Pituitary Test
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| A. Downgrowth from developing hypothalamus - neural ectoderm - posterior pituitary
Upgrowth of oral ectoderm from roof of mouth - anterior pituitary
Development directed by different transcription factors for each sectionB. Used for reproduction
Women - act in ovary via GPCR - FSH for follicle development and LH for ovulation and progesterone production
Male - act in testes - LH for testosterone production and FSH for sperm productionC. A polypeptide hormone from POMC precursor - secreted by corticotroph cells
GPCR coupled to cAMP
Stimulates secretion of cortisol from adrenal cortex in stress
Stimulates growth of adrenal cortex
D. Several reports of altered hypothalamic and pituitary hormone secretion, clinical disruption of circadian secretion and delayed puberty
Molecules in the environment can disrupt pituitary functionE. Stress e.g. infection, pain etc stimulates hypothalamus to secrete corticotrophin releasing hormone
Anterior pituitary corticotroph cells release ACTH
Adrenal cortex secretes cortisol
Long feedback loop
F. Released in pulses - increase in ACTH followed by increase in cortisol
Peaks at 7am to prepare the body for waking
Disruption of this leads to increased risk of CVD, T2 diabetes and depression
Best health outcomes when hormones given by this rhythmG. Prominent vessels in the pituitary stalk
Gonadotrophs directly adjacent to capillaries - allows rapid diffusion into bloodstream
Pituitary can adapt to demands e.g. during pregnancy, lactation, menopause, stress, seasons, fetal stress and pubertyH. Hypothalamus secretes gonadotrophin releasing hormone
Anterior pituitary gonadotroph cells release LH and FSH
Ovary - oestrogen and progesterone
Testes - testosterone
Released in pulses every 90 mins
Cyclical release in menstrual cycleI. Lots of mitochondria
Euchromatin - high transcription rate
Hormones stored in secretory granules
RER
Majority of exocytosis occurs at boundary with capillaries - directedJ. Anterior - TSH, ACTH, LH, FSH, GH, prolactin
Posterior - Oxytocin and vasopressin (ADH)K. The pituitary gland sits at the base of the skull in a recess of the sphenoid bone called the sella turcica
This is a bony cavity in which the pituitary sits
Relatively protected from trauma except the stalk
Tumours cannot expand within the fossa L. Hormonal effects - hormone secreting tumours effects depend on cell type - present as over excretion of the hormone
Mechanical effects - affect vision as tumour presses on optic chiasm - affects peripheral vision field leading to tunnel visionM. To produce and secrete eight peptide/glycoprotein hormones and in turn these hormones exert many functions important for health
E.g. PRL, ACTH, TSH, GH, LH, FSH, ADH and OxytocinN. Only pituitary hormone whose principle control is inhibitory
PRL production is stimulated by estrogen during pregnancy
Dopamine agonists e.g. bromocryptine suppress lactation
Pathology - prolactinomas hyper secrete PRL - cause infertility O. Stretch of cervix/vagina at parturition
Sucking - nipple stimulation causes milk ejection reflexP. Five endocrine cell types each secrete different trophic hormones
Cell types can be differentiated by antibody labelling and cell structure of tumours
Non-secretory supporting call types = Folliculo-stellates
These support the cells Q. Deficit - infertility in adult life - lack of sexual maturation
Excess - precocious puberty at age 4/5R. Neural stimulus depolarises neuron
AP down axon
Ca influx
Exocytosis
E.g. osmoreceptor cells outside BBB sense increased osmolarity and depolarise ADH neuronsS. Stimulus e.g. cold triggers hypothalamus to produce thyrotrophin releasing hormone
Anterior pituitary thyrotroph cells then secrete thyroid stimulating hormone
Thyroid then secretes T3 and T4
Long feedback loop
Pathology of TSH secretion is rareT. Hypothalamus is superior
Optic chiasma is directly in front (where optic nerves cross)
At the base of the brain behind the nasal cavity |
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