Lab Ten

Question 1

Name the hormones associated with the pars distalis (comprising the majority of the anterior pituitary).

Answer 1

The pars distalis secretes six main hormones:

1. Thyroid-stimulating hormone (TSH)
2. Adrenocorticotropic hormone (ACTH)
3. Follicle stimulating hormone (FSH)
4. Luteinizing hormone (LH)
5. Prolactin (PRL)
6. Growth hormone (GH)

Question 2

Name the hormones associated with the pars intermedia.

Answer 2

The pars intermedia secretes one main hormone:

1. Melanocyte-stimulating hormone (MSH) which stimulates the production and release of melanin

Question 3

Name the hormones associated with the pars nervosa.

Answer 3

The pars nervosa secretes two main hormones:

1. Oxytocin
2. Antidiuretic hormone (ADH) which is also known as Vasopressin

Question 4

Where are the cell bodies located for the neurons which secrete the hormones associated with the pars nervosa?

Answer 4

The cell bodies of the hormones associated with the pars nervosa are located in the hypothalamus.

Question 5

Where is the sella turcica?

Answer 5

The sella turcica is the hypophyseal (pituitary) portion of the sphenoid bone. The turcica is a saddle-like depression in the body of the sphenoid bone.

Question 6

What is the functional significance of the hypophyseal portal system?

Answer 6

There is no direct neural connection between the anterior pituitary and the hypothalamus, but there is a vascular connection. Via the portal system, releasing and inhibitory hormones secreted by the neurons in the hypothalamus circulate directly to the anterior pituitary where they regulate the secretory activity of its hormone-producing cells. Portal systems provide an efficient means of chemical communication by ensuring that all the blood entering the portal vessels will reach the intended target cells before returning to general circulation.

Question 7

Describe the anatomical relationships of the thyroid gland.

Answer 7

The thyroid gland is located anterior to the trachea, just inferior to the thyroid cartilage. The lobes of the gland wrap around the trachea and can be considered to be located on the lateral sides of the trachea, between the trachea and the common carotid arteries.

Question 8

Which arteries supply blood to the thyroid?

Answer 8

The thyroid is supplied by two main arteries:

1. Superior thyroid arteries which are branches of the external carotid arteries
2. Inferior thyroid arteries which are branches from the thyrocervical arteries (like the subclavian arteries)

Question 9

Describe the anatomical locations of the parathyroid glands.

Answer 9

The parathyroid glands are located on the posterior surface of the thyroid gland. Usually, there are two pairs of these glands. One pair on the superior and one pair on the inferior portion of the thyroid. It is important to know that one gland from each pair is located on each lobe of the thyroid gland.

Question 10

Which hormones are produced by the follicular cells of the thyroid and what is its function?

Answer 10

The follicular cells of the thyroid gland produce the hormones thyroxine (T4) and triiodothyronine (T3). Through the conversion of tyrosine, which is a component of thyroglobulin, in the presence of iodine, these thyroid hormones are produced. The functions of the thyroid hormones are to increase cellular metabolism, oxygen consumption, maintain blood pressure, as well as tissue growth and development.

Question 11

Which hormone is produced by the parafollicular (C) cells of the thyroid and what is its function?

Answer 11

The parafollicular cells produce calcitonin. This hormone functions to regulate the calcium ion concentration in body fluids by decreasing the plasmic calcium ion concentration and opposes the actions of parathyroid hormone (PTH), also known as calcitriol.

Question 12

Which hormone is produced by the principal cells of the parathyroid glands?

Answer 12

The principal cells of the parathyroid glands produce parathyroid hormone (PTH) which increases the calcium ion concentration in body fluids. This is considered “essential for life” because calcium ion homeostasis is essential for many normal body functions, including the transmission of nerve impulses, muscle contraction, and blood clotting. Hypothyroidism is characterized by an increase in excitability of neurons leading to a loss in sensation, muscle twitches, and convulsions. If this condition goes untreated, these symptoms progress to spasms of the larynx, respiratory paralysis, and death.

Question 13

Describe the anatomical relationships of the adrenal gland.

Answer 13

The adrenal glands sit on and are attached to the superior part of each kidney. In this position, each adrenal lies between the kidney, the diaphragm, and the major arteries and veins travelling along the dorsal wall of the abdominopelvic cavity.

Question 14

Describe the blood supply of the adrenal glands.

Answer 14

These glands are supplied by the following vessels:

1. Inferior suprarenal arteries which are branches of the renal arteries
2. Middle suprarenal arteries which are direct branches from the aorta
3. Superior suprarenal arteries which are branches of the inferior phrenic arteries

Question 15

Identify the three histological layers of the adrenal cortex and name a hormone produced by cells in each layer.

Answer 15

The adrenal gland has three main histological layers:

1. Zona glomerulosa (outermost layer of the adrenal cortex) which produces mineralocorticoids such as aldosterone
2. Zona fasiculata (middle layer of the adrenal cortex) which produces glucocorticoids such as cortisol and corticosterone

3. Zona reticularis (innermost layer of the adrenal cortex) which produces gonadocorticoids such as androgen

Question 16

Which neurochemicals are produced by the cells found in the adrenal medulla?

Answer 16

The adrenal medulla cells synapse with sympathetic preganglionic axons. In response to stimulation by the sympathetic innervation, these cells produce and release the catecholamines (epinephrine and norepinephrine) which are classical neurotransmitters of the sympathetic postganglionic neurons.

Question 17

Why are adrenal medullary cells considered to be “modified post-ganglionic sympathetic neurons?”

Answer 17

Embryologically, the sympathetic ganglia and the adrenal medulla develop from the same tissue. As a result, the medulla is sometimes viewed as misplaced sympathetic ganglion and its hormone-releasing cells, although lacking nerve processes, are considered to be equivalent to postganglionic neurons.

Question 18

Note the two functional features of the pancreas: exocrine vs endocrine.

Answer 18

Exocrine

The pancreas is mostly made up of exocrine tissue. The exocrine portion of the pancreas consists of the pancreatic acini which account for approximately 99% of the pancreas.

Endocrine

The endocrine portion of the pancreas consists of the pancreatic islets (of Langerhans) which are scattered among the exocrine cells.

Question 19

Name the three cells found in the Islets of Langerhans and the endocrine hormones they produced.

Answer 19

1. Alpha cells - Produce the hormone glucagon (hyperglycemic hormone)
2. Beta cells - Produce insulin (hypoglycemic hormone)
3. Delta cells - Produce somatostatin (which inhibits the release of both glucagon and insulin)

Question 20

Name a hormone produced by the heart, thymus, and kidneys.

Answer 20

Heart: Produced atrial natriuretic peptide

Thymus: Produces thymosin

Kidney: Produces erythropoietin

Question 21

Name three hormones produced by the gastrointestinal tract.

Answer 21

Stomach: Produces gastrin which increases gastric activity

Intestine: Produces cholecystokinin which increases the secretions of digestive juices by the pancreas

Intestine: Secretin increases the secretion of bicarbonate solution from the pancreas

Question 22

Is the pancreas a retroperitoneal organ?

Answer 22

Yes, the pancreas is a retroperitoneal organ.