14 Cardiovascular System

Transcription

1 14 Cardiovascular System The goal of this topic is to examine and understand the structure of the heart, blood vessels and the lymphatic vessels. You should aim to understand how the structure of blood vessels change from large arteries to the level of capillaries and back to large veins. At each level, the composition of component layers are closely related and adapted to the function at that level. The same principle of relationship between the layer structure and function is seen in the respiratory and digestive systems. The cells in blood are covered in Topic 7 Blood. You should also review contractile cells. This topic deals with the transport system of fluids in the body. For cells and components of blood, review the section on Blood and Bone Marrow. Also review the section on Contractile cells. Objectives Study each of the given types of vessel using the following points: Structure and size of lumen. Presence or absence of the three luminal layers. The thickness of the layers in the vessel. The thickness of the tissue between the different layers. The different types of tissue found in each layer. The presence or absence of vasa vasorum. You should be able to: 1. Describe the general anatomy of the cardiovascular system. 2. Describe how the histological morphology facilitate the functioning of the cardiovascular system. 3. Describe the structure and function of each of the parts of the cardiovascular system. 4. Describe the generic structure seen in blood and lymph vessels. 5. Describe the specific structure seen in each part of the cardiovascular system. 6. Correlate the structural specialisations in each part of the cardiovascular system with the function of that part. 7. Identify and describe the various types of arteries, veins, arterioles, capillaries and venules. 8. Describe the structure of the three types of capillaries. 9. Compare arteries, veins, arterioles, capillaries and venules in terms of structure and function. 10. Compare blood and lymphatic vessels. 11. Explain the structure, function and distribution of valves in the cardiovascular system. 12. Give examples of each of the types of vessels found in the cardiovascular system. 13. Describe the various portal systems and their relevant histology. 14. Identify, describe and compare the various contractile elements found in the cardiovascular system and the rest of the body. 15. Explain the structure and function of valves in the cardiovascular system. 16. Describe the flow of blood to and from the heart from and to the extremities. Slides Slide name Slide number Stain Vessels Muscular artery and vein 69 H/E

2 Muscular artery and vein 70 R/F Elastic artery 67 H/E Elastic artery 49 R/F Large vein 92 H/E Large vein 109 R/F Ductus thoracicus 75 H/E Ductus thoracicus 65 R/F Accessory structure Valve 47 Masson s trichrome Cardiac muscle Heart muscle (longitudinal section) 20 H/E Heart muscle (cross section) 77 H/E Heart muscle 86 Y/H Tasks Study each of the slides, using the guidelines below. Select and compare different types of staining (H/E and R/F) where available and as appropriate. Use the following points and compile a table for each type of vessel. Do this, while studying the specific items for each slide listed below: 1. Structure and size of the lumen. 2. Presence or absence of the three luminal layers. 3. The thickness of the layers in the vessel. 4. The thickness of the subdivision in each layer. 5. The presence or absence of vasa vasorum. Slide 67: Elastic artery Cross section through aorta (H/E) Slide 49: Elastic artery Cross section through aorta showing elastic fibres (R/F) 1. This slide is a cross-section through the aorta. View the slide on low magnification. In this view, you should be able to see the lumen, wall and surrounding structures of the blood vessel. 2. Identify: The lumen of the blood vessel Wall of the blood vessel Adipose tissue surrounding the aorta Vasa vasorum Accompanying blood vessels

3 1. Is this a cross or longitudinal section? Cross section. 2. What is the approximate diameter of the lumen of the blood vessel? Use the scale on the image as a guide. 6 mm 3. What is the approximate diameter of the wall of the blood vessel? Use the scale on the image as a guide. 1.5 mm 4. Name the 3 layers and divisions of the wall of the aorta. See table below. 5. What is characteristic of each layer and divisions of the wall of the aorta? See table below. 6. What is characteristic of the elastic fibres in each layer? TI: fibres TM: fenestrated sheets TA: loose network 7. How is the outer border of the tunica intima determined Innermost sheet of elastic lamella. 8. How does the inner part of elastic arteries receive nutrients? The outer part? Inner part: from the lumen. Outer part: Vasa vasorum 3. View the medium and high magnification slides of the elastic artery. In this view, cellular detail should be visible. Identify the 3 layers of the elastic artery. Identify the tissue components present in each layer of the elastic artery. 4. Make an annotated diagram of a partial section of the wall of the elastic artery, indicating the layers, divisions and tissue components. Clearly indicate the elastic elements in each layer and division. 1. What are identifying features of elastic arteries? Multiple sheets of elastic lamellae in the wall. 2. With increased age and increased blood pressure, a layer in elastic arteries increase in thickness. Name the layer and the component in the layer which cause the increased thickness. The number of fenestrated lamellae in the tunica media increase with age. With hypertension, both the number as well as the thickness of lamellae are increased. 3. Cells in the wall of the elastic artery are involved with repair (normal) and atherosclerosis (pathological). Name the cells and the originating layer. Smooth muscle cells from the tunica media.

4 Slide 69: Muscular artery and medium vein (H/E) Slide 70: Muscular artery and medium vein showing elastic fibres (R/ F) 1. View the slide on low magnification. In this view, you should be able to see the lumens of the blood vessels, the walls and several surrounding structures. 1. How many blood vessels are visible on the slide? 6/5 2. Identify each of the blood vessels on the slide. 3 Arteries, 3 Veins; 2 Arteries, 3 Veins 3. What other structures are visible on the slide? Accompanying nerves. 4. What is present in the areas between the structures? Adipose tissue and loose connective tissue. 2. Identify: The lumens of the blood vessels. Wall of the blood vessels. Tissues surrounding the blood vessels. Structures accompanying the artery and vein. Tissues between the structures. 1. Is this a cross or longitudinal section? Cross section. 2. What is the approximate diameter of each of the structures on the slide relative to the lumen? 1. Large open lumen, relative thin wall. 2. Large irregular lumen, relative thin wall. 3. Lumen (round) and wall approximating each other, lumen still bigger. 4. Big collapsed lumen, thin wall. 5. Big collapsed lumen, thin wall. 6. Big open lumen, thin wall 3. Name the layers found in the wall of a muscular artery and vein. See table below. 4. What are the relative thickness of the three layers of the artery and vein with respect to each other? TI: artery thin; vein thin. TM: artery thick; vein medium. TA: artery medium; vein thick.

5 5. What structure is clearly visible in the wall of the muscular artery? Tunica media. 6. What is characteristic of each layer and division of the wall of the muscular artery and vein? See table below. 7. What cells are normally present in the tissues found between the structures on the slide? See table below. 8. Name the function/s of each of these cells. See table below. 9. Name the 3 layers of connective tissue associated with nerve bundles. Endo-, peri- & epineurium. 3. View the medium and high magnification slides of the muscular artery and vein. In this view, cellular detail should be visible. Identify the cells (or their nuclei) present in each of the various structures visible on the slide. 1. What is diagnostic of each of the cells visible on the slide? Endothelium: flattened with bulging nucleus; smooth muscle cells: spindle shaped with elongated nucleus, contraction causes wavy folds in elastic lamellae. 2. Are the cells visible in cross, diagonal or longitudinal section? See table below. 3. Explain the function of each of the cells present in the structures. See table below. 4. Make an annotated diagram of the low magnification view of the arteries, veins and surrounding structures. For the artery and vein, make and annotated drawing, indicating cellular and structural detail and distribution of fibres. Indicate cross, oblique or longitudinal sections as appropriate. Add the function of each structure. 1. What is characteristic of the elastic fibres of the artery and vein? Less prominent than elastic artery. 2. How are elastic fibres arranged and distributed in the artery and vein? Artery internal and external laminae; Vein loose fibres. 3. How can the arrangement and distribution of elastic fibres be used to distinguish between a muscular artery and vein? See above the arrangements of the elastic fibres.

6 Slide 92: Large vein cross-section through the vena cava (H/E) Slide 109: Large vein cross-section through the vena cava showing elastic fibres (R/F) 1. View the slide on low magnification. In this view, you should be able to see the complete blood vessel, and some of the surrounding tissues. Slide 109 shows only part of the wall of the vessel. 2. Identify: The lumen of the blood vessel. Wall of the blood vessel. Smaller blood vessels in the surrounding tissues. 1. What is characteristic of the lumen of the vena cava as seen on slide 92? The lumen is relatively large, and collapsed. 2. Are there any clearly defined layers or structures visible at low magnification? Yes. A thin dark inner band, a striped layer and then bundles. 3. View the medium and high magnification slides of the large vein. In this view, cellular detail should be visible. 1. What are the layers seen in the wall of the vena cava? See table below. 2. Does the layers in the wall of the vena cava show further divisions? Name the divisions. See table below. 3. What are characteristic of each of the layers and divisions seen in the wall of the vena cava? See table below. 4. Make and annotated diagram of the complete vein, including surrounding structures. For a partial section of the wall of the vein, make a detailed drawing showing cellular detail and distribution of fibres. Indicate cross, oblique or longitudinal sections as appropriate. Add the function of each structure. 1. What is the relationship of the three layers with respect to each other? TI & TM relatively thin, indistinguishable, smooth muscle cells circumferential; TA thick, smooth muscle cells longitudinal. 2. How are elastic fibres distributed in each layer? TM circumferential, TA longitudinal.

7 Thoracic Duct Various Slide 75: This slide is a cross section through the thoracic duct (H/E). Slide 65: This slide is a cross-section through the thoracic duct showing elastic fibers (R/F). 1. View the slide on low magnification. In this view, you should be able to see the ductus thoracicus and the surrounding connective tissue. 2. Identify: The lumen of the ductus thoracicus. The epithelium lining the lumen. The different layers comprising the wall of the lymph vessel. The surrounding connective tissue. 1. Name the epithelium lining the ductus thoracicus. Endothelium. 2. List the layers and divisions of each layer comprising the wall of the ductus thoracicus. Same 3 main layers as arteries and veins, but less defined. Smaller lymph vessels: too delicate to be a vein, too large to be a capillary. 3. What tissue surrounds the ductus thoracicus? Adipose tissue, loose connective tissue. 3. View the medium and high magnification slides of the ductus thoracicus. In this view, cellular detail should be visible. Identify the cells present in each layer of the lymph vessel. Identify the cells present in the surrounding connective tissue. 1. Name the cells present in each layer of the wall of the ductus thoracicus. TI: endothelium; TM: smooth muscle cells, TA: smooth muscle cells. 2. Are the cells orientated parallel or perpendicular to the direction of flow in the vessel? Parallel to the flow. 4. Make an annotated diagram of the complete ductus thoracicus, including the surrounding connective tissue. For a partial section of the wall of the ductus thoracicus, make a detailed drawing showing cellular detail and distribution of fibres. Indicate cross, oblique or longitudinal sections as appropriate. Add the function of each structure. 1. Describe each layer in the wall of the ductus thoracicus. TI: thin with lamina elastica interna; TM: thickest with smooth muscle cells; TA: not well defined, smooth muscle cells. 2. How is the elastic fibres distributed and arranged? Mostly absent. 3. How does the layers seen in a lymphatic vessel correlate and differ from that of arteries? And veins? Layers are very ill-defined in lymph vessels and consists mostly of varying amounts of connective tissue and smooth muscle. Smooth muscle in media is orientated circularly

8 and longitudinal in adventitia. Questions 1. What are the two main component parts of the circulatory system? Blood circulation and lymph circulation. 2. In this drawing of the endothelium of an elastic artery, which direction does blood flow take place?

9 3. Describe the maintenance and regulation of blood pressure based on the histological morphology of the circulation system. Rhythmic contraction of cardiac muscle force blood into arteries, which pulsate. Elastic lamellae in the arterial wall of elastic arteries expand passively to store some of the force. Potential energy from elastic tension is released by elastic recoil during diastole, continuing forward motion. This result in steady blood flow, especially in the terminal parts of the arterial macrovascular system. Muscular arteries regulate blood flow to specific tissues and organs. Never supply in the tunica media controls the contraction and dilation of smooth muscle cells in the media. Smooth muscle fibers and precapillary sphincters of the microvascular system regulate blood flow into the capillary bed. During inspiration, negative pressure is created in the thoracic cavity. Blood is returned to the heart with assistance of the negative pressure, compression of the veins by skeletal muscle and the prevention of back flow by valves. 4. On a histological section, what can be used to initially differentiate between arteries and veins of all sizes? Size of the lumen compared to the thickness of the vessel wall: Arteries have a small lumen, relative to the wall; veins have a large lumen, relative to the wall. Collapsed or open lumen: Lumen of arteries are usually open, vein, collapsed. 5. Make a schematic diagram, showing the regions and major structural features of blood vessels in each region. Indicate the function of each region.

10 You should have on your drawing the following items: Macrovascular and microvascular system. Heart, elastic arteries, muscular arteries, arterioles, capillaries, cells, venules, valve, vein. Histological features should include: tunica intima, media and adventitia, smooth muscle cells, pre-capillary sphincters, pericytes, endothelial cells, basal lamina, capillaries. 6. What is the function of elastic arteries? Conduction tubes. Maintain continuous and uniform movement of blood flow. 7. On a histological section, what can be used to initially differentiate between arteries and veins of all sizes? Thick walls keep arteries open, whereas thin-walled veins appear collapsed. 8. What is the function of lymphatic vessels? Collect and return interstitial fluid and protein (lymph) to the blood stream. Trafficking route for cells of the immune system during immune surveillance and infection.

11 Facilitate lipid absorption from the digestive track. 9. What are end-arteries? Arteries normally form anastomoses with each other. An end-arteries is an artery that is the only supply of oxygenated blood to a region. No anastomoses occur, and occlusion of the vessel results in necrosis. 10. How are the central artery of the retina, coronary arteries, segmental arteries of the kidneys and arteries entering the brain different from arteries in the rest of the body? Arteries normally form anastomoses. In case of occlusion, for example a cut throught the skin, little or no problems result. These group of blood vessels does not have anastomoses and occlusion will result in necrosis. 11. How are the central artery of the retina, coronary arteries, segmental arteries of the kidneys and arteries entering the brain similar? These are all end-arteries. Arteries normally form anastomoses, providing blood in case of occlusion in one part. In some areas, no anastomoses exist. These are called endarteries. Occlusion results in necrosis. 12. What happens when end-arteries are occluded? Necrosis in the region supplied by the end-arteries. 13. What is a portal system? Give an example of portal systems. A system of vessels interposed between two capillary beds. Examples are the portal veins, hypophyseo-portal system and the glomerulus in the kidney. 14. Compare the structure of the vena cava with elastic arteries. The tunica media is the thick in the artery, thinner in the vena cava. The aorta contains smooth muscle and elastic lamella layers, whereas there are only smooth muscle layers in the vein. 15. There is no clear dividing line between elastic and larger muscular arteries. Name 4 characteristics that is used as diagnostic of muscular arteries. 1. Elastic material decrease 2. Smooth muscle cells predominant in TM 3. Prominent lamina elastica interna 4. Often also clear lamina elastica externa 16. What morphological feature is characteristic of medium veins? Valves, particularly in the inferior part of the body. 17. What mechanism facilitate return of blood to the heart? Gravity superior to the heart. Valves inferior to the heart. Muscle action on the blood vessels. 18. Describe the general structure of veins in comparison to arteries. Larger diameter, thinner walls collapsed on slides. More connective tissue. Same 3 layers, but no lamina elastica interna or externa boundaries less distinct. Thinner tunica media. Upper body thin media drain by gravity. Lower body thicker media due to more smooth muscle cells active propulsion of blood towards heart.

12 Structure varies a lot, arbitrarily divided into small, medium and large veins. 19. The ductus thoracicus ultimately starts as a blind-ending tube in the micro-capillary beds. 20. What mechanism drives lymphatic flow? Valves to prevent back flow driven by compression of adjacent skeletal muscle. Memorandum Slide Is this a cross or longitudinal section? Cross section 2. What is the approximate diameter of the lumen of the blood vessel? Use the scale on the image as a guide. 6 mm 3. What is the approximate diameter of the wall of the blood vessel? Use the scale on the image as a guide. 1.5 mm 4. Name the 3 layers and divisions of the wall of the aorta. See table below. 5. What is characteristic of each layer and the divisions of the wall of the aorta? See table below. 6. What is characteristic of the elastic fibres in each layer? TI: fibres TM: fenestrated sheets TA: loose network 7. How is the outer border of the tunica intima determined? The outer border of the TI is the innermost fenestrated elastic layer. 8. How does the inner part of elastic arteries receive nutrients? The outer part? Inner part: diffusion from the lumen; outer part from vasa vasorum Elastic artery elastic membranes aorta, subclavian, pulmonary trunk, pulmonary arteries, common carotid artery conducting Layer Division / Component Description / Characteristic Function Tunica intima Relatively thick Endothelium Oriented parallel to direction of blood flow Synthesize and secrete vwf into the blood. Basal lamina thin Support endothelium Subendothelial CT Smooth muscle cells Longitudinal Contractile

13 Secrete: Ground substance fibers Fibroblasts Scattered Fibers elastic & collagen Amorphous ground substance Lamina elastica interna Innermost elastic layer Tunica media Thickest Smooth muscle cells spiral layers Synthesis of CT Repair of vascular wall Atherosclerosis Fenestrated sheets elastin Collagen fibres Elastic fibers Amorphous ground substance Lamina elastica externa Fibroblasts Concentric ^Number + ^thickness with ^age Outermost elastic layer Holes facilitate diffusion of substances Tunica adventitia Relatively thin Connective tissue layer Collagen fibres Circular bundles Prevent expansion beyond physical limit during systole (bursting). Elastic fibres Loose network Cells: fibroblasts & macrophages Blood vessels (vasa vasorum) Nerves (nervi Penetrate media Nutrients to outer layer of wall

14 vascularis) Muscular artery Muscular artery smooth muscle majority of arteries, most of the rest distribution Layer Division / Component Description / Characteristic Function Tunica intima Thinner than elastic ^age > ^thickness due to lipid deposition Endothelium Basal lamina Subendothelial CT flattened thin sparse may contain smooth muscle cells longitudinal Lamina elastica interna Well defined Wavy Tunica media Smooth muscle cells spiral fashion contraction Collagen fibers Little elastic material No fibroblasts Lamina elastica externa layers maintain BP Tunica adventitia thick = TM Loose CT Fibroblasts Collagen fibers Elastic fibers longitudinal longitudinal Adipose cells Blood vessels (vasa vasorum) Penetrate and supply TM & TA Unmyelinated

15 sympathetic nerves Large vein Large vein vena cava, portal veins, brachiocephalic veins, renal veins return blood to heart Layer Division / Component Description / Characteristic Function Tunica intima Not clearly defined Endothelium Basal lamina Subendothelial CT Smooth muscle cells Tunica media Relatively thin or absent Smooth muscle cells circumferentially arranged Collagen fibers Some fibroblasts Tunica adventitia Thickest Collagen fibers Elastic fibers longitudinal Fibroblasts Smooth muscle cells longitudinal Small to medium veins Small to medium veins Layer Division / Component Description / Characteristic Function

16 Tunica intima Endothelium Basal lamina Subendothelial CT Smooth muscle cells Lamina elastica interna Thin Thin Few Thin if present Tunica media Thin Smooth muscle cells Just below TA Circular?? Longitudinal?? Collagen fibers Elastic fibers Scattered fibroblasts Tunica adventitia Thicker Loose CT Collagen fibers Elastic fibers Longitudinal Network Few fibroblasts Few smooth muscle cells Vasa vasorum, lymph vessels, unmyelinated nerve vessels In medium veins Tunica intima Tunica media Tunica adventitia Small veins Endothelium 3 layers circular smooth muscle cells Collagen mm Thin BL Elastic fibers Few fibroblasts Medium veins Endothelium 3 4 layers smooth muscle cells Main part

17 Superficial and deep veins Thin BL Separated collagen fibers Loose CT Deep veins Veins of the viscera 1 10 mm Thin subendothelial CT Scattered fibroblasts Thick collagen fibers Valves folds of intima (absent CNS & viscera) Some elastic fibers Large veins Endothelium Thin or absent Thick Smooth muscle cells Vasa vasorum, lymph vessels & nerves Vena cava Portal veins Renal veins Thin BL Smooth muscle cells Elastic fibers >10 mm Thin subendothelial CT Smooth muscle cells No valves Vasa vasorum, lymph vessels & nerves Venules Collapsed lumen Thin endothelium lymphoid organs = cuboidal epithelium Thin BL Pericytes External to this: 1. Fibroblasts 2. Collagenous fibers Larger venules 1/2 layers flattened smooth muscle cells Venules Site of lymphocyte and granulocyte migration Layer Division / Component Description / Characteristic Function Tunica intima Endothelium Basal lamina Pericytes Cuboidal in lymphoid organs Thin Incomplete initially, bigger vessels Primary site vasoactive agents

18 complete Tunica media Absent / Present 1 2 layers smooth muscle flattened Tunica adventitia Ductus thoracicus as example of lymphatic vessels Endothelium tubes lacking continuous BL. Allows high permeability. Increased thickness increased CT bundles smooth muscle. Scratch Xxxxx Comparison of Tunics in Arteries and Veins General appearance Tunica intima Tunica media Arteries Thick walls with small lumens Generally appear rounded Endothelium usually appears wavy due to constriction of smooth muscle Internal elastic membrane present in larger vessels Normally the thickest layer in arteries Smooth muscle cells and elastic fibers predominate (the proportions of these vary with distance from the heart) Veins Thin walls with large lumens Generally appear flattened Endothelium appears smooth Internal elastic membrane absent Normally thinner than the tunica externa Smooth muscle cells and collagenous fibers predominate

19 Comparison of Tunics in Arteries and Veins Tunica externa Arteries External elastic membrane present in larger vessels Normally thinner than the tunica media in all but the largest arteries Collagenous and elastic fibers Nervi vasorum and vasa vasorum present Veins Nervi vasorum and vasa vasorum present External elastic membrane absent Normally the thickest layer in veins Collagenous and smooth fibers predominate Some smooth muscle fibers Nervi vasorum and vasa vasorum present xxxxx

20 16 Digestive System Objectives You should be able to: The purpose of this topic is to practically illustrate the structures, organs and glands of the gastrointestinal tract. The secretory units which were covered in the session on glandular epithelia, should be reviewed for the salivary glands and pancreas. You should know how the histology of the stomach, small and large intestine varies, and how this is related to function, the roles of the liver, pancreas and gall bladder in digestion, and how their structure is related to function. The digestive system can be divided into three parts: 1. Upper Digestive Tract (oral cavity, oesophagus and stomach). Histology of the structures found in and around the mouth, the oesophagus and stomach. 2. Lower Digestive Tract (duodenum to anus). Most digestion and absorption takes place from the duodenum to the ileum. The colon and lower digestive tract is involved with water balance and excretion. 3. Accessory organs. Those organs whose primary function related to the digestive system. These include the liver, gall bladder and pancreas. Digestive system in general You should be able to: 1. Describe the generic components, organisation and functions common to most of the digestive tract. 2. Describe how the basic organisation of the digestive tract is modified along its course. 3. Relate the structure to the function of each section of the digestive tract. 4. Describe the morphology and histology of each component of the digestive tract. 5. Describe functional variations related to differing functions. 6. Relate the morphology with the function of each component of the digestive tract. 7. Describe the appearance, organisation and functions of the epithelial cells throughout the digestive system. 8. Discuss the distribution of lymphoid tissue in the digestive system. 9. Identify and describe the cells found in the various areas of the digestive tract. 10. Describe the specialised functions of cells found in the various areas of the digestive tract. 11. Identify and describe the intrinsic glands of the digestive tract. 12. Describe the surface topology of the mucosa of the digestive tract. 13. Identify the layers of the digestive tract and compare cross and longitudinal appearance. 14. Define the cellular composition of the mucosal layers and their function. 15. Describe changes in layers in the transitional areas of the digestive tract. Upper digestive tract You should be able to: 1. Describe the characteristics of the lip. 2. Name and identify the papillae on the tongue. 3. Name, identify and compare the salivary glands. 4. Identify and describe the structure and function of the salivary glands. 5. Describe and identify the histological structures of teeth. 6. Identify and describe the oesophagus. 7. Identify the regions of the stomach.

21 8. Identify the different types of secreting cells in gastric glands., and the function of each. Lower digestive tract You should be able to: 1. Identify the neural tissue in the intestines and the coats in which they are found. 2. Distinguish between the various sections of the small and large intestine. Accessory organs You should be able to: 1. Describe the organisation of liver tissue. 2. Recognise and describe the histological structure and function of liver lobules. 3. Explain how blood and bile pass through the liver lobules and relate this to liver function and pathologies. 4. Identify and describe the structure of the gall bladder and bile duct. 5. Identify and describe the structure and function of the exocrine and endocrine pancreas. General approach Following a systematic approach when looking at each slide will assist you in correctly identifying the tissue and spotting key elements. Key elements are set out below: xxxxxx 1. Always start by viewing the section at low magnification to orientate yourself as to the general structure. Look for the lumen, epithelial surface and layering. Can you spot changes in the 1. First, always scan each section at low power. Look for obvious junctions, for example between the esophagus and stomach. 2. Next, identify the four layers characteristic of the G.I. tract: mucosa, submucosa, muscularis externa, adventitia/serosa. If these 4 layers are present you must be viewing part of the alimentary tube. 3. Once you have identified the 4 layers of the G.I. tract, look for the key structural features within each layer for each specific region of the tract. For example, stratified squamous epithelium lines the esophagus and anal canal, whereas simple columnar epithelium lines the stomach, small intestine, and large intestine. However, these GI organs with simple columnar epithelium can be distinguished by several criteria, most importantly by differences in mucosal folding. There are pits leading into coiled glands in the stomach, villi and straight glands (crypts) in the small intestine, and straight glands (crypts) in the large intestine. Thus villi are unique to the small intestine. TO HELP YOU KEEP TRACK OF CHANGES IN THE VARIOUS LAYERS, CLICK HERE FOR AN EXCEL SPREADSHEET THAT YOU CAN FILL IN AS YOU WORK THROUGH THESE SLIDES (click here to see a filled in version to check your work). 4. Cross-sectioned villi and glands will both appear as circular structures. However, in villi the surface epithelium will be seen enclosing cellular connective tissue (lamina propria), whereas in glands the epithelium will ring open spaces--the lumens of the glands. 5. At the end of this section of the lab manual you were issued, you will find a Review Exercise Chart (click here for a PDF version of the chart) that you should fill in to remind you of the key features of each region. As a study aid, relate structure with function. For example, absorptive cells with microvillus brush borders are found in the small and large intestine where most absorption takes place. 6. Use the orientation of the muscle layers of the muscularis externa to determine the plane of section for each slide. A cross-section of the tube will show longitudinallysectioned muscle in the inner layer and cross-sectioned muscle fibers in the outer layer, whereas these relationships are reversed in a longitudinal section. (An oblique section of the tube cuts both muscle layers obliquely).

22 7. The textbook, lecture Powerpoints, and lecture notes should be helpful during slide examinations. List the organs and accessory organs involved with the digestive system. Describe the anatomy of the organs and accessory organs involved with the digestive system. Discus ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation from the viewpoint of the relevant histology. Refer to cells, tissues, organs and structures. What role does the cells of the liver, pancreas and gallbladder play in digestion? Seen from a cellular level, how is the blood flow through the liver important for digestion in general and drug therapy specifically. Describe how the basic arrangement of the layers and structures in the wall of the digestive tract varies, depending on the differing functions of the different parts. Describe how blood passes through the liver at a histological level. How does the composition of blood change as it passes through the liver lobules? Liver Discuss the blood supply of the liver 1. Define the concept of the classic liver lobule and recognize it in histological tissue sections 2. Learn about the structure of portal triads and identify its components 3. Understand the structure of hepatic cords and liver sinusoids 4. Learn about and identify the cells of the liver tissue: hepatocytes, Kupffer cells, endothelial cells and Ito cells 5. Discuss the functions and ultrastructural features of hepatocytes 6. Understand the concept of the Acinus of Rappaport 7. Discuss the production of bile and the cellular structures involved 8. Study the histological features of the gallbladder Oral cavity Know the location and histological similarities and dissimilarities among the different types of oral mucosae (lining, masticatory, specialized). 1. Know the histology of the tongue including the different types of papillae. 2. Know the histology of the adult tooth and name the cells responsible for the production of enamel, dentin, and cementum. 3. Describe how the tooth is anchored in alveolar bone. 4. Know the structure of the epithelial attachment and understand its significance in protecting the periodontal space. Pharynx, Esophagus, and Stomach Be able to describe the layers in the wall of the digestive tract (mucosa, submucosa, muscularis (propria), and adventitia/serosa), and explain how they differ in the pharynx, esophagus, and stomach. 1. Know the histological differences in the pharynx and the upper, middle and lower portions of the esophagus. 2. Be able to recognize gastric glands, identify their constituent cells, and know their secretory products. 3. Be able to differentiate gastric glands, cardiac glands, and pyloric glands.

23 The wall of the gastrointestinal tube consists of 4 major layers (W pgs ): the mucosa, the submucosa, the muscularis (also called muscularis propria or muscularis externa) and the serosa (if covered by peritoneum) or adventitia (if retroperitoneal). The mucosa, in turn, consists of an epithelium, a supporting lamina propria of loose connective tissue and a thin, usually double, layer of smooth muscle, themuscularis mucosae. The four major layers will be examined in each region of the digestive system. The mucosa differs considerably from region to region, reflecting changing functional activity. Be sure to identify these differences. The other layers in the wall change rather little, although there are subtle differences also in these layers that can also help you identify particular regions of the GI tract. To help you keep track of changes in the various layers, you can fill in this spreadsheet as you work through today's and next week's labs. Salivary Glands Be able to identify parotid, submandibular and sublingual salivary glands on the basis of histological appearance and by the types of secretion produced by each gland. 1. Be able to identify striated ducts of the salivary gland at the light and electron microscope level and correlate the structural features of the constituent cells to the functions of these ducts. 2. Know the localization of myoepithelial cells and nerves in relation to the acinar cells, and their role in secretory functions. We will study three major salivary glands; the parotid, submandibular, and sublingual glands. These glands are divided into numerouslobules which contain the secretory units, which are called acini. Each secretory unit consists of acinar (secretory) cells and branching ducts. Ducts within lobules (intralobular ducts) connect with larger interlobular ducts which are found in the connective tissue between lobules. Small and Large Intestine Be able to describe the layers in the wall of the digestive tract (mucosa, submucosa, muscularis externa and adventitia/serosa), and explain how they differ in the small and large intestines. 1. Be able to identify and know the general functions of the following regions of the GI tract: Duodenum Jejunum/ileum Colon Appendix Rectum Anal canal To help you keep track of changes in the various layers, you can fill in this spreadsheet as you work through today's and next week's labs. Describe the histological characteristics of the layers comprising each segment of the gastrointestinal tract and describe how they relate to their function Name and describe four transitional junctions in the GI tract Describe the topography of the gastric gland, its component cells, and architectural differences between glands in the three regions of the stomach Describe the structure of the small intestine, how its surface area is maximized, and the cells that comprise its epithelium Contrast the histological appearance of the large intestine from that of the small intestine Identify a few key pathological examples regarding the GI tract

24 Describe the organization of and roles played by the salivary glands, pancreas, liver, and gall bladder in initiating and facilitating particular digestive processes Contrast the three types of salivary glands, their component cells, and secretions Name the exocrine cells of the pancreas and explain how they are organized Describe the structure of the liver lobule and its component cell, the hepatocyte, and how this structure is related to the flow of blood and bile Draw a connection between the structure of the pancreas and salivary glands Identify some key pathological examples involving these organs xxxxxx Slides Slide name Slide number Stain Oral cavity Lip 51 Tooth (longitudinal section) 25 Tooth (cross section) 23 Tooth (ground longitudinal section) 27 Tooth (ground cross section) 16 Tongue (tip) 7 Papilla fungi & filiformes 53 Papilla circumvalata 33 Parotid gland 85 Submandibular gland 35 Sublingual gland 107 Upper digestive track Esophagus (cross section) 31 Esophagus-stomach junction 101 Fundus 37 Pylorus 38 Stomach-duodenal junction 36 Lower digestive track Duodenum 40

25 Ileum 41 Appendix vermiformis 43 Colon 42 Rectum-anal-skin junction 45 Liver Liver (pig) 68 Liver (human) 46 Liver (injected) 110 Liver (reticular fibres) 48 Accessory organs Gall bladder 58 Pancreas 50 Tasks General 1. Make a table and list, for each of the slides, the following: 1. Mucosa Type of epithelium Cell types present in epithelium Features of mucosal glands Features of lamina propria Muscularis mucosae 2. Submucosa 3. Muscularis externa 4. Serosa or Adventitia If a heading is not applicable, make sure to explicitly state so, and do not just leave the listing empty. 2. Make an annotated diagram of the general structure of the digestive track. Use the following word bank to populate your diagram: muscle coat, submucosa, mucous membrane, villi, lymphoid nodule, epithelium, lamina propria, muscularis mucosa, serosa, external gland, mesentery, submucosal gland, Meissner's plexus, Auerbach's plexus. Note: You can add additional terms as well as substitute terms. 3. Name the four layers making up the general structure of the digestive track. 1. Mucosa

26 Epithelium: stratified squamous, simple columnar Lamina propria: loose connective tissue = blood and lymphatic vessels, lymphoid follicles. muscularis mucosae: smooth muscle 2. Submucosa: loose connective tissue 3. Muscle layer Two layers of smooth muscle cells, inner circumferentially, outer longitudinal. Separated by nervous tissue, myenteric plexus. 4. Serosa/Adventitia Loose connective tissue covered by mesothelium Only loose connective tissue. 5. +Glands Isolated mucosal secretory cells. Lamina propria of mucosa. Submucosa External connected with ducts. 4. What are the general content of each of the four layers of the digestive track? 5. List the epithelium found in the complete digestive track, starting and ending with keratinized stratified squamous epithelium. 6. Describe the general distribution of glands in the digestive track. 7. What structures are found in the submucosa? 8. Give the distribution of the serosa and adventitia throughout the digestive track. 9. Describe the morphology of the serosa seen in the digestive track. Slide specific tasks Slide 51: Lip (H/E) 1. View the slide at low magnification. At this view, the four zones of the lip should be visible. 1. What are the four zones visible on the surface of the lip? Hairy skin, vermilion border, vermilion and oral mucosa. 2. The lip is a mucocutaneous junction. What is a mucocutaneous junction? Give examples of mucocutaneous junctions. 3. Name the epithelium found in each of the four zones of the lip. 4. Name the three main layers of skin, the subdivisions of each and the structures found in each. 5. What is the difference between the outer and inner surface of the lip? Outer surface contain the normal structures found in skin, covered with keratinized stratified squamous epithelium. The inner surface is devoid of hair, and covered with

27 stratified squamous epithelium. The dermal papillae of the inner surface of the lip are increased in number and more vascular, but does no dermal appendages are present. 2. View the slide at higher magnification. Cellular arrangements should become visible. 3. Identify the following: 1. The different parts of the surface of the lip. 2. Muscle tissue. 3. Connective tissue. 4. Labial glands. 1. What type of contractile tissue is present in the lip? Striated muscle running in various directions. 2. How is the contractile tissue arranged? 3. Give the complete classification of the labial glands. 4. What type of connective tissue is present in the lip? Fibro-elastic connective tissue. 4. Make an annotated line drawing of the histology of the lip. Indicate the structures of the lip, and the functions of each structure. Slide 16, 23, 25 and 27: Tooth Slide 25: Tooth (longitudinal section; H/E) Slide 23: Tooth (cross section; H/E) Slide 27: Tooth (ground longitudinal section) Slide 16: Tooth (ground cross section) 1. You should know the parts of the tooth and be able to recognise the parts of the tooth on a slide. Structures and cells of and found in association with a tooth: blood vessels, pulp, dentine, enamel, odontoblasts, cementum, periodontal membrane, crown, root, root canal, alveolar bone, pulp chamber, gingiva. 2. View the tooth slides on low magnification. You should see the enamel and root canal of the tooth. In the haematoxillin stained sections, the alveolar bone is also visible. 3. Identify the structures and cells associated with the tooth, on both cross and longitudinal sections. 4. Make an annotated line drawing of a cross and longitudinal section of the tooth, indicating the various parts as identified above. 1. Enamel is analogous to epithelium, covering the surface of the tooth and derived from epithelium. 2. What is characteristic of the pulp?

28 3. What is the layer of cells found against the dentine called? 4. What is characteristic of cementum? 5. What are the collagen fibres of the periodontal ligament known as? 6. What is characteristic of the gingiva? 7. What is the granular layer of Tomes? 8. What are Retzius lines? 9. Define and describe spindles and tufts? 10. What cells are responsible for the secretion of dentine? Slide 7: Tongue a coronal section through the distal part of the tongue (H/E) 1. View the slide at low magnification. The free surface and attached area should be visible. Below the free surface, layers of muscle tissue interspersed with glandular tissue is visible. Blood vessels and scattered fat cells are also present. 2. View the slide at high magnification. Cellular detail should now be discernible. 1. What is secreted by the glands in the tongue? 2. What type of epithelium is present on the dorsal surface of the tongue? 3. What type of epithelium is present on the undersurface of the tongue? 4. Muscles normally have an origin (fixed) and insertion (moving). Muscle fibres run longitudinally between the origin and insertion. In what direction does muscle fibres of the tongue run? 3. Identify the following tissues and structures in the tongue: 1. Papillae 2. Epithelia 3. Muscle fibres 4. Fat cells 5. Glandular tissue. 4. Make an annotated diagram of the tongue, indicating the different layers, tissues and structures. 1. Twist and fold your tongue. Why is the tongue able to perform such complex movements? 2. How is the anterior and posterior parts of the tongue divided? 3. How does the anterior and posterior parts of the tongue differ?

29 Slide 53: Papillae fungi- and filiformes (H/E) Slide 33: Papilla circumvalata (H/E) You should be able to identify and differentiate between the three types of papillae seen on the tongue. Papillae are surface structures and as such are covered with epithelium. You should know the type of epithelium covering the papillae and the glands associated with the papillae. 1. View the slides on both low and high magnification. Look at the shape of the papillae and their placement in the epithelium of the tongue. 1. Name the three types of papillae found on the tongue. 2. What is the shape of each of the papillae found on the tongue? 3. How are the papillae distributed on the tongue. 4. Where are the glands found in relation to the papillae? 5. Classify the glands fully. 6. Where are taste buds found in the digestive track? 7. What are the glands of Ebner? 8. What are the functions of the glands found in association with the papillae? 2. Make an annotated diagram of each of the three types of papillae. 3. Make an annotated diagram of the surface of the tongue, indicating the distribution of the papillae and landmark on the surface of the tongue. Slides 85, 35 and 107: Salivary glands Slide 85: Parotid gland a section through the parotid salivary gland (H/E) Slide 35: Submandibular gland a section through the submandibular salivary gland (H/E) Slide 107: Sublingual gland (H/E) 1. View the slides at both low and high magnification. At low magnification, lobes, ducts and general structure should be visible. At higher magnifications, the acini and cells forming the acini is visible. Epithelia of ducts should also be identifiable. 1. Name the six types of contractile cells. 2. Which contractile cell/s are associated with salivary glands? 3. Where in salivary glands are contractile cells seen? 4. Give the complete classification of glandular tissue. 5. Name the three types of cellular secretion. 6. Which type of cellular secretion is active in salivary glands? 7. Secretory material from salivary glands are contained in zymogen granules. 8. Compare the three salivary glands in a table with regards to the following: Type of secretory units. Type of secretions.

30 Relative frequency of secretory unit types. Type of ducts. Cells, tissues and structures seen in the gland. 9. Identify the following structures of each of the salivary glands: 1. Connective tissue septae. 2. Blood vessels. 3. Secretory units. 4. Secretory ducts. 5. Zymogen granules. 1. Give a complete classification for each of the three salivary glands. 2. Name the organ most commonly associated with pseudostratified columnar epithelium. 3. Describe the morphology of ducts found in salivary glands and the associated epithelial progression. Intercalated ducts striated ducts interlobular ducts Simple cuboidal simple columnar tall columnar pseudostratified columnar stratified columnar 4. Where does centro-acinar cells occur? 5. Does salivary glands have centro-acinar cells? 10. Make an annotated drawing of the secretory units of each of the salivary glands. Give a clear indication of the relative frequency of the different secretory units. Slide 31: Oesophagus Cross section through the oesophagus (H/E) 1. Consider the macroscopic structure and function of the oesophagus and answer the following questions: 1. What is the function of the oesophagus? Transport ingested food from the oral cavity to the stomach. 2. What transitional areas are seen in the oesophagus? Epithelium: Stratified squamous (oesophagus) to simple columnar (stomach). Glands: Oesophageal glands in submucosa higher up; cardiac glands in the mucosa lower down. Muscle: Skeletal muscle in the upper third; smooth muscle in the lower third, mixed in the middle third of the oesophagus. 3. How are muscle types distributed in the oesophagus? Smooth muscle in the muscularis mucosa of the lamina propria; mixed in the muscular layer: skeletal muscle in the upper third; smooth muscle in the lower third, mixed in the middle third of the oesophagus. 4. Is the surface of the oesophagus flattened or folded? Folded.

31 5. How does the lumen of the oesophagus appear? Folds. 2. View the oesophagus at low magnification. All layers, from the lumen of the oesophagus to the surrounding adventitia should be visible. Identify the following: 1. Lumen of the oesophagus. 2. Folded epithelium. 3. Glands in the lamina propria. 4. Papillae 5. Glands 6. Adventitia 1. What are the three main layers of the oesophagus? Mucous membrane, muscle layer, adventitia. 2. What type of epithelium is present in the oesophagus? Stratified squamous epithelium. 3. What is the function of this epithelium in the oesophagus? How is this different from the rest of the digestive track? Protective vs absorptive. 4. What type of glands are located in the oesophagus? Mucous throughout. 5. In which of the three main layers of the oesophagus does the glands occur? 6. What is analogous between the muscle layers and glands of the oesophagus? 7. Describe the contractile components of the oesophagus. 8. What does the adventitia consist of? 3. View the oesophagus at higher magnification. Some cellular detail may be visible. 1. Where are the nerve supply found in the oesophagus? 4. Identify the transitions between the different layers of the oesophagus. 1. Describe the border between the epithelium and the lamina propria. 2. How is the border between the epithelium and the lamina propria similar to the border between the epidermis and dermis of skin? 3. Describe the structure of the muscular layer. 5. Make an annotated line diagram of the oesophagus, showing the layers and contents of each layer and the divisions of each layer. Use the terminology used in the drawing of the general structure of the digestive track as a resource.