what is adrenal gland? what are its two regions and the hormones released from the adrenal gland

ADRENAL GLAND 

introduction 

Adrenal gland are one of the most important endocrine gland of the body . Adrenal glands are also known by the name of suprarenal glands as they are present above the kidneys both of the adrenal glands are divided into two regions that are the upper region that is known as the adrenal cortex whereas the lower region is known as the adrenal medulla . In humans adrenal glands are located on both sides of the back in the retroperitoneum above and slightly medial to the kidneys both of the adrenal glands are of pyramidal shape whereas the left adrenal gland is slightly larger than the right one . In humans adrenal glands are 1.0 cm thick 5.0 cm in length and are 3.0 cm width . These glands are of yellowish color in an adult human both of the adrenal glands weight about 7 -10 grams . A fatty capsule surrounds the adrenal gland which also surrounds the kidneys and lies within the renal fascia . The location of the adrenal gland is such that they are present below the diaphragm and are attached to the crura of the diaphragm by the renal fascia  The adrenal glands are separated from the kidneys by through a thin and weak wall of connective tissues . 

structure of adrenal glands 

Each of the adrenal glands comprises of two distinct parts each having their own functions and features and these two parts are as following

• Adrenal cortex
• Adrenal medulla 

renal cortex 

                                 from the intermediate mesoderm the tissues of the adrenal cortex is derived . It first appears 33 days after fertilization the fetal adrenal cortex is different from its adult counterpart as it is composed of two distinct zones the inner fetal zone which carries most of the hormone producing activity and the outer definitive zone which is in a proliferative phase the adrenal gland decreases in size after birth because of the rapid disappearance of the fetal zone with a corresponding decrease in androgen secretion . Aldosterone cortisol and androgen are some of the hormones produced by the adrenal cortex . Adrenal cortex is further divided into three layers that are known as zones and the three zones of adrenal cortex are as following

• zone glomerulosa 
• zone fasciculata 
• zone reticularis 

1. zone glomerulosa is the outermost layer of the adrenal cortex . This zone is involved in the production of hormone aldosterone a mineralocorticoid that is produced by the action of enzyme aldosterone synthase and aldosterone plays a very important and crucial role in long term regulation of the blood pressure  
2. the largest of the three zones of cortex present between the zone glomerulosa and zone reticularis is known by the name of zone fasciculata . It is responsible for the production of important hormone such as glucocorticoid that is a cortisol this zone is about 80% of the renal cortex in this zone cells are arranged in columns radially orientated towards the medulla in this zone cells contain abundant mitochondria and smooth endoplasmic reticulum 
3. the zone of cortex that is directly adjacent to the medulla is the inner most layer that goes by the name of zone reticularis this zone is mainly involved with the production of androgen mainly dehydroepiandrosterone DHEA dehydroepiandrosterone sulfate DHEAs and androstenedione (which is a precursor )

medulla 

                      from the neural crest cells which comes from the ectoderm layer of the embryo adrenal medulla is derived these cells migrate from their initial position and aggregate in the vicinity of the dorsal aorta to form the adrenal medulla and other organs of sympathetic nervous system adrenal medulla cells are also known by the name chromaffin cells because they contain granules that stain with chromium salts and it is a character that is not present in all sympathetic organs adrenaline and non adrenaline are the two main hormones secreted from the renal medulla about 20% of the non adrenaline and 80% of the adrenaline are secreted from here . The chromaffin cells of the medulla are the body main source of the catecholamines (adrenaline and non adrenaline ) medulla can be considered as a specialized sympathetic ganglion unlike the other sympathetic ganglion the adrenal medulla lacks distinct synapses and releases its secretion directly into the blood 

hormones of the adrenal gland 

Adrenal gland one of the most important endocrine gland of the body including both of its regions that are region cortex and the renal medulla secretes these following hormones 

• corticosteroids
• adrenaline 
• non adrenaline 
• androgen 

corticosteroids 

                       these are a group of steroid hormones that are produced from the cortex of the adrenal gland all corticosteroids share a common precursor that is cholesterol therefore the first step in steroid-genesis is cholesterol uptake or synthesis corticosteroids are of two different types and are named according to their actions and these are 

• glucocorticoid
• mineralocorticoid

1. mineralocorticoid is a hormone that is produced from the zone glomerulosa of the adrenal cortex hormone aldosterone a mineralocorticoid is essential for the regulation of salt minerals balance and blood volume at the kidneys aldosterone acts at the level of proximal convulated tubules and the collecting duct by increasing the absorption of sodium and excretion of both potassium and hydrogen ion . Angiotensin 2 and extracellular potassium are the two main regulators of aldosterone production the amount of sodium in the body effect the extracellular volume which in turn influences blood pressure mineralocorticoid production is regulated by the factors such as renin andiotensin aldosterone system the concentration of potassium and to some extent the concentration of ACTH 
2. glucocorticoid have many effects on metabolism as the name of this hormone suggest this hormone is involved with the increase in the circulating level of glucose in the body the adrenal gland secretes a basal level of cortisol but can also produce burst of the hormone in response to adrenocorticotropic hormone (ACTH) released from the Anterior pituitary Glucocorticoids are under the regulatory influence of the hypothalamus pituitary adrenal axis (HPA). Glucocorticoid synthesis is stimulated by ACTH a hormone that is released from the pituitary gland and in turn ACTH is stimulated by presence of corticotropin releasing hormone (CRH) which is released by neurons of the hypothalamus

adrenaline and non adrenaline 

                                           adrenaline and non adrenaline are also known by the name of catecholamines as they are water soluble compounds that are made up of a catechol group and a amino group about 20% of the non adrenaline and 80% of the adrenaline are secreted from the adrenal medulla adrenaline and non adrenaline are also known as the stress hormone that prepares the body for the fight or flight movements. Catechlamines are produced in chromaffin cells in the adrenal medulla from tyrosine or is produced from phenylalanine in the liver. Catecholamine release is stimulated by the activation of the sympathetic nervous system when activated it evokes the release of catecholamine from the storage granules by stimulating the opening of calcium channels in the cell membrane

androgen

               cells in the zone reticularis of the adrenal gland produces male sex hormone or also known as androgen most important of which is dehydroepiandrosterone DHEA generally these hormones do not have an overall effect in the male body but they convert to more potent forms such as in the form of testosterone and dihydrotestosterone (DHT) or in case of females it is estrogen and these hormones such as testosterone and estrogen are produced in gonads

          

DISEASES RELATED TO ADRENAL GLAND 

 The normal function of the adrenal gland may be disturbed by various circumstances such as infections genetic disorders autoimmune diseases or any kind of side effect that is caused as a result of any sort of medication or medical therapy these things effect the gland directly or indirectly as a result of dysregulation of hormone production leading to over or underproduction of hormones some of the disorders of the adrenal glands are as following 

• Addison's disease
• cushing syndrome 
• primary aldosteronism 
• congenital adrenal hyperplasia 
• adrenal insufficiency 

cushing disease 

               cushing disuses occurs due to overproduction or present of excess glucocorticoid in the body this condition can occur as a result of some underlying cause such as hypothalamic pituitary adrenal axis ( HPA axis ) prolonged treatment with glucocorticoid the most common cause of endogenous cushing syndrome is a pituitary adenoma which causes an excess production of ACTH some of the symptoms or side effects occurring in this disorder are excessive protein breakdown disturbance in metabolism high blood sugar leading to diabetes obesity increased blood pressure osteoporosis

primary aldosteronism 

                                                          this condition is caused as result of excess production of aldosterone some some of the causes of this disorder are bilateral hyperplasia of the glands Conn's syndrome etc the most prominent symptoms of it are hypertension electrolyte imbalance increasing potassium depletion and sodium retention 

adrenal insufficiency 

                              this is disorder that is caused as a result of deficiency of glucocorticoid it is very rare it is further divided into primary adrenal insufficiency such as Addison's disease and the other one is secondary adrenal insufficiency

 

Addison's disease 

                          Addison's disease is a disorder in which there is decreased production of mineralocorticoid and glucocorticoid production by the adrenal gland it is an autoimmune disorder in thi disease body produces antibodies that attacks the cells of its own cells of adrenal gland one of the main symptom of addition's disease is hyper-pigmentation of skin along with some non specific symptoms such as fatigue  

secondary adrenal insufficiency 
                                          in this disorder there is a dysfunction of the hypothalamic pituitary adrenal axis that leads to a decreased stimulation of the adrenal cortex in this type of disorder there is a effect on the production of (ACTH) by the pituitary gland this type of adrenal insufficiency usually does not effect the production of mineralocorticoid which is under regulation of the renin angiotensin system