Introduction to Human Anatomy and Physiology PDF

MODULE 1 INTRODUCTION TO HUMAN ANATOMY AND PHYSIOLOGY Learning Tasks and Performance Indicators: 1. Define anatomy and physiology; 2. Discuss sub-fields of anatomy and physiology; 3. Distinguish the different le...

MODULE 1 INTRODUCTION TO HUMAN ANATOMY AND PHYSIOLOGY Learning Tasks and Performance Indicators: 1. Define anatomy and physiology; 2. Discuss sub-fields of anatomy and physiology; 3. Distinguish the different levels of structural organization; 4. Enumerate characteristics of an organism; 5. Explain homeostasis and its significance; and 6. Describe the basic anatomical terminologies. Course Outline: 1. Anatomy and Physiology: Defined 2. Levels of Structural Organization 3. Characteristics of an Organism 4. Homeostasis 5. Basic Anatomical Terminology Two branches of science—anatomy and physiology—provide the foundation for understanding the body’s parts and functions. Anatomy is the science of body structures and the relationships among them. It was first studied by dissection, the careful cutting apart of body structures to study their relationships. Physiology is the science of body functions—how the body parts work. Since the structures and functions are so closely related, you will learn about the human body by studying its anatomy and physiology together. The structure of a part of the body allows performance of certain functions. For example, the bones of the skull join tightly to form a rigid case that protects the brain. The bones of the fingers are more loosely joined to allow a variety of movements. The walls of the air sacs in the lungs are very thin, permitting rapid movement of inhaled oxygen into the blood. The lining of the urinary bladder is much thicker to prevent the escape of urine into the pelvic cavity, yet its construction allows for considerable stretching as the urinary bladder fills with urine. A. SUBFIELDS OF ANATOMY 1. Gross Anatomy – structures that can be examined without using a microscope. 2. Cytology – structures and functions of a cell. 3. Histology – microscopic structure of tissues. 4. Embryology – study of structures that emerged from the time of fertilized egg through the 8 weeks in uterus. 5. Developmental Biology – the complete development of an individual from fertilization of an egg to death. 6. Surface Anatomy – surface markings of the body to understand internal anatomy through visualization and palpation (gentle touch).  7. Systemic Anatomy – structure of specific systems of the body such as the nervous or respiratory systems. 8. Regional Anatomy – specific regions of the body such as the head or chest. 9. Radiographic Anatomy – body structures that can be visualized with x-rays. 10. Pathological Anatomy – structural changes (from gross to microscopic) associated with disease. B. SUBFIELDS OF PHYSIOLOGY 1. Neurophysiology – functional properties of nerve cells. 2. Endocrinology – hormones (chemical regulators in the blood and how they control body functions. 3. Cardiovascular Physiology – functions of the heart and blood vessels. 4. Immunology – how the body defends itself against disease-causing agents. 5. Respiratory Physiology – functions of the air passageways and lungs. 6. Renal Physiology – functions of the kidneys. 7. Exercise Physiology – changes in cell and organ functions as a result of muscular activity. 8. Pathophysiology – functional changes associated with disease and aging. The levels of organization of a language—letters, words, sentences, paragraphs, and so on— can be compared to the levels of organization of the human body. Your exploration of the human body will extend from atoms and molecules to the whole person. From the smallest to the largest, six levels of organization will help you to understand anatomy and physiology: the chemical, cellular, tissue, organ, system, and organismal levels of organization. 1. Chemical level  Atoms, the smallest units of matter that participate in chemical reactions.  Molecules, two or more atoms joined together. Certain atoms, such as carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), calcium (Ca), and sulfur (S), are essential for maintaining life.  Deoxyribonucleic acid (DNA), the genetic material passed from one generation to the next, and glucose, commonly known as blood sugar. 2. Cellular level  Cells, the basic structural and functional units of an organism. Cells are the smallest living units in the human body.  Examples: muscle cells, nerve cells, and epithelial cells. The figure shows a smooth muscle cell, one of the three types of muscle cells in the body.  3. Tissue level  Tissues are groups of cells and the materials surrounding them that work together to perform a particular function  Types of tissue in the body: epithelial tissue, connective tissue, muscular tissue, and nervous tissue. 4. Organ level.  Organs are structures that are composed of two or more different types of tissues; they have specific functions and usually have recognizable shapes.  Examples of organs are the stomach, skin, bones, heart, liver, lungs, and brain. 5. System level  A system consists of related organs with a common function.  Also called the organ-system level.  Example: digestive system, which breaks down and absorbs food. Its organs include the mouth, salivary glands, pharynx (throat), esophagus, stomach, small intestine, large intestine, liver, gallbladder, and pancreas. Sometimes an organ is part of more than one system. The pancreas, for example, is part of both the digestive system and the hormone- producing endocrine system. 6. Organismal level.  Organism, any living individual, can be compared to a book in our analogy. All the parts of the human body functioning together constitute the total organism. Certain processes distinguish organisms, or living things, from nonliving things. Following are the six most important life processes of the human body: 1. Differentiation  The development of a cell from an unspecialized to a specialized state.  For example, a fertilized egg (ovum) develops into an embryo, and then into a fetus, an infant, a child, and finally an adult. 2. Reproduction  The formation of new cells for tissue growth, repair, or replacement, or to the production of a new individual.  In humans, the former process occurs continuously throughout life, which continues from one generation to the next through the latter process, the fertilization of an ovum by a sperm cell. 3. Growth  The increase in body size that results from an increase in the size of existing cells, an increase in the number of cells, or both.  4. Movement  The motion of the whole body, individual organs, single cells, and even tiny structures inside cells.  For example, the coordinated action of leg muscles moves your whole body from one place to another when you walk or run. 5. Responsiveness  The body’s ability to detect and respond to changes (reaction).  For example, different cells in the body respond to environmental changes in characteristic ways. Nerve cells respond by generating electrical signals known as nerve impulses (action potentials). Muscle cells respond by contracting, which generates force to move body parts. 6. Metabolism  The sum of all the chemical processes that occur in the body.  Catabolism, the breakdown of complex chemical substances into simpler components.  Anabolism, the building up of complex chemical substances from smaller, simpler components.  For example, digestive processes catabolize (split) proteins in food into amino acids. These amino acids are then used to anabolize (build) new proteins that make up body structures such as muscles and bones. When the life processes cease to occur properly, the result is death of cells and tissues, which may lead to death of the organism. Clinically, loss of the heartbeat, absence of spontaneous breathing, and loss of brain functions indicate death in the human body. Homeostasis is the condition of equilibrium (balance) in the body’s internal environment due to the constant interaction of the body’s many regulatory processes. An important aspect of homeostasis is maintaining the volume and composition of body fluids, dilute, watery solutions containing dissolved chemicals that are found inside cells as well as surrounding them. BODY FLUIDS 1. Intracellular Fluid (ICF). The fluid within cells. 2. Extracellular Fluid EFC). The fluid outside body cells is  Interstitial Fluid. Fills the narrow spaces between cells of tissues.  Blood Plasma. Fluid within blood vessels  Lymph. Fluid within lymphatic vessels  Cerebrospinal Fluid. In and around the brain and spinal cord  Synovial Fluid. In joints  Aqueous Humor and Vitreous Body. The fluid of the eyes The proper functioning of body cells depends on precise regulation of the composition of the interstitial fluid surrounding them. Because of this, interstitial fluid is often called the body’s internal environment. The composition of interstitial fluid changes as substances move back and forth between it and blood plasma. Such exchange of materials occurs across the thin walls of the smallest blood vessels in the body, the blood capillaries. This movement in both directions across capillary walls provides needed materials, such as glucose, oxygen, ions, and so on, to tissue cells. It also removes wastes, such as carbon dioxide, from interstitial fluid. Homeostasis in the human body is continually being disturbed. Some disruptions come from the external environment in the form of physical insults such as the intense heat or a lack of enough oxygen for that two-mile run. Other disruptions originate in the internal environment, such as a blood glucose level that falls too low when you skip breakfast. Homeostatic imbalances may also occur due to psychological stresses in our social environment—the demands of work and school, for example. In most cases the disruption of homeostasis is mild and temporary, and the responses of body cells quickly restore balance in the internal environment. However, in some cases the disruption of homeostasis may be intense and prolonged, as in poisoning, overexposure to temperature extremes, severe infection, or major surgery. Fortunately, the body has many regulating systems that can usually bring the internal environment back into balance. Most often, the nervous system and the endocrine system, working together or independently, provide the needed corrective measures. The nervous system regulates homeostasis by sending electrical signals known as nerve impulses (action potentials) to organs that can counteract changes from the balanced state. The endocrine system includes many glands that secrete messenger molecules called hormones into the blood. Nerve impulses typically cause rapid changes, but hormones usually work more slowly. Both means of regulation, however, work toward the same end, usually through negative feedback systems. FEEDBACK SYSTEMS The body can regulate its internal environment through many feedback systems. A feedback system or feedback loop is a cycle of events in which the status of a body condition is monitored, evaluated, changed, remonitored, reevaluated, and so on. Each monitored variable, such as body temperature, blood pressure, or blood glucose level, is termed a controlled condition. Any disruption that changes a controlled condition is called a stimulus. A feedback system includes three basic components—a receptor, a control center, and an effector. 1. Receptor. A body structure that monitors changes in a controlled condition and sends input to a control center. Typically, the input is in the form of nerve impulses or chemical signals. For example, certain nerve endings in the skin sense temperature and can detect changes, such as a dramatic drop in temperature. 2. Control center. The brain, sets the range of values within which a controlled condition should be maintained, evaluates the input it receives from receptors, and generates output commands when they are needed. Output from the control center typically occurs as nerve impulses, or hormones or other chemical signals. In our skin temperature example, the brain acts as the control center, receiving nerve impulses from the skin receptors and generating nerve impulses as output.  3. Effector is a body structure that receives output from the control center and produces a response or effect that changes the controlled condition. Nearly every organ or tissue in the body can behave as an effector. When your body temperature drops sharply, your brain (control center) sends nerve impulses (output) to your skeletal muscles (effectors). The result is shivering, which generates heat and raises your body temperature. A group of receptors and effectors communicating with their control center forms a feedback system that can regulate a controlled condition in the body’s internal environment. In a feedback system, the response of the system “feeds back” information to change the controlled condition in some way, either negating it (negative feedback) or enhancing it (positive feedback). A. NEGATIVE FEEDBACK SYSTEMS A negative feedback system reverses a change in a controlled condition. Consider the regulation of blood pressure. Blood pressure (BP) is the force exerted by blood as it presses against the walls of blood vessels. When the heart beats faster or harder, BP increases. If some internal or external stimulus causes blood pressure (controlled condition) to rise, the following sequence of events occurs. Baroreceptors (the receptors), pressure-sensitive nerve cells located in the walls of certain blood vessels, detect the higher pressure. The baroreceptors send nerve impulses (input) to the brain (control center), which interprets the impulses and responds by sending nerve impulses (output) to the heart and blood vessels (the effectors). Heart rate decreases and blood vessels dilate (widen), which cause BP to decrease (response). This sequence of events quickly returns the controlled condition— blood pressure—to normal, and homeostasis is restored. Notice that the activity of the effector causes BP to drop, a result that negates the original stimulus (an increase in BP). This is why it is called a negative feedback system. B. POSITIVE FEEDBACK SYSTEMS A positive feedback system tends to strengthen or reinforce a change in one of the body’s controlled conditions. A positive feedback system operates similarly to a negative feedback system, except for the way the response affects the controlled condition. The control center still provides commands to an effector, but this time the effector produces a physiological response that adds to or reinforces the initial change in the controlled condition. The action of a positive feedback system continues until it is interrupted by some mechanism. Normal childbirth provides a good example of a positive feedback system. The first contractions of labor (stimulus) push part of the fetus into the cervix, the lowest part of the uterus, which opens into the vagina. Stretch- sensitive nerve cells (receptors) monitor the amount of stretching of the cervix (controlled condition). As stretching increases, they send more nerve impulses (input) to the brain (control center), which in turn releases the hormone oxytocin (output) into the blood. Oxytocin causes muscles in the wall of the uterus (effector) to contract even more forcefully. The contractions push the fetus farther down the uterus, which stretches the cervix even more. The cycle of stretching, hormone release, and ever-stronger contractions is interrupted only by the birth of the baby. Then, stretching of the cervix ceases and oxytocin is no longer released. Another example of positive feedback is what happens to your body when you lose a great deal of blood. Under normal conditions, the heart pumps blood under sufficient pressure to body cells to provide them with oxygen and nutrients to maintain homeostasis. Upon severe blood loss, blood pressure drops and blood cells (including heart cells) receive less oxygen and function less efficiently. If the blood loss continues, heart cells become weaker, the pumping action of the heart decreases further, and blood pressure continues to fall. This is an example of a positive feedback cycle that has serious consequences and may even lead to death if there is no medical intervention. These examples suggest some important differences between positive and negative feedback systems. Because a positive feedback system continually reinforces a change in a controlled condition, some event outside the system must shut it off. If the action of a positive feedback system is not stopped, it can “runaway” and may even produce life-threatening conditions in the body. The action of a negative feedback system, by contrast, slows and then stops as the controlled condition returns to its normal state. Usually, positive feedback systems reinforce conditions that do not happen very often, and negative feedback systems regulate conditions in the body that remain fairly stable over long periods. HOMEOSTATIC IMBALANCES As long as all the body’s controlled conditions remain within certain narrow limits, body cells function efficiently, negative feedback systems maintain homeostasis, and the body stays healthy. Should one or more components of the body lose their ability to contribute to homeostasis, however, the normal equilibrium among body processes may be disturbed. If the homeostatic imbalance is moderate, a disorder or disease may occur; if it is severe, death may result.  Disorder is any abnormality of structure or function.  Disease is a more specific term for an illness characterized by a recognizable set of signs and symptoms. A local disease affects one part or a limited region of the body; a systemic disease affects either the entire body or several parts of it. Diseases alter body structures and functions in characteristic ways. o Symptoms, subjective changes in body functions that are not apparent to an observer. Examples of symptoms are headache, nausea, and anxiety. o Signs, objective changes that a clinician can observe and measure. Signs of disease can be either anatomical, such as swelling or a rash, or physiological, such as fever, high blood pressure, or paralysis. Scientists and health-care professionals use a common language of special terms when referring to body structures and their functions. The language of anatomy they use has precisely defined meanings that allow us to communicate clearly and precisely. For example, is it correct to say, “The wrist is above the fingers”? This might be true if your upper limbs (described shortly) are at your sides. But if you hold your hands up above your head, your fingers would be above your wrists. To prevent this kind of confusion, anatomists use a standard anatomical position and a special vocabulary for relating body parts to one another. A. BODY POSITIONS 1. Anatomical Position  Body is upright or standing position  Facing forward with arms on the sides and the palms facing outward 2. Reclining Position  Body is lying on a plane i. Prone – lying face down ii. Supine – lying face up B. REGIONAL NAMES 1. Head or Cephalic  Includes the skull and the face 2. Neck or Cervical  Attaches the head to the trunk 3. Trunk  Includes the chest, abdomen, and pelvis 4. Limbs or Appendages  Upper Appendages – shoulder, armpit, arm, forearm, wrist, and hand  Lower Appendages – buttock, thigh, leg, ankle, and foot *** Groin – the area on the front surface of the body marked by a crease on each side, where the trunk attaches to the thighs. The common names and corresponding anatomical terms (in parentheses) are indicated for specific body regions. For example, the head is the cephalic region. The descriptive form of a body part usually is based on a Greek or Latin word. For example, the Latin word for armpit is axilla. Thus, one of the nerves passing within the armpit is named the axillary nerve. C. DIRECTIONAL TERMS To locate various body structures, anatomists use specific directional terms, words that describe the position of one body part relative to another. Several directional terms are grouped in pairs that have opposite meanings, such as anterior (front) and posterior (back). 1. Anterior (ventral) – Nearer to or at the front of the body. 2. Posterior (dorsal) – Nearer to or at the back of the body. 3. Superior (cephalic or cranial) – Toward the head, or the upper part of a structure. 4. Inferior (caudal) – Away from the head, or the lower part of a structure. 5. Lateral – Farther from the midline. a. Ipsilateral – On the same side of the body as another structure. b. Contralateral – On the opposite side of the body from another structure. 6. Medial – Nearer to the midline. 7. Superficial (external) – Toward or on the surface of the body. 8. Deep (Internal) – Away from the surface of the body. 9. Proximal – Nearer to the attachment of a limb to the trunk; nearer to the origination of a structure. 10. Distal – Farther from the attachment of a limb to the trunk; farther from the origination of a structure. 11. Intermediate – Between two structures. 12. Central – describe major structures of the body 13. Peripheral – describe minor structures of the body 14. Visceral – organs inside a cavity 15. Parietal – walls of a cavity D. FUNDAMENTAL PLANES AND SECTIONS OF THE BODY When you study a body region, you often view it in section. A section is a cut of the body or one of its organs made along one of the planes just described. It is important to know the plane of the section so you can understand the anatomical relationship of one part to another. The figure indicates how three different sections—transverse, frontal, and midsagittal—provide different views of the brain. 1. Sagittal Planes – vertical line that divides the body into left and right parts.  Midsagittal plane – line passing through the middle dividing the structures into two equal parts.  Parasagittal plane – line passing through the middle dividing the structures into two unequal parts. 2. Coronal or Frontal – divides the structure into anterior and posterior parts. 3. Transverse or Cross-sectional or Horizontal – divides the body into superior and inferior parts. 4. Oblique Plane – passes through the body or an organ at an angle between a transverse plane and a sagittal plane or between a transverse plane and a frontal plane. E. BODY CAVITIES Body cavities are spaces within the body that help protect, separate, and support internal organs. Bones, muscles, ligaments, and other structures separate the various body cavities from one another. 1. Dorsal Body Cavity  Cranial – brain  Vertebral – spinal cord 2. Ventral Body Cavity  Thoracic Cavity – superior portion i. Pericardial cavity – heart ii. Pleural cavity – lungs *** Mediastinum – central portion of the thoracic cavity containing all thoracic viscera except the lungs. It includes the heart, trachea, thymus, esophagus, and large blood vessels.  Abdominopelvic Cavity – inferior portion i. Abdominal cavity  Stomach, spleen, liver, pancreas, gallbladder, kidneys, uterus, adrenal glands, large portion of the large and small intestine. ii. Pelvic Cavity  Urinary bladder, portion of large and small intestine, reproductive organs. 3. Other Body Cavities  Oral cavity – contains the tongue and teeth  Nasal cavity – the nose