Gastro-Intestinal Tract - 2 Objectives: At the end of this session you should be able to: 1. Recognise and describe a section of liver appreciating how each lobe is constructed from a large number of lobules with portal areas and how bile and blood flow through and are transported in and out of this organ. 2. Recognise and describe a section of gall bladder. Appreciate why, despite its similarity to the rest of the GIT, its structure is relatively simpler;(because it is merely a storage bag). 3. Recognise and describe a section of pancreas representing both exocrine and endocrine units. 018 LIVER SLIDE 17 pig liver (H&E and PAS section) Identify: liver lobule, portal area, liver cords, sinusoids and central vein. In the PAS stained section note the PAS- positive pink glycogen granules in the hepatocytes. Identify in portal areas at higher magnification cross sections of: hepatic artery hepatic portal vein bile ducts lymphatics 1 Q 1. How would you distinguish between them the cross sections of branches of the hepatic artery, vein, bile duct and lymphatics at a portal area?

SLIDE 20 Liver vascular injected section A red dye has been injected into this tissue to highlight the blood vessels and sinusoids. Q 2. What does the position of sinusoids within the lobule indicate? SLIDE 21 Liver section stained for reticular fibres View under high magnification. The reticular fibres stain black. Note how they support the hepatocytes and the walls of the sinusoids. Q 3. What are reticular fibres composed of? SLIDE 19 Liver injected with colloidal carbon suspension Again view under high magnification. Note the cells have phagocytosed carbon particles. Q 4. What are these cells called and where are they located? 2 GALL BLADDER SLIDE 23 (guinea pig) Identify again the main 4 layers. Q 5. What is the lining epithelium type? Q 6. Is there a lamina muscularis present? Q 7. Would you expect to see any glands in the gall bladder?

PANCREAS SLIDE 24 - pancreas of rat View the section of pancreas and identify: lobules, islets of Langerhans, interlobular connective tissue with ducts and blood vessels. Under high power identify an acinus with its pyramidal cells. Look for centro-acinar cells (terminal duct cells). Q 8. Why does the basal part of these pyramidal cells (unlike the apical part) show basophilia? 3