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http://vslides.unsw.edu.au/VirtualSlideV2.nsf/id/2CA2E0

Histology

Slide 1

  • Pituitary gland
  • Top bit = anterior pituitary gland - adenohypophysis
  • Not very good for basophils
  • In the middle, the thing that splits it is the pars intermedia, beneath which is the posterior pituitary - neurohypophysis
  • Lots of blood vessels (endocrine gland). No ducts (not exocrine)
  • Two cell types visible: acidophils and chromophobes (no colour in cytoplasm - represent 50% of cell types)
  • Describe one hormone produced by each of the cell types
  • Purple material in the middle = colloid (pars intermedia)
    • (NB: in thyroid, the colloid represents T3 and T4
    • Here in the pituitary gland - MSH (melanocyte stimulating hormone)
  • In the anterior pituitary gland, releasing hormones come down from the hypothalamus via the portal system and produce cascade (causing more hormones to be released)
  • Posterior side: pituicytes (support and structures)
    • Strands are nerve fibres
    • Develops from the base of the brain
    • Stringy parts = axons of nerve fibres from the supraoptic and paraventricular nuclei
    • Produces oxytocin (uterus, breast) and ADH (kidneys - collecting tubules)
    • Herring bodies = blobs where the hormones are stored before being released
  • Pituitary sits in the sella turcica

Slide 2

  • Note the capsule
  • Anterior pituitary = top, wrapping around the pars intermedia
  • Colourful colloid present in the pars intermedia
  • Posterior pituitary = bottom
  • Question before = draw a pituitary gland, some cell types, and a hormone per cell type

Anterior pituitary:

  • Basophils = blue
  • Acidophiles = red
  • Chromophobe = transparent

Posterior pituitary:

  • Lots of nerve axons
  • Pituicytes
  • Herring bodies

Pars intermedia

  • Have Rathke's cysts bodies (blobs of hormone)
  • MSH is produced here (melancyte stimulating hormone)
    • Acts on pineal body and on the skin

Slide 3

  • Pituitary gland
  • Dangley bit to the right = pars tuberalis, lots of blood vessels (releasing hormones from the hypothalamus come down these blood vessels, move into the anterior pituitary and stimulate those cells to release their hormones). Pars tuberalis wraps around the infundibulum (connecting stalk), that connects to the supraoptic and paraventricular nuclei.
  • On the left, you've got the anterior pituitary at the top, pars intermedia in the middle, and posterior pituitary at the bottom.
  • Anterior pituitary = basophils, acidophils, chromophobes
  • Pars intermedia = colloid, cells that make the colloid live in follicles like in the thyroid. Here they're making MSH.
  • Posterior: pituicytes, Herring bodies, blood vessels

Slide 4

  • Adrenal gland
  • Top = capsule (collagen)
  • Beneath that = cortex
    • Zona glomerulosa = balls/clusters of cells
    • Zona fasciculata = run in cords, lots of blood vessels (sinusoids), has lipid vacuoles
    • Zona reticularis = branching network of cords of cells

Functions:

  • ZG secrete mineralocorticoids
  • ZF and ZR secrete glucocorticoid hormones e.g. cortisol, in response to ACTH from the anterior pituitary in response to CRH)
  • Sex hormones are secreted by ZR
  • Beneath that = medulla (lots of blood vessels)
    • Secrete adrenaline and noradrenaline (a weaker form of adrenaline)
    • Produced by chromaffin cells
    • Medullary release of hormones is under the control of the autonomic nervous system
  • Three types of capillaries = continuous, fenestrated, sinusoids

Epic Wikipedia pages to memorise

Links

Pathology

  • Pituitary disease
    • Hyperfunction: arises because of an actively secreting adenoma or a hypothalamic tumour inducing hypersecretion (usually trophic hormone; almost all revolve around increased number of cells (1. due to things going wrong in hypothalamus {doesn't happen much} 2. hyperplasia or neoplasm {more common, mostly neoplasm}))
      • Neoplasms of the pituitary are not typically
      • Pituitary gland sits in sella turcica (surrounded by the sphenoid bone and petrous part of the temporal bone, with one flap of the dura mater, above which is the optic chiasma)
        • Quite literally caught between a rock (sphenoid/temporal bone) and a hard place (fibrous dura mater)
    • Hypofunction: results from destruction of normal tissue by an adenoma or other mass lesion, an infarct, or following surgical or radiation therapy

Options:

  1. Hyperfunction, if the cells proceed to grow and increase their production
  2. Hypofunction: Expands, squashed blood vessels, infarction, resulting in the
  3. Slow expansion, gradually pushes superior structures upwards, squashing the optic chiasma
    • At the chiasma, the two nasal parts of the retina (which detect temporal field) - therefore lose half a visual field on the temporal side (bitemporal hemianopia)

Rathke's pouch tumour (oral endoderm) is

  • Effects of pituitary adenomas
    • Hypersecretion of one or more hormones
      • Prolactin = 30%
      • ACTH = 15%
      • Growth hormone = 15%
      • Growth hormone + prolactin = 10%
      • FSH + LH (low levels) = 15%
    • Mass effects
      • Reduced secretion of other anterior pituitary hormones
      • Diabetes insipidis
      • Visual disturbances
      • Pain due to compression of the dura mater
      • Signs of raised intracranial pressure

Slide 5

  • Pituitary section
  • Poorly handled, H&E stain
  • All looks the same; tumour proliferation of one clone of cells
  • Very vascular (like all endocrine tissue)
  • Take home message: 1) monomorphic and 2) vascular
  • Location is important - bad place of expansion that can damage surrounding structures
    • Bad pituitary adenoma - squashes the good pituitary tissue
    • Good pituitary adenoma - squashes the optic chiasma and you get visual disturbance
  • Link above shows a dog pituitary tumour; very vascular, lots of monomorphic cells, squashing of adjacent brain tissue; squashing of residual pituitary tissue (nearby)
    • Technically this is a benign tumour (not invading, metastasising), but is not harmless ("malignant by position"). This is treatable (surgically and with radiation).

Slide 6

  • Everything is dead
  • Around the pituitary (near capsule), there are some cells that are viable, arranged in groups. Coagulative necrosis (cell outlines with no nuclei in the middle)
  • Infarct = area of ischaemic necrosis
  • Middle = necrotic, periphery = not necrotic
  • Pituitary expands, infarct, causes necrosis of pituitary
  • Postpartum pituitary necrosis: pituitary enlarges in pregnancy. Postpartum, there can be a loss of blood pressure that results in infarction and coagulative necrosis.