The special groups of hormone-secreting cells scattered in the pancreas that produce insulin, glucagon, and other hormones for blood sugar regulation are called Islets of Langerhans.
Definitions [15]
Definition: Endocrine System
A group of glands and glandular cells that secrete hormones to regulate and coordinate various functions in the body through chemical control.
Define the following:
Endocrine gland
An endocrine gland is a ductless gland that secretes hormones directly into the bloodstream to regulate various physiological processes and maintain homeostasis in the body.
Define the following:
Exocrine gland
An exocrine gland is a gland that secretes its products (such as enzymes, sweat, or mucus) through a duct directly onto an epithelial surface or into a body cavity, rather than into the bloodstream.
Define the following:
Hormone
Hormone is a molecule that is created and secreted in very minute quantities into the blood stream by an endocrine gland or a specialized nerve cell that governs the growth or functioning of a specific tissue organ in a distant area of the body, e.g., insulin
Define the following:
Hypersecretion
Hypersecretion is a medical and physiological term that refers to the excessive production and release of a substance by a gland or a cell.
Define the following term:
Endocrine system
The endocrine system is defined as a group of organs performing an overall common function. The endocrine glands secrete certain chemicals called hormones.
Definition: Hormone
Endocrine glands secrete certain chemical known as hormones.
or
Hormone is a secretion from some glandular part of the body, which is poured directly into blood and which acts on the target organs or cells of the same individual, bringing about coordination between distant parts of the body.
Define the following:
Beta cells
Beta cells are specialized endocrine cells located within the islets of Langerhans in the pancreas. They are critical to human metabolism because they are the primary source of insulin production in the body.
Define the following:
Hyperglycemia
Hyperglycemia is a medical condition characterized by an abnormally high level of glucose (sugar) in the bloodstream.
Define the following:
Diabetes mellitus
Diabetes mellitus is a chronic metabolic condition characterised by elevated blood glucose (hyperglycemia). It occurs when the body either cannot produce enough insulin or cannot use the insulin it produces effectively.
Definition: Islets of Langerhans
Define the following:
Exocrine gland
- Glands that discharge secretions into ducts are known as exocrine glands.
- Sebaceous glands in the skin, salivary glands in the buccal cavity, etc. are examples of exocrine glands.
Define the following term:
Myxoedema
Myxoedema is a condition that affects an adult if his thyroid does not function properly; in this condition, the person becomes sluggish with swelling of the face and hands.
Define the following:
Exophthalmic goiter
Exophthalmic goitre a form of hyperthyroidism in which the thyroid gland is overactive and secretes excess thyroxine, producing an enlarged thyroid (goitre) together with protrusion of the eyes (exophthalmos).
Define the following:
Hypothyroidism
Hypothyroidism is a medical condition in which the thyroid gland is underactive and fails to produce sufficient thyroid hormone to meet the body’s metabolic needs.
Key Points
Key Points: Human Endocrine System
- Endocrine system controls body activities through chemical messengers called hormones, which are released directly into the bloodstream (no ducts).
- Hormones act as intercellular messengers — they inhibit, stimulate, or modify specific body processes like growth and development, and act only on specific target organs.
- Types of Hormones — Steroid (aldosterone, sex corticoids); Amine (thyroxine, adrenaline); Peptide (ADH, GnRH); Protein (TSH, FSH); Fatty acid derivatives (prostaglandins).
- Endocrine glands are ductless glands — they secrete hormones directly into the blood. Examples: thyroid, pituitary, pancreas, hypothalamus, adrenal glands.
- All endocrine glands work in a coordinated manner, activating each other to bring about overall chemical coordination in the body.
Key Points: Hormones
- Hormones are chemical secretions by endocrine glands that regulate body activities.
- Body activities must be timed and coordinated so processes (like digestive secretions) occur only when needed.
- Besides the nervous system, hormones help regulate complex body functions by acting as chemical messengers.
- Hormones are released into the bloodstream and carried to all parts of the body, but act only on specific target organs or cells.
- Endocrine glands are ductless glands that secrete hormones directly into the blood; some hormones are also produced by organs with other primary functions (e.g., stomach, duodenum).
Key Points: Adrenal Glands
- The adrenal glands are located above each kidney and consist of two parts: the medulla (inner) and the cortex (outer).
- The adrenal medulla secretes adrenaline, the "emergency hormone," which increases heartbeat, blood pressure, and blood glucose during stress.
- The adrenal cortex produces cortisone, mineralocorticoids, glucocorticoids, and sex corticoids, which regulate metabolism, stress response, and salt-water balance.
- Hyposecretion of cortisone causes Addison’s disease, while hypersecretion causes Cushing’s syndrome.
- Hormonal imbalance from adrenal cortex overgrowth can cause adrenal virilism in women (male traits) and feminization in men (e.g., breast enlargement).
Key Points: Pancreas
- Pancreas functions both as an exocrine gland (secreting pancreatic juice into the duodenum) and an endocrine gland (secreting hormones into the blood).
- The Islets of Langerhans contain beta cells (secrete insulin) and alpha cells (secrete glucagon), which regulate blood sugar levels.
- Insulin lowers blood glucose by promoting glucose uptake by cells and storing excess glucose as glycogen in the liver and muscles.
- Under-secretion of insulin causes diabetes mellitus (hyperglycemia), with symptoms like excessive urination, thirst, weakness, and sugar in urine.
- Glucagon raises blood sugar by converting glycogen to glucose in the liver; overdose of insulin can lead to hypoglycemia or insulin shock.
Key Points: Thyroid Gland
1. The thyroid gland is a butterfly-shaped gland located in the neck and secretes thyroxine and calcitonin.
2. Thyroxine controls basal metabolic rate, influences growth, mental development, bone formation, and body temperature.
3. Hypothyroidism may cause:
- Simple goitre (due to iodine deficiency),
- Cretinism (dwarfism and mental retardation in children),
- Myxoedema (sluggishness and swelling in adults).
4. Hyperthyroidism leads to exophthalmic goitre with symptoms like protruding eyes, neck swelling, high metabolism, rapid heartbeat, and breathlessness.
5. Use of iodised salt helps prevent thyroid-related issues caused by iodine deficiency.
Key Points: Pituitary Gland
1. The pituitary gland, also known as the master gland, is a pea-sized endocrine gland located below the hypothalamus and consists of anterior and posterior lobes.
2. The anterior pituitary secretes:
- Growth hormone (GH): controls body growth; deficiency causes dwarfism, excess causes gigantism or acromegaly.
- TSH: stimulates the thyroid.
- ACTH: regulates adrenal cortex.
- Gonadotropic hormones: control testes and ovaries.
3. The posterior pituitary secretes:
- ADH (vasopressin): controls water reabsorption in kidneys; deficiency causes diabetes insipidus.
- Oxytocin: triggers uterine contractions during childbirth and helps in milk ejection.
4. Tropic hormones are those that stimulate other endocrine glands to release their hormones.
5. Disorders from hormonal imbalance include gigantism, acromegaly, and diabetes insipidus.
Important Questions [28]
- Identify the Odd Term in Each Set and Name the Category to Which the Remaining Three Belong : Example : Glucose, Starch, Cellulose
- Identify the Odd Term in Each Set and Name the Category to Which the Remaining Three Belong : Example : Glucose, Starch, Cellulose, Calcium
- Distinguish between Diabetes mellitus and Diabetes insipidus (endocrine gland concerned).
- Briefly Explain the Following Terms: Hormone
- Rewrite the Correct Form of the Statement : Alpha Cells of Pancreas Secrete Insulin.
- Rewrite the correct form of the statement: Cretinism is caused due to deficiency of Adrenaline.
- Fill in the Blanks with Suitable Functions: Thyroid Gland and _________
- The Hormone Secreted by Islets of Langerhans.
- Identify the Odd One in Each Set : Oxytocin, Insulin, Prolactin, Progesterone
- Cretinism and Myxoedema Are Due to
- Give the exact location of the adrenal gland.
- Explain Hormones.
- Give Technical Terms for the a Method of Contraception in Which the Sperm Duct is Cut and Ligated
- Give Technical Terms for Group of Hormones Which Influence Other Endocrine Glands to Produce Hormones
- Match the Items Given in Column a with the Most Appropriate Ones in Column B and Rewrite the Correct Matching Pairs Cretinism Diabetes Insipidus Exophthalmic Goitre Adrenal Virilism D
- Differentiate Between the Following Pairs on the Basis of What is Indicated in the Brackets. Testosterone and Oestrogen [Organ Which Secrets]
- The diagram given below represents the location and structure of an endocrine gland. Study the same and answer the questions that follow:
- Gigantism and Acromegaly Are Due to
- Given below is the outline of the human body showing the important glands: (i) Name the glands marked 1 to 4. (ii) Name the hormone secreted by part 2. Give one important function of this hormone.
- Alpha cells of the pancreas secrete ______.
- State the exact location of the following structure. Islets of Langerhans
- Match the items given in Column I with the most appropriate ones in Column II and rewrite the correct Matching pairs: (a) Hyposecretion of Thyroxine in adults (b) Hyposecretion of Insulin
- Write the exact location of the following gland: Thyroid
- Expand the following biological abbreviation: TSH
- Name the mineral element required for the synthesis of thyroxine.
- The Diagram Given Below Represents an Organ System in the Human Body. Study the Same and Answer the Questions that Follow Draw a Neat, Labelled Diagram Showing the Longitudinal Section of Part 1.
- The diagram given below represents an endocrine gland in the human body. Study the diagram and answer the following questions: (i) Identify the endocrine gland. Where is it located?
- The hormone that affects urination is ______.
