Endocrine system

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Endocrine system

• Histology a embryology
• Curs Endocrine system

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Endocrine system

• one of regulatory systems
• hormone (gr. horman - invite incite)
• chemical messenger produced by endocrine gland
  and transported to target organ by blood
• proteins (polypeptide) - insuline
• biogene amins - adrenalin
• steroids - estrogens

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Endocrine system

• endocrine glands
• diseminated endocrine cells
• neuroendocrine cells

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Endocrine glands

• Pituitary gland (gl. pituitaria hypophysis)
• Thyroid gland (glandula thyroidea)
• Parathyroid gland (gll. parathyroideales)
• Suprarenal gland (gll. suprarenales)
• Endocrine pancreas (insulae pancreaticae)
• Pineal gland (gl. pinealis - epiphysis)

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Pituitary gland - characteristic

• composed of two lobes
• frontal - adenohypophysis
• dorsal - neurohypophysis
• intimal connection with hypothalamus

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Pituitary gland - development

• Ratkes pouch
• 3rd week - ceiling of oral cavity
• evagination to the diencephalon
• separation proliferation of anterior wall
• diencaphalic pouch
• origin of dorsal lobe
• cells diferetiate to pituicytes

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Adenohypophysis

• distal part (pars distalis)
• largest (75)
• tuberal part (pars tuberalis)
• cranialy
• intermedial part (pars intermedia)
• between adeno- and neurohypophysis

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Distal part

• cellular cords between them capillaries
• on HE staining 3 types of cells
• acidophils
• basophils
• PAS-positive
• chromophobes
• without granules undiferentiated elements

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Acidophils in distal part

• a - cells (40 - 50)
• large granules gER
• nucleus surrounded by granuleless zone GC
• growth hormone
• e - cells (15 - 20)
• usually small and rare (x gravidity lactation)
• small granules (gravidity - enlargment)
• prolactin

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Bazophils in distal part

• ß1 - cells
• large granules by the cellular membrane
• ACTH (ß-MSH Met-enkephalin endorfin)
• ß2 - cells
• large cells small granules by the CM
• TSH
• d - cells
• large cells medium granules
• FSH LH

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Tuberal part

• surrounds infundibulum
• numerous capillaries
• most of cells are d - cells

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Intermedial part

• rudimental
• cells in cords
• basophils
• remnants of Ratkes pouch lumen

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Neurohypophysis

• medial eminence (eminentia medialis)
• bottom of 3rd brain ventricle
• numerous unmyelinisated nerve fibers
• infundibulum
• unmyelinisated nerve fibers
• some of them leads to capillaries
• nervous part (pars nervosa)

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Nervous part

• nerve fibers
• axons of hypothalamical neurons
• Herring bodies - contain secretory granules
• secretion of oxytocine and vasopresin
• pituicytes
• glial cells
• capillaries

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Pituitary gland - blood supply

• superior hypophyseal artery
• prim. capillary plexus in infundibulum
• sec. capillary plexus in adenohypophysis
• hypophyseal portal system
• inferior hypophyseal artery
• capillary network in neurohypophysis

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Hypothalamus

• neurosecretory cells
• production of granules and their secretion to
  blood
• paraventricular nucleus - oxytocin
• supraoptical nucleus - vasopresin
• other nucleuses - liberins and statins
• regulation of adenohypophyseal secretion

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Thyroid gland - characteristic

• two lobes isthmus
• metabolic role
• thyroxine T4 trijodtyronin T3
• calcitonin

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Thyroid gland - development

• development from 24th day
• invagination of entoderm of primitive pharynx
• relat. and absol. descent - ductus thyreoglossus
• foramen caecum
• appearence of lobes (lobus pyramidalis)

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Thyroid gland - histogenesis

• solid endodermal object
• ingrowth of surrounding mesenchyme and vessels
• ingrowth of ultimobranchial bodies
• 10th week - cells make groups
• single layer epithelium surrounds lumen
• 11th week - production of colloid

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Thyroid gland - morphology

• capsule - septa
• follicles (50 - 900 um)
• round shape
• single layer epith. from follicular cells
• contain colloid - thyreoglobulin
• follicular cells
• parafollicular cells

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Follicular cells

• round nucleus numerous gER (basal parts) MIT
• numerous lysosomes
• thyreoglobulin production of T4 a T3

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Synthesis of thyroid hormones

• 1. iodid pump use ATP and pumps iodium from blood
  to colloid
• 2. and 3. synthesis of thyroglobulin and
  peroxidase stored in one secretory granule
  their secretion to colloid by exocytosis
• 4. iodisation of thyroglobulin by peroxidase in
  colloid resulting in iodthyroglobulin

• endocytosis of iodthyroglobulin
• 5. fusion of primary lysosome with endocytosed
  vesicle
• proteolysis of iodthyroglobulin resulting in T3
  T4 and other fragments
• secretion of T3 and T4 to blood circulation
• 6. binding to the transporting plasma protein
  (TBG)

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Parafollicular cells

• C-cells
• between follicles (alone or in groups)
• larger lighter
• many of ER and GA MIT
• granules - round dark
• production and secretion of calcitonin

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Parathyroid gland - characteristic

• 2 pairs of small rounded bodies
• role in metabolism of bones and calcium
• parathormon (PTH)

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Parathyroid gland - development

• dorsal parts of 3rd and 4th branchial pouch
• 5th week - proliferation of endoderm losing of
  lumen
• ingrowth of vessel from mesenchyme
• chief cells - fetal metabolism of calcium
• oxyphil cells - appearence in 7th year after birth

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Parathyroid gland - morphology

• capsule septa
• parenchyme divided on cords
• chief cells - medium to large cells (4-8 um)
• light cytoplasm
• granules contain PTH
• oxyphil cells - rare larger
• cytoplasm darker (more acidophilic) no granules
  numerous MIT
• unclear function

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Function of parathormon

• PTH connected to osteoblasts RANKL (ligand
  for receptor for activation of nuclear factor
  kappa)

PTH connected on osteoblasts M-CSF (monocyte
collony stimulating factor)

• Monocytes reaches an area of bone remodeling (on
  their surface are receptors for M-CSF)

Connection of M-CSF on monocyte activates
expresion of RANK receptor
Connection RANK-RANKL is established (appearence
of multinuclear precursor unable to reabsorb
bone)
RANK-RANKL connection is inhibited by
osteoprotegerin (has greater affinity to
receptor his synthesis in osteoblast in
inhibited by PTH)
A resting osteoclast (nonfuctional) uncouples
from osteoblast.
Maturation of cells is completed when the sealing
zone and ruffled border appear. (The formation of
sealing zone requires integrins)
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Suprarenal gland - characteristic

• double gland
• two special tissues - cortex and medulla
• mineralocorticoids - aldosteron
• glucocorticoids - cortisol corticosteron
• androgens - testosteron
• catecholamins - epinephrin norepinephrin

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Suprarenal gland - development

• cortex - from coelomic epithelium next to the
  mesenterium
• proliferation moving to the aorta
• medulla - from the origin of celiac ganglion
• sympaticoblasts growth to cortical mass
• secundar proliferation of cortex - definitive
  cortex

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Suprarenal gland - cortex

• capsula - septa
• fibroblasts collagenous and elastic fibres
  smooth muscle cells
• cortex of suprarenal gland
• zona glomerulosa - (15)
• zona fascicularis - (65)
• zona reticulosa - (7)

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Zona glomerulosa

• outer zone
• rounded cords of cells
• cells producing steroids
• between cords are capillaries (sinusoidal)
• production of aldosteron

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Zona fasciculata

• medium widest zone
• long paralel cords of cells
• in cytopl. numerous lipid droplets
• cells producing steroids
• between cords are capillaries (again)
• production of glucocorticoids and androgens

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Zona reticulosa

• inner zone of cortex
• irregular anastomozing cords of cells
• small cells with granules of lipofuscin
• some elements have pyknotic nucleus
• between cells are capillaries (of course)
• production of glucocorticoids and andogens

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Suprarenal gland - medulla

• anastomozing cords of polyedric cells
• large cells large nucleus
• gER MIT GK granules
• epinephrin norepinephrin chromogranins ATP
• dopamin-ß-hydroxylaseu Leu- a Met- enkefalin
• between cords are capillaries (what else)
• rarely - parasympatical ganglious cells

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Suprarenal gland - blood supply

• aa. suprarenales sup. mediae et inf.
• subcapsular plexus
• capsular cortical and medullar arteries
• in medulla arterial and also venous blood
• vena suprarenalis

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Islets of Langerhans

• endocrine part of pancreas
• 01 - 02 mm in size 1 - 15 milions in count
• various type of cells - A B D PP (F)
• production of
• insulin
• glucagon
• somatostatin
• pancreatic polypeptide

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I. of L. - development

• differentiated from indiferent cells of p.
• divided from tubules
• first are A-cells then B D and PP
• insular field - all types are mixed
• mantle inslets - B in core A mantle
• insulin in 10th week glucagon in 15th week

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I. of L. - morphology

• cords of epithelial cells between them are
  capillaries (really)
• body and tail - 70 B 20A 10D1PP
• haed - 65 PP 25 B 7 D 3 A
• I. of L. - tail gt body gt head

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I. of L. - cellular types

• gER GA granules
• A - cells
• a - granules - rounded 300 nm
• glucagon - hyperglycemic-glycogenolytic factor

• B - cells
• ß - granules - rounded 300 nmspecies specifical
• insulin - hypoglycemic factor

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• D - cells
• d - granules - rounded 250 nm
• one long prominence - paracrine secretion
• somatostatin
• PP - cells
• granules - 180nm very light
• pancreatic polypeptide - regulation of exocrine
  pancreas
• (G - cells)
• production of gastrinu

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Pineal gland

• upper dorsal end of 3rd brain ventricle
• capsule from pia mater septa
• pinealocytes - main cells
• nucleus with expressive nucleolus bas.cytopl.
• production of melatonin
• interstitial cells - astroglial cells
• rod like nucleus
• spherolithi pineales - concrements of
  protein-like material
• count of them elevates with age

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Disseminated endocrine cells

• endocrine cells of GIT
• closed type vs. open type
• contain numerous granules
• many of types many of hormones
• regulation of GIT function