Histo Review Endocrine

ENDOCRINE SYSTEM REVIEW

• Ei guys sorry gumawa nlng akong review kasi mejo pressed for time… I tried to make it as self-study-able as possible and merong mga questions in between (yung answer nasa next slide)… if you have questions text me nlng or ask on tues morning (or ask Bea). Pero it would be best if you referred to a book. Hope this helps anyway and I hope hope we get higher grades this time 

• Pituitary (neurohypophysis, adenohypophysis) – Pars distalis, pars intermedialis; pars nervosa – Chromophobes, acidophils, basophils; Herring body, pituicytes – Rathke’s pouch, infundibulum

• Adrenal Gland – Cortex, medulla – Zona glomerulosa, zona fasciculata, zona reticularis

• Thyroid Gland – Thyroid follicles, C cells (parafollicular cells), colloid

• Parathyroid Gland – Adipose, oxyphil cell, chief cell

• Endocrine Pancreas – Islets of Langerhans, Beta cell (insulin), Alpha cell(glucagon)

• Pineal Gland

Hypophysis – pituitary gland • Located in the diencephalon • Comprised of adenohypophysis (anterior pituitary) and neurohypophysis • Infundibulum: connects pituitary to hypothalamus •

Pituitary • Adenohypophysis comprised of pars distalis and pars intermedia – Pars distalis: secretes growth hormone (GH), thyroid stimulating hormone (TSH), adenocorticotropic hormone (ACTH), folliclestimulating hormone (FSH), Luteinizing hormone (LH) and prolactin – Pars intermedia: secretes melanocyte stimulating hormone (MSH) – Pars tuberalis: thin extension in contact with infundibulum

• Neurohypophysis comprised of pars nervosa, infundibular stalk and median eminence – Pars nervosa (posterior pituitary) : stores ADH and oxytocin • ADH and oxytocin not synthesized in pars nervosa; secreted by hypothalamus

Hypophysis – pituitary gland Adenohypophysis (ant. Pituitary) • Pars distalis 

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•

– darker staining

Pars intermedia – in between pars distalis and pars nervosa – Narrow band of darker staining cells along right hand margin of slit

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Slit remnant of Rathke’s pouch

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Neurohypophysis (post. Pituitary) • Pars nervosa 

• Pars nervos a • Pars interme dia • Pars distalis

Pars nervosa

Pars distal is

Pars intermed ia

Adenohypophysis –pars distalis

• Pars distalis • Secretory Cells of pars distalis – Chromophils (A): darker staining, dark cytoplasm • Basophils: v. dark staining nucleus (dark staining cytoplasm) • Acidophils: dark staining cytoplasm

– Chromophobes(B): Secretory cells are arranged in clumps separated a fine(only hardlybystain reticular fiber CT ( thin black found in anterior lines ), where the capillaries lie

Chromophobes

Chromophils and their secretions • chromophil A cid o psh ils –S o m a to tro p h ic ce ll ( G H ) –M a m m o tro p h ic ce ll ( Pro la ctin ) pnemonics: GPA" (g rowth hormone and p rolactin are secreted by the a cidophils)

Basophils

–Gonadotrophic cell (FSH, LH) –Thyrotropic cell (TSH) –Cotricotrophic cell (ACTH) B-FLAT" (b asophils secrete F SH,

Pars distalis

b a so p h il

acidophil

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chromophobe

Question: In this picture of the pars distalis, what type of secretory epithelial cell are denoted by arrow?

Red: Basophil (other cells are acidophils – yellow; chromophobes – orange)

Question: In this picture of the pars distalis, what type of secretory epithelial cell is labeled 'a'?

Chromophobe (no stain) -other chromophobes  yellow arrow (other cells are b- basophil; c- acidophil)

Question: What hormones do these cells secrete?

Prolactin and Growth hormone (mammotropic & somatotropic) (other cells: blue – chromophobe, yellow: basophil)

Capillary • NOTE: endocrine glands are highly vasculariz ed (since secretions go to blood) • Encircled: nucleus of endothelial cell

Question: Identify (ID) cell. ID gland

Chromophobe pars distalis – hypothalamus other structures (basophil – purple stain and acidophil – pink stain) encircled – blood vessel with RBC

Pars nervosa

Pars distal is

Pars intermed ia

Pars intermedia • May be cystic  Pars intermedia fused with/within pars distalis (purple arrow) • Lumen of rathke’s pouch disappear • Split in right (green)  fixation artifact

Question: Identify gland Identify space at tip of arrow

Pituitary gland cystic pars intermedia other structures (notice lighter pars nervosa with pituicytes; pars distalis with dark staining basophils and acidophils and light staining chromophobes) Pars nervosa

Pars distalis

Pars nervosa

Pars distal is

Pars intermed ia

Posterior pituitary functions • Stores and releases 2 hormones that are produced in the hypothalamus: – Antidiuretic hormone (ADH/vasopressin): – Promotes the retention of H20 by the kidneys. » Less H20 is excreted in the urine.

• Oxytocin: – Stimulates contractions of the uterus during parturition. – Stimulates contractions of the mammary gland alveoli. » Milk-ejection reflex. 

Neurohypophysis – pars nervosa • Cells of pars nervosa

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– Pituicytes (C):neuroglial-like; – Herring bodies: cellular projections which store neurotransmitters accumulation of secretion within the axon of neurons whose cell bodies lie in the hypothalamus of the brain • no nuclei

– Nuclei of endothelial

Pars nervosa pituicytes

Question : ID gland. ID structures

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Post. Pituitary – pars nervosa

ID gland. ID structures

Herring body pituicyte nucleus Nucleus of endothelial cell of fenestrated capillary 

Question : ID gland. ID pointed structure

Post. Pituitary; Herring body

Question: ID gland. ID pointed structure

Pituicyte (round/oval nuclei)

Thyroid Gland • Largest of the pure endocrine glands • Composed of many spherical hollow sacs (thyroid follicles) surrounded by cells (follicular cells/principal cells) • Follicles are filled with a colloid • Follicular cells use the thyroglobulin and iodide stored in the colloid to produce primary thyroid hormones (ex. T3 and T4) • In between follicles are parafollicular cells which secrete calcitonin • Only gland which stores its hormonal secretion extracellularly before releasing into bloodstream

•

Thyroid Gland

Thyroid follicles

Functions of T3 • Stimulates protein synthesis. • Promotes maturation of nervous system. • Stimulates rate of cellular respiration by: – Production of uncoupling proteins. – Increase active transport by Na+/K+ pumps. – Lower cellular [ATP].

• Increases metabolic heat. • Increases metabolic rate. – Stimulates increased consumption of glucose, fatty acids and other molecules. 

Thyroid Gland Thyroid follicle Follicular/ principal cells: simple cuboidal cells (actively synthesizing), simple squamous cells (inactive stage)  -line the follicle  -lesser cytoplasm compared to parafollicular cells Colloid : pink, contains thyroglobulin and iodine (hormone precursors) 

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Parafollicular cells Parafollicular cells  -”C” cells  -cells outside of follicle  -produce calcitonin 

Question: What is this homogenous substance?

Colloid filled with thyroglobulin – glycoprotein precursor of thyroid hormone other structures (follicle cells -green, parafollicular -purple (calcitonin), black – capillary)

Parathyroid Gland

Parathyroid Glands • Parathyroid (A) embedded in thyroid (B) • Notice thyroid follicles filled with colloid (lower half) • Notice the absence of follicles in parathyroid tissue (upper half) • Parathyroid cells usually darker staining (due to

Some functions of PTH: Single most important hormone in the control of blood [Ca2+ ]. 

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inc renal tubular absorption of Ca inc intestinal Ca absorp 

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• Notice that the parathyroi d gland contains blood vessels and adipocytes • Notice that Chief cells appear as bands/ ribbons or cords (yellow scribble in

Cells of Parathyroid C h ie f ce lls ( w ith in g re e n a rro w ) - secrete Pa ra th yro id h o rm o n e ( PT H ) -more numerous O xyp h ilce lls ( w ith in b lu e a rro w ) -smaller , darker n u cle u s -less numerous th a n ch ie f ce lls -more cytoplasm ( usually pink sta in ) -function not cle a r

Question: ID gland and cell

Parathyroid tissue C h ie f ce ll ( m o re n u m e ro u s, se cre te PTH ) O xyp h ilce ll ( le ss n u m e ro u s a n d la rg e r)

Oxyphil cells ( bigger cytoplasm )

Adipocytes chief cells

Adrenal Gland • Encapsulated • Comprised of a cortex and medulla – Cortex originates from mesoderm and medulla from the neural crest – Cortex further subdivided into zona glomerulosa, zona fasciculata and zona reticularis – Cortex does not receive neural stimulation (must be hormonally stimulated via ACTH) 

General parts of Adrenal Gland • Capsule (A): • Cortex (B): divided into three zones within areolar/reticular CT framework • Medulla (C):

Adrenal Gland

Adrenal Gland: Cortical Division

Question: ID gland. ID layer

A d re n a l m e d u lla Z o n u la g lo m e ru lo sa

Zona glomerulosa – Beneath capsule – Cells are composed of columnar cells arranged in small clusters – Cells have heavily stained nuclei and basophilic cytoplasm – Fairly dark and quite narrow – involved in electrolyte regulation via secretion of aldosterone and

Z. Glomerulosa arranged in clusters (red) encircled in yellow: ang walang kamatayang endothelial cell nucleus

Question: ID gland. Id layer

W h a t d o e s it se cre te ?

Adrenal gland zona glomerulosa secretes mineral corticoids (aldosterone)

Zona Fasciculata • Zona fasciculata – Center of adrenal cortex – Widest, palest layer – Identified by arrangement of vacuolated cells in vertical columns or strips – Cells appear pale and foamy looking because of dissolved lipid of their secretions

Zona fasciculata encircled in yellow: endothelial cells of capillary

• Note columna r arrange ment of cells (vertical, parallel to each other with capillarie

Zona Reticularis • Innermost cortical layer • cells are somewhat unorganized (anastomosing cords) • involved in sex hormones (sex steroids) 

Question: ID gland. ID layers

• Adrenal gland • Zona reticularis and medullary layer

Adrenal Medulla • Lighter than cortex • Site of epinephrin e and norepineph rine production • Cells: ganglion cells (in blue arrow)

Chromaffin cell (secrete catecholamines)

Functions of adrenal medulla • Innervated by preganglionic sympathetic axons (SNS) – Increase respiratory rate. – Increase HR and cardiac output. – Vasoconstrict blood vessels, thus increasing venous return. – Stimulate glycogenolysis. – Stimulate lipolysis. 

Question: Why does the venous blood draining the cortex to the medulla have a high concentration of glucocorticoids?

Glucocorticoids are needed for the synthesis of phenyl ethanolamine N methylene  a key enzyme in the synthesis of nor epinephrine

Pancreas • Accessory gland for digestion • Endocrine function: insulin and glucagon

• Islets of Langerhans (A): endocrine portion of pancreas – Lighter staining compared to exocrine acinar ducts (produce cells for the digestive system) – Appear in patches throughout pancreas – types of cells • alpha cells secrete glucagon (outer) • beta cells secrete insulin (inner)

– types of cells • alpha cells secrete glucago n ( usuall y stain

red

and found in periph ery outer) • beta cells secrete insulin (usually stain

blue

Pineal Gland • Projection of the roof of the diencephalon with a small recess of the third ventricle extending to its stalk • Covered by pia mater • Hormone produced is melatonin • Hormone production : greatest in the dark • Comprised of – Pinealocytes & glial cells – Pineal sand : increases

Pineal Gland • Pinealocyte (region of orange arrow) – Major cell type – Nuclei round with prominent nucleoli – Secrete melatonin

• Glial /interstitial cell – Nuclei stain more deeply

• Brain sand – Aggregations of Ca+

Brain sand