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Endocrine 1

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Endocrine 1

Islets of Langerhans
- Islet of Langerhans cells
  - α alpha: periphery
    - Glucagon
      - activates glycogenolysis and lipolysis
      - increases blood glucose
  - β beta center
    - Insulin
      - Dimer of α and β chains
        with S-S bridges
      - entry of glucose into cells
      - decreases blood glucose
      - Diabetes mellitus
        insulin-dependent IDDM type 1
        autoimmune response to β cells
        treated by insulin
        non-insulin dependent NIDDM type 2
        target cell insulin insensitivity
        β cells cannot produce enough insulin
  - δ or D delta
    - Somatostatin
      - Inhibits release of other islet cell hormones
        through paracrine action
      - inhibits release of GH & TSH
        in anterior pituitary
      - inhibits HCl secretion
        by gastric parietal cells
  - PP gamma cells
    - Pancreatic polypeptide
      - Stimulates gastric chief cells activity
      - inhibits bile secretion
      - inhibits intestinal motility
      - inhibits pancreatic enzyme
      - inhibits bicarbonate secretion
Pineal
- contains
  - pinealocytes
    - epithelial-derived
    - large nuclei and prominent nucleoli
    - produce melatonin
      - from tryptophan
      - maintaining circadian rhythms
      - tumor suppressor
        scavenge hydroxyl radical
      - puberty timing
  - supporting glial cells=interstitial cells
    - less numerous
    - smaller
    - darkly stained nuclei
  - two types of calcifications
    - Corpora arenacea= brain sand
      - lumpy aggregates
      - variable size
      - darkly stained
      - hydroxyapatite + protein
      - convenient marker of the midline in sagittal sections
      - Increase with age
    - Myeloconia= brain dust
      - smaller crystals of calcite
        visible only with electron microscope
      - Similar to otoliths of inner ear
- pinecone-shaped organ
- Function
  - responds to light
    - light received by retina
      - Retinal signals
        stimulate
        hypothalamus
        sympathetic
        norepinephrine release
        inhibits pineal function
  - active in darkness
- Divided into lobules by CT
  - pinealocytes
  - interstitial (glial) cells
Pituitary=hypophysis =master endocrine organ
- Anterior pituitary: adenohypophysis= oral derivatives
  - pars intermedia
    - remnant of Rathke’s pouch
      - epithelial cells
      - colloid material
    - derived> oral ectoderm
    - separated from the pars distalis by
      - fluidfilled cysts
        are remnants of Rathke's pouch
        filled with a colloid-like solution
    - details
      - between distalis & nervosa
      - contains basophilic cords
      - resembles pars distalis
    - - produce melanocyte stimulating hormone =MSH
        from proopiomelanocortin
        stimulates melanin production
      - synthesizes proopiomelanocortin (POMC)
        Cleaved to form
        ACTH
        β-endorphin
        MSH
  - pars tuberalis
    - tube-like region
  - pars distalis
    - Histologically distinguished cells
      - acidophils
        red, affinity for acidic dyes(eosin)
        Somatotrophs
        mammotrophs
      - basophils
        blue, affinity for basic dyes(hematoxylin)
        tropic hormones: act on other endocrine organs
        corticotrophs
        gonadotrophs
        thyrotrophs
      - chromophobes
        pale, degranulated acidophils or basophils or stem cells
    - Cell types
      - Corticotrophs
        secrete ACTH
        controlled by CRH
        adrenal cortex
        release corticosteroids
        secrete Lipotropin
        regulate lipid metabolism
      - Somatotrophs
        secrete GH
        regulated by
        + GHRH
        - somatostatin
      - Mammotrophs=lactotrophs
        stimulated by
        vasoactive intestinal peptide
        thyroid releasing hormone (TRH)
        secrete prolactin
      - Gonadotrophs
        secrete FSH & LH
        FSH
        stimulates germ cell maturation
        Female
        ovarian follicle development
        estrogen secretion
        male
        spermatogenesis
        LH
        Female
        ovulation
        progesterone secretion
        Male
        interstitial/Leydig cells stimulation
        testosterone production
        controlled by GnRH & LHRH
      - Thyrotrophs
        secrete TSH=thyrotropin
        act on thyroid to secrete
        thyroxine=T4
        triiodothyronine=T3
        controlled by TRH
      - folliculostellate cells
        intercellular network
        numerous gap junctions
- Posterior pituitary: neural-derived regions: neurohypophysis
  - Pars nervosa
    - axon extending from two hypothalamic nuclei
      - paraventricular
      - supraoptic
    - neurosecretion
      - release stored hormones
        oxytocin 9aa
        antidiuretic hormone= ADH= vasopressin 9aa
        Stored in
        swellings near the axon terminus
        called Herring bodies
        coupled to neurophysin (N) I & II
  - Infundibulum
    - tube like cuff
    - hypothalamohypophyseal tract
  - median eminence
  - contains
    - unmyelinated axons
    - pituicytes=glial-like cells
      - interconnected via gap junctions
    - fenestrated capillaries
hormones
- peptide
  - ADH, oxytocin
- Lipid-derived
  - from cholesterol
    - estrogen
    - glucocorticoids
  - from eicosanoids
    - prostaglandins
- Protein
  - prolactin
  - growth hormone
- Monoamine
  - from a.a.: phenylalanine, tyrosine, tryptophan
  - catecholamines
    - adrenaline
    - noradrenaline
  - thyroxine
  - melatonin

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Description: Mind Map on Endocrine 1, created by B N on 03/11/2017.
Created by: B N
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Endocrine 1

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