A&P 2 Endocrine Pre-Lab Guide Information from Videos and Exercises Read Me In this Pre-lab, we are going over some basic concepts regarding endocrine glands. These notes cover important concepts found in the lab videos. These are notes for both lecture and lab. NOTE: the current videos are old videos, and so the notes may not align exactly with the videos. If you have any questions as to terms, etc., ask the teacher or your SI. NOTE: You will be tested on these concepts in BOTH LECTURE AND LAB. Some of the material will be covered in both! These notes do not appear in the Lecture Notes. For each gland studied in lab, know: - Any tissue layers that are named in the In-Lab Guide. - 1 or 2 representative hormones from each layer. On the lab practical, you will be asked questions such as name a hormone produced by this layer. You will not be asked "name all the hormones made by this gland or layer". That we will save for lecture. - "Typical" abbreviations. In lab, you may use them when naming a hormone on a lab exam. For example, Human Growth Hormone is commonly abbreviated "hgh". - The CELL NAMES as indicated in this document. You are not responsible for visual ID ing all cells, so pay attention to the instruction given in the In-Lab Guide. At the end of this guide, there are some review questions that you may do to assess yourself. Some of the pages have assessments using images and questions from McGraw-Hill Publishers. NO I am not going to simply give you the answers. However, you can ask questions before the next exam/quiz. If there are some questions you can t answer before lab, highlight them and see if you can answer them after lab!
STEP 1. Remembering basic concepts #1 Introductory Instructions For each gland studied in lab, know: - Any tissue layers that are named in the In-Lab Guide. - 1 or 2 representative hormones from each layer. On the lab practical, you will be asked questions such as name a hormone produced by this layer. You will not be asked "name all the hormones made by this gland or layer". That we will saved for lecture. - "typical" abbreviations. In lab, you may use them. When naming a hormone on a lab exam. For example, Human Growth Hormone is commonly abbreviated "hgh". - The CELL NAMES as indicated in this document. You are not responsible for visual ID ing all cells, so pay attention to the instruction given in the In-Lab Guide. #2 Basic concepts: - Endocrine glands make hormones. Hormones are chemical messengers that increase or decrease the activity of other tissues (like neurotransmitters did in the Nervous System chapter). * They use the bloodstream to get where they need to go. - Endocrine glands secrete differently than exocrine glands. See accompanying image. - All tissues and organs can secrete some hormones. The endocrine organs are those that are mostly endocrine tissue. And remember that an organ can fit into more than one organ system (e.g. ovaries, testes, and pancreas). * During the semester. we will be looking at several important organs that secrete important hormones, and yet they are not endocrine organs. These include the heart, liver, stomach, small intestines, and kidney. - Some organs are purely endocrine (e.g. thyroid gland), some are endocrine + exocrine (e.g. pancreas, ovary), others are endocrine + nervous ( neuroendocrine, e.g. hypothalamus, pituitary gland).
- When studying the name of hormones, the word "hormone" is often in the name. Please remember that the words "hormone" or "factor" or "peptide" are often interchangeable in the hormone's name, so these are all the same hormone: Human Growth Hormone Human Growth Factor Human Growth Peptide - Know these endocrine organs. We studied the hypothalamus and pineal gland with the brain, so we will not be looking at slides of that here. We will be studying the other organs aas the semester progresses.
Step 1. The Hypothalamus. We will not be looking at a slide of the hypothalamus in lab. The hypothalamus makes several hormones that stimulate the pituitary to secrete its hormones. A hormone that causes another hormone to be secreted is called a TROPIC hormone (and the word "tropic" or "releasing" is usually in its name). For example, the pituitary gland secretes a hormone called Growth Hormone. It releases this hormone when the hypothalamus secretes "Growth hormone-releasing hormone". Look at the crude drawing of the brain below in Image 1, noting the points in order (first 1, then 2, then 3, etc.). The hypothalamus also makes the 2 hormones that the posterior pituitary secretes: Antidiuretic Hormone (ADH) and Oxytocin. Look at the crude drawing of the brain below in Image 2, noting the points in order (first 1, then 2, then 3, etc.). Image 1 Image 2
Step 2. The Pituitary The pituitary sits in the sella turcica of the sphenoid bone. Actually, the "pituitary" is 2 separate structures: the anterior pituitary, or adenohypophysis, and the posterior pituitary, or neurohypophysis. See image below. The neurohypophysis is not technically a gland; instead, it stores hormones produced in the hypothalamus. However, it is an "endocrine secreting organ", and we will deal with it here. In the image on the right, we are cutting through both glands to see the individual tissue layers. This is what your slides will be showing you. Notice that there is an "inter-glandular cleft". Find it on the image, as well as the anterior and posterior pituitary glands. We will come back to this cleft in a moment, as it is a good landmark on our slides. Notice, on the drawing, the anterior pituitary has 2 obvious layers ("Pars" is Latin for "part"): Pars distalis Pars intermedia There is a trick to understanding the image and slide: The "intra-glandular cleft" is not between the anterior & posterior pituitary. Instead, it is between the 2 layers of the anterior pituitary!!!! The neurohypophyses only has 1 layer, the pars nervosa. The cells are called pituicytes, and they are actually neural cells.
Step 3. The Thyroid & Parathyroid Glands The thyroid gland is found just under the larynx (voice box), just a little lower than the "Adam's Apple". The narrow region in the front is called the "isthmus". The Parathyroid glands are found on the posterior surface of the thyroid gland, and are actually embedded in the thyroid tissue. Notice this! Look at the crude photo of the thyroid gland slide, noting the points in order (first 1, then 2, then 3, etc.). At higher power we can see the follicles of the thyroid, which make and store thyroxine. The fluid within each follicle is called colloid. Surrounding the follicles are other cells, called Parafollicular cells. These cells make another hormone called calcitonin. The parathyroid gland makes parathyroid hormone (PTH).
Step 4. The Pancreas The pancreas has two functional components: endocrine, to produce insulin and other hormones, and exocrine, to produce pancreatic juices for digestion. Here, we will only be talking about the endocrine functioning of the pancreas; we will discuss the exocrine function during the digestion lab. The pancreas is in direct contact with the stomach, duodenum, spleen, and major vessels of the abdomen. The endocrine cells of the pancreas, alpha and beta cells, are found in structures called "pancreatic islands" (the old term, "islets of Langerhans" or islands of Langerhans, is still heard of now and then). We will not be identifying the individual cells, but you should know their names, and what they produce. The exocrine cells are called "acini", which means rice. Look at the accompanying image, noting the points in order (first 1, then 2, then 3, etc.). Notice this! Acini
Step 5. The Adrenal Gland The adrenal glands (also known as suprarenal glands) are endocrine glands that sit atop the kidneys. They are surrounded by an protective Adipose capsule. Look for this in the image to the right. The adrenals are surrounded by a thick protective layer called the renal capsule, which will be visible under the microscope. The adrenals are actually 2 separate secreting organs: the Adrenal Cortex, and the Adrenal Medulla. Find these on the image below. The Adrenal Medulla is chiefly responsible for releasing hormones in response to stress through the synthesis of a group of hormones called the catecholamines (CAT-A-KOL-A-MEENS) - epinephrine and norepinephrine (the "adrenalines"). The Adrenal Cortex is further subdivided into 3 distinct layers which secrete their own families of hormones, seen on the image below. These layers stain differently, and are therefore detectable under the microscope. From superficial to deep, these layers are: Find these on the image below 1. Zona Glomerulosa, which makes the mineralocorticoid (controlling mineral levels in the blood). The most important of these is Aldosterone, which controls sodium levels. 2. Zona Fasciculata, which make a group of hormones called the corticosteroids, controlling blood glucose levels and the body's reaction to stress. Cortisol is the main corticosteroid. 3. Zona Reticularis, which produces the Androgens. Testosterone is the most famous Androgen, and a precursor molecule to Testosterone, is produced here. Note that, therefore, both genders make testosterone. Look at the image below, and relate the layer names on top with the hormone names on bottom: Frontal Section of Adrenal Gland
Step 6. The Thymus Gland The thymus gland is a specialized organ of the immune system. We will study it in more detail during the immunity section. Look at the image to the right while reading this description: The thymus sits just above the heart in the thoracic cavity. When dissected, it has an obvious cortex and medulla, just like the adrenal gland. The thymus is largest and most active during the neonatal and pre-adolescent periods. The thymus produces thymosin, a hormone which helps "matures immune cells in the blood (T cells), which are critical cells of the adaptive immune system. By the early teens, the thymus begins to atrophy and the glandular tissue is replaced by adipose (fat) tissue. Nevertheless, residual T cells continue throughout adult life. More on this during the immunity chapter.
Step 7. The Ovary The ovary is the female gonad (organ that makes the sex cells: sperm and ova or eggs); it is basically an egg sac. It contains millions of non-mature eggs, called follicles. Of course, the ovary has a very important NON-ENDOCRINE function: the production, once a month, of a mature ovum (or egg), which can be fertilized. We will study this in more detail during the "Reproduction Section". However, it also has an important ENDOCRINE function: It produces estrogen and progesterone. Look at the image to the right while reading this description: The ovary is an important part of the female reproductive tract. Once a month, it will release an ovum, where it will drift towards the uterus. The uterus is where a fertilized ovum will develop into a fetus. The ovary is attached to the uterus via the ovarian tube ("Fallopian tube"). Look at the lower image, noting the points in order (first 1, then 2, then 3, etc.) while reading this text: The ovary also has an important endocrine function, as structures within the ovary produce several important hormones. In the image to the right, we are seeing within the ovary (1) an immature follicle (2) maturing into a tertiary, or graafian follicle (3) which is surrounded by a dark ring of cells called Theca cells, important in hormone production. The ovum is ovulated into the fallopian tube (4 is "ovulation"). What is left of the Graafian follicle now grows larger, becoming a Corpus luteum (5). In time, this will break down, decaying into fibrous tissue (6). Both the Graafian follicle and the Corpus luteum make hormones. They are temporary secreting structures that eventually break down if the woman does not become pregnant, and are responsible for fluctuating hormone levels during a woman's reproductive cycle, and will be discussed in more detail during the "reproduction section".
Step 8. The Testes Testes are the male gonads. Like the ovaries, testes are components of both the reproductive system and the endocrine system. The primary functions of the testes are to produce sperm (spermatogenesis) and to produce androgens, primarily testosterone. Look at the lower image, noting the points in order (first 1, then 2, then 3, etc.) while reading this text: