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ANATOMY & PHYSIOLOGY HISTOLOGY LABORATORY GUIDE SPRING SEMESTER Histology slides are available in the laboratory for your examination. Several different types of tissue can be seen on many of these slides; you are responsible only for the specific type of tissues described in this exercise. Learn to recognize each type of tissue (underlined names) and each cell structure or detail about each tissue that is included in this exercise. The names of tissues include all underlined words, e.g. stratified cuboidal epithelium. The use of illustrations of tissues in your textbook is essential. It will help you learn them if you draw an illustration of each type of tissue. At first this exercise appears to be difficult, but as you study the slides you will begin to recognize distinct characteristics in each type of tissue. You will discover that only a few tissues look enough alike to make them difficult to tell apart. The best magnification for each tissue is indicated. Follow this procedure for each tissue that you study: 1. Find a micrograph of the tissue in your text or in a histology atlas. Have a clear understanding of what the tissue should look like. 2. Take 2 or 3 slides at a time to your station and return them to their

proper tray. 3. Don't squeeze the slides, because it will damage the soft tissue beneath the cover slip. If you clean them do so carefully.

4. Observe a slide under low power to find the specific tissue that looks like the micrograph. The microscope eyepiece has a magnification of 10 X, so multiply 10 times the number on the objective lens to calculate magnification. For example 10 x 10 = 100, 10 x 40 = 400. 5. Observe the tissue under higher magnification if necessary. 6. Draw an illustration of the tissue and label parts. How you will be tested: On histology exam day in lab, you will be given a paper with a list of 15 structures to find. The objective is to place the microscope pointer on each cell or structure listed on your paper, all from memory, no books or notes allowed. You may go in any order that you choose. Once the microscope pointer has been placed on the cell or structure of your choice, raise your hand and a grader will look at your choice. If you have the pointer on the correct object a circle will be drawn around the number of that question. If the pointer is not on the correct object then one line will be drawn through the number (two points off) and you have another chance. The next try will result in circle over the single line (if you get it right) or and X over the number (if you get it wrong again with four points off). This is the only lab quiz that is not eligible for a drop. All information on the following sheets is fair game for test questions.

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Typical Test Questions: 1. Put the pointer on simple cuboidal epithelium. 2. Put the pointer on a cell that produces growth hormone. 3. Put the pointer on a smooth muscle cell in a respiratory bronchiole. Tissues are classified in four major groups: epithelial, connective, muscle and nervous. The most common types of tissue within each of these four categories are described first, followed by representative organs that consist of several different types of tissues.

EPITHELIAL TISSUE Epithelial tissues or epithelia cover body surfaces and line vessels, ducts and body cavities. Epithelia have a "free" surface on their outer surface and a basement membrane on their deep surface. In most organs, connective tissue lies beneath the basement membrane. Epithelia along with their underlying connective tissue are called epithelial membranes; three types exist. (1) Mucous membranes which line surfaces that open to the outside and secrete mucus and are the digestive, respiratory, urinary and reproductive tracts. (2) Serous membranes line body cavities that do not open to the outside and secrete a lubricating fluid. These membranes line the pericardial, pleural and peritoneal cavities. The epithelial component of serous membranes is known as Mesothelium. (3) The Cutaneous membrane which is skin. Other epithelia line blood vessels and the heart, line ducts and passageways within glands. The epithelial component of the epithelia that line arteries, veins, capillaries, lymph vessels and the heart are called endothelium. Endocardium consists of endothelium and its underlying layer of connective tissue. 1. Squamous epithelium: Find these cells on the slide that is labeled Squamous Epithelium Isolated Homo with the microscope set on 100 X. Then examine them at 400 X. These cells are pink with dark nuclei and look like fried eggs. Their shape is squamous. They have been pulled apart, isolated from each other and placed on the slide. In life these cells were part of a stratified squamous epithelial layer found lining the oral cavity. Other squamous epithelial cells consist of a single layer of cells called simple squamous epithelium that lines blood vessels, capillaries and the heart (Endothelium), body cavities (Mesothelium) and lung alveoli. Thin cells like these are located in places where diffusion is an important function (endothelium, alveoli) or as stratified layers where abrasions ware away the exposed layer of cells (lining of the oral cavity, vagina and surface of the skin). (text figure 4.2 a & b) 2

2. On the slide labeled mesothelium silvered flat mount identify simple squamous epithelium. It looks somewhat like cracked mud on a dry lake. Mesothelium is a specific layer of epithelium that lines serous membranes. This tissue has been pealed off of a serous membrane and placed on the slide, so you are looking at the free surface of these cells. On slides labeled Human Mesothelium section, you are viewing the edge of these cells lying over adipose tissue. Only the thin edge of the organ in these slides is mesothelium. (View at 400 X) 3. Stratified squamous epithelium can be seen in cross-sections of skin. Look at slides labeled Pigmented Epithelium Human or Human Skin. The top layer of cells are stratified squamous and appear like nets or cotton candy superficial to a purple stained layer. This top layer of stratified squamous epithelium is the stratum corneum of the epidermis. The deepest layer of the purple cells is the stratum basale and most of the cells between the stratum basale and the stratum corneum are cells of the stratum spinosum. The deeper tissue is dermis which contains mostly dense irregular connective tissue. (View at 400 X)(text figure 4.2 e) 4. Simple columnar epithelium consists of one layer of tall cells over a layer of basement membrane and connective tissue. These cells form the lining of many parts of the digestive system and are the cells that contact the lumen of the gut. Look at a slide of the digestive system (Jejunum, Duodenum, Intestine, Human Goblet Cells) and examine the innermost "finger-like" edges of the organ. These finger-like structures are intestinal villi which are covered with simple columnar epithelium. Also observe Goblet Cells on these slides. Goblet cells have large white vacuoles (or darker if the mucus is stained) which contain and release mucus onto the gut lining to protect it from digestive enzymes. Goblet cells are single cells that are glands. Each is an example of a simple columnar epithelial cell. (View at 400 X)(test figure 4.2 c) 5. Pseudostratified ciliated columnar epithelium is a tissue that looks stratified, but is actually simple. Look for ciliated columnar cells along the edge on slides labeled Pseudostratified Ciliated Columnar Epithelium. The cilia look like pink fuzz along the free surface. The movement of cilia pushes mucus over the surface of respiratory passages of the pharynx into the throat where it is swallowed. This activity continually sweeps debris out of the lungs. You may also see the Hyaline Cartilage that makes up the tracheal rings in these slides. (View at 430 X)(text figure 4.2 d) 6. Simple cuboidal epithelium can be seen on slides labeled Kidney and Kidney Vascular Injection Cat. Find the cortex and identify the capillary balls that are surrounded by a white space. Each is a glomerulus within a Bowman's capsule. Within the nearby tissue, look for cuboidal cells that make up the walls of tubules. Tubules with the thickest cells are proximal convoluted tubules while tubules with thinner walls are distal convoluted tubules. Capillaries and arterioles can be identified in injected tissues. Locate a pyramid within the medulla of the kidney and find the collecting (papillary) 3

ducts. Collecting ducts can be distinguished from limbs of Henle by their thicker walls, prominent lateral membranes and pale color. Simple cuboidal epithelium is the tissue that PCT, DCT, Ascending Henle and Collecting ducts are made of. (View at 400 X)(text figure 4.2 b, 25.4 c) 7. Transitional epithelium is the lining of the urinary bladder and the ureters and is seen on slides labeled Human Bladder or Ureter. This tissue is specialized for stretching and changes shape as the organ expands and contracts. While relaxed, these cells look billowy or scalloped; the outer surface appearing irregular rather than flat. (View at 400 X)(text figure 4.2 f) CONNECTIVE TISSUE Connective tissues hold organs and tissues together. Most connective tissues have fibers that penetrate into organs binding them together. Most connective tissues consist of a non-living, extracellular matrix that surrounds living cells. The matrix may be hard like bone, soft and pliable like cartilage or even a liquid as in blood. It is made of protein fibers, ground substance and other biochemicals. Fibrous Connective Tissues Fibrous connective tissue includes types of connective tissue other than cartilage, bone and blood. Fibrous connective tissue has several functions including (1) support and holding organs together, (2) storage of fat like adipose tissue, (3) immunity with cellular defense of pathogens like mast cells and macrophages and (4) transportation of nutrients, waste and gas from blood to deeper tissues as the liquid part of areolar connective tissue. The matrix in fibrous connective tissue consists of combinations of the following: (1) ground substance; a gel-like substance (glycosaminoglycans, GAGs) that consists of large molecules that hold water, (2) fibers that are called collagen, elastin and reticulin. A variety of cells are present in fibrous connective including: fibroblasts, adipocytes, mast cells and macrophages. 1. Areolar connective tissue; Also known as loose connective tissue, areolar has white (collagen) and yellow (elastin) fibers in the matrix surrounding the cells which are called fibroblasts. These cells and matrix can be seen on slides labeled Mammal Areolar Connective Tissue, Areolar Connective Tissue. The collagen fibers are wide and pink and faintly visible, but the elastin fibers are dark easily seen threads. This tissue attaches under skin to deeper tissue, and is packing material between many organs. (400 X)

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2. Adipose tissue: These cells are round and contain a large white vacuole that

contains fat and with nuclei and cytoplasm squeezed to the edge. This tissue can be seen on slides labeled Adipose, Mammal Adipose or Mammary. Compared to other connective tissue, adipose is rather vascular. There are very few fibers between cells with very little matrix. Adipose tissue can be found in many organs such as slides of the trachea, bone and muscle. (View at 100 X)

3. Dense regular connective tissue is an avascular tissue that has great tensile strength in one direction. It is the connective tissue that tendons, ligaments, fascia and aponeuroses are made of. The wavy (often pink) collagen fibers are oriented in one general direction and fibroblasts (cells) appear as tiny specks between the collagen fibers. View this tissue on slides labeled White Fibrous Tissue or Tendon at 400 X. 4. Dense irregular connective tissue is vascular with collagen fibers oriented in all directions; it has tensile strength in all directions. It comprises the dermis and is what leather and organ capsules are made of. (View at 400 X). View this tissue on slides that are labeled Pigmented Epithelium Human or Human Skin. 5. Reticular connective tissue is a modified loose connective tissue with an abundance of reticular fibers; sometimes called Type III collagen fibers. Reticular connective tissue forms the framework of liver sinusoids, lymph organs and bone marrow and can be seen on slides labeled Reticular Tissue Mammal. (View at 400 X) Cartilage and Bone Connective Tissues Cartilage and bone are tissues that support a part of the body with their firm or rigid matrix. 1. The hyaline cartilage in the trachea on slides labeled Mammal Trachea, Hyaline Cartilage or Primate Hyaline Cartilage is the central layer of dark purple tissue. Notice the homogeneous matrix surrounding cartilage cells which are located in spaces called lacunae. Fibers are actually present, but difficult to see without special staining. (View at 400 X). 2. Elastic cartilage is similar to hyaline cartilage except for the presence of

numerous elastin fibers which are located between the cells. External ears and the epiglottis are partly made of this tissue. View on slides labeled: Elastic Cartilage at 400 X).

3. Fibrocartilage is what the pubic symphyses and intervertebral discs consist of and is seen on slides labeled Pubic Symphysis or Intervertebral Disc. It contains many collagen fibers that appear to be clustered together in bundles. (View at 400 X). 5

4. Bone tissue is easily recognized by the presence of its haversian canals, which appear in the center of a cylinder called an osteon. Blood vessels fill these canals. Notice the small cells (osteocytes) surrounding the canals. These cells sort of look like tiny bugs, are located within lacunae, and interconnect with other cells through tiny canals called canaliculi. Osteons are present only compact (solid) bone and differ from spongy bones which do not have the osteon. View this tissue on slides labeled Bone Decalcified or Mammal Compact Bone at 100 X) Blood Connective Tissue Blood is a specialized type of connective tissue in which its cells are carried in a liquid matrix called plasma. Blood transports nutrients, gasses and waste throughout the body. 1. Blood consists of an abundance of red blood cells that do not have a nucleus and are pink and white blood cells which are stained purple because of the DNA present in the nucleus stains purple; all carried in plasma. Look at your text and learn to identify Neutrophils, and Lymphocytes; identification of basophils and Eosinophils is not required. Platelets are also present in blood and can be found among the erythrocytes. View on slides labeled Human Blood Film at 400 X).

MUSCLE TISSUE 1. Striated muscle: skeletal muscle tissue is sectioned in both longitudinal and cross section on slides labeled skeletal muscle. In l.s. they appear as long fibers with dark nuclei (like cigarettes viewed from the side), and in x.s. (cross section) as circular polygons (like cigarettes viewed from the ends). Muscle striations can be seen only in l.s. (longitudinal section) and with the microscope light dimmed slightly. Also notice the position of the nuclei in skeletal muscle cells. (View at 400 X) 2. Smooth muscle: smooth muscle is most easily identified in longitudinal sections. Look at the edges to see individual cells. Note the central nucleus and lack of striations. Smooth muscle looks like dense regular connective tissue, except for the presence of many nuclei in smooth muscle. View on slides labeled Smooth Muscle or in any intestine slide at400 X). 3. Heart muscle intercalated discs slides: these sections will probably have both l.s. and x.s. views of heart muscle, so look around for the best cells. Cardiac muscle tissue s striated less clearly than skeletal muscle, but unlike skeletal muscle has dark striations called intercalated discs that pass between the ends of cells. Unlike skeletal muscle, cardiac has nuclei which are located in the

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centers of these cells and have branches between cells. Skeletal muscle does not branch or have interconnecting fibers like cardiac. (View at 400 X) NERVE TISSUE 1. Giant multipolar neurons: The pink octopus-like cells called neurons are a type of nervous tissue. They are unusually large in this tissue which makes them ease to see. Notice the nuclei in the body, and extensions called axons or dendrites of each cell. Axons and dendrites look the same in these tissues. The small cells surrounding these giant neurons are neuroglial cells which support and feed neurons. View on slides labeled Giant Multipolar Neurons at 100 X). 2. Spinal ganglion cat slides: this is a section through the spinal cord of a cat. Some slides will also include spinal ganglia (dorsal root ganglion) which contain spinal nerves which enter the spinal cord. In the center of all slides you will find a tiny central canal which in life contains cerebrospinal fluid. Look to the sides of the central canal for neurons. Since these are cut sections of tissue, only part of each cell can be seen. They appear like starfish and unlike the giant multipolar neurons in the previous slide do not show their long arms. (View at 100 X) 3. Motor end organs: This slide shows the contact between skeletal muscle tissue and motor nerve fibers. The skeletal muscle appears as long pink/purple bundles while the nerve Axons are dark thread-like fibers. At the ends of the axons you will see numerous dark specks which are Motor End Plates. These motor end plates are the locations of synapses or gaps which occur between nerves and muscles and are the points where stimulation for muscle contraction occurs. (View at 100 X) 4. Myelinated neurons: Look at the slide that is labeled Medullated nerve c.s. & l.s. at 40 X. Medullated means myelinated. Identify the longitudinal section of the nerves and the cross section of nerves. The cross section consist of about ten nerve fascicles of variable sizes each surrounded by a yellow stained connective tissue layer of perineurium. Surrounding a group of fascicles is an outer yellow stained layer of epineurium. Find the same layers in the longitudinal section. Now look at the cross section of a fascicle at 400 X. You see many tiny circles with dark specks among them. Each circle is a myelinated neuron consisting of a central nerve fiber surrounded by invisible myelin with some containing a Schwann cell nucleus. Look closely and identify yellow endoneurium, a Schwann cell nucleus and the internal nerve fiber (axon or dendrite). Now look at the longitudinal section at 400 X where you see myelinated neurons from the side. The yellow endoneurium surrounds each neuron and Schwann nuclei are present. Look around and find a node of Ranvier, there are hundreds of them on each slide. They look like two hot dog

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weenies touching end to end. At the node, look to see if the neuron fiber is visible as a faint line passing through the node. SPECIFIC ORGANS 1. ADRENAL GLAND: The adrenal gland is located superior to both kidneys; somewhat looking like a party hat sitting on top of the kidney. A fibrous capsule surrounds the secretory parts of this gland which include the outer cortex and the inner medulla. The adrenal cortex secretes dozens of hormones collectively referred to as corticosteroids and is further subdivided into three layers. The outer most zona glomerulosa lies just beneath the capsule and contains rounded clusters of darkly stained cells that are about eight cells deep. The zona glomerulosa secretes aldosterone, a mineralocorticoid. Deep to the zona glomerulosa is lighter stained zona fasciculata. This layer produces glucocorticoids like cortisol (hydrocortisone), cortisone and corticosterone. The innermost layer of the cortex is called the zona reticularis. It is about the same thickness as the zona fasciculata, but contains cells that are darkly stained. The zona reticularis secretes gonadotropins (sex hormones) such as the testosterone precursor dehydroepiandrosterone, as well as estradiol and other estrogens. The adrenal medulla is derived from an embryonic sympathetic ganglion and produces two hormones epinephrine and norepinephrine. Cells in the medulla are more lightly stained and have larger nuclei than do cell of the zona reticularis. (View at 400 X) (Text figure 16.12) 2. THYROID GLAND: The thyroid is surrounded by a thin capsule. The specimen you see may have connective septa that separate the gland into lobules. Three hormones are produced and released by the thyroid. Two are stored in large follicles that are surrounded by a layer of simple cuboidal epithelium that produces T3 and T4. Less abundant and larger C cells, called clear cells or parafollicular cells, are located between follicles; they produce calcitonin. (View at 400 X) (Text figure 16.7) 3. LIVER: The four lobes of the liver are subdivided into thousands of microscopic lobules. Each lobule is considered to be an individual functional unit in the liver and consists of a central vein from which sinusoids radiate outwardly toward the outer edges of each lobule. Orange connective tissue which holds arteries, veins and bile ducts surrounds lobules. Examine the text illustration (23.24) and locate the following structures on a microscope slide of the liver: A lobule with a central vein surrounded by a connective tissue septum. Notice that many of the central veins in these slides are lined with orange connective tissue. The white spaces that radiate from the central vein are sinusoids while the cells that make up the walls of the sinusoids are hepatocytes. Blood passes through these sinusoids toward the central vein as it is exposed to Kupffer cells which are

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starfish shaped phagocytes that will not be identified here. With your microscope set at 100 X, scan between lobules to find bile ducts. Bile ducts look like tiny circles surrounded by darkly stained cuboidal or columnar cells. Look for arteries and veins between lobules also. 4. STOMACH: Look at a slide of Cardiac Stomach at 100 X and identify the deep layer of smooth muscle tissue. Also identify the surface epithelium that is the lining of the organ and locate gastric pits. Gastric pits are the openings from the surface that lead into deep passages that are called gastric glands. Look at text illustration 23.15 for perspective. Gastric glands are lined with several types of cells including parietal cells and chief cells (you are not required to specifically identify parietal and chief cells). Notice that gastric glands extend deep into the stomach next to the most superficial smooth muscle layer. 5. AORTA: At 100 X, look at the slide that is labeled Aorta Infant and identify the tunica intima, tunica media and tunica adventitia. The tunica media makes up the bulk of this organ and is stained a dark purple. Observe the purple wiggly elastic fibers. The inner layer of tunica intima is a slightly lighter color purple and is only a few cells thick. The endothelium is very fragile and is usually lost during slide preparation. The outer tunica adventitia consists mostly of collagen connective tissue and is stained pink. Find blood vessels, vasa vasorum, within this layer. 6. VEIN: Look at the slide that is labeled Vena Cava Human and identify the tunica intima, tunica media and tunica adventitia. First scan this tissue at 100 X and locate the tunica adventitia which makes up about 75 % of the organ. It is the outermost layer and contains pink collagen fibers which can be identified by the absence of nuclei among them. These collagen "tracts" appear to support bundles of longitudinal muscle fibers of which nuclei can be seen at 400 X. Next locate the tunica intima; a thin layer that has a distinct simple squamous epithelial (endothelium) layer along the inner curved surface of the vessel. The tunica intima is thin in veins being only a few cells in thickness. Deep to this layer is a thin tunica media which consists of circular smooth muscle cells in which the nuclei appear elongate because they have been sectioned lengthwise. Vasa vasorum are probably visible in this organ. 7. HYPOPHYSIS: At 100 X, view a slide labeled Pituitary Gland Human and identify the following structures. You will see blood which is stained bright orange. Blood cells are located in sinusoids throughout the anterior lobe of the pituitary. At 400 X you will be able to distinguish three types of cells in this gland other than blood cells in sinusoids. Brightly stained orange cells are acidophilic (alpha cells) which exist in two forms that can be identified with immunocytochemistry staining techniques that are not shown here. Alpha cells

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produce the protein hormones GH and Prolactin. There are four different types of darkly stained basophilic (basophils) cells which produce glycoproteins hormones TSH, FSH and LH and the polypeptide hormones ACTH and MSH. And finally find the pale chromophobic cells which show little affinity for the dyes. These may be stem cells, undifferentiated progenitors of secretory chromophils, or may produce yet undiscovered hormones. 8. URETER: At 40 X, view a slide labeled Ureter x.s. and located the innermost mucosa layer. The mucosa is darkly stained and about 8 cell layers in thickness and consists of the innermost transitional epithelium and a thin, but stringy layer of supporting connective tissue which can be seen at 400 X. Due to contraction of the smooth muscle cells within the muscularis, the luminal surface is folded, thus creating a star-shaped lumen. Notice that the transitional epithelium cells that are next to the lumen are the largest cells while the basal cells are the smallest. Now view this organ at 100 X and look at the tissues between the mucosa and the outermost part of the ureter. About midway between the mucosa and the outside identify circular smooth muscle in the muscularis layer. These cells stain slightly darker and have nuclei that are elongated. Slightly medial to these cells are longitudinal smooth muscle cells. Likewise, these cells are stained slightly darker than the surrounding connective tissue with nuclei that appear as tiny circles because they are cut in cross section. To the outside of the outermost layer of circular smooth muscle is the adventitia layer which is made mostly of connective tissue. Find adipose cells and blood vessels in this layer. Blood vessels are also present in the muscularis layer and can be identified by the presence of red blood cells. 9. MAMMARY GLAND: At 40 X, view a slide labeled Mammary gland active and identify the red connective tissue septa that surround purple lobules. Mammary glands are branched tubuloalveolar glands; terminal alveoli, which produce and secrete milk, can be identified by their larger size within each lobule. This tissue is easily confused with thyroid, but can be distinguished by finding alveoli that join together in mammary lobules. Alveoli are made of simple cuboidal epithelium and myoepithelial cells; their precipitated product (milk) may be seen within the lumen as well as within the duct passages. Ducts can be identified within the septa and lobules. Some ducts are very large and can be distinguished from blood vessels by the presence of closely packed dark purple nuclei in their walls. Identify adipose tissue located around the edges of this tissue sample. Now look at the slide labeled Mammary gland at 40 X. This organ is inactive and not lactating. Most of this organ consists of dense connective tissue and adipose tissue, but scattered among the connective tissue are immature lobules. Within these lobules are ducts surrounded by light colored areolar connective tissue.

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10. LUNG: Observe a slide labeled Lung c.s. cat at 40 X. Scan the tissue sample from one end to the other and identify air passages. Air passages that have a rippled inner surface are respiratory bronchioles, while those that have smooth inner surfaces are bronchioles or terminal bronchioles. The specimen will also have blood vessels which are indicated by the presence of orange stained blood within. Pick out a respiratory bronchiole and look at it at 400 X. Observe the rippled inner edge which looks somewhat like villi in the intestine and notice that the cells are cuboidal in shape. Also, look at smooth muscle cells that are deep to these cuboidal cells; the rippled appearance is a result of the contraction of these smooth muscle cells. Back off to 100 X and look at the white spaces in this organ; these are alveoli. Some of these white spaces (alveoli) appear to be isolated structures, but most of them are seen joining other alveoli. Find a place where several alveoli open up into a common area; this area is an alveolar duct. Look at a group of alveoli at 400 X. The white area is filled with air and alveolar macrophages while the purple tissue consists of simple squamous epithelium of the alveolar walls (pneumocyte type I), pneumocyte type II cells which produce surfactant and capillaries (you are not required to identify any of these cells). 11. PANCREAS: Observe a slide labeled Islands of Langerhans: pancreas, sec. at 40 X. Identify the thin connective tissue capsule that surrounds this organ and extensions of connective tissue into the pancreas between lobes. Look at the larger end of this specimen and identify orange tubes. If these tubes are lined with cuboidal epithelium they are pancreatic ducts, but if they are not lined with cuboidal epithelium they are blood vessels. You can just make out cuboidal cells at 100 X. Most of this organ consists of lobules containing numerous purple stained tubes (acini) which comprise the exocrine component of the organ. Can you name six zymogens that are produced in these acini? Also within each lobule are lighter colored clusters of cells which are the islets of Langerhans which comprise the endocrine component of the organ. These islets contain (indistinguishable here) Beta cells which produce insulin and Alpha cells which produce glucagon? Look around and find an intralobular duct within a lobule; distinguishable by its cuboidal epithelium lining. Most of these specimens also contain a Pacinian corpuscle.

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