Human Endocrine System

Endocrine Glands and Hormones

An endocrine gland secrets hormones directly into the bloodstream, through which it is transported to the target cell or organ throughout the body. Examples of endocrine glands include the pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, gonads (ovaries and testes), and pineal gland....

Human Endocrine System

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The Hypothalamus

Hypothalamus forms the basal part of the diencephalon( forebrain) that regulates various body functions. ​Nuclei, which are neurosecretory cells, also produce hormones. They regulate the synthesis and secretion of the Pituitary gland. Hypothalamus produces two types of hormones,...

Pituitary Gland

The pituitary gland is located in sella turcica (a bony cavity) ​and is attached to the hypothalamus through a stalk. It is divided into two parts:...

Functions of Pituitary Gland Hormones

Hormones Functions Growth hormone Regulates the growth in humans. ​Over secretion – causes Gigantism Under secretion – causes Pituitary dwarfism. ​Excessive secretion in middle age – causes Acromegaly. Prolactin Regulates the growth of the mammary glands and the formation of milk in them. Thyroid-stimulating hormone (TSH) Stimulates the synthesis and secretion of thyroid hormones. Adrenocorticotropic hormone(ACTH) Stimulates the synthesis and secretion of glucocorticoid from the adrenal cortex. Luteinising hormone(LH) ​​Stimulates the synthesis and secretion of Androgen from the testis in males. Androgen regulates spermatogenesis. In females, it induces ovulation of fully mature follicles and maintains corpus lute​um Follicle-stimulating hormone (FSH) Stimulates growth and development of ovarian follicles in females.Regulates spermatogenesis in males. Melanocyte stimulating hormone ​ Acts on melanocyte​ cells present in the skin and regulates pigmentation of the skin. Oxytocin Regulates uterine contraction at the time of childbirth and milk ejection from the mammary gland. Vasopressin ( Antidiuretic hormone) Stimulates resorption of water and electrolyte from the kidney, hence reducing water loss through urine(diuresis)....

Pineal Gland

The Pineal Gland Secrets Melatonin regulates 24 the hour​ rhythm of our body like the sleep-wake cycle, body temperature, etc. It also regulates metabolism, ​pigmentation, the menstrual cycle, and the defense capability of the body....

Thyroid Gland

The thyroid gland consists of two lobes that contacted each other through the isthmus. The thyroid gland is composed of follicles and stromal tissues. Follicles synthesize two hormones: Tetraiodothyronine or thyroxine (T4) and ​Triiodothyronine (T3). Iodine is essential for the normal functioning of the thyroid gland....

Parathyroid Gland

The parathyroid gland which is situated at the back side of the thyroid gland, secrets peptide hormone known as parathyroid hormone. Its level in the body is regulated by the circulating level of calcium ions. PTH is a hypercalcemic hormone, that is, it increases the blood Ca2+ levels, by following processes: stimulating the process of bone resorption, stimulating reabsorption of Ca2+ by the renal tubules, and increasing Ca2+ absorption from the digested food. It plays an important role in maintaining calcium balance in the body....

Thymus

It secrets the peptide hormone, Thymosin. ​It plays an important role in the development of the immune system. It provides Cell-mediated immunity through the differentiation of T – lymphocytes and Humoral immunity, through the production of antibodies....

Adrenal Gland

The adrenal gland is composed of two types of tissues, the​ centrally located tissue is called the adrenal medulla, and outside this lies the adrenal cortex. The adrenal medulla secretes two hormones( catecholamine) called adrenaline or epinephrine and noradrenaline or norepinephrine. These ​are also known as emergency ​hormones ​or hormones of Fight....

Pancreas

Pancreas act as both the Exocrine and Endocrine glands. The Exocrine part consists of Islets of Langerhans ​which contain two types of cells, alpha cells, and beta cells. Alpha ​Cells secrets Glucagon and ​beta cells secrets Insulin....

Testis

Testis acts both as a sex organ and an endocrine gland. It consists of seminiferous tubules and stromal or interstitial tissue. Leydig cells produce a group of hormones called Androgen. For example, Testosterone....

Ovary

The ovary which is the primary female sex organ, produces two groups of steroid hormones called Estrogen and Progesterone....

Hormones of the Heart, Kidney, and Gastrointestinal tract

The atrial wall of our heart secrets a peptide hormone, Atrial natriuretic factor (ANF), which decreases blood pressure through the dilation of blood vessels. The kidney produces a peptide hormone called Erythropoietin which stimulates erythropoiesis (formation of RBC). The gastrointestinal tract secretes four major peptide hormones, namely Gastrin: which stimulates the secretion of hydrochloric acid and ​pepsinogen. ​Secretin: stimulates the secretion of water and bicarbonate ions. Cholecystokinin (CCK): stimulates the secretion of pancreatic enzymes and bile juice. Gastric inhibitory peptide (GIP): inhibits Gastric secretion and mobility....

Mechanism of Hormone Action

​Hormone receptors are the proteins present in the target tissue only. When they are present on the cell ​membrane of the target tissue, they are called membrane-bound receptors and the receptors present inside the target cell are called intracellular receptors. The mechanism of action of hormones is as follows:...

FAQs on Chemical Coordination and Integration

Q1: Define Hormones....