Embryology and Anatomy of the Endocrines

Question 1

Where do endocrine glands start originally from?

Answer 1

The GI tract.

In the neck region are the pharyngeal arches from the clefts.

Question 2

Examples of evolutionary compromises:

Answer 2

Wisdom teeth (face shortening)

Foot problems (Due to feet evolving from hands)

Obstetric difficulties (due to evolving vertical stance)

Back problems/disc compression/varicose veins (Due to evolving from hunter gatherers)

Cardiovascular issues (Due to evolving from hunter gatherers)

Diseases of old age (Age of death selected for by evolution)

Question 3

How does the thyroid gland develop?

Answer 3

It develops from an outpouching of the mouth (at the back of the tongue)

Question 4

What problems arise from embryological movement of the thyroid gland?

Answer 4

Cysts and accessory thyroid glands can appear.

Question 5

Where is the thyroid gland located and how rich is its blood supply?

Answer 5

It is located below the larynx. It is the largest endocrine gland and receives the highest rate of blood flow per gram of tissue.

Question 6

What hormones does the thyroid gland produce?

Answer 6

Thyroid follicular cells: Produce thyroxine (T4), triiodothyronine (T3).

Target cells: Convert T4 to T3 which increases oxygen consumption and heat production in the cell.

C cells (parafollicular cells) secrete calcitonin, a hormone that lowers blood calcium by promoting calcium deposition in bone.

Question 7

What causes goiter?

Answer 7

Iodine deficiency causes the thyroid gland to become larger and larger.

Question 8

Where does the parathyroid gland originate?

Answer 8

Starts in one of the pharyngeal arches and travels to the thyroid gland where it fuses.

Question 9

What do the parathyroid glands do?

Answer 9

Important for calcium levels in the blood (PTH)

Question 10

How many parathyroid glands are there usually?

Answer 10

4

Question 11

What triggers PTH production?

Answer 11

Hypocalcaemia, this is because they raise calcium in blood by increasing GI absorption, increase osteoclast activity, and inhibit urinary excretion of calcium.

Question 12

Where is the pineal gland located and what happens to it with age?

Answer 12

It is attached to the roof of the third ventricle and its size gets smaller with age.

Question 13

What does the pineal gland do?

Answer 13

Produces serotonin during the day and melatonin during the night.

Question 14

What does melatonin do?

Answer 14

May suppress gonadotropic secretion and so it is important for sleep induction.

Question 15

Where is the thymus located?

Answer 15

In the mediastinum, it undergoes involution after puberty. It is located under the collar bones.

Question 16

What does the thymus do?

Answer 16

Secretes thymopoietin and thymosins which are important hormones for development and activation of T lymphocytes

Question 17

Are adrenal glands intra or retroperitoneal and what are their parts?

Answer 17

They are retroperitoneal and are composed of an inner core called the adrenal medulla and surrounded by an adrenal cortex.

It is actually a ganglion of the sympathetic nervous system.

Question 18

When is the adrenal gland fully formed?

Answer 18

3 years of age

Question 19

What is the function of the adrenal glands?

Answer 19

Production of catecholamines (into the bloodstream)

Question 20

Where do adrenal glands originate?

Answer 20

From the top of the neural tube.

Question 21

What 3 layers is the adrenal cortex made up of?

Answer 21

The outer zona glomerulosa, middle zona fasciculata, and an inner zona reticularis.

Question 22

What hormones are produced by the adrenal cortex?

Answer 22

More than 25 different steroid hormones that fall into 3 categories: Sex steroids (androgens such as DHEA), mineralocorticoids (aldosterone), and glucocorticoids (cortisol)

Question 23

What stimulates glucocorticoid secretion? What does it do?

Answer 23

ACTH, it stimulates fat and protein catabolism and increases energy supplies in the bloodstream. These hormones are secreted in response to stress.

Question 24

What is the purpose of fat around the adrenal gland?

Answer 24

It acts as a form of lubrication for adrenal gland movement.

Question 25

What disorders arise from adrenal medulla hypersecretion?

Answer 25

Hypertension, elevated metabolic rate, hyperglycaemia, nervousness, sweating, and other disorders

Question 26

What causes adrenal medulla hypersecretion?

Answer 26

Can be caused by a tumour (Pheochromocytoma)

Question 27

What causes adrenal cortex hypersecretion?

Answer 27

A cortical tumour or excessive ACTH

Question 28

What is the result of adrenal cortex hypersecretion?

Answer 28

Cushing syndrome

Question 29

What is the cause of adrenogenital syndrome caused by?

Answer 29

Hypersecretion of adrenal androgens which causes masculinisation of newborn females.

Question 30

What disease results in hyposecretion of glucocorticoids?

Answer 30

Addison’s disease.

Question 31

What are the features of addison’s disease?

Answer 31

Darkened skin, hypoglycaemia, dehydration, hypotension, weakness, and loss of stress resistance.

Question 32

Why is it advantageous for the pancreas to be retroperitoneal?

Answer 32

If there is a pancreatic tumour then the digestive enzymes are limited to the retroperitoneal space rather than the peritoneum where they can digest the structures inside.

Question 33

What 2 ducts lead to the duodenum from the pancreas?

Answer 33

The bile duct and an accessory duct.

Question 34

What is the endocrine tissue of the pancreas called?

Answer 34

Pancreatic islets/islets of langerhans.

Question 35

What important hormones are released by the islets of langerhans?

Answer 35

Insulin (beta cells)

Glucagon (alpha cells)

Somatostatin (delta cells): Chemically identical to growth hormone inhibiting hormone (GHIH) and is secreted by the pancreas as a paracrine secretion.

Question 36

Where and when is estradiol produced?

Answer 36

In ovarian follicles.prior to menstruation and progesterone afterward.

Question 37

What does the follicle produce in order to prevent further release of FSH?

Answer 37

Inhibin

Question 38

Where is testosterone produced in the gonads?

Answer 38

Interstitial cells between seminiferous tubules. These stimulate development of the male reproductive system and masculine physique.

Question 39

What is produced as negative feedback for testosterone production?

Answer 39

Sustentacular cells of the testes secrete inhibin which also slows FSH release.