Endocrine System

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Endocrine System
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Thyroid Gland Fibro-elastic capsule delicate
septa trabeculae Septa mark off
lobules Lobules not completely separated Stroma
areolar reticular C.T. highly vascular
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Thyroid Gland Follicle closed, single-layered
epithelial sac (50 500 µ dia.) Size dependent
on amount of stored secretion 20 million
follicles in thyroid gland Generally spherical,
other shaped occur Epithelium simple cuboidal
(cell height uniform) Cytoplasm finely
granular basophilic (pale) Free border
microvilli Organelles polarized Terminal
bars at cell margins Mesh of reticular fibers
under epithelium (basement membrane)
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Colloid fills follicle Rich in nucleoproteins Cont
ains thryoglobulin enzymes
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Blood vessels lymphatics intimate plexuses
around follicles Arterio-venus anatomoses
common Thyroxin in veins lymphatics (most in
veins) Nerve fibers most are vasomotor A few
end in association with follicle cells (secretory)
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Parathyroid Humans 4 brownish glands 2 attached
to back of each thyroid lobe Accessory glands
occur in 30 of people Glands are ovoid Size of
an apple seed
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Framework Delicate fibro-elastic capsule Septa
divide each gland incompletely (lobules) Invasion
of septa begins after birth continues with
age Basketwork of reticular fibers supports cell
groups
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Parenchyma Epithelium secondarily lost surface
(from pharyngeal lining Masses cords of cells
each cell may back up on a capillary 2
primary cell types Chief cell oxyphil
cell Chief cells most common in masses cords
Clear chief cells (cytoplasm clear but rich in
glycogen Dark chief cells (smaller nuclei finely
granular cytoplasm) Oxyphil cells in small
groups abundant, deeply acidophilic cytoplasm
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Blood supply fairly rich larger vessels follow
septa Broad, irregular capillaries channel
parenchyma Lymphatics (?) Nerve fibers vasomotor
(few)
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Hypophysis Pituitary Gland Compound gland 2
parts from different embryonic sources Epithelial
part pouch pinched off from roof of
mouth Neural part from downgrowth brain floor
(diencephalon)
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Size small, flattened grape Framework Fibro-elas
tic capsule innermost part of dura
mater Thickest over anterior lobe Trabeculae
with blood vessels radiate from one region of
anterior lobe Meshwork of reticular tissue
supports epithelial cords sinusoids
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Pars Distalis (Posterior Lobe) Parenchyma
anastomosing cords of epithelial
cells Chromophobe cells smaller than chromophil
cells may be inactive form Chromophil cells
Cytoplasm granular more distinct than
chromophobe cells 2 types of chromophil cells
acidophil (alpha cells) basophil (beta
cells) Acidophils specific, spherical granules
of uniform size Basophils appreciably larger
fewer granules
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Pars Tuberalis Cell groups cords Cells finely
granular Cysts with colloid not uncommon in this
part Pars Intermedia Narrow, definite region but
ill defined in humans Cysts common filled with
colloid or hyaline material
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Neurohypophysis Distinct cell type
pituicyte Resemble neuroglia cells 4 subtypes
many contain fatty droplets, granules,
pigment Unmyelinated nerve fibers from the
hypothalamus majority end in pars nervosa
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Suprarenal Gland (Adrenal Gland) Flattened,
triangular cocked-hat (5 x 3 x 1 cm.) Cranial
pole of kidney Two very distinct regions Cortex
Medulla Cortex firm, yellow externally
reddish brown internally Medulla thinner,
softer, dark gray Different embryonic sources
become secondarily associated physically
functionally very different Framework Capsule
thick, fibro-elastic, inner zone looser more
vascular Slender trabeculae into cortex
reticular fibers sinusoidal vessels
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Suprarenal Gland (Adrenal Gland) Framework Capsu
le thick, fibro-elastic, inner zone looser
more vascular Slender trabeculae into cortex
reticular fibers sinusoidal vessels Medullary
reticulum coarser baskets around parenchymal
masses
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CORTEX
MEDULLA
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Suprarenal Cortex Radial, cellular cords long,
slender separated by trabeculae 2 cells
thick 3 layers in cortical parenchyma Zona
Glomerulosa Zona Fasciculata Zona Reticularis
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Zona Glomerulosa Thin layer Ovoid groups of
cells Groups U or J shaped Continuous with
zone below Cells columnar with deeply staining
nuclei Cytoplasm lightly basophilic with a few
lipid droplets Sinusoidal spaces
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Zona Fasciculata Middle layer thickest Parenchyma
long parallel columns usually 2 cell
wide Component cells irregularly cuboidal
larger than cells of Z. glomerulosa Nucleus
vesicular Cytoplasm basophilic outer
two-thirds cells have lipid droplets of
cholesterol, fatty acids, neutral fats inner
third cells more basophilic
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Zona Reticularis Parenchyma anastomosing cords
one cell wide Component cells much like Z.
fasciculata Fewer lipid droplets Near
medulla mixture of dark cells (deeper
staining) Cytoplasm large lipid droplets
at puberty add yellow-brown pigment
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Suprarenal Medulla Thin region in humans 5 to
10 of Suprarenal gland Points of triangle of
this gland, the medulla may fail C.T. and
blood vessels may be only elements in
points Medullary cells arranged in rounded groups
or short anastomosing cords Cells polyhedral
large vesicular nuclei cytoplasm specific
secretory granules ( varies) precursors of
epinephrine granules undergo chromaffin
reaction brown when treated with bichromate
solution
Medulla
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Medulla contains a few autonomic neurons
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Vascular supply extensive (more so than any
other organ/gland) Cortex from arterioles in
capsule empty into sinusoids sinusoids pass
toward medulla between cell columns sinusoids
lined with macrophages Medulla vascular
supply from 2 sources major source venous
blood from sinusoids sinusoids connect with
venules in medulla minor source arterioles
from capsule that pass directly to
medulla open to ordinary capillary plexus
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lymphatics in capsule near medullary
veins Nerve fibers unmyelinated nerves from
solar plexus enter capsule as small
bundles bundles follow trabeculae a few end
in cortex most end near medullary cells
preganglionic fibers medullary cells take
place of ganglionic cells stimulation of
splanchnic nerves ? heavy discharge of
epinephrine
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Pineal Body (Epiphysis) Stalked outgrowth of
diencephalon Encapsulated, lobulated organ (7 mm.
long) Internally densely packed cells
calcareous concretions often encountered Cap
sule supplied by dura mater septa vessels
pass inward lobules incomplete
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Parenchyma Epitheliod cells (pineal cells) form
cords long, branched processes processes with
bulbous ends Neuroglial cells (astrocytes
microglia)
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Pineal development Full development in middle
childhood Regressive changes follow onset
variable Stroma becomes fibrous increased
C.T. Acervuli increase largely in septa
capsule may be up to 1 mm. diameter lamellat
ed pimply or knobbed composed of calcium
/or magnesium carbonates phosphates The
Vertebrate third eye functional
photoreceptive organ in a few forms melatonin (?)
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Pancreas Islets of Langerhans These you
studied with the Digestive Glands.
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Corpus Luteum of the Ovary These you studird with
the Female Reproductive System. Placenta This
temporary endocrine gland studied with the Female
Reproductive System.
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Interstitial Cells of Leydig These you studied
with the Male Reproductive System.