You've got some nerve . . . . .

Sorry for the pun.... :)  You guys are all expert histologists now. Feels pretty good doesn't it?? If I were you, I would keep reviewing the midterm material over the next few weeks up until the final, because the new is definitely lighter than past lectures. One of the key things for this week is to recognize what nerve cells look like. Check out the pictures below. Notice that they all are fairly similar looking (as are most nerve cells)--central nucleus, large cytoplasm, etc.

The nerve cells are those running diagonally down the middle of the pic.

Other Key Things to Remember:
-The anatomical names of the nerve connective coverings are the same as muscle (epi-, peri-, and endoneurium), but the histological classifications are slightly different. Remember that the epineurium is the thickest covering that surrounds the entire nerve. Anything that is cutting through the middle of the nerve will be perineurium, and anything surrounding a single fiber/axon will be endoneurium.

-What stains nerve tissue??? (hint: Gold, _____, Bronze)

-Know what satellite cells are, where to find them (p. 46), and what they do.

-For the central nervous system, don't go off of the color of the tissue on the slides to determine what is white/grey matter because white matter can be the darker of the two... you think they would have figured that one out right??? :) Remember from your anatomy days that the brain is like an oreo (grey matter on the outside, white on the inside) and your spinal cord is like a hotdog (white on the outside and grey on the inside).

-Make sure you can ID the dorsal and ventral sides of the spinal cord. The easiest way for me to do that is to remember the pneumonic "Heading to the back dor (like door, stands for dorsal)." Let me explain... the dorsal horn is in the back, and it touches the edge of the spinal cord while the ventral horn does not. It looks like the DORsal horn is heading to the back door. Also, the dorsal horn is usually narrower. Whatever works for you!

See the dorsal horn heading to the back door???

-Make sure you memorize the layers of the cerebrum!!! And that you can name them in order... Don't worry too much about being able to distinguish between all the layers on the slide, they can be pretty ambiguous. Remember the PP sandwhich :) And that it's inner inner, outer outer with pyramids on the bottom and crumbling granules on top of them ( i.e. inner pyramidal, inner granular, outer pyramidal, outer granular).

-For the cerebellum, know the layers and how to ID them on a slide or on a U-Find. They're pretty logical though - white matter on the inside (remember... OREO!!), then comes the granular layer which looks.... very granular :) (always does...), and the outermost layer is the molecular layer (think: molecules are smaller than granules... can't really see molecules). In between the molecular and granular layers is the purkinje cell layer (looks like a row of nerve cells separating the two layers). Here are some pics for your viewing pleasure...

This picture should look familiar to all of those who are in physiology. Aren't those purkinje cells cool?!?! Which layer is more granular looking?

If you're having a hard time orienting yourself, look for the sulci (grooves of the brain).

- For the meninges, in between the lobes of the brain is a good place to point to for pia mater on U-Finds. Dura mater is often not present...

-Ependymal cells - where are they present??? (choroid plexus and central canal). Remember that they change histologically over time. I like the remember it this way: as you get old, you get short and bald (ciliated simple columnar --> sparsely ciliated simple cuboidal -->simple squamous).

-Auerbach's and Meissner's plexi both help regulating peristalsis. Auerbach's is found between the inner circular and outer longitudinal layers (think Auerbach sounds Austrian, kinda like Arnold Schwarzenegger, who has lots of muscles . . . so Auerbach's is gunna be between all those muscles). Zoom in and look for cells that fit the look of the ones at the beginning of this blog post. I prefer to look in the jejunum for these plexi, just because there aren't really any other structures there to confuse them with (no Brunner's or Peyer's patches). The Meissner's plexus is found at the very basal edge of the submucosa right before you get to the inner circular muscle layer (think Meissner Mucosa). Once again, zoom in and scan around until you find something that fits the profile of a nerve cell. 

Here's a little game of "Where's Waldo" for you. These pictures were both taken of that slide.

Meissner's (Base of sub-mucosa)

Auerbach's (lighter clustered structures toward the left-middle) - notice the smooth muscle on either sides??

Other Random Pics:

Meissner's

Auerbach's (notice the muscle layers on either side)

-For the retina: Be able to identify (slide and U-Find) all of the layers and name them in order. The inner/outer nuclear layers are highly nucleated. The ganglionic cell layer can also look nucleated, but will sometimes, but not always, be thinner than the nuclear layers; generally the ganglionic cell layer will have much larger nuclei. The plexiform layers look clear (like plexiglass). Remember that outer isn't referring to the outer part of the body, but the outer part of the slera (think the backside of your eyeball).

Notice how the ganglionic cell layer is thick here? (see E) However, the nuclei aren't as tightly packed, are larger, and have colored cytoplasm - fairly common characteristics for this layer

-Make sure you know what neurons are unipolar, bipolar, etc. Some people like to remember it using the following: one tongue --> unipolar neuron, two ears --> modified bipolar neuron, two nostrils-->bipolar neuron, two retinas --> bipolar neuron.

Good luck on the quiz!! As always, feel free to let us know if you have any questions.

Nervous Review Sheet

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 nervous histology, but keep in mind all of the following terms.

Cross Section of Nerve

·       Epineurium*

·       Perineurium*

·       Endoneurium*

Myelinated Longitudinal Section of Nerve

·       Nerve axon

·       Node of ranvier

Neuron Cross Section

·       Nerve cell body

·       Satellite cells

·       Epineurium*

·       Endoneurium*

Spinal Cord

·       White matter*

·       Grey matter*

·       Dorsal horn*

·       Ventral horn*

·       Posterior median sulcus*

·       Anterior median fissure*

Cerebrum

Focus on the organization of the layers

·       White matter

·       Polymorphous/Multiform layer

·       Inner (pyramidal) ganglionic layer

·       Inner granular

·       Outer pyramidal cell layer

·       Outer granular

·       Plexiform (molecular) layer

Cerebellum

·       White matter*

·       Granular layer*

·       Purkinje cell layer*

·       Molecular layer*

Meninges

·       Pia mater*

·       Arachnoid mater

·       Dura mater

Choroid Plexus

Know how ependymal cells change with age

·       Ependymal cells*

Associated Nervous Tissue

·       Auerbach’s plexus*

·       Meissner’s plexus*

·       Intrafusal fiber

·       Purkinje fiber*

Multipolar Neuron

·       Dendrite

·       Nerve cell body

Special Senses

Retina

·       Inner limiting membrane*

·       Optic nerve fiber layer*

·       Ganglionic cell layer*

·       Inner plexiform*

·       Inner nuclear*

·       Outer plexiform*

·       Outer nuclear*

·       Outer limiting membrane*

·       Rods and cones*

Taste Bud

·       Tongue epithelium

·       Sustentacular cells*

·       Taste bud*

·       Taste pore

Organ of Corti

·       Hair cells*

·       Tectorial membrane*

·       Vestibular membrane*

·       Basilar membrane*

Olfactory Epithelium

·       Bowman’s gland

·       Olfactory receptor cells*

·       Olfactory epithelium

Muscle!!!

Hey guys!

Hope you all survived the midterm and are ready to start another week of histology!!!! Hopefully the midterm was able to help you see areas you need to practice or helped boost your confidence in what you already know :) If you didn't do so hot, remember you can drop the midterm and that there's still the final which is worth half of your grade.

This week is muscle - make sure you know the differences between the 3 types of muscle:

See the difference between the transverse and longitudinal cuts?

Skeletal:
- multinucleated
- peripheral nuclei
- striations
- can be regularly or irregularly arranged

See the layers?

Smooth:
- uninucleated
- central nuclei
- no striations
- fusiform shape
- usually comes in layers

The intercalated discs allow current to pass from cell to cell

Cardiac:
- bifurcated
- central nuclei
- intercalated discs containing several gap junctions
- striations








Also, be sure you can find/identify intrafusal fibers and know their function, i.e. prevention of muscle over-stretching; remember their histological name is modified skeletal muscle fiber and that the capsule is DCCTRA. Normally, intrafusal fibers are about 2-3 times the size of a single skeletal muscle fiber and are surrounded by a collagen sheath (connective tissue).

Sarcomeres

So, just a refresher from anatomy of what's actually going on in the sarcomere - remember that all the actin is coming from the Z-line and all the myosin is coming from the M-line. Contraction is due to an increase in overlap between actin and myosin. The M-line is located in the A-band - THE A-BAND DOES NOT CHANGE SIZE DURING CONTRACTION!!!! Remember that it is the I-band and H-bands that shrink as myosin and actin overlap more. 

 Now, try to find the above structures on a real image. Remember: 'Zoro Is A Hairy Man' ;)







As we zoom out, can you see where those striations come from? Smooth muscle doesn't look like this because they don't have sarcomeres like skeletal and cardiac muscle; they have a completely different method of contraction which you will learn more about in advanced physiology :)






 Also, make sure to study exceptions/anomalies - those tend to make good quiz/final questions :) For instance, the tongue is the only place in the body where we find skeletal muscle irregularly arranged.

See the longitudinal AND transverse muscle fibers?

Also, when it comes to memorizing the different smooth muscle layers, remember most of the time the layers will be inner circular, outer longitudinal - then just memorize the exceptions, which there are a few :/ Also, remember that the inner circular layer is responsible for segmentation while the outer longitudinal layer is required for peristalsis.

The exceptions are:
1. the stomach - has three layers; essentially just adds an inner oblique layer to the normal inner circular, outer longitudinal - so it becomes inner oblique, middle circular, outer longitudinal
2. the uterus and vagina - just think about it - girls are all over the place! (sorry gals) ;) So are the muscle layers of female repro . . . oh wait, there aren't any! Almost all of the female female repro system is smooth muscle irregularly arranged - think about the parts of the female repro that have to do a lot of stretching - those are the ones that are going to be irregular
3. the vas deferens - remember that the vas deferens has tons of muscle - it needs that muscle to act as a pump - I think of the vas deferens as a sandwhich (inner longitudinal, middle circular, outer longitudinal)
4. the ureter: the ureter is just whacked - it's exactly opposite of everybody else: inner longitudinal, outer circular


Blood Vessels

Make sure you know the anatomical layers of the heart - epicardium, myocardium, endocardium, and what they are histologically

Purkinje fibers - these are modified cardiac myocytes located just under the endocardium in a region called the subendocardium; remember that impulses in the heart originate at the SA node, travel to the AV node, through the left and right bundles located in the interventricular septum to the purkinje fibers - these fibers travel through the ventricular walls to spread the current

- purkinje fibers are non-contractile cells and contain fewer myofibrils - this means they take up less stain, i.e. they are generally lighter on a slide and are larger, often binucleated cells.

Look for them near the 'edge' of the tissue on your slide - if you point to cells in the middle of the myocardium, chances are they're not purkinje fibers - as you can see in the diagram on the left, purkinje fibers tend to stay out of the muscle wall







Large, medium, small artery and arteriole


Make sure you know what makes up the different tunics:
1. tunica intima: endothelium + basement membrane + internal elastic lamina
2. tunica media - just the muscle layer
3. tunica adventitia - LCT with some DCCTRA


Large artery:

See the 1:1 muscle cell layer to elastic fiber ratio?

Medium artery:

Notice the distinct internal and external elastic laminas; also, the virtual absence of elastic fibers in the tunica media

Small artery:

Note the absence of an external elastic lamina, but still a distinct internal elastic lamina

Also, know capillaries and where to find them (lungs and kidneys are a good place) and that they are made of simple squamous epithelium.




Large, medium, small veins

 I absolutely love this picture - notice the differences between the medium artery and medium vein? The vein is much more collapsed and has a much thinner muscle layer - remember, they don't do any pumping, whereas the arteries do lots of pumping and stretching.

Also, veins tend to have a much thicker tunica adventitia and no internal/external elastic laminas

For the purposes of this class, a large vein is one whose lumen doesn't fit entirely on the view screen.

Good luck ya'll!!!!

Muscle Review Sheet

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 muscle histology, but keep in mind all of the following terms.

Skeletal Muscle

Transverse Cut

·       Skeletal muscle*

·       Epimysium*

·       Perimysium*

·       Endomysium*

·       Fascicle*

·       Peripherally located nuclei

Longitudinal Cut

·       Perimysium*

·       Endomysium*

Intrafusal Fiber

·       Intrafusal fibers*

·       Capsule

Sarcomere

·       A-band

·       H-disk

·       M-line

·       Z-line

·       I-band

Neuromuscular Junction

·       Terminal bouton (motor end plate)

·       Nerve axons

·       Skeletal myofibers

Tongue

·       Circumvallate papillae*

·       Von Ebner’s gland

·       Taste bud

·       Skeletal muscle*

Cardiac Muscle

Cardiac Muscle

·       Bifurcations

·       Intercalated discs

·       Centrally located nuclei

Smooth Muscle

Longitudinal Cut

·       Smooth muscle fiber (fusiform shape)

·       Centrally located nuclei

Transverse Cut 

·       Smooth muscle myocyte

·       Centrally located nuclei

 Vasculature 

·       Tunica intima*

·       Tunica media*

·       Tunica adventitia*

Intestine

·       Muscularis externa*

·       Inner circular*

·       Outer longitudinal*

·       Muscularis mucosa*

Stomach

·       Muscularis externa*

·       Inner oblique*

·       Middle circular*

·       Outer longitudinal*

·       Gastric gland

·       Muscularis mucosa*

Reproductive Tract

Uterus

·       Endometrium*

·       Myometrium*

·       Uterine glands

·       Uterine epithelium

Vagina

·       Smooth muscle*

·       Lamina propria

·       Vaginal epithelium

Oviduct

·       Oviduct epithelium

·       Lamina propria

·       Muscularis externa*

·       Inner circular*

·       Outer longitudinal*

Vas Deferens

·       Vas deferens epithelium

·       Inner longitudinal layer*

·       Middle circular layer*

·       Outer longitudinal layer*

Urinary Tract

Ureter

·       Ureter epithelium

·       Inner longitudinal layer*

.         Outer circular layer*

Circulatory System

Heart

Outer Heart Wall

·       Adipose tissue

·       Myocardium*

Inner Heart Wall

·       Endocardium*

·       Purkinje fibers*

Vasculature

Large Artery

·       Tunica intima*

·       Internal elastic lamina*

·       Tunica media*

·       Tunica adventitia*

Medium Artery

·       Tunica intima*

·       Internal elastic lamina*

·       Tunica media* (sporadic elastic fibers)

·       Tunica adventitia*

Small Artery

·       Tunica intima*

·       Tunica media* (~4 layers)

·       Tunica adventitia*

Arteriole

·       Tunica intima* (very thin internal elastic lamina)

·       Tunica media* (~2-3 layers)

·       Tunica adventitia

Capillary

·       Endothelium*

Large Vein

·       Tunica intima (no elastic lamina)*

·       Tunica media*

·       Tunica adventitia*

Medium Vein

·       Tunica intima*

·       Tunica media* (a few muscle layers)

·       Tunica adventitia*