Exam I Flashcards
Role of endocrine system
homeostasis
Main endocrine product
Hormones go directly into the interstitium or directly to the blood for affecting different target cells
Main endocrine product
Hormones
Hormones and Target Cells
hormones bind to specific receptors either on the surface or within the cells. They typically generate second messengers
Structural groupings of hormones
Peptides and proteins -
steroids - testosterone
amino acid derivatives - thyroid hormones, epinephrine
fatty acid derivatives - eicosanoids
features of endocrine systems
ductless, cells are epitheliod in appearance often arranged in cords or clusters, sparse CT, very vascular and often fenestrated (leaky) sinusoidal capillaries
hypophysis (pituitary gland) role
the relay station, feedback from target organs and the brain controls its responses
Developmental biology of hypophysis
1) neurohypophysis: downward extension form the floor of the hyothalamus (diencephalon)
2) adendohypophysis develops as a pouch-like ectodermal outpocketing of the oral cavity
(stomodeum) , it surrounds the neurohypophysis
Pictures in the notes
hypophysis (Pit. Gland) morphology
saddle-shaped depression of the sphenoid bone (sella turcica). It
has two distinct parts (neurohypophysis and adenohypophysis) with vascular connections. The two parts will be
covered individually followed by an explanation of the vascular connection.
Neurohypophysis (posterior lobe)
extension of the nervous system.
3 regions
median eminence, infundibular stalk, neural lobe
Stroma
astroglial-like stromal cell called pituicyte
Hypothalmic nuclei
neuron cell bodies in the parenchyma that produce the neurosecretory products
Neurosecretory products of parenchyma
The secretion is transported down their axons and stored within
axonal dilatations
stimulation of hypothalamic nerve bodies…
produces an axon potential that travels
down the axon and results in the release of the neurosecretion to nearby
(fenestrated) capillaries.
Adenohypophysis (anterior lobe)
has cells that are epitheliod (i.e.‘epithelial-like’) which
is understandable since it develops as an outpocketing of the oral cavity, an epithelial lined cavity.
3 regions
pars tuberalis, pars intermedia, pars distalis
pars tuberalis
Surrounds median eminence/ infundibular stalk. Very vascular (contains part of venous portal system vessels) Basophilic cells with melatonin receptors i.e. may have role in photoperiod regulation
Pas intermedia
Between pars distalis and neural lobe of neurohypophysis (large ruminants have ‘Wulzen’s cone’ i.e. pars distalis type cells) Basophilic cells (melanotropes) – produce melanocyte stimulating hormone. (hypothalmic control)
Pas distalis
Largest, most distal part of pituitary. Basophilic and acidophilic staining cells (hypothalamic control via a venous portal system)
Somatotrope
Growth hormone
PD
lactotrope (mammotrope)
prolactin
PD
Thyrotrope
TSH thyrotropin
PD
Corticotrope
corticotropin (ACTH)
PD
gonadotrope
FSH, LH
PD
Chromophobe
Possibly a degranulated cell
small, no granules
PD