Histology Review Part One

Well, in general, the histo practical should be the easiest part of histology.  You should be happy that this is also the most important.  I say that because there are no tricks.  Here is the information, if you learn it you will do well.  People who don’t do well on the practical do so because they haven’t spent enough time looking at their slides.  Be wary of short cuts (ie. videos, slice of life etc) because they don’t work regardless of the rumors you may hear.  There is no substitute for looking at your slides.  I know that this takes more time but you will learn it better so it is well worth it.  That is the best advice I can give you.  As far as this review goes, use it as a check list while you are looking at your slides.  I have listed the slide name and the structures on that slide that you should be able to identify along with some helpfull hints.  Good luck!

submandibular gland  (or sublingual but not parotid)

• ***Serous Demilune*** he always, always asks this, if you get it wrong I will kill you!!!!
• Be able to distinguish between mucous unit (lighter) and serous unit (darker)

kidney

• simple squamous epithelium (parietal layer of Bowman’s capsule)
• simple cuboidal epithelium (around the ducts)

skin (thin, not palmar or plantar)

• stratified squamous keratinized (you must say keratinized or it will be wrong) epithelium
• dense irregular connective tissue (dermis)
  • this is collagen type 1 (pink)-he will ask this, he is big on collagen types
• stratified cuboidal epithelium (around the sweat duct)
  • this is another one that he always asks so make sure you know it!
• adipose tissue (looks like chicken wire)
• sebaceous (however the hell you spell it) gland
• cells with foamy appearance associated with a hair follicle and not found in thick palmar or plantar skin-no one has hairy palms-hopefully anyway)

esophagus

• stratified squamous non-keratinized epithelium (also found in the vagina) *remember to write non-keratinized or it will be wrong
• loose aerolar connective tissue (underneath the epithelium)

jejunum

• simple columnar epithelium with goblet cells and brush border (you must write out that entire name or it will be wrong)
• Paneth cells (this is another one that he always asks)
  • popular secondary question:what does it secrete?-lysozyme*
• plasma cells (black dots in the loose areolar connective tissue)
• part of the immune system and necessary because of the nasty stuff we eat especially in Dominica!

ileum (you can also use colon)

• myenterric (Auerbach’s) plexus
• parasympathetic plexus located between the two layers of smooth muscle and is found through the GI tract

stomach

• simple columnar epithelium (also in gallbladder)
• notice the lighter color staining because each cell is mucous secreting
• therefore NO goblet cells or brush border

bladder (or ureter)

• transitional epithelium (dome shaped and/or bi-nucleate cells)

trachea

• ciliated pseudostratified columnar epithelium with goblet cells
• also refered to as respiratory tract epithelium but do not write that name on the exam

epididymis (human not primate)

• pseudostratified columnar epithelium with stereocilia
• remember that stereocilia are just long microvilli (actin microfilaments) so they are not real cilia

Note: here is a hint about the pseudostratified epithelia, the above two examples are the only instances where you will see them therefore, if it does not have either cilia or stereocilia, IT IS NOT PSEUDOSTRATIFIED even if it looks like it might be! You will also never see cilia or stereocilia on any other epithelium therefore, to determine if it is pseudostratified, first look for either one of those two surface specializations. This is a constant rule so use it for your practical!

tendon

• dense regular connective tissue (do not call this tendon on the exam)
• looks very much like smooth muscle and longitudinal section of nerve *therefore compare the three side by side to see the subtle differences

hyaline cartilage

• chondrocyte cell in a lacuna (you have to write lacuna otherwise it is wrong)
• isogenous group (remember this is interstitial growth)
• territorial and inter-territorial matrix
  • territorial matrix is darker because of the preponderance of GAG’s
  • remember this is collagen type 2 (type 2-blue)
• perichondrium
  • remember this part is collagen type 1 (pink)

developing membranous bone (fetal finger)

• perichondrium vs. periosteum
• just what the name says, if it is the part over the cartilage it is perichondrium if it is over bone it is periosteum.  These two structures are continuous with each other.
• know the five zones (resting, proliferating, hypertrophy, calcification, and ossification) remember that the process here is endochondral ossification
• **Sharpey’s fibers (another one that he will definitely ask) simply connects the periosteum to the bone collar
• bone collar (remember this is direct bone formation)
• cell types: osetoclast (large multinucleated), osteocyte and osteoblast

Note: One question that everyone seems to ask me is the difference between appositional, interstitial, direct and endochondrial bone formation.   I know it has nothing to do with your slides but since it is confusing I will mention it.  First, you are describing two separate things that is growth vs. bone formation.   They do not mean the same thing.  When talking about growth you use the terms appositional and intramembranous to describe it.  Appositional (bone and cartilage) is when cells (...blasts) move from the outside in and become (...cytes).   Interstitial (cartilage only) is when the chondrocytes divide within the middle of the cartilage and form isogeneous groups that eventually spread out.  Bone formation refers more to the embryology of bone.  Direct or intramembranous bone formation is what happens in the bone collar.  Bone is directly made from embryonic mesoderm.  Endochondrial bone formation is just what the name says, cartilage is made first then it turns to bone (indirect) and this is what is happening in the epiphyseal plate.

compact bone

• Haversian system or osteon
• osteocyte in a lacuna (must write lacuna)
• canaliculi (house cytoplasmic extensions of the osteocyte cell)
• interstitial lamella
• broken down osteon that looks like nothing significant in between osteons

ovary (this is one of his favorite things so know it well!)

• primordial follicle (just under epithelium, no zona pellucida)
• primary follicle (zona pellucida with no antrum)
• secondary follice (has an incomplete antrum)
• mature graafian (complete antrum)
• remember they all have primary oocytes regardless of what follicle it is.  It is the LH surge that triggers the completion of meiosis and you can’t tell that by looking at the slide!
• corona radiata
• zona pellucida
• cumulus oophorus
• interstitial cells (secrete estrogen)
• theca interna (produce androsteindione under the influence of LH)
• granulosa cells (turns androstenedione into estrogen under the influence of FSH)
• get the hormone thing down he will ask it as a secondary question
• atretic follicle (collapsed zona pellucida)
• germinal epithelium
• corpus luteum (big white thing that is somewhat cellular)

elastic cartilage

• looks “dark and creepy”
• has elastic fibers in it (duh) as well as collagen type 2

nerve longitudinal section

• be able to identify that it is nerve (and not tendon or muscle)
• *Node of Ranvier (know this one for sure)
  • a stupid little horizontal line that you can barely see but you know it is nerve and it doesn’t look like anything else

nerve cross-section (on same slide as above)

• axon vs. myelin sheath
• schwann cell (nuclei that you see)
• endo vs. epi vs. perineurium

cross section of spinal cord

• neuron cell body
• nucleus vs. nucleolus (yes he will ask you something that simple to confuse you)
• lipofuscin granuoles
  • brown stuff that accumulates in cells that don’t divide[FrontPage HTML Markup Component][FrontPage HTML Markup Component][FrontPage HTML Markup Component]
• Nissel bodies (ER)
  • can’t really see but blue stuff closer to the nucleus, when in doubt pick lipofuscin granules
• Be able to tell the difference between cardiac (intercalated disks), skeletal (striated), and smooth muscle.

 cerebellum

• molecular layer (outside, has dendrites of Purkinje cells)
• granular layer (inside, has axons of Purkinje cells)
• **Purkinje cell (likely to be a question)

 blood

• platelet (formed from megakaryocyte)
• neutrophil (multi-lobed nucleus, most common)
• monocyte vs lymphocyte
• lymphocyte is roughly the size of a RBC and a momcyte is much larger and also has a kidney shaped nuclueus (sometimes not always)
• eosinophil (pink-red granuoles)
• basophil (dark granules filled with histamine, so dark that you can barely see the nucleus but you can clearly make out the granuoles however, these are rare and you probably will not see one on your slide)

Well, that is about 99.9% of what you will get on your practical so if you manage to learn all of that you will most certainly get an A.  Remember that the histo practical is an easy way to bring up your grade if you need to, so don’t miss out on the opportunity because you didn’t dedicate enough time to it.  The key to doing well is good time management which means being organized and also getting enough sleep.  That is the best thing you can do for yourself. 

Histology Review Part Two

 Well, here we go again!  In general, first and foremost make sure you can identify the organ.  That is the most important because you will get a lot of questions asking you to simply identify the organ and also, you will not be able to correctly identify the specific structures if you have no idea what organ you are in.   The best way to do this is to just compare all of the organs on low magnification first before you go looking for specific structures.  If there is a specific cell type, make damn sure you know what it secretes!  As far as the cumulative part, make sure that you know your epithelia really well.  Also, know the ovary inside and out because Dr. K loves that.  You might want to also review the collagen types in different tissues i.e. hyaline cartilage is type 2 (blue) while bone is type 1 (pink).  Maybe also the fetal finger.  Otherwise, focus mainly on the new stuff because that is what you will be questioned on the most.

 skin

• Know the layers of the epidermis: stratum germinativum, stratum spinosum, stratum granulosom, (two types of granules-keratohyalin and lamellar), stratum lucidum (thick skin only), stratum corneum
• Melanocyte cell – clear cell in the germinativum (not the pigmented one which is a melanophore)
• Dermis has two layers: papillary layer (loose areolar CT) and reticular layer (dense irregular CT)
• Sweat ducts-stratified cuboidal,* myoepithelial cell – squamous cell that wraps around the outside of the sweat duct (squeezes out the sweat-gross!)
• pacinian corpuscle – looks like an onion, found in reticular layer of dermis, deep pressure and vibration receptor
• Meisner’s corpuscle – sort of S-shaped, found in the papillary layer, touch receptor
• <Neurovascular bundle – just what the name implies, a cross-section of nerve with a vein and arteriole.  Found deeper in dermis, not on all slides, may or may not be associated with a pacinian corpuscle
• Hair follicle with sebaceous gland – thin skin only (unless you are some sort of mutant that has hair on your palms!)

blood vessels

• Muscular vs. Elastic artery: muscular has only two elastic lamella an internal and external while elastic has too many to count.
• Tunica intima, media (collagen type 3) and adventitia (collagen type 1)
• Be able to tell the different between artery/arteriole and vein/venule

• *vasa vasorum-stupid little circles within the adventitia

 lymphatics

• Lymphatic nodules - *always B cells (remembering that will help you with all of the secondary questions), primary (no germinal center, has not been antigenically challenged), secondary (germinal center*-has been antigenically challenged therefore it contains plasma cells and memory B cells*).  They are found in the lymph node, palatine tonsil, ileum, colon, and appendix
• Lymph node - ID by the lymphatic nodules which are located all around the outside (cortex), also it has a capsule and a sub-capsular (not sub-scapular) sinus. If you remember that lymphatic nodules are only B cells, and the lymphatic nodules are located in the cortex, then the cortex has B cells!  Next, paracortex has T cells and then the medulla has B cells! (BTB)
• Palatine tonsil - ID by the lymphatic nodules that are located everywhere (vs. in the periphery in the lymph node) also, it has crypts
• Thymus-no lymphatic nodules * (duh, it only has T cells!) Darker area outside is the cortex, lighter area inside is the medulla. **Hassel’s corpuscles-pink circular things, made of degenerating epithelial-reticular cells.  If you look at it on high magnification you see lots of lymphocyte cells (black dots) and the occasional pink cells which are the epithelial-reticular cells
• Spleen - ID by the lymphatic nodules (white pulp but actually stains blue?????) with a central arteriole.   Remember that the white pulp, since it is nothing more than a lymphatic nodule has B cells but, the area immediately around the central arteriole, PALS has T cells* Everything else in between is the red pulp
• Appendix - circular thing with a lumen and lymphatic nodules all around it.  If you look closer, you will see that is has GI tract epithelium (simple columnar with goblet cells and a brush border)

gastrointestinal

• Esophagus-compare to vagina, has stratified squamous non-keratinized epithelium with esophageal glands (duh).  The muscularis externa contains either skeletal, smooth, or a mixtures of both types of muscle depending upon where the cross-section is made
• Stomach-simple columnar epithelium that is all mucous secreting therefore is does not have goblet cells.  It also has three layers of muscularis externa and a large area of gastric glands.  Magnify the area of the gastric glands and you will find the different cells types.  *Parietal cell – pink, secretes HCL and intrinsic factor.   *Chief cell – blue, makes pepsinogen.  If you can’t remember which cell is which, just remember that the chief cells have a “manly” name and are therefore blue!
  Make sure you know the layers in all slides of the GI tract i.e. Lamina propria, muscularis mucosae, submucosa and muscularis externa.  Also, if he wants you to ID a cell type within the lamina propria it is most likely a lymphocyte or plasma cell (black dots).  If you see any white spaces that form lines within the lamina propria/villi it is probably a lacteal (small lymphatic vessel)
  Don’t forget about the Myenterric or Auerbach’s Plexus which is the parasympathetic ganglia located in between the inner circular and outer longitudinal muscle layers of the muscularis externa throughout the GI tract.
• Duodenum ID by the *Brunner’s glands which secrete an alkali mucous, it also has villi and plica circularis with normal GI epithelium (simple columnar with goblet cells and brush border)
• Jejunum-*no Brunner’s glands, also has longer plicae.  Don’t forget about good old *Paneth Cells that have the bright red granules and secrete lysozyme.
• Ileum-shorter plicae, many more goblet cells, peyers patches (lymphatic nodules that don’t have the normal GI tract epithelium over them.  They instead have the M cells)
• Colon no villi, many more goblet cells
• Gallbladder ID by the really weird projections on the surface, also has simple columnar epithelium, no brush border etc.
• Parotid gland-only serous units
• Submandibular – mixed but predominantly serous
• Sublingual-mixed but predominantly mucous
• Don’t forget about ******Serous Demilune!!!!!!!!!
• Liver-unless he uses the pig liver, you will not really see the classic lobule etc.  ID by the central vein and the unique appearance of the hepatocyte cells.  Different from spleen and pancreas because it all essentially one color.  Also, no lymphatic nodules in the liver.  Don’t forget about the triad found at the corners of the liver lobule (assuming he does show the pig liver)-hepatic artery, portal vein and bile duct
• Pancreas – looks  like undercooked steak, has areas of lighter pink coloring which are the islets of Langerhan’s (endocrine).  Red areas in between is the exocrine portion.  ID this organ by its coloration also, no lymphatic nodules.