is called aalveolargland (assuming a “bulb” shape much like the alveoli in our lungs). The coiled glands curl up and the acinar cells have a lobed berry appearance. Simple, unbranched, or minimally branched glands include the variations listed in the figure below.
The image shows five types of simple glands (in order): simple tubular, simple branched tubular, simple spiral tubular, simple acinar, and simple branched acinar glands.
Likewise, compound glands come in three main forms. The main difference between compound glands and simple glands is that they come in more complicated branching arrangements. They assume a tubular, acinar, or combined tubulo-acinar form, as shown below.
The image shows three compound glands: tubular compound, acinar compound, and tubulo-acinar compound.
Types of Gland
Glands are sectioned into two groups based on their function. Endocrine glands excrete chemicals, such as hormones, through the basal lamina of cells that travel through the bloodstream. Examples of endocrine glands are the thyroid and pituitary glands, which play important roles in preserving the body's homeostatic balance. But the endocrine glands are varied.
Main endocrine glands (and their main functions):
- Thyroid gland:it mainly helps to regulate our metabolism and vital bodily functions with the release of the hormones TSH, T3 and T4. This gland is butterfly-shaped and located in the neck. Other functions it helps regulate are our breathing, our heart rate, our weight and body temperature (and much more).
- pituitary gland:it is the size of a pea and is located behind our noses. It is directly controlled by the hypothalamus. The pituitary gland is often referred to as the “master gland” because it releases a plethora of growth hormones and stimulators that affect our thyroid, adrenal glands, and sex organs (i.e., prolactin, which stimulates milk production, growth hormones for muscle and bone mass, etc.)
- Pancreas:it is also considered a gland, despite being a whole organ, as it is a secretory organ. Maintains healthy blood sugar levels through the release of insulin and glucagon. The pancreas also releases digestive enzymes that break down proteins, fats and carbohydrates in our food.
- Pineal gland:releases melatonin, which is involved in the sleep cycle. The pineal gland plays a role in regulating our circadian rhythm (or sleep-wake cycles which are linked to periods of light and dark throughout the 24-hour cycle).
- adrenal gland:help control blood sugar and the use of carbohydrates and fats. They are located at the top of each kidney and release sex hormones and cortisol – which is a stress hormone.
- Timo:it is located between our lungs and is only active until the onset of puberty. It secretes hormones important for puberty and a healthy immune system.
- Testicles (in men):release the sex hormone testosterone. Despite lying freely in the scrotum, it is connected to the body by the spermatic cord, which is highly innervated and connected to our blood vessels. Testosterone promotes sperm production and our sex drive.
- Ovaries (in women):produces estrogen, which promotes breast development and healthy periods. Estrogen initiates menstruation and the release of an egg each month.
Exocrine glands, on the other hand, use ducts to expel their material onto an epithelial surface rather than into the bloodstream. That outer surface could be our skin or even our GI tract. Material is always expelled at the apical surface (“top”) of our cells.
Major exocrine glands:
- Salivary Glands (contains amylase to help soften our food)
- Liver bile-producing glands
- Part of the pancreas that secretes pancreatic enzymes into the duodenum of the small intestine
- Prostate (helps boost seminal fluid during ejaculation)
- Gastric Glands (digest our food)
- Sweat glands (remove body heat)
Everyday examples of glands
One gland that we are all perhaps painfully aware of is the sweat gland. Whether we feel them during a class speech or after a good hour of exercise, we know that our sweat glands are close to the epidermis of our skin and secrete beads of moisture. There are two types of sweat glands: eccrine and apocrine. Eccrine glands are distributed throughout our body and secrete water-based moisture; it's the main way our body cools down. Apocrine glands, on the other hand, are those located in our armpits and perineal areas. Apocrine glands are known to compress their secretions into vesicles which then enter the lumen. Although they play a less significant role in humans, they are the only glands in hoofed animals such as cattle.
The figure shows an eccrine sweat gland.
Another familiar apocrine gland in mammals are the mammary glands. Mammary glands can be classified as exocrine (rather than endocrine) and are used to store and secrete milk to feed young animals. Like the apocrine glands, lactating animals are capable of withdrawing their milk secretions in membrane-enclosed vesicles.
Quiz
1. What is the main determinant of how a gland is classified?
A.material excreted
B.number of cells
C.Form
D.Location
Answer to question #1
Cis correct. While the other options listed are important for understanding the type of gland being studied, the main determinant of how a gland is classified is its shape (i.e. simple acinar, tubular composite, etc.)
2. Define the distinction between endocrine and exocrine glands:
A.Endocrine glands secrete from the apical lamina into the bloodstream; exocrine glands to the basal surface of the epithelium
B.Endocrine glands secrete from the basal lamina into the bloodstream, exocrine glands secrete to the apical surface of the epithelium
C.Exocrine glands secrete from the apical lamina into the bloodstream, endocrine glands secrete into the basal surface of the epithelium
D.Exocrine glands secrete material through membrane-bound vesicles, endocrine glands do not.
Answer to question #2
Bis correct. As discussed earlier, endocrine glands release hormones directly into the bloodstream through the basal lamina of the gland, while exocrine glands release their contents onto the apical surface of the epithelial lining, such as the skin or even our GI tract.
3. Which of the following is characteristic of the apocrine method of secretion?
A.Apocrine glands use vesicles to secrete content
B.Apocrine glands release water-based moisture in granules to cool the body
C.Apocrine glands use cell signaling mechanisms exclusively to coordinate secretion
D.Unlike eccrine glands, apocrine glands are more populous and dispersed throughout the body.
Answer to question #3
Ais correct. Apocrine glands are less numerous than eccrine glands in the human body and, unlike eccrine glands, use membrane-bound vesicles to transport secretions. Notably, apocrine glands are not limited to one type of sweat gland but also include mammary glands.
References
- Hormone Health Network (2017). “Endocrine Glands and Types of Hormones.”Hormone.org. Retrieved 5/28/2017 from http://www.hormone.org/hormones-and-health/endocrine-glands-and-types-of-hormones
- Ingraham, Susan (2016). “The exocrine system: how it works.”exocrine systemRetrieved 5/28/2017 from http://www.susaningraham.net/exocrine-system.html
- Prakash Mohini (2017). “What is the difference between Simple Gland and Compound Gland?”preserve articles. Retrieved 5/29/2017 from http://www.preservearticles.com/2011082111261/what-is-the-difference-between-simple-gland-and-compound-gland.html
- Theodora (2017). “Epithelial, endothelial, and glandular tissue.”Theodora Encyclopedia. Retrieved 5/30/2017 from http://www.theodora.com/encyclopedia/e/epithelial_endothelial_and_glandular_tissues.html
FAQs
What are the types of glands explain with examples? ›
Two principal types of glands exist: exocrine and endocrine. The key difference between the two types is that, whereas exocrine glands secrete substances into a ductal system to an epithelial surface, endocrine glands secrete products directly into the bloodstream [1].
What are the 12 glands in the human body? ›- hypothalamus.
- pituitary.
- thyroid.
- parathyroids.
- adrenals.
- pineal body.
- the ovaries.
- the testes.
- Holocrine Glands.
- Merocrine Glands.
- Apocrine Glands.
Endocrine glands help control many body functions, including growth and development, metabolism, and fertility. Some examples of endocrine glands are the pituitary, thyroid, and adrenal glands.
What are five glands and their functions? ›- Pituitary gland which secretes growth hormone.
- Thyroid gland which secretes thyroxine hormone.
- Parathyroid gland which secretes parathormone.
- Pancreas which secretes insulin.
- Adrenal glands secrete adrenaline.
Examples of exocrine glands include sweat glands, lacrimal glands, salivary glands, mammary glands, and digestive glands in the stomach, pancreas, and intestines.
What are the 4 main glands? ›The female ovaries, male testes, and pituitary, thyroid, and adrenal glands are major constituents of the endocrine system.
What are the 5 types of glands? ›- thyroid.
- adrenal gland.
- testes.
- ovaries.
The hormones released by the endocrine system control many important functions in the body, including growth and development, metabolism, and reproduction. The endocrine system includes the hypothalamus, pineal gland, pituitary gland, thyroid gland, parathyroid glands, thymus, adrenal glands, and pancreas.
How many glands are in the body? ›The endocrine system is made up of seven different glands that make chemicals called hormones. Hormones are substances that act as "messengers" to control many body functions.
What is an example of human gland? ›
Pineal gland: a small gland near the centre of the brain. Thyroid gland: a small gland in the front of the neck, wrapping around the windpipe. Parathyroid glands: four small glands in the neck behind the thyroid gland. Adrenal glands: 2 glands that sit above the kidneys on each side of the body.
What is an example of glands in the human body? ›Many glands make up the endocrine system. The hypothalamus, pituitary gland, and pineal gland are in your brain. The thyroid and parathyroid glands are in your neck. The thymus is between your lungs, the adrenals are on top of your kidneys, and the pancreas is behind your stomach.
Is the pancreas A gland? ›The pancreas is made up of 2 types of glands: Exocrine. The exocrine gland secretes digestive enzymes. These enzymes are secreted into a network of ducts that join the main pancreatic duct.
What are the types of gland? ›- Adipose tissue.
- Adrenal glands.
- Hypothalamus.
- Kidneys.
- Ovaries.
- Pancreas.
- Parathyroid glands.
- Pineal gland.
The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus and adrenal glands. The hypothalamus and pituitary gland are neuroendocrine organs.
What is the function of each gland? ›| Hormone | Secreting gland(s) | Function |
|---|---|---|
| glucagon | pancreas | helps increase levels of blood glucose (blood sugar) |
| insulin | pancreas | helps reduce your blood glucose levels |
| luteinizing hormone (LH) | pituitary | controls estrogen and testosterone production as well as ovulation |
| melatonin | pineal | controls sleep-wake cycles |
Your liver and pancreas are exocrine glands too. Your liver secretes bile through ducts into your gastrointestinal tract. Your pancreas secretes pancreatic juices through ducts into your gastrointestinal tract. But your liver and pancreas are also considered endocrine glands.
What are the examples of endocrine vs exocrine glands? ›Examples of exocrine glands are sweat, salivary, sebaceous, mucous gland. An endocrine gland is a gland which secretes its products directly into the blood stream. Examples of endocrine glands are pituitary gland, ovaries, testes, thyroid gland, adrenal glands.
What are the 5 endocrine glands? ›The glands that make up the endocrine system produce chemical messengers called hormones that travel through the blood to other parts of the body. Important endocrine glands include the pituitary, thyroid, parathyroid, thymus, and adrenal glands.
What are the 20 endocrine glands? ›- Endocrine Glands. Unlike exocrine glands(sweat, salivary), endocrine glands secrete their respective substances directly into the bloodstream rather than through a duct. ...
- Pituitary gland. ...
- Thyroid gland. ...
- Parathyroid glands. ...
- Adrenal glands. ...
- Pancreas. ...
- Gonads. ...
- Pineal gland.
What is the most important gland in the body? ›
The pituitary gland is sometimes called the "master" gland of the endocrine system because it controls the functions of many of the other endocrine glands. The pituitary gland is no larger than a pea, and is located at the base of the brain.
Is A kidney A gland? ›The kidney is traditionally regarded as an exocrine gland, producing urine to regulate body fluid volumes and composition and to excrete nitrogenous wastes. In addition to these functions, it is now recognized that a number of hormones are produced within the kidney that have local and systemic actions.
Which of the following is not a gland? ›Final answer: The tongue is not a gland.
What are 3 glands that most mammals have? ›The mammalian integument includes various secretory glands, including sebaceous glands, eccrine glands, apocrine glands, and mammary glands.
How many glands are in the mouth? ›There are three pairs of large salivary glands. Parotid glands are found in front of and just below each ear. Submandibular glands are below the jaw.
How many glands does a woman have? ›The ovaries
A woman has 2 ovaries. The ovaries are found on each side of the uterus, just below the opening of the fallopian tubes. These are the tubes that extend from the uterus to near the ovaries. The ovaries contain the egg cells needed for reproduction.
Glands produce and release different hormones that target specific things in the body. You have glands all over your body, including in your neck, brain and reproductive organs. Some glands are tiny, about the size of a grain of rice or a pea.
What are the 2 main skin glands? ›There are eccrine and apocrine sweat glands.
What are the types of simple glands? ›A simple gland has an unbranched duct (or no duct at all). There is only a single secretory unit (acinus or tubule). Examples include sweat glands, gastric glands, intestinal crypts, and uterine glands.
What are the two main categories of glands called ____? ›There are two major categories of glands in the body - exocrine and endocrine.
What is the female gland? ›
The ovaries are the dominant organ in females that make and secrete sex hormones for females. The theca cells and granulosa cells within the ovaries produce sex hormones for females. The theca cells make androgens, and the granulosa cells take the androgen and convert it into estrogen.
Which gland is present in male? ›Testes: Testes are the endocrine glands found only in males. The ductless glands, which secrete their products, that is, hormones directly into the blood, are known as endocrine glands.
What is the gland in male and female? ›The gonads, the primary reproductive organs, are the testes in the male and the ovaries in the female. These organs are responsible for producing the sperm and ova, but they also secrete hormones and are considered to be endocrine glands.
What is an example for gland and organ? ›The term "organ" is a more general term that refers to a group of tissues that are designed to complete some function in the body. For example, the thyroid gland secretes thyroid hormones to regulate metabolism, and the liver is an organ that helps rid the body of toxins.
What is the definition of pituitary gland? ›A pea-sized organ attached to the part of the brain called the hypothalamus. It lies at the base of the brain above the back of the nose. The hypothalamus sends signals to the pituitary gland, which then makes hormones that control other glands and many of the body's functions, including growth and fertility.
What gland secretes insulin? ›For instance, the pancreas secretes insulin, which allows the body to regulate levels of sugar in the blood.
Which is the largest endocrine gland? ›Thyroid gland is the largest endocrine gland of the body. It is present in the neck region and is responsible for the secretion of hormones like thyroxine that control the metabolic rate in the body.
What are the 3 types of glands and what do they secrete? ›- Salivary glands - secrete saliva.
- Sweat glands- secrete sweat.
- Mammary glands- secrete milk.
- Endocrine glands - secrete hormones.
| Difference Between Exocrine Glands and Endocrine Glands | |
|---|---|
| Endocrine Glands | Exocrine Glands |
| Examples | |
| Thyroid glands, parathyroid glands, pituitary glands, adrenal glands. | Salivary glands, liver, Brunner's glands, oesophageal glands. |
Pineal gland: a small gland near the centre of the brain. Thyroid gland: a small gland in the front of the neck, wrapping around the windpipe. Parathyroid glands: four small glands in the neck behind the thyroid gland. Adrenal glands: 2 glands that sit above the kidneys on each side of the body.
What are the different types of endocrine glands explain? ›
Important endocrine glands include the pituitary, thyroid, parathyroid, thymus, and adrenal glands. There are other glands that contain endocrine tissue and secrete hormones, including the pancreas, ovaries, and testes. The endocrine and nervous systems work closely together.
What is the definition and classification of a gland? ›(gland) An organ that makes one or more substances, such as hormones, digestive juices, sweat, tears, saliva, or milk. Endocrine glands release the substances directly into the bloodstream. Exocrine glands release the substances into a duct or opening to the inside or outside of the body.
What is an example of a Holocrine gland? ›Sebaceous glands are examples of holocrine glands. It produces sebum through holocrine secretion. The sebum on the skin keeps it flexible and prevents it from drying out.
How many different glands are there? ›The endocrine system is made up of seven different glands that make chemicals called hormones. Hormones are substances that act as "messengers" to control many body functions.
What does pituitary gland do? ›Anatomy of the Pituitary Gland
It regulates growth, metabolism, and reproduction through the hormones that it produces. The production of these hormones is either stimulated or inhibited by chemical messages sent from the hypothalamus to the pituitary. The posterior lobe produces two hormones, vasopressin and oxytocin.
What Is the Pancreas? The pancreas is unique in that it's both an endocrine and exocrine gland. In other words, the pancreas has the dual function of secreting hormones into blood (endocrine) and secreting enzymes through ducts (exocrine).
Which gland is responsible for growth? ›The pituitary gland is a structure in our brain that produces different types of specialised hormones, including growth hormone (also referred to as human growth hormone or HGH). The roles of growth hormone include influencing our height, and helping build our bones and muscles.
What are the 7 hormones of the endocrine system? ›- Adrenocorticotropic hormone (ACTH or corticotropin).
- Follicle-stimulating hormone (FSH).
- Growth hormone (GH).
- Luteinizing hormone (LH).
- Prolactin.
- Thyroid-stimulating hormone (TSH).