CHAPTER 05 Histology: EPITHELIUM

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1 BIO 211: ANATOMY & PHYSIOLOGY I 1 CHAPTER 05 Histology: EPITHELIUM Part 01: Brief Introduction Part 02: Survey of Types Dr. Lawrence G. G. Altman Some illustrations are courtesy of McGraw-Hill. Some illustrations are courtesy of McGraw-Hill.

2 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)

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4 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

5 EPITHELIA 5 MANY FUNCTIONS 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.

6 EPITHELIAL FEATURES 6 TIGHTLY PACKED: Little extracellular space EXISTS as SHEETS: Cells attached by tight junction points and desmosomes (binding bodies). OPEN SPACE TIGHT JUNCTION impermeable Surface view of simple squamous epithelium stripped from underlying connective tissue in the peritoneal cavity. CELL 1 CELL 2 DESMOSOME anchoring junction

7 EPITHELIAL FEATURES 7 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 BRUSH BORDER N N N TEM: 3 Cells shown ^

8 8 CORE 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)

9 EPITHELIAL FEATURES 9 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. BASEMENT MEMBRANE

10 EPITHELIAL FEATURES 10 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 RETICULAR LAMINA Below the BASAL LAMINA Extracellular network of collagen fibers BASAL LAMINA + RETICULAR LAMINA = BASEMENT MEMBRANE

11 EPITHELIAL FEATURES 11 SEM: BASEMENT MEMBRANE EPITHELIAL CELLS BM collagen fibers BASAL LAMINA RETICULAR LAMINA

12 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

13 EPITHELIA: SURVEY of TYPES CLASSIFICATION of EPITHELIA cells 13 Number of Layers SIMPLE epithelium: 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

14 EPITHELIA: SURVEY of TYPES CLASSIFICATION of EPITHELIA SIMPLE epithelium: Little protection; other functions 14 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

15 PSEUDOSTRATIFIED PSEUDO = FALSE or FAKE EPITHELIA: SURVEY of TYPES CLASSIFICATION of EPITHELIA SIMPLE epithelium: Little protection; other functions 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 EPITHELIA: SURVEY of TYPES CLASSIFICATION of EPITHELIA SIMPLE epithelium: Little protection; other functions 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

17 TYPES: SIMPLE SQUAMOUS SIMPLE CUBOIDAL SIMPLE COLUMNAR EPITHELIA: SURVEY of TYPES CLASSIFICATION of EPITHELIA SIMPLE epithelium: Little protection; other functions 17 usually quite permeable Also see: DISTAL TUBULE (KIDNEY) Lab Atlas: PLATE 9- F KIDNEY: ABSORPTION (Many MICROVILLI)

18 EPITHELIA: SURVEY of TYPES CLASSIFICATION of EPITHELIA SIMPLE epithelium: Little protection; other functions 18 NO CILIA EXAMPLE: DIGESTIVE TRACT (STOMACH to ANUS) CILIATED EXAMPLE: UTERINE TUBES BOTH TYPES: GOBLET CELLS MAY BE PRESENT (MUCOUS PRODUCTION)

19 19 EPITHELIA: SURVEY of TYPES CLASSIFICATION of EPITHELIA SIMPLE epithelium: Little protection; other functions SIMPLE SIMPLE SIMPLE

20 EPITHELIA: SURVEY of TYPES CLASSIFICATION of EPITHELIA SIMPLE epithelium Little protection; other functions TYPES 20 SIMPLE COLUMNAR EPITHELIUM cilia non- ciliated (mucous - producing) OVIDUCT PANCREATIC DUCT PHOTO EQUIVALENT: 10a also in STOMACH

21 EPITHELIA: SURVEY of TYPES CLASSIFICATION of EPITHELIA SIMPLE epithelium: Little protection; other functions TYPES 21 MAY HAVE CILIA EXAMPLE: RESPIRATORY TRACT REALLY SIMPLE EPITHELIUM!!!! why??? - ALL CELLS REST ON BM - SOME DO NOT REACH APICAL SERVICE - NUCLEI AT DIFFERENT LEVELS GIVING FALSE APPEARANCE of BEING STRATIFIED

22 EPITHELIA: SURVEY of TYPES CLASSIFICATION of EPITHELIA SIMPLE epithelium: Little protection; other functions TYPES 22 MONKEY TRACHEA PICTURE EQUIVALENT: LAB ATLAS: Human Trachea PLATE 10- B

23 EPITHELIA: SURVEY of TYPES CLASSIFICATION of EPITHELIA SIMPLE epithelium: Little protection; other functions 23 PSEUDOSTRATIFIED COLUMNAR EPITHELIUM (ciliated) GOBLET CELLS SEM of CILIA in TRACHEA CILIA

24 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

25 STRATIFIED SQUAMOUS EPITHELIUM 25 Keratinized Cells ORAL CAVITY PICTURE EQUIVALENT: Atlas: Fig. 10- D HUMAN SKIN (keratinized) PICTURE EQIVALENT: Lab Atlas: Fig. 11- A

26 STRATIFIED COLUMNAR EPITHELIUM 26 VERY RARE! - URETHRA of MALE - some LARGE DUCTS of GLANDS REMINDER: STRATIFIED EPITHELIUM NAMED ON BASIS of APICAL LAYER

27 STRATIFIED CUBOIDAL EPITHELIUM 27 ALSO VERY RARE! - 2 to 3 CELLS DEEP - LARGEST DUCTS of: SWEAT GLANDS MAMMARY GLANDS SALIVARY GLANDS SURROUNDING EGGS

28 TRANSITIONAL EPITHELIUM 28 UMBRELLA CELLS CUBOIDAL COLUMNAR RELAXED DISTENDED THINK URINARY BLADDER!

29 TRANSITIONAL EPITHELIUM 29 PICTURE EQUIVALENT: ATLAS: Fig. 11- B (RELAXED) Fig. 11- C (DISTENDED) Bladder

30 TRANSITIONAL EPITHELIUM 30 LAST SLIDE