Download Hypophyseal portal system

Endocrine system
Thyroid, Parathyroid, Adrenal
Thyroid
Location: In the neck anterior to the larynx (thyroid cartilage)
It has 2 lobes connected by isthmus.
It produces 3 essential hormones:
 Thyroxin T4. tetra iodothyronine
 T3 triiodotyronine T3
T4 90% > T3
T3 90% more potent
T4 & T3 are regulate
metabolism of every cells.
 Calcitonin: aid in regulation of blood calcium and storage
of (ca) on bones.
Function ..?
The structure of thyroid
Stroma
It has thin fibrous capsule project into embedded thin trabeculae and
partition it into poorly defined lobules. C.T septa
The structural and secretory units of the thyroid is the follicle.
There are thousand of follicles of different diameters.
The follicle consists of single layer of epithelial cells (follicular
epithelium) which completely enclose a central lumen.
The epithelial cell vary in high from low cuboidal to columnar
state.
active
The epithelial cells rest on a typical basal lamina.
The lumen is filled with colloid which is strong acidophilic composed of
stored hormone thyroglobulin, it is inactive.
The follicles are surrounded by extensive network of fenestrated
capillaries and vasomotor nerves.
Two basic cells are present in the follicles
The principal or follicular cells and the Para follicular or C- cells.
Follicular cells secret T3 + T4 – endodermal in origin.
Parafollicular cells
secret calcitonin (hypocalcimic factor) –
ectodermal in origin.
Neural crest account 0.1% of the epithelium
Stimulated when calcium Ca++ are present resorption of bone.
The follicular cells = are cuboidal or columnar contain one or more
prominent nuclei and usually basophilic cytoplasm (pseudopodia).
EM
It has the character of secretory and absorptive cells. The apical surface
posses short microvilli RER in the basal region, well developed Golgi
apparatuse, mitochondria, lysosome and membrane limited vesicles
called colloidal resorption droplets in the apical region
C cells or para follicular cells
 Small in population, account for 0.1% larger in size of all
population.
 C cells referred to clear cytoplasm in some species and can be seen
nuclear LM
They are two to three times larger than follicular cells.
 In human is difficult to identify except with immunohistochemis
methods for calcitonin
The C cells are found in between the follicular cell or single cells or in
clusters and rest on the basal surface, its apical surface doesn’t reach the
luminal surface. Or in the interfollicular space as small clusters.
EM
They contain electron – dense (numerous membranes bound granules that
contain calcitonin.
They usually concentrated in the central region of both lobes of thyroid.
Function
TSH stimulates synthesis + release of thyroxin by:
(1) Increase uptake of iodide
(2) Synthesis of thyroglobulin.
(3) Iodination of thyroglobuline.
(4) Increase Phagocytosis of thyroglobulin – containing colloid
(5) Secretion of thyroxin in blood
negative feedback to support
TSH.
 Influence of TSH is reflected by hypertrophy of follicular cell
decrease hormonal colloid.
 At the apical part of the cell colloid is absorbed into the cell by
process of phagocytosis
phagosome
fuse with smaller
electron dense vesicle (1ry lysosome).
Lysosomal proteases split iodized throglobulin into T3 > T4
base of the cell they gain access to perifollicular capillaries.
Beginning
a.a (blood cap.)
Iodide
TSH structural
RER
oxidation
GA
Thyroglobulin.
lumen+ iodide thyroglobulin
hypertrophy + hyperplasia of follicle cell
follicles
In adenoma they are insensitive to TSH regulation
Hypothyroidism in adult + cretinism in children
Hyperthyroidism
at the
goiter
Blue Histology (School of Anatomy and Human Biology - The University of Western
Australia)
The parathyroid
 Found within the capsule of thyroid about 4 in number (tiny
gland) ovoid few millimeters in diameter.
 On each of superior and inferior pole location + number varies.
Develop from 3rd + 4th pharyngeal pouch.
The parathyroid possess a thin capsule of their own that send
trabecule and divide the gland into incomplete lobules. Most of the
blood vessels enter the gland through these trabeculae.
The parenchyma formed of cells arrange in irregular anastomosing
cords or groups. Supported by reticular fibers.
Two types of parynchymal cells present:
I. A major population of principal or chief cell numbers.
 Small polygonal cells D (5 – 8Um)
 With uniform central located nucleus.
 Pale – staining, acidophilic cytoplasm.
+ argyrophilic few mitochondria.
EM = reveal membrane – bound granules.
Secretory granules – (small electron dense).
Secret PTH parathyroid hormone maintain blood calcium.
Mitochondria, golgi apparatus.
Glycogen and lipid droplets (lipofuscin pigment)
Two types of chief cells: depend on the state of secretion.
1- One with fewer secretory granules and large glycogen droplets.
2- Predominant of secretory granules and much less of glycogen.
Osteoblast has receptor for PTH which stimulate to release osteoclast
stimulating factor
resorption
ca release to blood.
II. Oxyphil cells (6 –10 M)
 Small population.
 Are not known to have secretory function – unknown function
 Appear until somewhat between puberty and increase in
number with age.
 They are more rounded and considerable larger than principal
cells.
 They have strong acidophilic cytoplasm.
 The cytoplasm is voluminous, filled with mitochondria.
 The nuclei are central located and small with condensed
chromatin.
Glycogen
No secretory granules.
They are found singly or in clusters
Chief cells
then actively 10 times of normal when ca
In Rickets + Vit.D deficiency the principal cell hypertrophy to
recover normal calcium level
2ry hyperparathyroidism
If they is hyperplasia of principal cell
lead to increase ca level.
production of PTH and
It is called primary hyperparathyroidism which occur due to being
tumer of parathyroid lead
hypercalcemia ca+
phosphate + kidney stone.
Loss of bone mineral
kidney stones
Hyperparathyroidism
ca, tingling.
Cardopedal spasm (muscle cramps
muscle tetany especially
facial + laryngeal
fetal (tremors). Mental confusion
Memory lost
Treatment
oral ca, vit D, (emergency) calcium gluconate
Blue Histology (School of Anatomy and Human Biology - The University of Western
Australia)
THE ADRENAL GLAND
Secretes steroid hormones and catecholamine
Site: Supra renal, triangular in shape, embedded in the perirenal fat.
CAPSULE
The gland covered with thick connective tissue capsule, from which
trabeculae extend into the parenchyma carrying blood vessels + nerves
Reticular fibers extended between the cells + sinusoidal.
PARENCHYMA
The secretory parynchymal tissue is organize into cortical and medulary
region
The adrenal cortex is the steroid secreting portion. It lies beneath the
capsule and constitutes nearly 90% of the gland
It arise from caelomic mesodermal epithelium
THE ADRENAL MEDULLA
Is the catecholamine secreting portion, it lies deep to the cortex and
form the center of the gland. It is ectodermal in origin.
THE ZONATION OF ADRENAL CORTEX
AT BIRTH 2 ZONES
CORTEX
Medulla
Shortly the adrenal cortex is divided into three zones on the basis of the
arrangement of its parenchymal cells.
1. Zona glomerulosa
Narrow outer zone that constitute 15% of the cortical volume.
Mineralocorticoids (aldosteron + deoxycorticose)
2. Zona fasciculate
The thick middle zone that constitutes 80% of the cortical volum.
3. Zona reticularis
The inner zone constitute 5 – 7 % of the cortical volume.
Fascicularis and reticularis
secret glucocorticoids and androgens.
BLOOD SUPPLY
The adrenal supplied by superior, middle and inferior adrenal arteries.
In the gland the distribution will be as follow:
From 3vessels
superior
Middle suprarenal
Inferior
1- Capsular or sub capsular capillaries (plexus)
2- The sub capsular plexus give rise to straight cortical capillaries,
they separate the cellular cords of the zona fasciculate and drain
into capillaries in the zona reticularies, ultimately they will drain
into medullary sinuses
which drain into large venous
Sinuses
which empty into the central vein or adrenal vein.
3- Medullary arterioles – long cortical arteries, penetrate the cortex
traveling within the trabeculae and bring arterial blood directly to
medullary sinuses.
The medulla thus having dual blood supply the cortical capillaries +
medullary arterioles
The cortical capillary and medullary sinuses are all fenestrated.
I. ZONA GLOMERULOSA CELLS
Formed of arched or curved columns of cells that are continuous with
underlying cellular cords of zona fasciculate.
The cells are small columnar or pyramidal
These clusters of cells are surrounded by a rich network of fenestrated
sinusoidal capillaries.
The cells have spherical nuclei closely packed together (vaculated)
and deeply stained nuclei, acidophilic cytoplasm.
EM
Abundant sER, few rER, ribosomes, multiple golgi complexes, large
mitochondria with tubular cristae
Lipid droplets are sparse.
They secret mineralocorticoids
aldosterone, salt water retention
The aldosterone is regulated by angiotensine II which produce by
Stimulate rennin when they blood pressure.
II. ZONA FASCICULATA
 The cells here are larger and polyhedral, they are called
spongiocytes (vacuolated cytoplasm).
 They arranged in longer straight cords, one or two cell thick, that
are separated by straight cortical capillaries.
 They have highly stained spherical nucleus.
 Generally acidophilic (faint) cytoplasm (most vacuolated).
 There is abundant lipid droplets that usually dissolve during
preparation and the cell appear vacuolated.
NB
Lipid droplets contain, fatty acids, cholesterol phospholipids which are
precursors of steroid hormone
EM
Abundant sER, well developed, golgi complexes, mitochondria with
tubular cristae, few rER all characteristic of cells producing steroids.
They secret glucocorticoids regulating protein + CHO metabolism
The most important glucocorticoids
cortisol (catabolic effects)
Also they depress immune (by AB formation + lymphocyte
production) + anti-inflammatory retard tissue growth.
Secret small amount of androgen.
The cells of zona fasciculate is under feedback control of ACTH
III. ZONA RETICULARIS
 Their nuclei are deeply stained polyhedral (group of cells) shape
dark stained acidophilic.
 They arranged in cords which branch and anastomose in a reticular
manner, separated by fenestrated capillaries.
 They have relatively few lipid droplets.
 They present feature of steroid secreting cells mainly secret
Androgen and to lesser extent cortisol
secretion may lead to
mascularizing effect on developing genetalia.
1ry adrenocortical insufficiency (Addisons)
zones are atrophied.
ACT
all three
2ry Adrenocortical insufficiency :
reduce of ACTH.
Cushiong syndrom
adrenal hyperplasia or hyperedism of ACTH
( ACTH
ca )
ADRENAL MEDULLA
It consists of irregularly, large pale staining epitheloid cells called
chromaffin cells. They arranged in ovoid because they react with
chromate sales to produce
brownish colour
Clusters and short interconnecting cords.
its stroma is a highly vascular C.T.
By EM:
The cells have membrane – bound granules containing catecholamine
The nor-epinephrine granules are more electron-dense are autoflourscent
and stain well in siner + iodine Argentaffin (+)
In human about 80% of adrenal medulla secret epinephrine
EPINEPHRINE
Granules, cells elect.
Not autoflourscent
Stain iodine + silver
NOR-EPINEPHRINE
Autoflourscent strong
Stain with silver + iodine
argentafin +
By immune histochemistry the epinephrine cell are not autoflourescent.
And stain weakly with silver + iodine
Nor-epinephrine cell are autofluorescent and stain well with silver +
iodine
argentaffin +
Glucocorticoids + stress stimulate increase secretion of catecholamine
Medullablastoma
Secretion of catecholamine lead to general systemic response which
called fight or flight
Response HR, BP, RR. dilatation of bronchi
tremors,
sweating – closure of sphincter
Lipolysis, fat cell – glycogenolysis.
Blood sugar
Diabetes.
Blue Histology (School of Anatomy and Human Biology - The University of Western
Australia)
THE HYPOPHYSIS = PITUITARY GLAND
 It is the master gland although, it is regulated by hypothalamus
hormonal regulation
 It is pea-shaped gland 0.5 gm in ♀ and slightly more in ♀.
 Located in the base of the skull in a depression of the sphenoid
bone called sella turcica.
 There is a short stalk connecting the hypothalamus to the pituitary
called infundibulum.
 The hypophysis has two functional as well as histological
components.
1- Adenohypophysis (ant. Pituitary), the glandular epithelium
that derived from oral ectoderm. ( as dorsal autpocket of
Rathke’s pouch (primitive oral cavity)
Blood supply = derived from two set of vessels.
1- Superior hypophyseal arteries: supply the pars tuberalis, median
eminence and infundibular stem.
2- Inferior hypophyseal arteries: primarily supply the parsa nervosaVenous drainage carried to dural sinuses (mainly cavernous sinus)
HYPOPHYSEAL PORTAL SYSTEM
These vessels connecting the capillary bed in the median eminence and
pars tuberalis with a sinus oidal capillary plexuses in pars distals
This system of vessels carrier inhibiting factors (releasing factors)
neuroendocrine secretion of hypothalamus nerves from their sites
Release in the median eminence ca..? (stored secretion of hypothalamous)
and infundibular stem directly to the cells in pars distalis
There is feed back mechanism from primitive hypothalamus (devise
releasing factor of hypoth. TRH
CRW
SRH
GnRH (LH & SH)
PRH
RIF
PARS DISTALIS =
It is formed of small irregular groups of cells supported by reticular fibers
and separated by blood sinusoids
Three types of cells are recognized based on the staining properteria of
their secretory granules. Acidophils, basophils and chromophobes
(A) Acidophilis (40%)
Stained bright red with H & E giving the cytoplasm a distinct granular
appearance
There are two cell types: according to secretory granules:
1- Somatotropes
Growth hormone
EM: Small rounded and regular granules numerous.
2- Mammotropes
prolactin,
EM: large + irregular granules during lactation.
They are smaller than basophils but larger than chromobones.
GH before puberty
GH after puberty
GH
Gigantism
Acromegaly
dwarfism
Prolactin (estrogen & progesterone)
infertility + amenorhea
(B) Basophils 10% = they stain better with periodic acid – shift (stain
blue)
1- Thyrotrophs
TSH
Specific granules
small in size
2- Corticotropes, other naw Adenocorticolipotropes (
ACTH +
lipotropes LPH)
ACTH
They have the few, smallest size granules
Also some cells by histochemistry secret endrophin MSH + lipotropic
hormone LPH.
3- Gonadotrophers
variable size granules
Cells produce:
- Leuteinizing hormone LH
- Follicle stimulating hormone FSH.
(C) Chromophobes : they are poorly stain with H & E that the
cytoplasm appears virtually translucent, making them easily identifiable.
They are degranulated as a result of their releasing to their hormone could
be
acidophilic or
basophil
that are degranulated
PARS INTERMEDIA
It is rudimentary in human and appears as diffuse regions with slight
basophilic cells that may produce Melatonin stimulating hormone (MSH).
In fish + Amphibian, it is well developed
This area could surround small cystic cavities represent remnants of
Rathke’s pouch.
NB
It is found that in human MSH + ACTH can be release from one cell
type, so in Addison disease
pigmentation of skin.
Also they found that cells of pars intermedia could produce:
 endorphius
endogenous pain killer
Lipotropin
hormone regulating for metabolism.

PARS TUBERALIS
Highly vascular region containing vein of the hypophyseal portal vein
Small population of function of gonadotropes may present.
Neurohypophysis = Pars Nervosa = post. pituitary
It is consisting of pars nervosa + infundibulum that connect it to
hypothalamus.
The pars nervosa is primarily consist of a dense bundle of unmyelinated
nerve fibers (axons) terminal, these axons originate from the cell bodies
located in the hypothalamus
This tract of nerve is called = hypothalamic – hypophyseal tract.
The cell bodies of these neurons liea either in the supraoptic or
paraventricular nuclei of the hypothalamous.
These neurons are unique in two respects:
(1) They don’t terminate on other neurons or target cells, but end in the
proximity of fenestrated capillaries of pars nervosa.
(2) They contain secretory granules in all parts of the cells i.e cell body,
axon, axon terminals
ADH (Antidiuretic hormone) (vasopressin)
released from the
supraoptic nucleus to the axon in pars nervosa
Oxytosin is synthesized predominantly by nerve cell bodies forming the
paraventricular nucleus.
Within the pars nervosa, individual axons are separated from one another
by pituicytes.
Similar to glial cells in CNS.
Pituicytes has no clear function.
Therefor the unmeylinated axon stain poor with H & E but the clear thing
in the section is the nuclei of the pituicytes (oval or round nuclei)
irregular in shape with many branches.
EM
The axon terminals contain membrane- bound secretory granules
containing either ADH or oxytosin. They are octapeptides protein that
differ only in 2 amino-acids
Dilated portion of axon terminals that contain aggregation secretory
granules and can be visible by LM and stained with chrome alum
haematoxylin as blue-black structure called Herring bodies.
Neurosecretory granules are released into perivascular space by
exocytosis. The only structure interposed between the fenestrated
endothelium and the axon terminal are their basal lamina + reticular
fibers.
ADH
conc. Of urine
Diabetes insipidus.
Oxytosin production initiated by suckling reflex
Syntosinon.
Oxytosin
initiate labour.
uterine contraction
The pineal gland = pineal body
120 mg.
 It is a neuroendocrine gland.
It is a dorsal outgrowth of the diencephalons attached by a short
stalk to the third ventricle.
The gland is covered by pia matter forming a capsule from which
C.T trabeculae extend into the parenchyma forming irregular
lobules.
Its secretion are influenced by light and dark periods of day
The pinealocyte: it is the parenchymal cell + intestinal cells.
 Arrange into irregular cords and follicles.
 They have large nuclei that irregularly folded into various
configurations.
Slightly basophilic cytoplasm
They have cytoplasmic processes which are slightly basophilic but
difficult to see in LM.
 These cytoplasmic processes extend to the C.T trabeculae where
they terminate as bulbous expansions near the blood vessels,
organelles, sER. RER, GA, ribosomes, small secretory vesicles.
Microtubules well developed, microfilaments.
 In between these cells there are intercellular areas of calcified
organic matrix concentrically organized into oval elements are
common.
These opaque concentrations are called brain sand or corpora arenacea.
They are derived from precipitation (concretion) of calcium, phosphate
and carbonate on carrier protein that are released into the cytoplasm when
pineal secretion are released by exocytosis.
They found in childhood and increase with age.
They are easily located in x – rays of the skull because pineal is a midline
structure help in identification of space – occupying lesion
 A small population of a second parenchymal cell called interstitial
cell, represent only about 5% of the total cell number.
 They have more elongate nuclei deeply stained and condensed
chromatin in comparison to pinealocytes
Pineal function: reading
Melatonon influence reproductive activity
It is innervated by sympathetic nerve from superior cervical ganglion
deinnervation
change in physiological activity
If this injured
alternation in biologic activity
Norepinephrin
control melatonin
Secret melatonin, other substance.
Fluctuation in releasing factor such as ACTH R.F extend indirectly by
Melatonin
Melatonin
stops O2 control sexual activity through hypothalamus
Decrease melatonin
preconscious puberty
Blue Histology (School of Anatomy and Human Biology - The University of Western
Australia)