endocrine embryology

Question 1

common component of all endocrine organs

Answer 1

mesodermal component which gives rise to vasculature

Question 2

what gives rise to brain and spinal cord

Answer 2

neural ectoderm

Question 3

what gives rise to the mouth

Answer 3

ectoderm- comprises the tissues as far back as the pharynx (the pharynx is endodermal origin) in th upper mouth. In lower mouth, ectoderm gives rise to tissues half way along the length of the tongue.

Question 4

define stomodeum

Answer 4

mouth opening

Question 5

origin of posterior pituitary

Answer 5

neural ectoderm evaginates at 4 weeks forming the posterior pituitary and central portion of infundibular stalk, plus the median eminence

Question 6

origin of anterior pituitary

Answer 6

At 4 weeks, oral ectoderm from upper part of mouth evaginates forming rathkes pouch, and comes in contact with neural ectoderm. This pouch pinches off from oral epithelium and develops into anterior pituitary. The

Question 7

Origin of the sella turcica

Answer 7

connective tissue which develops around the pituitary

Question 8

origin of pituitary vasculature

Answer 8

local mesoderm infiltrates the pituitary giving rise to hypophyseal portal system and small vessels in posterior pituitary

Question 9

Be able to describe the origins ofthe pars distalis, pars intermedia, pars tuberalis, pars nervosa and infundibular stalk.

Answer 9

pars tuberalis, intermedia and distalis are from oral ectoderm. Pars nervosa and infundibular stalk are from neural ectoderm

Question 10

origin of thyroid follicle epithelial cells

Answer 10

endoderm

Question 11

origin of calcitonin secreting cells in thyroid

Answer 11

neural crest- originally ectodermal

Question 12

origing of thyroid vasculature

Answer 12

mesoderm

Question 13

origin of parathyroid glandular cells

Answer 13

endoderm- inferior parathyroids from cleft btw 3rd and 4th pharyngeal pouches. Superior parathyroids from cleft after 4th pharyngeal pouch

Question 14

describe thyroid gland formation

Answer 14

Medial evagination of endoderm btw first and second pharyngeal pouches forms (thyroid diverticulum) > the diverticulum enlarges and descends in the pharynx connected via the thyroglossal duct > the thyroid descends until in front of trachea > thyroglossal duct degenerates

Question 15

what is the ultimobranchial body

Answer 15

group of cells that form just below the 4th pharyngeal pouch which gets populated by neural crest derived cells and cells that give rise to calcitonin secreting cells of thyroid.

Question 16

How does the parathyroid and calcitonin cells become integrated into the thyroid

Answer 16

During the thyroids descent, it comes in contact with primordia of parathryoids and the ultimobranchial body, which both become embedded in the thyoid resulting in parathyroids and calcitonin releasing cells respectively

Question 17

How does the cellular composition of the thyroid change

Answer 17

initially it is a solid mass of endodermal cells, but these get interspersed by infiltrating mesoderm into cords of cells (which will become follicular cells) then to small clumps which then form the epithelia of follicles

Question 18

origin of adrenal cortex and medulla

Answer 18

Cortex arises from mesoderm (mesothelium between the dorsal mesentery and urogenital ridge) and medulla arises from ectoderm

Question 19

Another name for urogenital ridge

Answer 19

wolffian body

Question 20

describe development of the adrenal cortex

Answer 20

At 4 weeks, mesonephric or wolffian duct induces cells in the cleft btw dorsal mesentery and urogenital ridge to migrate into the mesenchyme dorsal to it > They form a cup structure > at 2-3 months another wave of clls from coelomic epithelium (mesothelium) enter the mesenchyme and surround the outer part of the cup

Question 21

origin of the layers of the cortex

Answer 21

Reticularis: first round of cells that arrive from the coelomic epithelium. Fasciculata and glomerulosa: second group of cells that arrive from coelomic epithelium.

Question 22

How does the adrenal cortex change after birth

Answer 22

a portion of the inner region of the early reticularis regresses. The layers of the fasciculata and glomerulosa become more distinct

Question 23

development of adrenal medulla

Answer 23

Neural crest cells migrate to become sympathetic ganglia (sympathogonia) and some of them then migrate into the center of the cup.

Question 24

Chromaffin cells

Answer 24

The early progenitors of the epi and NE producing cells of the medulla which migrate from the neural crest. They stain yellow brown with chrome salts

Question 25

how does the adrenal medulla change after birth

Answer 25

It increases in volume.