This shows you a section This shows you a section of a blood vessel of a blood vessel illustrating a simple illustrating a simple squamous epithelium (E). squamous epithelium (E). Note that the epithelium Note that the epithelium is so thin that the only is so thin that the only thing you can really see thing you can really see of these cells are their of these cells are their flattened nuclei, which flattened nuclei, which bulge into the lumen of bulge into the lumen of the blood vessel. (The the blood vessel. (The pinkish cells are red pinkish cells are red blood cells in the lumen blood cells in the lumen of the blood vessel)of the blood vessel)

Wheater, 1993

EPITHELIUMEPITHELIUM

Following are a series of images and Following are a series of images and descriptions to assist you in learning the descriptions to assist you in learning the characteristics of epithelia and its various characteristics of epithelia and its various subtypes.subtypes.

This shows a very thin, This shows a very thin, simple squamous simple squamous epithelium (mesothelium) epithelium (mesothelium) that has been spread that has been spread onto a slide and stained onto a slide and stained so that you are looking so that you are looking down onto the tissue. down onto the tissue. Note that the cells are Note that the cells are tightly packed together tightly packed together with little intracellular with little intracellular material (the dark lines material (the dark lines indicate the cell indicate the cell boundaries). The nuclei boundaries). The nuclei are indicated by “N”.are indicated by “N”.

Wheater, 1993

This shows a section of This shows a section of the small intestine the small intestine illustrating the simple illustrating the simple columnar epithelium with columnar epithelium with microvilli (arrow) on the microvilli (arrow) on the apical surface. Notice apical surface. Notice that the epithelium is a that the epithelium is a single layer of cells and single layer of cells and that these cells are taller that these cells are taller than they are wide. Note than they are wide. Note also the Goblet cells also the Goblet cells within the epithelium within the epithelium (GC).(GC).

GC

This shows the simple This shows the simple columnar ciliated columnar ciliated epithelium of the epithelium of the oviduct. Note that oviduct. Note that many of the cells many of the cells contain cilia (C) contain cilia (C) extending from their extending from their apical surfaces. Note apical surfaces. Note also the secretory also the secretory cells (SC) that are cells (SC) that are nonciliated.nonciliated.

C SC

This shows the This shows the pseudostratified columnar pseudostratified columnar epithelium of the epithelium of the epididymis. This epididymis. This epithelium appears to be epithelium appears to be stratified but in fact all of stratified but in fact all of the cells make contact the cells make contact with the basement with the basement membrane. Note that the membrane. Note that the epithelial cells contain epithelial cells contain stereocilia extending from stereocilia extending from their apical surfaces their apical surfaces (arrows).(arrows).

This shows a section of the This shows a section of the dermal portion of the dermal portion of the integument (skin). Seen in the integument (skin). Seen in the center of the field are a center of the field are a number of cross-sections of a number of cross-sections of a sweat gland. Notice that some sweat gland. Notice that some of the tube-like structures have of the tube-like structures have simple cuboidal epithelium simple cuboidal epithelium (black arrow). This is the (black arrow). This is the secretory portion of the sweat secretory portion of the sweat gland. Other parts of the gland gland. Other parts of the gland have stratified cuboidal have stratified cuboidal epithelium (green arrow). This epithelium (green arrow). This is the duct of the sweat gland.is the duct of the sweat gland.

This shows a section of This shows a section of thin skin illustrating a thin skin illustrating a stratified squamous stratified squamous epithelium that is epithelium that is keratinized (Ep). Notice keratinized (Ep). Notice that the outer portion of that the outer portion of the epithelium consists of the epithelium consists of extremely flattened extremely flattened (almost scaly in (almost scaly in appearance), dead cells appearance), dead cells (arrow). No noticeable (arrow). No noticeable organelles remain in organelles remain in these cells, hence this is these cells, hence this is termed a keratinized termed a keratinized epithelium.epithelium.

Ep

Connective Tissue

This shows the This shows the epithelium at the epithelium at the junction of the junction of the endocervix and endocervix and ectocervix. Note the ectocervix. Note the stratified squamous stratified squamous epithelium epithelium (nonkeratinized) on (nonkeratinized) on the left and the simple the left and the simple columnar epithelium columnar epithelium on the right.on the right.

Connective Tissue

Stratified Squamous Simple Columnar

This shows a section This shows a section of the nasal cavity of the nasal cavity illustrating the illustrating the pseudostratified pseudostratified columnar epithelium columnar epithelium with cilia. Goblet cells with cilia. Goblet cells (GC) can also be (GC) can also be distinguished here as distinguished here as the pale-staining the pale-staining epithelial cells.epithelial cells.

GC

Connective Tissue

This shows the This shows the pseudostratified pseudostratified columnar epithelium columnar epithelium of the trachea. Cilia of the trachea. Cilia extending from the extending from the apical surface of the apical surface of the epithelial cells can be epithelial cells can be seen much better seen much better than in the previous than in the previous micrograph.micrograph.

Connective Tissue

This shows a section This shows a section of the larynx of the larynx illustrating illustrating pseudostratified pseudostratified columnar epithelium columnar epithelium on the right and on the right and stratified squamous stratified squamous epithelium on the left. epithelium on the left. The cilia are difficult The cilia are difficult to discern at this to discern at this magnification.magnification.

Stratified Squamous Pseudostratified Columnar

This shows a section of This shows a section of the epithelium lining the the epithelium lining the cervix containing stratified cervix containing stratified columnar epithelium. columnar epithelium. Note that it is the shape Note that it is the shape of the cells adjacent to of the cells adjacent to the free surface by which the free surface by which the epithelium is named the epithelium is named (i.e. the surface cells here (i.e. the surface cells here are columnar in shape)are columnar in shape)

Connective Tissue

This illustrates the This illustrates the transitional epithelium transitional epithelium lining the urinary bladder. lining the urinary bladder. Note that the epithelium Note that the epithelium is stratified and that the is stratified and that the surface cells are of surface cells are of diverse shapes. This diverse shapes. This epithelium is distensible epithelium is distensible (can be stretched). The (can be stretched). The stretched cells tend to stretched cells tend to flatten while those not flatten while those not stretched tend to be stretched tend to be dome-shaped and bulge dome-shaped and bulge into the lumen (arrow).into the lumen (arrow).

Connective Tissue

This shows a section of This shows a section of the colon illustrating the colon illustrating simple tubular glands simple tubular glands (arrows) called the Crypts (arrows) called the Crypts of Lieberkuhn (or of Lieberkuhn (or intestinal crypts). Note intestinal crypts). Note that these appear in that these appear in section as relatively section as relatively simple invaginations of simple invaginations of the surface epithelium.the surface epithelium.

Connective TissueSmoothMuscle

This shows a section of the This shows a section of the duodenum illustrating finger-duodenum illustrating finger-like folds termed villi that are like folds termed villi that are lined with simple columnar lined with simple columnar epithelium. The epithelium epithelium. The epithelium contains Goblet Cells (GC; the contains Goblet Cells (GC; the almost empty-appearing cells almost empty-appearing cells within the epithelium). The within the epithelium). The epithelium also contains epithelium also contains Crypts of Lieberkuhn as seen Crypts of Lieberkuhn as seen in the previous slide. Below in the previous slide. Below the Crypts of Lieberkuhn are the Crypts of Lieberkuhn are other glands that extend into other glands that extend into the connective tissue termed the connective tissue termed Brunner’s Glands (BG). These Brunner’s Glands (BG). These are compound tubular glands. are compound tubular glands.

BG

GC

Villus

This shows a section of the This shows a section of the submandibular gland submandibular gland illustrating the compound illustrating the compound acinar type of gland. Note the acinar type of gland. Note the presence of mucous (black presence of mucous (black arrow) and serous (green arrow) and serous (green arrow) cells. The mucous cells arrow) cells. The mucous cells typically appear empty with typically appear empty with routine tissue processing routine tissue processing because the secretory because the secretory contents are lost during the contents are lost during the preparation of the tissue. Also preparation of the tissue. Also notice the ducts lined with notice the ducts lined with simple columnar type of simple columnar type of epithelium (D).epithelium (D).

D

This shows a section This shows a section of a mammary gland of a mammary gland illustrating a illustrating a compound acinar compound acinar (alveolar) type of (alveolar) type of gland. Note the gland. Note the abundant cross-abundant cross-sections of glandular sections of glandular material and the large material and the large duct (D).duct (D).

D

This illustrates the This illustrates the secretory cells of the secretory cells of the mammary gland at mammary gland at higher magnification. higher magnification. Note that the Note that the secretory portion of secretory portion of the gland is lined by the gland is lined by simple cuboidal simple cuboidal epithelium (SC).epithelium (SC).

SC

This shows a scanning This shows a scanning electron micrograph of electron micrograph of the epithelium of the the epithelium of the oviduct (you are oviduct (you are essentially looking onto essentially looking onto the surface of the the surface of the epithelium from within the epithelium from within the oviduct). Some of the oviduct). Some of the epithelial cells have cilia epithelial cells have cilia (C) while others have (C) while others have microvilli (M).microvilli (M).

C

M

This shows a This shows a transmission electron transmission electron micrograph of the oviduct micrograph of the oviduct epithelium illustrating epithelium illustrating cells that have cilia (C) cells that have cilia (C) and others that have and others that have microvilli (M) on their microvilli (M) on their surface. Note the surface. Note the difference in size and difference in size and composition of these composition of these structures. structures.

M C

This shows a higher This shows a higher magnification magnification transmission electron transmission electron micrograph of cilia. micrograph of cilia. Note in the cross-Note in the cross-sections of cilia (*) the sections of cilia (*) the arrangement of the arrangement of the microtubules within microtubules within the cilium.the cilium.

*

This shows a This shows a transmission electron transmission electron micrograph of cilia in micrograph of cilia in cross-section. Note cross-section. Note the characteristic the characteristic arrangement of arrangement of microtubules in the microtubules in the cilia (i.e. two central cilia (i.e. two central microtubules microtubules surrounded by 9 other surrounded by 9 other pairs).pairs).

Cilium

Microtubules

This shows a transmission This shows a transmission electron micrograph of the electron micrograph of the epithelium of the cervix. Seen epithelium of the cervix. Seen are the apical portions of two are the apical portions of two epithelial cells. Note that the epithelial cells. Note that the cell to the left has microvilli cell to the left has microvilli and cilia on its surface. Two and cilia on its surface. Two basal bodies (BB) are basal bodies (BB) are associated with the cilia in the associated with the cilia in the cell to the left. Also notice the cell to the left. Also notice the junctional complex between junctional complex between the two cells. What other the two cells. What other structures can you identify structures can you identify here?here?

BB

Zonula occludens

Zonula adeherens

Macula adherens

This shows another This shows another transmission electron transmission electron micrograph of the micrograph of the cervix epithelium. cervix epithelium. Notice the junctional Notice the junctional complex between the complex between the two epithelial cells.two epithelial cells.

This transmission This transmission electron micrograph electron micrograph shows the basal shows the basal portion of an portion of an epithelium. Notice epithelium. Notice the basal lamina (BL) the basal lamina (BL) separating the separating the epithelium from the epithelium from the underlying connective underlying connective tissue (CT).tissue (CT).CT

BLGlycogen