🌚 Flashcards
What is the thyroid gland?
A bilobate endocrine gland located in the anterior neck region
How many lobes does the thyroid gland have?
Two large lateral lobes
What connects the two lobes of the thyroid gland?
An isthmus, a thin band of thyroid tissue
What are the approximate dimensions of each lobe of the thyroid gland?
- Length: ~5 cm
- Width: ~2.5 cm
- Weight: 20 to 30 g
Where are the lobes of the thyroid gland located?
On either side of the larynx and trachea
What surrounds the thyroid gland?
A thin loose connective tissue capsule
What do the septa/trabeculae from the capsule do?
Extend into the parenchyma of the gland dividing it into lobules
What do the septa convey into the gland?
- Blood vessels
- Lymphatics
- Nerves
What are the functional units of the thyroid gland?
Secretory/thyroid follicles
Describe the structure of a thyroid follicle.
Roughly spherical cyst-like compartment with a wall formed by simple cuboidal or low columnar epithelium
What does the follicular epithelium rest on?
A basement membrane
Fill in the blank: The thyroid gland consists of two large lateral lobes connected by an _______.
[isthmus]
True or False: The thyroid gland weighs between 10 to 20 grams.
False
What are the two types of cells that secrete epinephrine and norepinephrine in the adrenal medulla?
Epinephrine-secreting cells and norepinephrine-secreting cells
These cells are responsible for the production of catecholamines.
How do epinephrine-secreting cells appear under a transmission electron microscope?
They show smaller and less electron-dense granules, whose contents fill the granule
This indicates a difference in hormone storage between the two cell types.
What distinguishes norepinephrine-secreting cells when observed under a transmission electron microscope?
They have larger, more electron-dense granules with irregular content and an electron-lucent layer beneath the membrane
This structural difference affects the secretion and functionality of norepinephrine.
What percentage of the catecholamine output of the adrenal vein is epinephrine?
About 80%
This highlights the predominance of epinephrine in adrenal catecholamine secretion.
Do adrenal medullary cells store hormones, and how does this differ from the adrenal cortex?
Yes, they accumulate and store their hormones in granules; unlike the cortex, which does not store steroids
This storage mechanism is crucial for the rapid release of hormones during stress.
How are adrenal medullary cells innervated?
By cholinergic endings of preganglionic sympathetic neurons
This innervation is essential for the stimulation of catecholamine release.
What is the structure and function of pancreatic islets?
They are spherical or ovoid clusters of endocrine cells scattered in the connective tissue stroma between pancreatic exocrine acini
These islets play a vital role in regulating blood glucose levels.
What type of capillaries vascularize the pancreatic islets?
Sinusoidal capillaries
This vascularization is important for the efficient exchange of hormones into the bloodstream.
How do all of the endocrine cells in the pancreatic islets appear in routine light microscopy (LM) preparations?
They appear similar
This similarity necessitates the use of immunohistochemistry to differentiate cell types.
How many major cell types are indicated to exist among the endocrine cells in the pancreatic islets?
At least three major cell types
Additionally, there are three or more minor cell types.
What are the two types of cells that secrete epinephrine and norepinephrine in the adrenal medulla?
Epinephrine-secreting cells and norepinephrine-secreting cells
These cells are responsible for the production of catecholamines.
How do epinephrine-secreting cells appear under a transmission electron microscope?
They show smaller and less electron-dense granules, whose contents fill the granule
This indicates a difference in hormone storage between the two cell types.
What distinguishes norepinephrine-secreting cells when observed under a transmission electron microscope?
They have larger, more electron-dense granules with irregular content and an electron-lucent layer beneath the membrane
This structural difference affects the secretion and functionality of norepinephrine.
What percentage of the catecholamine output of the adrenal vein is epinephrine?
About 80%
This highlights the predominance of epinephrine in adrenal catecholamine secretion.
Do adrenal medullary cells store hormones, and how does this differ from the adrenal cortex?
Yes, they accumulate and store their hormones in granules; unlike the cortex, which does not store steroids
This storage mechanism is crucial for the rapid release of hormones during stress.
How are adrenal medullary cells innervated?
By cholinergic endings of preganglionic sympathetic neurons
This innervation is essential for the stimulation of catecholamine release.
What is the structure and function of pancreatic islets?
They are spherical or ovoid clusters of endocrine cells scattered in the connective tissue stroma between pancreatic exocrine acini
These islets play a vital role in regulating blood glucose levels.
What type of capillaries vascularize the pancreatic islets?
Sinusoidal capillaries
This vascularization is important for the efficient exchange of hormones into the bloodstream.
How do all of the endocrine cells in the pancreatic islets appear in routine light microscopy (LM) preparations?
They appear similar
This similarity necessitates the use of immunohistochemistry to differentiate cell types.
How many major cell types are indicated to exist among the endocrine cells in the pancreatic islets?
At least three major cell types
Additionally, there are three or more minor cell types.
