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Lab #
I. Purpose:
Endocrine Gland Studies
Date
What is the function of the thyroid and adrenal glands?
CA Standard: (9c) Students know how feedback loops in the nervous and endocrine systems regulate
conditions in the body.
Background: Two systems regulate the body’s functions. These systems are the nervous system and the
endocrine system. The nervous system conducts impulses between the brain and spinal cord and the
body. The endocrine system secretes chemicals from glands into the bloodstream. Theses chemicals,
called hormones, carry messages to specific tissues or organs.
II. Materials:
microscope
prepared slide of thyroid gland
prepared slide of adrenal gland
III. Procedure:
Part A. Thyroid Gland
1. Observe a slide of the thyroid gland with the 10X objective of a microscope.
2. Note that the gland consists of a larger number of spherical sacs. These sacs are called follicles.
3. Switch to higher power and observe an individual follicle.
4. Observe the central material in the follicle. The thyroid gland secretes a material called a colloid
into the center of the follicle. The colloid is a stored form of thyroid hormone. The pituitary
gland secretes a hormone that signals the thyroid follicle cells to transport the colloid molecules
from the center of the follicle to the follicle cells as the colloid crosses the membranes of the
follicle cells, it is converted to thyroxine and then released into the bloodstream. Thyroxine
increases the rate of most metabolic functions in the body.
5. Compare the follicle you observed with that in Figure 1. Notice the location of the follicle cells
and the colloid.
6. Assuming you high-power field is 0.3 mm in diameter, estimate the diameter of each of 5 follicles.
Record the diameters in Table 1. Calculate the average diameter of a follicle.
7. Observe the cells between the thyroid follicles. These are interstitial cells. They secrete
calcitonin, which regulates the calcium level in the blood.
8. Find the interstitial cells in Figure 1.
Part B. Adrenal Gland
1. Hold up the adrenal gland slide. Note that there are two obvious layers of the adrenal gland. The
outer layer is called the cortex. The inner layer is the medulla. the gland is covered by a fibrous
connective tissue.
2. Locate the medulla under the 10X objective of your microscope. The medulla produces two
hormone, epinephrine and norepinephrine. They help the body adjust to sudden stresses. They
increase heart rate and the force of the heartbeat, and constrict blood vessels except those going to
muscles. This causes an increase in blood pressure. These hormones also cause the liver to
release stored sugar, which provides additional energy to the body under stress.
3. Observe the cortex of the adrenal gland with the 10X objective of your microscope.
4. The cortex is divided into three zones. Locate the innermost zone. This zone secretes small
amounts of sex hormones.
5. Locate the larger middle zone. This middle zone secretes glucocorticoids, a group of hormones
concerned with metabolism and stress resistance. The middle zone also secretes cortisol, which
increases carbohydrate, protein and lipid metabolism.
6. Locate the outer zone of the adrenal gland. This area secretes aldosterone, which increases
sodium and water retention by the kidneys.
7. In Figure 2, notice the cortex, medulla, sex hormone zone, glucocorticoid zone, aldosterone zone,
and fibrous connective-tissue covering.
IV. Data/Observations:
Table 1
Follicle
1
2
3
4
5
Average
Follicle Diameter
Diameter (mm)
V. Calculations/Results:
None
VI. Questions: (Re-state the questions and answer in a complete sentence.)
1. What is the function of the thyroid hormones?
2. What is the function of calcitonin?
3. Hyperthyroidism is a condition in which the thyroid secretes too much thyroid hormone. Predict
what would happen to the amount of colloid in the center of the follicle if a person had
hyperthyroidism. What would happen to the follicle cells?
4. Which part of Figure 3 shows the cells of a hyperthyroid follicle? Label it “hyperthyroid”
5. Hypothyroidism is a condition in which not enough thyroid hormone is produced. It can be caused
by an iodine deficiency. Iodine is necessary for the synthesis of the thyroid hormone. Without
iodine, the follicle cells shrink and become inactive. Identify the part of Figure 3 that shows the
cells of a hypothyroid follicle. Label it “hypothyroid”
6. What is the function of each of the following adrenal hormones?
a. Epinephrine:
b. Aldosterone:
7. Epinephrine is also known as adrenalin. How could it benefit someone bleeding from an injury?
8. How does epinephrine provide an adaptive advantage to an animal faced with danger?
VII. Conclusion:
Answer the purpose. Re-state and answer in a complete sentence.