Lecture 1 Introduction Cell TBW And Homeostasis PDF

Introduction, cell, TBW and homeostasis Lecture 1 Introduction, cell, TBW and homeostasis 1. Introduction Human physiology is the study of how the human body functions, including the physical and chemical processes that occur with...

Introduction, cell, TBW and homeostasis Lecture 1 Introduction, cell, TBW and homeostasis 1. Introduction Human physiology is the study of how the human body functions, including the physical and chemical processes that occur within different body systems. Physiology helps us understand how the body responds to stimuli and maintains internal balance, also known as homeostasis. In essence, physiology focuses on the characteristics and mechanisms that define life, aiding in adaptation and maintaining balance, two fundamental features of living organisms. Levels of Organization in the Body The human body is composed of various levels of organization: 1. Chemical Level: o Atoms such as oxygen, carbon, hydrogen, and nitrogen account for about 96% of the body's chemistry. These atoms combine to form essential molecules like proteins, carbohydrates, fats, and nucleic acids (e.g., DNA). 2. Cellular Level: o Cells are the basic units of life, capable of carrying out the processes associated with life. They are the foundation of all body structures and functions. 3. Tissue Level: o Tissues consist of specialized cells. There are four primary types of tissues: muscle, nervous, epithelial, and connective tissue. 4. Organ Level: o Organs are composed of different tissues working together to perform specific functions, like the stomach, which contains all four tissue types. 5. System Level: o A system is a collection of organs that work together to perform activities essential for survival, such as the digestive or circulatory systems. 6. Organism Level: o The body is composed of integrated systems that work as one functional unit, each system depending on others for proper functioning. 2. Cell physiology 2.1 Overview of the Cell The cell is the basic structural and functional unit of all living organisms and the smallest living entity capable of performing all essential life processes. Despite their microscopic size, cells carry out complex functions such as energy production, waste removal, and reproduction. While cells can vary in size and shape based on their specific functions, they all share several common structural components. 1 Wadi Al-Shati University, College of Medical Technology, Department of Medical Laboratories. By Walaa Al-Azhari, M.Sc.  Introduction, cell, TBW and homeostasis 2.2. The Structure of the Cell Each cell is composed of several distinct structures, each with a specific function, contributing to the overall homeostasis of the body. The primary components of a typical cell are the plasma membrane, cytoplasm, organelles, and the nucleus. 2.2.1 The cell membrane The cell membrane, or plasma membrane, is a fundamental structure in all living cells, acting as a barrier between the intracellular and extracellular environments. It regulates the movement of substances in and out of the cell. Beyond its protective function, the membrane plays a crucial role in communication, transport, and maintaining cellular homeostasis. It is typically 7.5 to 10 nm thick, composed of a lipid bilayer with embedded proteins, carbohydrates, and cholesterol molecules, which help regulate interactions with the external environment. 2.2.1.1 Structure of the Cell Membrane The cell membrane is composed of various components, each contributing to its structural integrity and function. 2.2.1.1.1 The Phospholipid Bilayer The basic structure of the cell membrane is a phospholipid bilayer. Phospholipids are amphipathic molecules, meaning they contain both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions.  Hydrophilic Heads: These are polar and face the aqueous environments inside (cytoplasm) and outside (extracellular fluid) of the cell.  Hydrophobic Tails: These nonpolar fatty acid tails face inward, away from water, forming the core of the membrane. This bilayer arrangement makes the membrane selectively permeable, allowing only certain substances to pass through. 2.2.1.1.2 Cholesterol Cholesterol molecules are interspersed within the phospholipid bilayer. They provide stability and fluidity to the membrane by preventing the fatty acid tails of the phospholipids from packing too tightly. This flexibility is crucial for maintaining the cell membrane’s integrity, particularly under varying temperature conditions. 2.2.1.1.3 Membrane Proteins Membrane proteins are either embedded within the lipid bilayer or associated with the membrane's surface. They account for nearly half the mass of the cell membrane and perform many key functions. 2 Wadi Al-Shati University, College of Medical Technology, Department of Medical Laboratories. By Walaa Al-Azhari, M.Sc.  Introduction, cell, TBW and homeostasis  Integral (Transmembrane) Proteins: These proteins span the entire membrane and have domains exposed to both the intracellular and extracellular environments. They are involved in transport, signal transduction, and cellular communication. Examples include ion channels, transporters, and receptors.  Peripheral Proteins: These are attached to either the inner or outer surface of the membrane and are involved in structural support, signaling, and maintaining the cell's shape. Specialized Functions of Membrane Proteins Membrane proteins are essential for specific cellular activities, including: Ion Channels Ion channels are proteins that allow specific ions to pass through the membrane. These channels are selective, meaning they only allow certain ions (e.g., Na+, K+, Ca2+) to move across the membrane. Types of ion channels include:  Voltage-gated channels: Open or close in response to changes in membrane potential.  Ligand-gated channels: Open or close when a specific molecule (ligand) binds to them.  Mechanically-gated channels: Open in response to mechanical forces, such as stretching or pressure. Transporters and Pumps Transporters move substances across the membrane, while pumps actively transport ions or molecules using energy. Examples include:  Sodium-potassium pump (Na+/K+ ATPase): Actively transports sodium out of the cell and potassium into the cell.  Glucose transporters (GLUTs): Facilitate the movement of glucose into the cell. Enzymatic Activity Some membrane proteins function as enzymes, catalyzing reactions at the cell surface. For example, certain enzymes in the plasma membrane convert precursor molecules into active signaling molecules. 2.2.1.1.4 Carbohydrates Carbohydrates are often attached to proteins (glycoproteins) or lipids (glycolipids) on the extracellular surface of the membrane. Collectively, these form the glycocalyx, a protective and recognition layer. 3 Wadi Al-Shati University, College of Medical Technology, Department of Medical Laboratories. By Walaa Al-Azhari, M.Sc.  Introduction, cell, TBW and homeostasis  Glycocalyx: This is involved in cell-cell recognition, communication, and adhesion. It also protects the cell from mechanical and chemical damage. 2.2.1.2. Functions of the Cell Membrane The cell membrane is involved in various essential functions: 1. Selective Permeability: The cell membrane regulates the movement of substances into and out of the cell, allowing some molecules to pass while restricting others. Small, nonpolar molecules (like oxygen and carbon dioxide) can easily diffuse through, whereas polar molecules and ions (such as glucose and sodium) require specific transport proteins. 2. Barrier Function: It acts as a protective barrier, separating the internal environment of the cell from the external surroundings. 3. Cell Communication: The membrane contains receptors that facilitate communication between cells by receiving signals from hormones and other molecules. 4. Signal Transduction: The membrane plays a role in transmitting signals from the external environment to the interior of the cell, influencing cellular responses. 5. Transport Mechanism: It allows substances to move across the membrane through both passive (diffusion, facilitated diffusion) and active transport (requiring energy). 6. Cell Recognition: The presence of glycoproteins and glycolipids aids in cell recognition and adhesion, which is crucial for tissue formation and immune response. 7. Maintaining Shape: It contributes to the structural integrity and shape of the cell through interactions with the cytoskeleton. 8. Endocytosis and Exocytosis: The membrane is involved in processes like endocytosis (bringing substances into the cell) and exocytosis (expelling substances from the cell). 2.2.1.3. Transport Mechanisms Transport across the cell membrane occurs via passive or active mechanisms:  Passive Transport: No energy is required, and substances move down their concentration gradient. This includes: o Simple Diffusion: Movement of small, nonpolar molecules like O₂ and CO₂. o Facilitated Diffusion: Movement of larger or polar molecules (e.g., glucose) through a protein channel or carrier. o Osmosis: The diffusion of water across a semipermeable membrane. 4 Wadi Al-Shati University, College of Medical Technology, Department of Medical Laboratories. By Walaa Al-Azhari, M.Sc.  Introduction, cell, TBW and homeostasis Osmosis Osmosis is a vital process that occurs within cells and their surrounding environment. It is defined as the movement of water molecules across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration.  Mechanism: Water molecules naturally move to balance the solute concentrations on both sides of the membrane. This balance ensures a stable environment for the cell, allowing it to perform its essential functions effectively.  Osmotic Pressure: This refers to the force or pressure required to prevent water from moving into the area with a higher solute concentration. Osmotic pressure increases as the difference in solute concentration grows. It is crucial in ensuring that cells do not swell excessively or shrink due to changes in surrounding solute concentrations.  Importance of Osmosis: o Maintains cell volume. o Regulates fluid pressure inside and outside the cell. o Protects cells from sudden environmental changes, whether it involves an increase or decrease in water availability.  Active Transport: Requires energy (usually ATP) to move substances against their concentration gradient. o Primary Active Transport: The sodium-potassium pump (Na+/K+ ATPase) is a key example, maintaining high intracellular potassium and low intracellular sodium concentrations. o Secondary Active Transport: Uses the energy from the movement of one substance down its gradient to transport another substance against its gradient (e.g., sodium-glucose symporters).  Vesicular Transport: o Endocytosis: The process by which cells engulf large particles, liquids, or even other cells. Examples include phagocytosis (cell eating) and pinocytosis (cell drinking). o Exocytosis: The release of substances from the cell through vesicle fusion with the membrane. This is how cells secrete hormones, neurotransmitters, and enzymes. 2.2.1.4. Maintenance of Membrane Potential The cell membrane is essential for the maintenance of the resting membrane potential, which is crucial for the functioning of nerve and muscle cells.  The inside of the cell is more negatively charged compared to the outside, primarily due to the distribution of ions (mainly Na+, K+, and Cl-).  The Na+/K+ ATPase pump actively transports sodium ions out and potassium ions into the cell, maintaining a negative resting potential.  This potential is critical for the generation and conduction of action potentials in excitable cells (e.g., neurons and muscle cells). 5 Wadi Al-Shati University, College of Medical Technology, Department of Medical Laboratories. By Walaa Al-Azhari, M.Sc.  Introduction, cell, TBW and homeostasis Action Potentials An action potential (AP) is a rapid, temporary change in the membrane potential of excitable cells, such as neurons, muscle cells, and some gland cells. It is the fundamental mechanism by which these cells transmit signals across distances. The process involves a series of phases: depolarization, repolarization, and sometimes hyperpolarization. 1. Resting Membrane Potential  Before an action potential occurs, the cell is at its resting membrane potential, typically around -70 mV for neurons. This potential is maintained by the selective permeability of the cell membrane and the activity of ion pumps like the sodium-potassium (Na⁺/K⁺) pump. The interior of the cell is more negative compared to the extracellular space due to the higher concentration of negatively charged proteins and other ions. 2. Depolarization: o Before reaching the threshold, a few voltage-gated sodium channels open. o These channels have two gates: the activation gate and the inactivation gate. o During depolarization, the activation gate opens quickly, allowing sodium ions (Na⁺) to enter the cell. This leads to a rapid increase in positive charge inside the cell. o Once the membrane potential reaches the threshold (approximately -55 mV), more sodium channels open, accelerating depolarization until the potential reaches its peak (+30 to +40 mV). 3. Repolarization o Shortly after the activation gate opens, the inactivation gate of sodium channels begins to close, stopping the flow of sodium into the cell. o Simultaneously, voltage-gated potassium channels open, which have a single activation gate. This gate opens slowly, allowing potassium ions (K⁺) to exit the cell, helping to restore the membrane potential to its negative state. o Potassium continues to flow out of the cell until the membrane potential approaches -70 mV (the resting potential).  Depolarization: Sodium channels open (activation gate) → Na⁺ enters → the internal charge becomes positive.  Repolarization: Sodium channels close (inactivation gate) + Potassium channels open (activation gate) → K⁺ exits → the internal charge returns to negative 4. Hyperpolarization 6 Wadi Al-Shati University, College of Medical Technology, Department of Medical Laboratories. By Walaa Al-Azhari, M.Sc.  Introduction, cell, TBW and homeostasis  Often, the outflow of K⁺ overshoots the resting potential, making the membrane potential more negative than the resting state (hyperpolarization). This is a result of the slow closure of K⁺ channels. The membrane potential may drop to around -80 mV before stabilizing back to the resting potential. 5. Refractory Period During and immediately after an action potential, the neuron enters a refractory period where it is less responsive to new stimuli. This is divided into two phases:  Absolute Refractory Period: No new action potential can be initiated, regardless of the strength of the stimulus, because the sodium channels are inactivated.  Relative Refractory Period: A new action potential can be initiated, but only by a stronger-than-usual stimulus, as some sodium channels have reset, but the membrane is still hyperpolarized. 2.2.2. Cytoplasm The cytoplasm is the gel-like substance inside the cell, in which the organelles are suspended. It is composed of water, salts, and organic molecules.  Cytosol: The liquid portion of the cytoplasm, containing ions, nutrients, and enzymes essential for cellular reactions.  Cytoskeleton: A network of protein filaments (microfilaments, intermediate filaments, and microtubules) that provide structural support, maintain the cell's shape, and facilitate movement within the cell. 2.2.3. Organelles Organelles are specialized structures within the cell, each with a specific role in maintaining cellular function. 2.2.3.1. Mitochondria Mitochondria are often referred to as the "powerhouses" of the cell. They generate the majority of the cell’s ATP (adenosine triphosphate) through aerobic respiration, a process that involves the oxidation of nutrients to produce energy.  Structure: Mitochondria have a double membrane. The inner membrane is folded into structures called cristae, which increase the surface area for energy production.  Function: Mitochondria produce ATP via the citric acid cycle (Krebs cycle) and oxidative phosphorylation. They also play roles in apoptosis (programmed cell death) and calcium storage. 2.2.3.2. Endoplasmic Reticulum (ER) 7 Wadi Al-Shati University, College of Medical Technology, Department of Medical Laboratories. By Walaa Al-Azhari, M.Sc.  Introduction, cell, TBW and homeostasis The endoplasmic reticulum is a network of membranous tubules and sacs involved in protein and lipid synthesis.  Rough ER (RER): Studded with ribosomes, the RER is primarily involved in the synthesis of proteins, which are then transported to the Golgi apparatus for modification and sorting.  Smooth ER (SER): Lacks ribosomes and is involved in lipid synthesis, detoxification of drugs, and calcium storage. 2.2.3.3. Golgi Apparatus The Golgi apparatus functions as the cell's "post office." It modifies, sorts, and packages proteins and lipids for delivery to their final destinations within or outside the cell.  Structure: Composed of flattened sacs called cisternae.  Function: Receives proteins and lipids from the ER, modifies them (e.g., glycosylation), and packages them into vesicles for transport. 2.3.3.4. Lysosomes Lysosomes are membrane-bound organelles containing digestive enzymes. They break down waste materials, cellular debris, and foreign substances that enter the cell, such as bacteria.  Autophagy: Lysosomes are involved in the breakdown of damaged organelles and recycling their components. 2.3.3.5. Peroxisomes Peroxisomes are small, membrane-bound organelles that contain enzymes involved in the detoxification of harmful substances, such as hydrogen peroxide (H₂O₂). They also play a role in lipid metabolism. 2.3.3.6. Ribosomes Ribosomes are the sites of protein synthesis. They can be found free-floating in the cytoplasm or attached to the rough ER. They translate genetic information (mRNA) to form polypeptides. 2.2.4. The Nucleus The nucleus is the control center of the cell, containing the cell’s genetic material (DNA) and directing all cellular activities. 8 Wadi Al-Shati University, College of Medical Technology, Department of Medical Laboratories. By Walaa Al-Azhari, M.Sc.  Introduction, cell, TBW and homeostasis  Nuclear Envelope: A double membrane that encloses the nucleus. It has nuclear pores that regulate the exchange of materials (e.g., RNA and proteins) between the nucleus and the cytoplasm.  Chromatin: The form in which DNA exists when the cell is not dividing. It consists of DNA wrapped around histone proteins. During cell division, chromatin condenses to form chromosomes.  Nucleolus: A dense region within the nucleus where ribosomal RNA (rRNA) is synthesized and ribosome assembly begins. Functions of the Nucleus:  Stores and protects the cell's genetic information.  Directs protein synthesis by transcribing DNA into messenger RNA (mRNA), which is then translated by ribosomes in the cytoplasm.  Controls cell growth, division, and differentiation. 2.3. Cellular Communication Cells communicate with each other via chemical signals, which bind to receptors on the cell membrane. This communication can take place over long or short distances.  Autocrine Signaling: The cell secretes a substance that acts on itself.  Paracrine Signaling: Signals act on nearby cells (e.g., neurotransmitters in the synaptic cleft).  Endocrine Signaling: Hormones are released into the bloodstream and act on distant cells or organs. Signal Transduction Pathways: When a chemical signal binds to a receptor on the cell membrane, it activates a cascade of intracellular reactions, leading to changes in cellular behavior. This often involves secondary messengers like cyclic AMP (cAMP). 2.4. Cellular Division and Growth Cells divide through processes of mitosis and meiosis:  Mitosis: The process by which a single cell divides into two identical daughter cells, ensuring tissue growth, repair, and maintenance.  Meiosis: A specialized form of cell division that occurs in germ cells (sperm and eggs), reducing the chromosome number by half to maintain genetic diversity during sexual reproduction. 9 Wadi Al-Shati University, College of Medical Technology, Department of Medical Laboratories. By Walaa Al-Azhari, M.Sc.  Introduction, cell, TBW and homeostasis 3.Total Body Water (TBW) Water is the most abundant component in the human body and plays a vital role in the functioning of cells and organs. Total Body Water (TBW) comprises the total volume of water present within the body’s compartments and significantly contributes to body weight. It is crucial for maintaining homeostasis, transporting nutrients, and removing waste products. On average, TBW accounts for approximately:  60% of body weight in adult males  52.5% in adult females  77% in infants These percentages can vary based on factors such as age, sex, body fat percentage, and overall health. Understanding TBW and its distribution is essential for assessing hydration status and has important clinical implications. 3.1. Distribution of Total Body Water TBW is distributed into two main compartments:  Intracellular Fluid (ICF): This is the water found inside cells, which constitutes about two-thirds (40%) of TBW.  Extracellular Fluid (ECF): The fluid outside cells, comprising about one- third (20%) of TBW. The ECF is further subdivided into: o Interstitial Fluid (ISF): The fluid that surrounds cells, facilitating the exchange of nutrients and waste. o Plasma (Intravascular Fluid): The fluid component of blood, responsible for transporting cells, nutrients, and metabolic by-products throughout the body. o Transcellular Fluid: A minor portion of ECF that includes cerebrospinal fluid, synovial fluid (in joints), peritoneal fluid, and pleural fluid. Table 1: Approximate distribution of TBW in a 70 kg male Compartment Percentage of Body Weight Volume (Liters) Intracellular Fluid 40% 28 L Extracellular Fluid 20% 14 L - Interstitial Fluid 15% 10.5 L - Plasma 5% 3.5 L 3.2. Functions of Total Body Water 11 Wadi Al-Shati University, College of Medical Technology, Department of Medical Laboratories. By Walaa Al-Azhari, M.Sc.  Introduction, cell, TBW and homeostasis Water in the body plays several vital roles, including: Medium for Cellular Reactions: Water serves as the solvent for biochemical reactions, essential for metabolic processes and energy production (ATP synthesis). Transport of Nutrients and Waste: It facilitates the movement of nutrients (e.g., glucose, amino acids) and the removal of waste (e.g., urea, CO₂) via blood plasma. Temperature Regulation: Water helps regulate body temperature by sweating and evaporating heat from the body. Lubrication and Cushioning: Water acts as a lubricant in joints (synovial fluid) and protects vital organs (e.g., cerebrospinal fluid for the brain). Electrolyte Balance: Water distribution helps maintain electrolyte concentration, crucial for functions like nerve signaling and muscle contraction. 3.4. Regulation of Total Body Water The body regulates Total Body Water (TBW) through various mechanisms involving hormones, the kidneys, and thirst: 1. Hormonal Regulation: o Antidiuretic Hormone (ADH): Produced by the hypothalamus and released from the posterior pituitary, ADH promotes water reabsorption in the kidneys, reducing urine output. Its levels increase during dehydration to concentrate urine and retain water. o Aldosterone: This hormone, produced by the adrenal glands, promotes sodium retention and potassium excretion in the kidneys. Since water follows sodium, aldosterone indirectly aids in water retention, helping to regulate blood volume and pressure. o Atrial Natriuretic Peptide (ANP): Released by the heart in response to increased blood volume or pressure, ANP promotes sodium and water excretion, thus reducing blood volume. 2. Thirst Mechanism: Osmoreceptors in the hypothalamus detect changes in blood osmolarity. An increase in osmolarity (e.g., dehydration) triggers thirst, prompting water intake to restore normal osmolarity and TBW levels. 3. Renal Function: The kidneys are crucial for maintaining water balance: o In overhydration, they produce more dilute urine to expel excess water. o In dehydration, they concentrate urine by reabsorbing more water, with the aid of ADH, to conserve body water. The glomerular filtration rate (GFR) and tubular reabsorption are essential for adjusting water levels based on the body's hydration status. This comprehensive regulation is vital for maintaining homeostasis and overall health. 3.5. Shifts in Fluid Compartments Fluid shifts between the intracellular fluid (ICF) and extracellular fluid (ECF) compartments can occur due to various conditions: 11 Wadi Al-Shati University, College of Medical Technology, Department of Medical Laboratories. By Walaa Al-Azhari, M.Sc.  Introduction, cell, TBW and homeostasis 1. Dehydration: This results from excessive water loss, reducing ECF volume, often due to diarrhea, vomiting, or inadequate fluid intake. It can lead to cellular dysfunction and symptoms like fatigue and dry skin. 2. Overhydration: Excessive water intake or kidney failure can cause overhydration, leading to diluted electrolytes (especially sodium), resulting in potential brain swelling, seizures, and in severe cases, coma or death. 3. Edema: This is the accumulation of excess fluid in the interstitial space, often due to imbalances in hydrostatic and osmotic pressures. Causes include heart failure, kidney disease, or inflammation. 4. Homeostasis Homeostasis refers to the body's ability to maintain a stable internal environment despite changes in external conditions. It is a vital concept in physiology, as it allows the body to function efficiently under various circumstances. Without homeostasis, physiological processes would become imbalanced, leading to diseases or even death. This interrelationship forms the foundation of physiology, ensuring that physiological processes remain balanced and efficient. Importance of Homeostasis: The cells of the body require a carefully controlled internal environment to operate effectively. This includes balanced levels of oxygen, carbon dioxide, nutrients, temperature, fluid levels, and blood pressure. The primary role of homeostatic mechanisms is to keep these variables within narrow limits to ensure optimal function. Systems Involved in Homeostasis: Several physiological systems are involved in maintaining homeostasis, including: 1. Nervous System: The central nervous system, especially the brain and spinal cord, plays a crucial role in regulating various homeostatic mechanisms. The brain sends nerve signals to organs to adjust their functions and maintain balance. 2. Endocrine System (Hormones): Hormones released by the endocrine glands are key regulators of body processes, such as blood sugar levels through insulin secretion by the pancreas. 3. Circulatory System: It distributes nutrients, hormones, and oxygen to tissues while removing waste products from the body. Key Mechanisms of Homeostasis: 1. Negative Feedback Mechanism: This is the most common mechanism for maintaining homeostasis. The body senses changes in internal conditions and responds by reversing those changes to restore balance. For instance, when body temperature rises above normal, the central nervous system signals the sweat glands to increase sweating, cooling the body. 2. Positive Feedback Mechanism: Although less common, this mechanism is essential in specific cases. A well-known example is blood clotting, where a wound triggers a cascade of chemical reactions that amplify each other until the bleeding stops. Examples of Homeostasis in the Body: 12 Wadi Al-Shati University, College of Medical Technology, Department of Medical Laboratories. By Walaa Al-Azhari, M.Sc.  Introduction, cell, TBW and homeostasis 1. Regulation of Body Temperature: The body maintains a relatively constant internal temperature (around 37°C) through complex mechanisms, including sweating, dilation, or constriction of surface blood vessels, and shivering to increase heat production. 2. Regulation of Blood Glucose Levels: Blood glucose levels must remain within a narrow range. After eating, blood glucose rises, prompting the pancreas to release insulin, which helps cells absorb glucose. When glucose levels drop, the pancreas secretes glucagon, which stimulates the liver to release stored glucose into the bloodstream. 3. Osmotic Pressure Regulation: Osmotic pressure is the measure of solute concentration in the blood. The kidneys play a key role in regulating fluid and ion concentrations by eliminating excess through urine or reabsorbing what the body needs. Disruptions in Homeostasis: When the body fails to maintain internal balance, a homeostatic disruption occurs, which can lead to various diseases. For example:  Diabetes: Results from a failure to regulate blood glucose levels.  Fever: Occurs when the body cannot maintain normal temperature due to infection.  Hypertension: Arises from improper regulation of blood pressure. 13 Wadi Al-Shati University, College of Medical Technology, Department of Medical Laboratories. By Walaa Al-Azhari, M.Sc.