Endocrine Organs
Hormone
Mechanism
Paracrine
Autocrine
Endocrine
Compounds
Steroid
Amino acids and arachidonic acid analogs
Peptides and proteins
Luteinizing hormone (LH)
Antidiuretic hormone (ADH)
Follicle-stimulating hormone (FSH)
Oxytocin
Adrenocorticotropic hormone (ACTH)
Interleukins
Growth hormone (GH)
Glucagon
Various growth factors
Insulin
Gonadal steroids
Adrenocortical steroids
Prostaglandins
Prostacyclins
Catecholamines
Leukotrienes
Thyroid hormones
Epinephrine
Norepinephrine
Receptor
Cell surface receptors
Intracellular receptors
Regulation
Positive feedback
Negative feedback
Pituitary gland (Hypophysis)
Thyroid gland
Pineal gland
Adrenal glands
Parathyroid glands
Hypothalamus
Gross structure
Anterior lobe (adenohypophysis)
Posterior lobe (neurohypophysis)
Embryologic origin
Ectoderm of the oropharynx
Rathke's pouch
Composition
Pars distalis
Pars intermedia
Pars tuberalis
Embryologic origin
Composition
Neuroectoderm of the floor fo the third ventricle (diencephalon)
Pars nervosa
Infundibulum
Forms hypothalamohypophyseal tracts
Blood supply
Superior hypophyseal arteries
Inferior hypophyseal arteries
Continuous with median eminence
Arise from internal carotid arteries
Supply
Pars tuberalis
Median eminence
Infundibulum
Arise from internal carotid arteries
Supply pars nervosa
Tropic hormones
ACTH
Thyroid-stimulating hormone (TSH)
FSH
LH
Lactotropes (PRL cells, mammotropes)
Corticotropes (ACTH cells)
Somatotropes (GH cells)
Gonadotropes (FSH, LH cells)
Thyrotropes (TSH cells)
Follicular stellate cells
Star-like
Form cell clusters or small follicles
Do not produce hormones
Interconnected with connexin-43
Small cystic cavities
Parenchymal cells
Lining on the colloid follicles
Derived from folliculo-stellate cells or hormone secreting cells
Function unclear
Highly vascular region
Herring bodies
Hormones
Oxytocin
ADH
Location
Middle of the base of brain
Encapsulates ventral portion of 3rd ventricle
Functions
Major controlling centers of autonomic nerve system
Coordinates endocrine function
Hormones
Dopamine
Corticotropin-releasing hormone (CRH)
Somatostatin
Gonadotropin-releasing hormone (GnRH)
Growth hormone-releasing hormone (GHRH)
Thyrotropin-releasing hormone (TRH)
Regulates daily rhythm
Developed from neuroectoderm of posterior portion of roof of diencephalon
Located at posterior wall of 3rd ventricle
Melatonin
Corpora arenacea (Brain sand)
Parenchymal cells
Pinealocytes
Interstitial (glial) cells
Chief cells
Large deeply infolded nucleus
lipid droplets in cytoplasm
Light impulse inhibits production of melatonin
Inhibits gonadal hormone release (Inhibit GnRH release)
Features
Bilobate connected by isthmus
In anterior neck region adjacent to larynx and trachea
Thyroid follicle
Colloid
Epithelium
Functional unit
Enzymes
Glycoproteins
Thyroglobulin
Inactive storage form of hormone
Follicular cells (Principle cells)
Parafollicular cells (C cells)
Lipid droplets and PAS-positive droplets
Both secretory and absorptive cell morphology
Slightly basophilic
Produces T3 (Triiodothyronine), T4 (Tetraiodothyronine)
No exposure to the follicle lumen
Secrete calcitonin (thyrocalcitonin)
Located in the periphery of epithelium
Essential to normal growth and development
Antagonist to parathyroid hormone (PTH)
Suppressing osteoclasts
Regulated by blood calcium levels
Regulate cell and tissue metabolism, heat production
Influence body growth and development
Regulated by TSH from anterior pituitary
Poorly defined lobules
Essential for life
Epithelial cells
Principle (Chief) cells
Oxyphil cells
Small, polygonal cells with centrally located nucleus
Synthesis, storage and secretion of PTH
Major type of parenchymal cells
Round, larger than principle cells
Acidophilic cytoplasm
Parathyroid hormone-related protein (PTHrP)
Secretory parenchymal tissue
Cortex (Steroid secreting)
Medulla (Catecholamine secreting)
Norepinephrine
Blood supply
Fenestrated cortical sinusoidal capillaries
Medullary arterioles
Capsular capillaries
Zonation
Zona fasciculata
Zona reticularis
Zona glomerulosa
Closely packed ovoid clusters
small and columnar or pyramidal cells
15% cortical volume
large and polyhedral cells
Long straight cords, separated by sinusoidal capillaries
80% cortical volume
5-7% cortical volume
Arranged anastomosing cords, separated by fenestrated capillaries
Glucocorticoids
Gonadocorticoids
Mineralocorticoids
Epinephrine
Aldosterone
Corticosterone
Cortisol (major)
Dehydroepiandrosterone (DHEA)
Dehydroepiandrosterone sulfate (DHEAS)
Androstenedione
Cells of adrenal medulla
Chromaffin cells
Ganglion cells
Modified neurons
Lacking axonal process
Pale-stained epithelioid cells
Large polygonal cells
Located closely to adrenomedullary vein