Glandular Tissue Curriculum : Phase 1/Semester2/TOB /Session 4 2017/2018 Lecturer : Dr. Rajaa Ali Al- Taee Msc. PhD. Histology G.mail: [email protected] Hammurabi Medical Collage / Babylon University Glandular Tissue References: • Histology Textbooks ‘Basic Histology’, Junqueira,13 th Edition chapter 1,2,3.pp:1-72 • ‘Colour Atlas of Histology’ Gartner and Hiatt 5 th Edition. • http://www.histologyguide.com/ Glandular Tissue Objectives of the lecture: 1. Define a gland as an epithelial cell or aggregate of cells specialised for secretion. 2. Classify glandular tissue, describing the meaning of the following terms: Exocrine or endocrine Merocrine, apocrine or holocrine. 3. Describe the above mechanisms of secretion. Glandular Tissue 4 . describe the mechanisms of endocytosis. 5. describe how endocytosis and secretion combine to give transepithelial transport. 6. explain the mechanism and importance of the glycosylation of newly synthesised proteins in the Golgi apparatus. 7. describe the role of secretions in cell functions (e.g. in communication). 8. describe simple mechanisms of control of secretion (e.g. nervous, endocrine). Glandular Tissue Glandular Epithelium: Glandular epithelium is more complex and varied than the epithelial cells which cover surfaces or line tubules or vessels. A gland is a single cell or a mass of epithelial cells adapted for secretion. Classification of Glands • By destination • By structure • By nature of the secretion • By the method of discharge By destination 1. Exocrine glands 2. Endocrine glands: • ductless glands • Secretion • Cells https://youtu.be/GUi84E6lUiY Adrenal gland Thyroid gland Exocrine glands secrete into ducts or directly onto a free surface. Their secretions include mucus, sweat, oil, ear wax and digestive enzymes. EXO = out side and crine = secret Examples include :- pancreas , stomach , sweat glands , salivary glands , mammary glands , sebaceous glands , etc . Endocrine glands - called “ductless glands” discharge their secretions into the intracellular fluid, where it diffuses into the blood stream. These secretions are hormones, or chemical messengers, which regulate many body functions. ee Examples include :- Pituitary gland ,thyroid gland,adrenal gland,parathyroideees exe 3. Mixed gland (an exocrine and endocrine gland) The Pancreas. Formation of glands from covering epithelia. During fetal development epithelial cells proliferate and penetrate the underlying connective tissue. They may-or may not-maintain a connection with the surface epithelium. When the connection is maintained, exocrine glands are formed; with the connection lost, endocrine glands are formed. Exocrine glands secrete to the body surface or gut via duct systems formed from the epithelial connection. Formation of glands from covering epithelia. The cells of endocrine glands, which secrete hormone) can be arranged in cords or in follicles with lumens for storing the secretory product. From either the cords or follicles of endocrine cells, the secretory product is released outside the cells and picked up by the blood vessels for distribution throughout the body. General structure of exocrine glands. • Exocrine glands by definition have ducts that lead to an organ or body surface. • Inside the gland the duct runs through connecting septa and branches repeatedly, until its smallest branches end in the secretory portions of the gland. Classification by Structure Secretory part: unicellular / multicellular acinar (alveolar) / tubular coiled / branched * Parotid gland: branched Duct system: 1. Simple gland (single duct) 2. Complex gland (branched ducts) Branching ducts: Main ↓ interlobular ↓ Intralobular ↓ Intercalary Salivary gland 1-Exocrine glands: Structural classification of exocrine glands: 1) unicellular glands 2) multicellular glands ↓ Goblet cell https://youtu.be/cdqLLa81-eE Salivary gland Multicelular gland: composed of : 1) An epithelial lined duct 2) A secretory unit called the acinus 3) Interstitial connective tissue Classification by method of secretion: Merocrine (exocytosis ) • secretion is released by exocytosis of secretory granules (pancreas, parotid gland, protein component of milk from mammary gland). Apocrine (pinch of ) • apical portion of cell along with secretory product is pinched off (lipid component of milk from the mammary gland). Holocrine (rupture) • entire cell is shed along with secretory product (sebaceous glands). https://youtu.be/E5aJTpiwakI • Classification by nature of secretion: Ex: Salivary glands • Classification by nature of secretion: mucous glands Secretion: contains mucopolysaccharides which collects in the apical part of cell. Cytoplasm: stain very lightly with H/E stain Nuclei: basally placed & flattened (mucoid pushes the nuclei). serous glands Secretion: thin, watery, rich in enzymes, protein in nature. Cytoplasm: granular stain darkly & rich in rER. Nuclei: rounded & basally placed. muco-serous or mixed gland Contain both serous & mucous secretory units. Sometimes serous cells form crescentic caps on mucous acini called as serous demilunes. Sero-mucous gland Mixed gland According to above 4 criteria of classifications ,classify parotid gland? Endocytosis • Engulfing • Opposite of exocytosis (merocrine secretion) • Endo- & Exo-cytosis (Transepithelial Transport) https://www.youtube.com/watch?v=sBCDxPvu4F0&feature=yo utu.be Transepithelial Transport • material endocytosed at one surface • transport vesicle shuttles across cytoplasm • material exocytosed at opposite surface Golgi Apparatus: Structure Stack of disc-shaped cisternae • One side of discs are flattened; other concave • Discs have swellings at their edges • Distal swellings pinch off as migratory Golgi Vacuoles https://youtu.be/3H5dSPQNlX8 Golgy apparatus Golgi Apparatus: Function • Packaging through condensation of contents • Transport • Adding sugars to proteins and lipids (Glycosylation) Golgi Product Destinations • Majority extruded in secretory vesicles • Some retained for use in the cells (e.g. lysosomes) • Some enters the plasma membrane (Glycocalyx) Glycosylation & Specificity • Branching sugars offer complex shapes for specific interactions in the glycocalyx • Destruction of this layer by enzymes alters many specificity based properties of cells: adhesion to substrates & neighboring cells mobility of cells communication with neighboring cells contact inhibition of movement and division Control of Secretion • Nervous • Endocrine control • Neuro-endocrine control • Negative feedback chemical mechanism Q:Give one or more examples of glands for each type of above controls? Thank you for listen.