Histology of the Endocrine System Flashcards
What are the 3 classes of hormone compounds?
- Steroid (lipid-soluble)
- Peptide (water-soluble)
- Amino acid analogues & derivatives (water-soluble)
What class of hormone is secreted by cells of the ovary, testes, & adrenal cortex?
Steroid
What class of hormone is secreted by cells of the hypothalamus, pituitary, thyroid, parathyroid, pancreas, GI, & Resp. Tract?
Peptide
What class of hormone includes thyroxine, epinephrine, and norepinephrine?
Amino Acid Derivates
What gland is found at the base of the brain and is connected to the hypothalamus via a stalk?
Pituitary gland
What are the two parts of the pituitary gland?
Anterior
Posterior
What are the three subdivisions of the anterior pituitary gland? `
- Pars distalis
- Pars intermedia
- Pars tuberalis
What does the posterior pituitary gland consist of?
- Pars nervosa
- Infundibular stalk
What gives rise to the Ant. Pit.? (Embryo)
Ectoderm
What gives rise to the post. pit?
Neuroectoderm
What is the pituitary portal system comprised of?
Primary capillary plexus and a secondary capillary plexus
Hormone releasing factors (RH) are produced by hypothalamic neurons and then released into the…
Primary capillary plexus
From the primary capillary plexus, hormone releasing factors (RH) drain into the….
(This is where they act on endocrine cells in the AP)
Secondary capillary plexus
What 3 cell types are described in the Pars distalis?
- acidophils
- basophils
- chromophobes
What are acidophils?
Bind acid dyes and stain pink or orange
What are basophils
Bind basic dyes and typically stain blue
What are Chromophobes?
Pale-staining and may represent degranulated chromophils
What do acidophils secrete?
Growth Hormone (somatotropin) & Prolactin
(GPA)
What do basophils secrete?
ACTH
TSH
FSH
LH
(B-FLAT)
T/F: Thyrotropes are acidophils
FALSE; basophils
What do thyrotropes produce?
TSH
What are thyrotropes stimulated by?
TRH
TSHa acts on the ____________, stimulating production of _______ & ________
Thyroid
T3 & T4
T/F: Gonadotropes are basophils
True
Gonadotropes provide what hormones in both sexes
LH, FSH
What are the target organs of gonadotropes?
Testes & Ovaries
What are gonadotropes stimulated by?
GnRH
T/F: Corticotropes are acidophils
FALSE; basophils
Corticotropes produce POMC which is then cleaved into _________________
ACTH
What stimulates corticotropes?
CRH
ACTH acts on the ____________ to produce ____________
Adrenal cortex; cortisol
T/F: Somatotropes are acidophils
TRUE
Somatotropes are the most abundant cells in the POSTERIOR pituitary (T/F)?
FALSE - Ant. Pit.
What do somatotropes produce?
Growth Hormone
What stimulates somatotropes?
GHRH
What does GH stimulate?
Liver & other organs to secrete IGF-1 (which promotes stem cell growth)
What does GH target directly (w/ anabolic effects)?
Cartilage & Bone
T/F: Lactotropes are acidophils
TRUE
What do lactotropes produce?
Prolactin - stimulates milk production in the breast
What stimulates and inhibits lactotropes?
Stimulates: TRH
Inhibits: Dopamine
If a patient has a pituitary adenoma and it affects somatotrophs, lactotrophs, and corticotrophs - what would be seen?
Somatotrophs: Excess GH (acromegaly)
Lactotrophs: Excess prolactin, decreased FSH & LH, infertility
Corticotrophs: Cushing’s disease
What do pars intermedia cells secrete?
Melanocyte stimulating hormone (MSH) and endorphins
Which MSH regulated production of melanin?
Alpha-MSH
Posterior pituitary gland is composed of what two things?
- unmyelinated axons
- pituicytes (support cells)
What is a herring body? Where are they found?
-Dilations or swellings of the axon, filled with neurosecretory vesicles
-Post. Pit. Gland Axons
What do herring body swellings contain?
ADH & Oxytocin
What is the function of ADH? When is it secreted?
-Increased water reabsorption back into circulation form filtrate in kidney tubules
-Released in response to extracellular hypertonicity (dehydration)
What is the milk-ejection reflex?
Oxytocin acting on mammary gland, causes milk to be “let down” into lactiferous ducts during lactation
What is parturition?
Causes uterine contractions during the second and third stages of labor (oxytocin)
What does the pineal gland develop from?
Neuroectoderm
What two cell types are in the pineal gland?
- Interstitial glial cells (like astrocytes)
- Pinealocytes (modified neurons)
What do pinealocytes secrete?
Melatonin
When is melatonin secreted?
At night
What inhibits melatonin secretion?
Light input from the eye
What are the calcified concretions found in the pineal gland?
Brain sand (corpora arenacea)
What does the thyroid develop from?
Endoderm
What is unique about how the thyroid stores its secretory products?
-Stores it extracellularly in the lumen. It is in cyst-like follicles.
A thyroid follicle is formed by a _________________________ enclosing a lumen filled with _______________.
Simple Epithelium
Colloid
Colloid is a viscous gel that contains mostly
Iodinated thyroglobulin
What cells types are found in the thyroid follicle?
- Follicular cells
- Parafollicular cells
In the lumen of follicular cells what is found (besides tyrosine residues)
T4. T3
What are the actions of T3 & T4?
-Regulate metabolism and growth
-Increase O2 consumption of almost all tissues
-Bind to nuclear receptors (inc/dec gene expression)
Colloid levels for hyper- and hypo- thyroidism
HYPO: too much colloid
HYPER: too little colloid
what do parafollicular cells secrete?
calcitonin
What is the function of calcitonin?
Lowers Blood Ca++ by inhibiting bone resorption by osteoclasts
What is graves disease?
Autoimmune disease where IgG binds to the TSH receptor on follicular cells, activating the secretion of T4 and T3. Hyperthyroid symptoms.
What do parathyroid glands develop from?
3rd and 4th pharyngeal pouches (endoderm) in early embryo
What two cell types are found in the parathyroid gland?
- Chief cells
- Oxyphil cells
What do chief cells secrete?
Parathyroid hormone (PTH)
What is the function of PTH?
Increase Blood Ca++ levels
How does PTH increase blood Ca++?
-Stimulate osteoblast which then stimulate osteoclast
-Osteoclast resorb bone and release Ca++
What are oxyphil cells?
-Acidophilic cells
-Function not known
Adrenal gland cortex and medulla derivatives
Cortex: Mesoderm
Medulla: Neural Crest Cells
What are the 3 zones in the adrenal cortex (superficial to deep)
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
What 3 hormones are produced by the adrenal cortex (steroid hormones)
- mineralocorticoids (aldosterone)
- Glucocorticoids (cortisol)
- Androgens (DHEA)
3s (Salt, sugar, sex)
The zona glomerulosa secretes what to regulate BP?
Aldosterone
What stimulates aldosterone production?
Angiotensin II
What does the zona fasciculata secrete?
Hydrocortisone (cortisol)
What stimulates glucocorticoid production?
ACTH
What does the zona reticularis produce?
Weak androgens, mainly DHEA
What stimulates androgen production?
ACTH
What do androgens do?
Regulate secondary sex characteristics
What is unique about ZF and ZR mitochondria?
They have tubular cristae in mitochondria
What two cells types are found in the adrenal medulla?
- Chromaffin cells
- Parasympathetic ganglion cells
What are chromaffin cells?
Modified postganglionic sympathetic neurons (NO axons or dendrites)
What do chromaffin cells secrete?
Epinephrine and norepinephrine
What do chromaffin cells synthesize in the adrenal medulla?
Norepinephrine and epinephrine
Describe cortical blood supply to the adrenal gland
ZG:
- Fenestrated capillaries
ZF, ZR:
- Sinusoids supply
Describe medullary blood supply to the adrenal gland
Comes from two sources:
-Venous blood (rich in hormones) reaches the medulla through cortical sinusoids
-Arterial blood reaches the medulla via direct branches from capsular artery
What does contraction of the central adrenomedullary vein do?
-Rapidly released hormones from the medulla into the blood
What is addison’s disease (AD)?
-Adrenal insufficiency (destruction of adrenal cortex) - yields cortisol deficiency, hyperpigmentation of the skin and oral mucosa (from increased MSH secretion)
