Chapter 1 - The Sciences of Anatomy and Physiology

Digestive System

Mechanically and chemically digests food materials, absorbs nutrients, and expels waste products.

Responsiveness

All organisms exhibit responsiveness, which is the ability to sense and react to stimuli (changes in the external or internal environment). A stimulus to the skin of the hands, such as an extremely hot temperature, causes the human to withdraw the hand from the stimulus so as to prevent injury or damage. Responsiveness occurs at almost all levels of organization.

Embryology

Embryology is the discipline concerned with developmental changes occurring from conception to birth.

Urinary System

Filters the blood to remove waste products and biologically active molecules, concentrates waste products in the form of urine, and expels urine from the body.

hypochondriac regions

The right and left hypochondriac regions are inferior to the costal cartilages and lateral to the epigastric region.

Iliac regions

The right and left iliac regions are lateral to the hypogastric region.

Lymphatic System

Transports and filters lymph (interstitial fluid transported through lymph vessels) and participates in an immune response when necessary.

Several properties are common to all organisms, including humans:

- Organization. - Metabolism. - Growth and Development. - Responsiveness. - Regulation. - Reproduction.

Regulation

An organism must be able to adjust or direct internal bodily function in the face of environmental changes. When body temperature rises, the body regulates this change by circulating more blood near its surface to facilitate heat loss, and thus return the body to within normal range. (The process of maintaining body structures and function is called homeostasis, which is discussed in greater depth in section 1.5)

Endocrine System

Consists of glands and cell clusters that secrete hormones, which regulate development, growth and metabolism; maintain homeostasis of blood composition and volume, control digestive processes, and control reproduction.

anatomic position

For accuracy and clarity, anatomists and physiologists describe these parts based on the premise that the body is in what is termed the anatomic position, which is then the point of common reference. An individual in the anatomic position stands upright with the feet parallel and flat on the floor, the upper limbs are at the sides of the body, and the palms face anteriorly (toward the front); the head is level, and the eyes look forward toward the observer (figure 1.4). All of the anatomic and directional terms used in this book refer to the body in anatomic position.

The tissue level

consists of tissues, which are groups of similar cells that perform common functions. There are four major types of tissues. Epithelial tissue covers exposed surfaces and lines body cavities. Connective tissue protects, supports, and binds structures and organs. Muscle tissue produces movement. Finally, nervous tissue conducts nerve impulses for communication.

Pathologic anatomy

examines all anatomic changes resulting from disease. Both gross anatomic changes and microscopic structures are examined.

Neurophysiology

examines how nerve impulses travel throughout the nervous system

Pathophysiology

investigates the relationship between the functioning of an organ system and disease or injury to that organ system. For example, a pathophysiologist would examine how blood pressure, contractile force of the heart, and both gas and nutrient exchange may be affected in an individual afflicted with heart disease.

Cardiovascular System

Consists of the heart and blood vessels; the heart moves blood through blood vessels in order to distribute hormones, nutrients, gases, and pick up waste products.

Growth and Development.

During their lifetime, organisms assimilate materials from their environment and often exhibit increased size (growth) and increased specialization as related to form and function (development). As the human body grows and develops, structures such as the brain become more complex and sophisticated.

Establishing Normal Ranges for Clinical Practice

It is interesting to know that what is clinically accepted as the "normal range" for a variable, such as body temperature of 98.6°F, blood glucose of 80-110 milligrams/ deciliter (mg/dL), or blood pressure of 90-120/60-80 mm Hg is determined by sampling healthy individuals in a population. A normal range for a variable is determined by the value for 95% of the individuals sampled. Health-care practitioners should be aware that this means that 5% of the population, although healthy, will have values for a given variable considered outside of the normal range.

Respiratory System

Responsible for exchange of gases (oxygen and carbon dioxide) between blood and the air in the lungs.

Receptor

- The receptor is the body structure that detects changes in a variable, which is a substance or process that is regulated. - A receptor typically consists of sensory neurons (nerve cells). These neurons may be in the skin, internal organs of the body, or specialized organs such as the eye, ear, tongue, or nose. For example, the retina of the eye (receptor) detects a change in light (stimulus) entering the eye.

the organismal level

The highest level of structural organization in the body is. All body systems function interdependently in an organism, which is the living being.

Nervous System

A regulatory system that controls muscles and some glands and responds to sensory stimuli. Also responsible for consciousness, intelligence, memory

midsagittal (mid-saj′˘ı-t˘al; sagitta = arrow) plane

A, or median plane, is a vertical plane and divides the body or organ into left and right halves. A midsagittal plane through the head will split it into a left half and a right half (each containing one eye, one ear, and half of the nose and mouth). A plane that is parallel to the midsagittal plane, but either to the left or right of the midsagittal plane, is termed a sagittal plane. A sagittal plane divides a structure into left and right portions that are not equal. Although there is only one midsagittal plane, an infinite number of sagittal planes are possible.

Organization

All organisms exhibit a complex structure and order.

Homeostatic Systems Regulated by Negative Feedback

Learning Objectives 3. Define negative feedback. 4. Explain how homeostatic mechanisms regulated by negative feedback detect and respond to environmental changes. Most processes in the body are controlled by negative feedback. If a homeostatic system is controlled by negative feedback, the resulting action will always be in the opposite direction of the stimulus. In this way, the variable is maintained within a normal level, or what is called its set point. How a variable that is regulated by negative feedback fluctuates over time can be viewed in figure 1.12. Notice that the variable does not remain constant over time but rather it fluctuates, and its fluctuation occurs around the set point. If the stimulus increases, the homeostatic system is activated to cause a decrease in the stimulus until it returns to the set point. In contrast, if the stimulus decreases, the homeostatic system causes an increase in the stimulus until it returns to normal. This idea is generally better understood by describing a specific example, such as temperature regulation. Temperature Regulation We begin by first explaining how a negative feedback mechanism works to maintain the temperature of your home at a set point of 70°F. On a very cold day, the indoor temperature drops. This drop in temperature is detected by the thermostat. The drop in temperature is relayed through the electrical wiring of your home to the heat pump, which is then activated. The heat pump continues to heat your home until the thermostat reaches 70°F. An electrical signal is then sent from the thermostat to shut off the heat pump. Body temperature is regulated in an analogous way to how the temperature of your home is regulated (figure 1.13a). If you venture outside on a cold day, body temperature may begin to drop. This decrease in body temperature is detected by the sensory receptors of the skin, which send nerve impulses to the hypothalamus (a component of the brain). (The hypothalamus can also directly detect changes in body temperature by monitoring blood temperature as it passes through this region of the brain.) The hypothalamus compares sensory input to body temperature set point, and initiates motor output responses to blood vessels in the skin to decrease the diameter of the inside opening (lumen) of the vessels, thus decreasing the amount of blood circulating to the surface of the body. As a result, less heat is released through the skin. Nerve impulses are also sent to skeletal muscles, which cause shivering, and perhaps to smooth muscle associated with hair follicles of the skin, causing "goose bumps." In contrast, on a very hot day (figure 1.13b), or when you are engaging in strenuous exercise, an increase in body temperature is detected by the sensory receptors of the skin or hypothalamus. The hypothalamus detects the difference between the increased body temperature and the original temperature set point, and transmits motor output to the blood vessels of the skin. This change increases the lumen diameters of blood vessels so that additional blood is brought near the surface of the body for the release of heat through the skin. Nerve impulses are also sent from the hypothalamus to the sweat glands to initiate sweating. Both responses help cool the body by the loss of heat from its surface. In these examples, regulation occurs through the nervous system. Other examples of homeostatic regulation through the nervous system include the withdrawal reflex in response to injury from stepping on glass or burning your hand (see section 14.6), regulating heart rate and blood pressure when you exercise (see section 20.6), or changing breathing rate in response to an increase in carbon dioxide levels (see section 23.5). Recall that the control center may also be the endocrine system. Examples of homeostatic systems that regulate through the endocrine system include the parathyroid gland release of parathyroid hormone in response to a decrease in blood calcium ( see section 7.6) or pancreas release of insulin in response to an increase in blood glucose (see section 17.9).

Muscular System

Produces body movement, generates heat when muscles contract.

transverse plane

also called a horizontal plane or cross-sectional plane, divides the body or organ into superior (top) and inferior (bottom) parts. If a transverse plane is taken through the middle of the trunk, the superior portion contains the chest and the inferior portion contains the abdomen.

Metabolism

which is defined as the sum of all of the chemical reactions that occur within the body. • Anabolism - where small molecules are joined to form larger molecules • Catabolism - where large molecules are broken down into smaller molecules

homeostatic imbalance

- Sometimes results when critical changes from aging or disease cause a variable that is normally controlled by negative feedback, to be abnormally controlled by positive feedback. drugs patients are taking may affect the normal homeostatic control mechanisms. For example, one type of medication for the treatment of depression is an SSRI, which stands for selective serotonin reuptake inhibitor

Effector

- The effector is the structure that brings about the change to alter the stimulus. - Most body structures can serve as effectors. The most common effectors are muscles and glands. For example, smooth muscle in the walls of air passageways (bronchioles) regulate airflow into and out of the lungs. Glands, such as the pancreas, release hormones (e.g., insulin).

stimulus

A stimulus is a change in the variable (a physical or chemical factor), such as a change in light, temperature, chemicals (e.g., glucose or oxygen levels), or stretch in muscle.

Surface anatomy

Surface anatomy focuses on both superficial anatomic markings and the internal body structures that relate to the skin covering them. Health-care providers use surface features to identify and locate important landmarks, such as pulse locations or the proper body region on which to perform cardiopulmonary resuscitation (CPR). Most anatomy and physiology classes also instruct students on important surface anatomy locations.

Female Reproductive System

Produces female sex cells (oocytes) and female hormones (e.g., estrogen and progesterone), receives sperm from male, site of fertilization of oocyte, site of growth and development of embryo and fetus, produces and secretes breast milk for nourishment of newborn.

Male Reproductive System

Produces male sex cells (sperm) and male hormones (e.g., testosterone), transfers sperm to the female.

A coronal plane

(kˉ or′ˉ o-n˘ al; korone = crown) plane, also called a frontal plane, is a vertical plane that divides the body or organ into anterior (front) and posterior (back) parts. When a coronal plane is taken through the trunk, the anterior portion contains the chest and the posterior portion contains the back and buttocks.

body cavities

Enclosed spaces where internal organs and organ systems are housed. Named either according to the bones that surround them or the organs they contain.

respiratory physiology

studies how respiratory gases are transferred by gas exchange between the lungs and the blood vessels

abdominopelvic regions

Smaller compartments within abdominopelvic cavity delineated by using two transverse planes and two sagittal planes. The 9 regions are: • The umbilical region is the middle region and is named for the umbilicus, or navel that lies in its center. • The epigastric region is the superior region above the umbilical region. • The hypogastric region lies inferior to the umbilical region. • The right and left hypochondriac regions are inferior to the costal cartilages and lateral to the epigastric region. • The right and left lumbar regions are lateral to the umbilical region. The right and left iliac regions are lateral to the hypogastric region.

Serous Membranes

a continuous layer of cells, that encase the subdivisions of the ventral cavity (1) a parietal layer that typically lines the internal surface of the body wall and (2) a visceral layer that covers the external surface of the organs (collectively the viscera) within that cavity. serous cavity - space between the parietal and visceral serous membrane layers serous fluid - secreted by serous membrane within the serous cavity; has the consistency of oil and serves as a lubricant. In a living human, organs (e.g., heart, lungs, intestines) are moving and rubbing against each other and the body wall. Friction caused by this movement is reduced by the serous fluid so the organs move more smoothly against one another and the body walls. Serous membranes will be discussed again in section 5.5b.

Negative Feedback

Most processes in the body are controlled by negative feedback. If a homeostatic system is controlled by negative feedback, the resulting action will always be in the opposite direction of the stimulus. In this way, the variable is maintained within a normal level, or what is called its set point. How a variable that is regulated by negative feedback fluctuates over time can be viewed in figure 1.12. Notice that the variable does not remain constant over time but rather it fluctuates, and its fluctuation occurs around the set point. If the stimulus increases, the homeostatic system is activated to cause a decrease in the stimulus until it returns to the set point. In contrast, if the stimulus decreases, the homeostatic system causes an increase in the stimulus until it returns to normal. This idea is generally better understood by describing a specific example, such as temperature regulation.

Integumentary System

Provides protection, regulates body temperature, site of cutaneous receptors and some glands, synthesizes vitamin D, prevents water loss.

Physiology

Study of function of the body parts. Examine how organs and body systems function under normal circumstances, as well as how their functioning may be altered via medication or disease. Physiologists examine the function of various organ systems, and they typically focus on the molecular or cellular level. Thus, a basic knowledge of both chemistry and cells is essential in understanding physiology, and that's why we've included several early chapters on these topics. Mastery of these early chapters on chemistry and cells is critical to understanding the physiologic concepts that are covered throughout the text. The discipline of physiology parallels anatomy because it also is very broad and may be subdivided into smaller groups. Many specific physiology subdisciplines focus their studies on a particular body system. • Cardiovascular physiology • Neurophysiology • Respiratory physiology • Reproductive physiology • Pathophysiology

Anatomy

Study the structure and form of organisms. Examine the relationships among parts of the body as well as the structure of and composition of individual organs.

Systemic anatomy

Systemic anatomy studies the anatomy of each functional body system. For example, studying the urinary system would involve examining the kidneys (where urine is formed) and the organs of urine transport (ureters and urethra) and storage (urinary bladder). Most undergraduate anatomy and physiology classes use this systemic approach.

Homeostatic Systems Regulated by Negative Feedback

Temperature Regulation We begin by first explaining how a negative feedback mechanism works to maintain the temperature of your home at a set point of 70°F. On a very cold day, the indoor temperature drops. This drop in temperature is detected by the thermostat. The drop in temperature is relayed through the electrical wiring of your home to the heat pump, which is then activated. The heat pump continues to heat your home until the thermostat reaches 70°F. An electrical signal is then sent from the thermostat to shut off the heat pump. Body temperature is regulated in an analogous way to how the temperature of your home is regulated (figure 1.13a). If you venture outside on a cold day, body temperature may begin to drop. This decrease in body temperature is detected by the sensory receptors of the skin, which send nerve impulses to the hypothalamus (a component of the brain). (The hypothalamus can also directly detect changes in body temperature by monitoring blood temperature as it passes through this region of the brain.) The hypothalamus compares sensory input to body temperature set point, and initiates motor output responses to blood vessels in the skin to decrease the diameter of the inside opening (lumen) of the vessels, thus decreasing the amount of blood circulating to the surface of the body. As a result, less heat is released through the skin. Nerve impulses are also sent to skeletal muscles, which cause shivering, and perhaps to smooth muscle associated with hair follicles of the skin, causing "goose bumps." In contrast, on a very hot day (figure 1.13b), or when you are engaging in strenuous exercise, an increase in body temperature is detected by the sensory receptors of the skin or hypothalamus. The hypothalamus detects the difference between the increased body temperature and the original temperature set point, and transmits motor output to the blood vessels of the skin. This change increases the lumen diameters of blood vessels so that additional blood is brought near the surface of the body for the release of heat through the skin. Nerve impulses are also sent from the hypothalamus to the sweat glands to initiate sweating. Both responses help cool the body by the loss of heat from its surface. In these examples, regulation occurs through the nervous system. Other examples of homeostatic regulation through the nervous system include the withdrawal reflex in response to injury from stepping on glass or burning your hand (see section 14.6), regulating heart rate and blood pressure when you exercise (see section 20.6), or changing breathing rate in response to an increase in carbon dioxide levels (see section 23.5). Recall that the control center may also be the endocrine system. Examples of homeostatic systems that regulate through the endocrine system include the parathyroid gland release of parathyroid hormone in response to a decrease in blood calcium ( see section 7.6) or pancreas release of insulin in response to an increase in blood glucose (see section 17.9).

Thoracic Cavity

Thoracic Cavity The median space in the thoracic cavity is called the mediastinum (mˉ e-dˉ e-as-tˉı′n˘um; medius = middle) (figure 1.8b). It contains the heart, thymus, esophagus, trachea, and major blood vessels that connect to the heart. Within the mediastinum, the heart is enclosed by a two-layered serous membrane called the serous pericardium (per-˘ı-kar′d ˉ e-˘um; peri = around, kardia = heart). The parietal pericardium is the outermost layer of the serous membrane and forms the sac around the heart, whereas the visceral pericardium forms the heart's external surface (figure 1.9b). The pericardial cavity is the potential space between the parietal and visceral layers of the pericardium, and it contains serous fluid. The right and left sides of the thoracic cavity house the lungs, which are associated with a two-layered serous membrane called the pleura (plˉur′˘ a; = a rib) (figure 1.9c). The parietal pleura is the outer layer of the serous membrane and lines the internal surface of the thoracic wall. The inner layer is the visceral pleura, which covers the external surface of each lung. The pleural cavity is the potential space between these parietal and visceral layers, and it contains serous fluid.

1 When you digest a meal, what type of metabolic reactions do you think you are utilizing primarily: anabolic or catabolic chemical reactions? Why?

When you digest a meal, you are utilizing primarily catabolic chemical reactions, because the main goal is to break down larger molecules (such as starches in bread) into smaller molecules (such as simple sugars) that can be absorbed.

The cellular level

consists of cells, which are the smallest living structures and serve as the basic units of structure and function in organisms. Cells and their components are formed from the atoms and molecules from the chemical level. The structures of cells vary widely, reflecting the specializations needed for their different functions. For example, a skeletal muscle cell may be very long and contain numerous organized protein filaments that aid in muscle contraction, whereas a red blood cell is small and has a flattened disc shape that facilitates the quick and effective exchange of respiratory gases.

The organ system level

contains related organs that work together to coordinate activities and achieve a common function. For example, the organs of the digestive system (e.g., oral cavity, stomach, small and large intestine, and liver) work together to digest food particles, absorb nutrients, and expel the waste products.

Computed Tomography (CT)

- A computed tomography, previously termed a computerized axial tomography (CAT) scan, is a more sophisticated application of x-rays. A patient is slowly moved through a cylindrical, doughnut-shaped machine while low-intensity x-rays are emitted on one side the cylinder, passed through the body, collected by detectors, and then processed and analyzed by a computer. These signals produce an image of the body that is about the thickness of a dime. Continuous thin "slices" can be used to reconstruct a three-dimensional image of the body. Little overlap of organs occurs in these thin sections, and the image is much sharper than one obtained by a conventional x-ray. CT scanning is useful for identifying tumors, aneurysms, kidney stones, cerebral hemorrhages, and other abnormalities. A drawback to CTs is that they expose the patient to higher doses of radiation than a traditional x-ray.

feedback loop of a homeostatic system

- A stimulus - The detection of the stimulus by a receptor - Input information relayed to the control center (if a separate structure) - Integration of the input by the control center and initiation of a change through effectors Return of homeostasis by the actions of effectors

Medical Imaging

- Health-care professionals have taken advantage of sophisticated medical imaging techniques to extend their ability to visualize internal body structures noninvasively (e.g., without inserting an instrument into the body). Some of the most common techniques are radiography, sonography, computed tomography, digital subtraction angiography, dynamic spatial reconstruction, magnetic resonance imaging, and positron emission tomography.

Magnetic Resonance Imaging (MRI)

- Magnetic resonance imaging (MRI), previously called nuclear magnetic resonance (NMR) imaging, was developed as a noninvasive technique to visualize soft tissues. - The patient is placed in a supine position within a cylindrical chamber that is surrounded by a large electromagnet. The magnet generates a strong magnetic field that causes protons in the nuclei of hydrogen atoms in the tissues to align. - Thereafter, upon exposure to radio waves, the protons absorb additional - energy and align in a different direction. The hydrogen atoms then - abruptly realign themselves to the magnetic field immediately after the radio waves are turned off. This results in the release of the atoms' excess energy at different - rates, depending on the type of tissue. A computer analyzes the emitted energy to produce an image of the body. MRI is better than CT for distinguishing between - soft tissues, such as the white and gray matter of the nervous system. - However, dense structures (e.g., bone) do not show up well in MRI. Formerly, another disadvantage of MRI was that patients felt claustrophobic while isolated in the closed cylinder. However, newer MRI technology has improved the hardware and lessened this effect. A specific type of MRI, called functional MRI (fMRI), provide the means to map brain function based on local oxygen concentration differences in blood flow. Increased blood flow relates to increased brain activity and is detected by a decrease in deoxyhemoglobin (the form of hemoglobin lacking oxygen) in the blood.

Control Center

- The control center is the structure that interprets input from the receptor and initiates changes through the effector. - The control center is generally a portion of the nervous system (brain or spinal cord) or an endocrine organ (such as the thyroid gland). - A homeostatic system involving the nervous system provides a relatively quick means of responding to change. An example is regulating blood pressure when you rise from bed in the morning. - In contrast, the endocrine system usually provides a means of a more sustained response over several hours or days through the release of hormones. An example is when the parathyroid hormone continuously regulates blood calcium levels, a process that is essential for the normal function of both muscles and nerves. - Note that the control center is sometimes the same structure as the receptor because it both detects the stimulus and causes a response to regulate it. For example, the pancreas acts as a receptor because it detects an increase in blood glucose and also acts as a control center because it releases the hormone insulin in response.

Positron Emission Tomography (PET)

- The positron emission tomography (PET) scan is used both to analyze the metabolic state of a tissue at a given moment in time and to determine which tissues are most active. The procedure begins with an injection of radioactively labeled glucose (sugar), which emits particles called positrons (like electrons, but with a positive charge). Collisions between a positron and electron cause the release of gamma rays that can be detected by sensors and analyzed by computer. The result is a brilliant color image that shows which tissues were using the most glucose at that moment. In cardiology, the image can reveal the extent of damaged heart tissue—because damaged heart tissue consumes little or no glucose, the damaged tissue will appear dark. PET scans have also been used to illustrate activity levels in the brain. PET scans also may detect whether certain cancers have metastasized throughout the body, because cancerous cells will take up more glucose and show up as a "hot spot" on the scan. The PET scan is an example of nuclear medicine, which uses radioactive isotopes to form anatomic images of the body. - Positron emission tomography (PET) scan of the brain of an unmedicated schizophrenic patient. Red areas indicate high glucose use (metabolic activity). The visual center at the posterior region of the brain was especially active when the scan was made.

Sonography

- The second most widely used imaging method is sonography , aka ultrasound. - A technician slowly moves a small, handheld device across the body surface. This device produces high-frequency ultrasound waves and then receives signals that are reflected from internal organs. The image produced is called a sonogram. Sonography is the method of choice in obstetrics, where a sonogram can visualize the placenta, examine the fetus and evaluate fetal age, position, and development. Sonography avoids the harmful effects of x-rays, and the equipment is inexpensive and portable. - Improvements include three-dimensional and four-dimensional ultrasound. - In three-dimensional ultrasound, sound waves are emitted in various angles and processed in a computer. This creates a three-dimensional view. A two-dimensional ultrasound is a flat image and a three-dimensional ultrasound shows depth, contour, and detail. Four-dimensional ultrasound shows movement using a compilation of three-dimensional images. Movements like heart motion and yawning can be seen in real time. When radiography or sonography fail to produce the desired images, other more detailed but much more expensive imaging techniques are available.

Dynamic Spatial Reconstruction (DSR)

- Using modified CT scanners, a special technique called dynamic spatial reconstruction (DSR) provides two important pieces of medical information: three-dimensional images of body organs, and (2) information about the normal organ movement as well as changes in its internal volume. Unlike traditional static CT scans, DSR allows the physician to see the movement

Diabetes

- is an example of a homeostatic imbalance. - occurs when the homeostatic mechanisms for regulating blood glucose are not functioning normally, and blood glucose fluctuates out of the normal range, sometimes resulting in extremely high blood glucose readings. - High blood glucose results in damage to anatomic structures throughout the body. Patients with diabetes must rely on other methods, such as diet restriction, exercise, and perhaps a medication to lower blood glucose.

Radiography

- is the primary method of obtaining an image of a body part for diagnostic purposes. - A beam of x-rays, which are a form of high energy radiation, penetrates solid structures within the body. X-rays can pass through soft tissues but they are absorbed by dense tissues, including bone, teeth, and tumors. - Film images produced by x-rays passing through soft tissues leave the film lighter in the areas where x-rays are absorbed. - Hollow organs can be visualized if they are filled with a radiopaque (raˉ-deˉ-oˉ -paˉk; opacus = shady) substance that absorbs x-rays. - The term x-ray also applies to the photograph (radiograph) made by this technique. Originally, x-rays got their name because they were an unknown type of radiation, but they are also called roentgen rays in honor of Wilhelm Roentgen, the German physicist who accidentally discovered them. Radiography is commonly used in dentistry, mammography, diagnosis of fractures, and chest examination. Disadvantages of x-rays are that they are difficult to interpret when organs overlap in the images, and they are unable to reveal slight differences in tissue density. In addition, the radiation of an x-ray is not without risk.

sections or planes

- refer to real or imaginary "slices" of the body, - to examine the internal anatomy and describe the position of one body part relative to another. - The term section implies an actual cut or slice to expose the internal anatomy, whereas the word plane implies an imaginary flat surface passing through the body. - The three major anatomic planes are: o the coronal, o transverse, and o midsagittal planes

homeostasis

- refers to the ability of an organism to maintain consistent internal environment, or "steady state," in response to changing internal or external conditions. - In this section, we introduce you to the general concept of homeostasis. - We describe the general components of homeostatic systems, - provide specific examples of these regulatory processes, and then describe the relationship of homeostasis, health, and disease. Maintained by utilizing homeostatic control systems: - receptor, - control center, and effector In summary, is a term that describes the many physiologic processes to maintain the health of the body. These characteristics are noted about homeostatic systems: • They are dynamic. • The control center is generally the nervous system or the endocrine system. • There are three components: receptor, control center, and effector. • They are typically regulated through negative feedback to maintain a normal value or set point. It is when these systems fail that a homeostatic imbalance or disease results, ultimately threatening an individual's survival.

Homeostatic Systems Regulated by Positive Feedback

A homeostatic system may also be controlled by positive feedback. The stimulus here is reinforced to continue in the same direction until a climactic event occurs (figure 1.14). Following the climactic event, the body again returns to homeostasis. Because their end result is to increase the activity (instead of initially returning the body to homeostasis), positive feedback mechanisms occur much less frequently than negative feedback mechanisms. Figure 1.15 illustrates one example of a positive feedback mechanism in the human body, when a mother breastfeeds her baby. The baby suckling at the breast is the initial stimulus detected by sensory receptors in the skin of the nipple region. The receptors transmit this input to the control center, which is the hypothalamus of the brain. The hypothalamus signals the posterior pituitary to release the hormone oxytocin into the blood. Oxytocin is the "output" that is sent to the effector, which is the glandular tissue of the breast. Oxytocin stimulates the mammary gland to eject the breast milk. The baby feeds and the cycle repeats as long as the baby suckles. Once the baby stops suckling (and thus the initial stimulus is removed), then the cycle will stop. Other examples of positive feedback mechanisms include the blood clotting cascade (see section 18.4) and uterine contractions involved in labor and childbirth (see section 29.6).

Compare the organ systems of the human body.

All organisms must exchange nutrients, wastes, and gases with their environment to carry on their metabolism. Simple organisms (e.g., bacteria) may exchange these substances directly across their surface membranes. In contrast, complex, multicellular organisms require sophisticated organ systems with specialized structures and functions to perform the myriad of activities required for the routine events of life. In humans, 11 organ systems are commonly denoted, each composed of interrelated organs that work in concert to perform specific functions (figure 1.3). A person maintains a healthy body through the intricate interworkings of all of its organ systems. Subsequent chapters examine each of these organ systems in detail.

Reproduction

All organisms produce new cells for growth, maintenance, and repair. The somatic (body) cells divide by a process called mitosis, whereas sex cells (called gametes) are produced by another type of cell division called meiosis. The sex cells, under the right conditions, have the ability to develop into a new living organism.

levels of organization in the human body

Anatomists and physiologists recognize several levels of increasingly complex organization in humans, as illustrated in figure 1.2. These levels, from simplest to most complex, are the chemical level, cellular level, tissue level, organ level, organ system level, and organismal level. Throughout future chapters, boxes like this one will highlight how various organ systems do not work in isolation, but rather are interconnected to carry out overlapping functions. For example, the cardiovascular system and respiratory system work together in the transport of respiratory gases (oxygen and carbon dioxide) by the blood throughout the body.

cardiovascular physiology

Cardiovascular physiology examines the functioning of the heart, blood vessels, and blood. Cardiovascular physiologists examine how the heart pumps the blood, what are the parameters for healthy blood pressure, and details of the cellular exchange mechanisms by which respiratory gases, nutrients, and wastes move between blood and body structures.

Clinicians' Use of Scientific Method

Clinicians regularly apply the principles of the scientific method when interacting with patients. Consider what typically occurs when a patient with a health problem or complaint goes in for a doctor's appointment. First, information is gathered. The nurse obtains the patient's weight, blood pressure, and other vital signs. The physician solicits the patient's medical history, asks about his or her specific complaint(s), and completes a physical examination. Based on the information gathered, the clinician forms a hypothesis or a tentative explanation of any specific symptoms the patient may be experiencing. As a follow-up to the initial hypothesis, the clinician orders tests and evaluates the test results. After all information is gathered, the clinician draws a conclusion to make a diagnosis. (Sometimes additional tests may be ordered if the test results are inconclusive.) Following a definitive diagnosis, the clinicians treat the patient and additional information is gathered as the patient's response to the treatment is monitored.

Comparative anatomy

Comparative anatomy examines similarities and the differences in the anatomy of different species. For example, a comparative anatomy class may examine limb structure in humans, chimps, dogs, and cats.

Digital Subtraction Angiography (DSA)

Digital subtraction angiography (DSA) is a modified three-dimensional x-ray technique used primarily to view blood vessels. It involves taking radiographs both prior to and after injecting an opaque medium into a blood vessel. The computer compares the before and after images, and removes or subtracts the data from the before image from the data generated by the after image, thus leaving an image that may indicate evidence of vessel blockages. DSA is useful in the procedure in which a physician directs a catheter through a blood vessel and puts a stent in the area where a blood vessel is blocked. The image produced by the DSA allows the physician to accurately guide the catheter to the blockage.

Skeletal System

Provides support and protection, site of hemopoiesis (blood cell production), stores calcium and phosphorus, provides sites for muscle attachments.

Microscopic anatomy

Examines structures that cannot be seen by the unaided eye. For most of these studies, scientists prepare individual cells or thin slices of some part of the body and examine these specimens under the microscope. Microscopic anatomy has several subdivisions with two main divisions: • Cytology - is the study of body cells and their internal structure. • Histology - is the study of tissues.

WHAT DO YOU THINK? 2 What do you think would happen to your body organs if there were no serous fluid between the parietal and visceral layers?

If you didn't have the lubricating serous fluid,there would be increased friction and it would be quite painful whenever your organs moved. For example, the illness pleurisy (inflammation of the pleura) makes it very painful to breathe, because the pleural membranes are inflamed and the serous fluid cannot appropriately lubricate the membranes.

oblique

In addition to these major planes, there are numerous minor planes called oblique (ob-lˉ ek′) planes that pass through a structure at an angle (figure 1.5).

The scientific method

Refers to a systematic and rigorous process by which scientists: - Examine natural events (or phenomena) through observation - Develop a hypothesis (possible explanation) for explaining these phenomena - Experiment and test the hypothesis through the collection of data - Determine if the data support the hypothesis, or if the hypothesis needs to be rejected or modified.

Regional anatomy

Regional anatomy examines all of the structures in a particular region of the body as a complete unit. For example, one may study the axillary (armpit) region of the body, and in so doing examine the blood vessels (axillary artery and vein), nerves (branches of the brachial plexus), lymph nodes (axillary lymph nodes), musculature, connective tissue, and skin. Most medical school gross anatomy courses are taught using a regional anatomy approach.

Abdominopelvic Cavity

The abdominopelvic cavity may be subdivided into two smaller cavities by a horizontal plane at the level of the superior aspects of the hip bones. The area superior to this plane is the abdominal cavity; the pelvic cavity lies inferior to this plane where it is wedged between the two hip bones. You can locate the division between these two cavities by palpating (feeling for) the superior ridges of your hip bones. The abdominal cavity contains most of digestive system organs, as well as the kidneys and most of the ureters. The pelvic cavity contains the distal part of the large intestine, the remainder of the ureters and the urinary bladder, and the internal reproductive organs. The peritoneum (per′i-toˉ-neˉ′um; periteino = to stretch over) is the two-layered serous membrane that lines the abdominopelvic cavity (figure 1.9d). The parietal peritoneum, the outer layer of this serous membrane, lines the internal walls of the abdominopelvic cavity. The visceral peritoneum is the inner layer of this serous membrane, and it covers the external surfaces of most abdominal and pelvic organs. The potential space between these serous membrane layers is the peritoneal cavity, which contains and is lubricated by serous fluid.

Abdominopelvic Cavity - parts of

The abdominopelvic cavity may be subdivided into two smaller cavities by a horizontal plane at the level of the superior aspects of the hip bones. The area superior to this plane is the abdominal cavity; the pelvic cavity lies inferior to this plane where it is wedged between the two hip bones. You can locate the division between these two cavities by palpating (feeling for) the superior ridges of your hip bones. The abdominal cavity contains most of digestive system organs, as well as the kidneys and most of the ureters. The pelvic cavity contains the distal part of the large intestine, the remainder of the ureters and the urinary bladder, and the internal reproductive organs. The peritoneum (per′i-toˉ-neˉ′um; periteino = to stretch over) is the two-layered serous membrane that lines the abdominopelvic cavity (figure 1.9d). The parietal peritoneum, the outer layer of this serous membrane, lines the internal walls of the abdominopelvic cavity. The visceral peritoneum is the inner layer of this serous membrane, and it covers the external surfaces of most abdominal and pelvic organs. The potential space between these serous membrane layers is the peritoneal cavity, which contains and is lubricated by serous fluid.

Epigastric region

The epigastric region is the superior region above the umbilical region.

Hypogastric

The hypogastric region lies inferior to the umbilical region.

Thoracic cavity

The median space in the thoracic cavity is called the mediastinum. It contains the heart, thymus, esophagus, trachea, and major blood vessels that connect to the heart. Within the mediastinum, the heart is enclosed by a two-layered serous membrane called the serous pericardium (per-˘ı-kar′d ˉ e-˘um; peri = around, kardia = heart). The parietal pericardium is the outermost layer of the serous membrane and forms the sac around the heart, whereas the visceral pericardium forms the heart's external surface (figure 1.9b). The pericardial cavity is the potential space between the parietal and visceral layers of the pericardium, and it contains serous fluid. The right and left sides of the thoracic cavity house the lungs, which are associated with a two-layered serous membrane called the pleura (plˉur′˘ a; = a rib) (figure 1.9c). The parietal pleura is the outer layer of the serous membrane and lines the internal surface of the thoracic wall. The inner layer is the visceral pleura, which covers the external surface of each lung. The pleural cavity is the potential space between these parietal and visceral layers, and it contains serous fluid.

Explain how the studies of form and function are interrelated.

The sciences of anatomy and physiology are intertwined; one must have some understanding of anatomic form to study physiologic function of a structure. Likewise, one cannot adequately describe and understand the anatomic form of an organ without learning that organ's function. This interdependence of the study of anatomy and physiology reflects the inherent and important interrelationship of how the structure and form of a component of the body determines how it functions. This concept is central to mastering the study of anatomy and physiology. Integrating the disciplines of anatomy and physiology, rather than trying to separate discussion of form and function, is the easiest way to learn about both fields. Anatomists and physiologists may be describing the organs slightly differently, but both disciplines must use information from the other field for a full understanding of the organ system. You cannot fully understand how the small intestine propels food and digests or absorbs nutrients unless you know about the structure of the small intestine wall. Figure 1.1 visually compares how anatomists and physiologists examine the human body, using the small intestine as an example. Note that anatomists (left side of the figure) tend to focus on the form and structure, whereas physiologists (right side of figure) focus on the mechanisms and functions of these structures. However, both anatomists and physiologists understand that the form and function of structures are interrelated. Throughout this text, we integrate these disciplines so you can more easily see that anatomic form and physiologic function are inseparable.

Umbilical region

The umbilical region is the middle region and is named for the umbilicus, or navel that lies in its center.

Gross anatomy

also called macroscopic anatomy, investigates the structure and relationships of body parts that are visible to the unaided eye, such as the intestines, stomach, brain, heart, and kidneys. In these macroscopic investigations, specimens or their parts are often dissected (cut open) for examination. Gross anatomy may be approached in several ways: - Systemic anatomy - Regional anatomy - Surface anatomy - Comparative anatomy - Embryology

Homeostatic control systems

are separated into two broad categories based on whether the system maintains the variable within a normal range by moving the stimulus in the opposite direction, or amplifies the stimulus in the same direction. These two types of feedback control are called negative feedback and positive feedback, respectively.

reproductive physiology

explores how the regulation of reproductive hormones can drive the reproductive cycle and influence sex cell production and maturation

Radiographic anatomy

investigates the relationships among internal structures that may be visualized by specific scanning procedures, such as sonography, magnetic resonance imaging (MRI), or x-ray. (See Clinical View: "Medical Imaging" at the end of this chapter.)

The organ level

is composed of organs, which contain two or more tissue types that work together to perform specific, complex functions. The small intestine is an example of an organ that is composed of all four tissue types, which work together to process and absorb digested nutrients.

The chemical level

is the simplest level, and it involves atoms and molecules. Atoms are the smallest units of matter that exhibit the characteristics of an element, such as carbon and hydrogen. When two or more atoms combine they form a molecule. Examples of molecules include a sugar, a water molecule, or a vitamin. More complex molecules are called macromolecules and include some proteins and the deoxyribonucleic acid (DNA) molecules. Macromolecules form specialized microscopic subunits in cells called organelles, which are microscopic structures found within cells.

Posterior Aspect

posterior aspect contains cavities that are completely encased in bone and are physically and developmentally different from the ventral cavity. The term dorsal body cavity has been used by others to describe this posterior aspect, but is not used here because of these differences between the ventral cavity and posterior aspect. • cranial cavity is formed by the bones of the cranium, aka endocranium, houses the brain • vertebral canal, which is formed by the bones of the vertebral column, houses the spinal cord.

Abdominopelvic quadrants

using the umbilicus as the central point and having imaginary transverse and midsagittal planes pass through the umbilicus, partition the abdomen more simply into four quadrants: • right upper quadrant (RUQ), • left upper quadrant (LUQ), • right lower quadrant (RLQ), and • left lower quadrant (LLQ). These quadrants, like the abdominopelvic regions, are used to accurately locate and describe various aches, pains, injuries, or other abnormalities.

Lumbar regions

• The right and left lumbar regions are lateral to the umbilical region.

Ventral Cavity

• The ventral cavity is the larger, • anteriorly placed cavity in the body • the ventral cavity and its subdivisions do not completely encase their organs in bone, but lined with thin serous membranes. • partitioned by the diaphragm into: o a superior thoracic cavity o an inferior abdominopelvic cavity.