Arteries and veins differ in many ways, including diameter, strength, durability, and valves. Arteries have thick walls that can withstand high pressure. When the heart pumps blood, there is high pressure in the arteries, which we call blood pressure. High blood pressure is necessary for the heart to pump the blood to parts of the body, especially to the brain. In fact, in order to send enough blood to the brain, the sympathetic nerves press against the muscles around the walls of the arteries, by which the pressure is raised further and blood carried to every part of the body. The walls of arteries are thus created thick and strong so that they can resist such high pressure. When the system breaks down and the pressure is higher than necessary, the arteries may tear, resulting in bleeding in the brain, paralysis, or even death.

The walls of the veins, in contrast, are created thin. The arteries are vessels that feed us, while the veins shuttle used blood back to the heart. The arteries do not expand much, nor do they store much blood. No more than 15% of the blood in the body is found in the arteries.

The veins can expand due to their thin walls and store more blood. A total of 65% of the blood is found in the veins. While the arteries are equipped with features to function with little blood and high pressure, the veins are built to hold more blood, but at a lower pressure. The veins function as a blood tank that is tapped immediately in times of bleeding, especially to delay the death of the brain. In case of bleeding when the brain cannot get oxygen, the body declares a state of emergency. The sympathetic nerves convey messages to the arteries and veins. The muscles in the arteries constrict and stop unnecessary flow into organs and tissues other than the brain and the heart. The aim is to send more blood to the brain. The veins constrict simultaneously, and the blood in their store is pumped first to the heart and then to the brain.

It is dangerous when an artery bleeds. It may lead to excessive bleeding because of the high blood pressure, and death could ensue. Conversely, a person does not lose much blood when a vein bleeds, for blood pressure is virtually non-existent in the veins. Surgeons are especially careful about puncturing an artery during an operation because it is hard to stop the blood that spurts out of the arteries.

The arteries are not found close to the skin; but are located deep under the skin. The arteries, especially those in the arms and legs, pass from among the muscles so that they cannot be easily harmed. The veins are created immediately beneath the skin. Bleeding of a vein does not pose a huge threat as bleeding of arteries.

A question may tug at your mind at this point: why aren’t both vessels created deeper and thus protected?

Nurses cannot use the arteries when they administer medicine, blood, or serum because the arteries refuse blood from outside due to the high pressure. Therefore, only the veins accept serum or blood externally. As the veins are in plain sight right under the skin, the job of nurses is made easier. The jobs of surgeons also becomes easier because the arteries lie deep within and the veins lie along the surface.

The arteries do not have valves to stop the reverse flow of blood because the blood is already pumped with high pressure. There are valves only between the heart and the arteries. If it weren’t for these valves, the blood pumped from the heart would flow back, causing heart failure, and the brain would not receive blood. The veins by contrast are equipped with valves to stop blood from flowing back.

When we move our legs, the blood is jammed in the veins. The closing direction of the valves are placed so as to lead to the upward movement of the blood. When we move, the blood in our legs moves upward and when we stop moving the blood does not flow back down because the valves close with the end of the movement. The valves in our veins are present only in those that are below the heart. There is no valve in the vessels above the heart, as they would be rendered useless due to gravity.

e rarely think about our veins and arteries, but they have been perfectly created to serve our body.

We tend to overlook our skin, but it performs many vital functions for our bodies – including coming to our rescue in emergencies.

Since it is designed to function within very precise limits, our body is very susceptible to small temperature changes. Since abnormalities in these changes occur, the body has various mechanisms to keep its temperature constant. One of these mechanisms works by changing the amount of blood in the veins underneath the skin. When talking about body temperature, it is important to distinguish between the internal and external body temperature. The internal temperature is the temperature of the brain and internal organs, while the external body temperature is the temperature of the skin.

Normally, arteries that transport clean blood, and veins that carry dirty blood, are not connected; therefore clean and dirty blood never mix. However, as a consequence of some illnesses or birth defects, an abnormal bridge between arteries and veins may be present. This kind of condition is usually called arteriovenous shunts, or arteriovenous fistula. In these kinds of situations, blood is pumped directly from arteries to veins. In other words, clean blood flows towards dirty blood. Normally, the clean blood has to travel the body, providing oxygen and other supplements to cells, while collecting carbon dioxide and returning to the heart to be cleaned again.

An incredible network for the transportation of substances from the blood in arteries and veins has been created. If this system, known as the “capillary network,” did not exist, none of our organs could be fed, and the circulatory system would not be able to provide its vital function.

The system is necessary for two reasons. The speed of the blood in the arteries and veins is too fast for anything to be transported to the organs, and their walls are too thick to allow transportation of substances. Therefore, the blood travels from the arteries to the capillaries, and after the trading of oxygen and other substances with carbon dioxide is completed, it flows to the veins. If any kind of abnormalities exist, the blood flows directly from the arteries to the veins, therefore skipping the capillaries. As a consequence, the organs aren’t fed and the blood gathers in the veins without fulfilling its purpose. Naturally, the oxygen and nutrition balance of the organs gets messed up. The blood is pumped out of the heart with no purpose and heart failure becomes inevitable.

The capillary network has been assigned the task of communication between arteries and veins. The skins is our only organ where the blood flows directly from arteries to veins; AV shunts accomplish a very important duty in this function.

There is a network of veins underneath the skin. The number of veins in this network is so many that if they were completely filled up, they could hold up to two liters of blood in the skin. Blood is pumped to the skin for two purposes: to provide oxygen and nutrients to the cells, and to collect carbon dioxide and waste products in the cells, as is done with every organ; and to monitor the internal temperature of the body by sending blood to the skin if the temperature gets too high, similar to what radiators in cars do when the engine gets too hot.

There is also the subcutaneous fat tissue underneath the skin which acts as an insulator. The vein network mentioned above is inside this fat tissue. There is a continuous flow of blood from the capillaries that feed the skin towards this network of veins. Moreover, especially in areas where the skin is exposed – such as the hands, feet, face and ears – there is a blood flow from the small arteries towards this network of veins. Contrary to other organs in the body, blood flows directly from the arteries to the veins. If this direct blood flow did not exist, the amount of blood in the skin’s veins would be close to zero, because the amount of blood necessary for skin nutrition is very little. However when the internal temperature rises too much, the amount of blood, which is normally close to zero, can suddenly increase to as much as 30% of the blood pumped by the heart. In this case, the body’s internal temperature is being transported to the skin. This is an incredibly efficient cooling system. However, if the weather is cold, the AV shunt veins are switched off and the skin’s blood flow is decreased until close to zero, therefore maintaining internal temperature. The fat tissue underneath the skin also has a very important function, as it acts as insulation, helping maintain temperature.

Body temperature and the body’s systems work in perfect coordination with each other. We can observe a very simplified version of this system in computer based air conditioners. However, when we reflect upon the incredibly sophisticated cooling system of the human body, we come to the conclusion that no other system is as perfect as that.

The hypothalamus, which has various vital duties for the brain, was also given the very important mission of controlling the body’s temperature. There are hot and cold heat receptors in various parts of the hypothalamus. When body temperature increases, these receptors are activated. As a consequence of this warning, skin veins all over the body expand. Simultaneous with the expansion of the veins, sweat is excreted.

The hypothalamus also has the duty of suppressing the mechanisms that produce heat throughout the body. For example, trembling is stopped and general metabolism is slowed down to decrease body temperature. As metabolism slows down, the production of heat becomes minimal, and cooling takes place. In conditions where the body temperature is too cold, some hormones secreted in the hypothalamus trigger the pituitary, and then the thyroid, hormones. Since thyroid hormones are responsible for increasing metabolism, body temperature increases. However if body temperature increases above normal, the control of the hypothalamus on the thyroid is reversed, and thyroid hormones are decreased, therefore decreasing body temperature.

There is one more reason for placing so many veins in the perfect and miraculous body’s skin: except for extremely cold weather conditions, quite a large amount of blood exists in these veins that are not used for nutritional purposes. Some of our organs act as storage for blood; two of the most important ones are the spleen and liver. Another one is the skin. In the course of losing blood, or an illness that increases the need for blood, the spleen and liver shrink. As a consequence of this shrinkage, the blood inside them is sent to the heart, through veins, and distributed to the areas in need of blood. This increases the heart rate.

A similar scenario occurs in the skin. The veins responsible for cooling shrink, and the blood they contain is sent to the heart with the help of the main veins, therefore helping the heart pump. During heavy loss of blood, the blood in the skin comes to the rescue. Patients who are losing blood have incredibly cold and pale skin. This is because the blood in the skin has reduced to a minimum.

The obverse of this happens in an illness called erythromelalgia, where more blood than normal flows from the arteries to the veins in the skin. This is mostly seen in the hands, feet, nose, and ears, since AV shunts are more prevalent in these areas of the skin. The symptom of this illness is burning pain, which is triggered by heat and soothed by cool temperatures. The nutrition of the skin decreases and some substances produced because of the absence of oxygen increases redness, heat, and pain, since some of the capillaries feeding the skin shut down and all of the blood flows from arteries to veins with the AV shunts.

Our skin protects our muscles and bones, and contributes to the beautiful aesthetic of our body. It provides our sense of touch, and is therefore a means for us to experience the material world, as well as providing temperature control for our bodies. It can clearly be seen that the relationship between the skin and the veins could not have evolved by the consequence of coincidence.

We vessels can be divided into three main groups in terms of structure and function. The ones with thicker walls, which bring every organ the blood they need from the heart, are the arteries. The pressure inside us is higher and we easily carry blood to the organs. The ones with thinner walls, lower pressure, and larger inner space are called veins. As a matter of fact, both arteries and veins have a three-layered structure that is very suitable for holding a fluid like blood. Since our walls are strengthened with both connective tissue and smooth muscle layers, we bear the pressure coming from the heart and help blood proceed by contracting and relaxing. Since arteries are directly subjected to the strong pressure from the heart, our walls were created in a thicker and stronger form. Since the veins return blood to the heart and thus have lower pressure, we have valves that close after blood passes, so it does not flow backward due to gravity. This is a serious challenge for the blood passing through your legs. Varicose veins might develop due to weight gain from pregnancy or obesity, which increases pressure on the legs, or to hours of standing, walking, or running on hard surfaces.

Capillaries are the most delicate blood vessels, with walls made of a single layer of epithelium, which enables us to exchange substances between blood and tissues. As blood vessels, our total length is about 120,000 kilometers. Try to imagine if a fisherman’s net were made from a rope of this length and how wide it would be! And yet, such a vast network of blood vessels is located in your body, and capillaries take blood to every part, without neglecting an area as tiny as the head of a pin.

The well-being of your organs is directly related to us. If our interiors begin to narrow, because of fatty cholesterol plaque for instance, then we begin to lose our flexibility. This means malnutrition for that organ, since a lesser amount of blood than expected can come. If a blood clot sticks to our wall and blocks the blood flow, the relevant organ may be in terrible trouble. If other arteries supply blood to that organ, then it can handle this, but if a main artery is blocked and if secondary channels do not exist or are insufficient, you experience infarction. Taking this into consideration, you need to be careful what you eat and lead a physically active life. When you get old, if sufficient blood does not pass through us in your brain, failures with brain activities appear and you go senile. As the walls of veins and arteries have a rich network of nerves, we let the suitable amount of blood flow according to the need of the organ we’re serving, under the control of the autonomous nervous system. While blood vessels that are connected to an organ not currently requiring much blood contract to reduce the amount supplied, those that are connected to currently more active organs expand. And dear Peter, the greatest blessing here is that none of these activities require any conscious effort from you; everything works smoothly without your even being aware.

This wonderful network of ours finds its value in the vital fluid we carry. If it weren’t for blood, we would have no value at all, and such a perfect means of distribution would be unnecessary. Even the duty of the heart is to make this fluid circulate throughout the body. Now, let us step aside and allow blood to have the floor.

When we have been sitting or lying for a long time we can suffer from orthostatic hypotension due to an insufficient operation of the sympathetic nerves.

When we are lying down, the blood pressure in our arteries is pretty much equal throughout the body. When we stand up, the blood pressure is affected by the gravity and increases in the vessels under the heart, while decreasing in the brain. If we lie down again, the blood pressure in the arteries balances once again. If these changes cannot be naturally controlled, then we may suffer an increase or decrease in blood pressure, which could result in a fatal injury.

There are baroreceptors in the walls of main arteries whose tasks are to measure constantly the blood pressure and to send data (electrical signals) to the brain, informing it about the blood pressure in the body. These baroreceptors are located in the aorta as it leaves the heart and in the carotid artery as it enters the brain. With the onset of hypertension, the frequency of the signals that are sent to the brain increases and this drops in case of hypotension. The center of vessel movement in the brain, with regard to the frequency of electrical signals it receives, perceives a low or high blood pressure.

In the brain is a vasomotor center; this continuously controls the blood pressure and regulates it. This center constantly receives data about blood pressure. If the pressure decreases, the signals of the sympathetic nerve increase. If the pressure increases, the signals to the parasympathetic nerves are suppressed. As a result of sympathetic irritability, the heart begins to beat faster and stronger. It pumps much more blood in a unit of time, and thus the blood pressure increases. The arteries and veins also constrict and owing to this constriction in the arteries, the blood pressure increases further. As a consequence of constriction in the veins, the extra blood that is stored inside the veins is pumped into the heart. Now, as the heart is receiving greater volumes of blood, it works faster and contributes to the increase in the pressure. In the meantime, as a result of the suppression of parasympathetic nerve signals, the heart contracts faster and stronger, thus pumping much more blood.

As the blood pressure rises, the mechanism which is in charge of reducing the pressure via vasomotor center is triggered. While pressure is applied to the sympathetic nerves, the signals that are being sent to the heart and vessels decrease. Thus, the rate of systole and the amount of blood which is being pumped decreases. As the arteries receive less blood the volume of blood in the system falls off and as the arteries and veins expand, the blood pressure falls. Due to the dilatation in the veins, the volume of blood which is sent to the heart also decreases and as a result the heart pumps less blood and the blood pressure drops.

However, by triggering the parasympathetic nerves, the signals that are sent to the heart increase. This helps to slow the heart down and ensures that there is less blood pumping through the system. As a result, the blood pressure which has been reduced via the sympathetic system is reduced even further with the parasympathetic system. At this point, it is necessary for there to be a rapid drop in blood pressure, which is provided by the simultaneous functioning of different mechanisms.

We cannot control this system and it acts extremely rapidly and with great elegance. Even in the systole period, when the heart is pumping the blood and there is a short and sudden increase in pressure and in the diastole period, when the heart relaxes and there is a short and sudden decrease in pressure, the system is in charge and functioning at every second, operating to increase the hypotension and to decrease the hypertension. The average healthy human heart beats 70 times per minute. Consequently, there are 70 systole and 70 diastole stages every minute; thus a normal balance can be maintained by decreasing the pressure, which increases 70 times every minute, and by increasing the pressure, which decreases 70 times every minute; this is how the body maintains a normal balance. In other words, this system functions 140 times every minute. Is it possible that this system, which operates throughout our life, a system that we are not aware of, a system that is so sensitive and vital to our lives, a system the details of which have only recently been understood after centuries of observation could be nothing more than a coincidence?

The pressure regulating system mentioned above carries out other important tasks while we are sitting and standing as well. The amount of blood going to the brain is related to the maintenance of a difference in blood pressure between the arteries and veins and to the recirculation of blood. In connection with hypotension, the pressure in the veins to the brain decreases, in order to partially compensate for the decrease in the arteries. By preventing a decrease in the difference of pressure (perfusion pressure) between the two systems, the continuity of blood going to the brain can be maintained.

In addition, a small decrease in the blood going to the brain can lead to an increase in acidity and carbondioxide in the brain tissues and to a decrease in oxygen; this results in the dilatation of the blood vessels in the brain. When these systems go into action anyone who is not suffering from orthostatic hypotension will have a stable amount of oxygen consumption in the brain when they stand up, and thus not experience dizziness.

In fact, scenes from karate movies are wonderful displays of the perfect functioning of this system. In such scenes, the fighter will jump up, and then suddenly fall to the ground; he will then suddenly spring up and performs different moves. Certainly with every movement, the blood pressure changes suddenly, but as a sign of the Creator’s mercy and grace, the body is able to maintain a balance. Should not the person watching these scenes stand in amazement, thinking: “Oh my God, what an incredible order! How great is Your knowledge, power, wisdom and art!”

As mentioned at the beginning of the article with reference to an actual sad incident, when a person whose sympathetic system is not functioning normally suddenly stands up, they can suffer from dizziness and perhaps even faint due to irregular blood pressure.

For patients suffering from orthostatic hypotension patients, it is important that they do not stand up rapidly. In addition, exercises that encourage the use of leg muscles before standing up will help pump blood towards the brain.

Pause for a minute… What would happen if this miraculous system did not exist? Consider how much time it would take you to merely get out of bed every day!

He was born in Cordova in 52OAH (1126) and named after his grandfather Abu al-Walid Muhammad ibn Ahmad ibn Rushd, who died in the same year. His grandfather was the Chief Judge in Cordova and the foremost authority in Maliki jurisprudence. To distinguish him from his illustrious ancestor, Ibn Rushd was later known as Ibn Rushd al-Hafid (the grandson).

Cordova, where Ibn Rushd grew up, was a thriving centre of all the diverse arts of civilization and culture attracting many great scholars from around the then known world to its wonderful libraries. Ibn Rushd studied and memorized the Qur’an and the Muwatta of Imam Malik. He was an excellent student of jurisprudence and quickly qualified to give legal opinions and sit as judge.

Following his work in the sciences of law, language and Hadith, he went on to study mathematics, astronomy and astrology and then medicine. He was a friend to the most prominent thinkers and writers of his age: Ibn al-Tufayl (d. 1186/6), author of the famous allegory Hayy ibn Yaqzan (said to have influenced Robinson Crusoe ); the philosopher, Ibn Bajja (Avempace in the West, d. 1139); the great jurist and judge Abu Bakr ibn al ‘Arabi (d. l148); the famous physician Abu Marwan ‘Abd al-Malik ibn Zuhr (Avenzoar in the West, d. 1161) and his son Abu Bakr (d. 1198).

Ibn Rushd served as a judge in Ishbiliya (Seville) in 1171 and then in Cordova two years later. His reputation for wide knowledge, correctness and fairness in giving verdicts, led to his appointment as Chief Judge. His book Bidayat al-mujtahid wa nihayat al-muqtasid (The reference for the searcher and the resort for the fair) remains an important reference for students of jurisprudence and is still taught in universities to this day. Although he was a Maliki he used the ideas of other schools of thought. Because he had so many activities and interests besides his public duties, Ibn Rushd had to organize his time very fully: he spent his days working as a judge, teaching, and in academic discussion with other scholars; he reserved his nights for reading and writing.

His friend Ibn al-Tufayl wrote to invite him to visit Marrakech, the capital of the Muwahhidun (Almohades) who had established a powerful and stable state in North Africa after they took over from the Murabitun (Almoravides), and were famous for their patronage of scientists, physicians, theologians and philosophers. Ibn Rushd’s intelligence, learning and ideas so impressed the ruler, Abu Yusuf ‘Abd al-Mu’min, that he was appointed to reform the educational system. This he did successfully before returning to Cordova.

When Abu Ya‘qub ibn ‘Abd al-Mu’min came to power, he appointed Ibn Rushd as his personal physician after Ibn Tufayl. Ibn Rushd held this post for a year (1183) when he was appointed as Chief judge. His success provoked court envy and he was falsely accused of heresy, in particular that he adhered too closely to the doctrines of Aristotle. He was indeed a supporter of Aristotle’s doctrines after these were properly reformed and adapted to Islam. Ibn Rushd fell out of favour at the court and was ill-treated. His books on philosophy were burnt, though his works on medicine and theology were not censored. When Abu Ya‘qub discovered he had been misinformed, he tried to invite Ibn Rushd back to apologise to him, but he was too late. Ibn Rushd died on 9th Safar 595AH (December 1198).

His writings

Ibn Rushd was broadly cultured indeed and wrote on many different subjects. Here we can mention only the most famous of his great works. In jurisprudence, as noted above, he wrote Bidayat al-mujtahid wa nihayat al-muqtasid (The reference for the searcher and the resort for the fair). In philosophy, he wrote Tahafut al-tahafut (refutation of the refutation), his response to Imam al-Ghazali’s famous Tahafut al-falsafa (refutation of philosophy). Ibn Rushd combined both philosophy and religion in mainly two books: Fasl al-maqal wa taqrib ma bayna l-shari‘a wa l-hikma min al-ittisal (an authoritative treatise on the convergence between the religious law and philosophy), and Kitab al-kashf ‘an manahij al-adilla fi ‘aqa’id al-milla wa ta‘rif ma waqa‘a fiha bi hasb al-ta‘wil min al-subah al-muzayyifa wa 1-bida‘ al-mudilla (an exposition of the methodology of demonstrating the creeds and description of the confusions and innovations in interpretation which confound truth and lead to error). In medicine, Ibn Rushd wrote the Kitab al-kulliyyat fi al-tibb (a general reference on medicine) which was translated into Latin and Hebrew and European vernaculars. It was a major reference in medicine though it never reached the standard of al-Qanun fi al-Tibb of Ibn Sina (Avicenna, d. 1037) which was used everywhere as simply T he Canon of Medicine.

Ibn Rushd had prepared this book especially for practising physicians and students of medicine. He apologised for the work’s brevity, a limitation he attributed to his preoccupation with commitments to judging, political affairs and philosophy. He advised those who sought greater detail to consult al-Taysir (The simplification) of Abu Marwan ‘Abd Al-Malik ibn Zuhr. Al-Kulliyyat is organized under seven broad headings or chapters:

1. Anatomy
2. The function of the organs
3. Diseases (pathology)
4. Syndromes: a brief clinical review
5. Health care, especially sports, massage and sleep
6. Medication and diet
7. Healing (particularly of different types of fevers).

The chapter on anatomy in al-Kulliyat

Ibn Rushd criticized the physicians and students of medicine of his time for neglecting anatomy. His own presentation of the subject is both concise and precise. He divides it into two major areas:

a. Anatomy of ‘simple’ organs such as bones, flesh, and veins.

b. Anatomy of ‘compound’ organs-for example, the arm which comprises bones, flesh, veins, tendons, nerves etc.

His description starts with the bones of the head and the teeth. 

Bones

There are six bones in the cranium and 14 in the upper jaw (the maxilla) and the ear, and two in the lower jaw (the mandible). All these bones are attached by seams except the two bones of the mandible that are articulately joined. This was later established as untrue-the mandible in fact has a single bone not two. The first to discover this was the physician and linguist ‘Abd al-Latif al-Baghdadi (Ibn al-Labbad). He examined 10,000 cadavers removed from the hills of al-Muqattam, east of Cairo, during the construction of a road. He realized this fact after observing thousands of examples. This was revealed in his wonderful book al-Ifada wa l-i’tibar fi l-umur al-mushahada wa l-ahwal al-mu‘ayana fi ardi Misr, (review and lessons from examinations and experiences in Egypt).

Ibn Rushd wrote of the teeth that there are 16 in each jaw-two central incisors, two lateral incisors and two canines, and five molars and premolars on both right and left sides. There are three or four roots in the maxilla but only two in the mandible, the remaining teeth have only one root.

He also described the large aperture in the back part of the skull, the foramen magnum, and its relation with the seven vertebra of the neck (cervical vertebrae), which have apertures on the sides. The vertebrae of the chest region are twelve; in the lumbar there are five, linked to the sacrum in which he counted three bones (in fact there are five) attached to the bone of the coccyx which is also composed of three attached vertebrae.

Ibn Rushd said that all vertebrae are articulate except the first two from the neck, because the first vertebra is attached to two appendices ramified from the skull.

He also said the bone of the sacrum is attached from the sides of the hips, in each of which is the acetabulum (socket) which contains the ‘head’ of the thigh bone (femur), often referred to as the ‘pomegranate’.

Ibn Rushd described in detail the bones of the front side starting from the clavicles up to the pubic bone, passing by the ribs and the bones of the shoulders. He also described the upper and lower limbs very precisely. What he wrote is not different from what we know today except that, for the bones of the arm, he uses ‘lower’ and ‘upper’ zanad (forearm) to mean the radius and the ulna. He indicated the bones of the leg, nowadays known as the fibula and tibia, in the same terms.

Veins and arteries

In the old days, the arteries were called the ‘beating veins’ (dhawarib ), and jugular veins were the ‘non-beating’ veins (ghayr al-dhawarib ). Ibn Rushd made a precise distinction between the two types of veins which remains accurate and valid. He wrote:‘Arteries come out of the heart whereas the jugular veins come back to it.’ He also described the difference precisely, the arteries are more solid and have two similar layers: the fibres of the inner layer are crosswise while the outer layer fibres are length-ways-even by modern standards a very professional anatomical description.

Two arteries of different size come out of the heart, the smaller one goes to the lungs and ramifies into them (pulmonary artery). The other (aorta) is larger, divided into many sections and ramifies into the whole body, one section going up to the head and upper limbs, another going alongside the vertebral column with branches leading to the chest and abdomen; it ends in the lower body and feeds the two lower limbs.

Ibn Rushd’s fascinating description is confirmed as correct and accurate. However, he failed to observe the circulation of the blood accurately. This was not properly described until nearly a hundred years later by Ibn al-Nafis (d. 1288) a Damascus-born physician who worked in hospitals in Cairo, and many centuries before William Harvey (1578-1657). 

The nervous system

The nervous system is the most complicated organ in the human body and its anatomy has only gradually become known over recent centuries. Nevertheless, Ibn Rushd was able to describe the brain, its membranes and the cranial nerves. He describes the smelling nerve perfectly, pointing out that it ends with a nipple like that of the breast. He does not consider this nerve as the primary one, giving that distinction to the optical nerve. The first pair of nerves issue from the brain and form the sclera inside the cranium, then come out to the eyes each from its side. This is a wonderfully precise description.

Ibn Rushd then describes the nerves that feed the muscles of the eye. According to modern anatomy, these nerves are the third, fourth and sixth, but Ibn Rushd considers them all as the second pair that ramifies in the muscles of the eyes. He considers the third pair as related to the next (the fourth), and these feed areas of the face, the ear, the palate and the nose-in fact, he was writing about the fifth and seventh pair of nerves according to modern anatomy. As for the fifth, Ibn Rushd says that a part of it leads to the ears and the muscles of the cheeks, whereas this is identified as part of the seventh pair.

Ibn Rushd writes that the sixth nerve feeds the pharynx and the tongue and part of it leads to the muscles near and around the shoulder and another part deviates to the neck and a branch of that goes to the larynx. This is actually the eleventh nerve (the accessory nerve) and there is some confusion in Ibn Rushd’s account with the description of the tenth nerve (vagus; the wandering or confused nerve). Although he attributes many characteristics of the vagus nerve to the accessory one, Ibn Rushd is very accurate in the description of the characteristics themselves. He observes that some of the branches of this nerve lead to the chest and feed the heart, lungs, and esophagus; that it runs through the diaphragm and makes the link with the cardiac and liver membranes, the spleen and the rest of the intestines/bowels.

Ibn Rushd describes the seventh nerve as starting from the back of the brain and ramified in the tongue: he is describing accurately the twelfth nerve (hypo-glossal).

He describes as accurately as modern anatomy does, the nerves that go along the vertebrae. He mentions the eight pairs of cervical nerves, sixteen pairs of dorsal nerves, and five pairs of lumbar nerves.

He misses the correct number of the sacral nerves, they seemed only three to him because they are very closely attached-in fact they are five. Three nerves come from the bone of the coccyx and a single nerve comes out on the sides from the middle. This is absolutely accurate.

Ibn Rushd wrote;

‘The brain has two nipple-shaped appendices that grow from its two advanced abdomens (olfactory bulb). They reach the bone that resembles the cribrium (cribriform plate), which is perforated with many holes [i.e. like a sieve], not smooth but rough with its position in the cranium, where it reaches the end of the nose.’

It would be very hard to improve on the concision or accuracy of this account even today.

About the membranes of the brain, he wrote, again with wonderful, inspiring accuracy:

The brain has two membranes, one is hard and thick (dura mater), and the other is thin (pia mater), they cover the brain very closely and in some locations are completely joined. The thick one is adherent to the cranium. This membrane has many perforations in two places, the first at the canal at the end of the nose (cribriform plate), and the second at the bone of the palate. Under the brain on the thick cover, there is the mysterious net composed of veins that go up to the head.’

The structure of eye

Ibn Rushd’s ability and competence as an anatomist is most clearly demonstrated in his description of the eye and its layers, which compares most favorably with what is known today except some minor differences in terminology. Ibn Rushd had even established the original development of the layers of the eye in the fetus, and discovered that they appear to imitate the layers of the brain and its membranes. Ibn Rushd combined accurate observation with brilliant exposition, sight with insight, presenting the structures of the eye as well as any twentieth-century expert could, and did so many centuries ahead of any physician in Europe.

He wrote:

The eye is composed of seven layers and three liquid areas. The first, from the side of the cranium, is a membranous layer that develops from the thick layer (sclera). The next layer from outside develops from the thinner membrane of the brain; it is called al-mashima (choroid). The next is a layer similar to the net (retina). It grows from the same nerve that comes out of the brain. In the middle of this layer, there is a soft and liquid area called al-rutuba al-zujajiyya (vitreous humour). Inside it, there is another spherical body but with some minor flatness. It is as clear as the ice and called al-rutuba al-jalidiyya , and we call it nowadays al- ‘adasa (lens).’

Ibn Rushd continues this wonderful description, by mentioning al-rutuba al-ma’iyya al-amamiyya (aqueous humour), he also called it al-rutuba al-baydhiyya because its liquid is similar to the soft liquid egg-white:

‘On the outside of this liquid appears a soft body whose inner texture is velvet-like, that follows the al-rutuba of baydhiyya (aqueous humour); smooth from the outside its colour is different from the body of the other, it can be very black or less dark or even blue.’ This is an extremely precise description of the iris (quzahiyyatu al-‘ayn) and the ciliary body (al-jism al-hudhabi).

He adds:

‘Inside the ciliary body, next to the lens, a hole that widens and narrows depending on the extent of darkness that it needs, the hole is called hadaqa (pupil) and the membrane itself is called the inabiyya (grape- like) layer.

‘Next to this layer, a cover that has a hard and clear white and thin plate which is called al-qarniyya (cornea). It takes the colour of the layer below it. On the top of this rises a white body called al-multahim (conjunctiva).’

Ibn Rushd also wrote about the physiology of sight:

‘The sight is not a thing that comes out of the eye as Galinius used to think. The eye receives the colours through the reflecting objects in which they are held, in the same way as a mirror does. Once the colours are reflected in the eye, the object is then conceived by the visioning power.

‘This could well be proved in natural science (physics). That is why any of those parts of the eye is able to reflect the colours because of its very glossy surface. So that body is the special tool to the lens and the advantage of the qarniyya (cornea) is . . . [that] it is made clear and thin so that it does not prevent the ice-like liquid (lens) from receiving the images.’

This is an accurate description of the eye and the physiology of sight that does not differ much from what we know today.

From this brief dip into a chapter of al-Kulliyyat fi al-Tibb , we realize the importance of the work of Ibn Rushd-jurist, philosopher, physician. He was an expert in each of these fields and the most distinguished scholar in Spain and North Africa. He neither experienced nor discovered any contradiction between his religion and his science; rather, his quest for knowledge and excellence, his wonderful curiosity, enlightened and improved his faith. His famous observation- who practises autopsy, his faith in God increases -should silence the false allegation that Muslims never practised anatomy and that they are against applied sciences. What has been written by so many Muslims in all fields of knowledge refutes this allegations. Medicine and the other applied sciences are a necessary and essential contribution to the well-being of humankind. Therefore, to work in them is fard kifaya , a collective obligation upon the community of Muslims as a whole, an obligation which some members of the community must undertake on behalf of the others who cannot.

Islam is the guide for those who seek true and sound knowledge in every subject. All sciences, so long as they are directed to God and not to merely worldly ends or personal glory, bring their students closer to God and make easier the way to approach and please Him: Those who fear God, amongst his servants, are those who have knowledge. And God is the Guide to the straight path.