Endocrine Organs

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

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 andparaventricular nuclei of hypothalamus Produce vasopressin (ADH) and oxytocin in

nuclei then travel to pars nervosa via axonsto the Herring bodies

o Herring bodies (i.e. axon terminals) ADH and Oxytocin released with neural

stimulationo Pituitcytes - glial cells

Infundibular stalk

• Video recordingo Pituitary gland

• Microscope imageso 4xo 10x

Adrenal (Suprarenal) Gland

• Functiono Adrenal cortex – mesoderm origin, secrete steroid hormoneso Adrenal medulla – neural crest origin; secrete epinephrine and

norepinephrine

• Locationo Retroperitoneal organs located on the superior poles of the kidneys,

embedded in adipose tissue

• Structureo Capsule

Dense connective tissue• Produces septa into the gland as trabeculae

o Bring in blood and lymph vessels and nerve fibers

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

o Adrenal Medulla Chromaffin cells

• Large, pale-staining polyhedral cells• Modified sympathetic postganglionic neurons• Granulated

o Secrete epinephrine and norepinephrine

• Video recordingo Adrenal gland

• Microscope images o Adrenal cortex

10x 40x

o Adrenal medulla

10x 40x

Thyroid Gland

• Functiono Secretion of hormones thyroxine (T3), tri-iodothyronine (T4) and

calcitonino Hormones are important for metabolism, growth and calcium regulation

• Locationo Located in the cervical region anterior to the larynxo Consists of two lobes united by an isthmus; may have an accessory

pyramidal lobe

• Structureo Capsule

Dense connective tissue• Form septa

o Bring in blood and lymph vessels and nerve fibers

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

o Parafollicular Cells (Clear cells or C cells) Lie in clusters outside the thyroid follicles Contain secretory granules

• Secrete hormone calcitonino Decrease blood calcium

• Video recordingo Thyroid and parathyroid glands

• Microscope imageso Thyroid gland

4x 10x 40x

Parathyroid Gland

• Functiono Produces parathyroid hormone which is involved in calcium regulation

• Locationo Fur to six oval glands located on the posterior surface of the thyroid gland

• Structureo 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 granuleso Secrete parathyroid hormone

Increases blood calcium Oxyphil cells

• Smaller nucleus• More cytoplasm; eosinophillic• Function unknown• Suggest they are transitional derivatives of chief cells

• Video recordingo Thyroid and parathyroid glands

• Microscope imageso 10xo 40x

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