Orientation to the Human Body PDF

4373_01_001-015.qxp 12/3/14 8:07 AM Page 3 1 chapter ORIENTATION TO THE HUMAN BODY...

4373_01_001-015.qxp 12/3/14 8:07 AM Page 3 1 chapter ORIENTATION TO THE HUMAN BODY More than 6 billion human bodies currently reside on the earth. While each is individually unique, all have the same basic design and structure. The structure of the body, anatomy, is closely entwined with how it functions, physiology. Once you learn the structure of a specific part of the body, you’ll naturally want to know how it works. Learning normal anatomy and physiology will also help you grasp the changes and symptoms that occur with certain disease processes. The study of the processes that disturb normal function is called pathophysiology. (Patho means suffering or disease; therefore, pathophys iology refers to diseased functioning.) As an example, in a later chapter, you’ll learn that the lungs consist of a series of tubes, called bronchi, and that the smallest of these bronchi end in tiny sacs, called alveoli. That’s a very basic description of the structure, or anatomy, of the lung. From there, you’ll learn that oxygen is absorbed into the bloodstream through the alveoli. That’s how the lung functions: its physiology. Armed with that information, you can then comprehend why someone becomes short of breath if the bronchi become narrowed (such as during an acute asthmatic attack) or blocked (such as from a tumor). The human body is an amazing organism. It is intricate and complex, but all of its processes make sense. Embark on this journey to study anatomy and physiology as you would any great adventure: with interest, excitement, and determination. Remember: you’re learning about yours elf ! The Body AT WORK We’re all aware that people look different on the outside. But did you know that people can vary internally as well? The art in this book reflects the anatomy typical of most people. However, variations do occur. For example, some people FAST FACT are born with only one kidney; others have an extra bone in their feet; still others have carotid arteries that follow an atypical route. Perhaps the most extreme Although Aristotle of example of anatomical variation is called situs inversus. In this inherited Greece made the first condition—affecting about 1 in 10,000 people—the organs are reversed. Instead recorded attempts to study of the spleen, pancreas, sigmoid colon, and most of the heart being on the left, anatomy in 380 B.C., the they’re on the right. Likewise, the gallbladder, appendix, and most of the liver are first atlas of anatomy wasn’t on the left instead of on the right. published until 1543 A.D. 4373_01_001-015.qxp 11/3/14 9:56 AM Page 4 4 Organization of the Body PART I Organization of the Body The human body is organized in a hierarchy, ranging from the very simple (a microscopic atom) to the very complex (a human being). Specifically: ATOMS link together to form… MOLECULES. Molecules are organized ORGANELLES, the metabolic units within into various structures, including… a cell that perform a specific function necessary to the life of the cell. Examples include mitochondria—the powerhouses that furnish the cell’s energy—and the cell’s nucleus. Organelles are contained within… ORGANS, which are structures of two or TISSUES, which are specialized groups of more tissue types working together to cells with similar structure and function. carry out a particular function. Examples CELLS, the smallest living units that Tissues come together to form… include the heart, stomach, and kidney. make up the body’s structure. Cells group Organs then form… together to form… ORGAN SYSTEMS, which are groups of organs that all contribute to a particular function. All of the organ systems together form… The Body AT WORK The body contains four types of tissues: Epithelial tissue covers or lines body surfaces; examples include the outer A HUMAN ORGANISM: one complete individual. layer of the skin, the walls of capillaries, and kidney tubules. Connective tissue connects and supports parts of the body; some transport and store materials; examples include bone, cartilage, and adipose tissues. Muscle contracts to produce movement; examples include skeletal muscles and the heart. Nerve tissue generates and transmits impulses to regulate body function; examples include the brain and nerves. 4373_01_001-015.qxp 11/3/14 9:56 AM Page 5 5 Organ Systems CHAPTER 1 Orientation to the Human Body The human body consists of 11 organ systems. The organs of each system contribute to a particular function. However, some organs belong to more than one system. Specifically, the pharynx is part of both the respiratory and the digestive systems, and the male urethra belongs to both the reproductive and urinary systems. Consists of skin, Consists of bones, Consists primarily hair, and nails cartilage, and of skeletal muscles Key functions: ligaments Key functions: Protection Key functions: Movement Temperature Protection of Posture regulation body organs Heat production Water retention Support Sensation Movement Blood formation Integumentary system Skeletal system Muscular system Consists of lymph Consists of the Consists of the nodes, lymphatic nose, pharynx, kidneys, ureters, vessels, lymph, larynx, trachea, urinary bladder, thymus, spleen, bronchi, and lungs and urethra and tonsils Key functions: Key functions: Key functions: Absorption of Excretion of Role in fluid oxygen wastes balance Discharge of Regulation of Production of carbon dioxide blood volume immune cells Acid-base and pressure Defense against balance Control of fluid, disease Speech electrolyte, and acid-base balance Lymphatic system Respiratory system Urinary system 4373_01_001-015.qxp 11/3/14 9:56 AM Page 6 6 PART I Organization of the Body Consists of the Consists of the Consists of the brain, spinal cord, pituitary gland, heart, arteries, nerves, and sense adrenals, pancreas, veins, and organs thyroid, capillaries Key functions: parathyroids, and Key functions: Control, other organs Distribution of regulation, and Key functions: oxygen, nutrients, coordination of Hormone wastes, other systems production hormones, Sensation Control and electrolytes, Memory regulation of immune cells, and other systems antibodies Fluid, electrolyte, and acid-base balance Nervous system Endocrine system Circulatory system Consists of the Consists of the Consists of the stomach, small and testes, vas deferens, ovaries, fallopian large intestines, prostate, seminal tubes, uterus, esophagus, liver, vesicles, and penis vagina, and breasts mouth, and Key functions: Key functions: pancreas Production and Production of Key functions: delivery of sperm eggs Breakdown and Secretion of sex Site of fertilization absorption of hormones and fetal nutrients development Elimination of Birth wastes Lactation Secretion of sex hormones Digestive system Male reproductive system Female reproductive system 4373_01_001-015.qxp 11/3/14 9:56 AM Page 7 7 Anatomical Terms CHAPTER 1 Orientation to the Human Body Terms are crucial for navigating your way around the human body. Besides being used to identify the location of various body parts, the use of proper terms ensures accurate communication between health-care providers. Because the body is three-dimensional, a number of different terms are needed. These include directional terms as well as terms for body planes, body regions, and body cavities. Directional Terms Directional terms are generally grouped in pairs of opposites. Midline Right Left Medial: Toward the body’s midline Lateral: Away from the body’s midline Superior: Above Distal: Farthest from the point of origin Proximal: Closest to the point of origin Anterior (ventral): Toward the front of the body Posterior (dorsal): Toward the back of the body FAST FACT Superficial: At or near the body’s surface All terms are based on the body being in the anatomical position—standing erect, arms at the sides, with face, palms, and feet facing forward. Keep in mind, too, that the terms right and left Deep: Away from the always refer to the patient’s right and left side. body’s surface Inferior: Below 4373_01_001-015.qxp 11/3/14 9:56 AM Page 8 8 Body Planes Body planes divide the body, or an organ, into sections. PART I Organization of the Body Sagittal Plane Divides the body lengthwise into right and left sides Called a midsagittal plane if the section is made exactly at midline Often used in illustrations to reveal the organs in the head or pelvic cavity Transverse Plane Divides the body horizontally into upper (superior) and lower (inferior) portions Also called a horizontal plane Used by CT scanners to reveal internal organs Frontal Plane Divides the body lengthwise into anterior and posterior portions Also called a coronal plane FAST FACT Often used in illustrations to The frontal plane is also called a coronal show the contents of the plane because the line of the plane crosses abdominal and thoracic cavities the top, or crown, of the head. The word coronal comes from a Latin word meaning crown. 4373_01_001-015.qxp 11/3/14 9:56 AM Page 9 9 CHAPTER 1 Orientation to the Human Body Body Regions The illustration below shows the terms for the different regions of the body. These terms are used extensively when performing clinical examinations and medical procedures. Cephalic (head) Frontal (forehead) Orbital (eye) Nasal (nose) Buccal (cheek) Oral (mouth) Cervical (neck) Deltoid (shoulder) Sternal (sternum) Pectoral (chest) Thoracic Axillary (armpit) Mammary (breast) Brachial (arm) Antecubital Abdominal (abdomen) (front of elbow) Antebrachial (forearm) Pelvic Inguinal (groin) Carpal (wrist) Pubic Palmar Cranial (palm) (surrounding the brain) Digital (fingers) Otic (ear) Femoral (thigh) Occipital (back of head) Patellar (knee) Scapular Vertebral column (spine) Lumbar (lower back) Tarsal (ankle) Sacral Pedal (foot) Gluteal (buttock) Perineal Popliteal (back of knee) Calcaneal (heel) Plantar (sole of feet) 4373_01_001-015.qxp 11/3/14 9:56 AM Page 10 10 Body Cavities The body contains spaces—called cavities—that house the internal organs. The two major body cavities are the dorsal cavity and the ventral cavity. Each of these cavities is subdivided further, as shown below. PART I Organization of the Body Mediastinum Thoracic cavity Pleural cavity Diaphragm Abdominal cavity Abdominopelvic cavity Pelvic cavity Cranial cavity Thoracic cavity Dorsal cavity Diaphragm Ventral cavity Spinal cavity Abdominopelvic Abdominal cavity cavity Pelvic cavity Ventral Cavity Dorsal Cavity Located at the front of the body Located at the back of the body Consists of two compartments (the thoracic and abdominopelvic), Contains two divisions but is one continuous cavity which are separated by the diaphragm Thoracic cavity Cranial cavity Surrounded by ribs and chest muscles Formed by the skull Subdivided into two pleural cavities (each containing a lung) and the Contains the brain mediastinum The mediastinum contains the heart, large vessels of the heart, trachea, esophagus, thymus, lymph nodes, and other blood vessels and nerves Abdominopelvic cavity Spinal cavity Subdivided into the abdominal cavity and the pelvic cavity Formed by the vertebrae The abdominal cavity contains the stomach, intestines, spleen, liver, and Contains the spinal cord other organs The pelvic cavity contains the bladder, some of the reproductive organs, and the rectum 4373_01_001-015.qxp 11/3/14 9:56 AM Page 11 11 CHAPTER 1 Orientation to the Human Body Abdominal Regions and Quadrants Because the abdominopelvic cavity is so large, and because it contains numerous organs, it’s divided further into regions (which are used to locate organs in anatomical studies) as well as quadrants (which are used to pinpoint the site of abdominal pain). Abdominal Regions The illustration below shows the location of the nine abdominal regions. The chart beside it lists some (but not all) of the organs found in each quadrant. Note that some organs, such as the liver, stretch over multiple quadrants. Right Hypochondriac Epigastric Region Left Hypochondriac Region Stomach Region Liver Liver Stomach Gallbladder Pancreas Liver (tip) Right kidney Right and left kidneys Left kidney Spleen Right Lumbar Region Umbilical Region Left Lumbar Region Liver (tip) Stomach Small intestines Small intestines Pancreas Descending colon Ascending colon Small intestines Left kidney Right kidney Transverse colon Right Iliac Region Hypogastric Region Left Iliac Region Small intestines Small intestines Small intestines Appendix Sigmoid colon Descending colon Cecum and ascending Bladder Sigmoid colon colon Abdominal Quadrants Probably used most frequently, lines intersecting at the umbilicus divide the abdominal region into four quadrants. Life lesson: Abdominal pain Abdominal pain is a common complaint, but diagnosing the Right Left cause can be difficult. While some conditions cause pain in a upper upper particular quadrant—for example, appendicitis typically quadrant quadrant causes pain in the right lower quadrant—many times (RUQ) (LUQ) abdominal pain results from a disorder in an entirely different area. For example, disorders in the chest, including Right Left pneumonia and heart disease, can also cause abdominal pain. lower lower This is called referred pain. Likewise, although the gallbladder quadrant quadrant is located in the right upper quadrant of the abdomen—and (RLQ) (LLQ) may cause pain in this region—it may also cause referred pain in the shoulder. 4373_01_001-015.qxp 11/3/14 9:56 AM Page 12 12 Homeostasis To function properly, the body must maintain a relatively constant internal environment despite changes in external PART I Organization of the Body conditions. This constancy, or balance, is called homeostasis. Because the body must make constant changes to maintain balance, homeostasis is often referred to as maintaining a dynamic equilibrium. (Dynamic means “active,” and equilibrium means “balanced.”) If the body loses homeostasis, illness or even death will occur. Specifically, the body operates within a narrow range of temperature, fluids, and chemicals. This range of normal is called the set point or set point range. For example, the body’s internal temperature should remain between 97° and 99° F (36°– 37.2° C) despite the temperature outside the body. Likewise, blood glucose levels should remain between 65 and 99 mg/dl, even when you decide to indulge in an occasional sugar-laden dessert. Just as a gymnast must make constant physical adjustments to maintain balance on a balance beam, the body must make constant internal adjustments to maintain homeostasis. 98˚ F Temperature: 97˚–99˚ F Glucose Sodium (36˚–37.2˚ C) 65–99 mg/dl 135–146 mmol/l Calcium Chloride 8.5–10.4 98–110 mmol/l 32˚ F Potassium mg/dl 3.5–5.3 mmol/l Carbon dioxide 21–33 mmol/l Homeostasis: ! The Body AT WORK That Makes Sense Every organ system is involved in helping the body maintain homeostasis. None To grasp how homeostasis works, think of works in isolation. The body depends on all organ systems interacting together. balancing a pencil on your finger. If you hold In fact, a disruption in one body system usually has consequences in one or your finger still, the pencil will remain more other systems. motionless and balanced. This reflects static Consider how the following systems contribute to helping the body (or nonmoving) equilibrium. If you move generate heat: your finger slightly, the pencil will move. By making fine adjustments to your finger, you Nervous system: The hypothalamus in the brain contains the body’s can keep the pencil balanced as it moves. This “thermostat.” is dynamic equilibrium, just as homeostasis Cardiovascular system: Blood vessels constrict to conserve heat. is a type of dynamic equilibrium. If the pencil Muscular system: The muscles contract to cause shivering, which veers too far to one side, it will fall. In the body, generates heat. this type of shift results in disease. Integumentary system: Sweat production stops and “goose bumps” form, which creates an insulating layer. Endocrine system: Thyroid hormone production increases metabolism, which raises body temperature. Digestive system: The metabolism of food and stored fat generates heat. 4373_01_001-015.qxp 11/3/14 9:56 AM Page 13 13 CHAPTER 1 Orientation to the Human Body Homeostatic Regulation Maintaining a stable environment requires constant monitoring and adjustment as conditions change. This process of adjustment (called homeostatic regulation) involves: 1. a receptor (which receives information about a change in the environment), 2. a control center (which receives and processes information from the receptor), and 3. an effector (which responds to signals from the control center by either opposing or enhancing the stimulus). The signal sent by the effector is called feedback; feedback can be either negative or positive. Negative feedback: when the effector opposes the stimulus (such as a dropping temperature) and reverses the direction of change (causing the temperature to rise) Positive feedback: when the effector reinforces the stimulus (such as uterine contractions during childbirth, which trigger the release of the hormone oxytocin) and amplifies the direction of change (causing even greater contractions and further release of oxytocin) Most systems supporting homeostasis operate by negative feedback. Because positive feedback is stimulatory, there are only a few situations in which it is beneficial to the body (such as during childbirth or in blood clotting). More often, positive feedback is harmful (such as when a high fever continues to rise). Homeostatic Regulation Through Negative Feedback ANIMATION Change in environment The outside temperature falls. The outside temperature falls. 40 60 20 80 0 100 Receptor -20 120 -40 140 A thermometer in the house detects the falling temperature and sends a message to the Temperature receptors in the skin detect the falling thermostat. temperature and send a message to the brain. Control center 62˚ Actual 71˚ Set temp temp The hypothalamus in the brain receives the The thermostat has been adjusted to a “set point” of message that the body temperature is dropping 68°. When the temperature falls below that point, it below its “set point” and sends nerve impulses to sends a message to the furnace. the muscles. Effector The furnace then begins to generate heat, raising The muscles begin to shiver, causing the body the indoor temperature. temperature to rise. 4373_01_001-015.qxp 11/3/14 9:56 AM Page 14 14 Review of Key Terms PART I Organization of the Body Anatomy: The study of the structure Negative feedback: When the effector Proximal: Closest to the point of of the body opposes the stimulus and reverses the origin direction of change Anterior: Toward the front of the body Sagittal plane: Divides the body into Organ: Structures of two or more right and left sides Distal: Farthest from the point of tissue types that work together to origin Superficial: At or near the body’s carry out a particular function surface Dorsal cavity: Located at the back of Organelle: Metabolic units (or “tiny the body; contains the cranial and Superior: Situated above something organs”) within a cell that perform a spinal cavities else specific function necessary to the life Frontal plane:Divides the body of the cell Tissue: Specialized groups of cells with lengthwise into anterior and posterior similar structure and function Pathophysiology: Functional changes portions resulting from disease Transverse plane: Divides the body Homeostasis: The state of dynamic into upper (superior) and lower Physiology: The study of how the equilibrium of the internal environment (inferior) portions body functions of the body Located at the front of Ventral cavity: Positive feedback: When the effector Inferior: Beneath or lower the body; consists of the thoracic and reinforces the stimulus and amplifies abdominopelvic cavities Lateral: Away from the body’s midline the direction of change Medial: Toward the body’s midline Posterior: Toward the back of the body Own the Information To make the information in this chapter part of your Key Topics for Chapter 1: working memory, take some time to reflect on what you’ve Organization of the body learned. On a separate sheet of paper, write down Organ systems everything you recall from the chapter. After you’re done, Directional terms log on to the DavisPlus website, and check out the Study Body planes Group podcast and Study Group Questions for the chapter. Body regions Body cavities Abdominal regions and quadrants Homeostasis and homeostatic regulation