Pineal, Thyroid and Parathyroid Histology Flashcards
What is the pineal gland named for?
it’s haped like a pine cone
Where is the pineal gland attached?
by a stalk to the roof of the third ventricle
What is the capsule of the pineal gland made of?
pia mater
When during life is the pineal gland the largest?
first decade of life
Where does most of the innervation come from for the pineal gland?
postganglionic sympathetic nerve fibers from the superior cervical ganglion (release epinephrine)
What cells make up 95% of the pineal gland/
pinealocytes
What do pinealocytes produce?
melatonin production at night
What provide supportive role in the pineal gland/
glial cells most similar to astrocytes (can’t identify them on section tough)
The pineal gland sort of looks lobulated on histology. why?
you get fine CT septations formed by the pia mater
Over age, the pineal gland can accumulate what forming “braine sand” - copora arenacea?
hydroxyappatite and calcium
WHy is this brain sand helpful for radiological markers?
it helps the radiologist see the pineal gland and displacement of the pineal form midline is evidence of cerebral tumors
What does melatonin do?
suppresses gonadotrophins secretion via inhibition on the hypohtalamus
retards gonadal growth and function
possibly alters emotional responses to reduced day length during winter months (SAD)
How is the thyroid gland formed embriologically?
endodermal downgrowth at floor of pharynx (between pouches 1 and 2)
The vascular mesenchyme separates this diverticulum into what?
follicles
What bodies from pouch IV fuse with thyroid primordium?
ultimobranchial bodies
What cells are located in the ultimobranchial bodies and from what are they derived?
C cells (parafollicular cells) of neural crest origin
What connects the two lobes of the htyorid?
isthmus
True or false: thyroid has no capsule.
false - has a CT cpasule which is quite delicate
What kidn of capillaries surrund the follicles?
fenestrated
What are some variables that will vary the appearache of the thyroid?
sex, nutrition, temperature, age, season, iodine content, etc.
What cells make up the follicle? What cells are just outside the basement membrane?
follicular cells
parfollicular cells (C-cells)
What do the C cells produce?
calcitonin
In between all these cells is what? What’s stored there?
colloid
stores thyroglobulin, which is the precurosr for T3 and T4
What kind of epithelium is in the follicles?
simple cuboidal epithelium
An inactive (resting) follicular cell will have more or less mitochodnria?
less
and only small golgi
What will be the organelle situation for the active follicular cells?
lots of mitochondira
enlarged golgi
increased rough ER
apical lysosomes to break down the colloid
What will you see in the lipid droplets within the active follicular cells?
PAS-positive colloid (from resoprtion)
What does calcitonin do?
lowers blood calcium by inhibiting bone resorption and decreases osteoclast motility and numbers
promotes excretion of caclium and phosphate from the kidneys
How much thyroid hormone does the thyroid store?
probably a 3-month supply
Where int he cell is thyroglobulin synthesized?
the endoplasmic reticulum
What residues are available for iodination in the thyroglobulin?
tyrosine
How is iodide taken up in the thyroid?
the basal portion of follicular cells have an active iodide transport pump
What happens to the iodide? using thyroid peroxidase at the cell surface…
it’s oxidated to iodine
that iodine is then used to iodinate the tyrosine residues
What enzyme does the iodination?
thyroid peroxidase again (TPO)
What will happen to the follicular cells under TSK stimulation?
- follicle cell height increases
- gland hypertrophy
- accelerated follicular cell metabolism
On to the Parathyroid gland….
1
Where are the parathyroid glands located?
tehre are two pairs located on the posterio surface of each lateral lobe of the thyroid
THey are derived from what pharnygeal structures?
puches III and IV
Describe the parenchymal arragnement in the parathyroids?
anastomosing cords and groups of cells with poorly defined lobules made of fine CT
WHat are the two main cell types in the parathyroid gland?
chief (principal) cells
Oxyphil cells
Which are more numerous?
Chief
Describe what the chief cells look like/
vesicular appearing nucleus
eosinophilic cytoplasm
What hormone is produced by the chief cells?
parathyroid hormone
What does parathyroid hormone do?
involve din regulation of calcium and phosphate levels - increases blood calcium by stimulating increased osteoclasts (by stimulating osteoblastst o produce osteoclast stimulating factor)
Which are bigger - osyphil cells or chief cells?
oxyphil
What is the function of the oxyphils?
we don’t know
True or false: there is no fat in the parathyroids.
false
