Emma Stewart Writes

Category: Writing Tips and Advice

Writing tips and advice

  • The Stress Hormone: Cortisol

    The Stress Hormone: Cortisol

    The ‘stress hormone’ cortisol is extremely important for managing and regulating the body’s response to stress. Cortisol regulates metabolism, the response to stress and the immune system. The adrenal glands release cortisol, regulated by the hypothalamus and the pituitary gland in the brain.

    Adrenal Glands

    The paired adrenal glands live just above each kidney and are directly connected to part of the autonomic nervous system. The adrenal medulla produces adrenaline (epinephrine) and noradrenaline (norepinephrine), both of which play a role in the ‘fight or flight’ response. Read more about that system here.

    The adrenal cortex produces glucocorticoids, of which cortisol is the most important. The hypothalamus regulates cortisol secretion via the HPA axis, the hypothalamus—pituitary—adrenal cortex axis. A negative feedback loop maintains cortisol at an appropriate level.

    The hypothalamus releases CRH – corticotropin releasing hormone. This stimulates the anterior pituitary to secrete ACTH – adrenocorticotropic hormone. ACTH reaches the adrenal glands and causes cortisol secretion. Cortisol levels feed back into the hypothalamus and pituitary gland to reduce secretion of CRH and ACTH, keeping cortisol levels where they need to be.

    Role of the HPA Axis

    This system maintains homeostasis in the body by regulating metabolism, the cardiovascular system, immune system, reproductive system and the central nervous system. That’s a lot of jobs! Serious illness results from this system going wrong.

    Cortisol

    A glucocorticoid or ‘steroid’ hormone, cortisol is the stress hormone. It follows a diurnal cycle, increasing after waking, slowly dropping until late afternoon. It then resurges before dropping to its lowest point in the middle of the night.

    Pharmaceutical versions include hydrocortisone, prednisolone and several other ‘corticosteroids’. Applications include treating inflammation, managing autoimmune disorders, chemotherapy and treating allergies.

    The Effects of Cortisol

    Glucose Metabolism

    Cortisol stimulates glucose synthesis and the breakdown of glycogen in the muscles. It also increases the breakdown of fats and blocks insulin. It causes insulin resistance in an effort to increase blood glucose levels, i.e. blood sugar.

    Immune System

    Cortisol reduces the immune response, the inflammation cascade and reduces T-cell growth. That means it is immunosuppressive. This is why pharmaceutical steroids are used to treat immune-mediated and autoimmune diseases like rheumatoid arthritis, psoriasis, eczema and allergies.

    Cortisol delays wound healing, because it suppresses inflammation. The inflammation process plays a role in healing of wounds, whether injuries or surgical. Steroid treatment is withdrawn prior to surgery whenever possible, for this reason.

    Electrolytes and Water Homeostasis

    Cortisol increases GFR (glomerular filtration rate), in other words, function of the kidneys. It causes excretion of phosphate and potassium, along with water and sodium retention. Too much cortisol or not enough cortisol will cause electrolyte disturbances.

    Cortisol also stimulates secretion of stomach acid, which explains why chronic stress causes problems like heartburn and stomach ulcers. People who are stressed for a long time have high ciruclating cortisol levels.

    Memory

    Cortisol combined with adrenaline stimulates memories of short-term emotional evens in order to ensure we avoid the same thing in future. This effect is part of how trauma affects the mind and body in the long term. It is absolutely a factor in the development of PTSD.

    Long term exposure to excess cortisol damages the hippocampus, the part of the brain essential for storing long term memories and learning. This means excess cortisol impairs the ability to learn.

    Pregnancy

    During pregnancy, cortisol plays two essential roles. At 30-32 weeks gestation, cortisol stimulates production of pulmonary surfactant. Surfactant allows the lungs to expand when the first breaths are taken after birth. Without it, the newborn cannot breathe. One of the byproducts of beef production is extracting this surfactant from the cow’s lungs. Cattle lung surfactant massively improved survival rates of premature babies.

    The second role is to stimulate parturition, to initiate labour. Foetal cortisol triggers conversion of progesterone to oestrogen which in turn stimulates prostaglandin secretion and oxytocin receptor development. Oxytocin is the hormone that stimulates contractions of the uterus. Because it reduces progesterone, treatment with steroids can induce miscarriage in early pregnancies.

    Stress

    So why does this matter? The adrenal glands function to help the body cope with stressors. Adrenaline and sympathetic nervous system is there for acute dangers and cortisol is there for longer term stresses. If you are writing about someone who has been living a stressful life, they will have high levels of cortisol which impacts their physiology.

    Cortisol increases insulin resistance and thus contributes to potential risk factors for type 2 diabetes mellitus. Research into this is ongoing and while stress or high cortisol alone isn’t enough to cause diabetes, it could be part of the complex of risk factors.

    Cortisol affects the immune system and impacts immune-mediated disease. Interestingly, cortisol can both suppress the immune system and over-activate it. We know that stress impacts autoimmune diseases.

    The HPA axis is regulated by dopamine, serotonin and norepinephrine – neurotransmitters responsible for regulating mood and emotions. This connection shows how psychological stress impacts our physiology, and vice versa.

    Oxytocin down-regulates the HPA axis, reducing stress. Oxytocin is the ‘love hormone’, aside from its role in giving birth and milk let down in animals, it is released when we are close with people we love, including hugging and even during orgasm. So it proves that spending time with those we are close to can help reduce stress. This even applies to our pets!

    I talked previously about the term ‘psychosomatic’ discussed in the medical terminology series. Psychosomatic means that psychiatric changes, such as mental health disorders, have an impact on our physical bodies. It does not mean that your problems are ‘all in your head’ and not real. They are real, and mental distress has an impact on our physiology too.

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  • Rodents for Writers: Rats

    Rodents for Writers: Rats

    Welcome to part one of Rodents for Writers: Rats. Rats have been very significant in human society for millennia. From beloved pets to laboratories to the Black Death, rats are everywhere. So, get comfortable while I tell you everything you need to know about rats.

    Biology of Rats

    Rats are mammals in the Order Rodentia, the sub-order Myomorpha: the mouse-like rodents. The larger of the mouse-like rodents, rats can reach up to 500g or larger. The best known species are the black rat (Rattus rattus) and the brown rat (Rattus norvegicus). The average lifespan for wild rats is one year, however domestic rats usually live two to three years.

    Teeth

    A characteristic of all rodents is their front teeth. Basically, the open-rooted pairs of incisors continue to grow throughout the animal’s lifetime. They are kept in check by chewing and gnawing. Rats have no canine teeth, and a set of premolars and molars that do not continually grow. The space between the incisors and molars is called the diastema.

    Senses

    Rats have extremely sensitive hearing and sense of smell. On the other hand, their vision is poor and they have red-green colourblindness. They see into the ultraviolet spectrum, however, beyond what humans can see.

    Body

    Rats have stocky bodies, with fur covering most of them except the ears, paws and tail. The tail functions for temperature regulation and balance. They are good climbers, swimmers and burrowers. Their front paws are prehensile and are used to hold food, although they don’t have opposable thumbs.

    Diet

    Rats are true omnivores and can eat just about anything. Cereals, insects and small animals are the mainstay but rats in urban spaces eat discarded and stored human food. In rural places they often break into livestock food stores. Many people employ cats to control rat populatons.

    Reproduction

    Rats breed quickly, capable of producing five litters per year. They reach sexual maturity at six weeks old and the average is seven pups per litter. Gestation is 21 days and the female can get pregnant again immediately after giving birth.

    Social

    Rats are very social creatures and live in colonies, basically a large group. They sleep together, groom each other and play together. People keep rats as pets and they are affectionate, trainable and entertaining to keep. For this reason, they should live in a small group, called a mischief.

    Human Uses For Rats

    Laboratory rats are common, especially in the field of medical research. They work in efforts to find mines and explosives. Rats are trained easily and can act and take part in animal-assisted therapy.

    Rats in Society

    Pests

    Rats are a common urban pest infesting houses, buildings and infrastructure. Consequently, they can live off discarded and stored food and are strong swimmers. Urban rats lose their fear of humans too, and are challenging to eliminate once they are established.

    Invasive Species

    The worst invasive species, rats have been stowaways on ships for as long as humans have been sailing the seas and oceans. Rats contributed to the extinction of many species of wildlife, both plant and animal. Antartica is the only continent to be free of rats.

    Spread of Disease

    Rats carry infectious diseases that can be passed on to other species, they are zoonotic vectors.

    Bubonic Plague

    A plague by any other name, you may have heard of the Black Death, the Black Plague. The worst pandemic in world history. The bacteria Yersinia pestis causes the plague and rats, and their fleas, played a huge role in spreading it. Rats are not the only factor, though, but they are the most commonly associated with the Black Death of the Middle Ages.

    Leptospirosis

    Leptospirosis, alternatively known as Weil’s disease, is a serious bacterial infection. It causes jaundice, kidney failure, meningitis and bleeding in the lungs. Rats shed Leptospira in their urine. Leptospirosis is an important zoonotic disease for humans and dogs. For this reason, we vaccinate dogs against Leptospirosis in the UK routinely.

    Rats in Culture

    Asian Cultures: China

    The first of twelve animals in the Chinese Zodiac is the rat. When people born in the year of the rat, they are associated with creativity, intelligence, honesty, generosity, ambition, a quick temper and wastefulness.

    India

    Rats are the vehicle of Ganesha: a patron of the arts and sciences, remover of obstacles and a bringer of good luck. Consequently, a temple of Ganesh always has a rat statue in it.

    European Cultures

    Rats generally have negative associations, largely because of the association with the Black Death in the 14th century. ‘Rats!’ is used as a mild curse word in the UK. Similarly, calling someone a rat is an insult, implying dishonesty and being untrustworthy. To ‘rat on someone’ means to betray them by informing on them.

    However, pet rats are common in the UK and are beloved by those who keep them. Myself included. I have cared for many rats over my veterinary career and kept some myself. The downside is their short lifespans.

    Rats in Fiction

    Due to their associations with disease and dirt, rats accordingly play a negative role in many fictional works. They have been used as villains in animation, used as an evil entity by H.P. Lovecraft and as a torture method by George Orwell. Another example is Templeton, the rat character in Charlotte’s Web, shows selfishness and self-serving tendencies.

    Conversely, positive rat characters do exist in fiction. For example, Rizzo the Rat from the Muppets, Remy from Ratatouille and Master Splinter in the Teenage Mutant Ninja Turtles. It’s nice to see rats get some good press for once.

    The Pied Piper of Hamelin story in particular, tells of a man who led the rats away from a town with enchanted pipe music. When the town refused to pay him, he led their children away as well. This story is associated with the Black Death.

    Rats undoubtedly symbolise disease, filth and death in a lot of fiction. Crime and dishonesty is a common theme as well. The Bible describes rats as ‘unclean’ in Leviticus. However, rats symbolise cunning and resourcefulness as well.

    As I have said, rats are intelligent creatures and learn quickly. They are inquisitive and entertaining to watch. They get a bad rap because of the Plague, however this reputation is largely undeserved. Rats deserve a shift in perspective, I think.

    Every Friday we will have another creature feature. This month’s theme is Rodents for Writers. Rats are often maligned by society. Next week, we’ll be talking about mice. If you missed last month, we discussed snakes. You can read that here.

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  • Endocrinology For Writers

    Endocrinology For Writers

    Endocrinology for writers is the new Monday blog series for March. Endocrinology is the study of the system of hormones and signals the body uses to manage its functions. It’s a complex subject and many people find it confusing. I’m here to help try to make it easier to understand.

    Why will this help writers? It allows you to understand important body functions such as responses during stress and fear, illnesses and conditions like diabetes and reproduction. Knowing what each of the important hormones actually do helps you understand and describe the effects and behaviours. So let’s get into it with some definitions.

    Endocrinology Definitions

    Hormone: signalling molecules secreted by endocrine glands to regulate physiology and behaviours. Hormones take different forms; amino acid complexes, steroids, eicosanoids, leukotrienes and prostaglandins.

    Glands: glands that produce and secrete hormones into the bloodstream. Some organs have endocrine functions as well as their other functions in the body.

    Neuroendocrine system: thepart of the brain that connects to the endocrine system and controls the release of hormones based on input from the nervous system.

    Axis: a sequences of endocrine glands that signal each other in a specific order to control hormone secretions.

    Homeostasis: the steady state of optimal physiological function. The endocrine system manages the body in order to maintain this.

    Tropic hormones: these hormones target other endocrine glands and organs to stimulate them to produce other hormones. The anterior pituitary gland secretes the majority of these hormones.

    Feedback loops: the endocrine system has negative feedback loops that control the production of hormones. For example, high levels of cortisol will cause the hypothalamus to stop producing hormones that stimulate cortisol production. This stops the body producing too much of a hormone.

    Endocrine Glands and Organs

    The endocrine system involves the entire body and many organs and glands are involved, both secreting hormones and responding to hormones. The neuroendocrine system is the part of the brain responsible for controlling hormone release.

    Neuroendocrine System

    Pineal gland: the pineal gland within the brain produces melatonin, a homrone derived from serotonin, which regulates the sleep cycle. The pineal gland links to a light sensing organ called the ‘parietal eye’ or ‘third eye’ in reptiles and amphibians. This is most notable in tuataras, a lizard-like reptile that is the last surviving species of its category.

    Hypothalamus: this part of the brain organises inputs from all other parts of the brain and responds by releasing hormones and tropic hormones. This triggers the pituitary gland.

    Pituitary Gland: there are three lobes of the pituitary gland:

    • Anterior: responds to tropic hormones and releases other hormones
    • Intermediate: only functional in the foetus
    • Posterior: direct nerve connection to hypothalamus and produces oxytocin and vasopressin (anti-diuretic hormone or ADH)

    This system controls all aspects of reproduction; bonding, sexual behaviour, spermatogenesis (sperm production), ovarian cycle, parturition (giving birth), lactation (milk production) and maternal behaviour.

    It also controls regulation of metabolism, eating and drinking, fat metabolism, mood regulation, fluid and electrolyte homeostasis and blood pressure.

    Glands

    Glands are organs that specifically produce hormones as their main function. You may know some of them already. So let’s get into the details.

    Thyroid gland: The thyroid gland is located just below the larynx and has two lobes. It secretes the thyroid hormones thyroxine (T4) and triiodothyronine (T3) to control metabolism.

    Parathyroid glands: Four tiny glands located behind the thyroid gland, hence the name. The parathyroid glands produce parathyroid hormone (big surprise!) an important hormone for calcium homeostasis.

    Adrenal Glands: a pair of glands located above the kidneys, split into two regions with different functions. We’ll cover this in detail in a later post.

    • Adrenal cortex: produces glucocorticoids, mineralocorticoids and androgens
    • Adrenal medulla: adrenaline (epinephrine) and noradrenalin (norepinephrine)
    • The adrenal glands also produce dopamine and enkephalin

    Gonads: the primary organs producing sex hormones and gametes. I’m including the uterus and placenta too.

    • Testes: the male gonads produce androgens such as testosterone, oestradiol (estradiol Am. Eng.) and inhibin.
    • Ovaries and Corpus Luteum: progesterones, oestrogens (estrogens Am. Eng.) and inhibin.
    • Placenta: progesterone, oestrogens, human chorionic gonadotrophin (hCG) and human placental lactogen.
    • Uterus: during pregnancy it produces prolactin, which stimulates milk production, and relaxin which affects blood flow and relaxes the pelvis and birth canal.

    Organs With Endocrine Functions

    Several organs have endocrine functions in addition to their other functions. Not only do they produce hormones, they also respond to hormones as well as other changes in the body’s physiology.

    Pancreas: the pancreas has exocrine functions (digestive enzymes) and endocrine functions related to blood glucose (blood sugar) and metabolism.

    • Insulin – produced in the β-islet cells (beta-islet) to reduce blood glucose and stimulate glucose uptake by cells.
    • Glucagon – produced in the α-islet cells (alpha-islet) to increase blood glucose and glucose production in the liver.
    • Somatostatin – produced in the δ-islet cells (delta-islet) to inhibit release of insulin and glucagon.

    Kidneys: the kidneys produce erythropoietin which stimulates production of red blood cells in the bone marrow. They also release renin, which is involved in the RAAS system and calcitrol, the active form of vitamin D3.

    Liver: produces insulin-like growth factor (IGF), thrombopoietin (THPO) to stimulate platelet production, hepcidin, angiotensinogen and angiotensin. The later two are also part of the RAAS system, which we’ll cover at a later date.

    Heart: ANP (atrial natruiretic peptide) and BNP (brain natruiretic peptide) released from the muscle cells of the heart control blood pressure.

    This covers a basic introduction to endocrinology for writers. Over the next few weeks we will cover the important systems that will help you understand how important endocrinology is for our behaviours and emotions. Don’t forget to subscribe for more updates and find me on my social media channels.

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  • Creature Features: Snakes Cultural Impact

    Creature Features: Snakes Cultural Impact

    Snake’s Cultural Impact

    Photograph of a cobra with its hood raised.
    © Patrick JEAN / muséum d’histoire naturelle de Nantes, Attribution, via Wikimedia Commons

    Let’s discuss the cultural impact of snakes. Snakes form an important part of many cultures in the world, both modern and historical. Ophidiophobia (phobia of snakes) is commonplace. Last week, we discussed the potential dangers certain snakes pose. The main risks include venomous bites and the largest constrictors. Non-venomous snakes are not a threat to humans.

    Snake Charming

    You will know this from various cartoons and movies. Snake charming is an Indian roadside show where the charmer plays a flute-like instrument and the snake responds to the music. Typically, the Indian cobra species.

    The snake is actually responding to the movement of the instrument, they lack external ears so they don’t hear in the conventional sense. Animal welfare laws prohibit snake charming.

    Snake Catchers

    The Irula tribe from India have been catching snakes for generations professionally. The snake skin industry was outlawed in 1972. The Irula tribe now catch the snakes to milk their venom. The venom is collected and used for producing antivenom, biomedical research and other medicinal products.

    There are modern day experts elsewhere in the world, who specialise in catching snakes both for study and to remove them from homes and property.

    Consumption

    Many people eat snakes, especially in Asia: China, Taiwan, Thailand, Indonesia, Vietnam and Cambodia. Snakes are believed to have health benefits and aphrodisiac properties. Snake wine, which is wine infused with whole snakes, is used in Chinese traditional medicine.

    Pets

    People keep snakes as pets, especially the more docile smaller snakes like the corn snake and the ball python. Snakes require specialist housing for optimum health but usually only need fed once every week or two. You need to seek expert veterinary care for snakes as well, not all vets are knowledgable or comfortable handling them.

    Symbolism and Mythology of Snakes

    Ancient Mesopotamia

    Nirah means ‘little snake’ in Sumerian. Nirah is a messenger god and may be lord of the underworld. Sumerian art features representations of two intertwined serpents. Ancient deities iconography in Assyria and Babylon feature snakes.

    Hopi Tribe of Arizon

    The Hopi Native American tribe celebrate snakes as a symbol of fertility. They release snakes into the fields to guarantee good crops. So they represent the umbilical cord joining all humans to mother Earth.

    Egypt

    Ancient Egyptian iconography commonly incorporates snakes. The Nile Cobra adorns the crown of the pharaoh. Snake iconography associated with Ra, Wadjet, Renenutet, Nehebkau and Meretseger.

    More sinister purposes for snakes exist in Ancient Egypt – using them to murder an adversary or to comit a ritual suicide. Cleopatra is famous for allowing an asp (Egyptian Cobra) to bite her, according to popular belief.

    Ouroboros

    Found in Ancient Egyptian iconography and Greek magical tradition, the symbol of a snake eating its own tail. Gnosticism, Hermeticism and alchemy adopted the ouroboros icon.

    The ouroboros represents the eternal cyclic renewal, or a cycle of life, death and rebirth. Snake’s shed their skin as they grow, hence this is representative of the transmigration of souls or immortality.

    The act of biting its own tail is a fertility symbol in some religions: the tail is a phallic symbol and the mouth is a yonic or womb-like symbol. So, the ouroborous represents sexual intercourse and reproduction.

    Ancient Greece: Medusa

    The legend of Medusa depicts a monster with snakes for hair that can turn those who look at her into stone. The hero Perseus slayed Medusa. She had two sisters, Stheno and Euryale who were both gorgons as well. Her image symbolises warding off evil.

    In Ovid’s Metamorphoses the tale of Medusa is a bit different by comparison. Medusa, a priestess of Athena and suffered sexual assault by Poseidon, the god of the sea. Athena turned her into a gorgon after this. Some say as punishment, others believe it was so she could protect herself. Because of this, Medusa is an important symbol for sexual assault survivors in the modern day.

     Asclepius

    The Greek god of healing, Asclepius, represented by a rod or staff with a serpent wrapped around it. The sick and injured went to Asclepius’ temples for healing and care. Hence, the staff of Asclepius became a symbol for medicine.

    Similarly, Hermes’ staff, Caduceus has wings and two serpents intertwined around it. With a V included in the symbol, it represents veterinary medicine. Hermes was messenger to the Olympian gods.

    India

    Indian traditions and deities feature snakes a lot. Shiva has a cobra around the neck. Vishnu is sometimes depicted as sleeping on a seven-headed snake or within the coils of a serpent.

    Temples dedicated to cobras called Nagraj are common. Snakes symbolise fertility and people celebrate them during the Hindu festival of Nag Panchami.

    China

    The Chinese Zodiac features snakes as one of the twelve celestial animals. 2025 is the year of the snake, hence my choice of topic for this month. Snakes associate with traits like intelligence and unscrupulousness. Ancient China related snakes to the river deities.

    Christianity and Judaism

    The Garden of Eden

    We can’t talk about snakes in culture and society without discussing this. In the book of Genesis, a serpent tempts Eve to eat the forbidden fruit from the Tree of Knowledge. God throws Adam and Eve out of the Garden as punishment and this confers the concept of ‘Original Sin’ on humanity. Whether you believe it or not, nobody can deny the importance of this story on shaping our society and culture. Genesis doesn’t name the serpent, but it is a common belief that the serpent is the Devil.

    Moses

    In the book of Exodus, Moses turns his staff into a snake as proof of God’s power. In the book of Kings, God instructed Moses to create the Nehushtan – a bronze snake on a pole that cured people of snake bites in the desert.

    Satan

    The final book in the New Testament, the book of Revelation contains the final mention of serpents in the Bible. There, serpents are symbolic of Satan, the fallen angel who tempts people towards sin. He plays a role in the apocalypse described by the book of Revelation.

    It’s clear that snakes represent evil and sin in Christianity. There is less of this in Judaism and Islam.

    Conclusion

    It’s clear that snakes play an important role in a lot of cultures. They can symbolise fertility, the cycle of life, rebirth, evil and temptation. People fear and revere snakes across the world. Often maligned and misunderstood, yet they have played an important role in shaping society as it is today.

    However, snakes also represent healing, recovery and caring for people and animals alike. I love snakes, they are fascinating creatures and get a bad rap. They have personalities, unique abilities and an important place in the ecosystem.

    I hope you enjoyed this summary of the snakes cultural impact and why they matter so much. They have a number of representations which you can use in your writing to symbolise different things. As always, if you have any thoughts or questions, I’d love to hear them.

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  • Understanding Medical Terminology: Body Parts

    Understanding Medical Terminology: Body Parts

    Understanding Medical Terminology: Body Parts

    Welcome to the final part of understanding medical terminology: body parts and organs. Like everything else we’ve discussed so far, there are specific word roots for all the organs and body-parts. They are rooted in Greek and Latin, unsurprisingly. Greek and Latin is even combined for certain terminology. Let’s look at a few important examples.

    Note the spelling differences between British English and American English. Both are correct, but it depends on which version of English you use.

    This list is by no means exhaustive. You will find many more terms online or in a medical dictionary.

    OrganGreek RootLatin Root
    BloodHaem(at)- or Hem(at)- [AmEng}Sangui- / Sanguin-
    Gall BladderCholecyst(o)-Fell-
    HeartCardi(o)-Cordi-
    KidneyNephr(o)-Ren-
    LiverHepat(o)-Jecor-
    LungsPneumon-Pulmon(i)- (Pulmo-)
    BrainEncephal-Cerebr-

    Blood

    Haematology focuses on the study of the blood, specifically the blood cells. It involves measuring the number of each type of blood cell and assessing them under the microscope for abnormal changes. This tells you a lot about the health status of the patient.

    Haematemesis means ‘vomiting blood’, a symptom that can be very concerning. ‘Emesis’ is the root for vomiting. Haematuria means ‘blood in the urine’. Haemostasis means to ‘stop bleeding.’

    CPR

    CPR stands for ‘cardiopulmonary resuscitation’, a word that combines Greek and Latin roots. You should learn CPR if you don’t already know how to do it, you never know when it could come in handy to save someone’s life.

    The basics involve chest compressions to circulate the blood and pump the heart, providing breath or oxygen. Defibirillators only help if the heart has an abnormal rhythm, if there is no pulse you need to keep up the chest compressions.

    Unfortunately CPR in real life is nothing like the movies. It’s rarely successful and if the brain lacks oxygen for more than a few minutes then damage is highly likely to occur. A person who needs CPR will need time in intensive care to recover. That doesn’t mean you shouldn’t try, though.

    Conclusion

    I’ve given examples of a range of word roots from medical terminology but the combinations are endless. There are entire dictionaries of medicine. It’s important to use medical terminology correctly though, as some of the terms are easy to confuse.

    Even if you’re writing medical dramas like Greys Anatomy, keeping the medical jargon to a minimum is a good idea. Most people won’t know a lot of these terms and you don’t want to send your readers running to search up definitions every other paragraph.

    I hope this series has been helpful. I’m always happy to help with any questions regarding medical subject, especially animal related ones. So drop me a line if you need help.

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  • Creature Features: Venomous Snakes

    Creature Features: Venomous Snakes

    Venomous Snakes

    © Patrick JEAN / muséum d’histoire naturelle de Nantes, Attribution, via Wikimedia Commons

    There are about 600 venomous snake species in the world. Of those, about 200 are considered deadly to humans. They produce venom which is injected by their fangs during a bite, in order to kill prey, defend themselves and even aid in digestion of their meal.

    It’s important to make a distinction between the terms ‘venomous’ and ‘poisonous’ as they’re used interchangably which is incorrect. Poisonous means it is ingested, inhaled or absorbed into the body. Venom is injected under the skin or into the muscle via fangs. There are a couple of snake species that are both venomous and poisonous if eaten.

    How toxic a snake’s venom is is usually assessed by way of a murine LD50 test. This means the dose of venom required to kill 50% of a population of mice or rats, expressed by milligrams of substance per kilogram of test subject body weight. The lower the LD50 is, the more toxic the substance.

    Which Snakes Are Venomous?

    There’s not one single taxonomic group of venomous snakes, because they evolved the venom separately. Venomous snakes are found anywhere where snakes are found. The Common Adder (Vipera berus) is the only venomous snake in the UK and it is not deadly.

    The four main families of venomous snakes are:

    Atractaspididae – native to Africa and the Middle East, also known as burrowing asps.

    Colubridae – most are harmless but five species, including the boomslang, have caused human fatalities.

    Elapidae – this family includes mambas, brown snakes, coral snakes, death adders, cobras and taipans.

    Viperidae – true vipers and pit vipers including puff adders, rattlesnakes and cottonmouths.

    We’ll cover a few of the individual species later on. The potency of venom varies by species. Other factors in determining how dangerous a snake is includes aggression, so how likely the snake is to bite. The amount of venom delivered by a bite, the locaiton of the bite and access to antivenom and medical treatment.

    Effects of Venom on the Body

    There are four main types of venom based on the mechanism of action. Snake venom can include a combination of different agents with different effects. For more details check out my coverage of toxins here.

    Proteolytic agents break down protein, causing damage to the cells and connective tissue around the site of the bite.

    Haemotoxic agents attack the blood cells and damage the heart and cardiovascular system. This leads to clotting disorders, anaemia, tissue and heart damage and will risk death.

    Neurotoxic agents attack the nervous system and brain. They cause paralysis, including paralysing the nerves that control breathing and lead to asphyxiation.

    Cytotoxic agents attack cells and cause local tissue damage and inflammation at the site of the bite.

    Black Mamba

    © Patrick JEAN / muséum d’histoire naturelle de Nantes, Attribution, via Wikimedia Commons

    Dendroaspis polylepis. One of the longest venomous snakes in the world and the fastest moving land snake. The black mamba is native to subsaharan Africa. It is the most feared snake in Africa due to it’s speed, size, aggression and how quickly symptoms develop after envenomation.

    Their venom acts fast and contains highly potent neurotoxins, cardiotoxins and other dangerous substances. Symptoms develop within 10 minutes of the bite and treatment must be quick, aggressive and thorough. Antivenom is available for treatment of black mamba bites but speed is essential to have a chance of survival.

    Common Death Adder

    By CSIRO, CC BY 3.0

    Acanthophis antarcticus. This snake holds the title of ‘fastest strike’ in the world. They go from strike position to biting back to strike position in 0.15 seconds. They don’t flee from people, but may not bite unless actually touched. Mortality rate is 50-60% for untreated bites from these snakes.

    They are native to Australia, the home of all kinds of dangerous wildlife. Their speed means that the bite will be over by the time you realise it’s happening. So watch your step.

    Caspian Cobra

    By Omid Mozaffari – http://calphotos.berkeley.edu/cgi/img_query?enlarge=0000+0000+0511+1571, CC BY-SA 3.0

    Naja oxiana. The most venomous snake in Central Asia. Their venom is mainly potent neurotoxins but also includes several cytotoxic and cardiotoxic agents. Symptoms are rapid onset and death can occur within an hour of envenomation. Untreated mortality rate is 75%, the highest of any of the true cobras in the Naja genus.

    Eastern Brown Snake

    By Poyt448 Peter Woodard – Own work, Public Domain

    Pseudonaja textilis. The deadliest snake in Australia, it claims the top spot for annual deaths. They are notorious for their temper, aggression and speed. The good news is that Australia reports less than ten deaths per year for snake bites. This is because of awareness, education, medical provision and availability of antivenom.

    Non-Venomous Snakes

    By LA Dawson – Photograph by LA Dawson, CC BY-SA 2.5

    So if a snake lacks venom, how does it kill its prey? Snakes that don’t use venom are typically constrictors. This group includes pythons, boa constrictors and most other snake species. They hunt by striking and grabbing prey, coiling their body around it and squeezing it to death.

    This group includes one of the largest snake species in the world. Eunectes murinus. The green anaconda. They live in tropical South America around the Amazon rainforest. They are dangerous to encounter for sure, but they typically don’t hunt humans.

    So, at least you’re safer with these kinds of snakes. People keep many smaller species as exotic pets. Notably the corn snake and the ball python, two species that are fairly docile and tolerate handling well.

    Conclusion

    That covers the potential dangers of snakes and serpents. If you would like to learn more, start here on Wikipedia. Next week we’ll get into the cultural significance of snakes and some of the mythology surrounding them. I hope you’ll return for that.

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  • Understanding Medical Terminology – Colour, Position and Quantity

    Understanding Medical Terminology – Colour, Position and Quantity

    Roots of Colour

    Understanding medical terminology – colour, position and quantity. These word roots are essential for accurate descriptions of medical and anatomical items.

    Many words used to describe the colour of something in the medical world exist. Both Latin and Greek roots are used for the most part with the exception of yellow which also has a French prefix. These roots are combined with suffixes to describe many things. Here’s the list of prefixes:

    ColourGreek RootLatin RootFrench Root
    BlackMelan-Atr- or Nigr-–
    BlueCyan-Cerule-–
    GoldChrys-Aur-–
    GreyPoli-Can-–
    GreenChlor-Vir-–
    PurplePorphyr-Purpur- or Purpureo-–
    RedErythr- or Rhod-Rub-, Rubr- or Ruf-–
    Red-OrangeCirrh-––
    Silver–Argent-–
    WhiteLeuc- or LeukAlb- or Cand-–
    YellowXanth-Flav-Jaun-

    Once you know these roots you will spot them in medical words and in Latin names for species. You’ll find that you recognise some of these words already. So let’s take a look at a few examples:

    Cells

    The suffix ‘-cyte’ refers to a body cell. So melanocytes (black cells literally) are the cells in the skin that contained melanin pigment. Melanoma means a cancer of these cells. Erythrocyte translates literally as ‘red cell’ so it’s referring to red blood cells. Leucocyte (also spelled leukocyte) is a white cell – white blood cells.

    -osis

    This suffix means ‘condition, disease process or increase’ and is used a lot. Cyanosis means a blue discoloration of the skin/lips due to hypoxia (low oxygen). You describe someone as ‘cyanotic’ which is the adjective form. Poliosis describes a localised patch of grey or white hair. Chlorosis describes a yellow/green tinge to the skin in cases with severe iron deficiency.

    Bile Pigments

    Two of the main bile pigments use the latin roots. Bilirubin is the red bile pigment. It is produced in the liver by breaking down dead red blood cells. Another bile pigment, which is responsible for the green/yellow colour is biliverdin. You can guess that the prefix ‘bili’ relates to the bile.

    These pigments build up in the body due to liver or gall-bladder disease or a condition causing high destruction of red blood cells. This leads to the bile pigments moving into the body tissues and causing a colour change. It’s usually first noticable in the white of the eye (sclera) but eventually will change the skin and mucous membranes. This is called ‘jaundice’ and uses the French root. A fancy way of saying you look like a Simpson.

    Albumin

    Albumin is a protein that is found in the blood. It has a lot of functions, including transporting other substances and osmotic pressure to maintain the right balance of fluid between the cells and the circulation of the body. It is also found in egg whites, hence the name!

    Porphyria

    Porphyria is a disorder where porphyrins build up in the body. Porphyrins are used to make haem, the protein and iron molecule within red blood cells that carry oxygen around the body. Porphyria causes seizures, vomiting and all kinds of horrible symptoms, but it’s usually genetic.

    One of the key characteristics is the change in urine colour in response to sun exposure. The urine will turn purple. Porphyria causes an extreme sensitivity to sunlight. It has been theorised that this might explain some aspects of legends around vampires and werewolves but this may not be true. There are a number of historic royals who are suspected to have had this disease, including Mary, Queen of Scots and Maria I of Portugal. Vincent Van Gough, the artist, may have suffered from acute intermittend porphyria.

    Medical Terminology – Roots Of Position

    These roots describe locations in a lot of adjectives and nouns in the medical world. They can tell you where something is located, or which isomer of a molecule is present. Isomers are molecules that are identical in terms of properties, except for the direction they rotate polarised light. Such as ‘levothyroxine’ which is an L isomer of thyroxine (T4), the main thyroid hormone. Only the L isomer is active, the D isomer has no effect on the body.

    DescriptionGreek RootLatin Root
    Around/SurroundingPeri-Circum-
    Internal/WithinEndo-Intra-
    LeftLevo-Laev- or Sinistr-
    MiddleMeso- Mes-Medi-
    RightDexi-Dex-, Dextr- or Dextro-

    So here’s a few examples: Pericardium is the tough capsule that surrounds the heart. It contains a small amount of fluid and is there to protect the heart. So ‘peri-‘ means around and ‘cardium’ means the heart.

    Endometriosis

    Endometriosis is a topical condition right now, because it takes an average of seven years to diagnose. As we mentioned before the suffix ‘-osis’ means condition or disease. Endometrium is the term for the lining of the uterus, the part that is shed every monthly cycle. ‘Endo-‘ means inside and ‘-metrium’ is related to the uterus. So endometriosis means that the cells normally found inside the uterus start growing in other places in the body and cause severe symptoms. It’s extremely debilitating.

    Mediastinum

    Mediastinum is the anatomical term for the space between the lungs. The middle of the chest, in essence. This is where there are mediastinal lymph nodes, the thymus and the heart. A rare but interesting condition is ‘dextrocardia’ where the heart is on the right side of the chest instead of the left. There’s even an extreme version called ‘situs inversus’ where all the organs are flipped left to right and mirrored.

    Medical Terminology – Quantity or Amount

    There are a few prefixes that denote the number of something or the amount of something. You will encounter these a lot in medical terminology and other scientific writing. There is one that could trip you up but we’ll get to that.

    DescriptionGreek RootLatin RootOther (French)
    DoubleDiplo-Dupli-–
    EqualIso-Equi-–
    FewOligo-Pauci-–
    HalfHemi-Semi-Demi-
    Many/MuchPoly-Multi-–
    TwiceDis-Bis-–

    One you’ve probably heard a lot is ‘isotonic’. This term describes a fluid that has the same concentration as another. Intravenous fluids are usually isotonic, meaning they have the same concentration of electrolytes as the blood.

    Hemivertebrae is a condition where the vertebrae of the spine don’t form properly, only half of the vertebrae is present. It can cause all kinds of pain and difficulty. It’s congenital, meaning it is present from birth.

    When writing instructions for medication, we use a shorthand Latin acronym. Not for patients, of course, but between doctors, nurses and pharmacists they will use these. B.I.D stands for bis in diem – that means twice a day.

    ‘Equi-‘ means equal in Latin. Don’t get caught out by this anatomical term! The ‘cauda equina’ describes the tail end of the spinal cord where a bundle of nerves extend past the end of the cord. It looks like a horses tail so in this case ‘equina’ is referring to ‘equine’, that is to horses. ‘Cauda’ refers to the tail – a term used a lot more in animal medicine than humans.

    Thanks for reading, I hope you enjoyed this rundown of medical terminology – colour, position and quantity. If you missed the previous ones you can find them here and here. Subscribe to be updated when a new post is live and find me on my social media channels.

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  • Creature Features: Snake Senses and Physiology

    Creature Features: Snake Senses and Physiology

    Snake Senses and Physiology

    Snake Eyes

    Close up view of a python's face showing an orange eye with a slit pupil and the labial pits
    Python Close Up showing eyes and labial pits
    Alias 0591 from the Netherlands, CC BY 2.0 https://creativecommons.org/licenses/by/2.0 , via Wikimedia Commons

    No, not when you roll a one on a dice. Actual snake eyes, on actual snakes. We’re talking about snake senses and physiology. Snakes generally have good vision, some of them have slitted pupils like cats. All snakes lack eyelids, instead they have a clear scale covering the eye called the spectacle.

    You can tell if a snake is due to shed its skin because the eyes go cloudy. Fluid is secreted under the old skin to lift it off to be shed, and this causes the cloudiness. Snakes are vulnerable during this process so they can be more aggressive than usual if disturbed as they are blind.

    Some snakes also have the ability to ‘see’ infrared to find prey in the dark. Pythons, boas and pit vipers have indentations on their upper lips called the ‘labial pits’ which sense infrared. The image shows the little holes along the top lip of the snake, these are the labial pits. Each group of species evolved these things separately, and they are also believed to play a role in temperature regulation as well as hunting. Like night-vision goggles essentially, isn’t that cool?

    Snake Tongue and Sense of Smell

    Snakes use their tongues to detect scents. So when you see their little forked tongue flicker out, that’s what they’re doing. Most people know this. The tongue collects airborne particles and feeds them to the ‘vomeronasal organ’ also known as the ‘Jacobson’s organ’ inside the mouth. This organ is present in most animals, but not humans and aids in scent detection, especially pheromones. So it’s important for detecting prey, predators and potential mates.

    Snake Skin

    Snake skin is highly specialised to protect their bodies and provide grip for their unique form of movement. Lacking legs means that snakes must move flat along the ground, so their scales help them grip the surfaces. Many species can make use of this to climb trees as well and even smoother surfaces to an extent.

    A colourful rainbow boa that is wrapped around tree branches showing the scales of a snake's skin.
    Rainbow Boa showing it’s beautiful scales
    Damien Farrell, CC BY 3.0 https://creativecommons.org/licenses/by/3.0 , via Wikimedia Commons

    Snakes are covered in scales – some are smoother, others are ‘keeled’, meaning they have a ridge down the centre. Their dorsal scales, the upper body scales, are usually loosely diamond-shaped and arranged in interlocking rows. Their ventral scales (belly scales) are usually singular and wide until the vent, after which they are paired until the end of the tail.

    Ecdysis means shedding of the skin. This is something all snakes go through as they grow. Younger snakes will shed more frequently than older snakes. The process takes a bit of time. The new scales grow underneath, and fluid lifts off the old scales.

    This is when the spectacle goes cloudy. The snake will not feed during this process, but usually will feed soon after. Normally the snake sheds its skin in one long piece. They rub their chin on something rough like a rock or tree, and slowly wiggle their way out of the skin.

    Rattlesnakes have a unique set of scales on the end of their tails. They build up from previous sheds and form a hardened collection of scales which makes a sound when shaken. They use this as a warning to predators, and it gives them the name.

    Reproduction

    Snakes reproduce sexually, with internal fertilisation. Most species lay a clutch of eggs, which are left to hatch and fend for themselves. Some species stay with the eggs and care for them until they hatch, like pythons.

    A few species are classed as ‘ovoviviparous’, which means they keep the eggs inside until they hatch and are ‘born’. So this is a kind of inbetween egg layers and live birthers, if you will. Rattlesnakes are an example of this.

    There are a couple of species that have true live births. The boa constrictor and green anaconda both have placentas as well as yolk sacs for their young and give birth to live snakes. They don’t produce eggs.

    A phenonemon called parthenogenesis is seen in a couple of snake species. Parthenogenesis is a form of asexual reproduction, where a female animal can produce fertile eggs without mating. Copperheads and Cottonmouths are capable of this, although they can also do it the old-fashioned way.

    Feeding Snakes

    Snakes are carnivores and eat animals, occasionally eggs but mostly smaller animals. They eat their prey whole and take a while to digest their meal. Some even eat other snakes in some cases. Snakes can’t bite off or chew their food, and are specialised towards this as discussed last week.

    Snakes tend to be ambush predators and will strike quickly to catch their prey. Venomous snakes bite and inject venom to kill their prey before eating it. Other snakes will use constriction – wrapping their bodies around the prey and squeezing it until it dies before they slowly swallow it.

    A cobra demonstrating it's hood which is used in aggression.
    Cobra showing it’s hood
    © Patrick JEAN / muséum d’histoire naturelle de Nantes, Attribution, via Wikimedia Commons

    They then go and rest to digest their prey. Ideally they would keep their body temperature around 30 °C (86 °F) and as they are ectothermic they will move to a location to keep their temperature around that level. It takes some time to digest but they can digest everything but hair, feathers and claws. These indigestible parts are excreted within the faeces of the snake. Snakes don’t eat often, depending on the species and size of the previous meal this can range from once a week to a couple of times a year! Younger snakes need to eat more frequently so they have energy for growth. In captivity it’s important not to overfeed snakes. But they can also go a long time without food as well, over a year in some cases.

    Thanks for reading!

    Thanks for reading this rundown of snake senses and physiology. Next week we’re going to talk about venomous snakes and the dangers snakes can pose to us. If you missed the first part, you can read about snake anatomy here. Don’t forget to subscribe to be updated when a new post is live and find me on my social media channels.

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  • Understanding Medical Terminology – Suffixes

    Understanding Medical Terminology – Suffixes

    Last week we talked about prefixes, descriptors attached to the beginning of medical terms. Today we’re going to talk about understanding medical suffixes, attached to the end of medical terminology to add clarity and further description. There’s a lot to go through, so I’ve organised some of the most important ones into groups. We’ll cover symptoms and surgical ones today.  

    Symptom Suffixes

    A lot of suffixes are related to symptoms experienced by a patient, or clinical signs. In veterinary medicine we tend not to use the term ‘symptom’ as it means the reported experience of the patient. Our patients can’t tell us how they feel, even the parrots that can talk don’t know how to describe their physical sensations!

    -itis

    This suffix means inflammation and is Greek in origin. It’s one people often get confused and assume it means infection. Infections usually do cause inflammation, but other things can cause it as well. So ‘tonsilitis’ means inflammation of the tonsils. ‘Cystitis’ means inflammation of the bladder – it is often used interchangably with UTI (urinary tract infection) but cystitis can be caused by other factors. UTIs cause cystitis, but not all incidences of cysititis are UTIs. This is especially true in cats, where antibiotics are usually not required for cystitis.

    -lepsy

    Another Greek one, unsurprisingly, this suffix means attack or seizure. So it’s used to describe episodic conditions that have sudden ‘attacks’. You can already think of a couple, like epilepsy where the patient has sudden onset seizures. Or narcolepsy, where people suddenly fall asleep.

    -lysis

    From Greek, this means destruction or separation and is used for a number of medical terms. Paralysis means loss of motor function and is a neurological symptom. Haemolysis (hemolysis in US English) describes a condition where the blood cells are destroyed inside the body. The result is haemolytic anaemia. Anaemia means there’s not enough red blood cells. Make sense?

    -rrhage

    This comes from Greek for ‘to break or burst’ and means to burst forth or erupt with rapid flow. So ‘haemorrhage’ means bleeding. Or hemorrhage in US English.

    -stasis

    This means stopping or standing still. Tying it to the previous suffix, if you have haemorrhage you need to induce haemostasis, to stop the bleeding. Haem- or hem- is the prefix related to blood, and changing the suffixes changes the meaning. Using the right suffix could save lives!

    -rrhoea or -rrhea

    Similar to -rrhage discussed above, this term means flow or discharge. I know, that’s a word that feels uncomfortable for some. The obvious use of this is in ‘diarrhoea’ or ‘diarrhea’, where faeces flows freely.

    -stenosis

    This term describes an abnormal narrowing of a tubular structure to restrict flow – commonly in blood vessels but can also be related to other tubular organs like the digestive tract. Aortic stenosis describes narrowing of the aorta, the largest artery in the body. So quite an important one! Pyloric stenosis describes narrowing of the exit of the stomach into the small intestine. Stenosis works as a stand-alone word too.

    Surgical Suffixes

    There are lots of suffixes used in relation to surgery and procedures carried out by medical professionals. They indicate a lot about what the procedure entails, so let’s go through a few important ones.

    -centesis

    This is a procedure where an organ is punctured to aspirate the contents. Aspirate is a fancy way of saying that you suck out some of the contents in a syringe. It is done with a needle, and sometimes ultrasound is used to guide the procedure. A common example is ‘amniocentesis’ where a sample of the amniotic fluid around a foetus is taken for testing, looking for genetic abnormalities and things like that.

    It can be therapeutic too – pericardiocentesis is a big word and it means using a needle to aspirate fluid from the pericardium. The pericardium is a tough tissue capsule around the heart, and if it fills up with fluid it puts pressure on the heart and leads to heart failure. Doing pericardiocentesis can relieve this pressure until the underlying cause can be found and treated.

    -ectomy, -tomy, -plasty and -pexy

    These suffixes are used to describe different types of surgery. So appendectomy means removing the appendix, -ectomy means to remove. Thoracotomy means incising into the thorax (chest) so -tomy means to incise or cut into.

    The suffix -plasty comes from the Greek word meaning to mould or form and describes surgery to reconstruct or repair. A rhinoplasty is a procedure to reshape the nose, for example and this is where the term ‘plastic surgery’ comes from. So it’s not always about adding actual plastic to the body.

    Finally, -pexy means to fix in place. So a procedure that holds an organ in place. Anyone who’s owned a giant breed dog will be aware of this one. Large deep chested dogs like Great Danes are prone to a condtion where the stomach twists around on itself and becomes swollen. This can kill a dog within hours and is a true surgical emergency. Some people choose to do a gastropexy along with neutering. The vet stitches the stomach to the chest wall so it cannot twist. This pre-emptive surgery is termed ‘prophylactic’ because it’s a preventative.

    Conclusion

    Using medical terminology allows for more concise notes, avoiding a need for long-winded explanations. You could say this: “My dog got its stomach stitched to it’s chest wall while it was having routine neutering surgery so that it doesn’t end up getting a GDV in the future.”

    Or you could say this: “My dog got prophylactic gastropexy at neutering.” It’s the same thing, but much more concise. This is partly why medical professionals use this terminology – it saves space and time in clinical notes, referral letters and research papers.

    Of course, we have a responsibility to make sure our patients or clients know what we mean, so doctors may not use these terms when explaining things to you. At least they shouldn’t, or at least explain what they mean. Or check you understand what it means. If you’re unsure, please ask for clarification though.

    I hope you found this helpful and interesting. If you want to learn more or have any questions, my inbox is always open. I’ll be producing a video explaining this with visual aids so if that’s more your style, you can find the video here. Thanks for reading, and don’t forget to subscribe!

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  • Creature Features: Snakes and Serpents

    Creature Features: Snakes and Serpents

    In honour of this being the Year of the Snake, I thought we could talk about snakes. They are a common phobia, and culturally they have had quite an impact on human society. From the Garden of Eden to Cleopatra’s death, snakes are often thought of as evil or dangerous. Yet other people love them and they are a common exotic pet.

    A warning for those with ophidiophobia, fear of snakes, this series of articles will contain photographs of snakes occasionally. So feel free to skip these ones if you like. The anatomical diagrams will hopefully be less of a problem. That said, let’s get into it. We’ll start with some snake anatomy and physiology – discussing some of the unique features of serpents. Then we’ll look at the real life dangers of snakes, and finally a discussion of the cultural impact these creatures have had.

    I have a video going through these details here, if you’d prefer that format.

    Basic Snake Anatomy

    Snakes are limbless reptiles, with long thin bodies and protective scales. They lack eyelids but generally have good vision. Their diet is carnivorous and they strike with venom or constrict their prey, before swallowing it whole. Most snakes lay eggs, but there are a few that deliver live young.

    Like all reptiles, they are ectothermic. You might know this as ‘cold-blooded’ but it means that they control their body temperature by using their environment instead of generating body heat internally. So they bask in the sun to increase their temperature and hide in the shade or burrow to cool down.

    Internal Organs of Snakes

    Here’s a quick overview of their organ layout. They only have one full lung, the right lung. The left lung is small and not involved in oxygen exchange, but may have an immune function. Air sacs extend from the functional lung, storing air and allowing snakes to hold their breath for a long time. The heart has three chambers: a single ventricle and two atria. It is located near the end of the first third of the body length. There is no diaphragm to separate the chest and abdomen.

    The rest of the organs are as expected: a liver, two kidneys, a spleen, a gallbladder, stomach and intestines and reproductive organs. A male snake has a pair of testes and a pair of hemipenes (yes, they have two penises essentially) that lie within the tail when not in use. Female snakes instead have ovaries and an oviduct (kind of like a uterus.) Eggs are formed and held in the oviduct until they are ready to be laid, or hatch before the live young are born.

    Diagram of snake internal anatomy
    Uwe Gille, CC BY-SA 3.0 http://creativecommons.org/licenses/by-sa/3.0/, via Wikimedia Commons
    1. oesophagus
    2. trachea
    3. tracheal lungs
    4. rudimentary left lung
    5. right lung
    6. heart
    7. liver
    8. stomach
    9. air sac
    10. gallbladder
    11. pancreas
    12. spleen
    13. intestine
    14. testicles
    15. Kidneys

    Snake Skeleton Anatomy

    Snakes have no limbs and there is nothing left of the pectoral girdle: shoulders, collar bones etc. Boas and pythons do have vestigial pelvic bones and claws, but most of the more recently evolved species don’t have this at all.

    dbking, CC BY 2.0 https://creativecommons.org/licenses/by/2.0, via Wikimedia Commons

    The body skeleton is made up of vertebrae and ribs: from 175 to 400 vertebrae can be present. Almost all of them have a pair of attached ribs, except the first couple attached to the skull, and the caudal vertebrae that make up the tail of the snake. The division between body and tail can be seen externally when the belly scales change from one single scale to paired scales – just beyond the vent (the genital opening.)

    Snake Skull and Jaws

    The snake’s skull is extremely complex. The jaw has an extra bone called the quadrate bone and extra joints that allow for the snake to open its mouth wide enough to swallow prey larger than its head. Each side of the mandible, the lower jaw, can move independently as well.

    There is significant variation in anatomical structure between different species. The details of this are beyond the scope of this article but if you are interested you can find an in-depth explanation here: https://en.wikipedia.org/wiki/Snake_skeleton#Joints_of_the_snake_skull

    burmese python skull edited to indicate the different joints of the snake skull to facilitate it opening its mouth wide enough to swallow prey
    Mokele at English Wikipedia, Public domain, via Wikimedia Commons

    Lateral view of the skull of a Burmese python, with visible kinetic joints labeled. Red = highly mobile, green = slightly mobile, blue = immobile.

    • Red A: the joint between the mandible and quadrate. It is analogous to the joint in mammalian jaws.
    • Red B: the joint between the quadrate and the supratemporal. It is highly mobile in most directions, allowing a wider gape (i.e., the snake can open its mouth wider) and greater jaw flexibility.
    • Red C: the joint between the prefrontal and maxilla. It allows the maxilla to pivot in the plane of the photograph, and while it does not increase gape, it does facilitate the complex action by which the snake draws prey into its mouth.
    • Green A: the joint between the frontal bone and nasal bone. It allows the nose to upturn slightly, increasing gape and assisting in swallowing.
    • Green B: allows the lower jaws to bow outwards, further increasing the gape.
    • Blue: the joint between the supratemporal and parietal. Immobile, except for Dasypeltis.

    Snake Teeth

    The teeth are curved and point backwards towards the throat to allow for the snake to slowly ingest the whole prey. Venomous snakes have specialised teeth that can deliver venom after a bite such as the ‘fangs’ with grooves to deliver the poison.

    Snakes can strike fast, curling their bodies and arching forward to bite and deliver venom or grab hold of the prey so they can constrict it and kill it. The above link has more details on the different kinds of dentition seen in snake species.

    Close up of a rainbow boa showing the colours of its scales.
    Bernard DUPONT from FRANCE, CC BY-SA 2.0 https://creativecommons.org/licenses/by-sa/2.0, via Wikimedia Commons

    Thanks for reading this brief introduction to snake anatomy Next week we’ll discuss a bit more about snake physiology and some of their unique features, so I hope you’ll come back for that. See you soon!