ENDOCRINE SYSTEM ENDOCRINE SYSTEM

Transcription

1 Endocrine system consists of organs that produce and secrete hormones "endocrine" = internal secretion into capillaries Hormones carried by the blood to another organ; exert effects Hormones manipulate specific enzymes of metabolic processes directly or indirectly activating the genes 1 Pituitary gland a. General aspects (1) Three different regions of separate origin; almost totally unrelated anterior lobe anterior pituitary, adenohypophysis intermediate lobe pars intermedia posterior lobe posterior pituitary, neurohypophysis Pituitary Gland Posterior lobe Neurohypophysis posterior pituitary Infundibulum Hypothalamus Paraventricular nucleus OT & ADH production Pars tuberalis Supraoptic nucleus OT & ADH production Optic chiasma Intermediate lobe Pars intermedia Anterior lobe Adenohypophysis anterior pituitary 2

2 Pituitary gland is located on the underside of the diencephalon portion of the brain, just posterior to the optic chiasma where the two optic tracts cross Spherical ; human adults, about 7 mm in diameter. 3 Neurohypophysis --composed of neural tissue of the CNS white matter Contains glial cells and capillaries. Glial cells same as earlier; called pituicytes. No neuron bodies 4

3 Skip slide Nerve fibers, axons of neurons in the diencephalon paraventricular nucleus supraoptic nucleus. Pass down the stalk of the neurohypophysis infundibulum; ; end in the neurohypophysis Axons terminate on the capillaries in that tissue Nuclei generate impulses; sent to the neurohypophysis Axon terminals release oxytocin or antidiuretic hormone (aka, ADH or vasopressin) into blood. 5 Adenohypophysis (1) Composed of two different forms of glandular epithelial tissue. (2) Anterior lobe Pars distalis and pars tuberalis. Packed endocrine glandular epithelial cells, sinusoids and capillaries. Three types of endocrine cells Pituitary Gland Paraventricular nucleus OT & ADH production Supraoptic nucleus OT & ADH production Hypothalamus Infundibulum Pars tuberalis Optic chiasma Intermediate lobe Pars intermedia Posterior lobe Neurohypophysis posterior pituitary Anterior lobe Adenohypophysis anterior pituitary 6

4 Types of endocrine cells present 1. Chromophil(ic) cells: cytoplasm stain with H&E Acidophilic Cells; a above (pink to red; Cells; large and spherical. secrete; Somatotropin (growth hormone) Prolactin (lactogenic hormone.) 7 Basophilic Cells; b above light dull blue-gray; small ;cuboidal. secrete; Thyrotropin (thyroidstimulating hormone) Lutenizing (interstitialcell-stimulating) hormone, FSH (follicle stimulating hormone) and ACTH (adrenocorticotropic hormone) 8

5 Chromophobe cells: cytoplasm does not stain with H&E. c above Nucleus surrounded by space. Probably are immature cells. 9 Intermediate lobe (pars intermedia) Basophilic glandular epithelial tissue in clumps (follicles) and sacs (vesicles) between pars distalis and posterior pituitary gland secretes melanocyte-stimulating hormone, aka, MSH. Not significant in humans 10

6 Thyroid gland Composed (about 95%) of thyroid follicles between thyroid follicles is interstitial connective tissue containing small blood vessels and parafollicular cells adipose tissue is present in and around CT 11 12

7 Thyroid follicle Thyroid follicle is a hollow sac; simple endocrine glandular epithelium Inactive follicles: cells are flat; between cuboidal and squamous cells; aka, low-cuboidal Moderately active follicles: cuboidal cells: Very active follicles: low-columnar cells: 13 Follicle Lumen contains a colloid Colloidal dispersion of a large protein molecule Protein eosinophilic Protein binds the hormone for storage Follicle produces thyroxin (tetra-iodothyronine); Active form of the molecule, within the cells of the body where it acts, is triiodothyronine. 14

8 15 Adrenal gland General aspects next to the kidney ; superior kidney. Cortex and medulla medulla is a single, interior, mass of tissue cortex is a relatively thick complex layer surrounding the medulla outermost ; thin capsule of dense C.T. 16

9 17 Adrenal medulla Clumps or cords; large lightly basophilic cells; scattered small blood vessels. Hormones epinephrine (adrenaline) and norepinephrine (noradrenaline) by direct stimulation of the sympathetic part of the autonomic nervous system. 18

10 Adrenal cortex --divided into 3 layers; hormones produced are all steroids Zona reticularis (a) innermost next to medulla. (b) cells are in a network of branching cords, with sinusoids in-between. (c) Cells are spherical to cuboidal in shape, and their cytoplasm stains well with eosin cords are about 1 cell thick. (d) Androgens or androgen precursors, in both males and females

11 Zona fasciculata (f) (a) middle; thickest. (b) Cells in parallel sheets, perpendicular to surface capillaries or sinusoids lie between the sheets, hard to see. (c) Cells are spherical to cuboidal ; stains very lightly with H&E tiny spherical holes; represent storage vacuoles. (d) Glucocorticoids i.cortisol ii. Cortisone; one most commonly administered therapeutically

12 Zona glomerulosa (g) (a) outermost ; thinnest (b) Layer is composed of spherical clumps of endocrine cells; capillaries or sinusoids between layer is one to two clumps (glomeruli) thick. Glomeruli are not hollow. (c) Cuboidal to low columnar in shape cytoplasmic staining is intermediate between other layers. (d) Mineralocorticoids Aldosterone; regulates Na+ and water balance

13 Medulla Cortex R F G Capsule 25