L8) Endocrine tissues and glands Flashcards
what is the location and secretion(s) of thee anterior pituitary gland?
location: base of the brain
secretes: thyroid stimulating hormone (TSH)
what is the location and secretion(s) of the posterior pituitary gland?
location: base of the brain
secretions: antidiuretic hormone (ADH), vasopressin, oxytocin
what is the location and the secretion(s) of the thyroid gland?
location: anterior to the trachea (two lobes)
secretions: thyroxine (T4), triiodothyronine (T3)
what is the location and secretion(s) of the parathyroid gland?
location: lie on dorsal surface of the thyroid gland (4 glands - 2 pairs)
secretions: parathormone (PTH)
what is the location and secretion(s) of the adrenal glands?
location: top of each kidney (2 sections - inner medulla and 2 cortex surrounds it)
secretions: cortex secretes corticosteroids; small amounts of androgen, oestrogen and progestin
what is the location and secretion(s) of the pancreas?
location: left of and behind the stomach (is both exo/endocrine gland)
secretions: exocrine secretes digestive enzymes into the duodenum; endocrine - islets of langerhans: alpha cells secrete glucagon and beta cells secrete insulin
what is the endocrine control point?
hypothalamus - links endocrine to nervous system
what mechanisms does the hypothalamus regulate?
thermoregulation
plasma osmolality (via osmoreceptors)
heart rate, blood pressure
feeding
circadian rhythms
stimuli from ANS
emotion, sexual behaviour, mood
lactation
how does the hypothalamus interact with the pituitary glands?
posterior pituitary - through nerves
anterior pituitary - through hypothalamus-hypophyseal portal system (blood)
how does the hypothalamus interact with the posterior pituitary? (detailed)
through neurosecretory cells (nerves) that span between the hypothalamus and the posterior pituitary
hormones produced are packaged in vesicles and transported through the axon, and stored in the axon terminals that lie in the posterior pituitary
when stimulated, the action potential triggers the release of the stored hormones to a capillary network within the posterior pituitary
how does the hypothalamus interact with the anterior pituitary gland? (detailed)
through blood vessels
hormones are produced by specialized neurons of the hypothalamus
hormones are released into a capillary network (CN) and transported through veins (hypophyseal portal veins) to a second CN that supplies the anterior pituitary
the hormones then diffuse from the secondary CN into the cells of the anterior pituitary
this initiate the production of specific hormones by the anterior pituitary
What hormones are produced and released from the posterior pituitary?
oxytocin
antidiuretic hormone (ADH) (vasopressin)
what hormones are released from the hypothalamus to the anterior pituitary?
ACTH - adrenocorticotropic hormone
TSH - thyroid-stimulating hormone
GH - growth hormone
PRL - prolactin
FSH - follicle-stimulating hormone
LH - luteinising hormone
(MSH - melanocyte-stimulating hormone)
how does the endocrine system develop?
at week 5 gestation
arises from all 3 germ layers
the endoderm gives rise to the pharyngeal pouches, the pharynx, the neurohypophyseal bud, foregut
the mesoderm gives rise to intermediate mesoderm
the ectoderm gives rise to hypophyseal pouch (Rathke pouch) and neural crest
where does the pituitary derive from? (embryo)
neurohypophyseal bud and hypophyseal pouch
where does the thyroid derive from? (embryo)
floor of the pharynx
where does the parathyroid and thymus derive from? (embryo)
3rd and 4th pharyngeal pouches
where does the pancreas develop from? (embryo)
foregut
where does the adrenals develop from? (embryo)
intermediate mesoderm and neural crest
what is the location and structure of the thyroid gland?
location: base of neck, above second tracheal cartilage
structure: two wings (left & right) joined by isthmus
what are parafollicular cells?
neuroendocrine cell
what is the function of parafollicular cells?
humoral
to monitor plasma calcium concentrations and decrease Ca2+ levels (counteract PTH)
by producing peptide hormone thyrocalcitonin
what are the major and minor effects of parafollicular cells?
major effect: inhibits osteoclast activity in bone
minor effect: inhibits renal calcium and phosphate re-absorption in the tubular cells → more calcium and phosphate excreted
what are the histological features of a thyroid gland?
thyroid follicle - epithelial cells surrounding colloid-containing pools, called follicles
parafollicular cells - pale-staining cells
what is the location and structure of the parathyroid gland?
four “grains of rice” (nodular) that sit on the posterior aspect of the thyroid
what is the function of the parathyroid gland?
humoral
regulates plasma calcium concentration
by the production of parathyroid hormone PTH
(negative feedback)
how is the plasma calcium concentration regulated by the parathyroid gland?
when plasma calcium ↓ = PTH is produced (parathyroid hormone)
PTH causes bones to release calcium into blood
it prevents calcium loss by kidneys; absorb more calcium from the GI tract
what is the location and structure of the adrenal glands
sit on top of the kidneys
right adrenal = upside down pyramidal
left adrenal = crescent shaped
adrenal glands have two parts: inner medulla and outer cortex
what are the histological features of the adrenal medulla?
chromatffin cells - a parenchyma of large pale staining epitheloid cells
what is the structure of the adrenal cortex?
three layers:
outer - zona glomerulosa
middle - zona fasciculata
inner - zona reticularis
what is the function of the zona glomerulosa?
produces aldosterone
regulates BP
what is the function of the zona fasciculata?
produces glucocorticoids
mobilises fats, proteins and carbs
what is the function of the zona reticularis?
produces androgen precursors
what is the main indication of the adrenal cortex?
stress response
what is a stress response?
state of real or perceived threat to homeostasis
what does a stress response induce?
initiates a number of behavioural and physiological changes
improves individuals chance of survival when faced with homeostatic changes
what behavioural changes are induced due to stress response?
increased awareness
improved cognition
euphoria
enhanced analgesia
what psychological adaptations are induced due to stress response?
increased cardiovascular tone
increased respiratory rate
increased intermediate metabolism
decreased vegetative functions (feeding, digestion, growth, reproduction and immunity)
what hormones are involved in the stress response?
adrenal cortical hormones:
