grant o’rourke – Page 2 – Outlander Anatomy

September 29, 2015September 29, 2015

“Aye, Eye – The Eyes – Part 2!”

Greetings faithful anatomy students! Today we continue our studies of the complex and elegant eye in Anatomy Lesson #30, The Eyes – Part 2. Anatomy Lesson #29 covered anatomy and function of eyelids, eyebrows and eyelashes. Today, we will discuss other structures that are designed to aid the eye in the vision it provides: bony orbit, orbital fat (yes indeed!), conjunctiva, lacrimal apparatus, and extraocular muscles.

And just to set the mood, eyes are extremely important in the English language. A quick glance (ha ha) yields more than 200 eye idioms: catch one’s eye, apple of one’s eye, in the blink of an eye, more than meets the eye, in a pig’s eye, all eyes and ears, a bird’s eye view, a sight for sore eyes, easy on the eyes, bedroom eyes (we know who has THOSE! ?), can’t take eyes off of, eye for an eye, catch one’s eye. Well, you get the idea…references to the eye makes English more colorful! Blink. Blink. Wink. Wink.

SPOILER ALERT: early in this lesson a wee spoiler appears from Diana’s eighth book of the Outlander series: no names, no dates, and no places. A warning will surface beforehand. Look for this (heehee…this is going to be fun!) obnoxious, glaring, flashing sign so you can skip and not whinge about something you would rather not read. Don’t say I didn’t warn ye!

Let’s begin this lesson by considering the bony home for the eye. Each eyeball dwells in a cave known as the bony orbit (Photo A – dashed black line). Each orbit is composed of skull bones, some of which are so thin they readily transmit light (Photo A – black arrow). It isn’t even Halloween yet – Boo! ?

Photo A

A whopping seven skull bones form each bony orbit. These are difficult to distinguish in the adult skull where the bones are fused, but easily discerned using a color coded image (Photo B – right bony orbit):

Blue = fontal bone

Orange = zygomatic bone

Green = maxillary bone

Violet = lacrimal bone

Grey = ethmoid bone

Pink = palatine bone

Gold = sphenoid bone

The bony orbits protect and support the eyeballs and provide attachment for several accessory structures. Although difficult to appreciate in a two-dimensional figure, each orbit is shaped like a cone: the apex (point) lies at the back and the base, or orbital rim, faces front (Photo B – dashed black line). Each apex has holes which serve as access ports for nerves and blood vessels to enter and leave the bony orbit (Photo B – red stars). The orbital rim, roof and temporal (side) walls are thick and strong but the nasal (medial) wall and part of the floor are thin and delicate (Photo B – black arrows). In fact, each medial wall is so thin it is known as the lamina papyracea (Latin meaning paper layer)!

Photo B

Indeed, a direct blow to the bony rim can break any of walls but the medial wall and floor are most commonly disrupted. Known as a “blowout” fracture, this injury appears in one of Diana’s prolific writings!

SORTA SPOILER ALERT: The following quote describes this type of injury. If you don’t want to read it skip the next two quotes and images and head straight for the furry mammal with the big eyes. NO! Not Rupert! It has orange eyes and Rupert doesn’t.

Herself correctly describes the consequences of a blowout fracture suffered by a character in her 8^th book, Written in My Own Heart’s Blood, a.k.a. Moby. Claire relates:

A split lip and badly swollen eye seemed to be the chief injuries… The eye was swollen half shut …the underlying flesh a lurid palette of green, purple, and ghastly yellow. The eye itself was red as a flannel petticoat … I couldn’t move the globe of the eyeball upward at all…

Clinical Correlation #1: Photo C shows the appearance of a right eye (on your left) with a classic blowout fracture juxtaposed with a normal left eye. The left eye has a white sclera, normal skin of eyelids and cheek and, when tested, the patient can elevate (lift) the normal eye. The right eye is patently abnormal: the sclera is red due to hemorrhage and the eyelids and cheek are bruised and swollen also due to hemorrhage. The right eyeball cannot be raised in tandem with the left eye; it is frozen with the gaze directed forward. Failure to elevate the right eye occurs because a small muscle of the eyeball (inferior rectus – see below) is trapped within the fracture, anchoring the globe and preventing its lift.

Photo C:

And, continuing the quote from Moby – again, Dr. Sassynach is our observer:

It was almost certainly what was called a “blowout” fracture, which had cracked the delicate bone of the orbital floor and forced a displaced bit of it—along with part of the inferior rectus muscle—down into the maxillary sinus. The edge of the muscle was caught in the crack, thus immobilizing the eyeball.”

YOU CAN LOOK NOW!

See, I told ye it wasna Rupert!

Photo D is a vertical CT scan through the skull. The paired ghoulish-looking white rings are the bony orbits. The patient’s left orbit (on your right) is normal; the black triangular space below it is the normal left maxillary sinus. These are separated by a thin white line, the orbital floor (Photo D – green arrow). The patient’s right eye shows a blowout fracture. The red arrow points to the white, broken and dangling bony bit of the orbital floor. The right maxillary sinus is grey because it is filled with displaced orbital tissues: the light grey material is prolapsed orbital fat (see below) and the aforementioned inferior rectus muscle (Photo D – blue arrow) which is trapped in the fracture anchoring the eyeball so it cannot be elevated. Very interesting stuff!

$Blowout-fracture-KLS-edited$

Photo D

Now, structures other than eyeballs inhabit the bony orbits, including extraocular muscles, blood vessels, nerves and orbital fat. However, the eyeballs do not touch the bones of the orbit. Rather, they rest-in-a-nest of orbital fat that fills all the nooks and crannies not otherwise occupied. Orbital fat acts like a shock absorber cushioning the eyeball against trauma; it also serves as a socket in which each orb glides, slides and rotates. Photo E shows a horizontal section through the right eyeball and bony orbit; the cone shape of the bony orbit is easily appreciated from this birds-eye view (Photo E – black dashed lines). For orientation, the cornea and superior tarsus are labelled (Anatomy Lesson #29). See the yellow globs of “stuff” surrounding the eyeball? This is orbital fat and it is surprisingly abundant! Periorbital fat is also present but it lies superficial to the bony orbit being confined to eyelid margins and overlying orbital rim and cheek bone/zygomatic arch (Anatomy Lesson #8).

Try this: Close one eye and gently tap the soft tissues around the eyelids and overlying the orbital rim and zygomatic arch. Feel the springy and spongy nature of the soft tissues? This is periorbital fat. Orbital fat lies deep in the bony orbit and cannot be readily palpated.

Photo E

Most of the exposed eye is covered with the conjunctiva, a transparent, vascular mucous membrane. Bulbar conjunctiva overlies the sclera (white part) of the eyeball but it stops at the corneal rim and hence, does not cover the cornea. Palpebral conjunctiva lines upper and lower eyelids (Photo F).

Photo F

This design is possible because the conjunctiva reflects (turns) from the sclera onto the insides of upper and lower eyelids (Anatomy Lesson #29). This reflection creates a blind pocket or fornix where the sheet of conjunctiva turns from one surface onto another (Photo G – vertical section through eyeball and lids of eye). Thus, objects trapped on the exposed surface of the eyeball (e.g. contact lens) cannot move into the deep recesses of the bony orbit unless the conjunctival fornix is torn. The conjunctiva secretes mucus and contributes to the tear film (see below); it also produces immune cells that help protect the eyeball from microbes.

Photo G

Now, it is time to consider the lacrimal apparatus (Latin meaning tears), an uppity name for the system which produces and drains tears. The lacrimal apparatus for each eye includes a lacrimal gland, lacrimal canaliculi, lacrimal sac and nasolacrimal duct.

The lacrimal gland is roughly the size and shape of a large almond. Most of it lies inside the bony orbit but a smallish part sits in the outer upper eyelid (Photo H). The purpose of the gland is to secrete (discharge) the aqueous part of the tear film. Several small ducts (tubes) pierce the conjunctiva and empty the secretion onto the surface of the eyeball.

Photo H

As the palpebral parts of orbicularis oculi (Anatomy Lesson #29) close the eyelids, the tear film sweeps across the exposed surface of the eyeball. To understand where it goes next, please see Photo I. Near the nasal ends of upper and lower eyelids, the eyelashes (Anatomy Lesson #29) disappear and small elevations appear on the lids; these are superior and inferior lacrimal papillae (pl.). Each papilla bears a small opening, the lacrimal punctum.

Try this: Face a mirror and gently pull down on the lower eyelid. See the small bump near the medial canthus (Anatomy Lesson #29)? This is the inferior lacrimal papilla. Find its tiny opening, the inferior lacrimal punctum. Repeat with the upper lid.

Photo I

As the eyelids close, the tear film is swept toward the lacrimal puncta (pl.). Tears then enter the puncta and drain through the next group of lacrimal structures: lacrimal canaliculi (pl.), lacrimal sac and nasolacrimal duct. The paired lacrimal canaliculi are tiny ducts, each leading from its respective punctum to the lacrimal sac, an enlargement at the side of each nasal cavity. Tears then drain into the longer nasolacrimal duct.

Photo J

The nasolacrimal duct opens into the outer wall of each nasal cavity (Photo K – outer wall of right nasal cavity) under shelter of the inferior concha (Anatomy Lesson #28). After collecting in the nose, we blow out or swallow our tear film.

Hard to believe, but the thin tear film (40 µm or .0016 in) has three layers: 1) a deep mucous layer made by specialized conjunctival cells; 2) a middle aqueous film produced by the lacrimal glands; 3) an outermost lipid sheet released by tarsal glands (Anatomy Lesson #29).

Excessive tearing caused by pain or intense emotion, floods the lacrimal system, spills over the cheeks and fills the nasal cavity; this is why our nose “runs” when we weep.

Photo K

Can we see lacrimation (flow of tears) at work in Starz episodes? Oh, aye! Claire is a strong 20^th century woman but I count at least six season one episodes where she weeps. This is my favorite: the lass is touchingly, tenderly tearful while confronting her beloved hubby about his intent to end it all (Starz episode 116, To Ransom a Man’s Soul). Intense emotions have her lacrimal system in full flush!

Speaking of crying, Jamie presents us with a gut-wrenching, Emmy-worthy (AHEM!) performance as a single tear overflows his lid and slips down his face. Bound by his word, he stays absolutely still as the wicked wolverine (oops, Wolverton) of Wentworth messes with his scars (Starz, episode 115, Wentworth Prison). Ugh! Puir lad!

In addition to the above structures, each eyeball is moved by six extraocular muscles (intraocular muscles are inside the eyeball). These are all voluntary, strap-like muscles: four are recti (pl., Latin meaning straight) and two are oblique. The four recti muscles arise at the apex of the bony orbit, pass directly forward and attach to the eyeball like the hours on a clock face. In a left eyeball (Photo L – left eye) superior rectus inserts at the 12:00 position, inferior rectus at 6:00, lateral rectus at 3:00, and medial rectus at 9:00. Understand that the positions of medial and lateral recti are reversed in a right eyeball: medial rectus inserts at 3:00 and lateral rectus at 9:00. Superior oblique and inferior oblique are so named because they approach and insert into the eyeball at oblique angles.

Figure L

Movements of the head provide coarse adjustments to eye position but the extraocular muscles produce fine movements of the eyes. The four recti move each eye in linear directions: up (elevate), down (depress), toward the nose (adduct) and toward the ears (abduct). Oblique muscles roll each eye inward toward the nose (intorsion) or outward toward the ears (extorsion). The table below shows the main movements attributed to each of the six extraocular muscles. Each of these movements is aided by other extraocular muscles but these combos are beyond the scope of this lesson. Extraocular muscle movements are complex and require activation by three pairs of cranial nerves (from the brain) and several brain centers (too complex for our lesson).

Superior rectus	Inferior rectus	Medial rectus	Lateral rectus	Superior oblique	Inferior oblique
elevates	depresses	adducts	abducts	intorsion	extorsion

Each extraocular muscle has a yoke muscle that operates in concert to coordinate the gaze. For example, when we gaze to the right, the left medial rectus adducts the left eyeball and the right lateral rectus abducts the right eyeball. When we gaze to the left, the opposite muscle actions occur. Ditto for the obliques: as we roll our eyes to the right, the right inferior oblique contracts in tandem with the left superior oblique. The opposite muscles engage as our eyes roll to the left.

NOTE: both medial recti muscles adduct our eyes as we examine near objects but we will revisit this issue in the next eye lesson. Personally, I have never known a person who could simultaneously contract both lateral rectus muscles to abduct the eyes (eyeballs point toward the ears) although in an 1837 article from The London Medical Gazette, the author states that some men (?) can perform this maneuver. What about those lassies?

Speaking of maneuvers…get a keek of this! Och! All those lovely eye muscles working in tandem give us that gaze! Gah!

A simplistic description of the extraocular muscles at work can be seen at this link https://www.youtube.com/watch?v=f4RxYRpIqLs!

Or, for an interactive and sophisticated version, try this link. It’s a bit involved but here’s how it works: go to the site http://www.bmc.med.utoronto.ca/anatomia/intro.swf, select orbit, then select structure & function, and lastly, select extraocular muscles. On the right is a giant H with a four-arrow circle. Capture the circle with your mouse and move it along the H to activate and view the six extraocular muscles at work. Very cool!

Hey, here’s a novel idea, let’s use more Starz episodes to help us understand eye movements! Time for Claire to hop onto the dissection table: here she contracts both superior recti to elevate her eyes (Starz, episode 103, The Way Out). She’s had, oh, um, roughly one hogshead of Colum’s finest rhenish wine – she canna really recall but enough to drop Angus under the table. Even Jamie is waaay impressed! Claire’s eyes also demonstrate an interesting Eye Rule #1: lift the eyes – lift the lids meaning levator palpebrae superioris (Anatomy Lesson #29) and superior recti muscles contract together.

Try this: close both eyelids. Now attempt to elevate the eyes while keeping the eyelids closed. You’ll find it is difficult to almost impossible because of Eye Rule #1: lift the eyes – lift the lids. If you can lift your eyes while keeping the lids closed, then per Rudyard Kipling (the (wo) is my addition):

By the livin’ Gawd that made you,

You’re a better (wo)man than I am, Gunga Din!

Claire is still in the dissection lab as both inferior rectus muscles contract to depress her eyes (Starz, episode 109, The Reckoning). Note that her upper eyelids are also lowered. She’s totally pissed at Jamie ‘cause his sword belt gave her a licking (Not the only lickin’ she gets. Snort)! Now, I could be wrong, but isna she wrapping her hair with an elastic band in prep for beddy bye sans Big Red One? Har har. Don’t think those bands were invented for another century or so. Eye Rule #2: lower the eyes – lower the lids; as the eyes depress (look down), the eyelids lower; inferior recti and palpebral part of orbicularis oculi contracting together. Yes! Bravo!

Try this: With eyelids widely open, try depressing your eyes. It is possible but verra difficult.

Ooooh! If looks could kill, Claire would be six feet under right here, right now! Casting the evil eye, wee wily LegHair (dissing the character not the awesome actress!) glares at Claire and Jamie as they share wine, words, gazes and body heat (Starz, episode 103, The Way Out)! Yoked together, her right lateral rectus abducts the right eye and her left medial rectus adducts the left eye. Her eyes are slightly elevated because her head is tilted to the right. Got it? Super-duper!

Now, LogHare isna the only character who can coordinate eye movements: fury and fear curdle Jamie’s wame as he watches Black-Jack-Rat run a dagger tip along Claire’s linea alba (Anatomy Lesson #16). He’s so friggin’ mad and scairt he can scarcely contain himself (Starz episode 109, The Reckoning). Yoked together, the right medial rectus adducts his right eye and the left lateral rectus abducts his left eye. Both eyes are also slightly elevated because his chin is tilted down. This keeps his gaze focused on the “object” of interest – rat man. Ye ken? Grand!

Let’s finish this lesson with some interesting tidbits about leeches (Hirudo medicinalis). Ahhh… What do leeches have to do with eyes? Well, hang on and let’s find out! Leeches have a long shared history with humankind. A mural from an 18^th dynasty tomb in Thebes shows that leeches were used for medical purposes as early as 1300 B.C. Later, Latin and Greek writers Plautus, Cicero and Horace wrote of medicinal leeches using the names of bdella, sanguisuga or hirudo. The English word leech is from the Old English word “laece,” meaning doctor! Yikes! Today, many modern medical centers employ leeches in plastic surgery and trauma medicine especially to relieve venous congestion (Photo M). Mother Nature at her verra best!

Photo M

In the 18^th century, medical practitioners transported leeches in special containers. Talk about fancy pet carriers! These beasties were not only placed on the skin but in some pretty hard to reach areas such as mouth, conjunctiva, rectum and vagina (Photo N – 18^th & 19^th century leech carriers). The clear tube at the bottom of this pic was used for placement in hard-to-reach places!

Photo N

And, when not being transported, leeches were kept in some verra purty jars. Nice housing, guys!

Photo O

Herself writes about leeches and healing in Outlander book. After Rupert beats Jamie in the great hall, Mrs. Fitz places leeches on his swollen face. Claire describes the event:

“That eye, now, lad, let’s have a look at that.”… “Still bleedin’ under the skin. Leeches will help, then.” She lifted the cover from the bowl, revealing several small dark sluglike objects, an inch or two long, covered with a disagreeable-looking liquid. Scooping out two of them, she pressed one to the flesh just under the brow bone and the other just below the eye… she explained to me, “once a bruise is set, like, leeches do ye no good. But where ye ha’ a swellin’ like this, as is still comin’ up, that means the blood is flowin’ under the skin, and leeches can pull it out… When ye use ’em on an old bruise, they just take healthy blood, and it does the bruise no good.”

The fabulous leech scene was filmed but edited from the aired version (Starz episode 102, Castle Leoch). So, here’s a wee bit of the deleted footage where Mrs. Fitz works leech magic (purported to be black licorice) on Jamie’s red and swollen left eye and cheek (see gif). Rupert’s eye punch broke blood vessels that hemorrhaged into extraorbital fat and loose connective tissue of eyelids, brow and cheek. Had the punch directly hit the bony orbit and eye, Jamie could have suffered a blowout fracture!

Claire de-claires (ha ha) that the leech-leach induces remarkable improvement, but she also uses this as a chance to cradle Jamie’s face. Yep! This lass just wants to pet that lad’s epidermis! Hang on, Claire – more skin touching is, erm, coming!

Eyes are endlessly amazing and today, we learned more about their accessory structures. Next lesson, we will study the eyeballs! For now, let’s end today’s fascinating topic with a quote about the oblique muscle action from funnyman Jim Carrey:

“Behind every great man is a woman rolling her eyes.”

A deeply grateful,

Outlander Anatomist

photo creds: Starz, www.sussexvt.k12.de.us (warning gif), Medicine: Perspectives in History and Art by R. E. Greenspan, 2006 (Photo O – 19^th century leech jars), Netter’s Atlas of Human Anatomy, 4^th ed. (Photos B – L), www.aapos.org (image of blowout fracture), www.collectmedicalantiques.com (Photo N – image of leech carriers), www.leeches-medicinalis.com/the-leeches/biology (Photo M – image of leech), www.radiopaedia.org (CT image of blowout fracture), http://funny-pics-fun.com (lemur)

July 26, 2015August 31, 2015

Anatomy Fun Facts Coming Soon!

In just two days, Outlander Anatomy Fun Facts. Rupert says look for it!

The deeply grateful,

Outlander Anatomist

July 7, 2015July 7, 2015

“If a Tree Falls – The Ear”

Summertime greetings to all Outlander anatomy students! Anatomy Lesson #24 covered the outer ear so today’s Anatomy Lesson #25 is the Ear – Part 2, or to be more exacting the middle and inner ears.

But first, what does a tree have to do with the ear? The title of this lesson derives from a 300 year old philosophical thought: “If a tree falls in a forest and no one is around to hear it, does it make a sound?” An 1884 issue of Scientific American correctly addressed this question. What do you think? Watch for the answer later on!

And to emphasize the importance of the ear in society, do you ken that the English language is replete with many idioms of all things ear? One website lists 120+ idioms including: a tin ear, all ears, music to the ears, up to the ears in, wet behind the ears, bend one’s ears, can’t make a silk purse out of a sow’s ear (who would try?), cute as a bugs ear (didn’t know bugs had ‘em), fall on deaf ears, in one ear and out the other, turn a deaf ear, and blow it out your ear (here’s to you, BJR!).

Now, onto the lesson. To review, in anatomy lesson #24 we learned that the human ear is divided into three ears: an outer (Photo A- green), a middle (Photo A- yellow) and an inner ear (Photo A- blue). That lesson dwelt almost exclusively on the outer ear. So, now we move to the middle and inner ears.

Photo A

Let’s begin with the middle ears. Each middle ear is housed inside a cavity within one of our two temporal bones. The human skull includes 22 bones two of which are os temporale (Latin meaning temporal bone). The temporal bone is weirdly shaped (Photo B – pink bone). From a side view, it comprises most of the skull around the external acoustic meatus or EAM (Anatomy Lesson #24). The temporal bone also includes the zygomatic arch, part of the cheek bone (Anatomy Lesson # 8) and the gothic-looking styloid process marked by the black arrow (Anatomy Lesson #12). Let’s add a new part of the temporal bone which is pertinent to today’s lesson, the rounded mastoid process.

Try this: Place your fingers behind the pinna of one ear and move downward until you feel a rounded mound of bone; this is your mastoid process. It typically lies just below the level of the EAM or ear hole as Claire called it (ha ha). Its outer layer is compact bone, but inside it is riddled with air-filled spaces. Well done folks!

Photo B

A different image of the skull helps us appreciate the location of the middle ear. With the top of the skull and brain removed, Photo C shows the cranial base. The right side of the image shows the tortuous shape of the bony floor upon which the brain rests. Nerves and blood vessels pass through the many holes in the skull bones. The left side of the image is color coded so once again, the temporal bone is pink. See the bright green area? This is the location of the middle ear – it lies inside the petrous (Latin meaning stone-like) part of the temporal bone, one of the densest bones of the human body.

Photo C

The middle ear is small but it contains a large number of components including tympanic cavity, inner leaflet of tympanic membrane, three bones, the opening of a throat tube, a posterior “attic door,” two wee windows, two tiny muscles, a nerve and a nerve plexus. Wow! That’s quite a list for such a small space! Let’s examine the components.

The tympanic cavity is an air-filled chamber (Photo D, yellow dashed line) inside the petrous temporal bone; its shape is so difficult to describe that many anatomists compare it to a small room with four walls, a roof and floor. So let’s do that: the roof and floor are petrous temporal bone. The outer (lateral) wall is the tympanic membrane. The inner (medial) wall will be discussed shortly. The back wall has an “attic door” leading to the mastoid air cells (see below). The front wall receives the opening of the throat tube or pharyngotympanic or Eustachian tube (photo D) that extends between the back of the throat and the tympanic cavity.

Please understand this: normally, air pressure between the tympanic cavity and the EAM is equal. However, as we climb in altitude, air pressure becomes lower in the EAM than in the tympanic cavity which pushes the tympanic membrane outward causing discomfort, even pain. As we descend in altitude, air pressure is higher in the EAM than in the tympanic cavity which pushes the tympanic membrane inward, again causing pain. Air pressure equalizes on each side of the tympanic membrane when we open the Eustachian tubes: with altitude, air escapes from the tympanic cavity and with descent, air enters the tympanic cavity. Got it? Chewing and swallowing activates a pair of itsy, bitsy, teeny weeny, tensor veli palatini muscles that open the Eustachian tubes to equalize the air pressure. I won’t show an image of these wee muscles because it will clutter the lesson. Just know that they work well unless the Eustachian tubes are congested.

Photo D

Remember the “attic door” in the back wall of the tympanic cavity? It has a longish Latin name, the aditus ad antrum, but the short of it is that the passageway leads to air cells which riddle the mastoid process (Photo E). These little spaces are thought to reduce the mass of the skull bones and provide physical protection.

Photo E

The middle ear bones bring us back to the anatomical rule of three! Three ossicles meaning tiny bones are the smallest bones of the human body. How small are they? Well, all three easily fit on a U.S. dime with plenty of wiggle room (Photo F)! There are three ossicles per middle ear and they are not included in the count of 22 skull bones.

Photo F

The ossicles form a tortuous bridge spanning the tympanic cavity from outer to inner walls (Photo G). Each ossicle resembles the object for which it is named: the malleus (Latin meaning hammer) has a handle firmly attached to the inner leaflet of the tympanic membrane and a head that articulates (forms a joint with) the incus. The incus (Latin meaning anvil) articulates with the stapes (Latin meaning stirrup) and the stapes inserts into the oval window, an opening in the inner wall of the tympanic cavity. Although tiny, the joints or articulations between the ossicles are moveable.

Please understand this: imagination is sometimes required to relate the Latin names to their corresponding anatomical objects. However, ancient anatomists used objects found in nature to name the body parts. The names such as stapes or malleus seem quaint but I actually prefer them to the current naming trend which often includes meaningless words containing lots of “cs”, “xs” and “zs.”

Photo G

The inner wall of the tympanic membrane bears two holes piercing the temporal bone. One hole, the oval window, is plugged by the stapes (Photo H); the other hole or round window is closed by a membrane (Photo H – black arrow). The inner wall has several other features too, but these are beyond the scope of this lesson

Photo H

Let’s stop for a short Clinical Correlation: The oral cavity and throat contain oodles of bacteria (Rupert and Angus consider germs in this hilarious video: Angus and Rupert Go Through The Stones). All is well unless they follow the Eustachian tube into the tympanic cavity where they can set up housekeeping to our detriment. Otitis media (Latin meaning inflammation of middle ear) is a rather common condition which typically includes bacterial (or viral) infections of the middle ear. Over 30 million doctor visits per year in the U.S. are due to otitis media. Symptoms include: pain, pulling at the pinna, irritability, sleeplessness, crying, etc. A trip to the doctor and an otoscope exam is in order (Photo I).

Photo I

Anatomy Lesson #24, showed the photo of a normal tympanic membrane (Photo J – left). But, with otitis media, the tympanic membrane is red, bulging because there is fluid in the middle ear and it hurts (Photo J – right)! Proper treatment is imperative.

Photo J

Unresolved otitis media can lead to mastoiditis (Latin meaning inflammation of mastoid bone). Now, dinna confuse mastoiditis with mastitis which is inflammation of the breast. Och, we are discussing ears, not mammary glands!

Here’s how mastoiditis works: recall that little attic door in the back wall of the middle ear that leads to the mastoid air cells (photo E)? Well, that door is a perfect conduit for bacteria to make their way from the middle ear into the mastoid air cells causing serious health complications in children and adults. Photo K (left side) shows bacterial invasion of the mastoid air cells and its presentation at the body surface (Photo K – right side). Signs include fever, redness, swelling, and tenderness behind the pinna which is pushed outward and forward.

Photo K

A picture is worth a thousand words, so this photo shows a case of mastoiditis (photo L – left mastoid process). Ouch, that hurts!

Photo L

Now back to anatomy. The inner ear is the last and by far the most complex of the three “ears”. At first blush it resembles a mutant squid or snail. It contains both bony and membranous elements. Bony parts include cochlea, vestibule and three (yes, three!) semicircular canals (Photo M- tan structures) filled with fluid (perilymph). Membranous elements (Photo M – blue structures) are suspended within the bony parts; these are the cochlear duct, utricle, saccule and three semicircular ducts; these are surrounded by perilymph and are filled with endolymph. Only the cochlear duct is involved in hearing, the utricle, saccule and semicircular ducts are necessary for balance and equilibrium.

Photo M

The cochlea and its cochlear duct spiral 2.5 times much like a snail shell. Within each cochlear duct lies the organ of Corti, a strip of 15,000-18,000 specialized “hair” cells arranged in rows like soldiers. “Bristles” project from the surfaces of the “hair” cells although these are unlike the hairs of skin. When examined by scanning electron microscopy (Anatomy Lesson #6), the bristles resemble the pipes of an organ (Photo N – cat hair cells). The bristles are covered by a gelatinous membrane (not shown in Photo N). The organ of Corti is also our organ of hearing.

Photo N

The following is a simplified version of how we hear, as the full vocabulary and structural and functional details would fill yet another anatomy lesson. Sound waves travelling through the air are gathered by the pinna and EAM; they strike the drum-like surface of the tympanic membrane pushing it inward with a thrust equal to the intensity of the sound. Ergo, loud noises push the eardrum inward more than soft sounds. The tympanic membrane vibrations are transferred through malleus, incus and stapes. With each vibration the stapes pushes inward at the oval window creating corresponding shockwaves through perilymph and endolymph of the cochlear duct (Photo O – black arrows). Movements of the fluids rub the bristles of the hair cells against the gelatinous membrane creating an excitation which is transfer to nerve cells forming the cochlear nerve (Photo O). The cochlear nerve joins with the vestibular nerve (see below) to form Cranial Nerve VIII (vestibulocochlear nerve). Impulses of each Cranial Nerve VIII follow auditory pathways into the brain. Hair cells near the base of the cochlea detect high-pitched sounds, such as ringing of a cell phone; those closer to the apex detect lower-pitched sounds, such as barking of a large dog.

Photo O

Electrical signals carried by the cochlear nerve make their way to the primary auditory cortex of the brain (Photo P – pink zone) where electrical signals are converted into “sounds” that we learn to recognize and understand.

In summary, outer, middle and inner ears work together to transfer sound waves through air (outer ear), solid (middle ear) and liquid (inner ear) where the good, good, good, good vibrations are converted into electrical signals that make their way to the brain for interpretation of sound. Go Beach boys!

Photo P

Do you recall this lesson began with “If a tree falls in a forest and no one is around to hear it, does it make a sound?” Take a moment to think of the answer and then read on.

The answer to this philosophical riddle is that if a tree falls in the forest it creates sound waves but a receptor must be present to convert those sound waves into sound. If any creature is present with an organ than can perceive and interpret sound waves, then the falling tree does make a sound otherwise it only makes sound waves. Make sense? Good!

Now, every anatomy lesson must tie into all things Outlander and hearing is no exception. So next is a jolly good quote from Outlander book when Claire tells Jamie she is from a waaay different time zone (Starz episode 111, The Devil’s Mark). Well, Jamie knew there was something unique about this braw and bonny lassie!

“Do you know when I was born?” I asked, looking up. I knew my hair was wild and my eyes staring, and I didn’t care. “On the twentieth of October, in the Year of Our Lord nineteen hundred and eighteen. Do you hear me?” I demanded, for he was blinking at me unmoving, as though paying no attention to a word I said.

“I said nineteen eighteen! Nearly two hundred years from now! Do you hear?” I was shouting now, and he nodded slowly. “I hear,” he said softly.

Hmmm, Jamie is thinking: I ken now why the Sassynach didna take to my leather belt spankin’! It also ‘splains her twitchy-witchy “know how.”

Now we must move on to how the inner ear provides balance and equilibrium. Our ability to balance is independent of outer ear, middle ear and cochlear parts of the inner ear but it is dependent on function of the three semicircular ducts (Photo Q – bone removed). The semicircular ducts contain endolymph and each bears an ampulla, a swelling at one end (Photo Q – red arrows). Each ampulla contains a patch of “hair cells” similar to those of the organ of Corti. Once again, the bristles are covered with a gelatinous membrane.

Anterior and posterior semicircular ducts are oriented vertically at right angles to each other. The lateral semicircular duct is slightly off the horizontal plane. Orientation of the ducts cause each duct to be stimulated by angular rotation of the head in a given plane.

Photo Q

Turning your head from left to right sides (as in no) moves endolymph in the lateral semicircular duct. Nodding your head (as in yes) moves endolymph in the anterior semicircular duct. Moving your head to touch one shoulder or as in doing a cartwheel moves endolymph in the posterior semicircular duct. In aviation terms, the semicircular ducts are oriented such that they detect pitch, roll and yaw.

Here is how the semicircular ducts work: As the head moves in angular rotation, endolymph moves in the opposite direction bending the gelatinous membrane (cupula) and exciting the hair cells (Photo R). The hair cells transfer the signal to nerve cells of the vestibular nerve (part of Cranial Nerve VIII). The signal is carried to the brain which interprets it as angular motion of the head. The information can be used to activate various muscles to adjust the head and/or body positions.

Photo R

The final anatomical elements of the inner ear are utricle (Latin meaning leather bag) and saccule (Latin meaning money bag – Dougal is into this one!) located between the semicircular duct and cochlear duct. These elements are also filled with endolymph (Photo S) and are designed to detect changes in linear acceleration or linear deceleration.

Photo S

Utricle and saccule each contain a patch of hair cells with surface bristles (Photo T – bullfrog hair cell) covered by a gelatinous membrane (absent in Photo T). The hair cells of the utricle are oriented horizontally and those of the saccule are vertically oriented.

Photo T

Seated atop the gelatinous membrane are wee otoliths (ear stones or ear rocks) made of calcium carbonate (Photo U); these add weight to the gelatinous membrane thus enhancing our sense of gravitational pull.

Photo U

The utricle and saccule work this way: As our head undergoes linear acceleration or linear deceleration (forward, backward, upward, downward), endolymph, the gelatinous membrane and otoconia move in the opposite direction (Photo V). This bends bristles of the hair cells causing them to activate nerve cells of the vestibular nerve of Cranial Nerve VIII. The electrical impulses are carried to the brain. The utricle detects horizontal changes and the saccule detects vertical changes in linear movements of the head. This information arrives at the brain which then determines if and how much the head is tilted and if the body needs to be reoriented in space.

Photo V

This brings us to the end of today’s important lesson but we must tie balance and equilibrium into Outlander. Here are a couple of great quotes from Outlander book. The book quote and the Starz images (Starz, episode 108, Both Sides Now) don’t quite match because the book scenarios weren’t filmed. Nevertheless, it is fun and you will get the idea. The first scene takes place as Frank and Claire descend from Craigh na Dun after watching the Druid’s dance. Frank, the soon-to-be Oxford professor, is so absorbed in thought he doesn’t watch where he plants his feet!

“He dropped into one of his scholarly trances … The trance was broken only when he stumbled unexpectedly over an obstacle near the bottom of the hill. He flung his arms out with a startled cry as his feet went out from under him and he rolled untidily down the last few feet of the path, fetching up in a clump of cow parsley… “Are you all right?” … “I think so.” He passed a hand dazedly over his brow, smoothing back the dark hair. “What did I trip over?” “This.” I held up a sardine tin…”

Compare and contrast Frank’s stumble-tumble with Jamie’s sure footedness (Outlander book). In this scene, it is nighttime and Jamie unerringly hauls Claire through the night:

“Jamie kept a tight hold on my arm, hauling me upright when I stumbled over rocks and plants. He himself walked as though the stubbled heath were a paved road in broad daylight. He has cat blood, I reflected sourly, no doubt that was how he managed to sneak up on me in the darkness.”

Yes, Jamie has grace, balance, and equilibrium (Starz episode 104, The Gathering). Nothing will trip-flip this kilt! Hang on tight, Claire! Snort!

You may have seen this arabesque in the teaser but let’s appreciate it anyway. Jamie throws water on burning hay, a fire set by a Watch weasle! Our highlander fireman even makes tossing water a thing of beauty. Balance and equilibrium on one foot; 17th century ballet!

At last, the time has come to report the results of Lesson #24 and the Pinna Poll! Six images of pinnae from the Starz cast (episodes #103, #109, #115, #116) were shown and votes tallied. All the ear flaps are fabulous!

Not sure if you are surprised, but the winner is:…………..drum roll………………..Jamie! Congratulations Big Red! And it was an honest count, too; no stuffing of the ballot box! Jamie garnered 38% of the votes while the remaining five pinnae were in almost a dead heat with a slight edge by bad boy BJR!

Great comments were shared by many readers including these: exquisite, lovely, charming, manly, rugged, beautiful, elfin-like, fawn-like, nibble-worthy, snuggle-worthy, elegant, awesome, symmetrical, balanced, proportionate and yum! Let’s thank our six wonderful characters and all of you for playing the Pinna Poll!

That’s it for the ear. Complex and elegant! Oh, and a word to the wise: keep music turned down a notch or two. Over the years, hair cells of the organ of Corti become damaged by excessive noise. For years, the damage has been considered irreversible although a recent study shows some promise using a gene-activating drug regime. Stay tuned.

Closing with this fun poem from Mr. R’s World of Math and Science:

An ear splitting sound!

A crash and a boom!

Ringing so loudly,

It shook the whole room!

But I didn’t hear it,

I couldn’t at all,

My left and right ear,

Had gone to the mall!

My left and right ear,

My organs that hear,

Had gone to go shopping,

And that’s what I fear…

Without my 2 ears,

That spectacular pair,

I can’t hear sound waves,

Move through the air!

The deeply grateful,

Outlander Anatomist

Photo creds: Starz, Basic Histology, Junqueira & Carneiro, 11^th ed., Concise Histology, Bloom & Fawcett, 2^nd ed., Netter’s Atlas of Human Anatomy, 4^th ed., Clinically Oriented Anatomy, 5^th ed., www.aviationknowledge.wikidot.com (ampullae), www.clearwaterclinic.com (otoliths), www.fairview.org (mastoiditis), www.kids-ond.com (ossicles), www.mhhe.com (ampula hair cells), www.sciencepoems.net (Mr. R’s ear poem), www.student.com (ossicles with inner ear), www.teachmeanatomy.info (mastoid air cells), www.otopathologynetwork.org (ossicles on dime), www.wallpaper.com (fallen tree), www.wikipedia.org (mastoiditis with subperiosteal abscess)