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by Ananth


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Biology Presentation:

Biology Presentation By Ananth, Manu, Kishan, Rahul, Ruchir , Nishith



Some Important Definitions:

Some Important Definitions

What Are Hormones ?:

What Are Hormones ?

Slide 5:

A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence , it is a chemical messenger that transports a signal from one cell to another . All multicellular organisms produce hormones. Hormones in animals are often transported in the blood. Cells respond to a hormone when they express a specific receptor for that hormone.

Hormone Signalling:

Hormone Signalling Biosynthesis of a particular hormone in a particular tissue Storage and secretion of the hormone Transport of the hormone to the target cell Recognition of the hormone by an associated cell membrane or intracellular receptor protein Relay and amplification of the received hormonal signal : This then leads to a cellular response. The reaction of the target cells may then be recognized by the original hormone-producing cells, leading to a down-regulation in hormone production. Degradation of the hormone.

Effects Of Hormones:

Effects Of Hormones Hormones have the following effects on the body stimulation or inhibition of growth mood swings induction or suppression of apoptosis (programmed cell death) activation or inhibition of the immune system regulation of metabolism preparation of the body for mating, fighting, fleeing, and other activity preparation of the body for a new phase of life, such as puberty, parenting, and menopause control of the reproductive cycle hunger cravings A hormone may also regulate the production and release of other hormones

Hormone + Receptor:

Hormone + Receptor

What Are Glands ?:

What Are Glands ?

Slide 12:

A gland is an organ in a multicellular organism that synthesizes a substance for release of substances such as hormones. Glands are made up of tissues or group of cells On basis of secretion they are of two types Exocrine glands (ductless) Endocrine glands (ductual)


Formation Every gland is formed by an ingrowth from an epithelial surface. This ingrowth may from the beginning possess a tubular structure, but in other instances glands may start as a solid column of cells which subsequently becomes tubulated. As growth proceeds, the cells divide or give off offshoots, in which case a compound gland is formed. In some the number of branches is limited, in others a very large structure is finally formed by repeated growth and sub-division


Classification Glands can also be classified according to their shape. • If the gland retains its shape as a tube throughout it is termed a tubular gland. • In the second main variety of gland the secretory portion is enlarged and the lumen variously increased in size. These are termed alveolar or saccular glands.




Exocrine glands are a type of ductal glands that secrete their products (including hormones and other chemical messengers) into ducts that lead directly into the external environment. Typical exocrine glands include sweat glands, salivary glands, mammary glands, stomach, liver, pancreas

Classification Of Exocrine Glands:

Classification Of Exocrine Glands

1. Based On Structure:

1. Based On Structure Exocrine glands contain a glandular portion and a duct portion, the structures of which can be used to classify the gland. • The duct portion may be branched (called compound) or unbranched (called simple). • The glandular portion may be tubular or acinar , or may be a mix of the two (called tubuloacinar ). If the glandular portion branches, then the gland is called a branched gland.

2. Based On The Product Secreted:

2. Based On The Product Secreted Serous glands - secrete proteins, often enzymes. Examples include chief cells and Paneth cells Mucous glands -secrete mucus. Examples include Brunner's glands, esophageal glands, and pyloric glands Mixed glands -secrete both protein and mucus. Examples include the salivary glands. , the parotid gland is predominantly serous, the sublingual gland is redominantly mucous, and the submandibular gland is both serous and mucous.

3.Based On Method Of Secretion:

3.Based On Method Of Secretion Apocrine glands - a portion of the plasma membrane buds off the cell, containing the secretion,an example is fat droplet secretion by mammary gland. Holocrine glands - the entire cell disintegrates to secrete its substance, an example is sebaceous glands for skin and nose. Merocrine glands - cells secrete their substances by exocytosis an example is pancreatic acinar cells.



Slide 23:

The endocrine system is a system of glands, each of which secretes a type of hormone directly into the bloodstream to regulate the body. It derives from the Greek words endo meaning inside, within, and crinis for secrete. The endocrine system is an information signal system like the nervous system, yet its effects and mechanism are classifiably different. The endocrine system's effects are slow to initiate, and prolonged in their response, lasting for hours to weeks. The nervous system sends information very quickly, and responses are generally short lived

Slide 24:

. Hormones are substances (chemical mediators) released from endocrine tissue into the bloodstream where they travel to target tissue and generate a response. Hormones regulate various human functions, including Metabolism, growth and development, tissue function, and mood. The field of study dealing with the endocrine system and its disorders is endocrinology. Features of endocrine glands are, in general, their ductless nature, their vascularity, and usually the presence of intracellular vacuoles or granules storing their hormones.

Slide 25:

In contrast, exocrine glands, such as salivary glands, sweat glands, and glands within the gastrointestinal tract, tend to be much less vascular and have ducts or a hollow lumen. In addition to the specialised endocrine organs mentioned above, many other organs that are part of other body systems, such as the kidney, liver, heart and gonads, have secondary endocrine functions. For example the kidney secretes endocrine hormones such as erythropoietin and renin



Pineal Gland:

Pineal Gland

Slide 30:

The pineal gland is a small endocrine gland in the vertebrate brain. It produces the serotonin derivative melatonin, a hormone that affects the modulation of wake/sleep patterns and seasonal functions. Its shape resembles a tiny pine cone (hence its name), and it is located near the centre of the brain, between the two hemispheres, tucked in a groove where the two rounded thalamic bodies join.


function Pineal gland produces a hormone called Melatonin which is a derivative of the amino acid tryptophan, which also has other functions in the central nervous system. The production of melatonin by the pineal gland is stimulated by darkness and inhibited by light. Photosensitive cells in the retina detect light and directly signal the SCN, which relay the circadian signals to the spinal cord and out via the sympathetic system to superior cervical ganglia (SCG), and from there into the pineal gland. The function(s) of melatonin in humans is not clear; it is commonly prescribed for the treatment of circadian rhythm sleep disorders. The compound pinoline is also produced in the pineal gland; it is one of the beta- carbolines .



Slide 34:

The hypothalamus affects the endocrine system and governs emotional behavior, such as anger . Most of the hypothalamic hormones generated are distributed to the pituitary via the hypophyseal portal system. The hypothalamus maintains homeostasis; this includes a regulation of blood pressure, heart rate, and temperature.

Slide 35:

The Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland ( hypophysis ). The hypothalamus is located below the thalamus, just above the brain stem. In the terminology of neuroanatomy , it forms the ventral part of the diencephalon. All vertebrate brains contain a hypothalamus. In humans, it is roughly the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the autonomic nervous system. It synthesizes and secretes certain neurohormones , often called hypothalamic-releasing hormones, and these in turn stimulate or inhibit the secretion of pituitary hormones. The hypothalamus controls body temperature, hunger, thirst , fatigue, sleep, and circadian cycles.

Pituitary Gland:

Pituitary Gland

Slide 39:

Located at the base of the brain, the pituitary gland is protected by a bony structure called the sella turcica (also known as turkish saddle) of the sphenoid bone. the pituitary gland, is an endocrine gland about the size of a pea and weighing 0.5 g (0.02 oz.), in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity ( sella turcica ) covered by a dural fold ( diaphragma sellae ). The pituitary is functionally connected to the hypothalamus by the median eminence via a small tube called the infundibular stem (Pituitary Stalk). The pituitary fossa, in which the pituitary gland sits, is situated in the sphenoid bone in the middle cranial fossa at the base of the brain. The pituitary gland secretes nine hormones that regulate homeostasis.


functions Functions Hormones secreted from the pituitary gland help control the following body processes: • Growth (Excess of HGH can lead to gigantism and acromegaly.) • Blood pressure • Some aspects of pregnancy and childbirth including stimulation of uterine contractions during childbirth • Breast milk production • Sex organ functions in both men and women • Thyroid gland function • The conversion of food into energy (metabolism) • Water and osmolarity regulation in the body • Water balance via the control of reabsorption of water by the kidneys • Temperature regulation Pituitary gland also makes endorphin to relieve pain and alter mood

Thyroid Gland:

Thyroid Gland

Slide 42:

, The thyroid gland or simply, the thyroidis one of the largest endocrine glands. The thyroid gland is found in the neck, below (inferior to) the thyroid cartilage (which forms the laryngeal prominence, or 'Adam's Apple'). The isthmus (the bridge between the two lobes of the thyroid) is located inferior to the cricoid cartilage. The thyroid gland controls how quickly the body uses energy, makes proteins, and controls how sensitive the body should be to other hormones. It participates in these processes by producing thyroid hormones, the principal ones being triiodothyronine (T3) and thyroxine (T4). These hormones regulate the rate of metabolism and affect the growth and rate of function of many other systems in the body. T3 and T4 are synthesized from both iodine and tyrosine. The thyroid also produces calcitonin, which plays a role in calcium homeostasis .

Slide 43:

Hormonal output from the thyroid is regulated by thyroid-stimulating hormone (TSH) produced by the anterior pituitary, which itself is regulated by thyrotropin -releasing hormone (TRH) produced by the hypothalamus. The thyroid gets its name from the Greek word for "shield", after the shape of the related thyroid cartilage. The most common problems of the thyroid gland consist of an overactive thyroid gland, referred to as hyperthyroidism, and an underactive thyroid gland, referred to as hypothyroidism.

Parathyroid Glands:

Parathyroid Glands

Slide 45:

The parathyroid glands are small endocrine glands in the neck that produce parathyroid hormone. Humans usually have four parathyroid glands, which are usually located on the rear surface of the thyroid gland, or, in rare cases, within the thyroid gland itself or in the chest. Parathyroid glands control the amount of calcium in the blood and within the bones. The parathyroid glands are four or more small glands, about the size of a grain of rice, located on the posterior surface (back side) of the thyroid gland. The parathyroid glands usually weigh between 25mg and 40mg in humans

Slide 46:

The two parathyroid glands on each side which are positioned higher (closer to the head) are called the superior parathyroid glands, while the lower two are called the inferior parathyroid glands. Occasionally, some individuals may have six, eight, or even more parathyroid glands. The parathyroid glands are named for their proximity to the thyroid but serve a completely different role than the thyroid gland.

Slide 47:

The parathyroid glands are quite easily recognizable from the thyroid as they have densely packed cells, in contrast with the follicle structure of the thyroid. However, at surgery, they are harder to differentiate from the thyroid or fat. In the histological sense, they distinguish themselves from the thyroid gland, as they contain two types of cells

Thymus Glands:

Thymus Glands

Slide 49:

The thymus is a specialized organ of the immune system. The only known function of the thymus is the production and "education" of T-lymphocytes (T cells), which are critical cells of the adaptive immune system. The thymus is composed of two identical lobes and is located anatomically in the anterior superior mediastinum, in front of the heart and behind the sternum. Histologically, the thymus can be divided into a central medulla and a peripheral cortex which is surrounded by an outer capsule. The cortex and medulla play different roles in the development of T-cells. Cells in the thymus can be divided into thymic stromal cells and cells of hematopoietic origin (derived from bone marrow resident hematopoietic stem cells). Developing T-cells are referred to as thymocytes and are of hematopoietic origin. Stromal cells include thymic cortical epithelial cells, thymic medullary epithelial cells, and dendritic cells .

Slide 50:

The thymus provides an inductive environment for development of T-lymphocytes from hematopoietic progenitor cells. In addition, thymic stromal cells allow for the selection of a functional and self-tolerant T-cell repertoire. Therefore, one of the most important roles of the thymus is the induction of central tolerance. The thymus is largest and most active during the neonatal and pre-adolescent periods. By the early teens, the thymus begins to atrophy and thymic stroma is replaced by adipose (fat) tissue. Nevertheless, residual T lymphopoiesis continues throughout adult life.



Slide 53:

The pancreas is a gland organ in the digestive and endocrine system of vertebrates. It is both an endocrine gland producing several important hormones, including insulin, glucagon, and somatostatin, as well as an exocrine gland, secreting pancreatic juice containing digestive enzymes that assist the absorbtion of nutrients and the digestion in the small intestine. These enzymes help to further break down the carbohydrates, proteins, and lipids in the chyme.


functions The pancreas is a dual-function gland, having features of both endocrine and exocrine glands. The part of the pancreas with endocrine function is made up of approximately a million cell clusters called islets of Langerhans. Four main cell types exist in the islets. They are relatively difficult to distinguish using standard staining techniques, but they can be classified by their secretion: α cells secrete glucagon (increase glucose in blood), β cells secrete insulin (decrease glucose in blood), δ cells secrete somatostatin (regulates/stops α and β cells), and PP cells secrete pancreatic polypeptide .

Slide 55:

The islets are a compact collection of endocrine cells arranged in clusters and cords and are crisscrossed by a dense network of capillaries. The capillaries of the islets are lined by layers of endocrine cells in direct contact with vessels, and most endocrine cells are in direct contact with blood vessels, by either cytoplasmic processes or by direct apposition. According to the volume The Body, by Alan E. Nourse ,[5] the islets are "busily manufacturing their hormone and generally disregarding the pancreatic cells all around them, as though they were located in some completely different part of the body." The islet of Langerhans plays an imperative role in glucose metabolism and regulation of blood glucose concentration.

Adrenal Gland:

Adrenal Gland

Slide 57:

In mammals, the adrenal glands are endocrine glands that sit atop the kidneys; in humans, the right suprarenal gland is triangular shaped, while the left suprarenal gland is semilunar shaped. They are chiefly responsible for releasing hormones in response to stress through the synthesis of corticosteroids such as cortisol and catecholamines such as epinephrine. The adrenal glands affect kidney function through the secretion of aldosterone, a hormone involved in regulating the osmolarity of blood plasma.

Slide 58:

The adrenal cortex is devoted to the synthesis of corticosteroid hormones. Specific cortical cells produce particular hormones including cortisol, corticosterone , androgens such as testosterone, and aldosterone. Under normal unstressed conditions, the human adrenal glands produce the equivalent of 35–40 mg of cortisone acetate per day . In contrast to the direct innervation of the medulla, the cortex is regulated by neuroendocrine hormones secreted by the pituitary gland and hypothalamus, as well as by the renin-angiotensin system.

Slide 59:

The adrenal cortex comprises three zones, or layers. This anatomic zonation can be appreciated at the microscopic level, where each zone can be recognized and distinguished from one another based on structural and anatomic characteristics. The adrenal cortex exhibits functional zonation as well: by virtue of the characteristic enzymes present in each zone, the zones produce and secrete distinct hormones . Zona glomerulosa Zona reticularis Zona fasciculata



Slide 62:

The testicle is the male gonad in animals. Like the ovaries to which they are homologous, testes are components of both the reproductive system and the endocrine system. The primary functions of the testes are to produce sperm (spermatogenesis) and to produce androgens, primarily testosterone. Both functions of the testicle are influenced by gonadotropic hormones produced by the anterior pituitary. Luteinizing hormone (LH) results in testosterone release. The presence of both testosterone and follicle-stimulating hormone (FSH) is needed to support spermatogenesis



Slide 64:

The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands Ovaries secrete both estrogen and progesterone. Estrogen is responsible for the appearance of secondary sex characteristics of anatomically female people at puberty and for the maturation and maintenance of the reproductive organs in their mature functional state. Progesterone functions with estrogen by promoting menstrual cycle cyclic changes in the endometrium

Slide 65:

Ovaries secrete both estrogen and progesterone. Estrogen is responsible for the appearance of secondary sex characteristics of anatomically female people at puberty and for the maturation and maintenance of the reproductive organs in their mature functional state. Progesterone functions with estrogen by promoting menstrual cycle cyclic changes in the endometrium

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