Surface Anatomy

Surface Anatomy 13 398 Chapter Thirteen Surface Anatomy I magine this scenario: An unconscious patient has been brought to the emergency room. Although the patient cannot tell the ER physician what is wrong or “where it hurts,” the doctor can assess some of the injuries by observing surface anatomy, including: ■ Locating pulse points to determine the patient’s heart rate and pulse strength ■ Palpating the bones under the skin to determine if a fracture has occurred ■ Passively moving the limbs to observe potential damage to muscles and tendons ■ Examining skeletal and muscular landmarks to discover whether joints are dislocated Examination of surface anatomy must often substitute for interviewing the patient, and when the health-care professional is a keen observer, it may be very accurate in assessing illness or injury. 13.1 A Regional Approach to Surface Anatomy Learning Objectives: 1. 2. Explain the importance of surface anatomy in learning about internal structures. Discuss how surface anatomy studies help us diagnose and treat disease. Surface anatomy is a branch of gross anatomy that exam ines shapes and markings on the surface of the body as they relate to deeper structures. An understanding of surface anatomy is essential for locating and identifying anatomic structures prior to studying internal gross anatomy. Health-care personnel use surface anatomy to help diagnose medical conditions and to treat patients, as when taking a pulse, inserting a needle or tube, or performing physical therapy. You have already begun your study of surface anatomy; each time we have asked you to palpate a part of your body and feel for a structure, you have examined your own surface anatomy. Cranial Frontal Temporal Occipital Nuchal (posterior neck) Auricular Orbital Nasal Health-care professionals rely on four techniques when examining surface anatomy. Using visual inspection, they directly observe the structure and markings of surface features. Through palpation (pal-pā   shŭ n) (feeling with firm pressure or perceiving by the sense of touch), they precisely locate and identify anatomic features under the skin. Using percussion (per-kŭsh  ́ŭn), they tap firmly on specific body sites to detect resonating vibrations. And via auscultation (aws-kŭl-tā   shŭn), they listen to sounds emitted from organs. In our discussion of surface anatomy in this chapter, the illustrations include some structures that we have discussed previ ously and other features yet to be discussed. We strongly suggest that you return to this chapter often as you explore and examine other body systems in subsequent chapters. In addition, before you begin, refer back to chapter 1 and review the discussion of body region names and abdominopelvic regions and quadrants. Study Tip! When preparing for an anatomy exam, your best study aid is your own body. Palpating surface anatomy features on yourself will help you recall these features on an exam and, more importantly, give you a richer understanding of human anatomy. 13.2 Head Region Learning Objective: 1. Identify the surface features of the cranial and facial regions. The head is the most complex and highly integrated region of the body because it houses the brain, which communicates with and controls all of the body systems. The head is structur ally and developmentally divided into the cranium and the face. Figure 13.1 shows the regions and many of the surface anatomy structures of the head and neck. Superciliary arch (with eyebrow) Superior palpebra Auricle External acoustic meatus Zygomatic arch Facial Oral Buccal Mental Buccal region Inferior palpebra Philtrum Frontal region Bridge of nose Dorsum nasi Apex of nose Ala nasi Nostril Lips (labia) Sternoclavicular joint (a) Lateral view Figure 13.1 Neck (cervical) Thyroid cartilage of larynx Clavicle Suprasternal notch Mental region Thyroid cartilage of larynx (b) Anterior view Head and Neck. The major regions of the head and neck are shown in (a) lateral view, while specific features are shown in (b) anterior view. Chapter Thirteen Surface Anatomy 399 13.2a Cranium The cranium (also called the cranial region or braincase) is cov ered by the scalp, which is composed of skin and subcutaneous tissue. The cranium can be subdivided into three regions, each having prominent surface anatomy features. The frontal region of the cranium is the forehead. Covering this region is the frontal belly of the occipitofronta lis muscle. The frontal region terminates at the superciliary arches. You can feel these bony elevations immediately inferior to your eyebrows. Laterally, the scalp covers the sides of the skull in each tem poral region and terminates just superior to the ear. The tempora lis muscle is attached at the temporal region, and is easily palpable when the jaw is repeatedly clenched. Running over the temporalis muscle is the superficial temporal artery. You can feel the pulse of this artery just posterior to the orbits and anterior to the auricle of your ear. The posterior part of the cranium is the occipital (ok-sip  ́ i-tăl) region. In the center of that region is the external occipital protu berance, a rounded or pointed projection (see figures 7.5, 7.8). In chapter 7, you learned that males tend to have a more prominent, pointed external occipital protuberance than females. Palpate your own external occipital protuberance. Is it small and rounded, or somewhat larger and pointed? WHAT DO YOU THINK? ● 1 Can you name some other facial muscles not already mentioned in this chapter that can be palpated easily under the skin? 13.2b Face The face is divided into five regions: auricular, orbital, nasal, oral, and mental. The auricular (aw-rik  ́ū -lăr; auris = ear) region is composed of the visible surface structures of the ear as well as the ear’s internal organs, which function in hearing and maintaining equi librium. The auricle (aw  ́ ri-kl), or pinna, is the fleshy part of the external ear. Within the auricle is a tubular opening called the external acoustic meatus. The mastoid process is posterior and inferior to the auricle. Palpate your mastoid process; it should feel like a bony bump immediately posteroinferior to the ear. The orbital (or ocular) region includes the eyes and associated structures. Most orbital region surface features pro tect the eye. Eyebrows protect against sunlight and potential mechanical damage to the eyes; eyelids (palpebrae; pal  ́pē -brē ) close reflexively to protect against objects moving near the eye; and eyelashes prevent airborne particles from contacting the eyeball. The superior palpebral fissure, or upper eyelid crease, is palpated easily on most individuals, although Asians do not have a superior palpebral fissure. The nasal region contains the nose. The firm, narrow part of the nose that projects anteriorly between the eyes is the bridge; it is formed by the union of the nasal bones. Anteroinferior to the bridge is the fleshy part of the nose, called the dorsum nasi (nā   zē ; nasus = nose). Farther anteroinferiorly is the tip of the nose, called the apex. The nostrils, or external nares (nā   res; sing., naris, na  ́ris), are the paired openings into the nose. The ala nasi (wing of the nose) forms the flared posterolateral margin of each nostril. The oral region is inferior to the nasal region; it includes the buccal (cheek) region, the fleshy upper and lower lips (labia), and the structures of the oral cavity (mouth) that can be observed CLINICAL VIEW Lip Color as a Diagnostic Tool Lip color is the collective result of a combination of pigments that contribute to a person’s skin color, most notably melanin, hemoglobin, and carotene. The pigment melanin has two subtypes: Eumelanin is black, and pheomelanin is typically slightly yellow in low concentrations but slightly reddish in high concentrations. The ratio of these types of melanin determines the skin and lip color. Hemoglobin, an oxygen-binding protein in red blood cells, contributes a red or pink hue. Carotene, a yellow-orange pigment found in carrots, sweet potatoes, and squash, contributes those hues to the skin and lips. Variations in lip color result from the combinations and amounts of these pigments. However, lip color is also affected by our environ ment and state of health. For example, cold weather causes our lips to appear “blue” because blood (and its reddish-colored hemoglobin) is being shunted away from the superficial lips and toward deeper body structures in order to conserve heat. Low body temperature for other reasons, as well as several health conditions, also cause “blue lips.” For instance, a patient who has anemia, pneumonia, emphysema, or certain disorders of the cardiovascular system could exhibit blueness or discoloration of the lips. when the mouth is open. Look in the mirror and observe the verti cal depression between your nose and upper lip; this is called the philtrum (fil  ́ trŭm; philtron = a love charm). The buccal (bŭk  ́al) region refers to the cheek. Within this region is the buccinator muscle. Palpate the superolateral region of your cheek and locate your zygomatic bone and the zygomatic arch. Finally, continuing in the inferior direction, look in the mir ror and observe the mental region, which contains the mentum, or chin. Usually, the mentum tends to be pointed and almost triangular in females, while males tend to have a “squared-off” mentum. W WHAT DID YOU LEARN? ● 1 Identify at least two surface features of the orbital region that protect the eye. ● 2 Identify the narrow, bony, superior part of the nasal region between the eyes. 13.3 Neck Region Learning Objectives: 1. Outline the palpable structures in the regions of the neck. 2. Name the triangles of the neck, and identify the structures they contain. The neck, also called the cervical region or cervix (ser  ́ viks), is a complex region that connects the head to the trunk. The spi nal cord, nerves, trachea, esophagus, and major vessels traverse this highly flexible area. In addition, the neck contains the larynx (voice box) and several important glands. For purposes of dis cussion, the neck can be subdivided into anterior, posterior, and lateral regions. 400 Chapter Thirteen Surface Anatomy Figure 13.2 Anterior and Posterior Triangles of the Neck. The sternocleidomastoid muscle is the landmark for separating the anterior and posterior triangles. These triangles are further subdivided as shown. Anterior triangle Submental Submandibular Carotid Muscular Posterior triangle Occipital Supraclavicular Sternocleidomastoid muscle Occipital Posterior triangle Supraclavicular The anterior region of the neck has several palpable land marks, including the larynx, trachea, and sternal notch. The larynx (lar   ́ ingks; voice box), found in the middle of the anterior neck, is composed of multiple cartilages. Its largest cartilage is the thyroid cartilage, which you can palpate as the big bulge on the anterior side of your neck. In males, the larynx has a noticeably pointed laryngeal prominence (commonly known as the “Adam’s apple”) that may be visualized more easily than in females. Inferior to the larynx are the cricoid cartilage and trachea (air tube). The neck terminates at the suprasternal notch of the manu brium and the left and right clavicles. Palpate your anterior neck region: Moving inferiorly along the neck, you first feel the promi nent thyroid cartilage, then the trachea with its hard, cartilaginous rings, and eventually the suprasternal notch and the clavicles. Submental Submandibular Carotid Muscular Anterior triangle neck and partially bounded by the anterior belly of the digastric muscle. It contains some cervical lymph nodes and tiny veins. When you are ill, these lymph nodes (as well as some glands) may enlarge and become tender. A physician palpates these to deter mine if you have an infection that has been detected by immune cells within these nodes. The submandibular triangle is inferior to the mandible and posterolateral to the submental triangle. It is bounded by the mandible and the bellies of the digastric muscle. If you palpate this triangle, you can feel the submandibular gland, which is the bulge inferior to the mandible. The posterior neck region is also referred to as the nuchal region (see figure 13.1a). This region houses the spinal cord, cervi cal vertebrae, and associated structures. You can easily palpate the spinous process of the vertebra prominens (C7), especially during neck flexion. Palpate your nuchal region; the bump you feel at the inferior boundary of this region is the vertebra prominens. As you move your fingers superiorly along the midline of the neck, you can palpate the ligamentum nuchae, a thick ligament that extends from C7 to the nuchal lines of the skull. The left and right lateral portions of the neck contain the sternocleidomastoid muscles, which become prominent when a person turns his or her head to one side. Each sternocleidomas toid muscle partitions each side of the neck into two clinically important triangles, an anterior triangle and a posterior triangle (figure 13.2). Each of these triangles houses important struc tures that extend through the neck, and these triangles are fur ther subdivided into smaller triangles. The anterior triangle lies anterior to the sternocleidomas toid muscle and inferior to the mandible. It is subdivided into four smaller triangles: the submental, submandibular, carotid, and muscular triangles. The submental triangle, the most superiorly placed of the four triangles, is posteroinferior to the chin in the midline of the The carotid (kă-rŏ t  ́ id) triangle is bounded by the sterno cleidomastoid, omohyoid, and posterior digastric muscles. Palpate this triangle until you feel the strong pulsation of an artery; that is the common carotid artery. This triangle also contains the inter nal jugular vein and some cervical lymph nodes, which may be easily palpated here as well. The muscular triangle is the most inferior of the four tri angles. It contains the sternohyoid and sternothyroid muscles, as well as the lateral edges of the larynx and the thyroid gland. Try to palpate the thyroid gland here. Also in this triangle are cervical lymph nodes. (Cervical lymph nodes are present throughout the neck, as we have indicated.) The posterior triangle is in the lateral region of the neck, posterior to the sternocleidomastoid muscle, superior to the clavicle inferiorly, and anterior to the trapezius muscle. This triangle is subdivided into two smaller triangles: the occipital and supracla vicular triangles. The occipital triangle is the larger and more posteriorly placed of the two triangles. It is bounded by the omohyoid, trapezius, and sternocleidomastoid muscles. This important tri angle contains the external jugular vein (which may be visible internal to the skin), the accessory nerve, the brachial plexus (a mass of nerves that innervates the upper limbs), and some lymph nodes. The supraclavicular (soo-pră-kla-vik  ́ū -lăr) triangle also goes by the names omoclavicular and subclavian. It is bounded