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Lecture for 2nd year medical students on 5th January 2001 by Professor Omar Hasan Kasule Sr.



A. Homeostasis

B. Urinary Excretion Of Metabolic Waste

C. Micturition

D. Civilization And Disposal Of Body Waste

E. Endocrine Functions Of The Kidney



A. Genitalia

B. Copulation

C. Gametes

D. Gender And Sexual Identity

E.  Anomalies



A. Qalb, Anatomical And Moral Concepts

B. Parity And Laterality

C. Control Of The Cardiac Cycle

D. Coordination

E.  Cardiac Work



A. Ibn Nafees And The Discovery Of Blood Circulation

B. Parity

C. Bio-Physical Laws

D. Control

E. Response To Physiological Need



A. Inter-Face Between The External And Internal Environments

B. External And Internal Respiration

C. Respiratory Movements As A Sign Of Life

D. Control Of Respiration

E. Cough, Sneeze, And Yawning Reflexes



7.5.1 EXRETORY SYSTEM, jihaz bawli

The excretory system consists of the kidneys, ureters, bladder, and urethra. The system forms and voids urine and ensures fluid and electrolyte balance It ensures homeostatic control of the body by controlling and maintaining the volume, pH, and ionic composition of plasma. The kidney is the most important organ in homeostasis fulfilling the physical laws, sunan al kawn, relating to equilibrium and balance, tawazun & i’itidaal. The kidney is the main avenue for excretion of metabolic wastes. The kidney turns 1700 liters of blood per day into 1 liter of urine. The kidney is 0.5% of body weight but receives 25% of the cardiac output. Its blood flow is 1300 ml/minute. Virtually all metabolic waste is excreted via the kidney. Urine is formed by ultra-filtration followed by selective reabsorption and accompanied by tubular secretion. Excretion is a very important physiological function. Not all food intake is absorbed or used by the body. Only what is retained is rizq; the rest is excreted. Micturition is under autonomic and voluntary control. When the bladder is full (350 ml), impulses are sent to the cortex leading to the desire to micturate. Parasympathetic discharge leads to bladder contraction. Control is affected by age, physiologic and anatomical maturity. In most adults there is conscious control. In some cases there is an overwhelming urge that a human cannot control. Handling of body wastes as a mark of civilization growth. Urine is filth, najasat. The Law teaches the importance of avoiding being soiled by urine (MB # 164 p 128) and teaches measures to safeguard against urine (Muslim #575). Washing of hands and the external excretory organs is required after urination. (MB # 165 p 129). The use of the right hand is forbidden (Muslim # 504, 505, 506, 511, 512, 513). Urine of breast-feeding infants is treated differently from that of adults in washing. The urine of female infants is also treated differently from that of males (MB # 167 p 129, Muslim #561, 563, 565). Urination on the street or public places is forbidden (Muslim #516). The kidney has important endocrine functions besides excreting metabolic waste, maintaining water and electrolyte balance, and maintaining pH.


7.5.2 GENITAL SYSTEM, jihaz tanasuli


Genitalia are both external and internal. There is a correspondence between male and female genitalia that is understood from the point of view of embryological development. The genital organs of females consist of the external vulva (mons pubis, labia, clitoris) and the internal organs (ovary, uterus, tubes, and vagina). The male external genitalia are the penis and the scrotum and the internal genitalia are the testes. The Qur’anic term farj (21:91, 24:30-31, 33:35, 66:12, 70:70) is used to refer to the external genitalia of both males and females. These can be used legally or can be misused. External genitalia must be private and are considered part of awrat,  (KS p. 405-406, MB # 240 p 161, # 241 p 163, #242 p. 162). Bathing should be in privacy not to expose genitalia (Muslim # 663, 664, 665, 666). It is forbidden to see somebody else’s external genitalia (Muslim #667, 668). The internal genitalia have an endocrine function besides their reproductive function. Anatomically and physiologically the genitalia have protection because of their importance. Both the ovary and the testis are in places that are not easily accessed from outside. The scrotal temperature is 1-3 degrees centigrade below the abdominal temperature to protect the process of spermatogenesis that is temperature-sensitive. The corrugated structure of the scrotum is to enable it lose heat more easily. The blood-testis barrier protects the environment around the germinal epithelium. The peritoneum and other serosal membranes protect the genitalia. The peritoneal cover is complete in males but the female peritoneal cavity opens to the exterior via the ovary-fallopian tube-uterus-cervix-vagina axis thus allowing ascending infection to reach the ovary. The uterus, rahim, had special mention in the Qur’an (3:35, 16:78, 39:6, 53:32) as the abode of the fetus. Fertilization and growth inside the uterus increase chances of survival compared to animals like frogs and fish whose ova are fertilized and grow outside and birds whose fetii grow partially inside and partially outside. Following implantation, the uterus undergoes many changes until parturition and involutes after that to return to almost its pre-pregnancy size. Female reproductive physiology manifests predictable cyclicity that is one of the signs of Allah, ayaat al llaah. The ovarian, menstrual, uterine, and vaginal cycles recur every month for 30-40 years of the woman’s life and are closely related to the human reproductive function. The ovarian cycle is an example of biorhythm controlled by periodic and pulsatile release of GnRH. The menstrual flow lasts a few days and recurs in a cycle of 28 days on average. The menstrual cycle manifests one of the sunan of Allah because its duration of 28 days is the same as the duration of the lunar cycle. Menstruation is a normal process (MB# #203 p 142) at the end of each ovarian cycle. Unlike Judaism, Islam does not make a menstruating woman a social outcast (Muslim # 592). Menstruation is a cause of physiological stress therefore fasting or prayers are excused (Muslim #660, 661, 662).



The prophet encouraged marriage in order to increase progeny (Ibn al Qayim p. 256). Copulation is a source of physical pleasure (Ibn al Qayim) but has a deliberate reproductive function that is considered one of the Purposes of the Law, maqasid al shari’at. Copulation done legally has the additional purpose of preventing illegal intercourse that leads to social, health, psychological, and economic problems. A supplication, dua, is said before sexual intercourse (MB # 1854 p 896). Foreplay is encouraged (Ibn al Qayim p. 257) and has a beneficial physiological and psychological function in getting ready for copulation. The vagina is the anatomically and physiologically right place for copulation. Anal intercourse is unnatural and is forbidden (Ibn al Qayim p. 262). Coitus has three main processes: Erection, emission, and ejaculation. It is a complicated process involving neural and hormonal influences (Bowman 20.23) and is intimately related to the circulatory system. Different copulation positions are acceptable (Muslim #3363, 3364, 3365). Coitus interruptus, ‘azl, is allowed with some restrictions (Muslim #3371, 3373, 3376, 3377). Copulation in advanced pregnancy is forbidden (Muslim #3389). Copulation with suckling mothers is allowed (KS p. 155, Muslim # 3391, 3392, 3393, 3394). Copulation is forbidden in menstruation because of the possibility of infection ascending into the female genital tract.


C. GAMETE, nutfat

The Qur’anic term nutfat or mani (p 1152 16:4, 18:37, 22:5, 23:13-14, 25:54, 32:8, 35:11, 36:77, 53:46, 75:37, 76:2, 77:20, 80:19, 86:6) refers to the male and female gametes that are the spermatozoa and ova respectively. In the process of fertilization, equal numbers of chromosomes are contributed from the father and the mother. For each gene from the father there is a corresponding gene from the mother and the zygote gets one of the pair. There is a wide range of permutations possible in gene selection with the result that a fetus of a given genotype is a very miniscule probability given all the possibilities. The male ejaculate is 2-3 mL. There are about 100 million sperms per mL of ejaculate. Only 1 out of these succeeds in fertilizing an ovum. There are only a few days the female menstrual cycle when fertilization can succeed. 500,000 ova are formed in fetal life but only 500 develop into adulthood and only one ovum is released at a time once every 28 days. A human has 46 chromosomes in 23 pairs. Each pair is shared equally between the mother and the father. The relation between a pair of allelomorphic genes is: (a) dominant/recessive (b) intermediate inheritance (variable contribution) or (c) co-dominance (equal). Expressivity is the extent to which a gene in revealed as a determinant of phenotype. Penetrance is the extent to which a gene is expressed. An autosomal dominant gene may show incomplete penetrance or reduced expression when it does show any signs or shows few signs of its presence. Many traits are polygenic traits, being determined by more than one gene. Multifactorial inheritance encompasses both genetic and environmental influences eg diabetes mellitus, hypertension, ischemic heart disease, and duodenal ulcer. There is physical resemblance between the parents and the children (KS p. 574, Muslim #3439, 3440, 3441).



Definition of gender can be genetic, anatomical, physiological, and psychological. Sexual orientation and socialization can also define or reinforce gender identity. The Qur’an has mentioned the make gender, dhukurat (p 447 3:36, 3:195, 4:11, 4:124, 4:176, 6:139, 6:143-144, 16:97, 26:165, 40:40, 42:49-50, 49:13, 53:21, 53:45, 75:39, 92:3). In most societies there is preference for the male gender. The process of sex determination is not random; Allah determines it. Sex is determined by the predominance of either the female or male reproductive substance (Muslim #614). The combination of the 2 sex chromosomes, X and Y, determines gender; XY is genetic female and XX is genetic male. The gonads produce gametes in addition to sex hormones. The sex hormones further define gender. Androgens are musculinizing and estrogens are feminizing. Gender differences in animals are purely due to chromosomes and hormones. In humans, it is chromosomes, hormones, and culture that determine gender identity. Sexual identity is a result of biology and socialization. Some deviant cultures encourage people of one gender to behave like those of another gender contrary to the teachings of Islam that emphasize very strong gender identity and a sharp demarcation between males and females. There are severe punishments for feminine men, al mukhanathin, and masculine females, mutarajilaat (KS p. 190). Homosexuality is also severely punished (KS p. 79).



Factors of teratogenesis: (a) general: age of ovum, genetics, parental age, order pf sibling with the first being at higher risk, multiple pregnancy (b) physical factors: radiation, hypoxia, hyperthermia (c) dietary factors: starvation, vitamin deficiencies (d) maternal disease: DM, rubella, AMV, syphilis, taxoplasmosis (e) drugs: anti-neoplastic, folic acid antagonists, sex hormones, thalidomide



The Qur’anic term qalb is not used in an anatomical sense. The heart is a pump that provides the energy to drive blood through the circulatory system. The weight of the heart is 250-400g; female hearts are 25% less heavy. Parity of the heart is understandable from the embryological point of view. Separation of the left and right hearts ensures supply of well-oxygenated blood to the tissues. Control of the heart rate is by the electrical conduction system. The blood supply is from the coronary arteries. Myocardial oxygen consumption at rest is 27 ml/minute that is approximately 12% of total body oxygen consumption. Myocardial blood flow is 75 ml/minute that is 4% of cardiac output. Separation of the left from the right heart leads to efficiency; well-oxygenated blood is delivered to tissues. The cardiac circle is well coordinated in health. The force of contraction increases with increase of the interval between contractions. There is co-ordination between the atria and ventricles. There is co-ordination between the left and right ventricles. The left cardiac output is equal to the right cardiac output. The pulmonary and systemic circulations are connected in series so that the blood pressure in both must be equal. Fluctuations are only temporary.



The prophet mentioned the flow of blood inside the body. Ibn Nafees was the first to describe circulation. William Harvey described it centuries later in 1628 CE but is erroneously or deliberately credited with its discovery by European writers. In 1661 Malphigi described capillaries. In 1668 Leuwenhoek saw blood corpuscles in capillaries. The circulatory system is an illustration of the sunan of equilibrium and control. Two circulatory systems, systemic and pulmonary, work in parallel in perfect coordination, a sign of the perfection of Allah’s creation. There are in addition special circulations such as the brain, coronary, splanchnic, skin, placental and fetal blood circulations. The circulatory system consists of arteries, veins, and capillaries. About 70% of blood in the peripheral circulation is in veins. The capillaries’ length is 2400 kilometers and total area is 6300 square meters. Valves in veins and lymphatics to prevent back-flow and regulate flow. Blood circulation follows biophysical principles and is another illustration of the unity of creation because physical and biological phenomena follow the same laws, sunan al kawn. The efficiency of the heart’s energy conversion is 20%, better than many machines. Blood pressure is the motive force. Mean flow is directly proportional to mean pressure and indirectly proportional to resistance. The principles of laminar flow apply to blood circulation; velocity is directly proportional to volume of flow and indirectly proportional to the area of the conduit. The density and the viscosity of the blood, the pressure gradient, the radius and length of the vessel affect the velocity of flow. Three mathematical equations can accurately describe blood flow dynamics: (a) O=PA.Q/A (b) W=PQ + MV2 and (c) F= DP/R; where O=Cardiac Output, P=Mean Aortic Pressure, A= Cross-Sectional Area, Q=Stroke Volume, M= Mass Of Stroke Volume, V=Velocity Of Ejection, W=Work Done By The Heart, F=flow rate, R=resistance. The Flow Rate Is The Change In Pressure/Resistance. Resistance to flow increases in vessels of smaller diameter. Vasoconstriction increases resistance. Pressure exerted by blood is resisted by tension in the wall of the vessels. Blood pressure is determined by cardiac output and impedance of flow. Anastomoses are protective in cases of blockage of an artery. Lymph finally drains into the IVC and SVC. Respiratory movements also help venous return. Blood flow to the skin increases in hot temperature to release heat. During digestion more blood flows into the GIT. During exercise cardiac output increases ten-fold and work done by the heart can increase 500-fold.



Heart disease is serious because of the importance of the heart. The common types of heart disease are: ischemic, hypertensive, valvular, congenital, cardiomyopathic diseases. Cardiac failure is usually the final pathway for most of these diseases.



The Qur’an mentioned the chest, sadr, sadr (p 269 3:29, 3:118-119, 3:154, 4:90, 5:7, 7:2, 7:43, 8:34, 11:5, 15:47, 17:51, 22:46, 27:74, 28:69, 29:10, 31:23, 114:5) but not as an organ of respiration. The lungs are the main organs of respiration. The lungs provide a big opportunity for exchange between the internal and external environments. The alveolar surface exposed to the air is 140 square meters. The air-fluid interface is 70-100 square meters. There are 7 x 10E8 alveoli. Surface area of lung capillaries is 120-130 square meters. Besides their respiratory function, lungs have other metabolic functions. The lumen of the airway is controlled autonomically by smooth muscles. It is very important that it remains patent all the time. Larynx prevents food from entering the airway. The term respiration can be used in 2 different ways to mean ventilation or tissue respiration. Ventilation, or external respiration, is gaseous exchange and serves three main purposes: gaseous exchange, temperature regulation, and humidity regulation. Tissue respiration, or internal respiration, is cellular respiration in which food and oxygen are combined to produce energy. Respiratory movements have been used over the millennia as indicators of life. The Qur’an describes the last moments as sakrat al mawt (p 1156 6:93, 33:19, 47:20, 50:19, 56:83-85, 75:26-30, 79:1, MB # 2119 p 993) as respiration begins to fail. There are two respiratory movements, inspiration and expiration, that alternate. Lung volumes and capacities change during these movements. Ventilation of the lungs is not even and there are dead spaces. The diaphragm and the inter-costal muscles carry out the mechanical work of breathing. When dry the composition of atmospheric air by volume is: 21% oxygen, 79% nitrogen. The alveolar air is: 14% oxygen, 80% nitrogen, and 6% carbon dioxide. In alveolar air at 37 degrees centigrade and vapor pressure of water 47 mmHg, the partial pressure of oxygen is 100mmHg and the partial pressure of carbon dioxide is 40mmHg. The difference between the partial pressures of atmosphere and alveoli determines the direction of diffusion of gases. The rate of respiration is controlled by the oxygen needs of the body. Oxygen needs of muscles increases 48 times in exercise. Myoglobin and Hb-F have more affinity for oxygen than ordinary adult hemoglobin. The body stores 20 ml of oxygen per Kg. Body requirements is 4 ml/Kg/minute. If the oxygen supply is cut off, hypoxia occurs in 2-4 minutes. Hypoxia occurs in 10-15 seconds if arterial supply to tissues is cut off. Hypoxia may be hypoxic, anemic, and stagnant. Coughing and sneezing expel irritants. In coughing the glottis is closed raising intra-ductal pressure to 100mm of mercury. When the glottis is opened suddenly, a jet of air under high pressure is released accompanied by the familiar sound of coughing. The glottis is not closed in sneezing but pressure still builds up. Sneeze is from Allah (KS p. 386). Sneeze in salat is from shaitan (KS p. 386). The prophet taught the etiquette of sneezing and yawning (MB # 2055 & 2056 p 966, Muslim #7125, 7127, 7128, 7129, 7130, 7131, 7132). The sneezer should praise Allah (KS p. 386). It is obligatory for those present to respond to the sneezer, tashmiit al ‘aatish (KS p. 386). Yawning, tathawub, is despised; it is from shaitan (KS p. 135). It is forbidden in salat (KS p. 135).

Professor Omar Hasan Kasule sr. January 2001