Lab 1: Epithelium PDF

Laboratory session 1 Epithelial tissue & Glands  Objectives: 1. Recognize the types of epithelia and determine their function based on structure. 2. Identify the types of glands 3. Differentiate between serous and mucus secretory units. 4. Differentiate between exocrine and endocrine glands. 5. R...

Laboratory session 1 Epithelial tissue & Glands  Objectives: 1. Recognize the types of epithelia and determine their function based on structure. 2. Identify the types of glands 3. Differentiate between serous and mucus secretory units. 4. Differentiate between exocrine and endocrine glands. 5. Recognize the specialization of the apical cell surface. Introduction: In this laboratory session, you will identify different types of epithelia and correlate each type with its function and location. You will observe different cell shapes and organizations and the way they are interconnected by cell junctions. Note that the epithelium typically forms a barrier that covers the surfaces of the body and lines tubes and ducts that communicate with the surface. It also lines the body cavities, the heart and the blood and lymphatic vessels, and the digestive and genitourinary tracts. Staining: There are many different histology stains in use. Most histologic dyes are classified either as acidic or as basic dyes. For instance, in the hematoxylin-eosin stain (H&E), the hematoxylin-metal complex acts as a basic dye. The eosin acts as an acidic dye. Any structure that is stained with the basic dye is considered to be basophilic. A structure that is stained by an acidic dye is referred to as acidophilic. With eosin, acidophilic structures appear in various shades of pink. Hematoxylin and eosin stain (H&E) is known as “ routine stain” as it is used “routinely” with all tissue specimens in histology and pathology labs.  Types of Epithelia Lining epithelia Glandular epithelia  Types of Lining Epithelia Simple Stratified Squamous Cuboidal Columnar Simple Squamous Epithelium is a thin layer of connective tissue  Mesothelium-Mesentery Photomicrograph shows Simple squamous epithelium (mesothelium). This is not a section but a surface view of a part of the mesentery. Note the shape of cells (polygonal, flat with dark-stained nuclei).  Endothelium-Blood Vessel Photomicrographs show Simple squamous epithelium (endothelium): flat cells with flat nuclei that line the blood vessels.  Renal corpuscle a b Photomicrographs in low (a) and high magnification (b) show simple squamous epithelium lining parietal layer of Bowman's capsule of renal corpuscle found in the renal cortex (Hematoxylin stain) Simple Cuboidal Epithelium  Kidney Tubules b a Photomicrographs in different mag., show Simple cuboidal epithelium found in kidney tubules. Nucleus is usually round located in the center of the cells.  Thyroid Follicles a b Photomicrographs in low (a) and high magnification (b) show Simple cuboidal epithelium found in the thyroid gland. These follicular cells have an absorptive and secretory functions as well.  Primary Ovarian Follicles Medulla cortex a b C Photomicrographs in low (a) and high magnification (b, C) show simple cuboidal epithelium in primary ovarian follicle Simple Columnar Epithelium  Gallbladder Photomicrographs in low (a) and high magnification (b) show Simple columnar epithelium lining the wall of the gall bladder: Note the shape of the cells and the position of the nuclei (the nuclei maybe a located toward the b base or central)  Small intestine Photomicrographs in low (a) and high magnification (b) show Simple columnar epithelium lining a the small intestine. b  Colon Photomicrographs in low (a) and high magnification (b) show Simple columnar epithelium lining the colon a b  Oviduct Photomicrographs in low (a) and high magnification (b) show simple columnar epithelium found in a the oviduct lining. Oviduct is lined with both secretory and ciliated cells b Pseudostratified Columnar Epithelium  Upper respiratory tract a b Photomicrographs in low (a) and high magnification (b) show Pseudo-stratified columnar ciliated epithelium found in the respiratory mucosa. Note the presence of goblet cells represent unicellular glands with secretion (mucus), which stains poorly with H&E.  Epididymis Epididymis a b Photomicrographs in low (a) and high magnification (b) show Pseudo-stratified columnar epithelium with Stereocilia (modified microvilli) in epithelial lining of Epididymis Stratified Squamous Epithelium  Esophagus a Photomicrographs in low (a) and high magnification (b) show b Stratified squamous, non-keratinized epithelium in esophagus. Photomicrographs in low and high magnification show Stratified squamous, non-keratinized epithelium in esophageal mucosal lining. Note the shape of the surface layer of the cells.  Skin Photomicrograph shows Stratified squamous keratinized epithelium (Epidermis of skin).  Skin a b Photomicrographs in low (a) and high magnification (b) show Stratified squamous keratinized epithelium (Epidermis of skin) H&E. Note the thin eosinophilic layer of keratin on the surface. Stratified Cuboidal Epithelium  Sweat glands a b Photomicrographs in low (a) and high magnification (b) show Stratified cuboidal epithelium found in sweat glands. Transitional Epithelium Urinary Bladder – Transitional Epithelium (Empty) Urinary Bladder – Transitional Epithelium (Distended) Apical Surface Specializations  Cilia - Upper respiratory tract Photomicrographs in low (a) and high magnification (b) & (c) show Pseudo- stratified columnar b ciliated epithelium a found in the respiratory mucosa. c  Microvilli - Small Intestine a b Photomicrographs in low (a) and high magnification (b) show the microvilli of the simple columnar epithelium of the small intestine.  Stereocilia - Epididymis Epididymis Testis a b Photomicrographs in low (a) and high magnification (b) show Pseudo-stratified columnar epithelium with Stereocilia (modified microvilli) in epithelial lining of Epididymis Glandular epithelia  Glands Endocrine Exocrine Mucous Serous Mixed  Endocrine gland - Anterior Pituitary b a Photomicrographs in low (a) and high (b) magnification of anterior pituitary gland (endocrine). Note the groups of cells (cords) surrounding blood vessels in the darkly stained part of the gland. There is no duct system.  Endocrine gland – Thyroid gland a b Photomicrographs in low magnification (a) and high magnification (b) of the thyroid gland show the arrangement of its cells in follicles containing stored secretion.  Exocrine glands Salivary glands The parenchyma of the exocrine glands consists of the secretory units and duct system. Salivary glands are compound alveolar or tubulo-alveolar (tubulo-acinar) glands with mucous, serous or mixed acini forming the secretory units. Note that the duct system of these glands lined mainly with simple cuboidal epithelium. Recall that the stroma of the glands is made up of connective tissue.  Exocrine glands Serous Acini Photomicrographs show serous cells (exocrine) found in parotid gland.  Exocrine gland Mucous cells a b Photomicrographs in low (a) and high magnification (b) show mucous cells (exocrine) found in sublingual gland. D is duct  Exocrine Glands Seromucous Glands a b Photomicrographs in low (a) and high magnification (b) show mixed cells (exocrine) found in submandibular glands. Note the serous demilunes.