Histology Lecture 15 (Overview of Digestive glands) 2024 PDF

Faculty of Medicine Histology & Cell Biology Overview of Digestive Glands By Dr. Amany Abd El Fattah Mohamed Lecturer of Medical Histology & Cell Biology  Learning outcomes ❑ By the end of the lecture, the studen...

Faculty of Medicine Histology & Cell Biology Overview of Digestive Glands By Dr. Amany Abd El Fattah Mohamed Lecturer of Medical Histology & Cell Biology  Learning outcomes ❑ By the end of the lecture, the students will be able to: 1. Enumerate types of digestive glands. 2. Describe the general structure of digestive glands. 3. Describe the structure of salivary glands. 4. Mention types of salivary glands & differences between. 5. Describe the structure of pancreas. 6. Describe the structure of liver.  Case Scenario 40 years old female came complaining of polyuria, polydipsia, polyphagia, weight loss and easy fatigability since 6 months. She is a fast-food lover and usually eats junk food. Her father is diabetic. Measuring her blood glucose level, it was 425 mg/dl. Q: What is the provisional diagnosis of this case?  Learning outcome 1 Enumerate types of digestive glands.  Digestive Glands Salivary glands Pancreas Liver  Learning outcome 2 Describe the general structure of digestive glands.  Digestive Glands Stroma Parenchyma “Supporting C.T. part” “Functioning part” Capsule Secretory units (surround the gland) (acini) Trabeculae (divide the gland) Duct system  Learning outcome 3 Describe the structure of salivary glands  Salivary Glands Exocrine glands which secrete saliva. It is compound branched tubulo-alveolar glands Types Parotid Submandibular Sublingual 1. Capsule→ dense C.T. surrounds the gland. 2.Trabeculae→ C.T. septa arise from the capsule, divide the gland into lobes & lobules 1. Salivary acini→ a group of secretory cells surrounding a central lumen. 2. Duct system→ series of ducts that convey saliva to oral cavity.  1. Salivary Acini 3 types: Mucous Serous Muco-serous (mixed)  1. Mucous 2. Serous Pale-stained rounded acinus, with Dark –stained rounded acinus, with narrow wide lumen. lumen. The secretory cells have The secretory cells are protein- ✓Basal flat nuclei synthesizing cells having: ✓Pale foamy ✓ Rounded central nuclei. cytoplasm. ✓ Basophilic cytoplasm. ✓ Apical acidophilic granules. 3. Mixed acini (muco-serous). A mucous acinus capped by a group of serous cells. Mucous Serous Mixed acini  2. Duct System Series of ducts that convey saliva from acini to mouth cavity. Start by small (intercalated duct) arise from acinus (lined by flat epithelial cells). End by main duct open into mouth (lined by stratified squamous non keratinized epithelium)  Learning outcome 4 Mention types of salivary glands & differences between them.  Parotid Submandibular Sublingual Type Pure serous Mixed Mixed Stroma Thick Thick Thin Acini Pure serous. -Mainly serous with Mainly mucous with some mucous and some serous and mixed ones. mixed ones.  Learning outcome 5 Describe the structure of pancreas  Pancreas Mixed gland (has exocrine and endocrine functions, performed by two separate parenchyma, pancreatic acini & Islets of Acini Langerhans). It is compound branched tubulo-alveolar gland. Islets of Langerhans  Structure of pancreas Exocrine part Endocrine part Pancreatic acini Islets of Langerhans Ducts. Secret insulin, Produce pancreatic glucagon and other juice (enzymes-HCO3) hormones ❑ Stroma: ❑Parenchyma: Delicate, loose C.T. 1. Pancreatic acini. 1. Capsule. 2. Duct system. 2. Trabeculae.  1- Pancreatic Acini ❖Irregular serous acinus with very narrow lumen. ❖Lining cells are similar to serous acinus. The secretory cells have: ✓ Rounded central nuclei. ✓ Basophilic cytoplasm. ✓ Apical acidophilic granules. Pancreatic acini  2. Duct System Series of ducts that convey pancreatic juice from acini to duodenum. Start by small (intercalated duct) arise from acinus (lined by flat centroacinar cells). End by the main pancreatic duct open into 2nd part of duodenum (lined by simple columnar epithelium) ❖Non-capsulated pale masses of endocrine cells, scattered between dark pancreatic acini. ❖Structure: Anastomosing cords of epithelial cells separated by fenestrated blood capillaries. Types of islet cells A (α) Glucagon B (β) Insulin D (δ) Somatostatin F (PP) Pancreatic polypeptide  Learning outcome 6 Describe the structure of Liver  Liver The largest gland in the body. Mixed gland (has exocrine and endocrine functions, performed by the same parenchyma, hepatocytes “liver cells”). It is compound branched tubular gland. 1. Capsule of Glisson→ dense Formed of hepatocytes, C.T. surrounds the liver, arranged in specific covered with peritoneum. manner forming the 2.Trabeculae→ C.T. septa arise “Classic hepatic lobule”. from the capsule, divide the gland into lobes & lobules  The Classical Hepatic lobule It is a hexagonal mass of hepatocytes which drains its blood into a central vein running in its longitudinal axis.  Blood sinusoids Structure: Bile canaliculi 1. Hepatocytes. 2. Blood sinusoids. 3. Bile canaliculi  1. Hepatocytes 80% of liver cells (main cell). Form irregular plates radiating from the central vein and extends towards the periphery. Each plate is formed of two or more rows of cells enclosing bile canaliculus. Plates are separated by blood sinusoids.  Blood sinusoids 2. Blood sinusoids Irregular blood channels between plates of hepatocytes. Lined by endothelial cells and Von Kupffer cells (liver macrophages). Drain blood into central vein.  3. Bile canaliculi Narrow anastomosing channels pass within the plates. Lined by hepatocytes. Drain bile formed by the hepatocytes into bile duct in portal tract. Bile canaliculi  The Portal Tract A triangular mass of connective tissue (C.T) at some angles of the hepatic lobules. Contains portal triad: 1. A venule branch of the portal vein (blood rich in nutrients but low in O2) 2. An arteriole branch of the hepatic artery (supplies O2). 3. Bile ductule (branches of the bile duct).  Case Discussion A case of Diabetes mellitus. It is due to insulin deficiency due to failure of secretion by b cells of islets of Langerhans. It is treated by insulin injection or oral hypoglycemics.  Summary and wrap up Digestive glands include salivary gland, pancreas & liver. Salivary glands are exocrine glands producing saliva. It is formed secretory acini & ducts. Pancreas is mixed gland. It has exocrine parenchyma “pancreatic acini & ducts” that produce pancreatic juice & endocrine parenchyma “islets of Langerhans” that produce hormones. Liver is mixed gland that has exocrine & endocrine functions performed by hepatocytes.