http://www.meddean.luc.edu/lumen/meded/Histo/frames/h_fram19.html
Slide 27 – 31 Pancreas
Testes 1: Low power view of the testis at the mediastinal region where the duct system
leaves the organ.
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a = seminiferous tubules
b = rete testis in mediastinum
c = epididymis
d = efferent ducts Note the thick collagenous connective tissue capsule (the tunica
albuginea) surrounding the testis.
Testes 2: Higher power of rete testis, the narrow cavernous channels lying in the dense
connective tissue. You will notice a couple of thin-walled, blood-filled blood vessels also
coursing in the same region. Sperm produced in the seminiferous tubules leave the testis
by way of the rete, which ultimately converges on about twelve efferent ducts.
Testes 3: Detail of rete testis, showing cavernous, irregular channels lined with a low
epithelium.
Testes 4: Low power view of seminiferous tubules. These tubules are very long and
tightly coiled, so each one is cut many times in any given section of the testis. Blood
vessels and interstitial cells of Leydig lie in the connective tissue stroma between the
tubules.
Testes 5: Seminiferous tubules of the testis.
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a = spermatogonia
b = spermatocytes (probably primary because secondary spermatocytes go
through their cell division so quickly that they are seldom seen in sections). The
cells are largest at this stage.
e = spermatids
f = maturing sperm
d = interstitial cells of Leydig (endocrine cells which secrete androgens).
A small amount of smooth muscle around the tubule aids in moving differentiated sperm
along the tubule and into the rete testis.
Testes 6: Detail of wall of seminiferous tubule, showing stages of spermatogenesis. The
large, vertically oriented nucleus at the base on the left belongs to a Sertoli cell; notice
that sperm heads (somewhat out of focus) are clustered deep down near this nucleus. The
horizontally flattened nuclei along the base of the tubule belong to spermatogonia, the
continually multiplying, diploid germ cells. A few primary spermatocytes, with the dark,
condensed chromosomes undergoing prophase of meiotic division, lie just above the
spermatogonia. Above the spermatocytes are the round, relatively small, haploid
spermatids, which would occupy the rest of the layers up toward the lumen.
Testes 7: Drawing of stages in the differentiation of sperm directly from spermatids. This
process is called spermiogenesis.
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A = a still-rounded spermatid, with an acrosomal body beginning to form in the
region of the Golgi apparatus. At the opposite pole of the nucleus lie the
centrioles, one of which begins to spin out a long cilium (or flagellum).
B = an elongating spermatid, with an acrosomal cap now forming over the top of
the nucleus. The flagellum is longer and the centrioles are oriented perpendicular
to each other. The centriole related to the flagellum is comparable to the basal
body of ordinary cilia.
C = further development of the acrosomal cap and beginning pinching off of
excess cytoplasm, thanks to the formation of a filamentous manchette, nuclear
ring, and annulus.
D = further condensing of the nuclear chromosomal material and separating off of
the excess cytoplasm. Notice that the intercellular bridge connecting this
spermatid to its neighbor is still intact.
E = the cytoplasmic mitochondria have now collected along the proximal portion
of the flagellum and are thus conserved (for energy purposes) when the residual
cytoplasm is cast off. The flagellum has meanwhile developed a complex fibrous
sheath which surrounds a central core of microtubules arranged in the nine plus
two arrangement typical of cilia.
Testes 8: Wall of seminiferous tubule. Along the base can be seen small dark nuclei of
spermatogonia and large, pale, ovoid or triangular nuclei of Sertoli cells, each with a
prominent nucleolus. Sperm heads are imbedded in folds of Sertoli cell membrane, rather
deep within the tubule wall. Sperm tails are pointing toward the tubule lumen. Primary
spermatocytes have large nuclei with the condensed chromosomes in prophase, near the
base of the wall. The small, round nuclei toward the lumen belong to early spermatids.
Pale pink cytoplasmic cast-offs from differentiating spermatids (becoming sperm) lie
next to the lumen. Look again at the two Sertoli cells farthest to the left and notice how
their cytoplasm meets near the base to form the basal and adluminal compartments on
either side of the junction.
Testes 9: Efferent ducts with their irregular epithelial border. These are the only portions
of the male reproductive tract with motile cilia on the lining epithelium. Cilia help to
move the sperm along toward the epididymis.
Testes 10: Detail of efferent duct wall, a low pseudostratified columnar epithelium with
some surrounding smooth muscle. The epithelium is ciliated. Sperm lie in the lumen.
Testes 12: Epididymis with pseudostratified columnar epithelium with stereocilia.
(Stereocilia are structurally like microvilli rather than like true cilia. They do not move.)
Each cross-cut of tubule shows some surrounding smooth muscle cells. Notice how very
regular this epithelium is in height, making an unusually smooth apical line near the
lumen. This is characteristic of epididymis. Compare this with the "scalloped" edge of
efferent ducts in the previous slides.
Testes 13: Another view of epididymal wall, showing more clearly the basal and
columnar cells of the pseudostratified epithelium. The stereocilia are long and pale
(practically invisible here!). Circular smooth muscle in the outer wall is evident
Testes 14: Distended epididymis packed with maturing sperm. They are already mature
structurally but are only now acquiring the ability to move on their own.
Testes 15: Ductus deferens with its proportionally small lumen and heavy muscular coat.
The bulk of the smooth muscle is circular, but there is a thin inner longitudinal and a
somewhat thicker outer longitudinal layer.
Testes 16: Detail of epithelial lining of the ductus deferens. It is pseudostratified
columnar with non-motile stereocilia.
Ovary 1: Ovary with surface cuboidal epithelium. (Really a modified mesothelium.)
Ovary 2: Cortex of ovary. A thick connective tissue capsule, the tunica albuginea
underlies the surface epithelium. Somewhat deeper lie several small, primary (primordial)
follicles. (All egg cells have reached the primary oocyte stage by birth and are held in this
"suspended animation", in very early prophase, until such time as they may ovulate or
undergo atresia.)
Ovary 3: Primary follicles with one single layer of flat follicle cells surrounding an
oocyte. Although an oocyte is a giant compared with its neighbors, this early stage is
small for an oocyte, and the cell will grow considerably in size when it begins to mature,
under the influence of FSH. The nucleus looks lightly granular, and the dark nucleolus is
prominent. Cytoplasm is very pale. Note the "swirly" interstitial tissue of the ovarian
stroma.
Ovary 4: Early maturation stage of follicle with beginning proliferation of follicle cells
around an enlarging oocyte. The nucleolus shows clearly inside the nucleus. As the
oocyte enlarges, its chromosomes prepare further for the first meiotic division, which will
occur at ovulation.
Ovary 5: Further developed follicle
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a = with antrum beginning at arrows. The homogenous gray-blue line
immediately surrounding the egg cell itself is the zona pellucida.
b and c = primary follicles, containing oocytes which are still small.
Ovary 6: A group of follicles in various stages of early development in the cortex of a rat
ovary. Blood vessels of the ovarian medulla are seen in the center of the field.
Development of follicles is regulated by FSH from the anterior pituitary.
Ovary 7: Maturing follicle, so called because it contains a definite antrum (or fluid-filled
space) and many layers of granulosa cells. The egg is still a primary oocyte and sits to
one side of the follicle on a mound of cells called the egg hillock or cumulus oophorus.
The cells closest to the oocyte will be expelled with it at ovulation as the corona radiata.
Surrounding the granulosa cells of the follicle is the theca interna, a rather cellular and
vascular connective tissue layer, which secretes estrogen. Outside of this is the theca
externa a more fibrous connective tissue layer, not well defined here. Note that several
follicles may start to develop in any one monthly cycle, but in the human only one will
mature, unless there are to be multiple ovulations and therefore possible multiple births.
All follicles that don't complete their maturation undergo atresia (i.e., degenerate). The
egg dies, the granulosa layer breaks up, and the whole follicle collapses and undergoes
fibrotic change.
Ovary 8: Large ruptured follicle, just after ovulation.
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Arrow = stigma, the point of rupture where oocyte was expelled. The reduction
division (or first meiotic division) takes place at the time of ovulation.
a = granulosa cells that will now proliferate under the stimulus of pituitary LH
and enlarge to become granulosa lutein cells, filling in the follicular cavity and
becoming the major portion of the new corpus luteum.
b = corpus albicans -- old scar of an earlier corpus luteum.
Slide 1 Pituitary
Macro view of the pituitary gland. This and the following pituitary slides are stained with Masson's trichome wherein nuclei and other
basophilic structures (may include cytoplasm) are blue, collagen is green or blue, and cytoplasm (nonbasophilic) are red. Notice the lightlystained neurohypophysis and darker-stained adenohypophysis.
Slide 2 Pituitary
The anterior pituitary is to the upper right and the posterior pituitary is to the lower left. Small cystic spaces that mark the remnants of Rathke's
pouch separate the two.
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Slide 3 Pituitary
The small dark cells are a lymphocyte infiltrate into the intermediate lobe. There is a rich blood supply to the anterior lobe that supplies the
hypothalamic releasing and inhibiting factors that regulate pituitary hormone secretion.
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Slide 4 Anterior Pituitary
The anterior pituitary is composed of the stained-rich chromophils and the clear chromophobes. Of the chromophils, acidophils are red and
basophils are blue.
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Slide 5 Anterior Pituitary
Chromophobes (black arrow), Eosinophiles (red arrow), Basophiles (blue arrow).
Also visible in this area are collagen (blue) and the red (yes, red) cells in the vasculature.
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Slide 6 Posterior Pituitary
The majority of the space is occupied by axons descended from the hypothalamus. It is thus not a true endocrine gland, but a specialization of
the hypothalamus that maintains the blood brain barrier while still secreting hormones into the bloodstream by the axon endings.
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Slide 7 Posterior Pituitary
Herring bodies (arrow) are the dilated hypothalamic nerve terminals from the hypothalamus from which the posterior pituitary actually releases
ADH & Oxytocin. ADH and oxytocin are released from different Herring bodies reflecting their seperate cells of origin.
Bar = 50 mm
Slide 1 Thyroid
The simple cuboidal epithelium lining the follicles produces the thyroglobulin which is stored in the colloid follicles. Later it is taken back up
by these same cells, cleaved, and released as T3 & T4. Notice that the thyroid is the only gland to store its hormones extracellularly.
Slide 2 Thyroid
The C-cells secrete calcitonin which helps lower calcium levels. Recall that this hormone antagonizes the effect of PTH from the parathyroids.
These C-cells are actually named for being "clear" (as in lighter staining). Notice that they are in the interstitium and do not normally touch the
follicles.
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Slide 3 Thyroid
Thyroglobulin (in the follicles) is a glycoprotein. The PAS stain reacts with the carbohydrate components of thyroglobulin and produces a deep
red appearance.
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Slide 1 Parathyroid
Cells of the parathyroid are often mistaken for lymphocytes. An actual lymphocytic infiltrate (arrow) stains darker. Notice the parathyroid cells
are sometimes arranged in strings or lines.
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Slide 2 Parathyroid
The string-like arrangement of the parathyroid cells on the right. The large, clear cells to the left are oxyphil cells whose function is unknown.
They are found only in humans and increase with age. The intense eosinophelia in their cytoplasm reflects an abnormally high number of
mitochondria in these cells.
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Slide 1 Adrenal
Identify the three layer of the adrenal cortex from left to right: Zona Glomerulus, Zona Fasiculata, Zona Reticularis (mnemonic - GFR). Also
notice the dark medulla and the surrounding capsule.
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Slide 2 Adrenal
Find the layers again and notice the rich blood supply.
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Slide 2KU Pancreas
The pancreas, shown here stained with H&E, serves both endocrine and exocrine functions. The round islets of Langerhans are the endocrine
portion and serve to identify pancreatic tissue.
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Slide 3KU Pancreas
Islets are distinguished from the surrounding exocrine tissue by a continuous connective tissue capsule and an extensive microvascular that first
bathes the center of the islet that is rich in B or beta (insulin) cells, and then the periphery where most of the A or alpha (glucagon) cells are
located. Within the islet, the glucagon-secreting alpha cells stain red while the insulin-secreting beta cells stain blue. (Gomori Stain)
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Slide 1 Pineal
The pineal gland (in the brain) secretes melatonin, but its function in man is largely unknown. It is best identified by the distinctive dark
globules known as brain sand that can be observed in the glands of older individuals. There are two principal cell types in the pineal; the
pinealocyte that is a highly modified neuronal cell and that secretes melatonin, and glial cells.
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Slide 2 Pineal
This is the brain sand of the same person after a grueling semester of Physiology. Obviously this is a digitally manipulated image, but do
remember that this mineralization has no clinical manifestation.
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