Histology of glands Flashcards
what are glands formed from
epithelial tissue
subdivisions of glands
endocrine
exocrine
endocrine glands
secrete hormones directly into the blood stream
thyroid gland
exocrine glands
release their substances either directly onto an epithelial surface e.g. goblet cell in the gut
OR via a system of ducts e.g. major salivary glands
how do glands develop
from a lining or covering epithelium by invagination into the underlying connective tissue
location of thyroid gland
anterior neck with right and left lobes
connected to an isthmus
cell arrangement thyroid glands
arranged into spherical structures called follicles
thyroid hormones are stored here
each follicle is lines with single layer of follicular cells which are cuboidal epithelium and surrounded by reticular fibers
vascular capillary netwrok surrounds the follicles for entrance of thyroid hormones into the bloodstream
follicles in thyroid gland
structural and function units of the gland
in active follicles the epithelium is cuboidal
less active follies the epithelialcellr appear flattened
all follicles are fixed with colloid
what divides the thyoird gland into lobules
connective tissue septa from the capsule of the thyroid gland
they extend into the glands interior and divide the gland
what is found between individual follicles in the thyroid gland
small amount of inter follicular connective tissue
what is in the image
thyroid gland
colloid in thyroid
is composed of thyroglobulin
it is inactive iodinated glycoprotein compound for storage of thyroid hormones
stain pink
by itself doesnt have any hormonal activity
parafollicular cells/ C cells in thyroid
pale staining
found peripherally in basal lamina of follicular epithelium or as clusters between follicular cells
secrete calcitonin
calcitonin function
inhibit bone resorption
lowers blood calcium levels
when necessary what do follicular cells do to stored thyroglobulin in thyroid
can take up the stored substance
transport it across the epithelium
release thyroid hormones into capillaries surrounding the follicle
what does thyroglobulin contain
modified tyrosine amino acids that constitute the thyroid hormones:
thyroxine (tetraiodothyronine,T4) and triiodothyronine T3
label the image
principal cells in thyroid
line the follicles
simple cuboidal epithelium
what is the pituitary gland controlled by
the hypothalamus of the brain
regulatory hormones are transported to the pituitary gland
embryonic origins of the pituitary
Adenohypophysis
neurohypophysis
clinical divisions of the pituitary gland
anterior lobe
posterior lobe
where is the pituitary gland located
what does the adenohypophysis contain
pars distils
pars tubercles
what does the neurohypophysis contain
pars intermedia pars nervosa
infundibulum/ pituitary stalk
where is the neurohypophysis derived from
down growth of nervous tissue from hypothalamus
it remains joined by the pituitary stalk
what is contained within the posterior pituitary/neurohypophysis
hypothalamohyphophyseal tract
consisting of axons from neurons whose cell bodies are located in the supraoptic and paraventricular nuclei of the hypothalamus
where does the anterior pituitary arise from
arises as an epithelial/ectodermal upgrowth from the roof of the primitive oral cavity known as Rathkes pouch
describe internal structure of Aden-hypophysis
may contain a cleft or group of cyst like spaces which represent the vestigial lumen of rattles pouch
dividing the major part of anterior pituitary form Thun zone of tissue against posterior pituitary known as pars intermedia
pars intermedia location
within the Aden-hypophysis but classified as posterior pituitary
pars distils
95%
forms anterior wall of rattles pouch
pars intermedia
forms posterior wall of rathkes pouch with pars nervosa of neurohypophysis
pars tuberalis
forms collar of cells around the infundibulum of the neurohypophysis
hormones secreted by posterior pituitary
antididiuretic hormone (aka vasopressin) and oxytocin
synthesises in the neurone cell bodies of supraoptic nucleus
what do ADH hormones act on
act directly on non-endocrine tissues
where is ADH specifically made
synthesises in the neurone cell bodies of supraoptic nucleus
where is oxytocin specifically made
paraventricular nucleus of the hypothalamus
how do ADH and oxytocin get to posterior pituitary
bound to glycoproteins
they pass down the axons of the hypothalamopituitary tract
through the pituitary stalk
to posterior pituitary where they are stored in distended terminal parts of axons
release of posterior pituitary hormones
controlled directly by nervous impulses passing down the axons from the hypothalamus
called neurosecretion
neurohypophysis
hypothalamic supraoptic and paraventricular nuclei consist of vasopressin and oxytocin synthesising hormones
send projections here
where in brain does the pituitary gland sit
in body depression in the sphenoid bone
called sella turcica
label the image
PP posterior pituitary
AP anterior pituitary
H hypothalamus
P pituitary stalk
V third ventricle
O optic chiasma
pars tuberalis
surrounds the infundibulum
infundibulum
connects hypothesis with hypothalamus at base of the brain
cell types within the pars distils
chromophobe cells, don’t take H&E
chromophil cells
chromophil cells
subdivided into acidophils (alpha cells)
and basophils (beta cells)
pars nervosa
consists primarily of unmyelinated axons and supporting pituicytes
what surrounds pars distils and pars nervosa
connective tissue capsule
what supplies the pars distils and pars nervosa
blood vessels and capillaries
label the image
what are all of the specific cell types in pituitary
somatotrope
mammotrope
thyrotrope
gondadotrope
andrenocorticotrope
cell types in pars distalis
somatotrope
mammotrope
thyrotrope
gondadotrope
andrenocorticotrope
pars tuberalis cell types
gonadotropes only
pars intermedia cell types
contain basophils
but secretions in humans are unclear
although ACTH secretion is possible