BIO 211: ANATOMY & PHYSIOLOGY I 1 CHAPTER 05 Histology: EPITHELIUM Part 01: Brief Introduction Part 02: Survey of Types Dr. Lawrence G. G. Altman www.lawrencegaltman.com Some illustrations are courtesy of McGraw-Hill. Some illustrations are courtesy of McGraw-Hill. 2 TISSUES TYPES Group of cells closely associated in: a) structure (similar) b) function (common or related) HISTOLOGY = the study of tissues In general, FOUR (4) MAJOR TYPES: 1. EPITHELIAL (this week's topic) 2. CONNECTIVE (supportive) 3. MUSCLE (movement) 4. NERVOUS (control)
3 EPITHELIA 4 LOCATIONS: COVERING or LINING EPITHELIUM ofa) FREE SURFACES (i.e. SKIN) b) LINING of OPEN CAVITIES (i.e. DIGESTIVE, RESPIRATORY SYSTEMS) c) LINING of CLOSED CAVITIES (i.e. VENTRAL BODY CAVITY) d) LINING of BLOOD VESSELS and HEART May also serve as a GLANDULAR EPITHELIUM To be discussed
EPITHELIA MANY FUNCTIONS 5 PROTECTION ABSORPTION FILTRATION SECRETION Bacterial Infections, Injury etc Example: lining of digestive tract Example: Renal (renal = kidney) Example: glandular epithelium or any COMBINATION of the above. EPITHELIAL FEATURES TIGHTLY PACKED: Little extracellular space EXISTS as SHEETS: Cells attached by tight junction points and desmosomes (binding bodies). OPEN SPACE TIGHT JUNCTION impermeable 6 Surface view of simple squamous epithelium stripped from underlying connective tissue in the peritoneal cavity. CELL 1 CELL 2 DESMOSOME anchoring junction
EPITHELIAL FEATURES POLARITY APICAL surface: often contain MICROVILLI: highly folded EXTENSIONS of the PLASMA MEMBRANE MICROVILLI from SMALL INTESTINAL EPITHELIUM Increases ABSORBTION area Note: brush border = many microvilli 7 BRUSH BORDER N N N TEM: 3 Cells shown ^ 8 CORE 9 + 2 Microtubule doublets CILIA BASAL BODY (centriole) 9 Microtubule triplets FLAGELLA: simply longer projections from BASAL BODY; cell propels itself (cilia move substances over a surface)
EPITHELIAL FEATURES POLARITY BASAL surface: bottom - most layer of epithelial tissue is always attached to a BASEMENT MEMBRANE. EPITHELIUM Acts as a barrier between the EPITHELIUM and the underlying CONNECTIVE TISSUE. 9 BASEMENT MEMBRANE EPITHELIAL FEATURES POLARITY BASAL surface: The BASEMENT MEMBRANE is composed of two layers. BASAL LAMINA Closest to the epithelium Actually secreted by the epithelium. - thin, non - cellular adhesive layer - selective filter of materials from blood - template for wound repair 10 RETICULAR LAMINA Below the BASAL LAMINA Extracellular network of collagen fibers BASAL LAMINA + RETICULAR LAMINA = BASEMENT MEMBRANE
EPITHELIAL FEATURES SEM: BASEMENT MEMBRANE EPITHELIAL CELLS 11 BM collagen fibers BASAL LAMINA RETICULAR LAMINA EPITHELIAL FEATURES 12 AVASCULARITY REGENERATION - No blood vessels - Nutrients etc. via DIFFUSION (upward) - IS innervated - High MITOTIC INDEX (turnover) END of PART 01: Brief Introduction NEXT: Part 02: Survey of Types
cells 13 Number of Layers one layer of cells STRATIFIED epithelium: multiple layers of cells BM BM STRATIFIED EPITHELIUM: layers may have DIFFERENT SHAPES but nomenclature based upon the CELL SHAPE of the free (APICAL) surface. SHAPE of cells SQUAMOUS flattened CUBOIDAL height = width COLUMNAR height > width TYPES SIMPLE SQUAMOUS SIMPLE CUBOIDAL SIMPLE COLUMNAR PSEUDOSTRATIFIED PSEUDO = FALSE OR FAKE In other words, ALL of the shapes May exist in the one cell layer arrangement! Looks stratified but really NOT! ONE LAYER of cells but different heights 14
PSEUDOSTRATIFIED PSEUDO = FALSE or FAKE TYPES Types SIMPLE SQUAMOUS SIMPLE CUBOIDAL SIMPLE COLUMNAR PSEUDOSTRATIFIED PSEUDO = FALSE or FAKE 15 SIMPLE SQUAMOUS EPITHELIUM SINGLE LAYER FLATTENED usually quite permeable LUNGS: DIFFUSION KIDNEY: FILTRATION In certain locations- special names: ENDOTHELIUM: LINING of BLOOD VESSELS/CAPILLARIES MESOTHELIUM: SEROSAL MEMBRANES 16 SIMPLE SQUAMOUS EPITHELIUM Endothelium (RBCs in a CAPILLARY) Picture Equivalent LAB ATLAS PLATES 9- C and 9- E Also see: ALVEOLUS (LUNG) LAB ATLAS PLATE 85- D BOWMAN'S CAPSULE (KIDNEY) LAB ATLAS PLATE 97- D
TYPES: SIMPLE SQUAMOUS SIMPLE CUBOIDAL SIMPLE COLUMNAR 17 usually quite permeable Also see: DISTAL TUBULE (KIDNEY) Lab Atlas: PLATE 9- F KIDNEY: ABSORPTION (Many MICROVILLI) SIMPLE epithelium: NO CILIA EXAMPLE: DIGESTIVE TRACT (STOMACH to ANUS) 18 CILIATED EXAMPLE: UTERINE TUBES BOTH TYPES: GOBLET CELLS MAY BE PRESENT (MUCOUS PRODUCTION)
19 SIMPLE SIMPLE SIMPLE SIMPLE epithelium TYPES 20 SIMPLE COLUMNAR EPITHELIUM cilia non- ciliated (mucous - producing) OVIDUCT PANCREATIC DUCT PHOTO EQUIVALENT: 10a also in STOMACH
TYPES 21 MAY HAVE CILIA EXAMPLE: RESPIRATORY TRACT REALLY SIMPLE EPITHELIUM!!!! why??? - ALL CELLS REST ON BM - SOME DO NOT REACH APICAL SURFACE - NUCLEI AT DIFFERENT LEVELS GIVING FALSE APPEARANCE of BEING STRATIFIED TYPES 22 MONKEY TRACHEA PICTURE EQUIVALENT: LAB ATLAS: Human Trachea PLATE 10- B
23 PSEUDOSTRATIFIED COLUMNAR EPITHELIUM (ciliated) GOBLET CELLS SEM of CILIA in TRACHEA CILIA STRATIFIED SQUAMOUS EPITHELIUM 24 MOST COMMON TYPE Of STRATIFIED EPITHELIUM - PROTECTION vs. ABRASION - HIGH MITOTIC INDEX - CELLS SHED FROM APICAL REGION STRATIFIED epithelium: Different layers may have different shapes BUT nomenclature: BASED ON CELL SHAPE of the free (APICAL) surface BASAL LAYERS: - USUALLY NOT SQUAMOUS - SITE OF NEW CELL GENERATION APICAL SURFACE MAY POSSESS KERATIN, A WATER INSOLUBLE PROTEIN
STRATIFIED SQUAMOUS EPITHELIUM 25 Keratinized Cells ORAL CAVITY PICTURE EQUIVALENT: Atlas: Fig. 10- D HUMAN SKIN (keratinized) PICTURE EQIVALENT: Lab Atlas: Fig. 11- A STRATIFIED COLUMNAR EPITHELIUM VERY RARE! - URETHRA of MALE - some LARGE DUCTS of GLANDS 26 REMINDER: STRATIFIED EPITHELIUM NAMED ON BASIS of APICAL LAYER
STRATIFIED CUBOIDAL EPITHELIUM 27 ALSO VERY RARE! - 2 to 3 CELLS DEEP - LARGEST DUCTS of: SWEAT GLANDS MAMMARY GLANDS SALIVARY GLANDS SURROUNDING EGGS TRANSITIONAL EPITHELIUM 28 UMBRELLA CELLS CUBOIDAL COLUMNAR RELAXED DISTENDED THINK URINARY BLADDER!
TRANSITIONAL EPITHELIUM 29 PICTURE EQUIVALENT: ATLAS: Fig. 11- B (RELAXED) Fig. 11- C (DISTENDED) Bladder TRANSITIONAL EPITHELIUM 30 LAST SLIDE