Location n A retroperitoneal gland lies at the

Location n A retroperitoneal gland, lies at the superior pole of the kidney, embedded in adipose tissue. n The right gland is pyramidal in shape while the left one is crescent-shaped. n Its dimensions are 1 x 2 x 5 cm and its weight is 7 -10 gm. n Supplied by 3 arteries and drained by one vein.

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

Blood supply of the gland It has one of the richest blood supply of the body. n Supplied by three arteries: n – Superior suprarenal artery from inferior phrenic artery. – Middle suprarenal artery from aorta. – Inferior suprarenal artery from renal artery. n 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 medulla (20 %) which are completely different in embryological, histological and functional aspects. n Cortical cells develop from mesoderm and secrete corticosteroid hormones. n Medulla originates from the ectodermal neural crest cell and secretes catecholamines. n

Blood circulation n 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. n Derived from mesoderm. n Histologically, divided into three concentric zones: zona glomerulosa, zona fasciculata and zona reticularis. n

Zona glomerulosa n n n 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. These cells have small dark nuclei, acidophilic cytoplasm containing: numerous SER, short mitochondria with shelf-like cristae, welldeveloped Golgi complex, abundant RER, free ribosomes and lipid droplets and short microvilli.

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

Zona fasciculata n n 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. 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

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

Zona reticularis Forms the inner layer of the suprarenal cortex and represent 7 % of the total volume of the gland. n Consists of anastomosing cords of small polyhedral cells. n 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. n

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

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

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

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

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

Some Clinical Correlations n 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.

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

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

Parenchymal cells n 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.

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

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

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

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