Pituitary Gland (Hypophysis)

Transcription

1 Endocrine Organs

2 Pituitary Gland (Hypophysis) Function o Production of hormones Location o Connected to the hypothalamus via an infundibulum situated within the sella turcica of the sphenoid bone Structure o Anterior pituitary gland (Adenohypophysis) 10x 40x Derived from the pharynx Pars distalis 75% of adenohypophysis Thin fibrous capsule Cords of epithelial cells interspersed with fenestrated capillaries Cells o Chromophils Secretory cells with cytoplasmic granules Identified by affinity for dyes Acidophils Somatotrophs (m/c) o Growth hormone Mammotrophs o Prolactin Basophils Gonadotrophs o Follicle stimulating hormone o Luteinizing hormone Corticotrophs o Adrenocorticotropic hormone Thyrotropic o Thyroid stimulating hormone o Chromophobes Weakly stained Few secretory granules Stem cells Pars tuberalis Surrounds hypophyseal stalk (infundibulum) Cuboidal to columnar cells Well vascularized

3 Pars intermedia 10x 40x Cuboidal cell-lined cysts o Remnants of ectoderm Basophils o Pro-opiomelanocortin (prohormone) Forms melanocyte stimulating hormone o Posterior pituitary gland (Neurohypophysis) Pars nervosa No secretory cells Neural tissue o Axons of neurons from supraoptic and paraventricular nuclei of hypothalamus Produce vasopressin (ADH) and oxytocin in nuclei then travel to pars nervosa via axons to the Herring bodies o Herring bodies (i.e. axon terminals) ADH and Oxytocin released with neural stimulation o Pituitcytes - glial cells Infundibular stalk Video recording o Pituitary gland Microscope images o 4x o 10x

4 Adrenal (Suprarenal) Gland Function o Adrenal cortex mesoderm origin, secrete steroid hormones o Adrenal medulla neural crest origin; secrete epinephrine and norepinephrine Location o Retroperitoneal organs located on the superior poles of the kidneys, embedded in adipose tissue Structure o Capsule Dense connective tissue Produces septa into the gland as trabeculae o Bring in blood and lymph vessels and nerve fibers o o Adrenal Cortex Zona glomerulosa (15% of cortex) Just beneath the capsule Similar looking to glomeruli of the kidney Closely packed small columnar cells Produce mineralcorticoids (i.e. aldosterone) Zona fasciculata (65%-80% of cortex) Large polyhedral cells Longitudinal sinusoidal capillaries between cells Secrete glucocorticoids (i.e. cortisol) Zona reticularis (10% of cortex) Smaller cells Secrete dehydroepiandrosterone (DHEA) o Precursor to testosterone Adrenal Medulla Chromaffin cells Large, pale-staining polyhedral cells Modified sympathetic postganglionic neurons Granulated o Secrete epinephrine and norepinephrine Video recording o Adrenal gland

5 Microscope images o Adrenal cortex 10x 40x o Adrenal medulla 10x 40x

6 Thyroid Gland Function o Secretion of hormones thyroxine (T3), tri-iodothyronine (T4) and calcitonin o Hormones are important for metabolism, growth and calcium regulation Location o Located in the cervical region anterior to the larynx o Consists of two lobes united by an isthmus; may have an accessory pyramidal lobe Structure o Capsule Dense connective tissue Form septa o Bring in blood and lymph vessels and nerve fibers o o Thyroid Follicles Surrounded by follicular cells (principle cells) Simple cuboidal to columnar epithelium Basophilic cytoplasm Secrete thyroglobulin o Binds with Iodide in colloid to from T3 and T4 Lumen filled with colloid Gelatinous fluid filled with precursors to thyroid hormone Parafollicular Cells (Clear cells or C cells) Lie in clusters outside the thyroid follicles Contain secretory granules Secrete hormone calcitonin o Decrease blood calcium Video recording o Thyroid and parathyroid glands Microscope images o Thyroid gland 4x 10x 40x

7 Parathyroid Gland Function o Produces parathyroid hormone which is involved in calcium regulation Location o Fur to six oval glands located on the posterior surface of the thyroid gland Structure o Capsule Dense connective tissue Form septa o Bring in blood and lymph vessels and nerve fibers Adipose tissue increases with age o Cells Chief cells Acidophilic cytoplasm with many granules o Secrete parathyroid hormone Increases blood calcium Oxyphil cells Smaller nucleus More cytoplasm; eosinophillic Function unknown Suggest they are transitional derivatives of chief cells Video recording o Thyroid and parathyroid glands Microscope images o 10x o 40x

8 Pineal Gland Function o Secretion of melatonin, influenced by light and dark periods of the day Location o Epithalamus of the brain (roof of diencephalon) Structure o Capsule Pia Mater Form septa o Bring in blood and lymph vessels and nerve fibers o Cells Pinealocytes Basophilic cells with one or two long processes o Secrete melatonin Interstitial cells Glial cells Deeply stained elongated nuclei

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