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Endocrine system (Endocrine cells in other organs (Liver— hepatocytes…

- - - - Only thyroid C cells are involved.
      - Parathyroid cells
      - pancreatic islet cells
      - chromaffin cells from adrenal medulla
- - - - Vasopressin/ADH
        
        Makes distal convoluted tubules more permeable, so water is reabsorbed and urine is more concentrated.
        
        Contraction of smooth muscles
        
        Water retention in the kidney
      - Oxytocin
        
        Milk secretion
        
        Uterine contraction
    - - pituicytes: Scattered among the axons and act as glial cells
      - paraventricular
      - supraoptic
  - - - Prolactin
        
        Sustain lactation.
        
        Support immune system.
        
        Acts generally
        
        Cell type that synthesise hormone and secrete
        
        Lactotropes
      - Thyroid Stimulating Hormone
        
        Thyrotropes
      - Adrenocorticotrophic Hormone
        
        Carticotropes
      - Gonadotrophic hormones
        
        Luteinising Hormone
        
        Follicle Stimulating Hormone
        
        Gonadotropes
      - Growth hormone
        
        Tropic and general acting hormone
        
        growth-promoting effects via its stimulation of insulin-like growth factors.
        
        A major source of circulating IGF-1 is the liver.
        
        Promotes metabolic effects.
        
        Somatotropes
- - - - large eosinophilic cells containing lipid droplets.
      - produces testosterone
      - present between seminiferous tubules.
      - produce cholesterol-based steroid hormones.
      - Controlled by interstitial cell stimulating hormone (ICSH)
  - - - secreted by cells of the theca interna(surrounds developing ovarian follicle)
    - - produced by thecal cells and by the corpus luteum
      - The main mass of corpus luteum is made up of sheets and cords of typical steroid-secreting cells
- - - - Calcitonin
        
        polypeptide that lowers blood calcium levels by stimulating osteoblastic activity.
        
        inhibiting decalcification of bone
      - They are found between follicles.
      - Intracellular granules also contain catecholamines and monoamine oxidase
    - - T4 thyroxine
      - T3 triiodothyronine
      - Arranged in follicles
      - Hormones stored in the form of Colloid
      - Active cell
        
        Cells are larger and columnar
        
        The follicles are empty
      - Inactive cell
        
        Cells are short and cuboidal
        
        Follicles full of colloid
      - T4 is converted to T3 in the blood where it has effect on metabolism, and the growth of the nervous system.
- - - - Larger and less numerous
      - Small dark nucleus and eosinophilic cytoplasm. (acidic stain that binds to basic tissue)
      - They are parathyroid cells that are senile or weakened with age.
    - - Produce parathyroid hormones=> raises Calcium levels==> increased osteoclasts=> bone matrix break down=> absorption of Ca** from renal tubules and SI
      - Prominent nucleus and little cytoplasm
- - - - Functions
        
        Carbohydrate metabolism
        
        Sexual function
        
        Electrolyte homeostasis
      - Three Zones
        
        Zona Fasciculata
        
        Middle and largest zone
        
        Cells secrete glucocorticosteroids such as cortisol.
        
        arranged in fascicles separated by capillary sinusoids
        
        Cells are filled with lipid droplets sometimes called spongiocytes.
        
        Zona Reticularis
        
        Thin, Innermost zone.
        
        Secrete sex hormones mainly androgens.
        
        Groups of cells separated by sinusoid.
        
        Zona Glomerulosa
        
        The outermost zone. Immediately under Capsule
        
        Cells are arranged in clusters
        
        Capillary sinusoids
        
        Connective tissue tuberculae in-between sinusoids.
        
        Cells secrete mineralcorticosteroids, mainly Aldosterone.
        
        Important in electrolyte and fluid homeostasis by causing Sodium retention.
      - derived from the same region of embryonic mesoderm that gives rise to the gonad
    - - cause smooth muscle contraction
      - affect metabolism
      - increase heart rate
      - polyhedral cells that produce catecholamines like adrenaline and noradrenaline
        
        High affinity for chromium salts
        
        chromaffin cells.
        
        adrenaline-producing
        
        Dopamine derived from Tyrosine.
        
        noradrenaline-producing
        
        Chromaffin cells are present in the lining of the intestines and the respiratory tract.
        
        found scattered in sympathetic ganglia and, in the fetus, as a large organ in front of the abdominal aorta which degenerates after birth.
        
        produce catacholamines that cause smooth muscle to contract and heart rate to increase.
      - derived from neuroectoderm
      - Corticomedullary interactions: Blood => cortical sinusoids => blood has high levels of Cortisol. =>Reaches Medulla=> Cortisol induces the enzyme phenylethanolamine N-methyl transferase (PNMT) that converts noradrenaline to adrenaline