Thyroid phys Flashcards
gastrulation
the formation of the ectoderm, endoderm, mesoderm
mesoderm becomes
muscles and skeleton
endoderm becomes
respiratory tract, digestive tract, liver, pancreas
ectoderm becomes
outer layer of the skin, hair, lining of nose and mouth, nervous system
facial cleft, auricular atresia, and micrognathia are due to
1st branchial arche and/or 2nd branchial arche
branchial cleft cyst is due to
failure of one of the four branchial arches to involute
one of the most common congenital abnormalities of the head and neck
branchial cleft cyst
when will a branchial cleft cyst get larger
respiratory infection
grow through life
where is a branchial cleft cyst found
lateral
anterior to the sternocleidomastoid
branchial cleft cyst versus lymph node
branchial - fluctuant
lymph node - firm
most common branchial cleft cyst
2nd branchial cleft cyst
where does tongue originate
between 1st and 2nd pharyngeal arch
outpouching between 1st and 2nd pharyngeal arch
foramen cecum; where the thyroid originates
3rd pharyngeal pouch becomes
inferior parathyroid
4th pharyngeal pouch becomes
superior parathyroid
when does the thymus atrophy
with age
most common place for thyro-glossal duct cyst
infra hyoid (inferior parathyroid has to traverse a further area)
what is a sinus tract
an opening with drainage
can a branchial cleft cyst or a thyroid-glossal duct cyst become a sinus tract
yes, they both can
when does a thyro-glossal duct cyst move
when you stick out your tongue (remember than the foramen cecum is connected to the tongue originally)
branchial cleft cysts are closely associated with
carotid arteries
are branchial cleft cysts or thyro-glossal duct cysts generally painful
no
where is the thyroid located
in the neck anterior to the cricoid cartilage
what does the thyroid require for production of active hormone
iodine
where is thyroid hormone stored
extracellulary in the thyroid colloid
is thyroid hormone stored in the thyroid cells?
no; it’s stored in extracellularly in the colloid
function of follicular cells
produce and secrete thyroglobulin into thyroid colloid
uptake of iodine via Na/I transporter
function of thyroglobulin
important for transport of tyrosine
important for iodinating tyrosines to develop into T3 and T4
parafollicular cells are also called
C cells
function of parafollicular cells
synthesize calcitonin
step 1 when creating T3 and T4
iodine comes into follicular cell via Na/I transporter
2nd step when creating T3 and T4
amino acids come in to form thyroglobulin (which is a protein)
3rd step when creating T3 and T4
thyroglobulin and iodine are transported into the colloid
4th step when creating T3 and T4
thyroid peroxidase (TPO) iodinates tyrosines within the thyroglobulin (we are still in the colloid now)
5th step when creating T3 and T4
iodinated tyrosines couple to make T3 and T4 (we are still in the colloid)
6th step when creating T3 and T4
thyroglobulin with iodinated tyrosines are endocytosed back into follicular cell
7th step when creating T3 and T4
thyroglobulin is digested by lysozymes –> release of T3, T4, rT3
release of amino acids and extra iodine for recycling
8th step when creating T3 and T4
T3, T4, and rT3 are diffused into systemic circulation
which steps are NOT stimulated further by TSH
-amino acids forming thyroglobulin
-thyroglobulin and iodine are transported in a vesicle to colloid
TSH exerts what type of effect
growth factor effect –> hyperplasia of thyroid
increased TSH –> growth of thyroid
which has a larger half life between T4 and T3
T4
once T3 and T4 are diffused into systemic circulation, what do they bind to
thyroid binding globulin
does thyroid binding globulin have a high affinity for T3 and T4
yes
what percent of T4 is bioavailable/free
0.02%