The glands in human body are of two types. One is exocrine glands and the other is endocrine glands.
Endocrine glands
These are ductless glands that secrete substances directly into the blood and which influence metabolism, body growth, development, activity, repair and other bodily functions. The endocrine glands are the glands of internal secretion.
Below are the major endocrine glands in the endocrine system;
Pituitary gland – The Pituitary gland is sometimes called the "master" gland of the endocrine system, because it controls the functions of the other endocrine glands. The Pituitary gland is no larger than a pea, and is located at the base of the brain. The gland is attached to the hypothalamus (a part of the brain that affects the pituitary gland) by nerve fibres. The Pituitary gland itself consists of three sections:
• the anterior lobe
• the intermediate lobe
• the posterior lobe
The anterior lobe produces hormones stimulating the Thyroid gland, the Adrenal glands, ovarian follicles, Ovaries and Testes. It also produces hormones to stimulate milk production in females after giving birth.
The intermediate lobe produces hormones that control the skins pigmentation.
The posterior lobe produces hormones to increase absorption of water into the blood by the kidneys and hormones to contract the uterus during childbirth and stimulate milk production.

Pineal gland – The Pineal gland is about the size of a pea, and is in the centre of the brain in a tiny cave behind and above the pituitary gland. It functions as a gland, secreting the hormone melatonin - which regulates the Pituitary gland and controls our body rhythms e.g. our internal body clock and our waking and sleeping patterns.
Melatonin receptors in the brain react to this hormone and synchronise the body to the twenty four hour day system, therefore informing the brain when it is day and when it is night. Melatonin is derived from Serotonin with which it works to regulate the sleep cycle.

Thyroid gland – the Thyroid glands are situated in the neck. It manufactures hormones which are then secreted into the bloodstream and then act as messengers to affect cells and tissues in other parts of the body.
The Thyroid gland controls metabolism through the production of the thyroid hormone – Thyroxin. The thyroid may become overactive (hyperactive) or underactive (hypoactive.) if the Thyroid gland produces too much thyroxin, the gland becomes overactive. Symptoms can include too much energy, weight loss, a warm feeling and possibly palpitations. If the Thyroid gland can also become underactive (where the gland doesn’t produce enough of the hormone.) symptoms can include little energy, feeling slow and lethargic.

Parathyroid glands – the Parathyroid gland is also situated in the neck. This gland makes a hormone called Parathyroid hormone or Parathormine, which helps the body store, use and regulates the balance of calcium and phosphate in the body.
As with the Thyroid gland, the Parathyroid gland can become overactive or underactive. If the gland becomes overactive this can cause transfer of calcium from the bones to the blood, bones can become brittle and break easily and also osteoporosis. If the gland becomes underactive, this can lower the blood calcium levels causing tetany (involuntary contraction of muscles) and low calcium levels in skeletal muscle causing cramps.

Adrenal glands – The human body has two Adrenal glands, one near the top of each kidney. The inner part of the Adrenal glands (known as the medulla) secretes hormones, such as Adrenaline that helps control blood pressure, heart rate and metabolic rate, blood supply to certain organs and muscle contraction and fatigue. The medulla also produces the hormone Noradrenalin which is similar to the adrenaline hormone. Noradrenalin is involved in the control of blood pressure, heart rate, breathing and relaxation of certain muscle. The outer part of the Adrenal glands (known as the cortex) secretes different hormones such as corticosteroids. This hormone controls the use of carbohydrates, fat and protein by the body, regulates the body’s salt and water balance and has anti-inflammatory effects.

Pancreas – The Pancreas lies just below the stomach. As well as working as an exocrine gland, it also secretes Insulin and Glucagon. Insulin is required to regulate blood glucose levels. The hormone is secreted in order to restore blood glucose levels back to normal. It also helps control the levels of carbohydrates and fats stored in the body. Glucagon is only produce when blood sugar levels are low. This is to encourage the release of sugar into the blood. Insulin and Glucagon have opposite effects in terms of which way they cause blood glucose levels to be driven after their secretion.

Thymus gland – The Thymus gland is a flat gland that lies behind the breastbone. It tends to shrink after birth until, by puberty; it is mostly thin fatty tissue. Its purpose is to process basic Lymphocytes, which help protect against viral infection and cancer. The ‘T’ stands for Thymus derived.

Testes and Ovaries (Gonads) – These glands are naturally different in men and women. In the female, the Gonads are the Ovaries and the female sex hormones are Oestrogen and Progesterone. The female hormones are responsible for developing the rounded, feminine figure, breast growth, pubic hair and all of the normal signs of femininity and reproduction. In the male, the Gonads are the Testes and the male hormone in Testosterone (though each sex produces a small quantity of the opposite sex hormone.) The male hormone is responsible for voice changes, increased muscle mass, development of hair on the body and face and the usual development of manliness.

Exocrine glands
These are glands that discharge secretions, usually through a tube or a duct onto a surface. For example, sweat glands release sweat onto the skin and digestive glands release digestive juices onto the walls of the intestine.
Below are the major exocrine glands in the exocrine system;
Sweat glands – Sweat glands are coiled tubular glands that re found in the dermis or lower part of the skin. They produce a watery secretion and open on to the skin to help control body temperature and provide an emotional response to stimuli. When you sweat, the moisture on your body evaporates and provides a cooling effect for the body. There are two types of Sweat glands; Eccrine sweat gland and Apoerine sweat glands. Both of these types of glands are controlled by the sympathetic nervous system, which controls many of our involuntary actions such as breathing, heartbeat ad sweating.

Salivary glands – These glands are found in and around the mouth and throat. The major Salivary glands are the Parotid, the Submanibular and Sublingual glands. They all secrete saliva into the mouth, the Parotid through tubes that drain saliva called salivary ducts near the upper teeth. The Submandibular secretes under the tongue and the Sublingual through many ducts in the floor of the mouth. Salivary glands produce the saliva used to moisten the mouth, initiate digestion and help protect teeth from decay.

Mammary glands – These are glands that lay within the breast. They are modified Sweat glands known as Areola glands and are designed for the production of milk after birth. Each Mammary gland is made up of between 15 and 20 Areola glands that radiate inwards away from the nipple. Though the multiple branches of these glands are normally small, they enlarge greatly during pregnancy under the influence of many hormones, eventually appearing like bunches of grapes in which milk is manufactured. The milk is carried down lactiferous ducts which increase in diameter as they approach the nipple until they form a lactiferous sinus (or chamber), where milk is stored.

Stomach – The Stomach is a J-shaped elastic sac which is the widest part of the digestive system. Swallowed food is pushed down the oesophagus into the Stomach. Food is enclosed in the Stomach by two circular muscles known as sphincters. As soon as food enters the Stomach, the Stomach lining releases enzymes that start breaking down proteins in the food. The Stomach lining also secretes Hydrochloric Acid, which creates the ideal conditions for the digesting enzymes to work. The potent Hydrochloric Acid kills bacteria, protecting the body from harmful microbes which can enter the body in food. The Stomach protects itself from being digested by its own enzymes or burnt by the Hydrochloric Acid, by secreting sticky, neutralising mucus that clings to the Stomach walls. If this layer becomes damaged in anyway, it can result in painful and unpleasant Stomach ulcers.

Liver – the Liver is the largest internal organ. A big blood vessel, called the portal vein, carries nutrient-rich blood from the small intestine directly to the Liver. Hepatic cells make up about 60% OF THE Liver tissues. These specialised liver cells carry out more chemical processes that any other group of cells in the body. They change most of the nutrients consumed into forms the body cells can use. They convert sugars and store and release them as needed, thereby regulating the blood sugar level. They break down fats and produce cholesterol and they remove ammonia from the body and produce blood proteins, including blood clotting factors. Other functions of the Hepatic cells ate to detoxify drugs and alcohol and produce bile, which breaks down fats in food that is eaten.

Prostate glands – The Prostate gland is a walnut shaped gland located in the pelvic area, just below the outlet of the bladder and in front of the rectum. It encircles the upper part of the urethra, which is the tube that empties urine from the bladder. The Prostate gland sis only present in males. The Prostate is a part of every man’s reproductive system. It requires male hormones, testosterone, to function properly, helping to regulate the bladder control and normal sexual functioning. The main function of the Prostate gland is to store and produce seminal fluid. Seminal fluid is a milky fluid that nourishes sperm.