Flashcards in Endocrine Histo Deck (118):
Regulates the activities of different cells, tissues, and orgrans
Provides communication between different systems in the body and coordinates body growth and development, is similar to the nervous system
Provides endocrine and neuroendocrine control of the other endocrine glands
Pituitary gland and hypothalamus
Pea-sized unpaired endocrine gland located at the base of the brain
Where does the pituitary gland sit?
Connects the pituitary gland to the hypothalamus
Surrounds the pituitary gland and is formed of dense irregular connective tissue
2 fundamental components of the pituitary gland
Adenohypophysis and Neuropophysis
How does the adenohypophysis develop?
Develops as an invagintation of the ectoderm of the oral cavity known as Rathke's pouch
How are the adenohypophysis cells organized?
Clumps and cords around fenestrated capillaries
Regions of the adenohypophysis
Pars distalis, pars intermedia, pars tuberalis
Bulk of the anterior lobe of the adenohypophysis
Thin remnant of the wall of Rathke's pouch
Remnants of the Rathke's pouch
Lines the pars intermedia
Forms a collar or sheath around the infundibular stalk
5 cells of adenohypophysis
Corticotropes, somatotropes, lactotropes, gonadotropes, thyrotropes
Corticotropes, gonadotropes, thyrotropes
What do somatotropes secrete?
Somatotropin, aka growth hormone
2 hormones that control the release of GH
GH releasing hormone (release) and somatostatin (inhibits)
Most abundant endocrine cells in the adenohypophysis
What do lactoropes secrete?
Hormone that controls the production and release of prolaction
Inhibited by dopamine, thyrotropin releasing hormone stimulates
What do corticotropes produce?
Adrenocorticotropic hormone (ACTH)
What does ACTH act on?
The cells of the adrenal cortex
Controls the release of ACTH
Corticotropin-releasing hormone (CRH) released from the hypothalamus
2 main hormones secreted by gonadotropes
Follicle-stimulating hormone (FSH) and lutenizing hormone (LH)
Controls the secretion of the gonadotropes
Gonadotropin-releasing hormone released from the hypothalamus
What do thyrotropes produce?
Thyrotropic hormone (TSH)
Controls the release of TSH
Part of the pituitary derived from nerve tissue
Regions of the neurohypophysis
Pars nervosa, infundibulum
Glial cells in the neurohypophysis
What is secreted into the pars nervosa by the hypothalamus?
Oxytocin and anitduiretic hormone
Large distended axon terminals of these neurons can sometimes be visualized as what?
What does the superior hypophyseal artery supply?
Pars tuberalis, infundibulum, median eminence, pars distalis
Most prominent feature of the hypophyseal blood supply
Hypophyseal portal system
What does the superior hypophyseal artery form upon arrival to the pituitary?
Primary capillary plexus
Where does blood go after the primary capillary plexus?
Into the hypophyseal portal veins, into the secondary capillary plexus in the pars distalis
Within which plexus do the hormones for the bloodstream exit the pituitary?
Secondary capillary plexus
Blood supply to the pars nervosa
Inferior hypophyseal artery
Unpaired pine-cone-shaped midline organ of the brain
Where is the pineal gland located?
Posterior end of the third ventricle of the brain, covered by cerebral hemispheres
What does the pineal gland develop out of?
Outgrowth from the dicephalon
What covers the pineal gland?
Pia mater forms the capsule, septa extends into the gland fron this capsule
What are aggregates of calcuim phosphates found with the pineal gland?
Corpora arenacea, aka brain sand
Principle cells of the pineal gland
What do the spaces between the clusters of the pineal gland contain?
Axons, pinealocyte cell processes, blood vessels, corpora arenacea
Describe pinealocytes on microscope
Large euchromatic nuclei with a prominent nucleolus
What do pinealocytes secrete?
How does the information about the light/dark cycles reach the pineal gland?
Retinothalamic tract, connecting the suprachiasmic nucleus with the sympathetic neural tracts
How is the synthesis/secretion of melatonin controlled?
Norepinephrine released by the sympathetic neurons
What is the activity of melatonin?
Inhibits the steroidogenic activity of the gonads
Supporting cells of the pineal gland
Glial cells (interstitial cells)
Describe the glial cells of the pineal gland
Nuclei are smaller and more heterochromatic
Divisions of the adrenal gland
Cortex(yellow peripheral layer) and medulla(central reddish-brown layer)
Embryological origin of the cortex
Mesenchyme, mesodermal in origin
Embryological origin of the medulla
Neural crest cells, ectodermal in origin
Tissue of the capsule
Dense connective tissue with thin trabeculae into the parenchyma of the gland
Forms the majority of the adrenal gland
Cortex (90% of the gland)
Steriod-producing part of the gland
What does the cortex produce?
Mineralocorticoids, glucocorticoids, some androgens
Characteristics of steriod-producing cells
Numerous lipid droplets, mitochondria with tubular cristae, abundant smooth ER
What do cortex cells do with steriod hormones?
Divisions of the adrenal cortex
Zona: glomerulosa, fasciculata, reticularis
Cell appearance of the zona glomerulosa
Closely packed cubodial/pyramidal cells, arranged into arched cords/curved columns, surrounded by numerous fenestrated sinusoidal capillaries
What do the cells of the zona glomerulosa secrete?
Purpose of mineralocorticoids
Regulate sodium and potassium honeostasis and water balance
Principle mineralocorticoid of the zona glomerulosa
Aldosterone (causes reabsorption of sodium)
Stimulates the zona glomerulosa to produce aldosterone
Makes up the majority of the adrenal gland
Describe the zona fasciculata
Cells form one or two cell-thick straight cords that run at a right angle to the capsule and have fenestrated sinusoidal capillaries between them
Large secretory cells in the zona fasciculata
Secretion of the spongiocytes
Role of glucocorticoids
Increase metabolism of glocus and fatty acids, depress the immune and inflammatory responses
How do glucocorticoids depress the immune and inflammatory responses?
Suppress the production of interleukin-1 and IL-2 by lymphocytes and macrophages, also supress lymphoblast mitosis within lymph nodes
What controls glucocorticoid production?
ACTH produced by the corticotropes of the anterior pituitary lobe. Necessary for cell growth and increased blow flow thru the adrenal gland
Innermost layer of the cortex
Appearance of the zona reticularis
Relatively small cells arranged into irregular cords that anastomose to form a network, contain fewer lipid droplets and stain more intensely with eosin
Contants of zona reticularis cells
What do the cells of the zona reticularis secrete?
Androgens and glucocorticoids
Composition of the adrenal medulla
Polyhedral cells arranged into clumps or cords supported by reticular fibers, with an extensive network of fenestrated capillaries
Principle secreting cells of the adrenal medulla
Where are chromaffin cells derived from?
Neural crest cells, so they are modified postsynaptic neurons that lack axons
What is unique about the granules of the chromaffin cells?
Accumulate and store hormones
How to differentiate between norepinephrine and epinephrine cells in chromaffin cells?
Epi cells are smaller and more abundant. NE cells have larger secretory granules
Innervation of chromaffin cells
Synaptic nerve fibers
Causes the degranulation of chromaffin cells
Release of acetylcholine from the synaptic terminals
How are the hormones of the chromaffin cells delivered to the body?
Via the bloodstream thru fenestrated capillaries
Modulate the activity of chromaffin cells and innervate blood vessels within the medulla
Irrigates the adrenal gland capsule
Blood supply within the cortex
Cortical arteries that branch and form a dense network of fenestrated cortical sinusoidal capillaries
Blood supply within the adrenal medulla
Medullary arteries that form a dense network of fenestrated medullary sinusoidal capillaries AND the cortical capillaires
Recieves blood from smaller blood vessels withing the medulla
Adrenimedullary collecting veins
Drains the blood from the adrenal gland
Central adrenomedullary vein (IVC on right side, left renal vein on left side)
Main structural unit of the thyroid gland
Structure of a thyroid follicle
Spherical structure forms by a layer of simple cuboidal follicular epithelium surrounding a cyst-like central cavity
Contents of thyroid follicle
2 types of cells of the follicular epithelium
Follicular and parafollicular cells
Principle endocrine cells of thyroid gland
Origin of thyroid follicular cells
2 main hormones synthesized by follicular cells
Thyroxine (T4) and Triiodothyronine (T3)
Synthesized in RER of follicular cells and is secreted into the lumen of the follicle
How is iodide used in follicular cells?
Actively transported from blood into cytoplasm, iodine is oxidized to iodine and released into the colloid
How are T4 and T3 stored in the follicular cells?
Linked to thyroglobulin molecule to remain stored in cell
How are T4 and T3 released?
TSH causes cells to take up thyroglobulin resobring the colloid, thyroglobulin is borken down by lysosomes, releasing T3:T4 (1:20) and diffuse into the blood
Main function of parafollicular cells
Synthesis of calcitonin
What does calcitonin do?
Lowers blood calcium levels by suppressing the resorptive activity of osteoclasts and promoting calcium deposition in bones by osteoblasts
Where are parafollicular cells derived from?
Small endocrine glands usually embedded with the thyroid
Arrangement of parathyroid gland cells
Arranged into cords that follow the fenestrated capillaries
2 types of cells of the parathyroid gland
Parathyroid chief cells and oxyphil cells
What do parathyroid chief cells produce?
How does parathormone work?
Increases the blood levels of calcium
Calcium blood levels
Where are parathyroid chief cells derived from?