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Lecture to 2nd year medical students on 28th July 2000 by Professor Omar Hasan Kasule
OUTLINE
6.1.1 CONCEPTS
A. Manifestations Of Perfection (Kamaal)
B. Optimality (Ahsan Taqwiim):
C. Change And Constancy:
D. DNA As A Basis For Predictability Of Biological Phenomena:
E. Incomparability (Nafiyu Al Muqaranat)
6.1.2 MANIFESTATIONS: ANATOMY
A. The Cell
B. Parity, Symmetry, And Laterality
C. Complexity With Simplicity:
D. Adaptation And Variations
E. Changes
6.1.3 MANIFESTATIONS: PHYSIOLOGY, BIOCHEMISTRY, & PHARMACOLOGY
A. Physiological Entity
B. Characteristics Of Physiological Phenomena
C. Physiological Anticipation
D. Chemical Structure
E. Chemical Reactions
6.1.4 PATHOLOGY
A. Concept
B. Etiology
C. Cell Injury
D. Bodily Response To Injury
E. Repair
6.1.5 BIOSTATISTICS AND EPIDEMIOLOGY
A. Numbers: Counting And Measuring
B. Probability Theory
C. Consistency Of Natural Phenomena
D. Models And Prediction
E. Inference And Causality
6.1.1 CONCEPTS
A. MANIFESTATIONS OF PERFECTION
NATURE OF PERFECTION
Perfection of Allah’s creation: Allah is the best creator, ahsan al kahliqin (2:138, 23:14, 37:125). He perfected everything He made, kamal al khalq (27:88, 32:7, 7:11, 2:138, 23:41, 27:88, 28:77, 31:20, 32:7, 37:125, 40:64, 64:3, 65:11, 95:4). He made humans in the best image (40:64, 64:3, 95:4). The process of perfection went through four stages: creation (khalq), making due proportions (taswiyat), balancing (ta ‘adil), and making the best image (surat).
Perfection created and not evolved: The biological perfection was created and not evolved. Every living and non-living things was created perfect de novo. It is therefore wrong to accept the view that life started as primitive life-forms that over time evolved to be the sophisticated human biology that we see now.
PURPOSIVENESS (GHA’IYAT AL KHALQ):
All what Allah created has a purpose (23:115). This applies to the whole organism or its contituent tissues and cells. The supreme purpose for human creation is ibadat. Here are however secondary purposes subsumed under the main one that are related to biology. Humans have to play their role in the maintenance of the eco-system. Each tissue, organ, and cell has its specific function under the overall biological scheme.
ORDER, HARMONY, AND PERFECTION ARE PART OF PREDISTINATION (QADAR):
Order and harmony are not accidental. They are part of deliberate creation. The perfection seen in human biology are not a result of accidental coincidence. They are part of Allah’s grand pre-design and could not have occurred as a result of incremental evolutionary adjustment. Random probability is too low to create the sophisticated human biological system. Denying the existence of a creator is an intellectual and mental aberration that can not be explained logically. The very perfection and harmony of the creation is a direct proof that a powerful creator exists.
BEAUTY OF CREATION (JAMAL AL KHALQ):
All what Allah created is beautiful and is pleasing to see. Humans with distorted perception may not be able to see this beauty in everything. Racists who see ugliness in other races or ethnic groups are blinded to this beauty. Many can not see the beauty of the physical world around them and therefore can not enjoy it. This is not because the eyes are blind but because the hearts are blinded by deficiency of faith (22:46). Beauty manifests in static as well as dynamic phenomena. There is grace and beauty in the movement of plants and animals and the changes that they undergo. There is beauty in physical features like mountains, rivers, lakes, and space. There is beauty in biological entities like humans, animals and plants. The Qur’an describes this esthetic beauty (16:6, 17:7). For humans female beauty is emphasised in a special way ( 25:221, 1231, 33:52, 55:70, 55:76, 63:4. MB # 1210 p 582, #1786 p 868-9). This emphasis is probably related to the purpose of procreation and family-raising as will be explained later.
THE CONSTANT PHYSICAL LAWS:
The laws of the inanimate world apply in biology in the same way with only difference of purposiveness and dynamic initiative that are found only in living things. These two qualities are most developed in humans.
PERFECTION AND POWER (QUDRAT):
Only the most powerful could achieve perfection. Humans are perfect because they were created by Allah, the most high and most powerful. Human handiwork can not be perfect because humans are not all-powerful.
UNIQUENESS:
Every human is unique and is different from everybody else. This also applies of organs and tissues. Each DNA is different. This testifies to the power of the creator able to create everything as unique. Thus creation is not a process of copying from a template as humans do but a deliberate act for each individual organism, organ, cell, or sub-cellular structure.
B. OPTIMALITY (AHSAN TAQWIIM):
The best creation (ahsana taqwiim) 95:4: All biological systems are optimal. No more effective or more efficient system can even be imagined. Any human organ or system being perfect. It is not possible to think of a way of making them better than what they are. The difference between the optimum and the maximum must be made clear. The optimum is a balance situation such that the combination of attributes is the best that it can be and no better combination can be imagined. Some attributes in the combination may not be the maximum. Humans are not the best in everything. They may have weaknesses that are compensated for by other strengths this being the most optimal way. The brain and intellect are the best compensatory mechanisms. Human biological superiority is sophistication and not quantity, size, or physical strength.
The human body is optimal. There are no useless or superflous organs or tissues. Organs and tissues habe multiple functions. Comparison of similar but different parts of the human body indicate the optimal adaptation of each for its specialized functions. Examples are the upper limb (mobility) and lower limb (power & stability), pectoral girdle (mobility) vs pelvic girdle (immobility and stability), shoulder (fine movements) vs hip joint (stability and firm movements). Comparison of the 2 genders shows differences that are optimal for specialised gender function: height, muscld mass, bone structure, and skin structure. IN general each variation is the best adaptation to the expected function. Geographical variation in human skin pigmentation also shows the optimal adaptation to the sun. Darker races live in hotter climates. Lighet-colored races live in the colder climates of the northern hemisphere and have less melanin. Human attempts to change Allah’s creation is always frought with problems because of human inability to understand the optimal balance. Use of drugs (depressants, narcotics, stimulants, hallucionogens, alcohol) and cosmetic surgery will lead to adverse consequences that will become clear with time.
C. CHANGE AND CONSTANCY:
Change is governmed by natural laws (sunan llah). There is a balance between constancy and change. There is constant change in biology; nothing remains static for any length of time. Yet amidst this change there is constancy which is a reflection of the creator’s laws in creation (sunan al llah fi al kaun). This change however diverse follows those laws. There is a dynamic equilibrium. Things are not static. The level of equilibrium can change. The law of change also covers Fixed unvarying phenomena. There are a few things that are fixed and do not change and these are usually pre-determined pre-natally. Examples are Allah's convenant with humans before birth (‘ahd llah ila al bashar, 7:172-173, 36:10), fixed lifespan (‘umr, 35:11), sustenance (rizq, 43:32), and aspects of character (shaqaa & sa'adah). Humans undergo changes over time. These changes do not amount to a change from one species to another as the theory of evolution stipulates. Adam was for example 70 feet tall (MB # 1399 p 658). Recorded heights of Europeans in the past 5 centuries have shown increasing stature. There is recorded increased average stature of Japanese over the past 50 years.
D. DNA AS A BASIS FOR PREDICTABILITY OF BIOLOGICAL PHENOMENA:
DNA is very simple in composition being made up of only 4 base-pairs. The complexity and uniqueness of each organism's DNA arises in the way those base-pairs are arranged, the sequencing. We now know a lot about DNA. Its genetic code was broken by the 1970s using several technics: (i) use of restriction endonecleases that by selective hydrolysis enabled sequencing, cleavage, and producing of restriction maps (ii) nucleic acid probes used to identify specific DNA/RNA sequences (iii) recombinant DNA technology. The functions of DNA are control of all aspects of cell functioning primarily through protein synthesis transfer hereditary information to the next generation. Protein synthesis involves translation of information from the 4-letter language of nucleic acids into the 20-letter language of amino acids. With the help of rRNA, mRNA (also called codon) is formed by the process of transcription from DNA. The templates for protein synthesis are provided by mRNA. By a process of translation, tRNA (also called anti-codon) is formed from mRNA and has the function of transferring amino acids to ribosomes for protein assembly. A codon is a 3-letter sequence. More than one codon is needed for each protein. Some of the sequences are punctuations. Both parents contribute equally to the chemical structure of DNA. DNA is the ultimate basis of the Qur'anic concept of nutfat which refers to both the male and female sexual fluids (16:4, 18:37, 23:13-14, 25:54, 32:8, 35:11, 36:77, 53:46, 75:37, 76:2, 77:20, 80:19, 86:6). DNA is far superior to the memory of any known human-made computer. More than 99% of the human genome is similar among all humans. The great variability seen is only in a few segments. DNA within one organism is quite stable. The processes of mitosis and meiosis occur in millions of cells daily with few variations. To ensure statbility DNA replication is semi-conservative. The transcription of the genetic code and its translation into protein molecules is accurate after many repetitions. There are mutations due to irradiation and mutagens. They may take any of 4 forms: point mutations, mis-sense, non-sense, and frame-shift mutations. Mutations are rare given the number of cell divisions. Many metabolic processes are also under genetic control.
E. INCOMPARABILITY
FAILURE OF COMPETITORS (‘AJZ AL SHURAKAA):
Pretension to divine attributes has happened in two ways: worhsip and biology. Worship of many gods causes much confusion because it is not logical. If there were more than one creator for the complex universe, the order and harmony that we see would not have happened. Although humans know that none beside Allah can create and perfect, yet they persist in worshipping things other than Allah as if they also are creators. Thus the human body can not be compared with any other biological system. The Qur’an challenged humans and other creations to create the like of Allah’s creation and proved them incapable of facing the challenge 7:191, 10:34, 13:16, 16:17-21, 22:73, 25:3, 31:115, 35:40, 46:4, 25:35-36. Cloning, genetic engineering, and selective breeding are not de novo creation.. No human or any other being can create new life, ‘ajz al shuraka ‘an al khalq (7:191, 10:34, 13:16, 16:17-21, 22:73, 25:3, 31:11, 35:40, 46:4, 25:35-36). Human actions are imperfect. Comparison of the human body and the human-made machine shows this clearly.
FUTILE ATTEMPTS AT COMPARABILITY:
(a) There is no comparison in biological systems. Humans have not been able to produce an independent biological system to compare with Allah’s creation. The only possible comparison is between the human body and machinery. (b) There is no comparability in physical systems: human eye vs camera, ear vs recording microphone, nose and lungs vs air-conditioning. The human eye and the video camera have similar processes. In both the mage is focussed at a spot in case of te eye the fovea centralis. In both the image is converted into electrical impulses. The impulses are stored in the human brain and on magnetic tape in the video. The brain decodes the image. The tape can be decoded to be visualised. Howeve the video camera beyond these few similarities can not in any way approach the sophistication of the human senses. (c) There is no comparability in chemical systems: eg liver metabolism vs chemical reactions. Human DNA in one cell if strecthed out would measure about 1 meter. It is responsible for tight control of so many metabolic processes. Nothing like this can be quoted in human-made chemical systems (d) There is no comparability in mechanical systems: The human musculo-skeletal system is far superior to the pulley and lever systems when we consider criteria of mechanical advantage and mechanical efficiency (work done/enrrgy expended). The mechanical efficiency of muscles is 50%. Muscle contraction produces heat which is not lost energy because it is needed to maintain body temperature. The heart is a very efficient mechanical pump that operates for decades without rest or the need for repair (e) Energy systems: The Krebs’ cycle is more efficient than the internal combustion engine.
6.1.2 MANIFESTATIONS: ANATOMY
A. THE CELL
The cell: The human body is made up of small particulate parts. The particulate nature of the body is implied in the Qur;anic term (jam’u al idhaam). The human body has 10E14 cells (Bowman p. 4.1). All the basic processes of life are found in the cell. These cellular functions replicate all physiological functions of the whole organism: transport, synthesis, respiration, excretion, mobility, energy use & storage (Devlin p. 17). Thus Allah is able to expand (yabsit) and compress (yaqbidh) as He wishes. The same functions could be at a macro level or at a micro level. Cells are surprisingly similar in structure and function despite the differences in location and specialisation. The same cellular DNA has different effects in different cells. Each cellular compartment is specialised for particular functions. Study of the cell illustrated the Qur’anic teaching that water is the origin of all life ( ). All cellular chemical reactions occur in a water milieu. Water is the universal solvent.
The creation of the cell: The process of combining the basic elements of O, H, C, N,and P to make the basic cellular structure could not be random. Allah created the cell in a purposive way as part of the human organism. The complexity and specialisation of cells was created and could not be a chance evolutionary event. There have been many arguments between creationists and evolutionists. It is not possible to set up an experiment to settle the argument either way because the phenomena concerned are part of human biological history and can not be tested empirically today. The answer can only be found in revelation (wahy).
The cell membrane: Cell membranes are very dynamic. They consist of protein and lipids. They exclude things from entering the cell but do selectively transport some molecules. They regulate the metabolic pathways by regulating the translocation of substrates, co-factors, and ions. Movements across the cell membrane can be by (a) passive by diffusion or can be (b) active requiring energy for the transportation system.
B. PARITY, SYMMETRY, and LATERALITY
PARITY
Parity is one of the constants of creation (sunan al Llah fi al khalq) (11:40, 23:27, 30:36, 43:12, 51:49). The female and male gender parity is one special case of parity that is essential for a normally-functioning human society (92:3, 3:36, 3:195, 4:1, 4:11, 4:124, 4:186, 7:189, 16:97, 30:21, 35:11, 39:6, 40:40, 42:11, 42:50, 49:31, 53:45, 75:39, 78:8). Males and females are a garment for one another (7:189). Most human organs occur in pairs (12:84, 15:88, 18:28, 18:57, 20:131, 31:7, 78:40, 90:8-10, 111:1). Even single organs like the heart, the uterus or the brain have distinguishable left and right portions; they were paired organs early in embryological development and became fused into one organ later in life. Paired organs are not always exactly the same. The phenomenon of parity is also found in animals (39:6, 42:11), plants (13:3, 20:53, 22:5, 26:7, 31:10, 50:7, 55:52), and the phenomena of day and night (25:164). Parity in the human body serves many purposes. It creates balance and harmony. The paired organ or structure is a spare one in case the other is indisposed. The basic hereditary material of the cell, DNA also illustrates this parity in that it exists in a double helix. The 23 human chromosomes are also in pairs.
SYMMETRY
Both circular and lateral symmetry are a constant feature of creation. Human handiwork can create works of beauty by using symmetric patterns. Yet human endeavors are very far from Allah’s creation.
LATERALITY OF LEFT AND RIGHT:
The Qur’an discussed laterality in several verses: 7:17, 16:48, 17:71, 20:17, 20:69, 29:48, 50:17, 57:12, 60:8, 69:19, 84:7-8. There is a difference in strength and use between the right and left sides of the body that reflects hemispheric dominance. Islamic culture also emphasizes this laterality. The right side is preferable to the left one. The right hand is preferred in eating and greeting. The left hand is used exclusively for matters of personal hygiene (Muslim #514, 515). Sleeping is preferably on the right side of the body. Wearing shoes is started with the right and putting them off is started with the left.
C. COMPLEXITY WITH SIMPLICITY:
A student of anatomy is amazed at the detail and complexity involved even in the smallest organs. The central nervous system or the knee joint require several pages of writing and illustrations to describe fully. Alongside this complexity is a basic simplicity. The complexity is based on a few simple phenomena. The complex human body is made up of cells as basic units of life. The cell is the basic building block. It is a miracle that the complex human body is composed of these tiny components that are in themselves very complex systems. The DNA molecule controls all the myriad functions of the cell. The many comlex differences between males and females are due to a single pair of chromosomes, X & Y, and two glands, the ovary and the testis. Even the complex metabolic processes have simple end-products: glucose, amino acids, and fatty acids. At the intellectual level the co-existence of simplicity with complexity has been put to good use by humans. Study of the simple microorganisms helps understand the more complex organisms. It is conceptually wrong to refer to humans and mammals as higher organisms and the prokaryotes as lower organisms. There is no superiority based on biological characteristics. Everything that Allah created was perfect it its own way and none can be considered biologically inferior.
D. ADAPTATION and VARIATIONS
Adaptation of structure to function: Human tissues are specialized: nervous, muscle, epithelial, and connective. Structure determines function and vice versa. Ventricles of the heart have thicker muscles than auricles because they do more work. Similarly the left ventricle has thicker walls than the right ventricle because it performs more work. The ovoid configuration of the erythrocyte and the large surface area are optimal for diffusion. The surface area of the erythrocyte is 138 cubic mu. A sphere of the same volume would have a surface area of 95 cubic mu. The perfect match between structure and function of various tissues and organs was created by Allah de novo and did not arise as a result of evolutionary adaptation. All was pre-conceived in Allah’s grand design for creation.
Variations in structure and function: Perfection does not exclude variations. No two individuals are exactly alike. There are differences due to age, sex, race, genetic inheritance, and environmental effects. There are also differences in the same individual among paired organs. These differences are however within the perfect scheme of creation.
Consistency and Predictability:
Biological structure and function are consistent within species and across species. This consistency is the basis of predictability of biological phenomena.
E. CHANGES
Staging: Many anatomical processes occur in phases. This is Allah’s plan to make sure that there is perfect interaction with the environment. For example the mitotic division of the cell has 4 phases: inter-phase (G1=cell growth and DNA synthesis, G2=DNA replication, G3=growth), prophase, metaphase, and telophase. Embryological development is staged. Chemical and metabolic processes occur in phases. Allah had the power to make these processes occur in one step. He however had a higher purpose to let them proceed in phases.
Anticipation: Close study of the anatomical structure and its variations reveals that there is anticipation of physiological and pathological changes. For example the brain is supplied by the carotid and vertebral arteries that are inter-connected in the circle of Willis. Blockage of either the carotid of the vertebral arteries does not cut off the brain blood supply because of existence of a collateral supply. The brain is the most vulnerable organ to hypoxia. Its total blood flow is 750 ml/mn. Consciousness is lost at blood flow less than 450 ml/min and is irreversible if blood flow is less than 350 ml/min. The carotid sinus reflex and the medulla oblongata ischemic reflexes are protective of the brain circulation and will trigger corrective action when the blood pressure or oxygen content decrease.
Protection: All human structures are created with mechanisms that protect them from anticipated injury. There are basically 5 protective systems: (a) mechanical eg. The cranium protects the brain, the pleural, peritoneal, and pericardial membranes protect organs and viscera that they enclose (b) secretions eg ear-wax (c) natural/in-born non-specific immunity that may be cellular eg phagocytes, mast cells, neutrophils or humoral eg complement, lysozymes, interferon (d) acquired immunity that may be cellular (B-lymphocytes, T-lymohocytes, Natural Killer cells ) or humoral .
6.1.3 MANIFESTATIONS: PHYSIOLOGY, BIOCHEMISTRY, & PHARMACOLOGY
A. PHYSIOLOGICAL ENTITY
Physiological entity: The Prophet Muhammad (PBUH) described the human body as a single physiological entity such that if any part is afflicted the rest of the body is also affected and it responds (MB# 2018 p. 955). This is in accord with the current physiological and pathological concepts of systemic involvement and co-ordination between different organs and systems of the body. This description of more than 14 centuries ago fits very well with the modern concepts of systemic effects of local pathology that disturbs the balance.
Correlation between anatomy and physiology: Each cell, tissue, or organ is adapted structurally to its function. It is impossible to find any structure in the body that has no function. This is an illustration of the purposiveness of creation in that Allah did not create anything that has no function.
B. CHARACTERISTICS OF PHYSIOLOGICAL PHENOMENA
Repeatability/replicability: All biological phenomena are repeatable exactly many times with no mistakes which shows that there is accurate and effective control.
Specificity: Organs and tissues have specific functions. This specificity extends to the cellular and sub-cellular level. For example neural transmitters and other types of hormones attach to cell receptors to cause their respective effects. These receptors are highly specific.
Specialisation: The body has specialised systems. The GIT undertakes digestion and absorption. The respiratory systems takes up oxygen and eliminates carbon dioxide. The excretory system eliminates metabolic wastes. The cardio-vascular system distributes food and oxygen to all parts of the body, transports hormones, and removes wates from tissues. The reproductive system ensures perpetuation of the species. The nervous and endocrine systems control and co-ordinate bodily functions.
Complementality: The delicate specialisation of the various systems does not preclude complementality. Almost any one activity or process involves many systems such that one system completes or perfects what another started. For example the contraction of a skeletal muscle requires co-ordinates action by biological, electrical, and chemical phenomena.
Co-operation: There is a high degree of co-operation between the various organs and tissues of the body. This is best illustrated in the co-operation between B and T cells in the modulation of immune reactions. The cardio-vascular and respiratory systems cooperate well. This is illustration of the prophet's saying that the body is one physiological entity such that when any part is afflicted the whole body suffers.
Hierarchy of importance: The functions, locations, and special peculiarities of each organ indicate its relative importance in the physiology of the human body. The brain and the heart for example have more protection from mechanical damage than other organs.
Information processing/perception: Ability to collect and integrate information of various kinds is the basis for the integrated functioning of the body.
C. PHYSIOLOGICAL ANTICIPATION
Reserve capacity in organs: Each organ is made with excess functional capacity which anticipates both physiological and pathological situations that call for increased work. The excess capacity anticipates disease conditions that may destroy part of an organ so that the remaining part is able to sustain function. Parity of organs is also part of the functional reserve.
Compensation for overload: Each organ or body system has inbuilt mechanisms that enable it to adjust rapidly and efficiently to situations of increased demand.
D. CHEMICAL STRUCTURE
Few basic building blocks: A few amino acids are the basic building blocks for the complex proteins. Similarly the basic building blocks of carbohydrates and lipids are simple sugars and fatty acids.
The ubiquitous water molecule: The hydrogen bond is perhaps the most important one in biochemistry. Water the basis of life is the best solvent because of its polarity that makes it possible for it to form hydrogen bonds. Water is a weak electrolyte and is thus able to play a major role in the acid-base balance of the body.
Chemistry and life: The artificial synthesis of urea in 1928 was a momentous event because it showed that compounds in living things can be synthesized in the laboratory. Biological phenomena that constitute life are in essence based on many chemical reactions. Humans can carry out many or all of those chemical reactions. It is not however possible for a human to create life by replication of these chemical reactions. This is because there is a missing dimension that alone confers life as we know it and that comes only from the handiwork of Allah the almighty. The purposiveness, organisation, and integration of life are more than the sum of its component chemical reactions.
Chemical bonds: It is possible to predict the chemical reactions of molecules by knowing the type of chemical bonds.
Symmetry: Study of stereo-chemistry shows that stereo-isomers which differ only in the symmetrical disposition of some atoms or bonds have different chemical properties.
E. CHEMICAL REACTIONS
The periodic table of elements: The discovery of the periodic table of elements is one of the strong indicators that there is order in the universe. It is possible to predict properties or elements and chemical reactions from the position of elements in the table. It is also possible to predict to a high degree of accuracy properties of elements not yet discovered.
Enzymes: Enzymes catalyse chemical reactions by decreasing the activation energy. The enzyme is not changed in the course of the reaction. It does not change the equilibrium constant, it only increases the speed of reaching equilibrium. The apoenzyme is part of the enzyme that is catalytically inactive. Co-factors ae small organic or inorganic molecules that that the enzyme requires of its action. A prosthetic group is similar to the co-factor but is more tightly bound to the apoenzyme. The complex of the apoenzyme and co-factor or prosthetic group is called a haloenzyme. Enzymes are specific because they have specific substrate binding sites. Depending on the reactions that they catalyse, enzymes can be classified as : oxido-reductases, transferases, hydrolases, lyases, isomerases, and ligases. Enzyme saturation kinetics can be described precisely by mathematical equations. Enzymes inhibition can be competitive, non-competitive, and uncompetitive.
Metabolism of new synthetic molecules: The finding that synthetic molecules can be metabolized by the biological systems indicates the existence of a unifying scheme of creation based on sunan al laahi fi al kawn.
Cyclicity: the urea cycle which operates to eliminate excess ammonia gives us a good example of cyclicity. The carrier molecule ornithine is regenerated after formation of each molecule of urea.
6.1.4 PATHOLOGY
A. CONCEPT
Pathology is a study of disease processes, etiology, pathogenesis, morphological changes, and clinical significance.
B. ETIOLOGY
Etiology can be intrinsic or extrinsic. Usually more than one cause is involved. The final path of etiological mechanisms is some form of injury to the cells of the body.
C. CELL INJURY
Among the causes of cell injury are: hypoxia, physical agents (heat, pressure, radiation, electricity), chemical agents, drugs, infections, immunological reactions, genetic disorders, nutritional imbalances. The concept of the common pathway in cell injury relates well to the concept of sunan. Different injuries to the cell cause the same or similar cell injuries, the common final path. Some cell injury is due to cell death by apostosis. Apostosis differs from necrosis because it is under genetic control. Examples of apostosis include: the programmed destruction of embryonic cells, hormone dependent organ or tissue involution in adults, cell death in tumors. Some diseases are due to intracellular accumulation of metabolic products for example steatosis or fatty change, atherosclerosis, xanthoma, immunoglobulin accumulation, glycogen accumulation in diabetes mellitus, and accumulation of pigments like lipofuschin, melanin, hemosiderin, and bilirubin. Injured tissues may either be regenerated or may be replaced by fobroplasia (connective tissue).
D. BODILY RESPONSE TO INJURY
Molecular or structural alterations in cells underly all forms of organ or tissue injury. Pathologic stimuli disturb normal homeostasis. Injured cells adapt by atrophy or hypertrophy. Injury results when adaptation fails. Injury may be reversible or irreversible. Irreversible injury leads to cell death.
6.1.5 BIOSTATISTICS AND EPIDEMIOLOGY
A. NUMBERS: COUNTING and MEASURING
B. PROBABILITY THEORY
Probability theory that enables computation of theoretical probabilities that predict empirical probabilities is another indication of the sunan.
C. CONSISTENCY OF NATURAL PHENOMENA
Normal distribution: indicates the predictability of biological phenomena. The definition of disease on a continuum
Sampling theory
D. MODELS and PREDICTION
Regression and prediction
E. INFERENCE and CAUSALITY
Causal relations
Statistical inference: the level of significance (alpha) and the level of confidence (1-alpha) are widely used in classical statistics. They have a basis in real life and are a manifestation of the sunan.
Statistics is concerned with human bias. Several technics have been developed to remove or decrease human bias: randomisation with stratification, cross-over studies, and double -blind studies to avoid observer bias. These methods remove human bias so that sunan can operate without distortions by the human will.