L28. Histology - Microanatomy of Endocrine Glands II

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Questions and Answers

Which of the following best describes the mechanism of action for steroid hormones?

They act through a second messenger system on the cell surface.

They are produced by enzymes in the smooth endoplasmic reticulum and mitochondria and require carrier proteins for blood transport. (correct)

They are released directly into the bloodstream and travel freely to target cells.

They are synthesized in the rough endoplasmic reticulum and stored in vesicles.

Which of the following is NOT a characteristic of peptide hormones?

They are packaged in the Golgi complex.

They are stored in secretory vesicles before release.

They are synthesized by the cooperative action of enzymes located in smooth endoplasmic reticulum and mitochondria (correct)

They are synthesized in the rough endoplasmic reticulum.

What is the primary difference between endocrine and paracrine signaling?

Endocrine signaling involves hormones binding to cell surface receptors, while paracrine signaling involves hormones entering the cell.

Endocrine signaling affects many different cell types, whereas paracrine signaling affects only a single cell type

Paracrine signaling involves rapid, short-term responses, while endocrine signaling results in long-term changes.

Endocrine hormones travel through the bloodstream to distant sites, while paracrine hormones act on neighboring cells via diffusion. (correct)

What describes an autocrine effect?

Hormones act on the same cells that produce them. Signup and view all the answers

Based on the organization presented, what is a key shared characteristic between the thyroid and parathyroid glands?

They have a defined section focused on cell types. Signup and view all the answers

According to the content, what do amino acid analogues and catecholamines have in common?

They are in the same class of hormone. Signup and view all the answers

Based on the information provided, the adrenal gland is similar to the thyroid and parathyroid in which aspect?

They all have the aspect of blood supply covered. Signup and view all the answers

In the adrenal gland, where do the thin-walled cortical capillaries, carrying hormone-rich but oxygen-poor blood, initially merge with oxygen-rich blood from medullary arterioles?

At the cortico-medullary junction. Signup and view all the answers

Which of the following is NOT a characteristic of the cells within the zona glomerulosa?

They have a basophilic staining pattern. Signup and view all the answers

Which of the following best describes the mechanism of action for protein hormones?

They interact with cell surface receptors, utilizing second messenger systems. Signup and view all the answers

What is the primary function of aldosterone, produced by the zona glomerulosa?

To increase sodium uptake in the kidney. Signup and view all the answers

How do steroid hormones typically exert their physiological effects?

By directly interacting with DNA, leading to the production of new proteins. Signup and view all the answers

Which of the following describes the order of zones in the adrenal gland cortex, from outermost to innermost?

Zona glomerulosa, zona fasciculata, zona reticularis Signup and view all the answers

Which characteristic is associated with endocrine glands?

They release their products into blood vessels via a dense plexus of fenestrated capillaries. Signup and view all the answers

How do the cells of the zona glomerulosa primarily obtain cholesterol, a precursor for steroid hormone synthesis?

By means of receptor-mediated uptake. Signup and view all the answers

The pineal gland develops as a dorsal extension from which part of the brain?

The posterior part of the roof of the diencephalon. Signup and view all the answers

What happens to the lumen of the pineal gland as it matures?

It becomes obliterated as the walls of the gland thicken. Signup and view all the answers

What is the connective tissue covering that surrounds the pineal gland?

The pia mater. Signup and view all the answers

How is the parenchyma of the pineal gland organized?

It is partitioned into clumps of cells, or lobules, by septae and trabeculae. Signup and view all the answers

What is the major cell type found within the pineal gland?

Pinealocytes. Signup and view all the answers

Which of the following is a distinct characteristic of pinealocytes?

They are relatively large cells with deeply creased nuclei. Signup and view all the answers

Which ratio accurately represents the production of T4 to T3 by the thyroid gland?

20:1 Signup and view all the answers

Where are T3 and T4 primarily transported within the body?

Serum carrier proteins Signup and view all the answers

What is the key function of T3 and T4 hormones regarding metabolic processes?

They regulate basal metabolism of carbohydrates, proteins, and fats. Signup and view all the answers

Which hormone directly controls all stages of T3 and T4 synthesis?

TSH Signup and view all the answers

How is the release of TRH regulated?

By negative feedback from T3 and T4 hormones. Signup and view all the answers

In which locations is T3 generated from T4?

Kidney, liver, and heart Signup and view all the answers

What is a distinctive characteristic of parafollicular cells in terms of staining?

They stain poorly with H&E. Signup and view all the answers

Where can parafollicular cells be found within the thyroid gland?

Within the wall of the follicle and in the interstitium Signup and view all the answers

What is the primary product secreted by parafollicular cells?

Calcitonin Signup and view all the answers

Which of the following best describes the characteristic spatial arrangement of secretory granules in parafollicular cells?

Located in close proximity to surrounding capillaries. Signup and view all the answers

Based on the provided information, what is the primary role of parathyroid hormone (PTH) when blood calcium levels are low?

To stimulate the release of calcium from bone by activating osteoclasts. Signup and view all the answers

Which of the following best describes the appearance and characteristics of oxyphil cells in the parathyroid gland?

Larger, acidophilic cells with many mitochondria and small nuclei. Signup and view all the answers

What is the functional relationship between calcitonin and parathyroid hormone (PTH) as described in the given content?

The action of PTH is opposite to that of calcitonin. Signup and view all the answers

How does PTH indirectly stimulate osteoclast activity?

By binding to osteoblasts, which then in turn drive the formation of activated osteoclasts. Signup and view all the answers

At what stage of life do oxyphil cells typically appear in the parathyroid gland, according to the text?

Around 4-7 years of age, increasing with age. Signup and view all the answers

What cellular components are characteristic of oxyphil cells, based on the description in the given information?

Numerous mitochondria, small nuclei, and an eosinophilic cytoplasm. Signup and view all the answers

Which cellular feature is identified within the chief cells of the parathyroid gland by the text?

Prominent nuclei Signup and view all the answers

What is the primary source of the secretory granules mentioned in the parathyroid gland cells?

Chief cells Signup and view all the answers

Besides bone, what other organ systems are targeted by Parathyroid Hormone (PTH) to help elevate blood calcium levels?

Kidney tubules and intestines Signup and view all the answers

According to the provided content, what is a characteristic of the fenestrated capillaries in the parathyroid gland?

They possess small pores or fenestrations that permit the exchange of molecules. Signup and view all the answers

Study Notes

Microanatomy of Endocrine Glands II

Pineal Gland (Epiphysis Cerebri):
- Located as a dorsal extension from the posterior part of the diencephalon's roof.
- Its lumen is obliterated as the walls thicken with age.
- It remains attached to the roof of the third ventricle.
- Covered by a capsule, extending into the gland as septae and trabeculae.
- Contains pinealocytes (95%) which are large cells with creased nuclei, prominent nucleoli, and long cytoplasmic processes.
- Contains glial cells (5%) which have long cytoplasmic processes forming a supporting network with blood capillaries.
- Contains corpora arenacea (brain sand) which are concretions of calcium phosphate located in glia and stroma. Their number and size increase with age.
- Primarily responsible for producing serotonin, melatonin, and other specific peptides(neurohormones). -May play a role in regulating gonadal function and adapting to day-length changes (jet lag) and seasonal affective disorder (SAD).
Thyroid Gland:
- Composed of two lateral lobes connected by an isthmus that crosses the midline of the larynx/upper trachea.
- Usually has a pyramidal lobe extending from the isthmus.
- Typically weighs around 40 grams.
- Covered by connective tissue forming a thin capsule that extends to subdivide the gland into lobules.
- Follicular organization comprises spherical follicles ranging up to 1mm in diameter.
- Follicles are lined with simple cuboidal epithelium resting on a basement membrane.
- The lumen of follicles is filled with colloid which is the stored secretory product of follicular cells, iodinated thyroglobulin.
- Thyroid follicular cells produce thyroxine (T4) and triiodothyronine (T3).
- These cells are the only endocrine cells for extracellular storage of secretory product.
- Follicular cells concentrate iodide 30-fold via ATP-dependent iodide transporters.
- Rough ER synthesizes thyroglobulin.
- Thyroid peroxidase is inserted into the apical membrane to facilitate the oxidation of iodide to free iodine and iodination of thyroglobulin.
- Iodinated thyroglobulin (colloid) is stored in follicle lumen and then taken into follicular cells by endocytosis.
- Colloid is hydrolyzed by lysosomal enzymes and T3 and T4 are released into the blood; MIT and DIT are recycled.
- T3 and T4 act to regulate tissue basal metabolism of carbohydrates, proteins, and fats.
- Parafollicular cells are large cells that stain poorly with H&E and are found within the wall of follicles, underneath the follicular cells and in small clusters within the interstitium.
- They produce calcitonin/thyrocalcitonin which depresses osteoclast activity and increases renal and intestinal calcium excretion; lowering blood calcium levels.
Parathyroid Glands:
- Two small glands located on the dorsal surface of the thyroid gland lobes.
- Composed of two cell types; chief (principal) cells and oxyphil cells.
- Chief cells are relatively small with large nuclei and few small secretory granules and create parathyroid hormone (PTH).
- Oxyphil cells appear later in life (4-7 years), are larger, acidophilic (stain darker) and have numerous mitochondria.
- PTH (parathormone) is produced by chief cells; it's crucial for calcium homeostasis. PTH opposes calcitonin in its action.
- Low blood calcium stimulates PTH to activate osteoclasts to release calcium from bones, and to increase calcium resorption in the kidney tubules and intestines.
Adrenal Glands (Suprarenal glands):
- Located at the cranial pole of each kidney, each is made up of two separate endocrine organs: adrenal cortex and adrenal medulla.
- The cortex is comprised of three zones: zona glomerulosa, zona fasciculata, and zona reticularis each having different types of cells that produces hormones.
- The zona glomerulosa is the outer zone and consist of rounded clumps of cells and produces aldosterone; important for maintaining sodium balance.
- The zona fasciculata is the middle zone, consisting of organized straight cords/columns of cells that produce glucocorticoids, mainly cortisol, critical for metabolism and reducing inflammation.
- The zona reticularis is the inner zone and is highly organized and produces gonadocorticoids, mostly dehydroepiandrosterone and some cortisol.
- The adrenal medulla consist of a network of polyhedral cells, surrounded by capillaries and cortical veins.
- The cells are modified postganglionic sympathetic neurons which are part of the chromaffin system and stain with dichromate salts.
- The adrenal medulla cells produce epinephrine (80%) and norepinephrine (20%), important for the fight-or-flight response.
- Glucocorticoids suppress axon formation of adrenal medullary cells.
- Clinical correlations: include Hypoadrenocorticism (Addison's disease), Hyperadrenocorticism (Cushing's syndrome) and Pheochromocytomas.

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Description

Test your knowledge on endocrine principles with this quiz focusing on hormone mechanisms, characteristics of peptide and steroid hormones, and gland functions. You'll explore the differences between autocrine and paracrine signaling, as well as the roles of key glands in hormone production.