Food for thought

So this post will be a little off topic. As I’m sure you’ve noticed by now most of my posts at the moment are rehashes of what I’m learning (anatomy of the head, just incase it wasn’t obvious enough!)

However some recent reading has brought up something that I felt like sharing.

I’ve always been interested in animal welfare. Not surprising for someone who wants to be a vet you might say. Well perhaps, but it wasn’t until I started on this course that I realized just how difficult it is to establish what is good welfare is, how to measure it and how to ensure that it is protected.

In class we learned a good basic way of measuring the welfare of an animal species. The Five Freedoms (which can be found on almost every animal welfare site) were established by the Brambell report for the UK governments Farm Animal Welfare Advisory Committee in 1967.  They have been elaborated upon since then and are defined as.

1.  Freedom from thirst and hunger - by ready access to fresh water and a diet to maintain full health and vigour.

2. Freedom from discomfort - by providing an appropriate environment including shelter and a comfortable resting area.

3. Freedom from pain, injury, and disease - by prevention or rapid diagnosis and treatment.

4. Freedom to express normal behavior - by providing sufficient space, proper facilities and company of the animal's own kind.

5. Freedom from fear and distress - by ensuring conditions and treatment which avoid mental suffering.

These are a great way to establish basic standards by which to measure whether or not a welfare standard has been met. As well it actually actively describes a standard that can be recognized and in many cases measured.

However welfare is expensive……. Very expensive.

And we like our food affordable (read: cheap).

In a recent conversation with an animal welfare scientist she had this to say on the matter:

“Cattle are so large that consecutive doses of analgesics may be a substantial cost, and then there are concerns re withdrawal periods and the cost of maintaining a now healthy animal during this period. In the case of sheep and footrot, the problem may also be their low market value. In both cases, one can argue that being pain-free improves recovery, weight gain and incidence of respiratory disease (in the case of calves and dehorning, as I recall--I'm not up to date with literature now). Yet, despite that, our obsession with money and having cheap food creates cashflow problems for many farmers e.g. in 2006, a farmer told me that he was paid 17p per litre for his milk and it cost him 21p per litre to produce...”

This is just a little depressing. Essentially our desire for accessible foods has created a welfare (crisis?) issue in our farming industry. Can we really take our meals at another beings cost?

Recent changes to animal welfare law bringing standards up have cost the industry greatly. For instance the changing over to enriched cages in the poultry industry by 2012 has cost the industry around 16 million euro to support the changes for the farms affected by the change. One poultry farmer I had the chance to work with told me that the changes were cost him £100 000.00. That's on top of the cost of running the business, marketing and general production related costs. What's more is this is a cost that he will not really recoup through his product as the change is mandated but the price will not increase (necessarily) as a result.

There is some good news on this front however, in the same conversation she went on to say that a colleague of hers who works in farm animal practice had told her that the farms in that practice who supplied Waitrose and Marks and Spencers were content, paid and treated fairly.

Why do the other national supermarket chains not follow suit. I will do some more reading up on this but I feel that they could learn something here.

The question now becomes, what matters more? How we feel about what we eat, or how much it costs?

" In 2010, my impression from the sidelines is that the economics of the survival of the farm animal may trump questions of their being pain-free, largely because, as consumers, we are beguiled by the idea of cheap food (cheap everything, in fact... We seem to know the price of everything, and to have forgotten the value of having nothing). "

Perhaps we need to focus more on the value of what we have, rather than what it costs.

Perhaps this is easier to say than to do….. but I sincerely hope not.

Getting down to the bare bones of it all...

WELLLLLL today (as I was at a loss of where to go to next) we're going to hit some of the basics (well structurally that is). Today's discussion is the skull.

As I'm sure you know (in humans that is) the skull is made up of many bones. Well, it is the same for animals. The rough anatomical regions of the skull are the face, mandible and cranium (or "brain box", though that term sounds somewhat unprofessional at the best of times).

The skull is formed from two kinds of bones (embryologically speaking). The bones of the skull are endochondral bones (from cartilaginous structures and are usually unpaired) and intramembronous (From mesenchyme of the embryo (I'm sure I'll get around to discussing what that is at one point but basically it's a type of embryological tissue). The intramembranous bones are usually paired and are usually plate like.

Each of the bones shown in the picture of the cat skull are paired (each have a partner of the same shape on the opposite side of the skull).

Now bones, though solid also have quite a few holes in them (to allow for the passage of different nerves and sometimes blood supply). Not shown here but usually found in the maxilla near the orbit (eye socket) is a hole called the infraorbital foramen. Through this hole a nerve leaves the skull to innervate the upper lip and the whiskers of the animal.

Also not shown here but perhaps in another image...

Ah, here we are.. in the mandible there are some more holes. The ones shown here (the mental foramen) is where the mental nerve (a branch of the inferior alveolar nerve of Cranial Nerve V, The trigeminal nerve... sorry for that mouthful) leaves the skull. It enters the mandible (or lower jaw) on the inside of the mandibular body (about opposite and just below where the marker is pointing to the masseteric fossa). Nerves, when running through the bone do not only innervate the tissues, but also gives some sensation within the bone. This nerve here, the inferior alveolar nerve, sensitizes the lower teeth. It's partner the maxillary alveolar nerve sensitizes the upper teeth (this is why tooth
infections or chips can hurt!).

The bones of the palate (hard palate which underlies the softer tissue you can feel with your tongue (in your mouth that is) are also part of the skull. There are all sorts of bones in the head as I'm sure you can now appreciate.  Issues that can happen in this area is a failure of the secondary palate to close (the bony palate) it is called an oronasal fistula or cleft palate and leaves an open connection to the nasal cavity from the roof of the mouth. This is usually first picked up in puppies or kittens as milk comes out of their noses when they try to feed. Cleft palate is both serious (great risk of them breathing in milk) and hard to fix. Surgery here is the only option though ay not always be successful. If the primary palate fails to close it is called a cleft lip (which is more cosmetic than damaging though there is a possible increase in nasal infections). Both of these need a surgical fix.


Also visible on this skull is the incisive foramen (or palatine fissure). This is where the vomeronasal organ (or Jacobson's organ) sits. That gland is a really neat sensory gland (you've probably seen horses flip their lips upwards and make a funny face, this is called Flehmen and it's them utilizing their vomeronasal organs to scent pheromones or something new). Usually this is described in stallions "smelling" a mare in heat but both sexes do this when they smell something new, or something interesting. Flehmen forces air into the nasal cavity through slits in the hard palate forcing it through the vomeronasal organ.
Other animals (ie cats) have this ability as well.



The back of the skull also comes into play. It's where the spinal cord leave the brain to be covered with, well, spine. It too has some clinical implications. Most recently issues with the bones around the foramen magnum (big hole where the spinal cord leaves through) have been implicated in a disease recognized in the dog breed the Cavalier King Charles Spaniel.  In this breed, due to selective breeding to create a smaller dome shaped head the occipital bone is too reduced and compresses the cerebellum against the foramen magnum, as a result the trapped fluid creates lesions in the brain, neuralgia (nerve pain) and can result in the dog being in a great amount of pain. The disease itself is called syringomyelia.

There are also small little bones (associated with the skull.. well sort of) in the area of the throat. This is called the hyoid apparatus and is what allows great movement of the tongue (important to vocalization... especially in human language). It's a good idea to know both what this is and where it is so that when you radiograph a dog (or cat) you don't go "oh look at the size of that bone they've swallowed". Or alternately... it's not a great idea to stick your finger down it's throat and try to pull it out ("that's not a stick, that's suppose to be there!")

Finally.... Head shapes.. Just like ears they come in all shapes and sizes. In dogs and cats they are most commonly described as Dolicocephalic (long pointy noses like greyhounds and siamese cats), Mesocephalic (like the german shepherd and the common domestic shorthair cat) and Brachycephalic (bulldogs and persian cats). As with everything else, there can be clinical implications here too.

Brachycephalic dogs (those cute squishy faced things) tend to have multiple problems associated with the reduced skull shape. They can have breathing difficulties, popping out eyes, bad teeth and bad skin. Essentially, those skin folds are not due to excess or "just plain wrinkly skin" but due to such a reduced skull shape. They have the regular amount of skin for a dog, just not enough skull to go underneath it. They have such issues as stenotic nares (closed up nostrils) because of too much cartilage or soft tissue in this area for the underlying skeleton and therefore have trouble breathing through their noses. They have trouble breathing period due to an overlong soft palate (again for the size of their skull) which then overlies the larynx causing them to make that snorting snuffling nose as they try to breathe properly. They have issues with their bite (mallocusion) an extreme underbite that usually results in an increase in incidences of dental disease. The have popping out eyes (exopthalmic eyes) due to the reduced bone around the eye socket that can then lead to increased ulceration or even proptosis (eyes popping out!). and also they tend to have an increased risk of skin disease due to all those wrinkles trapping dirt and bacteria (definitely have to wash these little faces at night).

Riiiight, so it may not be a dog ... 

but I felt that Pacman deserved at least a nod in the reduced skeleton department

So in conclusion, there is quite a lot going on in the head and it's only going to get busier as you add on those layers (muscle, nerves and other tissues). But that said, going down to the bare bones of it all is a good way to start.

I can't hear you!

How about ears... Shall we start on the inside and work our way out?

There are essentially 3 major parts to the ear. The inner, the middle and the outer. Wow, crazy naming there eh? Lets start at the middle. This is where all the good stuff is (the tiniest bits of your ear, the microscopic bits that actually allow you to hear). The inner ear is essentially formed from the semicircular canals, the vestibule (saccule and utricle) and the cochlea.

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The cochlea looks like a snail shell and holds the cochlear duct (in which the organs of sound, the organ of corti are contained). 

 If you cross section this area you get many round windows (with scala vestibuli and scala tympani both holding perilymph separated by the scala media that has endolymph and houses the organ of corti). 

The organ of corti house hair cells lightly covered by a tectoral membrane. Vibration of this membrane deflects the hairs and the electrical impulses created by this deflection are passed along Cranial Nerve VIII (CN VIII = vestibulocochlear, or cochlear nerve) to the brain. This is what we and other animals "hear".

Moving outwards from this section is the vestibule of the inner ear, which forms the Vestibular system (imagine that!). This is made of the saccule and utricle respectively. This area houses the macula and otoliths ("ear stones") which are calcium carbonate crystals (not stones at all which I found a little disappointing). The macula and otoliths allow for recognition of static balance (balance when the head is still). The macula/ otoliths in the saccule recognize balance when the head is positioned horizontally and the ones in the utricle recognize balance when the head is held upright. So when the head is moved forwards and backwards (in respect to upright position with gravity) the Utricle recognizes what's going on, alternately when the head moves from side to side in the same situation the Saccule "knows" where you are. Together they can also recognize linear acceleration and deceleration (if you start to run or leap up and down).

Basically this works by the otoliths pulling on the hair cell = a nervous signal is created and a pulse is sent down CN VIII and your brain does the rest. If there is no pull there is no signal sent. So essentially the movement of the head is what creates the deflection of the hair cells and results in a signal being sent to the brain to let it know what's going on. Move your head = move your hair (cells) = lets your brain know you're moving!

Also in this area is the cristae and cupola. This apparatus allows for recognition of circular movement of the head (rotational acceleration and deceleration). It works just like the macula and otoliths (minus the stones which weight the gelatinous mass (so to speak). These cupola are found in all ampullae (where the semicircular canals meet the utricle) and in these positions allow for recognition in all planes of orientation (granted, being in the presence of 1g gravity is key here). Again movement of the head results in the cupola bending the hair projections from the hair cells and yet more information is sent down the CN VIII about your movements. This is the best sort of big brother there is.

Here's a cool cover of what Nasa says about your (inner) ear in space http://www.nasa.gov/audience/forstudents/9-12/features/F_Human_Vestibular_System_in_Space.html

So now for the Semicircular canals. What do those do? Well along with the Utricle they house the endolymph and cupola that allow for recognition of circular movements (housed in the ampulla of the semicircular canals where it meets the utricle).

Now for the clinical aspect.. Basically if something goes wrong here, you're deaf..... permanently.

Moving on: the mechanics of hearing. This involves the middle ear, tympanic membrane and covers the transmission of sound waves to the inner ear (the actual sense organ).

Mechanics of Hearing

1. Ear Drum vibrates,
2. Ossicles vibrate
3. The stirrup pushes the oval window in and out
4. Perilymph moves
5. Pressure waves transmit from scala vestibula and scala tympani to the endolymph of scala media
6. The basilar membrane deflects (hair bundles bend and hair cells convert the mechanic vibration stimulus to an electrochemical signal
7. This signal travels to the brain via CNVIII (auditory nerve in this image)

Now this breakdown of the mechanics of how you hear included some structures not yet mentioned. So here they are.

First: the Ear Drum (or tympanic membrane), now depending on who you talk to this is part of the middle ear or the outer ear (basically it's the marker of the boundary between them). It's where the sound transmits from the outside of an animals body to the processes that allow them to "hear".

The bones (ear bones or ossicles) that allow this process to happen are as follows: Malleus (the hammer), Incus (the anvil) and Stapes (the stirrup). These bones are linked together by synovial joints and transmit the movement of the ear drum to the inner ear.

Also in this area are the spaces (which as our anatomy professor is fond of pointing out, all have names). The tympanic bulla is the round space (can be seen as is housed by a round projection off the base of the skull) and houses... well... apparently nothing. It is just the space. However if it does get something in it (like infection) it can drain via the Eustachian tube to your pharynx. Yummy. It also allows for air to be equalized on either side of the tympanic membrane (or ear drum) which would explain that "popping of your ears" during pressure changes.

A few things can happen clinically here.

1) Otitis media: a middle ear inflammation or infection. Pus can collect in the bulla (shows up on radiographs). You'll also see your dog or cat tilting their heads towards the affected side. This can happen because of viruses or perforation of the ear drum amongst many other possibilities. It can happen to anyone.

2) Horner's syndrome: This is a neat one (at least I think so). It usually stems (in relation to this position of the anatomy) from prolonged middle ear infections. Essentially the inflammation and build up of pus put pressure on a nerve that is completely unrelated to hearing -> The Facial nerve (CNVII) or the sympathetic fibres of the cervical ganglion. Basically you can get the symptoms from damage to the facial nerve in other areas as well but we are talking about the middle ear here!

The damage to CNVII results in facial paralysis, constriction of the iris, drooping of the upper eyelid and the displacement of the nicitating membrane over the eye on the affected side.

Sooooo finally the OUTER EAR!!! This is the bit that we all see (and that dogs usually love to have itched for them). This includes the Pinna (outer ear/auricular/chondral cartilage) to funnel sound towards the external auditory meatus (the ear canal) which carries sound through the annular cartilage (a ring that links the cartilaginous parts to the internal bony meatus of the external ear).... now if that's not a mouthful I don't know what is!.... 

All of this ends on the tympanic membrane (see I told you it's either inner or outer ear depending on which direction you come from).

The pinna is the cute part of the ear... Well maybe not in Lulu's case here.... But usually it's considered the cute bit!

And they come in all shapes and sizes....

Seeing is believing...... sort of

So when starting this blog I hadn't really thought about how hard it is to deliver what I'm learning in an interesting way. I mean I find it interesting but that's not to say that anyone else does.

Soooo lets just start anyway.


The eye.. It's actually kinda a neat structure... and one that is surprisingly hard to cut on dissection.

The adult eye has three tunics. The inner layer is the retina, the middle layer is the uvea (vascular or choroid layer) and the outer is a fibrous layer.

At the back of the eye is a spot called the fovea centralis: this is the area that the visual axis meets directly (instead of at the optic nerve like one would think). This is the area of clearest sight and only has cones.

Dogs and Cats have both rods and cones, however the ratio is about 95% rods to 5% cones. This means that dogs and cats can see lots of light and shade but not much by the way of colour, though they do have some.

Now for the important bits:
The Retina: the light sensitive layer. This is where the photoreceptor cells are, essentially the key to sight. The ganglion cells lie here (which will run to the optic nerve allowing for the brain to recognize what it sees).

Clinically there can be a few issues in this location:

1) Detached retina: you may have heard of this before. It is pretty much what it sounds like, essentially the retinal layer has detached from the choroid/sclera. Animals with a detached retina depending on severity have little to no vision in the affected eye. There are a few different causes (ie a blow to the head, bleeding in the eye wall or damage to the vitreous humour) however it can also be caused in clinics. Sometimes seen in cats is a detached retina due to a spike in blood pressure (sometimes happening during surgery).

2) Another is Progressive Retinal Atrophy or "night blindness": this is sometimes seen in specific breeds (ie the Irish setter and the abyssinian cat). Basically the blood vessels progressively atrophy and pupils will dilate in order to increase the light into the eye (in order to see). This results in vision during the day, but lots of bumping around during the night (as there is too little light for even dilation of the pupil to compensate for).

Tapetum Lucidum. This I have to say is my favourite layer. On dissection it is a beautiful iridescent blue and turquoise and it's what allows animals to be able to see at night (it's also what gives the animals in your car headlights glowing eyes). This layer lies between the pigmented layer and the choroid and it's cells are light reflecting in order to allow more light to reflect against the photoreceptors at the back of the eye.

The eye to the right is from a cow, it is the back half of the dissected eye. The milky white portion at the bottom is the retina (still attached at the area of the optic nerve). The blue/green portion itself is the tapetum lucidum.

Now for the lens. This is a surprisingly strong and solid structure (at least surprising to me who was used to thinking of a lens as well... a contact). The lens is a kind of oval shape that is made of many layers closely wrapped (much like an onion). This is suspended from muscles on the sides of the inner eye (in the ciliary body) by suspensory ligaments. The ligaments and muscles of the ciliary body are what allow you to focus on what you are seeing. For distance vision the ciliary body relaxes and the ligaments are taut allowing the lens to lie flat. For close vision, the ciliary body tenses, the fibres slacken and the lens is round.

So what can go wrong here? well most commonly are cataracts: the clouding of the lens due to age (that old dog eye look), genetics or diabetes (the side effect of sorbitol accumulation). Essentially these are irreversible without surgery. Cataracts can also be accompanied by lens luxation (displacement of the lens to the anterior chamber). Basically with cataracts, transparency is reduced and vision is affected to some degree. The change however is usually gradual over time and the reduction in vision may or may not be noticeable.

The Aqueous humour: this is that liquid just inside the cornea of the eye (in the anterior chamber). It is formed by the filtration of blood plasma by the ciliary processes and is what provides the iris with nutrients (it feeds it). The humour is formed near the ciliary body, moves towards the pupil and out towards where the iris meets the cornea (there is a venous plexus there that drains it from the anterior chamber). It is constantly formed and removed (keeping the meal going!).

The most common issue here is glaucoma, a raise in intraocular pressure. Usually caused when the drainage of the aqueous humour is blocked at the limbus. It can cause blindness indirectly (the raised pressure impedes circulation, killing off retinal cells in the eye) and can compress or even damage the optic nerve. Of note, in cats this can be a symptom of chronic renal failure (because of hypertension). This can be treatable by drugs (those that will decrease humour secretion or increase the drainage of it)

The cornea! Which most of us are familiar with at some point in time. It has many nerve endings and is very sensitive (hence why it hurts so much when you have a microscopic speck in your eye!). This is where light focuses. It's surface is a single layer of squamous epithelia and thankfully (in those times that you get a scratch on your eye) it repairs itself very quickly (cell turnover within 24 hours).

Quite a few things can go wrong here, some dangerous, some not and some just plain gross (ie epibulbar dermoid: hairs growing on the cornea surface.. Thankfully not really a problem and can be dissected off but ewww...)

For those that have horses a corneal ulceration may be familiar. Especially if the ulcer allows further entry of bacteria into the chamber of the eye (yes I am very familiar with this one.. my own little pony pulled out this trick also known as a stromal abscess).  It can be caused by scratches (infected ones) or even more chronic conditions like dry eye (or keratoconjunctivitis sicca, an autoimmune disorder causing failure of tear production) if this happens to your pet better get some artificial tears for it before you get an ulcer!

Just for the record this horse here doesn't have a green infection. That's the flourescent dye marking the area of the ulceration (in order to diagnose the problem).

Well I think I'll call it a day here. I know for you keeners I missed out on discussing conjunctivitis but perhaps next time...

Starting out....

So why am I here? Well, like any good student I had many other and more important things to do (ie studying, reading or even sleeping) but instead like most children of the internet generation, I felt a inexplicable need to share my thoughts..... well sort of.

Why do I want to become a vet? I'm sure most Vets have been asked that question at one point or another in their lives. Well for me? I just do. So here I am, in another country, another culture and another time zone than the one I am used to.

Basically I've decided to start a blog to discuss things I'm learning and what I think about them. I find the UK style of teaching/evaluation very different from what I am used to, so that may come up. I also find the culture here (especially in terms of animal welfare and the idea of "freedom foods") interesting, so that too may feature in this blog at some point. Alternately this could become a discussion on my confusion around the current student culture in the UK (the much less academic form..... and usually involving lots of alcohol and the occasional pile of vomit).  Essentially this is basically a way for me to "revise" what I'm learning in a very different way (hoping that what I share with you will stick with me in the long term) or at the very least unload.

So hopefully this won't put you to sleep, or if it does I'm at least hoping that's what you were looking for.