ENDOCRINE SYSTEM Flashcards
how do cells communicate?
contact-dependent
paracrine
synaptic
endocrine
what does the endocrine system consist of?
Discrete glands & tissues: Chemical messengers
where do the chemical messengers enter?
Enter bloodstream: dispersed throughout body
what cells do the chemical messengers exert an effect on?
target cells
what are target cells?
specific high affinity receptors
what is the function of endocrine cells?
secrete hormones
what do endocrine cells gather to form?
specialised organ/gland
adrenal, pituitary, pineal
what else can endocrine cells form?
discreet clusters in another specialised organs -ovary, testis, pancreas
where might endocrine cells be dispersed?
singly amongst cells in other
epithelial tissue
diffuse enteroendocrine system in gut
what is the pituitary gland?
Multifunctional gland: secretes large number of hormones
what does the pituitary gland activate?
peripheral endocrine cells -adrenal, thyroid, testis, ovary
where is the pituitary gland?
under brain linked by pituitary stalk
what is the structure of the pituitary gland?
Anatomically divided – anterior & posterior
what is the anterior pituitary?
Epithelial tissue with 3 distinct components
what are the 3 components of the anterior pituitary?
pars distalis
pars tuberalis
pars intermedia
what is the pars distalis?
major portion of gland
what is the pars tuberalis?
layer of cells running up stalk
what is the pars intermedia?
narrow band bordering P lobe
what are the 3 cell types in the anterior pituitary?
acidophils
basophils
chromophobes
what stain do acidophils produce?
acidic dyes
what stain do basophils produce?
basic dyes
what stain do chromophobes produce?
no cytoplasmic staining
what are the 2 types of acidophils?
somatotrophs
lactotrophs
what are somatotrophs?
Stimulates cell growth & replication
increase rate of protein synthesis
increase GH production=acromegaly
what are lactotrophs?
prolactin
Stimulates mammary gland development
Pregnancy/nursing stimulates milk production
increase in size & number
what are the 4 types of basophils?
corticotrophs
gonadotrophs
thyrotrophs
chromophores
what is an example of corticotrophins?
Adrenocorticotropic hormone (ACTH)
what is an example of gonadotrophs?
FSH & LH
what are corticotrophins?
Release of steroid hormones from adrenal cortex
e.g. glucocorticoids (cortisol)
what are gonadotrophs?
Regulate activity of gonads (ovary & testis)
what is FSH?
F-follicle development & secretion of oestrogen’s
M-sustentacular cells
what is LH?
Induces ovulation / estrogen & progesterone
what is thyrotrophs?
Thyroid stimulating hormone (TSH)
stimulates growth thyroid epithelial cells
Release of thyroid hormones
what is chromophores?
fail to stain- too few granules
may be any of 5 types
what is found in the posterior pituitary?
Pars nervosa (neural lobe)
what is the Pars nervosa (neural lobe)?
Continuation of hypothalamic region of brain into pituitary stalk
Contains axons of hypothalamic neurons
what 2 hormones are released by the posterior pituitary?
Antidiuretic hormone (ADH) oxytocin
what does ADH do?
decrease H2O loss by kidneys
what does oxytocin do?
Promotes contraction of smooth muscle uterus &
myoepithelial cells breast
where is the pineal gland?
Located under brain –composed of lobules of specialised cells
what are the 2 types of specialised cells in the pineal gland?
pinealocytes
glial cells
what are pinealocytes?
Neuron-like cells which produce melatonin
what are glial cells?
Bipolar elongated cells that run between nests of pinealocytes – indistinct unless stained
what is melatonin?
Secreted by pineal gland responds to light & regulates seasonal changes in the body
what effect does ageing have on melatonin?
Declines with aging & is thought to trigger changes throughout the endocrine system
what is the structure of the thyroid gland?
Bilobed
Curves across anterior surface of trachea
Lobes connected isthmus
what are the 3 hormones in the thyroid gland?
Thyroxine T4
Triiodothyronine T3
Calcitonin
what are T3 and T4 involved in?
metabolism
what is calcitonin involved in?
calcium homeostasis
what is a follicle of the thyroid gland?
structural unit
hollow spheres of cuboidal epithelial cells
what is the lumen of the follicle filled with?
colloid
what is surrounding each follicle?
basement membrane enclosing C-cells in a parafollicular position
what is an under active thyroid?
Increase colloid, flattened cells
what is an overactive thyroid?
Decrease colloid, tall cells
where are the parathyroid glands?
Embedded in posterior surface of thyroid
Separated by dense capsular fibres of thyroid
what do the parathyroid glands secrete?
Parathyroid hormone (PTH)
what is PTH involved in?
calcium homeostasis
what are the 2 cells in the parathyroid glands?
chief cells
oxyphils
where is the pancreas?
Lies within abdominopelvic cavity
what does the exocrine pancreas contain?
Pancreatic acini arranged in clusters
what does the endocrine pancreas contain?
Islets of Langerhans (pancreatic islets)
Small groups cells scattered among the exocrine cells
what do the pancreatic islets contain?
Extensive capillary network:hormones to blood stream
Each islet contains 4 cell types
what are the alpha cells?
Glucagon
increase blood glucose and glycogen breakdown liver
what are beta cells?
Insulin
increase blood glucose and glycogen synthesis liver
what are delta cells?
Inhibiting peptide
Inhibits release of glucagon & insulin
Slows food absorption + enzyme secretion
what are F cells?
Pancreatic polypeptide
Inhibits gall bladder contractions
Regulates production of some pancreatic enzymes
what is the adrenal gland?
2 distinct endocrine systems within one organ
what does the adrenal gland contain?
adrenal cortex
adrenal medulla
what is the adrenal cortex?
outer layer
Secretes steroid hormones (cholesterol)
what is the adrenal medulla?
inner layer
Neuroendocrine component - epinephrine (adrenaline) & norepinephrine (noradrenaline)
what are the 3 distinct zones of the adrenal cortex?
zona glomerulus
zona fasciculata
zona reticularis
what is the zona glomerulus?
Outer (smallest)
Mineralocorticoids (aldosterone)
what is the zona fasciculata?
Middle (biggest, yellow)
Glucocorticoids (cortisol & corticosterone)
what is the zona reticularis?
Inner (pale brown)
Androgens (DHEA & androstenedione)
how does the foetus/neonate adrenal cortex differ?
cortex is large & has 4th external layer – involutes after birth
where is the adrenal medulla derived from?
from neural crest & part of neuroendocrine system
what is the structure of the adrenal medulla?
Usually brown in colour
Cells - large pale staining nuclei & fine, granular cytoplasm
how are the cells arranged in the adrenal medulla?
Cells polyhedral in shape – arranged in clumps, cords, columns & surrounded by rich network capillaries
what is the effect of cortisol on age?
increases with age
what hormones decline with age?
sex hormones
melatonin
growth hormone
