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Module 1: An Introduction to the Human BodyCurriculum OutlineResourcesTortora, Principals of Anatomy and PhysiologyChapter 1. An Introduction to the Human BodyAllen, Laboratory Manual for Anatomy and PhysiologyExercise 1. Anatomical LanguageExercise 2. Organ Systems and Body CavitiesAnatomy and Physiology DefinedAnatomy – the study of the body structures and their relationships to each other.First studied by dissection – the cutting apart of body structures to study their relationships. Today, medical imaging techniques are also used.Branches of anatomical study include:Embryology – the study of the first eight weeks of development after fertilization of a human egg. Histology – the study of microscopic structure of tissues.Gross anatomy – the study of structures that can be examined without a microscope.Pathological anatomy – the study of structural changes (gross to microscopic) associated with disease.Physiology – the study of how body structures function.Studied using the scientific method – a systematic and logical approach to discovering how things work.The scientific method’s procedure is:Make an observation. Ask questions about the observation and gather information.Form a hypothesis — a tentative description of what’s been observed, and make predictions based on that hypothesis.Test the hypothesis and predictions in an experiment that can be reproduced. An experiment should include an experimental group and a control group. The control group is what the experimental group is compared against.Analyze the data and draw conclusions; accept or reject the hypothesis or modify the hypothesis if necessary.Reproduce the experiment until there are no discrepancies between observations and theory.Branches of physiology include:Neurophysiology – the study of the functional properties of nerve cells.Endocrinology – the study of hormones and how they control body functions.Pathophysiology – the study of functional changes associated with disease and aging.Structure and function are closely related – the structure of a body part often reflects its function. Furthermore, structural change results in functional change. This relationship is fundamental to healthcare - structural damage to a body part results in dysfunction, which may lead to disorder, disease, and potentially death.Levels of Structural OrganizationThe human body consists of several levels of structural organization (Figure 1.1):Chemical level - includes atoms and molecules.Atoms - the smallest units of matter that participate in chemical reactions.Molecules - two or more atoms joined together by a chemical reaction.Cellular level – molecules combine to form cells.Cells - the basic structural and functional living units of an organism.Tissue level – cells combine to form tissues.Tissues are groups of cells and the materials surrounding them that work together to perform a particular an level – two or more different types of tissues combine to form discrete organs with specific functions.System level - consists of related organs with a common function. An organ can belong to more than one anismal level – consists of all of the organ systems functioning together to constitute the total organism.The eleven systems of the human body are the integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic and immune, respiratory, digestive, urinary, and reproductive. See Table 1.2 in the textbook for a brief overview of each system’s components and functions.Knowledge of the body’s structural hierarchy is essential in health care – injury and dysfunction at one level may lead to injury and dysfunction at higher levels. The consequence may be disorder, disease, and potential death of the organism.Basic Life ProcessesAll living things have certain characteristics that distinguish them from nonliving things. The basic life processes in humans are:Metabolism - the sum of all chemical processes that occur in the body.Catabolism – the breakdown of large complex chemicals into small simpler components.Anabolism – the assembly of large complex chemicals from smaller, simpler components.Responsiveness - the ability to detect and respond to changes in environment (externally and internally).Movement - includes motion of the whole body, individual organs, single cells, or even organelles inside cells.Growth - refers to an increase in size and complexity, due to an increase in the number of cells (hyperplasia), size of cells (hypertrophy), or both.Differentiation - the change in a cell from an unspecialized state to a specialized state.Reproduction - refers either to the formation of new cells for growth, repair, or replacement (mitosis), or the production of a new individual (meiosis, sexual reproduction).If a life process becomes disrupted, the result may be cell and tissue death, which may lead to death of the organism.HomeostasisHomeostasis – the condition of dynamic equilibrium (balance) in the body’s internal environment due to the constant the constant interactions of the body’s many regulatory processes. Each structure, from the chemical level to the system level, contributes in some way to keeping body conditions within normal limits.Homeostasis and Body FluidsBody fluid homeostasis is essential to an organism’s survival; fluid volume and composition must be precisely maintained at all times. There are two types of body fluid:Intracellular fluid (ICF) - found inside body cells; also called cytosol.Extracellular fluid (ECF) - found outside body cells. Some examples are: Interstitial fluid – found between body cells. Blood plasma – found within blood vessels.Lymph – found within lymphatic vessels.Cerebrospinal fluid (CSF) – found around and within the brain and spinal cord.Interstitial fluid is often called the body’s internal environment. The composition of interstitial fluid changes as substances move back and forth between it, cells, and blood plasma.Exchange between intracellular fluid and interstitial fluid occurs across a cell’s plasma membrane.Exchange between interstitial fluid and blood plasma occurs across a blood capillary.Control of HomeostasisHomeostatic imbalances occur because of disruptions from the external or internal environments. When the disruption is mild or temporary, the body can quickly respond and restore balance in the internal environment. If disruption is extreme, homeostatic regulation may fail.Homeostasis is regulated by the nervous system and endocrine system, acting together or independently, using feedback systems.The nervous system detects changes and sends nerve impulses to counteract the disruption.The endocrine system regulates homeostasis by secreting hormones.Whereas nerve impulses cause rapid changes, hormones usually work more slowly.Feedback SystemsGeneral PrinciplesA feedback system is a cycle of events in which information about the status of a condition is continually monitored and fed back (reported) to a central control region (Figure 1.2).Any disruption that changes a controlled condition is called a stimulus.A feedback system consists of three basic components.A receptor monitors changes in a controlled condition and sends input in the form of nerve impulses or chemical signals to a control center.The control center sets the range of values within which a controlled condition should be maintained, evaluates the input it receives from the receptors, and generates output commands when they are needed.An effector is a body structure that receives output from the control center and produces a response or effect that changes the controlled condition.If a response reverses the original stimulus, the system is a negative feedback system.If a response enhances the original stimulus, the system is a positive feedback system.Negative Feedback SystemsA negative feedback system reverses a change in a controlled condition.Homeostasis of Blood Pressure (BP): Negative Feedback (Figure 1.3)If a stimulus (stress) causes blood pressure (controlled condition) to rise, pressure-sensitive cells (baroreceptors) in certain arteries send impulses (input) to the brain (control center). The brain sends impulses (output) to the heart (effector), causing the heart rate to decrease (response) and return of blood pressure to normal (restoration of homeostasis).The activity of the effector produces a result, a drop in blood pressure that opposes the stimulus, an increase in blood pressure.Positive Feedback SystemA positive feedback system tends to strengthen or reinforce a change in one of the body’s controlled conditions.Normal childbirth provides a good example of a positive feedback system (Figure 1.4).When labor begins, the uterus is stretched (stimulus) and stretch-sensitive nerve cells in the cervix of the uterus (receptors) send impulses (input) to the hypothalamus (control center). The hypothalamus causes the release of oxytocin (output) which stimulates the uterus (effector) to contract more forcefully (response). Movement of the baby’s head down the birth canal causes further stretching, the release of more oxytocin, and even more forceful contractions.The cycle is broken with the birth of the baby.Homeostatic ImbalancesDisruption of homeostasis can lead to disorder, disease and death.Disorder - a general term for any derangement of abnormality of function.Disease - a more specific term for an illness characterized by a recognizable set of signs and symptoms.Signs - objective changes that a clinician can observe and measure; e.g., fever or rash.Symptoms - subjective changes in body functions that are not apparent to an observer; e.g., headache or nausea.BASIC ANATOMICAL TERMINOLOGYBody PositionsAnatomical PositionThe anatomical position is a standardized method of observing or imaging the body that allows precise and consistent anatomical references.When in the anatomical position, the subject stands erect facing the observer, the upper extremities are placed at the sides, the palms of the hands are turned forward, and the feet are flat on the floor.Reclining PositionIf the body is lying face down, it is in the prone position.If the body is lying face up, it is in the supine position.Regional NamesRegional names are names given to specific regions of the body for reference.Examples of regional names include cranial (skull), thoracic (chest), brachial (arm), patellar (knee), cephalic (head), and gluteal (buttock) as seen in Figure 1.5. Directional TermsDirectional terms are used to precisely locate one part of the body relative to another and to reduce length of monly used directional terms, such as dorsal, superior, medial, and distal, are summarized in Exhibit 1.A and Figure 1.6.Planes and SectionsPlanes are imaginary flat surfaces that are used to divide the body or organs into definite areas (Figure 1.7). Principal planes include: sagittal, frontal (coronal), and transverse (cross-sectional).Sections are flat surfaces resulting from cuts through body structures. They are named according to the plane on which the cut is made and include sagittal, frontal, and transverse (Figure 1.8).Body CavitiesBody cavities are spaces within the body that help protect, separate, and support internal organs.Cranial Cavity and vertebral canalThe cranial cavity is formed by the cranial bones and contains the brain.The vertebral (spinal) canal is formed by the bones of the vertebral column and contains the spinal cord.Three layers of protective tissue, called meninges, line these cavities.Body Cavities of the trunkThe trunk is subdivided by the diaphragm into an upper thoracic cavity and a lower abdominopelvic cavity. (Figure 1.9)The thoracic cavity contains two pleural cavities, and the mediastinum, which includes the pericardial cavity (Figure 1.10).The pleural cavities enclose the lungs, while the pericardial cavity surrounds the heart (Figure 1.10).The mediastinum is a broad, median partition between the lungs that extends from the sternum to the vertebral column; it contains all contents of the thoracic cavity except the lungs.The abdominopelvic cavity is divided into a superior abdominal and an inferior pelvic cavity (Figure 1.11).Viscera of the abdominal cavity include the stomach, spleen, pancreas, liver, gallbladder, small intestine, and most of the large intestine (Figure 1.11).Viscera of the pelvic cavity include the urinary bladder, portions of the large intestine and internal female and male reproductive structures (Figure 1.11).Thoracic and Abdominal Cavity MembranesA thin, slippery serous membrane covers the viscera within the thoracic and abdominal cavities and also lines the walls of the thorax and abdomen.Parts of the serous membrane are the parietal layer which lines the walls of the cavities and the visceral layer which covers and adheres to the viscera within the cavities.Serous fluid between the two layers reduces friction and allows the viscera to slide somewhat during movements.The serous membranes include the pleura, pericardium and peritoneum.The pleural membrane surrounds the lungs, with the visceral pleura clinging to the surface of the lungs and the parietal pleura lining the chest wall.The serous membrane of the pericardial cavity is the pericardium, with visceral pericardium covering the surface of the heart and the parietal pericardium lining the chest wall.The peritoneum is the serous membrane of the abdominal cavity, with the visceral peritoneum covering the abdominal viscera and the parietal peritoneum lining the abdominal wall.Abdominopelvic Regions and QuadrantsTo describe the location of organs easily, the abdominopelvic cavity may be divided into nine regions by drawing four imaginary lines as shown in Figure 1.12.To locate the site of an abdominopelvic abnormality in clinical studies, the abdominopelvic cavity may be divided into quadrants by passing imaginary horizontal and vertical lines through the umbilicus (Figure 1.12).MEDICAL IMAGINGMedical imaging techniques allow physicians to peer inside the body to provide clues to abnormal anatomy and deviations from normal physiology in order to help diagnose disease Some common imaging techniques are:Radiography – uses x-rays to visualize bone and soft tissue (e.g. bone fracture diagnosis, mammography, and angiography); often the first imaging technique used to make a diagnosis.Magnetic resonance imaging (MRI) – uses magnetic fields and radio waves to create a computerized image; shows fine details for soft tissue but not bones. Most useful for differentiating between normal and abnormal tissues (e.g. brain tumors, blocked arteries, and musculoskeletal disorders).Computed tomography (CT) – uses multiple x-rays and a computer to create transverse section images of the body. Visualizes soft tissue and organs with much more detail than radiography. Often used to screen for cancer and coronary artery disease.Ultrasound scanning (Sonography) – uses sound waves and a detection instrument to visualize the body on a video monitor. The technique is safe, noninvasive, and painless. Most commonly used to visualize the fetus during pregnancy. Also used to observe organs and blood flow.Positron emission tomography (PET) – a positron-emitting substance is injected into the body and a detector measures the breakdown of the substance over time. Metabolically active tissues break the substance down faster than other tissues. Used to study body physiology (e.g. brain or heart metabolism).Endoscopy – Uses a video camera to visually inspect hollow body organs or cavities (e.g. colonoscopy, laparoscopy, and arthroscopy).Radionuclide scanning – similar to PET but uses a radioactive substance instead of a positron-emitting substance. Used to study activity of a tissue or organ (e.g. searching for malignant tumors).In Class Activities Be prepared to present all observations.Anatomy Activity Make a group and pick one member to be the “specimen”Use your anatomy definition to examine a structure on your specimen and how it fits with other structures, NOT function!______________________________________________________________________________________________________________________________________________________________________________Physiology Activity Pick one member to be the “subject”Follow the scientific method to answer the following question: What is the effect of exercise on heart rate?Hypothesis: _______________________________________________Experiment: _______________________________________________________________________________________________________Results:Resting heart rate: __________ beats / minuteHR immediately after exercise: __________ beats / minuteConclusion (based on results): ________________________________________________________________________________________________________________________________________________Structure and Function activity Describe the structure of a spoon and fork. How are they the same? Different?______________________________________________________________________________________________________________Which one is better for liquid food like soup? Why?_______________________________________________________Which one is better for solid food like steak? Why?_______________________________________________________How can understanding the relationship between structure and function help us learn anatomy and physiology? _______________________________________________________ ................
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