Glands - Endocrine and Exocrine Flashcards
what is the endocrine system responsible for
the synthesis and secretion of chemical messengers known as hormones
how do hormones travel
through the bloodstream
what do hormones act upon
specific target organs and tissues
how do some other hormones act
locallyy - they arrive at the site via microcirculation
what are endocrine glands composed of
islands of secretory epithelial cells, intervening support tissue
what are endocrine glands rich with
blood and lympathic capillaries
where do secretory cells discharge hormones
into the space where it is rapidly absorbed into the circulatory system
what are some chemicals that act as hormones
- protein and glycoprotein molecules
- small peptide molecules
- amino acid derivatives
- steroids derived from cholesterol
what are the three main parts of the endocrine system
the major endocrine organs
the endocrine components within other solid organs
diffuse endocrine system
what is the major function of major endocrine organs
the synthesis, storage and secretion of hormones
what are examples of major endocrine organs
thyroid and adrenal glands
some endocrine glands are components within other solid organs. what organs?
- pancreas
- ovary
- testis
- kidney
what is meant by the diffuse endocrine system
scattered individual hormone cells within an extensive epithelium
what is the major function of the diffuse endocrine system
paracrine
what do paracrine hormones do
act on adjacent non endocrine cells, rather than entering the bloodstream and producing systematic effects
what is the pituitary gland
- a small gland at the base of the brain beneath the third ventricle.
- it is divided into anterior and posterior parts with different embryological origins, functions and control mechanisms
what controls secretion of the pituitary hormones
hypothalamus - this is under the influence of nervous stimuli from higher centres in the brain
what are the two main functional groups of pituitary hormones
hormones that act directly on non endocrine tissues
hormones that modulate the secretory activity of the other endocrine glands
what are some examples of pituitary hormones that act directly on non endocrine tissues
growth hormone
prolactin
ADH
oxytocin
MSH
what are some examples of pituitary hormones that modulate the secretory activity of other endocrine glands
thyroid stimulating hormones, ACTH, gonadotrophic hormones, follicle stimulating hormone, LH
which glands can be described as pituitary dependent endocrine glands
thyroid gland
adrenal cortex
gonads
what is the most common disease of the pituitary gland
pituitary adenoma - benign tumours
what is pituitary adenoma a disease of
the pituitary gland
what is the thyroid gland
an endocrine gland found on the upper part of the trachea, shaped like a butterfly
why is the thyroid gland unique
stores large amounts of hormone in an inactive form within extracellular compartments in the centre of the follicles
how many different types of hormone does the thyroid produce
two
what is the main bulk of the thyroid gland formed from
epithelial downgrowth from the fetal tongue
what are calcitonin secreting cells derived from
ultimobranchial element of the fourth branchial pouch
what is thyrotoxicosis
this occurs when an excess of circulating thyroid hormone causaes clinical symptoms due to systemic effects of the thyroid hormone. symptoms include palpitations, fatigue, weight loss and anxiety
what is graves disease a cause of
pathological thyroid hyperplasia
what are parathyroid glands
small endocrine glands closely associated with the thyroid gland
how many parathyroid glands are there and where are they situated
4 - some have 5 or 6 - two pairs of glands on each side of the thyroid
what does the parathyroid hormone do
regulate serum calcium and phosphate levels
how does the parathyroid raise calcium levels
- direct action on bone
- direct action on the kidney
- promotion of the absorption of calcium from the small intestine
what is secretion of the parathyroid hormone stimulated by a decrease in
calcium levels in the bloodstream
what is hyperparathyroidism
when the parathyroid overworks
what is hypoparathyroidism
when the parathyroid underworks
what is the adrenal gland
an endocrine gland applied in the upper pole of each kidney. one is the adrenal cortex and one is the adrenal medulla
what does the adrenal cortex produce
steroid hormones
what are some examples of hormones produced by the adrenal cortex
- mineralocorticoids
- glucocorticoids
- sex hormones
what does the adrenal medulla produce
catecholamine hormones
what are some examples of catecholamine hormones
adrenalin and noradrenalin
what does destruction of the adrenal medulla and cortex lead to
failure of secretion of all adrenal corticol hormones, leading to addisons disease
what causes addisons disease
destruction of both adrenal glands which leads to failure of secretion of all adrenal corticol hormones
what is meant by hyperadrenalism
excess secretion of corticol hormones - this can be caused by a benign tumour
what does the embryonic epithelium of the pancreatic ducts lead to
both potential exocrine and endocrine cells
what are the main secretory products of the endocrine pancreas
insulin and glucagon
where is the pineal gland located
in the midline of the brain
what is the pineal gland connected to the brain via
a short stalk containing nerve fibres where some actually communicated with the brain
what does the pineal gland produce
melatonin
what is melatonin production induced by
darkness - inhibited by light via sympathetic nerves transmitting messages from the eye through the superchiasmatic nucleus
what is the diffuse neuroendocrine system
a scattered system of neuroendocrine cells that secrete hormones and active peptides
what does the diffuse neuroendocrine system possess
characteristic membrane bound neurosecretory vesicles that are usually spherical with an electron dense core
when is the diffuse neuroendocrine system particularly important
the gastrointestinal and respiratory tracts
what hormones can be secreted by the neuroendocrine system
some are true endocrine hormones, some are paracrine hormones
what can cells of the neuroendocrine system give rise to
tumours known as small cell marcinoma
what is the ectoderm
the outer most layer of cells
what are fenestrated capillaries
leakier than continuous capillaries - small pores in addition to small gaps which allow for the exchange of larger molecules
can the secretions of endocrine glands be stored and released after stimulation
yes
what are the different patterns of secretion
chronic, acute and episodic
what does a chronic pattern of secretion indicate
secretion occurs in the same period, at the same time and in the same amounts
what does an acute pattern of secretion indicate
depends on stimulus
what does an episodic pattern of secretion indicate
follows certain episodes like mealtime
what is humoral stimuli
hormones secreted in reponse to blood borne molecules eg insulin in response to glucose in the blood
what kind of hormone regulation is insulin in response to glucose
humoral
what is neural stimuli
this is when neurons stimulate hormone production
what is hormonal stimuli
hormone secretion stimulates another hormone to be secreted
what are the different classes of hormones
proteins and polypeptides
steroids
derivatives of amino acid tyrosine
which glands produce hormones under the classification of proteins and polypeptides
pancreas, parathyroid
which glands produce steroid hormones
adrenal cortex, ovaries and placenta
which glands produce derivatives of amino acid tyrosine
adrenal medulla and thyroid
what hormone does the thyroid gland produce
thyroxin
what does thyroxin do
it regulates metabolism
what is the thyroid gland lined with
a layer of follicular epithelium - usually cuboidal epithelium
what are parafollicular cells
neuroendocrine cells
how does the parathyroid hormone affect calcium levels
- production of the parathyroid hormone affects osteoclast cells
- no intake of calcium leads to secretion of the parathyroid hormone
- this affects osteoclast cells to break down the bone
- this breakdown of bone releases minerals including calcium into the blood
what is hyperparathyroidism
too much parathyroid is released
what is an osteoclast
a big cell containing nuclei that breaks down bone
why is osteoporosis more common in post menopausal people
when estrogen levels decrease, the activity of osteoclasts becomes higher due to inhibition, which means more bone is being broken down
what is the parathyroid cell made up of
chief cells which synthesise and secrete the parathyroid hormone, and oxyphil cells which have an unknown function
how are exocrine secretions released
through ducts that are opened directly onto the epithelial surface
how are exocrine glands classified
by structure or method of secretion
what are the two classifications for exocrine glands
unicellular, when they are made of one cell each, these include mucus glands which line the trachea.
multicellular, which form a sheet or pocket of gland cells
what occurs in a compound exocrine gland
multiple, branched ducts
what are branched exocrine glands surrrounded by
fibrous connective tissue capsules
what do the branches of compound exocrine glands do
they subdivide the gland into lobules composed of alveoli or tubules. secretions from the lobules are drained by a complex, branching duct system
what is the purpose of endocrine glands
regulate bodily function and maintain homeostasis
what is an example of a neural response
sympathetic nervous system stimulates the release of epinephrine
what is an example of hormonal response
hormones from pituitary gland stimulate the testes to make testosterone
what are the main parts of the endocrine system
- hypothalamus
- pituitary gland
- parathyroid gland
- thymus
- adrenal gland
- pineal gland
- thyroid
- pancreas
- ovary
- testis
what is parenchyma
glandular tissue
what divides the glandular tissue into lobes in branched exocrine glands
septa
what are interloba septa
the lobes produced from the division of glandular tissue by septa
what do intralobular septa divide lobes into
lobules
what are interlobar ducts lined by
stratified columnar epithelium
what are interlobular ducts lined by
pseudostratified columnar epithelium
what is the function of myoepithelial cells in branched glands
they contract and squeexe the secretions from the acini along the duct
what are the types of secretion
serous
mucous
mixed glands
what are serous secretions like
watery secretion containing enzymes
what is found in mucous secretions
they secrete mucines which hydrate to form mucous
what do mixed glands have
both serous and mucous
what happens to cells after the hormones separate from the duct
they die
what are the different salivary glands
parotid, submandibular, sublingual
where are the minor salivary glands
scattered around the oral cavity
what can both minor and major salivary glands be affected by
diseases or medications which can lead to dry mouth
what is xerostomia
dry mouth
which form of salivary gland can tumours arised in
both
what are salivary glands made up of
secretory acini - acini meaning a rounded secretory unit - and ducts
what are the two types of secretions from salivary glands
serous and mucuos
what is serous acinus secretion from salivary glands
proteins in an isotonic watery fluid
what is mucous acinuss secretion from salivary glands
mucin lubricant
what kind of acini is found in the sublingual glands
mainly mucous
what kind of acini is found in the parotid glands
mainly serous acini
what kind of acini is found in submandibular glands
a mixture of mucous and serous acini
does mcous acini stain more or less weakly than serous acini
more weakly
what kind of nuclei does mucous acini have
flattened
describe serous acini
has a granular cytoplasm due to enzyme production and round nuclei
what kind of gland is in the exocrine pancreas
branched tubuloacinar gland
what are the compartments of a branched tubuloacinar gland
head, neck, body, tail
what is the functional unit of the exocrine pancreas
acinus
are there are myoepithelial cells or strated ducts in the exocrine pancreas
no
what are examples of enzymes secreted from the exocrine pancreas
proteases and amylases
what are islets of langerhans
clusters of cells in the pancreas that produce hormones like insulin and glucagon
what makes up the pancreas endocrine
islets of langerhans
how much of the pancreas is taken up by the endocrine system
2%
what are the three major cell types of the islets of langerhan
alpha
beta
delta
what do alpha islets of langerhans produce
glucagon
what do beta islets of langerhans produce
insulin
what do delta islets of langerhans produce
somatostatin
what are some diseases of the pancreas
pancreatic cancer
cystic fibrosis
diabetes mellitus
which portion of the pancreas is affected in cystic fibrosis
exocrine
what is the most common endocrine disorder in the pancreas
diabetes mellitus
what occurs in type 1 diabetes mellitus
the beta islets of langerhans are destroyed - dependent on insulin.
how common is type 1 diabetes
only make up 5-10% of all diabetic patients
explain type 2 diabetes
tissues lose their sensitivity to insulin so it becomes ineffective
what are the oral implications of diabetes
- periodontitis
- dry mouth
- susceptibility to infection
what are some disorders of the exocrine system
reduced hormone release
excessive hormone release
hormone resistance
what is hypofunction
reduced hormone release
what is hyperfunction of the endocrine system
excessive hormone release
what is diabetes mellitus
hormone resistance
when can endrocrine changes be seen
in pregnancy, menopause, stress and obesity
what halogen does the thyroid gland require to produce thyroxin
iodine
what are the hormones that are produced by the thyroid gland that require iodine
T3 and T4
what does the sublingual gland produce
mucous
what does the parotid gland produce
serous
what does the submandibular secrete
serous-mucous
what are the three layers of the adrenal cortex
zona glomerulosa, zona fasiculata, and zona reticularis
what is the zona reticularis
the thin, innermost layer of the adrenal cortex and lies next to the adrenal medulla. consists of an irregular network of branching cords and clusters of glandular cells, separated by numerous wide-diameter capillaries. this layer secretes small quantities of androgens and glucocorticoids
what is the zona fasiculata
the middle and broadest of the three corticol zones. it consists of narrow columns and cords of cells, often only one cell thick. it secretes glucocorticoid and mainly the hormone cortisol, which raises blood glucose levels and increases cellular synthesis.
what is the zone glomerulosa
this lies beneath the capsule, and contains secretory cells arranged in rounded clusters. it is composed of cells arranged in irregular ovoid clusters separated by delicate fibrous trabeculae. this zone secretes the mineralcorticoid hormones, principally aldosterone.
