Epithelium Stuff

Congratulations on surviving your first quiz! Now to jump into the magical world of epithelium. This section can seem very intimidating at first, because we cover so much material. It's one of the heaviest weeks there are in the lab. Go to open lab, look at google images of stuff you're studying, ask questions, and practice! Remember that form follows function. 

Instead of going over everything you need to know this week, this post just highlights some things that are commonly missed and/or crop up often in subsequent quizzes. Pro tip: make sure you know all the layers of the things that have layers, because those are favorites for quizzes.

Don't try to cram this week. You don't need that kind of stress in your life. 

 First, I just want to review the kidney, especially since if you don't learn it well now, it will come back to bite you.

Can you see where the cortex ends and the medulla begins? What 3 structures are found in the cortex?

Make sure that you can easily identify the cortex and the medulla and that you can name each of the specific structures found there.


The medulla in particular often poses a problem for students, especially in deciding which structures are collecting ducts and which are the thick portion of the loop of Henle/end of DCT. Both have simple cuboidal epithelium, but remember that only the collecting ducts have tight junctions. Collecting ducts are also typically larger. Practice identifying tight junctions!

See the tight junctions? Also, this particular slide has several good examples of peritubular capillaries.

 Also, remember that the only difference between the thin portion of the loop of Henle and peritubular capillaries on a slide is the presence of blood cells in the lumen.

Just another pic for practice - see if you can identify all 4 medullary structures below.

I also thought it might be helpful to compare some of the tissues we talked about with epithelium that look similar:

Trachea vs. Bronchus                                            
- remember that the trachea will have c-shaped cartilage rings while the bronchus will have cartilage that looks 'broken' - it will only have small pieces.

- also, the trachea has large subtracheal glands that are sandwiched between the cartilage and epithelium, but the bronchus does not.

- both have ciliated pseudostratified columnar epithelium
 

Bronchus

Trachea

Epidermis vs. Esophagus vs. Vagina

- all three of these have stratified squamous epithelium, so telling them apart can be tricky

- the epidermis is the only one of the three that will have it's darkest layer in the middle. Notice how in both the vagina and the esophagus, the darkest layer is the deepest layer. The stratum granulosum is the darkest layer of the epidermis and is located right in the middle of all the layers (remember "can loud girls sing bass").

- the esophagus is unique because it is the only one of the three that has glands in the submucosa beneath the epithelium. If we ever show you the esophagus we will include the subesophageal glands with the epithelium.

- the vagina has two unique features: it is the only one of the three with glands in the epithelium itself, and it is the only one with cells that store large amounts of glycogen. Note the lighter staining and slight bulging of the more superficial cells - this is due to abundant glycogen storage.

Epidermis

Esophagus
(Note the subesophageal gland)

Vagina
(That little round guy is a vaginal gland within the epithelium)

Ureter vs. Urethra

- these two are extremely similar: they both have transitional epithelium and both perform almost the same function. The only difference is the shape of the lumen.

- the ureter has a Greek cross-shaped lumen; usually much smaller and less branched

- the urethra is larger and therefore has a larger lumen that tends to have more branches

Urethra

Ureter

Stuff from this section that won't be u-finds:
- Bronchus
- Bronchiole - Partially ciliated simple cuboidal epithelium -Cornea Stuff from this section that you won't need to know for this week (but will in the future): - Tunica intima, tunica media and tunica adventitia (part of Endothelium)
- Hair cells (in the cochlea) -Parietal cells and chief cells (in the stomach) Stuff from this section you don't need to know for lab:
- The whole page 7 is helpful to know, but you won't be quizzed on it directly.

Epithelium Key Terms

Key: Know the anatomical and histological names (including modifications) for the following bolded structures; assume that you will be required to find the structures indicated by * on your own slides.

***This list is not guaranteed to be exhaustive, and only includes terms from this unit. While we will not focus on quiz information from previous weeks, knowledge of previous material may be useful***

Focus on epithelium histology, but keep in mind all of the following terms. Review epithelial modifications as outlined in your lab manual.

Nomenclature

Be able to differentiate epithelium based on the following criteria

·       Quantity of layers (simple, pseudostratified, stratified)

·       Shape of the cell (squamous, cuboidal, columnar, transitional)

Be able to recognize and differentiate among the following free surface modifications and know where you would find them.

·       Microvilli

·       Stereocilia

·       Cilia

·       Specialized Secreted Products (keratin, enamel)

·       Glycocalyx (not included when naming cells)

Renal Epithelium

Cortex

·       Proximal convoluted tubule (PCT)*

·       Distal convoluted tubule (DCT)*

·       Glomerulus*

·       Parietal layer of Bowman’s capsule*

·       Visceral layer of Bowman’s capsule*

·       Macula densa*

Medulla

·       Collecting duct*

·       Thin loop of Henle*

·       Peritubular capillaries*

·       Thick loop of Henle*

Endothelium

Vein and Artery

·       Endothelium*

·       Tunica intima

·       Tunica media

·       Tunica adventitia

Respiratory Tract

Trachea

·       Tracheal Epithelium*

·       Hyaline cartilage (c-rings)

·       Subtracheal gland

Bronchus

·       Bronchus epithelium*

·       Hyaline cartilage (cartilaginous plates)

Bronchiole and Terminal Bronchiole

·       Bronchiole epithelium*

·       Terminal bronchiole epithelium*

·       Respiratory bronchiole

Lung

·       Alveoli*

Skin

Know the following layers and something unique to each layer

·       Skin*

·       Stratum corneum*

·       Stratum lucidum*

·       Stratum granulosum*

·       Stratum spinosum*

·       Tonofibrils*

·       Stratum germinatimum (basale)*

·       Dermal Papillae*

Cornea

·       Outer epithelial layer

·       Connective tissue layer

·       Inner epithelial layer

Cochlea

·       Vestibular membrane*

·       Tectorial membrane*

·       Basilar membrane*

·       Hair cells

·       Scala tympani

·       Scala media (cochlear duct)

·       Scala vestibuli

GI Tract

Esophagus

·       Esophageal epithelium*

·       Subesophageal glands

·       Muscularis externa layers

Stomach

·       Stomach epithelium*

·       Parietal cells

·       Chief cells

Small Intestine

·       Mucosa

·       Submucosa

·       Muscularis externa

·       Small intestine epithelium*

·       Goblet cells

Appendix

·       Appendix epithelium*

·       Lymph Nodule

·       Goblet cell

·       Trash in the lumen

Large Intestine

·       Muscularis externa

·       Submucosa

·       Mucosa

·       Large intestine epithelium*

·       Goblet cells

Female Reproductive Tract

Oviduct

·       Lamina propria

·       Oviduct epithelium*

Uterus

·       Uterus epithelium*

·       Stratum functionalis

·       Stratum basalis

·       Myometrium

·       Uterine gland

Vagina

·       Vaginal epithelium*

·       Lamina propria

Male Reproductive Tract

Epididymis

·       Epididymis epithelium*

·       Sperm (within lumen)

·       Stereocilia*

Vas Deferens

·       Vas deferens epithelium*

·       Muscularis externa

Urinary

Ureter

·       Ureter epithelium*

·       Submucosa

·       Muscularis externa

Urethra

·       Urethra epithelium*