Download Laboratory 11 Anatomy of the Endocrine System

Laboratory 11 Anatomy of the Endocrine System Objectives: •
Identity the anatomical source and functional roles of the major hormones secreted by: o Hypothalamus o Pituitary* o Pineal o Thyroid* o Parathyroid* o Thymus o Pancreas* o Adrenal* o Ovaries o Testes *=Identify the specific cells or region that each major hormone is secreted from using histological samples. 1. Overview of the Endocrine System: Endocrine glands are organs, which synthesize and secrete chemical messengers called hormones into the blood system. Endocrine glands differ from exocrine glands in that exocrine glands secrete the synthesized products into the “external” environment through a duct system whereas endocrine glands generally lack ducts and secrete their products into the blood stream. An individual organ, such as the pancreas, may serve both endocrine and exocrine functions. Further, several organs that are not classic endocrine glands may also secrete hormones such as the kidney, the heart and the stomach. 2. Endocrine glands in the CNS: As you no doubt remember from our neuroanatomy in Biol241, the hypothalamus is a small region of the brain inferior to the thalamus and superior to the pituitary gland that, among other functions, Figure 1. Endocrine organs and hormones in the cervical and cephalic regions. regulates several endocrine responses (Figure 1). The hypothalamus secretes hormones that regulate secretion of hormones from the anterior pituitary and synthesizes hormones that are released from the posterior pituitary. Hormones released from the hypothalamus are listed in Table 1 with the anterior pituitary hormone regulated. Table 1: Hypothalamic and Anterior Pituitary Hormones: Hypothalamic Hormone Anterior Pituitary Hormone Thyrotropin-­‐releasing hormone (TRH) Growth hormone-­‐releasing hormone (GHRH) Corticotrophic-­‐releasing hormone (CRH) Gonadotrophin-­‐releaseing hormone (GnRH) Thyroid-­‐stimulating hormone (TSH) Growth Hormone (GH) Target organ Hormone released by target organ Thyroid Thyroid hormone Calcitonin Liver, Muscles, Bone Insulin-­‐like growth factor (IGF) from liver Adrenal Cortisol, Aldosterone Adenocorticotrophic hormone (ACTH) Follicle-­‐stimulating hormone(FSH) Testes and ovaries Lutenizing hormone (LH) Prolactin Mammary glands Estrogen, Progesterone, Testosterone The pituitary is connected to the hypothalamus by the pituitary stalk or infundibulum and sits in the sella turcica of the sphenoid bone. The pituitary has both an anterior and posterior lobe. The anterior pituitary is glandular tissue. Upon stimulation by stimulating hormones released from the hypothalamus. the anterior pituitary releases hormones that then cause further hormone secretion by a target tissue. The major anterior pituitary hormones are listed in Table 1. In contrast to the anterior pituitary, the posterior pituitary is composed of neural tissues. The cell bodies that synthesize the hormones are located in the hypothalamus with the axons extending through the infundibulum and releasing the hormones from the axonal endings in the posterior pituitary. Note the differences in structure between the anterior and posterior pituitary lobes (Figure 2). The pineal gland is a small endocrine gland located at the posterior to the thalamus in the human brain (Figure 1). This gland receives indirect input from Figure 2. Anterior and Posterior Pituitary at 100X magnification. the eye and secretes the hormone melatonin in response to the absence of light perception by the retina. Melatonin is involved in regulating sleep/wake cycles and in seasonal behaviors, such as mating behaviors in many mammals. • Locate the hypothalamus, anterior pituitary, posterior pituitary and pineal gland on available models. • Examine the histological structure of the pituitary gland. 2 3. Endocrine glands in the cervical and thoracic region: The thyroid gland, the largest of the endocrine glands, is located in the throat just inferior to the “Adam’s apple” (Figure 1). It is composed of two lobes connected by a narrow isthmus. It produces two major hormones: thyroid hormone and calcitonin. Thyroid hormone has two forms, thyroxine (T4) and triiodothryonine (T3). Thyroid hormones regulate the rate of body metabolism and has ubiquitous effects on cellular energy usage. The thyroid gland consists of follicles surrounded by simple cuboidal epithelium (follicle cells) surrounding colloid produces T3 and T4 using iodine (Figure 3). The newly synthesized thyroid hormones are then stored in the colloid to await release. Figure 3. Histology of the thyroid and parathyroid glands (400X). Calcitonin is synthesized and released by parafollicular cells that are located in between the follicles (Figure 3).. Calcitonin release is stimulated by increases in plasma Ca2+ levels and acts to lower blood calcium. The parathyroid glands are small glands located on the posterior surface of the thyroid gland (Figure 1). These glands secrete parathyroid hormone (PTH) in response to low plasma Ca2+ levels and serves to increase blood calcium. Chief cells in the parathyroid secrete PTH (Figure 3). The function of the larger oxyphil cells in the parathyroid is unknown. The thymus is a bilobed gland located just posterior to the sternum and anterior to the heart. It is an important organ in the immune system, serving as the site of maturation of certain white blood cells. It secretes the hormones thymosin and thymopoietin, which regulate the maturation and function of certain white blood cells called T-­‐lymophocytes. • Locate the thyroid gland, parathyroid glands, and thymus on the available anatomical models. • Examine the histological structure of the thyroid and parathyroid glands. 4. Pancreas: The pancreas is an oblong, flattish gland associated with the digestive system. It is located partially inferior to and partially posterior to the stomach and nestled into the bend of the duodenum, or upper region of the small intestine (Figure 4, 5). The head of the pancreas is the enlarged portion adjacent to the duodenum . The body is the main portion posterior to the stomach whereas the thinning, more lateral portion is referred to as the tail and abuts the spleen. The pancreas has both endocrine and exocrine functions. Figure 4. Structure of the pancreas. 3 A majority of the pancreas is composed of tissue related to the exocrine function of secreting digestive enzymes into the duodenum. This part of the pancreas is composed of acinar cells arranged in grape-­‐like clusters and secretes enzymes into the pancreatic duct system. The endocrine pancreas, about 1% of the total pancreas, is composed of clusters of lighter staining cells that look like small islands called islets of Langerhan (Figure 6). Islets of Langerhan are composed of alpha cells that secrete glucagon and beta cells that secrete insulin. These two hormones have antagonistic effects on Figure 6. Histology of the pancreas at 100X. blood glucose. In response to high blood glucose, insulin is secreted and increases storage of the carbohydrate into more complex forms such as glycogen thereby lowering blood glucose. Glucagon is secreted in response to low blood glucose and increases glucose release from adipose lipid stores and liver-­‐stored glycogen. • Locate the pancreas and the anatomical parts of the pancreas on the available anatomical models. • Examine the histological structure of the pancreas. 5. Adrenal Glands The adrenal glands are paired triangular shaped glands located atop each kidney (Figure 5). The glands are composed of two distinct regions, the outer, epithelium-­‐derived cortex and the inner, neural-­‐derived medulla. The cortex produces three major groups of steroid hormones, collectively called corticosteroids. Mineralcorticoids, mainly aldosterone, regulate water and electrolyte balance by regulating sodium reabsorption in the kidneys. Glucocorticoids, such as Figure 5. Endocrine organs and hormones of the abdomen. 4 cortisol [hydrocortisone], increase glucose levels and modulate long-­‐term stress responses. Some gonadotrophins such as testosterone and estrogens are also produce in the adrenal cortex. Each class of steroids is produced by a different layer of cells in the cortex (Figure 7). The most superficial layer, the zona glomerulosa, produces mineralcorticoids in cells that are arranged in irregular clusters. The middle layer, the zona faciculata, produces glucocorticoids and the cells are arranged in long parallel cords. The innermost layer, the zona reticularis, produces gonadotrophins. The adrenal medulla is directly innervated by the sympathetic nervous system (SNS). The cells of the adrenal medulla are modified neurons which release epinephrine (mostly) and norepinephrine when stimulated by the SNS. Epinephrine and norepinephrine modulate the rapid stress response increasing heart rate, blood pressure and blood glucose and mediating the fight-­‐or-­‐
Figure 7. Histology of the adrenal gland. flight response. • Locate the adrenal glands on the available anatomical models. • Examine the histological structure of the adrenal glands. 6. Reproductive Glands: The female reproductive glands, ovaries, are paired oval shaped glands that produce the hormones estrogen and progesterone are are the site of production and maturation of the female gamates. The male reproductive glands, or testes, are located in a pouch-­‐like sac called the scrotum and produces the male hormone testosterone. Estrogen and testosterone are primarily responsible for the secondary sex characteristics in females and males, respectively. • Locate the reproductive glands on the available anatomical models. Figure 8. Reproductive endocrine glands. 5 7. Identification List: In addition to the anatomy know:
hormones secreted,
cell types/histological feature which secrete the hormone, and
stimulus for hormone release.
*=Histology drawing due.
Endocrine Gross Anatomy:
Endocrine Histology:
Thyroid
Parathyroid
Adrenal
Medulla
Cortex
Pancreas
Head
Body
Tail
Pituitary
Anterior
Posterior
Infindibulum
Pineal
Hypothalmus
Ovaries
Testes
Thymus
Pituitary
Anterior*
Posterior*
Pancreas*
Islets of Langherhan
Thyroid*
Follicle
Follicular cells
Colloid
Parathyroid
Chief cells
Adrenal*
Medulla
Cortex
Zona glomerulosa
Zona fasciculata
Zona reticularis
6 Attribution of images used in this document: Figure 1. LadyofHats. (2010). [Endocrine central nervous]. Wikimeida Commons. Retrieved July 16, 2012 from http://commons.wikimedia.org/wiki/File:Endocrine_central_nervous_en.svg. Figure 2. Tacoma Community College. (n.d.) [Anterior and posterior pituitary]. Tacoma Community College. Figure 3. Tacoma Community College. (n.d.) [Histology of the thyroid and parathyroid glands (400x)]. Tacoma Community College. Figure 4. National Cancer Institute. (2009). [Duoadenum and pancreas]. Wikimedia Commons. Retrieved July 16, 2012 from http://en.wikipedia.org/wiki/File:Duodenumandpancreas.jpg.. Figure 5. LadyofHats. (2010). [Endocrine Alimentary System]. Wikimeida Commons. Retrieved July 16, 2012 from http://commons.wikimedia.org/wiki/File:Endocrine_Alimentary_system_en.svg. Figure 6. Tacoma Community College. (n.d.). [Histology of the pancreas at 100x]. Tacoma Community College. Figure 7: Tacoma Community Colleg. (n.d.). [Histology of the adrenal gland]. Tacoma Community College Figure 8: LadyofHats. (2010). [Endocrine reproductive system]. Wikimedia Commons. Retrieved July 16, 2012 from http://commons.wikimedia.org/wiki/File:Endocrine_reproductive_system_en.svg. 7 THIS PAGE IS INTENTIONALLY LEFT BLANK. 8 Laboratory 11 Endocrine Glands 1.
Name:_______________________ Section: __________ For each major endocrine gland, list its anatomic location and the major hormones that it
produces.
ENDOCRINE GLAND
ANATOMIC LOCATION
MAJOR HORMONES
HYPOTHALAMUS
1. Releasing hormones
2. Inhibiting hormones
PITUITARY GLAND
-anterior
1.
2.
3.
4.
5.
6.
-posterior
1.
2.
1.
PINEAL GLAND
THYROID GLAND
1.
2.
1.
PARATHYROID
GLANDS
THYMUS GLAND
1.
PANCREAS
1.
2.
1.
2.
ADRENAL GLAND
-medulla
-cortex
1.
2.
3.
1.
TESTES
OVARIES
1.
2.
9 2. For each of the hormones listed in the following chart, list what organ secretes the hormone, the
hormone’s target tissue and the major effect the hormone has on that tissue.
HORMONE
Organ secretes it
Target Tissue
Hormone effects
Antidiuretic hormone
Oxytocin
Thyroid-stimulating
hormone
Adrenocorticotropic
hormone
Growth hormone
Follicle-stimulating
hormone
Lutenizing hormone
Prolactin
Melatonin
Thyroxine and
triiodothyronine (T3 and
T4)
Calcitonin
Thymosin and
thymopoietin
Parathyroid hormone
Cortisol
Aldosterone
Estrogen
Testosterone
Progesterone
Epinephrine and
norepinephrine
Insulin
Glucagon
10 3. Histology Drawings:
Provide histological drawings the following with the appropriate parts labeled.
Pituitary
Anterior
Posterior
Pancreas
Islets of Langherhan
Acinar cells
Thyroid
Follicle
Follicular cells
Colloid
Parathyroid
Chief cells
Adrenal
Medulla
Cortex
Zona glomerulosa
Zona fasciculata
Zona reticularis
11 12 4. Endocrine Mystery Cases:
In this exercise you will be playing the role of “endocrine detective” to solve various
endocrine mysteries. In each case you will have a victim who has suddenly fallen ill with a
mysterious malady. You will be presented with a set of “witnesses”, each of whom will give
you a clue as to the nature of the illness. Other clues will come from samples that you will
send off to the lab for analysis. You will solve the mystery by providing the victim with a
diagnosis.
Case 1: The Cold Colonel
You are called upon to visit the ailing Col. Lemon. Before you see him, you speak with
three witnesses who were with him when he fell ill.
Witness statements
• Ms. Magenta: “Colonel Lemon has been hot-blooded for as long as I’ve known him.
But I noticed that he couldn’t seem to keep warm. He kept complaining about being
cold….”
• Mr. Olive: “Just between you and me, I’ve noticed that the old chap has put on quite
a bit of weight lately.”
• Professor Purple: “The Colonel and I used to go on major expeditions together. Now
he just doesn’t seem to have the energy to do much of anything.:
What are your initial thoughts about the witnesses’ statements? Does one hormone come
to mind that may be the cause?
You see the Colonel and collect some blood to send off to the lab. The analysis comes
back as follows:
T3 (triiodothyronine): 50ng/dl (normal: 110-230 ng/dl)
T4 (thyroxine): 1.1ug/dl (normal: 4-11 ug/dl)
TSH (thyroid-stimulating hormone): 86 pU/ml (normal: 2-10 uU/ml)
Analyze the results. Why are the T3 and T4 low and the TSH high?
What is your final diagnosis? Explain.
13 Case 2: The Bloated Ms. Blanc
Your next call is to the home of Ms. Blanc. As before, you have three witnesses to
interview.
Witness statements:
• Ms. Magenta: “Between you and me, she has really let herself go. She has fat
deposits in all of these strange places, like around her face and trunk, and a weird
hump on her gack. If you ask me, some exercise may do her some good!”
• Col. Lemon: “Not that I want to talk about such things, but she has seemed bloated,
a bit swollen, lately. She told me that even her blood pressure has gone up!”
• Mrs. Feather: “The poor dear. She has been sick so much lately with all kinds of
infections. Personally, I think her immune system needs boosting. But my herbal
teas don’t seem to help.”
What are your initial thoughts based upon the witnesses’ statements? Does one hormone
come to mind that could produce these effects?
Your next stop is to speak with Ms. Blanc. During the interview you notice a bottle of pills
on her nightstand. You log the pills as evidence and send them off to the lab for analysis.
The lab report shows the pills to be the medication prednisone, which you know to be a
glucocorticoid similar to the hormone cortisol taken to reduce inflammation. Is this finding
significant? Why or why not?
Based on the witness statements and the laboratory analysis, what is your final diagnosis?
Explain.
14 Case 3: The Parched Professor
Your last call is to the aid of Professor Purple. Three witnesses are present from whom to
take statements.
Witness statements:
• Mr. Olive: “I swear that I saw him drink a full glass of water every half an hour today.
He kept saying how thirsty he was!”
• Ms. Blanc: “He must be going to the…well, you know, the little boys’ room, two or
three times every hour!”
• Mrs. Feather: “He has been saying lately that his mouth is dry and that he feels
weak. Personally, I think he’s just not following a healthy diet! He should be drinking
some of my herbal teas!”
Based upon the witnesses’ statements, what are your initial thoughts? Does one hormone
come to mind that could produce these effects?
You interview Professor Purple and collect blood and urine specimens to be sent off to the
lab for analysis. The lab reports that the urine osmolality is 150mOsm/kg, which means that
the urine is overly dilute, and that the blood osmolality is 300mOsm/kg, meaning that the
blood is overly concentrated. What is the significance of these clues?
Based upon the witness statements and the laboratory analysis, what is your final
diagnosis? (Hint: Think of the hormone that is supposed to trigger water retention from the
kidneys. Is there a disease where this hormone is deficient?)
15 THIS PAGE IS INTENTIONALLY LEFT BLANK. 16