Cases

Only the nose knows

We all know the nose is an important organ, particularly for the sense of smell.  Within the nose of mammals is a labyrinth of bones called the turbinate bones.  These are covered in a thin layer of tissue in which there are areas with sensory centres and these communicate with sensory nerves (the olfactory nerves).  But this is not all the nose is capable of;  Here we discuss how pathology affects the biomechanics, and vice versa, within the nose…

The concha (turbinates) are scrolls of bone lined by epithelium within the nasal cavity

Concha (turbinates) are scrolls of bone lined by epithelium within the nasal cavity

The extra layers of tissue supported by the turbinates increases the surface area within the nose massively. As air is breathed in, it is warmed, humidified and filtered over the surface of these scrolls of tissue.  Breathing through the nose can be altered to change the pathway the air takes – either to increase the amount going to the lungs, or to the sensory areas of the nose for smelling (olfaction), by sniffing.

Temperature control (thermoregulation) is important when it comes to the replication of some viruses.  The cooler environment of the nose is favoured by the rhinoviruses that cause the common cold, for example.  When body temperature decreases, the immune system is less able to get rid of virus infected cells .  Some viruses prefer to replicate in cooler temperatures. ‘Cat flu’ (feline viral rhinotracheitis, caused by feline herpesvirus-1) infected cats can pass these viruses on to kittens, or to ill animals who are less able to control their body temperature.  In fact, a fever might actually be the way the body has evolved to reduce the rate of replication of some of these viruses.  Severe inflammation can destroy the turbinates, but even very mild swelling can cause the turbinate bones to breakdown and remodel.

The severe inflammation has destroyed the turbinate bones, and the nasal cavity is filled with pus.

Severe inflammation has destroyed the turbinate bones, and the nasal cavity is filled with pus (nose of a cat with ‘cat flu’).

As the air makes its journey through the nose, wind pipe, and airways of the lungs, the path splits into smaller and smaller channels.  There is mucus within the nose, windpipe and larger airways within the lungs, which act to trap particles, which are sent back up to the mouth to be swallowed, sneezed or coughed out of the respiratory system.  Toxic substances, which could potentially severely damage the little air sacs (alveoli) of the lungs, are diluted by repeatedly coming into contact with the mucus over the surface of all of the divisions.

These lungs have been severely damaged by the animal inhaling stomach acid from vomiting.

The lungs of this dog have been severely damaged inhaling stomach acid after vomiting.

The scrolled nature of the bones causes inhaled air to create a vortex, similar to the wing-tip vortex seen at the ends of wings in flight.  This causes any particles to be thrown to the outside of the vortex (centrifugal).  This is particularly fascinating; In order for the immune system to actually recognise foreign material or infectious agents, they have to come into contact with the immune cells.  The vortex brings the particles within the inspired air into contact with the cells lining the nasal cavity.

The vortex at the end of a wing is similar to the vortex created within the nose due to the scrolls of turbinate bones

The vortex at the end of a wing is similar to the vortex created within the nose by the scrolls of turbinate bones

Tumours of the nose can destroy the turbinates as they invade and grow through the nasal cavity.  This gives bacteria and viruses ample opportunity to infect the damaged nose.  Some tumours are particularly nasty and may even grow from the nose, through the skull and into the brain.

This tumour, a fibrosarcoma, has grown from the roof of the mouth into the nose, destroying the tissue as it goes.

This tumour, a fibrosarcoma, has destroyed the roof of the mouth and grown into the nose.

 

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What's this?

What’s this? #3 Assume the cow is a sphere…

What was up with that beef ball? Was it those pesky physicists again, trying to validate their theoretical model?

It’s actually a globosus amorphous (not “amorphous blobosus”, as I used to so confidently tell people…) — where a fertilised egg doesn’t develop properly in the womb. Instead, it tends to form a ball of fat wrapped up in skin, and feeds parasitically on the umbilical cord of its twin (you might also know someone like this).

Umbilicus (I bet it would have been an outie bellybutton)

Umbilicus (I bet it would have been an outie bellybutton)

Also known as an ‘acardiac acephalic twin’ (acardiac = without heart, acephalic = without brain) or ‘acardiac amorphous twin’, these form as a result of abnormal development of one of a pair of twins (or septuplets!). They most commonly occur in cattle, but also occur in several other species such as goats, sheep and horses.

The normal twin is usually called the ‘pump twin’ because it provides the oxygenated blood to the abnormal twin which has no heart of its own.  Blood comes from the mother, via the placenta to the normal twin.  It then leaves the normal twin and, instead of going back to the mother, travels through the acardiac twin.  BUT the blood actually flows the wrong way around the acardiac twin as a result of this hijacked perfusion.  The blood flows to the intestinal arteries first, and because the blood has already flowed through the mother and normal twin first, it is super low in oxygen.  This is why, if anything develops at all, it is usually only the hind limbs and some organs — the parts that got any oxygen.

Our little guy only managed an eye socket and a piece of cartilage, which is why it was so shapeless and easily mistaken for a guinea pig or plush pathogen.

Sock it to me!

Sock it to me!

Piece of cartilage

Piece of cartilage

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Cases

Osteosarcoma

Sad face in the bone surrounded by the bone tumour cells.

Sad face in the bone surrounded by the bone tumour cells.

Last week,  ‘All Creatures Great and Small’ posted an x-ray of the leg of a poor dog with a bone tumour.  Unfortunately, this is quite a common tumour, and we diagnosed one in another dog a couple of days later.  This type of tumour is called an osteosarcoma (osteo = bone, sarcoma = a group of malignant tumours).

You can see the new bone formation in this picture of an x-ray from another dog with osteosarcoma.

You can see the new bone formation in this picture of an x-ray from another dog with osteosarcoma.

They form from the cells that produce bone during life.  There are a few cell types involved in bone formation.  Osteoblasts are cells which divide and mature to form osteocytes.  Osteocytes produce the bone itself.  Osteoclasts are cells which eat bone so that old or damaged bone can be replaced with new bone.  Any of these cells can become tumours.  So some of the tumours will produce lots of bone, whilst others will eat away at the bone.

Tumour cells (blue arrow) invading into a vessel (orange arrow indicates the wall of the vessel).  Black arrow: island of bone formed by the tumour cells.

Tumour cells (blue arrow) invading into a vessel (orange arrow indicates the wall of the vessel). Black arrow: island of bone formed by the tumour cells.

These tumours grow fast and can cause the bone they are growing in to break, known as a ‘pathological fracture’.  They are very painful and spread (metastasise) around the body by first invading vessels.  Osteosarcomas most commonly spread to the lungs where they can cause Marie’s disease.  Due to the painful nature of these tumours, which often occur on the legs, amputation is common to relieve the pain.  Unfortunately the microscopic tumours, which may have already spread around the body, are actually thought to grow faster once the primary tumour is removed…

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Cases

Monster tumour!

When an animal develops from the fusion of an egg and sperm cell, the first cell will divide and divide until a large ball of cells is formed.  These cells will go on to produce the entire animal, the placenta and membranes that surround it during development.  The organs and tissues formed from these cells are all very different from the original cells – we say that these cells have differentiated.  The cells can go down three possible routes:  The innermost layer of cells will form all of the guts, lungs and liver.  The middle layer of cells will form the skeleton, muscles, heart, blood and kidneys.  The outermost layer will form the skin and nervous system.  Eventually the developing animal will have a vast array of different cell types e.g. nerve cells, muscle cells, liver cells etc.

The cells undergoing their initial divisions.

The cells undergoing their initial divisions.

All of these cells have the potential to go wrong and form tumours e.g. brain tumours, muscle tumours and liver tumours.  Generally, these tumours will be made up of one cell type, e.g. the haemangiosarcoma we saw in a previous post was a tumour originating from the blood vessels, so the tumour itself was made up of a mish-mash of badly formed blood vessels.

In the ovary and testicle there are lots of cells which form the egg and sperm cells (germ cells) of the animal.  The job of these germ cells is to make complete new animals, so these cells have the potential to become ANY cell in the body during development of the foetus.  If this development goes wrong, and a tumour forms, the cells which make up the tumour could become any cells imaginable!

A teratoma from the chest.

A teratoma from the chest.  There’s a hair within the large cystic space.

A teratoma (‘terato’ comes from the greek for monster, and ‘-oma’ comes from the greek for tumour) is a tumour which consists of cells from all three layers of cells found during development.  We can find whole teeth, skin, glands, cartilage, bone, hair, muscle, fat, spleen, nerves and many more tissues inside these monstrous tumours.  These tumours originate from cells which have the potential to form other types of cells (stem cells), and stem cells are found all over the body, but they are in their largest numbers in the testicles and ovaries.  It goes without saying, that these are the most common sites for teratomas.

They cause a problem because they can grow quite large and interfere with the normal function of the organ in which they are growing.  Generally they are benign (teratoma), as they contain well-formed cells which don’t behave very aggressively.  However, sometimes some of the cell types within the tumour might not form fully or may be altered so that they become invasive and the tumour can be malignant (teratocarcinoma).

The eye and tumour are cut into a very thin section and put on a microscope slide.  The blue arrow is the eye, the black arrow is the tumour.

The eye and tumour are cut into a very thin section and put on a microscope slide. The blue arrow is the eye, the black arrow is the tumour.

In this case, a tumour was found behind the eye of a bird.  It was composed of a very bizarre mixture of lots of different tissues:

The black arrow points to a piece of cartilage with overlying tracheal tissue (respiratory epithelium - blue arrow).  The red arrow points to intestinal tissue (villi)!

The black arrow points to a piece of wind-pipe cartilage (respiratory epithelium – blue arrow). The red arrow points to some intestine!

Lobules of pancreas within this tumour.

Lobules of pancreas within this tumour.

There's even a fragment of muscle...

There’s a fragment of muscle…

...a large piece of cartilage.

…a large piece of joint cartilage.

There's even brain tissue in here!

There’s even brain tissue in here!

bone and marrow

The black arrow shows bone and the yellow arrow points out bone marrow. It’s almost like a whole new animal is growing within this tumour.

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What's this?

What is this? #2 Marie’s Disease!

What was that?

It was the tarsal (ankle) and metatarsal (foot) bones of a dog’s leg. But why are they so funky?

The complete set.

The complete set.

These bones are affected by Marie’s disease, or hypertrophic pulmonary osteoarthropathy (people like Marie’s disease because it’s shorter and rhymes).  It is characterised by clubbing of the fingers and toes, and inflammation of the bony surfaces (periostitis) and joints (arthritis).

As you might realise from the name, it is often associated with lung conditions, especially lung tumours. So the whole name breaks down to: hyper = over, trophy = growth, pulmonary = lungs, osteo = bones, artho = joints, and pathy = badness. Phew!

A lung tumour (metastatic melanoma), cut open

A lung tumour cut open (darker red central area)

Aside from lung tumours, other diseases can also cause hypertrophic osteoarthropathy, although for some reason they are mainly problems that affect the chest. No-one is 100% sure how exactly chest problems mess with the bones, but there are several theories.

Longstanding irritation and inflammation to any tissue can cause mineralisation, so it is thought perhaps the blood supply to bone is somehow disrupted which would lead to swelling and inflammation. There is a large nerve running through the chest — the vagus nerve — which has many branches and, among other things, tells the blood vessels how ‘open’ (or dilated) they should be. Perhaps diseases in the chest affect this nerve, in turn causing the blood vessels elsewhere to open up fully and blood to pool, eventually resulting in inflammation and irritation. Another idea is that hormones (or hormone-like substances) might be produced as a by-product of disease, signalling the bones to overgrow.

They may not look it, but these bones are thin and weakened. Though the outer periosteal layer has grown erratic new bone following irritation, the inside of the bone is being reabsorbed.

They may not look it, but these bones are thin and weakened. The outer periosteal layer has grown erratic new bone following irritation, but at the same time the inside of the bone is being reabsorbed.

Pierre Marie and his mate Eugen von Bamberger (probably not actually friends) are credited with first describing the disease. However, about 2500 years ago Hippocrates also recognised clubbed fingers and toes, and signs of hypertrophic pulmonary osteoarthropathy have been found in  human remains from his time.

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