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Anatomy_Gray_0	Anatomy_Gray	What is anatomy? Anatomy includes those structures that can be seen grossly (without the aid of magnification) and microscopically (with the aid of magnification). Typically, when used by itself, the term anatomy tends to mean gross or macroscopic anatomy—that is, the study of structures that can be seen without using ...	Anatomy_Gray. What is anatomy? Anatomy includes those structures that can be seen grossly (without the aid of magnification) and microscopically (with the aid of magnification). Typically, when used by itself, the term anatomy tends to mean gross or macroscopic anatomy—that is, the study of structures that can be seen ...
Anatomy_Gray_1	Anatomy_Gray	Observation and visualization are the primary techniques a student should use to learn anatomy. Anatomy is much more than just memorization of lists of names. Although the language of anatomy is important, the network of information needed to visualize the position of physical structures in a patient goes far beyond si...	Anatomy_Gray. Observation and visualization are the primary techniques a student should use to learn anatomy. Anatomy is much more than just memorization of lists of names. Although the language of anatomy is important, the network of information needed to visualize the position of physical structures in a patient goes...
Anatomy_Gray_2	Anatomy_Gray	How can gross anatomy be studied? The term anatomy is derived from the Greek word temnein, meaning “to cut.” Clearly, therefore, the study of anatomy is linked, at its root, to dissection, although dissection of cadavers by students is now augmented, or even in some cases replaced, by viewing prosected (previously diss...	Anatomy_Gray. How can gross anatomy be studied? The term anatomy is derived from the Greek word temnein, meaning “to cut.” Clearly, therefore, the study of anatomy is linked, at its root, to dissection, although dissection of cadavers by students is now augmented, or even in some cases replaced, by viewing prosected (p...
Anatomy_Gray_3	Anatomy_Gray	This includes the vasculature, the nerves, the bones, the muscles, and all other structures and organs located in the region of the body defined as the thorax. After studying this region, the other regions of the body (i.e., the abdomen, pelvis, lower limb, upper limb, back, head, and neck) are studied in a similar fas...	Anatomy_Gray. This includes the vasculature, the nerves, the bones, the muscles, and all other structures and organs located in the region of the body defined as the thorax. After studying this region, the other regions of the body (i.e., the abdomen, pelvis, lower limb, upper limb, back, head, and neck) are studied in...
Anatomy_Gray_4	Anatomy_Gray	Each of these approaches has benefits and deficiencies. The regional approach works very well if the anatomy course involves cadaver dissection but falls short when it comes to understanding the continuity of an entire system throughout the body. Similarly, the systemic approach fosters an understanding of an entire sy...	Anatomy_Gray. Each of these approaches has benefits and deficiencies. The regional approach works very well if the anatomy course involves cadaver dissection but falls short when it comes to understanding the continuity of an entire system throughout the body. Similarly, the systemic approach fosters an understanding o...
Anatomy_Gray_5	Anatomy_Gray	The anatomical position The anatomical position is the standard reference position of the body used to describe the location of structures (Fig. 1.1). The body is in the anatomical position when standing upright with feet together, hands by the side and face looking forward. The mouth is closed and the facial expressio...	Anatomy_Gray. The anatomical position The anatomical position is the standard reference position of the body used to describe the location of structures (Fig. 1.1). The body is in the anatomical position when standing upright with feet together, hands by the side and face looking forward. The mouth is closed and the fa...
Anatomy_Gray_6	Anatomy_Gray	Three major groups of planes pass through the body in the anatomical position (Fig. 1.1). Coronal planes are oriented vertically and divide the body into anterior and posterior parts. Sagittal planes also are oriented vertically but are at right angles to the coronal planes and divide the body into right and left parts...	Anatomy_Gray. Three major groups of planes pass through the body in the anatomical position (Fig. 1.1). Coronal planes are oriented vertically and divide the body into anterior and posterior parts. Sagittal planes also are oriented vertically but are at right angles to the coronal planes and divide the body into right ...
Anatomy_Gray_7	Anatomy_Gray	Three major pairs of terms are used to describe the location of structures relative to the body as a whole or to other structures (Fig. 1.1). Anterior (or ventral) and posterior (or dorsal) describe the position of structures relative to the “front” and “back” of the body. For example, the nose is an anterior (ventral)...	Anatomy_Gray. Three major pairs of terms are used to describe the location of structures relative to the body as a whole or to other structures (Fig. 1.1). Anterior (or ventral) and posterior (or dorsal) describe the position of structures relative to the “front” and “back” of the body. For example, the nose is an ante...
Anatomy_Gray_8	Anatomy_Gray	Superior and inferior describe structures in reference to the vertical axis of the body. For example, the head is superior to the shoulders and the knee joint is inferior to the hip joint. Proximal and distal, cranial and caudal, Other terms used to describe positions include proximal and distal, cranial and caudal, an...	Anatomy_Gray. Superior and inferior describe structures in reference to the vertical axis of the body. For example, the head is superior to the shoulders and the knee joint is inferior to the hip joint. Proximal and distal, cranial and caudal, Other terms used to describe positions include proximal and distal, cranial ...
Anatomy_Gray_9	Anatomy_Gray	Cranial (toward the head) and caudal (toward the tail) are sometimes used instead of superior and inferior, respectively. Rostral is used, particularly in the head, to describe the position of a structure with reference to the nose. For example, the forebrain is rostral to the hindbrain. Two other terms used to describ...	Anatomy_Gray. Cranial (toward the head) and caudal (toward the tail) are sometimes used instead of superior and inferior, respectively. Rostral is used, particularly in the head, to describe the position of a structure with reference to the nose. For example, the forebrain is rostral to the hindbrain. Two other terms u...
Anatomy_Gray_10	Anatomy_Gray	Superficial and deep can also be used in a more absolute fashion to define two major regions of the body. The superficial region of the body is external to the outer layer of deep fascia. Deep structures are enclosed by this layer. Structures in the superficial region of the body include the skin, superficial fascia, a...	Anatomy_Gray. Superficial and deep can also be used in a more absolute fashion to define two major regions of the body. The superficial region of the body is external to the outer layer of deep fascia. Deep structures are enclosed by this layer. Structures in the superficial region of the body include the skin, superfi...
Anatomy_Gray_11	Anatomy_Gray	X-rays are photons (a type of electromagnetic radiation) and are generated from a complex X-ray tube, which is a type of cathode ray tube (Fig. 1.2). The X-rays are then collimated (i.e., directed through lead-lined shutters to stop them from fanning out) to the appropriate area of the body. As the X-rays pass through ...	Anatomy_Gray. X-rays are photons (a type of electromagnetic radiation) and are generated from a complex X-ray tube, which is a type of cathode ray tube (Fig. 1.2). The X-rays are then collimated (i.e., directed through lead-lined shutters to stop them from fanning out) to the appropriate area of the body. As the X-rays...
Anatomy_Gray_12	Anatomy_Gray	Modifications to this X-ray technique allow a continuous stream of X-rays to be produced from the X-ray tube and collected on an input screen to allow real-time visualization of moving anatomical structures, barium studies, angiography, and fluoroscopy (Fig. 1.3).	Anatomy_Gray. Modifications to this X-ray technique allow a continuous stream of X-rays to be produced from the X-ray tube and collected on an input screen to allow real-time visualization of moving anatomical structures, barium studies, angiography, and fluoroscopy (Fig. 1.3).
Anatomy_Gray_13	Anatomy_Gray	To demonstrate specific structures, such as bowel loops or arteries, it may be necessary to fill these structures with a substance that attenuates X-rays more than bowel loops or arteries do normally. It is, however, extremely important that these substances are nontoxic. Barium sulfate, an insoluble salt, is a nontoxi...	Anatomy_Gray. To demonstrate specific structures, such as bowel loops or arteries, it may be necessary to fill these structures with a substance that attenuates X-rays more than bowel loops or arteries do normally. It is, however, extremely important that these substances are nontoxic. Barium sulfate, an insoluble salt...
Anatomy_Gray_14	Anatomy_Gray	For some patients it is necessary to inject contrast agents directly into arteries or veins. In this case, iodine-based molecules are suitable contrast agents. Iodine is chosen because it has a relatively high atomic mass and so markedly attenuates X-rays, but also, importantly, it is naturally excreted via the urinary...	Anatomy_Gray. For some patients it is necessary to inject contrast agents directly into arteries or veins. In this case, iodine-based molecules are suitable contrast agents. Iodine is chosen because it has a relatively high atomic mass and so markedly attenuates X-rays, but also, importantly, it is naturally excreted v...
Anatomy_Gray_15	Anatomy_Gray	During angiography it is often difficult to appreciate the contrast agent in the vessels through the overlying bony structures. To circumvent this, the technique of subtraction angiography has been developed. Simply, one or two images are obtained before the injection of contrast media. These images are inverted (such ...	Anatomy_Gray. During angiography it is often difficult to appreciate the contrast agent in the vessels through the overlying bony structures. To circumvent this, the technique of subtraction angiography has been developed. Simply, one or two images are obtained before the injection of contrast media. These images are i...
Anatomy_Gray_16	Anatomy_Gray	Ultrasonography of the body is widely used for all aspects of medicine. Ultrasound is a very high frequency sound wave (not electromagnetic radiation) generated by piezoelectric materials, such that a series of sound waves is produced. Importantly, the piezoelectric material can also receive the sound waves that bounce...	Anatomy_Gray. Ultrasonography of the body is widely used for all aspects of medicine. Ultrasound is a very high frequency sound wave (not electromagnetic radiation) generated by piezoelectric materials, such that a series of sound waves is produced. Importantly, the piezoelectric material can also receive the sound wav...
Anatomy_Gray_17	Anatomy_Gray	Developments in ultrasound technology, including the size of the probes and the frequency range, mean that a broad range of areas can now be scanned. Traditionally ultrasound is used for assessing the abdomen (Fig. 1.6) and the fetus in pregnant women. Ultrasound is also widely used to assess the eyes, neck, soft tissu...	Anatomy_Gray. Developments in ultrasound technology, including the size of the probes and the frequency range, mean that a broad range of areas can now be scanned. Traditionally ultrasound is used for assessing the abdomen (Fig. 1.6) and the fetus in pregnant women. Ultrasound is also widely used to assess the eyes, ne...
Anatomy_Gray_18	Anatomy_Gray	Doppler ultrasound enables determination of flow, its direction, and its velocity within a vessel using simple ultrasound techniques. Sound waves bounce off moving structures and are returned. The degree of frequency shift determines whether the object is moving away from or toward the probe and the speed at which it i...	Anatomy_Gray. Doppler ultrasound enables determination of flow, its direction, and its velocity within a vessel using simple ultrasound techniques. Sound waves bounce off moving structures and are returned. The degree of frequency shift determines whether the object is moving away from or toward the probe and the speed...
Anatomy_Gray_19	Anatomy_Gray	A CT scanner obtains a series of images of the body (slices) in the axial plane. The patient lies on a bed, an X-ray tube passes around the body (Fig. 1.7), and a series of images are obtained. A computer carries out a complex mathematical transformation on the multitude of images to produce the final image (Fig. 1.8).	Anatomy_Gray. A CT scanner obtains a series of images of the body (slices) in the axial plane. The patient lies on a bed, an X-ray tube passes around the body (Fig. 1.7), and a series of images are obtained. A computer carries out a complex mathematical transformation on the multitude of images to produce the final ima...
Anatomy_Gray_20	Anatomy_Gray	Nuclear magnetic resonance imaging was first described in 1946 and used to determine the structure of complex molecules. The process of magnetic resonance imaging (MRI) is dependent on the free protons in the hydrogen nuclei in molecules of water (H2O). Because water is present in almost all biological tissues, the hyd...	Anatomy_Gray. Nuclear magnetic resonance imaging was first described in 1946 and used to determine the structure of complex molecules. The process of magnetic resonance imaging (MRI) is dependent on the free protons in the hydrogen nuclei in molecules of water (H2O). Because water is present in almost all biological ti...
Anatomy_Gray_21	Anatomy_Gray	By altering the sequence of pulses to which the protons are subjected, different properties of the protons can be assessed. These properties are referred to as the “weighting” of the scan. By altering the pulse sequence and the scanning parameters, T1-weighted images (Fig. 1.10A) and T2-weighted images (Fig. 1.10B) can...	Anatomy_Gray. By altering the sequence of pulses to which the protons are subjected, different properties of the protons can be assessed. These properties are referred to as the “weighting” of the scan. By altering the pulse sequence and the scanning parameters, T1-weighted images (Fig. 1.10A) and T2-weighted images (F...
Anatomy_Gray_22	Anatomy_Gray	MRI can also be used to assess flow within vessels and to produce complex angiograms of the peripheral and cerebral circulation. Diffusion-weighted imaging provides information on the degree of Brownian motion of water molecules in various tissues. There is relatively free diffusion in extracellular spaces and more res...	Anatomy_Gray. MRI can also be used to assess flow within vessels and to produce complex angiograms of the peripheral and cerebral circulation. Diffusion-weighted imaging provides information on the degree of Brownian motion of water molecules in various tissues. There is relatively free diffusion in extracellular space...
Anatomy_Gray_23	Anatomy_Gray	X-rays is that gamma rays are produced from within the nucleus of an atom when an unstable nucleus decays, whereas X-rays are produced by bombarding an atom with electrons. For an area to be visualized, the patient must receive a gamma ray emitter, which must have a number of properties to be useful, including: a reaso...	Anatomy_Gray. X-rays is that gamma rays are produced from within the nucleus of an atom when an unstable nucleus decays, whereas X-rays are produced by bombarding an atom with electrons. For an area to be visualized, the patient must receive a gamma ray emitter, which must have a number of properties to be useful, incl...
Anatomy_Gray_24	Anatomy_Gray	The most commonly used radionuclide (radioisotope) is technetium-99m. This may be injected as a technetium salt or combined with other complex molecules. For example, by combining technetium-99m with methylene diphosphonate (MDP), a radiopharmaceutical is produced. When injected into the body this radiopharmaceutical s...	Anatomy_Gray. The most commonly used radionuclide (radioisotope) is technetium-99m. This may be injected as a technetium salt or combined with other complex molecules. For example, by combining technetium-99m with methylene diphosphonate (MDP), a radiopharmaceutical is produced. When injected into the body this radioph...
Anatomy_Gray_25	Anatomy_Gray	Depending on how the radiopharmaceutical is absorbed, distributed, metabolized, and excreted by the body after injection, images are obtained using a gamma camera (Fig. 1.11). Positron emission tomography (PET) is an imaging modality for detecting positron-emitting radionuclides. A positron is an anti-electron, which i...	Anatomy_Gray. Depending on how the radiopharmaceutical is absorbed, distributed, metabolized, and excreted by the body after injection, images are obtained using a gamma camera (Fig. 1.11). Positron emission tomography (PET) is an imaging modality for detecting positron-emitting radionuclides. A positron is an anti-ele...
Anatomy_Gray_26	Anatomy_Gray	PET has become an important imaging modality in the detection of cancer and the assessment of its treatment and recurrence. Single photon emission computed tomography (SPECT) is an imaging modality for detecting gamma rays emitted from the decay of injected radionuclides such as technetium-99m, iodine-123, or iodine-13...	Anatomy_Gray. PET has become an important imaging modality in the detection of cancer and the assessment of its treatment and recurrence. Single photon emission computed tomography (SPECT) is an imaging modality for detecting gamma rays emitted from the decay of injected radionuclides such as technetium-99m, iodine-123...
Anatomy_Gray_27	Anatomy_Gray	Plain radiographs are undoubtedly the most common form of image obtained in a hospital or local practice. Before interpretation, it is important to know about the imaging technique and the views obtained as standard. In most instances (apart from chest radiography) the X-ray tube is 1 m away from the X-ray film. The ob...	Anatomy_Gray. Plain radiographs are undoubtedly the most common form of image obtained in a hospital or local practice. Before interpretation, it is important to know about the imaging technique and the views obtained as standard. In most instances (apart from chest radiography) the X-ray tube is 1 m away from the X-ra...
Anatomy_Gray_28	Anatomy_Gray	The chest radiograph is one of the most commonly requested plain radiographs. An image is taken with the patient erect and placed posteroanteriorly (PA chest radiograph; that is, with the patient’s back closest to the X-ray tube.). Occasionally, when patients are too unwell to stand erect, films are obtained on the bed...	Anatomy_Gray. The chest radiograph is one of the most commonly requested plain radiographs. An image is taken with the patient erect and placed posteroanteriorly (PA chest radiograph; that is, with the patient’s back closest to the X-ray tube.). Occasionally, when patients are too unwell to stand erect, films are obtai...
Anatomy_Gray_29	Anatomy_Gray	Plain abdominal radiographs are obtained in the AP supine position. From time to time an erect plain abdominal radiograph is obtained when small bowel obstruction is suspected.	Anatomy_Gray. Plain abdominal radiographs are obtained in the AP supine position. From time to time an erect plain abdominal radiograph is obtained when small bowel obstruction is suspected.
Anatomy_Gray_30	Anatomy_Gray	High-density contrast medium is ingested to opacify the esophagus, stomach, small bowel, and large bowel. As described previously (p. 6), the bowel is insufflated with air (or carbon dioxide) to provide a double-contrast study. In many countries, endoscopy has superseded upper gastrointestinal imaging, but the mainstay...	Anatomy_Gray. High-density contrast medium is ingested to opacify the esophagus, stomach, small bowel, and large bowel. As described previously (p. 6), the bowel is insufflated with air (or carbon dioxide) to provide a double-contrast study. In many countries, endoscopy has superseded upper gastrointestinal imaging, bu...
Anatomy_Gray_31	Anatomy_Gray	Intravenous urography is the standard investigation for assessing the urinary tract. Intravenous contrast medium is injected, and images are obtained as the medium is excreted through the kidneys. A series of films are obtained during this period from immediately after the injection up to approximately 20 minutes later...	Anatomy_Gray. Intravenous urography is the standard investigation for assessing the urinary tract. Intravenous contrast medium is injected, and images are obtained as the medium is excreted through the kidneys. A series of films are obtained during this period from immediately after the injection up to approximately 20...
Anatomy_Gray_32	Anatomy_Gray	Computed tomography is the preferred terminology rather than computerized tomography, though both terms are used interchangeably by physicians. It is important for the student to understand the presentation of images. Most images are acquired in the axial plane and viewed such that the observer looks from below and upw...	Anatomy_Gray. Computed tomography is the preferred terminology rather than computerized tomography, though both terms are used interchangeably by physicians. It is important for the student to understand the presentation of images. Most images are acquired in the axial plane and viewed such that the observer looks from...
Anatomy_Gray_33	Anatomy_Gray	The great advantage of CT scanning is the ability to extend and compress the gray scale to visualize the bones, soft tissues, and visceral organs. Altering the window settings and window centering provides the physician with specific information about these structures. There is no doubt that MRI has revolutionized the ...	Anatomy_Gray. The great advantage of CT scanning is the ability to extend and compress the gray scale to visualize the bones, soft tissues, and visceral organs. Altering the window settings and window centering provides the physician with specific information about these structures. There is no doubt that MRI has revol...
Anatomy_Gray_34	Anatomy_Gray	Most nuclear medicine images are functional studies. Images are usually interpreted directly from a computer, and a series of representative films are obtained for clinical use. Whenever a patient undergoes an X-ray or nuclear medicine investigation, a dose of radiation is given (Table 1.1). As a general principle it i...	Anatomy_Gray. Most nuclear medicine images are functional studies. Images are usually interpreted directly from a computer, and a series of representative films are obtained for clinical use. Whenever a patient undergoes an X-ray or nuclear medicine investigation, a dose of radiation is given (Table 1.1). As a general ...
Anatomy_Gray_35	Anatomy_Gray	Imaging modalities such as ultrasound and MRI are ideal because they do not impart significant risk to the patient. Moreover, ultrasound imaging is the modality of choice for assessing the fetus. Any imaging device is expensive, and consequently the more complex the imaging technique (e.g., MRI) the more expensive the ...	Anatomy_Gray. Imaging modalities such as ultrasound and MRI are ideal because they do not impart significant risk to the patient. Moreover, ultrasound imaging is the modality of choice for assessing the fetus. Any imaging device is expensive, and consequently the more complex the imaging technique (e.g., MRI) the more ...
Anatomy_Gray_36	Anatomy_Gray	The skeletal system consists of cartilage and bone. Cartilage is an avascular form of connective tissue consisting of extracellular fibers embedded in a matrix that contains cells localized in small cavities. The amount and kind of extracellular fibers in the matrix varies depending on the type of cartilage. In heavy w...	Anatomy_Gray. The skeletal system consists of cartilage and bone. Cartilage is an avascular form of connective tissue consisting of extracellular fibers embedded in a matrix that contains cells localized in small cavities. The amount and kind of extracellular fibers in the matrix varies depending on the type of cartila...
Anatomy_Gray_37	Anatomy_Gray	There are three types of cartilage: hyaline—most common; matrix contains a moderate amount of collagen fibers (e.g., articular surfaces of bones); elastic—matrix contains collagen fibers along with a large number of elastic fibers (e.g., external ear); fibrocartilage—matrix contains a limited number of cells and ground...	Anatomy_Gray. There are three types of cartilage: hyaline—most common; matrix contains a moderate amount of collagen fibers (e.g., articular surfaces of bones); elastic—matrix contains collagen fibers along with a large number of elastic fibers (e.g., external ear); fibrocartilage—matrix contains a limited number of ce...
Anatomy_Gray_38	Anatomy_Gray	There are two types of bone, compact and spongy (trabecular or cancellous). Compact bone is dense bone that forms the outer shell of all bones and surrounds spongy bone. Spongy bone consists of spicules of bone enclosing cavities containing blood-forming cells (marrow). Classification of bones is by shape. Long bones a...	Anatomy_Gray. There are two types of bone, compact and spongy (trabecular or cancellous). Compact bone is dense bone that forms the outer shell of all bones and surrounds spongy bone. Spongy bone consists of spicules of bone enclosing cavities containing blood-forming cells (marrow). Classification of bones is by shape...
Anatomy_Gray_39	Anatomy_Gray	Bones are vascular and are innervated. Generally, an adjacent artery gives off a nutrient artery, usually one per bone, that directly enters the internal cavity of the bone and supplies the marrow, spongy bone, and inner layers of compact bone. In addition, all bones are covered externally, except in the area of a join...	Anatomy_Gray. Bones are vascular and are innervated. Generally, an adjacent artery gives off a nutrient artery, usually one per bone, that directly enters the internal cavity of the bone and supplies the marrow, spongy bone, and inner layers of compact bone. In addition, all bones are covered externally, except in the ...