Histology of Endocrine Organs Flashcards
1
Q
Which types of glandular cell(s) of the anterior pituitary gland stain acidophilic on H&E?
A
- Somatotropic (Growth Hormone)
- Mammotropic (prolactin)
2
Q
Which types of glandular cell(s) of the anterior pituitary gland stain basophilic on H&E?
A
- Corticotropic (when secreting adrenocorticotropic hormone)
- Thyrotropic (thyroid stimulating hormone)
- Gonadotropic (follicle stimulating hormone, luteinizing hormone)
3
Q
Which types of glandular cell(s) of the anterior pituitary gland are chromophobes on H&E?
A
-Corticotropic when secreting melanocyte stimulating hormone
4
Q
Pineal gland
A
- Role in growth, development & regulating circadian rhythms
- Synthesizes melatonin and serotonin
- Covered w/ pia mater and consists of pinealocytes, neuroglia and calcified granular material –> calcium phosphate crystals (brain sand)
5
Q
Thyroid hormone synthesis and turnover
A
- Thyroglobulin synthesized in the rough endoplasmic reticulum –> glycosylated in the golgia apparatus and secreted by exocytosis into follicle lumen as colloid
- Thyroglobulin is iodinated @ apical surface forming T3 and T4
- Thyroid stimulating hormone stimulates internalization of thyroglobulin via endocytosis and subsequent degradation to free the T3 and T4
- T3 and T4 released from basal surface of follicle cells into circulation
6
Q
Parafollicular C cell function
A
- Located just outside the thyroid follicle cells and secrete calcitonin when blood lvls of Ca2+ are too high
- Calcitonin lowers circulating Ca2+ lvls by:
1. Stimulating Ca2+ secretion from kidneys
2. Decreasing Ca2+ releasing activity of osteoclasts (decreasing bone resorption)
3. Increasing osteogenesis by osteoblasts
7
Q
Control of T3 & T4 release
A
- Via hypothalamic-anterior pituitary negative feedback loop, ex:
1. A stimulus (e.g. low body temp) causes hypothalamus to secrete thyrotrophic-releasing hormone onto the anterior pituitary
2. Thryotropic cells release thyroid-stimulating hormone
3. TSH stimulates thyroid follicle cells to release T3 and T4
4. T3 and T4 stimulate target cells to increase metabolism and increase basal body temperature
5. Increased body temperature detected by hypothalamus and inhibits further secretion of thyrotrophic releasing hormone + elevated thyroid hormone lvls block thyroid stimulating hormone signaling of anterior pituitary
8
Q
Grave’s Disease
A
- Hyperthyroidism due to abnormal antibodies which mimic TSH causing stimulation of the TSH receptors to over secrete T3 and T4
- Symptoms include: elevated metabolism, sweating, rapid heart rate, weight loss and exophthalmos (due to edema behind eye + swelling of eye muscles due to inflammation and increased adipose tissue deposition behind eye)
- 4-8Xs more common in women
- Tx: partial removal/destruction of thyroid or anti-thyroid drugs to decrease thyroid hormone production
9
Q
Hypothyroidism
A
- Insufficient thyroid hormone (T3 and T4) production, often due to autoimmune diseases (e.g. Hashimoto’s thyroiditis) causing follicle cell death
- Symptoms: low metabolic rate, weight gain, lethargy, chilliness, edema and mental sluggish
- Tx: synthetic T3/T4
10
Q
Goiter
A
- Thyroid enlargement most commonly due to iodine deficiency
- Follicle cells keep producing thyroglobulin but cannot iodinate it to make thyroid hormones –> lack of thyroid hormones causes pituitary to release thyroid stimulating hormone to increase thyroid hormone levels, resulting in increased colloid deposition
11
Q
Cells of the parathyroid gland
A
- Chief (principle) cells - release parathyroid hormone when blood [Ca2+] falls below normal range of 9.5-10.5 mg/dL
- Oxyphil cells - much larger cells that stain w/ acidic dyes, appear at puberty and increase in # w/ aging, presence of parathyroid hormone mRNA so may represent aging principle cells
12
Q
Calcium regulation by parathyroid hormone
A
- Blood Ca2+ lvls drop below 9.5 mg/dL
- Parathyroid gland releases parathyroid hormone into the bloodstream and increases blood [Ca2+] by:
a. Stimulating osteoclasts to resorb bone and release its Ca2+ stores
b. Increase Ca2+ by kidneys
c. Stimulating kidneys to convert inactive vitamin D to active form = calcitriol –> calcitriol increases Ca2+ absorption by intenstines - Blood Ca2+ lvls increase and inhibits further parathyroid hormone release
13
Q
Which hormones are released from the zona glomerulosa layer of the adrenal cortex?
A
- Mineralocorticoids (e.g. Aldosterone) –> influence Na+ and K+ levels (salt)
- Secreted in response to a decrease in blood volume or pressure
14
Q
Which hormones are released from the zona fasciculata layer of the adrenal cortex?
A
- Glucocorticoids (e.g. cortisol) primarily from here but also secreted from zona reticularis
- Influences glucose and AA metabolism and uptake
- Suppresses the immune system via negative feedback mechanism (anti-inflammatory action)
- Helps deal w/ stress (e.g. fasting, anxiety, trauma, crowding, infection, etc)
- Secreted in response to adrenocorticotropin hormone released from the anterior pituitary gland
15
Q
Which hormones are released from the zona reticularis layer of the adrenal cortex?
A
- Androgens –> eventually converted to testosterone and estrogen to influence secondary sex characteristics
- Also secrete cortisol
