Endocrine Embryology and overview

Question 1

What are the 2 sections of the hypophysis?

Answer 1

Neuro and adrenohypophysis

Question 2

What is the vascular supply to the hypophysis?

Answer 2

Sits within the circle of willis
Blood flows to the hypothalamus -> cap port sys to hypophysis -> drains to cavernous sinus in the base of the skull

Question 3

Where is the hypophysis?

Answer 3

Sits in a recess towards the base of the skull
Recess= basisphenoid

Question 4

What are the parts of the neurohypophysis?

Answer 4

Infundibulum
Neural crest

Question 5

What is the infundibulum of neurohypophysis?

Answer 5

Stalk attached to the hypothalamus

Question 6

What is the neural crest of the neurohypophysis?

Answer 6

Projection of axons from neurones in the hypothalamus

Question 7

What are the parts of the adenohypophysis?

Answer 7

Pars tuberalis
Pars intermedia
Pars distalis

Question 8

What is the function of the pars tuberalis?

Answer 8

Melatonin regulation
(collar around the stalks of the pit gland)

Question 9

What is the function of the pars intermedia?

Answer 9

Negligible function in small animals
Area that surrounds the neurohypophysis

Question 10

What is the function of the pars distalis?

Answer 10

Main secretory region of the AP
Has a collection of cells for each hormone secretion

Question 11

How does the adenohypophysis appear histologically?

Answer 11

Lots of collections of different secreting cells

Question 12

What is the histological appearance of the neurohypophysis?

Answer 12

Herring bodies
Pituicytes

Question 13

What are herring bodies?

Answer 13

Widened terminals of axons containing hormones

Question 14

What are pituicytes?

Answer 14

Specialised glia in the pituitary gland

Question 15

How does the neurohypophysis develop?

Answer 15

Downgrowth of the ectoderm of forebrain (diencephalon)
Retains connection with the brain via the infundibulum

Question 16

How does the adenohypophysis develop?

Answer 16

Upgrowth of ectoderm from the roof of the mouth?
Cups around the neurohypophysis
Loss of connection with the mouth

Question 17

How is the adenohypophysis regulated/ controlled?

Answer 17

Releasing factors from the hypothalamus travel via hypothalamohypophyseal portal capillary system to the adenohypophysis

Hypothalamus -> Neuroendocrine cells -> Hypothalamic artery -> Port Cap sys-> endocrine cells

Question 18

How is the neurohypophysis regulated?

Answer 18

Axons form Supraoptichypophyseal tract + paraventricularhypophyseal tract
Tracts release ADH and oxytocin

Question 19

What are fenestrated capillaries?

Answer 19

Lack tight junctions therefore allow transport of hormones from the hypothalamus to hypophysis

Question 20

What are the cells of the pars distalis?

Answer 20

Lactotrophs
Somatotrophs
gonadotrophs
thyrotrophs
Corticotrophs

Question 21

What is secreted to the pars distalis to stimulate each cell?

Answer 21

Dopamine-> lactotrophs
GHRH-> somatotrophs
GnRH-> Gonadotrophs
TRH -> Thryotrophs
CRF-> Corticotrophs

Question 22

Less light means more?

Answer 22

Melatonin
Less melatonin = inhibits repro cycle in long day breeders
Stimulates repro cycle in short day breeders

Question 23

WHat is the pineal gland responsible for?

Answer 23

Circadian rhythm

Question 24

WHat is the pathway for pineal stimulation?

Answer 24

Optic tract
Reticulospinal tract
T1 thoracic spinal outflow
Cranial cervical ganglion
Post synaptic neurones travel with the blood vessels
Pineal gland

Question 25

What does the pinela gland develop from?

Answer 25

caudodorsal part of the diencephalon

Question 26

What are the cells of the thyroid gland?

Answer 26

Follicular cells Parafollicular cells

Question 27

WHat is the role of the follicular cells?

Answer 27

T3 and T4 production Extracellular storage Have a football like arrangement

Question 28

What is the role of the parafollicular cells?

Answer 28

Calcitonin release Diffusely arranged

Question 29

What is colloid?

Answer 29

Thyroglobulin containing protein Stored extracellularly Surrounding cells add iodine

Question 30

Where do follicular cells develop?

Answer 30

Downgrowth from the pharyngeal endoderm of the tongue

Question 31

Where do parafollicular cells develop>

Answer 31

ultimobrachial body Most caudal pharyngeal pouch

Question 32

What is the blood supply to the thyroid gland>

Answer 32

Paired arteries Cranial thyroid arteries from the common carotid artery Caudal thyroid arteries from the brachiocephalic trunk Venous drainage via brachiocephalic trunk via internal and external jugular

Question 33

How is the thyroid gland innervated and what does this affect?

Answer 33

Autonomic vasomotor supply so change in blood flow = change in thyroid function

Question 34

What is the symp and parasymp supply to the thyroid gland>

Answer 34

SYMP craniocervical ganglion PARA distal vagal ganglion Run along the cranial laryngeal nerve together

Question 35

What is the innervation and blood supply to the parathyroid?

Answer 35

Same as thyroid for nerves Blood supplies are local

Question 36

How does the parathyroid develop?

Answer 36

From pharyngeal pouches pouches 3 and 4 =thyroid and parathyroid

Question 37

How does the adrenal gland develop?

Answer 37

Cortex - mesoderm between gonadal ridge and mesentery - cranial mesonephros Medulla- neural crest

Question 38

What are GnRH cells?

Answer 38

Cells in the brain that control the release of repro hormones

Question 39

Where do GnRH cells migrate?

Answer 39

Start in the olfactory bulb and move to hypothalamus

Question 40

Where do GnRH cells secrete?

Answer 40

Into the hypophyseal portal capillary system

Question 41

What will happen if there is no differentiation of rathkes pouch?

Answer 41

no adenohypophysis Instead there is a pituitary cyst This causes pituitary dwarfism which is common in GSD