ENDOCRINE TISSUES AND THEIR TARGET
ORGANS
We are going to study the structure
of the pituitary and of some reproductive organs affected by pituitary
hormones. We have already studied ovaries and testes, and we have seen
gametogenesis which is regulated by pituitary gonadotropins, so integrate that
knowledge with this exercise.
Materials: slides of pituitary,
vagina, uterus in various stages of hormone stimulation, prostate, mammary
glands, placenta
PITUITARY
Examine the slide of the pituitary. Notice that there are distinctly
different staining regions: The darkly staining anterior pituitary, or pars
distalis; the pars intermedia next to the cleft of Rathke's pouch; and the
posterior pituitary or pars nervosa.
Anterior pituitary: There are acidophilic cells which stain quite
darkly just in front of the cleft which is the remnant of Rathke's pouch from
which the anterior pituitary is derived. There are many blood vessels since
there is a portal system bringing blood directly from the hypothalamus to the
anterior pitutiary, with the releasing factors made in the hypothalamus. The
releasing factors will cause the anterior pituitary cells to secrete their
gonadotropins or other trophic hormones which will control release of hormones
by many other endocrine glands in the body (thyroid, pancreas, gonads, for
example.)
Intermediate pituitary: This tissue lies between the anterior and
posterior pituitary and makes a melanocyte stimulating hormone in some animals.
Posterior pituitary: Made from the infundibulum of the forebrain
(diencephalon), and containing many nerve fibers since this tissue will release
hormones at this region made in the hypothalamus, but stored in the cells here,
much as neurotranmitters are stored at the ends of nerves a long distance from
their cell body, and can be released due to stimulation. This is the region
where oxytocin and vasopressin are released.
UTERUS
Compare slides of different times of the menstrual cycle of normal
uterus (see the difference between the proliferative and secretory phases),
uterus from someone taking the pill, pregnant uterus regarding the following:
a. the thickness of the wall (you have a pie shaped sector cut from one
side of the uterus on each slide, and the whole thickness of the wall is
there.) Measure the thickness with a ruler. Prepare a table comparing the
thicknesses.
b. the amount of glandular tissue (lots of deep grooves in the surface
of the endometrium).
c. the relative amount of endometrium and myometrium. The
myometrium has many muscle layers.
VAGINA
Find the lumenal side. Count the layers of cells in the lumenal
epithelium (there may be 20-40 layers.) What kinds of muscle can you see?
There should be layers of both smooth and striated muscle, since there are both
voluntary and involuntary contractions of the vagina.
Compare the epithelium with the epithelium of the cervex and uterus.
Notice how the cervex transitions between the vagina and uterus.
MAMMARY GLAND
Compare the ducts and glandular tissue in normal and lactating gland.
How can you tell the difference?
PLACENTA
Examine the preparation of the PIG fetus with fetal membranes: measure
the length of the whole placenta. Can you see the folds on its surface which
interdigitate with folds of the uterus)? There are no villi on pig chorion
which correspond to those on the disc of the human placenta. The connection
with the mother is much less intimate, so there is little bleeding at birth of
pigs. In order to see these folds, use the dissection microscope. Examine the
fetal pig in the jar which has an injected placenta, with arteries in red and
veins in blue. Compare it to placentas of sheep, cat, other mammals shown
mounted in jars and to the human placentas we have seen. Next, cut open the fetal membranes (the
chorion vesicle is outermost) carefully so you can keep them, BEING CAREFUL NOT
TO CUT A SECOND MEMBRANE INSIDE, then examine the connection of the umbilical
cord with the membranes and see if you can tell the difference between the
allantois, (which is fused with the chorion and is used to store urine in
pig development, and to bring the circulation to the uterine lining to get
oxygen and release wastes) and the amnion, which contains the fluid
which protects the embryo from drying and mechanical injury, and the outer chorion, and yolk sac.
Look at the slide of human placenta villi. The round or
irregularly shaped structures are sections of the villi. Each villus
after the fourth month has:
1. a blood vessel in it which will probably contain blood
cells.
2. Around the blood vessel is connective tissue which contains a
few cells and a lot of extracellular material which is fibers and matrix
material.
3. Around the connective tissue is the syncytiotrophoblast
(syntrophoblast) which separates the mother's blood from the rest of the
villus, since the mother's blood is in the
4. intervillous space or lacuna between the villi.
MAKE DRAWINGS LABELING THESE
STRUCTURES.
NAME__________________________
ENDOCRINE AND PLACENTA
1. The difference in vagina as compared to uterus is, vagina:
a. has a thicker wall
b. has more glands
c. has striated muscle
d. has a more stratified (layered) epithelium
e. more than one of the above
3. The part of the uterus which is shed during menstruation and after birth is the:
a. entire endometrium
b. myometrium
c. outer layer of endometrium (the stratum functionalis), down to basal layer
d. connective tissue
e. basalis blood vessels
4. A lactating mammary gland can be distinguished from a non-secretory one by:
a. the amount of connective tissue
b. the number of fat cells
c. the size of the alveoli and ducts
d. the amount of hormone the mammary gland produces
5. The pars distalis or anterior pituitary has compared to the pars nervosa or posterior pituitary:
a. more different kinds of cells staining uniquely
b. fewer cell types since fewer hormones are released from it
c. more neurons entering it from the hypothalamus
d. fewer capillaries
15. The placental villi contain blood vessels containing:
a. fetal blood
b. maternal blood
16. The chorionic villi are bathed on the outside in the intervillus sinusoids or lacuna by blood from:
a. the embryo
b. uterine arterioles
SHORT ANSWER
1. What is the difference in the uterine wall in the first and last half of the menstrual cycle?
2. What is the difference in the uterine wall in the first half of the menstrual cycle with and without the pill?
3.How can you tell the lumenal side of the vagina?