Comparative Anatomy and Microanatomy of the Endocrine Glands Flashcards
What do endocrine organs do?
preserve homeostasis
they also secrete hormones directly to blood/lymph/tissue fluid
Describe a characteristic of endocrine organs?
they are ductless organs
neurohormonal system?
endocrine and nervous system are integrated
where are endocrine organs derived from?
from the 3 germ layers
where is the hypothalamus located in the brain?
at the ventral part of the brain
what does the hypothalamus do?
it is the regulator of the endocrine and nervous system - maintains homeostasis
what bodily functions does the hypothalamus regulate?
temp, thirst, hunger, sexual behaviour, blood volume etc. maintain homeostasis
what does the hypothalamus coordinate?
coordinates the activity of the pituitary gland through the secretion of peptides and amines
what are the two types of hormones produced by endocrine glands?
releasing and inhibitory
where is the pituitary gland integrated?
with the hypothalamus (structurally and functionally)
pituitary gland location?
suspended below the hypothalamus by a narrow stalk (infundibular and hypophysial stalk)
Where does the pituitary gland lie within?
within bony cavity called the hypophysial fossa (sella turcica) of the sphenoid bone
shape and size of pituitary gland?
small, oval gland
where in the brain is the pituitary gland located?
between rostrally optic chiasm and the caudally mammillary bodies
what is the pituitary gland controlled by?
by CNS and feedback from target organs
Adenohypophysis?
the anterior lobe of the pituitary gland
Neurohypophysis?
the posterior lobe of the pituitary gland
How many parts is the Adenohypophysis made up from?
3 (sometimes 2)
How many parts is the Neurohypophysis made up from?
3
How is the Rathke’s pouch developed
during embryonic development, the roof of the mouth bulges upwards (invaginates) to form, structure known as Rathke’s pouch
What is the Rathke’s pouch?
It is an ectodermal outpouching of the stomodeum - it is also known as the hypophyseal
when does the Rathke’s pouch normally close?
normally closes in fetal development
Acidophils?
cells that contain the polypeptide hormones - will stain red or organe
Basophils?
cells that contain the glycoprotein hormones - will stain bluish colour
Chromophobes - cytoplasms?
have a cytoplasm that stains really poorly
what is the adenohypophysis (pars intermedia) closely associated with?
with pars nervosa
Describe the capillaries in the adenohypophysis - pars tuberalis?
they are fenestrated, to enable passage of hormones from the secretory cells into the bloodstream
what do the cells of the pars tuberalis form?
cells form folding sheets (folds) and occasional cysts
Describe the lumen of the Neurohypophysis?
has a lumen, that’s continuous with the lumen of the brain’s third ventricle
What does the production of peptides and amines - by the hypothalamus influence?
they influence the pituitary gland to produced tropic hormones
Give an example of how the production of peptides and amines - by the hypothalamus influence?
corticotropin which in turn influences the production of cortisol by peripheral target tissues
trope?
because they turn on endocrine glands or support
Where are neurohormones from the hypothalamus released to?
to the hypothalamic-pituitary portal system
what do neurohormones bind to?
bind to receptors on endocrine cells
what does the hypophysial portal system regulate?
regulate their hormonal secretion (releasing or inhibiting)
what two hormones does the hypothalamic - hypophysial tract secrete?
ADH and oxytocin
What happens to the hormones secreted by hypothalamic - hypophysial tract?
they are placed in vesicles and transported and stored - each terminal stores either vasopressin or oxytocin
pineal gland aka?
epiphysis cerebri
what cells does the pineal gland contain and what are these cells responsible for?
contain pinealocytes
astrocytes
responsible for secreting melatonin
how are pinealocytes arranged?
arranged like cords, follicles
what are corpora arenacea?
AKA - brain sand
human pineal gland contains characteristic, extracellular concretions called corpora arenacea
melatonin important for?
for regulating biological rhythms e.g. circadian rhythms and season effects on breeding, sleep etc. innate immune response
where is the master biological clock that serves as the pacemaker for circadian rhythms?
located in the hypothalamic suprachiasmatic nucleus
what does the rhythm of the hypothalamic suprachiasmatic nucleus control?
controls the rhythm of melatonin secretion by the pineal gland via a polysynaptic pathway
Describe the retiono-pineal pathway?
light enters retina
suprachiasmatic nuclei
paraventricular nuclei
intermediolateral cell column of the spinal cord
cervical ganglia
pineal gland
What are the central glyocytes?
support cells in CNS
what is the thyroid gland attached to?
attached to trachea on the right and left side just caudal to the cricoid cartilage
what tracheal rings does the thyroid gland span?
spanning the initial five to eight tracheal rings
what are the lobes of the thyroid gland connected by?
by an isthmus - in pigs they are fused
what is the thyroid gland derived from?
derived from pharyngeal endoderm
size of thyroid gland is variable depending on what?
depending on heredity, environmental and nutritional factors
location of thyroid gland varies with…
with species
what is each gland of the thyroid gland embedded in?
in deep cervical fascia and divided into lobules
what do the lobules of the thyroid gland consist of?
they consist of many units called thyroid follicles
what is colloid made up of?
of a glycoprotein called thyroglobulin
what is colloid?
it is an inactive precursor of T3 and T4
adrenal cortex?
makes up 80% of organ
location of adrenal gland?
cranial-medial
what is the adrenal cortex derived from?
mesoderm
how many parts make up the adrenal cortex?
3
What are the three parts of the adrenal cortex?
the Zona Glomerulosa
the Zona Fasciculata
the Zona Reticularis
What is adrenal medula?
it is a modified sympathetic ganglion
What is the adrenal medulla innervated by?
innervated by preganglionic sympathetic nerves
what are the cells of the adrenal medulla?
the chromaffin cells
What are the two functionally and histologically distinct components of the pancreas?
exocrine and endocrine
what does the endocrine pancreatic tissue consist of?
small, discrete clusters of cells called islets of langerhans (pancreatic islets)
what percentage of cells in the pancreas is made up of pancreatic islets?
1%
pancreas endocrine activity is not controlled by…?
pituitary hormones
describe the gland of the pancreas?
lobulated and encapsulated
structure of adrenal gland?
outer –> inner
capsule, zona glomerulosa (closer to outside, closer to kidney), zona fasciculata, zona reticularis, medulla (inner and outer region)
what does the zona glomerulosa secrete?
secretes mineralocorticoids
what does the zona fasciculata secrete?
glucocorticoids
what does the zona reticularis secrete?
secretes sex steroids or androgens; oestrogens
what hormones does the adrenal cortex produce?
adrenocorticoid hormones
how many regions of the adrenal cortex are there?
three distinct regions
what is the adrenal gland?
paired glands located craniomedially to the kidneys
what surrounds the adrenal gland?
a capsule
how is the adrenal gland organised?
into peripheral cortex and central medulla
Which artery/vein passes over the adrenal gland?
phrenicoabdominal a.&v.
what % of the adrenal gland is the ‘cortex’?
80%
what is the parathyroid gland composed of?
it is composed of densely arranged cords of chief cells surrounded by a thin fibrous capsule
is the parathyroid gland paired?
usually there are two pairs (external and internal)
location of parathyroid gland?
they could be superficial or embedded to the thyroid gland
size of parathyroid gland?
only a few mm in diameter
location of parathyroid gland varies with what?
varies with species
what cell is responsible for synthesising, storing and secreting the parathyroid hormone?
chief cells of the parathyroid gland
what are chief cells also known as?
also called parathyroid or principal cells
what is the blood supply of the thyroid gland?
common carotid artery-thyroid artery
the right thyroid gland is close to what?
right gland is close to the common carotid artery, internal jugular vein, vagosympathetic trunk and tracheal duct
which nerve fibres does the thyroid gland receive?
both sympathetic and parasympathetic fibres
where are the sympathetic nerve fibres that the thyroid gland receives routed through?
routed through the cranial cervical ganglia
where are the parasympathetic nerve fibres that the thyroid gland receives routed through?
through the laryngeal branches of the vagus nerve
what two important nerves are close by to the thyroid gland?
the cranial and caudal laryngeal nerves
what are the follicles of the thyroid gland filled with?
filled with viscous protein rich fluid colloid
what are thyroid hormones synthesised in?
in colloid
what is colloid?
a substance that serves as an extracellular storage site
what cells are found within the walls of the thyroid follicles?
small Parafollicular cells
possible shaped of follicular cells?
follicular cells can be columnar, cuboidal, or squamous depending on their synthetic activity
what do follicle cells surround in the thyroid gland?
surround follicle cavity (which holds viscous colloid)
the follicular cells of the thyroid gland are the derivatives of what?
derivatives of the endoderm
what do the follicular cells of the thyroid gland secrete?
they secrete thyroid hormone
what do the lobules (that make up the thyroid gland) consist of?
many units called thyroid follicles
What is a vestigial eye?
many fish and amphibians have a median pineal eye and/or parietal/third eye
This is the pineal gland - it takes in information about light
in lower vertebrates, the pineal gland is sensitive to what?
it is directly photosensitive
pineal gland AKA?
Epiphysis cerebri
what is the pineal gland and where is it located?
part of the epithalamus and is located mid-brain
describe size and shape of pineal gland?
small organ and shaped like a pinecone
where is the pineal gland attached?
attached to the caudal end of the roof of the third ventricle directly before the rostral colliculi
which gland is the only gland to be directly influenced by the external environment via the retina?
the pineal gland
what hormone does the pineal gland secrete?
melatonin (derived from aa tryptophan)
how is neurohypophysis connected to hypothalamus?
by neural pathway
how is adenohypophysis connected to hypothalamus?
by vascular link
How does the neurohypophysis synthesise the hormones that it releases in to the blood?
releases the hormones into the blood that have been synthesised by the hypothalamus
How does the adenohypophysis synthesise the hormones that it releases in to the blood?
adenohypophysis itself synthesises the hormones that it releases into the blood
Why are the neurohormones of the neurohypophysis deposited directly into the capillaries?
because the neurohypophysis of the pituitary does not have a portal system
what does oxytocin do?
stimulates uterine contractions
What do ADH (anti-diuretic hormone) or Vasopressin do?
stimulates vasoconstriction and promotes fluid reabsorption by the kidneys; constricts vessels to raise blood pressure (arterioles)
where are oxytocine, ADH and vasopressin synthesised and release?
synthesised in the hypothalamus but released into the bloodstream in the pars nervosa
the hypothalamic - hypophysial tract secretes two neurohormones, what are they and how are they transported/stored?
oxytocin and ADH
they are placed in vesicles and transported + stored in terminals
each terminal stores either vasopressin or oxytocin
how are oxytocin and ADH released into the capillary bed?
they are conveyed along axons and released into neurohypophyseal capillary bed
What happens in the hypophysial portal system? 1st stage
1 - Neurohormones from the hypothalamus are released to the Hypothalamic-pituitary portal system
What happens in the hypophysial portal system? 2nd stage
Neurohormones bind to receptors on endocrine cells
What happens in the hypophysial portal system? 3rd stage
Regulate their hormonal secretion (releasing or inhibiting)
What is the hypophysial portal system?
blood vessels in the brain that connects the hypothalamus with the adenohypophysis
Where does the hypophysial portal system begin?
at the base of the hypothalamus
what happens to the arterial blood reaching the hypothalamus from the hypophysial portal system?
it branches to capillaries
What happens in the hypophysial portal system after the arterial blood reaching the hypothalamus branches to capillaries?
here, the venous blood joins and makes the small portal vein that passes through, stalk into the adenohypophysis
What happens in the hypophysial portal system after the portal vein stalks into the adenohypophysis?
here, they branch to anterior capillaries which in turn drain into the venous system
what are tropic hormones produced by - (the ones secreted by the pituitary gland)?
they are produced by neurosecretory cells in the several hypothalamic nuclei
what are most tropic hormones produced and secreted by?
by the ANTERIOR pituitary gland
Name two of the hormones produced by adenohypophysis?
GH - growth hormone
FSH - follicle stimulating hormone
haematology appearance of pars nervosa?
the pinkest - with some purple dots
haematology appearance of Rathke’s pouch?
white line
nuclei of the hypothalamus?
neuron cell bodies clustered in the hypothalamus
where does the nuclei of the hypothalamus send axons to?
to the neurohypophysis
central gliocytes?
support cells
central gliocytes aka?
pituicytes-neuroglial cells
oxytocin and ADH =
vasopressin
herring bodies?
secretory vesicles along the axons
neurohypophysis has no?
no neuron cell bodies
describe the myelination of the axons of the hypothalamic neurons?
unmyelinated
components of the neurohypophysis?
median eminence
infundibular stalk
pars nervosa
what is the infundibular stalk?
nerve tract
where is the median eminence?
base of the hypothalamus (this is a part of the neurohypophysis
what is the pars nervosa?
bulk of the neurohypophysis
what does the pars tuberalis part of the adenohypophysis do?
provides scaffold for the capillary network of the hypophyseal portal system
what is the pars intermedia?
a thin zone of basophilic cells
what is the primary function of the pars intermedia?
it is colour change regulation
- via melanotrophs ( a-melanocyte stimulating hormone) [a-MSH]
what three cells are found within pars distalis?
acidophils, basophils and chromophobes
what cells are classed as basophils in the pars distalis of the adenohypophysis?
Thyrotrophs
Gonadotrophs
Corticotrophs
What hormone does a thyrotroph secrete?
thyroid stimulating hormone (TSH)
What hormones does a Gonadotroph secrete?
Follicle stimulating hormone (FSH)
Luteinizing hormone (LH)
What hormone does a Corticotroph secrete?
Adrenocorticotropic hormone (ACTH)
what cells are classed as acidophils in the pars distalis of the adenohypophysis?
somatotrophs
lactotrophs
what hormones does a somatotroph secrete?
growth hormone (GH)
somatotropin
what hormone does a lactotroph secrete?
prolactin (PRL)
meaning of rudimentary?
undeveloped
Describe the presence of pars intermedia (of the adenohypophysis) in humans and birds?
rudimentary in humans and lacking in birds
What parts make up the adenohypophysis?
3 parts
Pars distalis
Pars intermedia
Pars tuberalis
which part of the adenohypophysis forms the stalk?
the pars tuberalis
How many sections make up the pituitary gland?
5
What sections make up the pituitary gland?
Adenohypophysis
Pars intermedia
Neurohypophysis
Hypophysial stalk
Recess of third ventricle
How many parts make up the pituitary gland median section?
3
What are the parts that make up the pituitary gland median section?
Adenohypophysis
Pars intermedia
Neurohypophysis
Which is the anterior lobe of the pituitary gland and which is the posterior lobe of the pituitary gland?
Anterior lobe: adenohypophysis
Posterior lobe: Neurohypophysis
What is the neurohypophysis?
it is he bulging of the diencephalon floor resulting in the outgrowth of the brain
it consists on nervous tissue from the hypothalamus
Where is the neurohypophysis derived from?
neural ectoderm
where is the adenohypophysis derived from?
oral ectoderm
What is the adenohypophysis?
an outgrowth of the pharynx (root of mouth) and it is glandular (hence ‘adeno’)
What does the nuclei of the hypothalamus consist of?
clusters of neurons
what does the nuclei of the hypothalamus do?
it sends axons to the posterior pituitary
secretes releasing hormones to the anterior pituitary
and intergrades and regulates vital bodily functions
