When we perceive a threat, the body's stress hormones like adrenalin  accelerates the body's ability to respond rapidly. Heart rate and breathing is increased. Parathyroid hormone (PTH) activates osteoclast and thereby increases blood calcium, that promotes bone demineralization or bone resorption. The two main actions of oxytocin in the body are contraction of the uterus during childbirth and lactation. When the levels of thyroid hormones become low, it can result in a condition, called as myxoedema. Aldosterone serves as the principal regulator of the salt and water balance of the body.

• Atrial natriuretic peptide (ANP) or atrial natriuretic factor (ANF) is a powerful vasodilator, and a protein (polypeptide) hormone secreted by heart muscle cells. ANF acts to reduce the water, sodium and adipose loads on the circulatory system, thereby reducing blood pressure. 
  
  
• The melanocyte-stimulating hormones ( MSH) are peptide hormones that are produced by cells in the intermediate lobe of the pituitary gland. They stimulate the production and release of melanin (melanogenesis) by melanocytes in skin and hair. An increase in MSH will cause skin darkening in humans. 
  
  
• GIP is a peptide hormone, secreted by the stomach, which stimulates intestinal secretions and insulin release as part of the digestive process; GIP inhibits the secretion of gastric acids and of pepsin. 
  
  
• Calcitonin is a hormone, that is produced in humans by the parafollicular cells (commonly known as C-cells) of the thyroid gland. Thyrocalcitonin (TCT) helps to regulate levels of calcium and phosphate in the blood, opposing the action of parathyroid hormone. This means that it acts to reduce calcium levels in the blood.
  
  Hence , option E is correct.

The primary function of the ovary is the production of ova. In addition to it, ovary acts like an endocrine organ where it secretes oestrogen, progesterone under the influence of FSH. Oestrogen helps to develop and maintain the secondary sexual characters. Glucagon is secreted by alpha cells of islets of Langerhans which helps to maintain the glucose level by preventing glucose level from falling too low. The pituitary is the master gland of the body which controls the function of various other glands. It is divided into two lobes anterior and posterior. The posterior lobe secretes growth hormone, oversecretion of this hormone leads to gigantism and is mostly caused by a tumor in the gland. It results in the oversecretion of growth hormone. Thus the correct answer is option B.  

Vasopressin is secreted from the posterior pituitary gland in response to reductions in plasma volume, in response to increases in the plasma osmolality, and in response to cholecystokinin (CCK) secreted by the small intestine. Its two primary functions are to retain water in the body and to constrict blood vessels. Vasopressin regulates the body's retention of water by acting to increase water reabsorption in the collecting ducts of the kidney nephron

Calcitonin is a polypeptide hormone secreted by the parafollicular cells (C-cells) of the thyroid gland in mammals. The concentration of calcium ion in extracellular fluids is the principal stimulus for the secretion of calcitonin by C-cells. Calcitonin acts as an emergency hormone to protect against the development of hypercalcemia. 

Cholecystokinin (CCK), formerly called as pancreozymin, is a digestive hormone released with secretin when food from the stomach reaches the duodenum. Cholecystokinin is secreted by cells of the upper small intestine. Its secretion is stimulated by the introduction of hydrochloric acid or fatty acids into the stomach or the duodenum. Cholecystokinin stimulates the gallbladder to contract and release stored bile into the intestine. It also stimulates the secretion of pancreatic juice.

Diabetes insipidus is a condition in which the kidneys are unable to prevent the excretion of water. The amount of water excreted in the urine is controlled by antidiuretic hormone (ADH). It is caused by a lack of ADH is called central diabetes insipidus. When it is caused by a failure of the kidneys to respond to ADH, the condition is called as nephrogenic diabetes insipidus. 

Calcitonin hormone stimulates temporary reduction in number and activity of osteoclasts and thereby reducing the blood calcium level to normal. Oxytocin facilitates uterine contractions to push the foetus downward which in turn stretches cervix more during childbirth. Oversecretion of thyroid hormones causes Graves’s disease. ADH stimulates absorption of water by collecting ducts resulting in production of concentrated urine and lower down the urine volume. Option B is correct answer.

The anterior lobe of the hypophysis (pituitary gland) is called as the adenohypophysis. This lobe contains cells, that produce prolactin, growth hormone (somatotropin), thyroid-stimulating hormone, follicle-stimulating hormone. 

Exocrine glands are glands that produce and secrete substances onto an epithelial surface by way of a duct. Examples of Exocrine glands include sweat, salivary, mammary, ceruminous, lacrimal, sebaceous, and mucous. 

• Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into the blood rather than through a duct because endocrine glands lack ducts. Hence they are also called ductless glands.
• The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus, and adrenal glands.
  
• Hence endocrine glands put their secretions directly into the blood.
• So, the correct answer is 'Blood'.

Exocrine glands are glands that produce and secrete substances onto an epithelial surface by way of a duct. Examples of exocrine glands include sweat, salivary, mammary, ceruminous, lacrimal, sebaceous, and mucous.

So, the correct option is ‘Saliva’.

Exocrine glands discharge their products through ducts. E.g., salivary, sweat, digestive gland. 

The endocrine system is composed of ductless glands. Endocrine glands secrete hormones. Glands that have ducts are called exocrine glands. The secretions of exocrine glands reach their target by travelling through a duct (tube). The mixed gland is a gland that produces endocrine and exocrine secretions. The pancreas is an example of a mixed gland because it secretes hormones in the circulation, like insulin and glucagon, but it also releases an exocrine secretion, the pancreatic juice. Whereas, thyroid, pituitary and adrenal glands are not having both endocrine and exocrine system.

Holocrine glands are a type of exocrine glands. They basically release their contents by rupturing, resulting in the death of the secretory cells itself and the contents are released into the lumen. For example, sebaceous glands.

In our body, we have 2 types of control and coordinating systems. One is through neurons, known as the nervous system and another is through hormones known as the endocrine system.

Hormones are organic chemical substances that are released or secreted by endocrine glands in one part of the body and sends out messages that affect cells in other parts of the body. They act as chemical messenger. The target organs or tissues are affected by and respond to only minute quantities of the hormones. Thus, only a small amount of hormone is required to alter cell metabolism. Major endocrine glands include pituitary, thyroid, parathyroids, pancreas, adrenals, testes or ovaries.

The glands are structures in which the cells are involved in the production of hormones or secretions. These hormones or secretions have an effect on the substrates. There are cells in the stomach which are responsible for the production of mucus, HCl, digestive enzymes, etc. There are glandular cells in the stomach but the stomach is not considered as a gland. The liver is the gland which produced various hormones, enzymes and the bile juice. The pancreas produces pancreatic juice with enzymes and hormones by the Islet cells of Langerhans. The kidney is a gland which secretes the hormones erythropoietin and renin.

a) Endocrine glands are the ductless glands that release their secretion (hormones) directly into the bloodstream. The released hormones affect the target cells which specifically carry their receptors.

•  The extracellular ("outside of cell") ligand-binding, a hydrophobic domain extending through the membrane.
• This type  of signaling mechanism is most likely used for communication between two neighboring cells is by extracellular space,

Exocrine gland is the right answer because exocrine glands are glands with ducts unlike endocrine glands. Salivary gland, sweat gland etc are exocrine gland.

• Nervous system is a coordinated network of nerve cells and fibres by which nerve impulses are transmitted throughout the body.
• Endocrine system consists of glands that produce hormones.
• Circulatory system consists of heart and blood vessels which supply throughout the body.

Endocrine glands are the ductless glands that secrete their products into bloodstream from where they are carried to the target organs. Pancreas, testes and thymus are endocrine glands as they secrete hormones. Pancreas secrete insulin and glucagon, testes secrete testosterone and thymus secrete thymosin hormone. Liver is not an endocrine gland instead, it is a digestive organ which secretes bile juice which is necessary for emulsification of fats.
So, the correct answer is 'Liver'.

• Apocrine glands are generally present in the skin and secrete their products on the skin surface.
• Endocrine glands are the ductless glands which secrete their products directly into the blood.
• Heterocrine glands are the glands which act both as exocrine and endocrine glands.For example, in humans, Pancreas is a heterocrine gland. It secretes insulin hormone into blood and act as endocrine gland and when it secretes digestive enzymes and juice through pancreatic duct, it acts as exocrine gland.

• Nervous system is a coordinated network of nerve cells and fibres by which nerve impulses are transmitted throughout the body.
• Endocrine system consists of glands that produce hormones. Hormones are secreted in the blood from where they reach the target organs and cause changes in their functioning and regulation.

• Leydig cells are present in testis and secrete testosterone hormone.
• Lutein cells are present in corpus luteum in ovary and secrete progesterone hormone.
• Parafollicular cells of thyroid gland secrete calcitonin hormone.
• Kupffer cells are phagocytic cells in liver that destroy or breakdown red blood cells.

The glands which pour their secretions directly into blood are called endocrine glands.

Sebaceous glands work with sweat producing eccrine glands to regulate body temperature.

The endocrine system is the collection of glands that produce hormones that produce hormones that regulate metabolism, growth and development, tissue function, sexual function, reproduction, sleep, and mood, among other things.

The pericardium is the protective layer of the heart. It consists of two layers, an outer fibrous layer and the inner serous layer. The serous layer again is made up of two membranes enclosing the pericardial cavity. Molluscs have a true body cavity or coelom. They posses pericardial glands. Antennary glands are also called as green glands. They lie enclosed within the coxal segment of each antenna. Each gland has three parts, namely Sac, labyrinth and bladder. These are seen in crustaceans like arthropods. Protonephridia are of two types, solenocytes and flame bulbs. These are present in animals that lack a true coelom. The protonephridia terminates in the enlarged bulb-like structure and have cilia inside. If there is only one cilium, it is called as solenocyte. If there are more cilia, it is called as flame bulbs.  Lancelets have solenocytes as excretory structure. Rotifers have flame bulbs.

Insulin is a peptide hormone produced by beta cells of the pancreatic islets; it is considered to be the main anabolic hormone of the body. Diabetes is a condition caused by little or no secretion of insulin hormone. If too much insulin is present in the body,a person can go into shock, a condition called insulin shock. Parathyroid hormone is secreted by the parathyroid glands and is the most important regulator of blood calcium levels. Tetany is a condition marked by intermittent muscular spasms, caused by malfunction of the parathyroid glands and a consequent deficiency of calcium. Osteoporosis is a medical condition in which the bones become brittle and fragile from loss of tissue, typically as a result of hormonal changes, or deficiency of calcium or vitamin D. It is a type of hyperthyroidism, meaning hypersecretion of parathormone(parathyroid) hormone.

Diosgenin, a plant steroid sapogenin. Diosgenin is the product of hydrolysis by acids, strong bases, or enzymes of saponins which are extracted from the tubers of Dioscorea wild yam. Diosgenin is used for the commercial synthesis of cortisone, pregnenolone, progesterone, and other steroid products. 

The endocrine system includes ductless glands that secrete hormones and release them directly into the blood. This makes option E correct about the system. Second messengers are the low molecular weight molecules that serve to transmit and amplify the signal of hormones, the first messenger, to initiate the downstream enzyme cascade inside the cell. Second messenger pathway is activated by binding of hormones to the receptor molecules present on the surface of target cells only.