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19 Cards in this Set
- Front
- Back
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Adrenal Glands location, Regions
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aka suprarenal glands
Location: At the superior poles of the kidneys, embedded in adipose tissue and covered with thick CT capsule, about 10g Regions (both embryologically, histologically and functionally separate): a) Cortex - responds to ACTH from anterior pituitary to release steroid hormones b) Medulla - releases catecholamines and not regulated by anterior pituitary |
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Layers of Cortex
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Zona glomerulosa
Zona fasciculata Zona reticularis Cortex stains lighter similar to fatty, lipid filled adipocytes |
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Medulla expulsion
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mediated by prominent smooth muscle fibers around large adrenal vein that contract to expel medullary material
arteries - muscle is circular and in tunica media; veins - muscle is longitudinal and in tunica adventitia |
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Blood Supply to Adrenals
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Superior, Middle and Inferior Suprarenal arteries with single central venous output
Right suprarenal vein drains to IV, Left suprarenal Vein to left renal vein Adrenal capsule arteries give off short cortical arteries (feed cortex via sinusoidal capillary bed in zona glomerulosa) and long medullary arteries (bypass cortex to deliver blood to medulla) Sinusoidal beds in zona glomerulosa (oxygenated) and zona reticularis (least oxygenated) Medulla - arterial blood from medullary arterioles and venous blood from cortical sinusoids |
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Most sensitive area to hypoxia
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Zona reticularis - deepest cortex zone, receives least amount of oxygenated blood
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Development of Adrenal Gland
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Cortex - from epithelial cells of mesoderm
Medulla - from neural crest cells of ectoderm Fetal cortex - mesodermal cells migrate and surround medulla cells Fetal medulla - cells from SNS ganglia are enclosed by cortex but not organized Permanent cortex - develops outside fetal cortex and develops into 2 zonses, permanent visible by 4 months with fetal dissolution, Zona reticularis develops by 3rd year Fetal adrenal gland interacts with placenta to secrete steroids |
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Adrenal Cortex Role, Zones, Hormones
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Parenchymal cells that synthesize and secrete steroid hormones without storing them
Zones: a) Zona glomerulosa - makes mineralocorticoids (aldosterone) b) Zona fasciculata - makes glucocorticoids (cortisol) c) Zona reticularis - makes androgens (DHEA and androstenedione) Hormones: Mineralocorticoids, Glucocorticoids, Androgens All hormones synthesized from cholesterol via LDL uptake from blood, when stimulated, stored cholesterol freed to use to make hormones. DO NOT STORE PREFORMED HORMONES secrete contents basolaterally |
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Steroid hormone sytnhesis
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Cholesterol in blood in LDL enters cortex cell and stored. ACTH stimulation promotes hormone synthesis in SER and P450 complexes
Once made, steroid hormones diffuse across cell membrane to blood stream (NO EXOCYTOSIS) Act via intracellular receptors as transcription factors to produce slow, long lasting systemic effects |
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Zona Glomerulosa Role, Stimulators, Hormone, Hormone Function, Feedback, Histology, Contents
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Topmost layer of cortex, 15% of cortex
Cells stimulated by Angiotensin II and ACTH Role: Produce and secrete mineralocorticoids (aldosterone mostly, but some deoxycorticosterone) Function: Hormones control fluid and electrolyte balance. Aldosterone targets DCT cells to increase Na+ reabsorption (water with it to up BP/ blood volume) and decrease K+ reabsorption. Targets all tissues where Na+ can be conserved (gastric mucosa, salivary glands, sweat gland) Feedback: RAAS system, Juxtaglomerular cells at renal corpuscle near afferent arteriole near macula densa will release renin with low serum Na+/BP which is converted to angiotensinogen to AgI to AgII. AgII to ZG to produce aldosterone Histology: resemble glomeruli, small columnar cells in tight clusters Contents: All cells have abundant SER, well developed Golgi, gap jxns and desmosomes Activated by LOW salt or LOW BP |
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Zona Fasciculata Role, Stimulators, Hormone, Hormone Function, Feedback, Histology, Contents
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65-80% of cortex (BIGGEST PART)
Role: Produce and secrete glucocorticoids (CORTISOL) which act on carb, fat and protein metabolism Stimulators: ACTH Hormones: Cortisol and corticosterone Hormone function: Many fxns and tissues a) Liver - anabolic effect - promote FFA, protein and glucose uptake for GLYCOGEN synthesis b) Other tissues - catabolic effect - stimulates protein or lipid breakdown Feedback: Cortisol inhibits CRH (hypothalamus) and ACTH (anterior pituitary) release. MUST taper glucocorticoid treatments in pts due to suppression over time and adrenal wasting and anterior pituitary wasting Histology: Longer cords of larger cells separated by fenestrated sinusoidal capillaries, MANY lipid droplets and extensive SER so looks like a sponge and cells often called spongiocytes |
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Pharmacologic effect of high dose cortisol
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a) Anti-inflammatory (inhibits macrophages and granulocyte migration)
b) Immunosuppresant by lowering lymphocyte counts Would only see if have tumor or very high ACTH levels otherwise |
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Zona Reticularis Role, Stimulators, Hormone, Hormone Function, Feedback, Histology, Contents
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Innermost zone, 10% cortex
Role: Produce androgen sex hormones androsterone and DHEA. Stimulators: ACTH Hormones: Androstenedione, DHEA Hormone function: Weak, masculinizing hormones that are converted to testosterone peripherally. Not much concern b/c most testosterone from ovaries/testes Feedback: hypothalamus and pituitary via CRH and ACTH (most feedback here via cortisol but some mild effect) Histology: smaller cells, IRREGULAR cords with WIDE capillaries, FEWER lipid droplets but well developed SER, cells nearest medulla are often dark indicating degenerating cells b/c of poor blood supply |
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Stress effect on cortex
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Stress increases CRH-ACTH release and leads to cortex hypertrophy
Lack of stimulation (chronic glucocorticoid use, hypophisectomy) leads to atrophy so must taper meds |
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Addison's Disease and Cushing's Disease Pathophysiology and Symptoms
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Addison's Disease - decreased secretion of adrenocortical hormones most often an autoimmune process (primary), lethal if steroid treatment not provided
Sx: weight loss, muscle weakness, fatigue, low BP Cushing's Disease (hyperadrenocorticism) - increased ACTH causes enlargement of suprarenal gland and cortisol overproduction (secondary) Sx: obesity (esp face, neck, trunk), impotency and amenorrhea |
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Adrenal Medulla Role, Cells, Cell Role, Blood supply
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NO obvious demarcation btw zona reticularis and medulla
Modified sympathetic ganglion completely invested in adrenal cortex Cells: Chromaffin cells innervated by myelinated PREsynaptic SNS ganglion cells (UNIQUE) Chromaffin cells - post synaptic cells that secrete epinephrine or norepinephrine upon AcH stimulation. Ganglion cells - innervate adrenal cortex to modulate secretory activity and innervate blood vessels Blood supply: capillaries and sinusoids with both arterial (long arteries) and venous blood (via sinusoids) |
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Chromaffin cell structure, Hormone release, Response
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Large, epitheloid like cells with ANS innervation. Ach increases Ca++ to cause release of Epi/Norepi.
Technically modified postganglionic SNS neurons without dendrites or axons and have a secretory function Steroids from AC that diffuse down inhibit dendrite and axon formation in chromaffin cells (in isolated cultures grow them) 2 populations called pheochromocytes High density cells - Norepi Low density cells - Epi - MOST ARE THIS Hormone release: PREFORMED (unlike cortex hormone) catecholamines from tyrosine stored in chromaffin cells vesicles, when stimulated via Ach from cholinergic nerve ending, depolarization, causing Ca++ influx, released to blood for "fight or flight" response (also release enkephalins and ATP) Response: Increased O2 used, heat produced, glucose release, mobilize fat, HR, BP up, alertness up |
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Endocrine pancreas Structure and role, Histology, Cells
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Diffuse organ that secretes hormones to regulate blood glucose levels
Organized in Islets of Langerhans (of few to many hundred cells) that are 1% overall pancreas size and cells are counterparts of enteroendocrine cells of GI mucosa (except B Islet cells) Integrated network of fenestrated capillaries Histology: lighter patches in darker pancreas around (exocrine) Cells: Alpha cells - 20% - secrete glucagon Beta cells - 70% - secrete insulin Delta cells - 10% - secrete somatostatin Minor cells - PP (F) cells, D1 cells, EC cells A and D near periphery of islet, B at center |
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Function of Pancreatic Hormones (main 3)
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1) Insulin - stimulates:
glucose uptake from circulation by muscle and adipose tissue, storage of glucose via glycogen synthesis phosphorylation and use of glucose in glycolysis 2) Glucagon stimulates: Release of glucose to bloodstream Gluconeogenesis and Glycogenolysis Reciprocal to insulin 3) Somatostatin Inhibit insulin and glucagon secretion Identical to hypothalmic somatostatin |
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Mechanisms of Insulin Activity to lower blood sugar
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Binds Alpha subunit of insulin receptor and activates the autophosphorylation (Tyr-P) of B unit (tyrosine kinase)
Activated insulin receptor stimulates DNA synthesis, protein synthesis and translocation of insulin dependent GLUT-4 transporter to plasma membrane GLUT-4 facilitates cellular glucose uptake Without this, diabetics lack glucose utilization |
