ANAT2241 Covering and Lining Epithelia

From Embryology

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ANAT2241 This practical support page content is not part of the virtual science practical class and provides additional information for student self-directed learning purposes. All practical class pages are located on Moodle - 2019 ANAT2241

General Objective

Histology terminology cartoon.jpg

To learn the structure and function of covering and lining epithelia.


Associated lecture slides: Covering and Lining Epithelia (17.51 MB PDF) | 4 slides/page

Specific Objectives

  1. To identify covering and lining epithelia.
  2. To understand the terms endothelium, and mesothelium.
  3. To classify epithelia on the basis of cell morphology and cell arrangement (e.g. layering), noting the general absence of blood vessels in epithelia.
  4. To study the surface specializations of some epithelial cells: brush or striated border (microvilli), non-motile stereocilia and motile cilia and to recognise these specialisation in electron micrographs.

Learning Activities

To identify, draw and label the various types of epithelium (simple, stratified and pseudostratified) and to discuss some of the special functional features associated with their structure.


Virtual Slides: Covering and Lining Epithelia


Epithelium histology cartoon 01.jpg Epithelium histology cartoon 02.jpg
Epithelia cell shape Epithelia sectioning appearance

Histology

Epithelium forms continuous layers of cells that cover surfaces and line cavities of the body.

Simple epithelium

Vein histology 01.jpg

Venule with endothelium, a simple squamous epithelium lining.

Thyroid histology 002.jpg

Thyroid follicles, with a simple cuboidal epithelium surrounding each follicle.

Pseudostratified epithelium

Trachea histology 01.jpg

Trachea lined with a pseudostratified epithelium.

Testis histology 015.jpg

Testis ductus epididymidis lined with a pseudostratified epithelium.

Testis histology 023.jpg

Testis ductus epididymidis lined with a pseudostratified epithelium.

Stratified epithelium

Oesophagus stratified squamous non-keratinized epithelium.

Transitional epithelium

Bladder histology 01.jpg

Urinary bladder transitional epithelium

Ureter histology 001.jpg

Ureter transitional epithelium

Unlabeled Images


Electron Micrographs

Epithelia Specialisations - Cilia

Respiratory Epithelium - Cilia
Respiratory Epithelium EM1

Respiratory Epithelium EM01b.jpg

 ‎‎Mobile | Desktop | Original

EM Slides
Respiratory Epithelium EM2

Respiratory Epithelium EM02b.jpg

 ‎‎Mobile | Desktop | Original

EM Slides
Scanning Electron micrograph


RespiratoryEpitheliumSEM01.jpg

This respiratory epithelium surface view by scanning electron microscope (SEM) shows the 3 dimensional structure of the cilia protruding into the airspace.


These cilia move the overlying mucus that has trapped particles, bacteria and viruses, entering the respiratory tract as shown in the movie below.[1]

Cilium cartoon.jpg

Epithelia Specialisations - Villi

Gastrointestinal villi and crypts cartoon.jpg


Simple Squamous Epithelium

Endothelium - Simple Squamous
Blood capillary EM 02.jpg An electron micrograph of a capillary blood vessel with white blood cell located in the lumen.

The endothelium is an example of a simple squamous epithelium.

Note the nuclei of the endothelial cells bulging into the vessel lumen.


  • The white blood cell nucleus shape suggests that it is a Monocyte.

Scale bar 1 μm (Stain - Osmium)

Epithelia Specialisations - Junctions

Epithelial Junctions
Epithelial junctions EM01.jpg Junctional complex between two cells in the epithelium of the intestinal mucosa (rat), intestinal lumen is towards the top of image.

These 2 epithelial cells have a range of different junctional complexes along their lateral contact membranes. Half (hemi-) versions of these junctions also occur on the cell basal membrane where it attaches to the extracellular matrix (basal lamina, visible in EM), not shown in this image.

  • Tight junction - (zonula occludens), located nearest the lumen, extends from arrow 1 to arrow 2. The narrowing of the apparent intercellular "gap" (~90 A) is clearly visible, but the fusion line of the two apposed membranes cannot be clearly distin- guished at this magnification. Note that there is relatively little accumulation of dense cytoplasmic material along this part of the complex.
  • Adherens junction - (zonula adhaerens) intermediate junction extends from arrow 2 to arrow 3. A relatively wide intercellular space (~200 A) is maintained throughout the junction. Extensive condensation of cytoplasmic fibrils occurs as a fine feltwork along either side of the junction. This condensation is continuous with the terminal web (tw) into which the filamentous rootlets (r) of the microvilli penetrate. Plate-like densifications within the cytoplasmic feltwork can be seen along part of the junction, especially along the right side (pi).
  • Desmosome - marked by arrows 4 and 5. This element is characterized by a wide intercellular space (~240 A) bisected by an intermediate line (id). Bundles of cytoplasmic fibrils (fd), coarser (diameter ~80 A) and more distinct than those of the terminal web, converge into dense plates (pd) on each side of the desmo- some. These plates are separated from the inner leaflets of the cell membrane by a zone of low density. Similar fibrils (if) appear throughout the remainder of the field below the terminal web.


Between the intermediate junction and the desmosome, the two apposed cell membranes are separated by an irregular space of varying width and show membrane invaginations and associated vesicles (v). The trilaminar structure of the cell membrane (cm) shows clearly along the microvilli (my), (wherever the membrane is sectioned normally), and within the desmosome. It can also be made out, though less regularly, along the lateral cell margins (e.g., at unnumbered arrow).

Note that the luminal membrane is nearly symmetrical, the outer leaflet being only slightly thinner and less dense than the inner leaflet, whereas the lateral membrane is definitely asymmetrical. The total thickness of all three layers is about 110 A along the apical surface of the cell but measures only about 70 to 80 A along the lateral intercellular spaces. Note also the fluffy dense material (fro) (probably mucus) associated with the tips and sides of the microvilli.


Specimen fixed in 2 per cent (Stain - Osmium) in acetate-Veronal buffer (pH 7.6) ; and embedded in Epon. Pb(OH)2-stained section. X 96,000. (Stain - Osmium)

Epithelial Junction - Desmosome
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Course Links

Moodle - ANAT2241 - 2019

Histology Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | ANAT2241 Support | Histology | Histology Stains | Embryology Glossary


Common Histology Stains  
Histology Stains - Common Stains and Their Reactions
Stain
Nucleus
Cytoplasm
Collagen
RBCs
Other
Haematoxylin
blue
-
-
-
mucins - light blue
Eosin
-
pink
pale pink
bright red
colloid - pinkmuscle - red
Iron Haematoxylin
blue/black
-
-
-
Van Gieson
-
brown/yellow
red
yellow
muscle: yellow/browncartilage - pink
Verhoeff's Elastin
black
-
-
-
elastic fibres - black
Tartrazine
-
yellow
yellow
yellow
Silver Impregnation
-
-
grey/brown
-
reticular fibres - black
Methyl Green
dark green
light green
light green
green
Nuclear Fast Red
red
pink
pink
pink
Gomori's Trichrome
purple/red
purple
green
red
keratin - redmuscle - purple/red
Heidenhain's Azan
red
purple/red
deep blue
red
muscle - red
Osmium Tetroxide
-
-
brown
brown
myelin, lipids - black
Alcian Blue
-
-
-
-
mucins, - blue
Periodic acid-Schiff (PAS)
-
-
pink
-
mucins, glycogen, glycocalyx - magenta
Phosphotungstic Acid-Hematoxylin (PTAH)
blue
-
red
blue
muscle bands - blue
Masson's Trichrome
blue/black
red
green/blue
red
cartilage, mucins - blue or green; muscle - red
Luxol Fast Blue
-
-
-
variable
myelin - blue
Aldehyde Fuchsin
-
-
-
-
elastic fibres, mast cells - deep purple
Light Green
-
-
light green
-
Gallocyanin
dark blue
-
-
-
nucleic acids, Nissl granules - dark blue
Romanowsky (e.g. Leishman's)
blue
pink
acidophils - red, basophils - blue, azurophilic - purple
Aldehyde Pararosanilin elastic fibres - purple
Haematoxylin and Eosin
One of the most common staining techniques in pathology and histology. Acronym "H and E" stain. (H&E, HE).


Haematoxylin
  • Stains nuclei blue to dark-blue.
  • Stains the matrix of hyaline cartilage, myxomatous, and mucoid material pale blue.
  • Stains myelin weakly but is not noticeable if combined with eosin stain.
  • combined with Orange G (H & Or. G.) instead of eosin, specifically stains the granules of acidophilic cells of the adenohypophysis (anterior pituitary).
Eosin
  • Stains cytoplasm pink to red; red blood cells are also bright red.
  • Common counterstain to hematoxylin.
  • Stain intensity varies with the formula as well as the fixative.

Practical Support

Pages can be accessed from any internet connected computer.

ANAT2241 Support Links: The Virtual Microscope | Covering and Lining Epithelia | Glandular Epithelia | CT Components | CT Types | Bone, Bone Formation and Joints | Muscle | Nervous | Blood | Eye | Cardiovascular | Respiratory | Integumentary | Gastrointestinal | Gastrointestinal Organs | Lymphatic and Immune | Endocrine | Urinary | Female Reproductive | Male Reproductive | Histology Stains | Histology Drawings | Practicals Health and Safety 2013 | Moodle - 2019


ANAT2241 This practical support page content is not part of the science practical class and provides only background information for student self-directed learning purposes.


Cite this page: Hill, M.A. (2019, December 16) Embryology ANAT2241 Covering and Lining Epithelia. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/ANAT2241_Covering_and_Lining_Epithelia

What Links Here?
© Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
  1. Lechtreck KF, Delmotte P, Robinson ML, Sanderson MJ & Witman GB. (2008). Mutations in Hydin impair ciliary motility in mice. J. Cell Biol. , 180, 633-43. PMID: 18250199 DOI.