Endocrine II Flashcards
Describe the covering of the parathyroid glands.
Covered by a collagenous connective tissue capsule which send septa that carry blood vessels, lymphatic vessels, and nerve fibers into the glands
What forms the supporting framework of the parathyroid glands.
Septa and reticular fibers form a supporting framework
What type of capillary network is found in the parathyroid glands?
a fenestrated capillary network
What percentage of the parathyroid gland is adipose tissue in the adult?
60-70%
How are epithelial cells arranged in the parenchyma of the parathyroid gland?
as cords or clusters
True or False: Chief cells are basophilic.
FALSE
eosinophilic
What do the secretory granules of chief cells contain?
parathyroid hormone PTH
enclosed by secretory granules and liberated by exocytosis
Describe the synthesis of PTH.
1) Ribosomes on the rER manufacture preproparathyroid hormone
2) Split as it is carried to rER lumen to form proparathyroid hormone and polypeptide
3) When it enters the golgi, it is split again to parathyroid hormone and polypeptide
What is the function of oxyphil cells?
function unknown
may be dormant, inactive chief cells
How do oxyphil cells stain?
intensely eosinophilic [due to mitochondria]
Which is larger: chief cells or oxyphil cells?
oxyphil cells
What is the function of intermediate cells?
function unknown
What are the three cell types found in parathyroid glands?
chief cells, oxyphil cells and intermediate cells
Is PTH essential for life?
Yes
What does PTH regulate?
calcium and phosphate levels in the blood
[ * it increases blood calcium level, and simultaneously decreases serum phosphate]
What do gland cells detect?
calcium
gland cells have calcium-sensing receptors
How do low levels of serum calcium affect PTH? high levels of calcium?
low serum Ca 2+ –> stimulate release of PTH
high serum Ca 2+ –> inhibit release of PTH
How does PTH influence bone?
- PTH attaches to osteoblast receptors
- casuses osteoblasts to release osteoclast simulating factor which triggers osteoclast activity
- therefore, frees calcium from bone to enter the bloodstream
How does PTH influence kidneys?
PTH prevents calcium loss in the urine
PTH promotes phosphate loss in the urine
How does PTH influence the GI tract?
- By regulating the formation of vitamin D in the kidneys
PTH controls the rate of calcium absorption from the GI. Vitamin D facilitates Ca 2+ absorption from the GI
How do PTH and calcitionin work together?
PTH increases low calcium levels in the blood to normal
Calcitonin decreases elevated calcium levels in the blood to normal
Why can’t surgeons completely remove the parathyroid glands?
Complete removal of the parathyroid glands will drop blood calcium level. This will cause tetanic contraction of muscles, including the laryngeal and respiratory muscles —> death
Describe the connective tissue capsule of the pancreas.
The capsule gives rise to septa which 1) partition the gland into poorly defined lobules and 2) carry blood vessels, lymphatic vessels, and gland ducts
What does the exocrine portion of the pancreas produce?
digestive enzymes
What does the endocrine portion of the pancreas produce?
hormones
Where are islets of Langerhans found?
in the endocrine pancreas
What are the 5 cells found in the islets of Langerhans?
Alpha cells Beta cells Delta cells G cells PP cells (F cells)
How can the different cells int eh islets of Langerhans be differentiated?
immunocytochemical procedures
What hormone is associated with alpha cells?
Glucagon
What does glucagon affect?
Affects liver, skeletal muscle, and adipose tissue
Increases blood glucose levels
What hormone is associated with beta cells?
Insulin
What is the function of insulin?
Decrease blood glucose levels
Somatostatin is associated with which cell in the islet of Langerhans?
Delta cells
What is the function of somatostatin?
Reduces smooth muscle contraction of digestive tract and gallbladder
G cells are associated with ….
Gastrin
Which hormone stimulates synthesis of HCl by parietal cells in the stomach mucosa?
Gastrin
What is associated with PP (F) Cells?
Pancreatic Polypeptide
What does pancreatic polypeptide do?
inhibits pancreatic exocrine secretions
What are the two potential causes of diabetes?
1) beta cells do not produce insulin
2) defective insulin receptors on target cells
What may happen with uncontrolled diabetes?
stroke blindness myocardial infarcts circulatory disorders renal failure gangrene
Describe Type I diabetes.
insulin-dependent juvenile onset (less than 20 yo)
What are three signs of diabetes type I?
polydipsia (excessive thirst)
polyphagia (excessive eating)
polyuria (excessive urination)
Describe Type II diabetes.
non-insulin-dependent
most common type
usually affects individuals over 40 yo
What are the two regions of the adrenal glands?
Cortex (outer)
Medulla (inner)
Which region of the adrenal glands is larger?
Cortex makes up about 90% of the organ
What does the cortex produce?
corticosteroids
What does the medulla produce?
catecholamines (epinephrine and norepinephrine)
Which region is functionally associated with the sympathetic nervous system?
Medulla
What are the three zones of the cortex?
Outer –> inner
Zona glomerulosa, Zona fasciculata, Zona reticularis
What type of cells are found in the zona glomerulosa?
columnar cells arranged in cords and clusters
Describe the cytoplasm in the zona glomerulosa?
ACIDOPHILIC cytoplasm
abundant sER, mitochondria GA, rER, lipid droplets, and free ribosomes
What do the cells in the zona glomerulosa synthesize?
mineralcorticoid hormones
What is the main mineralcorticoid hormone synthesize in the zona glomerulosa?
Aldosterone
What is the target and function of aldosterone?
Target: distal convoluted tubule of the kidney
Function: stimulate water balance, absorption of sodium and excretion of potassium
What is the largest layer of the cortex?
zona fasciculata
What type of capillaries are found in the zona fasciculata?
sinusoidal capillaries
What type of cells are found in the zona fasciculata and how are they arranged?
spongiocytes are arranged in radial columns with sinusoidal capillaries running in between them
- referred to as spongiocytes because the lipid droplet impart a foamy appearance
What organelles are abundant in the zona fasciculata?
abundant sER, golgi, mitochondia, lipofuscin pigment
What do the cells of the zona fasciculata synthesize?
glucocorticoid hormones: hydrocortisol and corticosterone
What is the function of hydrocortisol and corticosterone?
fucntion in control of carbohydrate, fat, and protein metabolism
What causes Cushing’s syndrome (hyperadrenocorticism)?
small tumors of the basophils in the anterior pituitary gland producing excess ACTH with over stimulates the suprarenal cortex leading to excess cortisol production
What are the symptoms of Cushing’s syndrome?
obese, mainly in the face, neck and trunk
Impotency in males
Amenorrhea in females
How does the zona reticularis look histologically?
intensely acidophilic
cells contain lipfuscin pigment
How are cells arranged in the zona reticularis?
cells form anastomosing cords
What do the cells of the zona reticularis synthesize?
weak androgens: dehydroepiandrosterone and androstenedione
What is the suprarenal medulla derived from?
neural crest
True or False: the suprarenal medulla is described as a modified sympathetic ganglion.
True
What two types of cells are found in the suprarenal medulla?
chromaffin cells and sympathetic ganglion cells
What are chromaffin cells?
modified neurons which form cords or clusters
What do chromaffin cells synthesize?
catecholamines: epinephrine and norepinephrine
True or false: catecholamines are responsible for the parasympathetic response.
FALSE
catecholamines are responsible for the sympathetic “fight or flight” response
Which cells in the medulla receive axon terminals of preganglionic sympathetic neurons of splanchnic nerves?
chromaffin cells
- the neurons release Ach
- chromaffin cells are equivalent to postganglion sympathetic cells but have no dendrites or axons
Where are sympathetic ganglion cells located?
In connective tissue of the medulla
Where do sympathetic ganglion cells send their axons?
Send their axons to the cortex where they modulate cortical activity and innervate blood vessels
