LocationLocation A retroperitoneal gland, lies at the superior pole of the kidney, embedded in adipose tissue. A retroperitoneal gland, lies at the superior pole of the kidney, embedded in adipose tissue. The right gland is pyramidal in shape while the left one is crescent-shaped. The right gland is pyramidal in shape while the left one is crescent-shaped. Its dimensions are 1x2x5 cm and its weight is 7-10 gm. Its dimensions are 1x2x5 cm and its weight is 7-10 gm. Supplied by 3 arteries and drained by one vein. Supplied by 3 arteries and drained by one vein. A retroperitoneal gland, lies at the superior pole of the kidney, embedded in adipose tissue. A retroperitoneal gland, lies at the superior pole of the kidney, embedded in adipose tissue. The right gland is pyramidal in shape while the left one is crescent-shaped. The right gland is pyramidal in shape while the left one is crescent-shaped. Its dimensions are 1x2x5 cm and its weight is 7-10 gm. Its dimensions are 1x2x5 cm and its weight is 7-10 gm. Supplied by 3 arteries and drained by one vein. Supplied by 3 arteries and drained by one vein.

Connective Tissue Stroma Each gland is surrounded by thick connective tissue capsule containing large amounts of adipose tissue. Each gland is surrounded by thick connective tissue capsule containing large amounts of adipose tissue. The capsule sends septa between the parenchyma of the gland accompanied by blood vessels and nerves. The capsule sends septa between the parenchyma of the gland accompanied by blood vessels and nerves. Parenchymal cells are supported by reticular fibers. Parenchymal cells are supported by reticular fibers. Each gland is surrounded by thick connective tissue capsule containing large amounts of adipose tissue. Each gland is surrounded by thick connective tissue capsule containing large amounts of adipose tissue. The capsule sends septa between the parenchyma of the gland accompanied by blood vessels and nerves. The capsule sends septa between the parenchyma of the gland accompanied by blood vessels and nerves. Parenchymal cells are supported by reticular fibers. Parenchymal cells are supported by reticular fibers.

Blood supply of the gland It has one of the richest blood supply of the body. It has one of the richest blood supply of the body. Supplied by three arteries: Supplied by three arteries: –Superior suprarenal artery from inferior phrenic artery. –Middle suprarenal artery from aorta. –Inferior suprarenal artery from renal artery. Drained by one vein: Drained by one vein: –Suprarenal vein  Inferior venal cava (right side) and left renal vein (left side). It has one of the richest blood supply of the body. It has one of the richest blood supply of the body. Supplied by three arteries: Supplied by three arteries: –Superior suprarenal artery from inferior phrenic artery. –Middle suprarenal artery from aorta. –Inferior suprarenal artery from renal artery. Drained by one vein: Drained by one vein: –Suprarenal vein  Inferior venal cava (right side) and left renal vein (left side).

Parenchyma of the gland Divides into two parts; cortex (80 % of the gland and medulla (20 %) which are completely different in embryological, histological and functional aspects. Divides into two parts; cortex (80 % of the gland and medulla (20 %) which are completely different in embryological, histological and functional aspects. Cortical cells develop from mesoderm and secrete corticosteroid hormones. Cortical cells develop from mesoderm and secrete corticosteroid hormones. Medulla originates from the ectodermal neural crest cell and secretes catecholamines. Medulla originates from the ectodermal neural crest cell and secretes catecholamines. Divides into two parts; cortex (80 % of the gland and medulla (20 %) which are completely different in embryological, histological and functional aspects. Divides into two parts; cortex (80 % of the gland and medulla (20 %) which are completely different in embryological, histological and functional aspects. Cortical cells develop from mesoderm and secrete corticosteroid hormones. Cortical cells develop from mesoderm and secrete corticosteroid hormones. Medulla originates from the ectodermal neural crest cell and secretes catecholamines. Medulla originates from the ectodermal neural crest cell and secretes catecholamines.

Blood circulation Arteries give rise to subcapsular plexus which gives: Arteries give rise to subcapsular plexus which gives: –Short cortical arteries  network of sinusoidal fenestrated capillaries  venous plexus  small venules  suprarenal medulla  suprarenal vein. –Long cortical arteries  medulla to form network of capillaries  renal vein. Arteries give rise to subcapsular plexus which gives: Arteries give rise to subcapsular plexus which gives: –Short cortical arteries  network of sinusoidal fenestrated capillaries  venous plexus  small venules  suprarenal medulla  suprarenal vein. –Long cortical arteries  medulla to form network of capillaries  renal vein.

Suprarenal cortex Synthesizes and secretes steroid (corticosteroid) hormones which are derived from cholesterol. Synthesizes and secretes steroid (corticosteroid) hormones which are derived from cholesterol. Derived from mesoderm. Derived from mesoderm. Histologically, divided into three concentric zones: zona glomerulosa, zona fasciculata and zona reticularis. Histologically, divided into three concentric zones: zona glomerulosa, zona fasciculata and zona reticularis. Synthesizes and secretes steroid (corticosteroid) hormones which are derived from cholesterol. Synthesizes and secretes steroid (corticosteroid) hormones which are derived from cholesterol. Derived from mesoderm. Derived from mesoderm. Histologically, divided into three concentric zones: zona glomerulosa, zona fasciculata and zona reticularis. Histologically, divided into three concentric zones: zona glomerulosa, zona fasciculata and zona reticularis.

Zona glomerulosa Forms the outer layer of the suprarenal cortex and represent 13 % of the total volume of the gland. Forms the outer layer of the suprarenal cortex and represent 13 % of the total volume of the gland. Consists of cords and clusters of small columnar or pyramidal cells. Consists of cords and clusters of small columnar or pyramidal cells. These cells have small dark nuclei, acidophilic cytoplasm containing: numerous SER, short mitochondria with shelf-like cristae, well-developed Golgi complex, abundant RER, free ribosomes and lipid droplets and short microvilli. These cells have small dark nuclei, acidophilic cytoplasm containing: numerous SER, short mitochondria with shelf-like cristae, well-developed Golgi complex, abundant RER, free ribosomes and lipid droplets and short microvilli. Forms the outer layer of the suprarenal cortex and represent 13 % of the total volume of the gland. Forms the outer layer of the suprarenal cortex and represent 13 % of the total volume of the gland. Consists of cords and clusters of small columnar or pyramidal cells. Consists of cords and clusters of small columnar or pyramidal cells. These cells have small dark nuclei, acidophilic cytoplasm containing: numerous SER, short mitochondria with shelf-like cristae, well-developed Golgi complex, abundant RER, free ribosomes and lipid droplets and short microvilli. These cells have small dark nuclei, acidophilic cytoplasm containing: numerous SER, short mitochondria with shelf-like cristae, well-developed Golgi complex, abundant RER, free ribosomes and lipid droplets and short microvilli.

Function of zona glomerulosa Secretes meniralocorticoids (e.g. aldosterone and deoxycorticosterone). Secretes meniralocorticoids (e.g. aldosterone and deoxycorticosterone). This hormone  plasma sodium concentration by  its reabsorption in distal convoluted tubules in kidneys and  its secretion in sweat and salivary glands. This hormone  plasma sodium concentration by  its reabsorption in distal convoluted tubules in kidneys and  its secretion in sweat and salivary glands. Its synthesis and secretion is under stimulation of angiotensin II. Its synthesis and secretion is under stimulation of angiotensin II. Secretes meniralocorticoids (e.g. aldosterone and deoxycorticosterone). Secretes meniralocorticoids (e.g. aldosterone and deoxycorticosterone). This hormone  plasma sodium concentration by  its reabsorption in distal convoluted tubules in kidneys and  its secretion in sweat and salivary glands. This hormone  plasma sodium concentration by  its reabsorption in distal convoluted tubules in kidneys and  its secretion in sweat and salivary glands. Its synthesis and secretion is under stimulation of angiotensin II. Its synthesis and secretion is under stimulation of angiotensin II.

Zona fasciculata Forms the intermediate layer of the suprarenal cortex and represent 80 % of the total volume of the gland. Forms the intermediate layer of the suprarenal cortex and represent 80 % of the total volume of the gland. Consists of columns of polyhedral cells arranged longitudinally, with capillary sinusoids lying between them. Consists of columns of polyhedral cells arranged longitudinally, with capillary sinusoids lying between them. These cells are larger than the zona glomerulosa cells, with slight acidophilic cytoplasm which appears vacuolated because it has lipid droplets. These cells are larger than the zona glomerulosa cells, with slight acidophilic cytoplasm which appears vacuolated because it has lipid droplets. The cells have spherical mitochondria, extensive SER, some RER, lysosomes and lipofuscin pigments The cells have spherical mitochondria, extensive SER, some RER, lysosomes and lipofuscin pigments Forms the intermediate layer of the suprarenal cortex and represent 80 % of the total volume of the gland. Forms the intermediate layer of the suprarenal cortex and represent 80 % of the total volume of the gland. Consists of columns of polyhedral cells arranged longitudinally, with capillary sinusoids lying between them. Consists of columns of polyhedral cells arranged longitudinally, with capillary sinusoids lying between them. These cells are larger than the zona glomerulosa cells, with slight acidophilic cytoplasm which appears vacuolated because it has lipid droplets. These cells are larger than the zona glomerulosa cells, with slight acidophilic cytoplasm which appears vacuolated because it has lipid droplets. The cells have spherical mitochondria, extensive SER, some RER, lysosomes and lipofuscin pigments The cells have spherical mitochondria, extensive SER, some RER, lysosomes and lipofuscin pigments

Function of zona fasciculata Secretes glucocorticoids (e.g. cortisol, cortisone and corticosterone). Secretes glucocorticoids (e.g. cortisol, cortisone and corticosterone). These hormones affect carbohydrate, fat and protein metabolism resulting in increase in glucose and amino acids levels and movement of fat. These hormones affect carbohydrate, fat and protein metabolism resulting in increase in glucose and amino acids levels and movement of fat. They also suppress inflammatory responses in allergic reactions. They also suppress inflammatory responses in allergic reactions. Their synthesis and secretion is under stimulation of ACTH of pituitary gland. Their synthesis and secretion is under stimulation of ACTH of pituitary gland. Secretes glucocorticoids (e.g. cortisol, cortisone and corticosterone). Secretes glucocorticoids (e.g. cortisol, cortisone and corticosterone). These hormones affect carbohydrate, fat and protein metabolism resulting in increase in glucose and amino acids levels and movement of fat. These hormones affect carbohydrate, fat and protein metabolism resulting in increase in glucose and amino acids levels and movement of fat. They also suppress inflammatory responses in allergic reactions. They also suppress inflammatory responses in allergic reactions. Their synthesis and secretion is under stimulation of ACTH of pituitary gland. Their synthesis and secretion is under stimulation of ACTH of pituitary gland.

Zona reticularis Forms the inner layer of the suprarenal cortex and represent 7 % of the total volume of the gland. Forms the inner layer of the suprarenal cortex and represent 7 % of the total volume of the gland. Consists of anastomosing cords of small polyhedral cells. Consists of anastomosing cords of small polyhedral cells. These cells resemble those of zona fasciculata but smaller in size, having darkly stained acidophilic cytoplasm with fewer lipid droplets and large amounts of lipofuscin pigments. These cells resemble those of zona fasciculata but smaller in size, having darkly stained acidophilic cytoplasm with fewer lipid droplets and large amounts of lipofuscin pigments. Forms the inner layer of the suprarenal cortex and represent 7 % of the total volume of the gland. Forms the inner layer of the suprarenal cortex and represent 7 % of the total volume of the gland. Consists of anastomosing cords of small polyhedral cells. Consists of anastomosing cords of small polyhedral cells. These cells resemble those of zona fasciculata but smaller in size, having darkly stained acidophilic cytoplasm with fewer lipid droplets and large amounts of lipofuscin pigments. These cells resemble those of zona fasciculata but smaller in size, having darkly stained acidophilic cytoplasm with fewer lipid droplets and large amounts of lipofuscin pigments.

Function of zona reticularis Secretes androgens (e.g. dehydro- epiandrosterone). Secretes androgens (e.g. dehydro- epiandrosterone). These hormones have weak masculinizing effect which is negligible under normal condition. These hormones have weak masculinizing effect which is negligible under normal condition. Their synthesis and secretion is under stimulation of ACTH of pituitary gland. Their synthesis and secretion is under stimulation of ACTH of pituitary gland. Secretes androgens (e.g. dehydro- epiandrosterone). Secretes androgens (e.g. dehydro- epiandrosterone). These hormones have weak masculinizing effect which is negligible under normal condition. These hormones have weak masculinizing effect which is negligible under normal condition. Their synthesis and secretion is under stimulation of ACTH of pituitary gland. Their synthesis and secretion is under stimulation of ACTH of pituitary gland.

Suprarenal medulla Occupies the central portion of the suprarenal glands and is totally covered by the cortical part. Occupies the central portion of the suprarenal glands and is totally covered by the cortical part. Develops from the ectodermal neural crest cells. Develops from the ectodermal neural crest cells. Consists of two cell populations: chromaffin cells and sympathetic ganglion cells. Consists of two cell populations: chromaffin cells and sympathetic ganglion cells. Occupies the central portion of the suprarenal glands and is totally covered by the cortical part. Occupies the central portion of the suprarenal glands and is totally covered by the cortical part. Develops from the ectodermal neural crest cells. Develops from the ectodermal neural crest cells. Consists of two cell populations: chromaffin cells and sympathetic ganglion cells. Consists of two cell populations: chromaffin cells and sympathetic ganglion cells.

Chromaffin cells Large epithelioid cells, arranged in clusters or short cords. Large epithelioid cells, arranged in clusters or short cords. Contain catecholamines in membrane- bound vesicles which are released by exocytosis under sympathetic stimulation. Contain catecholamines in membrane- bound vesicles which are released by exocytosis under sympathetic stimulation. They are of two types: epinephrine and norepinephrine secreting cells. They are of two types: epinephrine and norepinephrine secreting cells. The norepinephrine granules are more dense than the epinephrine granules. The norepinephrine granules are more dense than the epinephrine granules. Large epithelioid cells, arranged in clusters or short cords. Large epithelioid cells, arranged in clusters or short cords. Contain catecholamines in membrane- bound vesicles which are released by exocytosis under sympathetic stimulation. Contain catecholamines in membrane- bound vesicles which are released by exocytosis under sympathetic stimulation. They are of two types: epinephrine and norepinephrine secreting cells. They are of two types: epinephrine and norepinephrine secreting cells. The norepinephrine granules are more dense than the epinephrine granules. The norepinephrine granules are more dense than the epinephrine granules.

Function of medulla Synthesis and release of adrenaline and noradrenaline. Synthesis and release of adrenaline and noradrenaline.  Respiratory rate with bronchodilatation.  Respiratory rate with bronchodilatation.  Heart rate and cardiac output.  Heart rate and cardiac output.  Blood pressure.  Blood pressure.  lipolysis and glycogenolysis.  lipolysis and glycogenolysis. Action of what is called “ fight and flight ” Action of what is called “ fight and flight ” Synthesis and release of adrenaline and noradrenaline. Synthesis and release of adrenaline and noradrenaline.  Respiratory rate with bronchodilatation.  Respiratory rate with bronchodilatation.  Heart rate and cardiac output.  Heart rate and cardiac output.  Blood pressure.  Blood pressure.  lipolysis and glycogenolysis.  lipolysis and glycogenolysis. Action of what is called “ fight and flight ” Action of what is called “ fight and flight ”

Some Clinical Correlations Addison ’ s disease: Addison ’ s disease: –  secretion of adrenocortical hormones because of destruction of adrenal cortex. –Caused by TB, autoimmune disease or any chronic disease. –Fatal disease. Addison ’ s disease: Addison ’ s disease: –  secretion of adrenocortical hormones because of destruction of adrenal cortex. –Caused by TB, autoimmune disease or any chronic disease. –Fatal disease.

Cushing ’ s disease: Cushing ’ s disease: –Due to small tumor in the anterior pituitary leading to  secretion of ACTH, which causes enlargement and hypertrophy of suprarenal cortex which secretes more cortisol that causes obesity, impotance in males and amenorrhea in females. Cushing ’ s disease: Cushing ’ s disease: –Due to small tumor in the anterior pituitary leading to  secretion of ACTH, which causes enlargement and hypertrophy of suprarenal cortex which secretes more cortisol that causes obesity, impotance in males and amenorrhea in females. Some Clinical Correlations

LocationLocation A small conical-shaped endocrine gland lying in the midline attached to the roof of the diencephalon of the brain. A small conical-shaped endocrine gland lying in the midline attached to the roof of the diencephalon of the brain. Its dimensions are 7 x 4 mm and its weight is 120 mg. Its dimensions are 7 x 4 mm and its weight is 120 mg. A small conical-shaped endocrine gland lying in the midline attached to the roof of the diencephalon of the brain. A small conical-shaped endocrine gland lying in the midline attached to the roof of the diencephalon of the brain. Its dimensions are 7 x 4 mm and its weight is 120 mg. Its dimensions are 7 x 4 mm and its weight is 120 mg.

Connective Tissue Stroma The gland is covered by pia mater which forms its capsule, that sends connective tissue septa dividing the gland into complete lobules. The gland is covered by pia mater which forms its capsule, that sends connective tissue septa dividing the gland into complete lobules. Blood vessels and sympathetic nerves enter the gland via the connective tissue septa. Blood vessels and sympathetic nerves enter the gland via the connective tissue septa. The gland is covered by pia mater which forms its capsule, that sends connective tissue septa dividing the gland into complete lobules. The gland is covered by pia mater which forms its capsule, that sends connective tissue septa dividing the gland into complete lobules. Blood vessels and sympathetic nerves enter the gland via the connective tissue septa. Blood vessels and sympathetic nerves enter the gland via the connective tissue septa.

Parenchymal cells Two types of cells present in the pineal gland the first is pinealocytes: Two types of cells present in the pineal gland the first is pinealocytes: –They form the majority of cells. –Slightly basophilic cells, having spherical lobulated nucleus with one nucleolus. The cytoplasm has SER, RER, small Golgi apparatus, numerous mitochondria, small secretory vesicles containing electron-dense core. –They have one or two long processes with terminal dilatation near other cells or capillaries. Two types of cells present in the pineal gland the first is pinealocytes: Two types of cells present in the pineal gland the first is pinealocytes: –They form the majority of cells. –Slightly basophilic cells, having spherical lobulated nucleus with one nucleolus. The cytoplasm has SER, RER, small Golgi apparatus, numerous mitochondria, small secretory vesicles containing electron-dense core. –They have one or two long processes with terminal dilatation near other cells or capillaries.

Glial (interstitial) cells: Glial (interstitial) cells: –They form a network around the pinealocytes, and considered as astrocytes. –They have small dark nuclei, well- developed RER, glycogen droplets and long cellular processes. Glial (interstitial) cells: Glial (interstitial) cells: –They form a network around the pinealocytes, and considered as astrocytes. –They have small dark nuclei, well- developed RER, glycogen droplets and long cellular processes. Parenchymal cells

Brain Sands The pineal gland contains concentrations of calcium phosphate and carbonate deposited in concentric rings around an organic matrix. The pineal gland contains concentrations of calcium phosphate and carbonate deposited in concentric rings around an organic matrix. They appears in childhood and increase with age. They appears in childhood and increase with age. Their function is unknown but they are used as a radiological diagnostic tool. Their function is unknown but they are used as a radiological diagnostic tool. The pineal gland contains concentrations of calcium phosphate and carbonate deposited in concentric rings around an organic matrix. The pineal gland contains concentrations of calcium phosphate and carbonate deposited in concentric rings around an organic matrix. They appears in childhood and increase with age. They appears in childhood and increase with age. Their function is unknown but they are used as a radiological diagnostic tool. Their function is unknown but they are used as a radiological diagnostic tool.

Function of pineal gland Secretion of melatonin, serotonin and indalomine. Secretion of melatonin, serotonin and indalomine. It has circadian rhythm (melatonin  in darkness and  during day light). It has circadian rhythm (melatonin  in darkness and  during day light). Retina  sympathetic innervation of the gland  stimulate secretion. Retina  sympathetic innervation of the gland  stimulate secretion. Melatonin influence secretion of other endocrine glands through hypothalamus. Melatonin influence secretion of other endocrine glands through hypothalamus. Secretion of melatonin, serotonin and indalomine. Secretion of melatonin, serotonin and indalomine. It has circadian rhythm (melatonin  in darkness and  during day light). It has circadian rhythm (melatonin  in darkness and  during day light). Retina  sympathetic innervation of the gland  stimulate secretion. Retina  sympathetic innervation of the gland  stimulate secretion. Melatonin influence secretion of other endocrine glands through hypothalamus. Melatonin influence secretion of other endocrine glands through hypothalamus.

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