![\"11.3](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2019\/06\/Human_skulls_on_display-2.jpg\")
11.3.1 Skulls on display.<\/em>[\/caption]\r\n\r\nSkulls on Display<\/h1>\r\n<\/div>\r\nThis somewhat macabre display (Figure 11.3.1) can be viewed at the Slovak National Museum in Bratislava, Slovakia. The [pb_glossary id=\"3957\"]skulls[\/pb_glossary] are meant to represent normal human skeletal anatomy. The skull is part of the [pb_glossary id=\"3953\"]axial skeleton[\/pb_glossary], which is one of the two major divisions of the human skeleton. The other division is the [pb_glossary id=\"3954\"]appendicular skeleton[\/pb_glossary].\r\n\r\nAxial Skeleton<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_3955\" align=\"alignright\" width=\"429\"]![\"11.2](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Axial_skeleton_diagram_blank.svg_-2.png\")
Figure 11.3.2 The axial skeleton.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"3953\"]axial skeleton[\/pb_glossary],<\/strong> shown in blue in Figure 11.3.2, consists of a total of 80 bones. Besides the skull, it includes the rib cage and vertebral column. It also includes the three tiny ossicles (hammer, anvil, and stirrup) in the middle ear and the hyoid bone in the throat, to which the tongue and some other soft tissues are attached.\r\nSkull<\/h2>\r\nThe\u00a0[pb_glossary id=\"3957\"]skull[\/pb_glossary]<\/strong> is the part of the human skeleton that provides a bony framework for the head. It consists of 22 different bones. There are eight bones in the cranium, which encloses the brain, and 14 bones in the face.\r\nCranium<\/h3>\r\nThe\u00a0[pb_glossary id=\"3975\"]cranium[\/pb_glossary]\u00a0<\/strong>forms the entire upper portion of the skull. As shown in Figure 11.3.3, it consists of eight bones: one frontal bone, two parietal bones, two temporal bones, one occipital bone, one sphenoid bone, and one ethmoid bone. The ethmoid bone separates the nasal cavity from the brain. The sphenoid bone is one of several bones, including the frontal bone, that help form the eye sockets. The other bones of the cranium are large and plate-like. They cover and protect the brain. The bottom of the skull has openings for major blood vessels and nerves. A large opening, called the foramen, connects the spinal cord and brain.\r\n\r\n[caption id=\"attachment_3976\" align=\"aligncenter\" width=\"426\"]![\"11.3.3](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/822px-Cranial_bones_en_v2.svg_-2.png\")
Figure 11.3.3 The cranium consists of eight bones that are fused together at their joints.<\/em>[\/caption]\r\nFacial Bones<\/h3>\r\nThe 14 facial bones of the skull are located below the frontal bone of the cranium, and they are depicted in Figure 11.3.4. Large bones in the face include the upper jaw bones, or maxillae (singular, maxilla),<\/strong>\u00a0which form the middle part of the face and the bottom of the two eye sockets. The maxillae are fused together, except for an opening between them for the nose. The lower edge of the maxillae contains sockets for the upper teeth. The lower jaw bone, or\u00a0mandible,<\/strong> is also large. The top edge of the mandible contains sockets for the lower teeth. The mandible opens and closes to chew food and is controlled by strong muscles. There are two zygomatic (or cheek) bones and two nasal bones. The nasal region also contains seven smaller bones, as indicated in Figure 11.3.4.\r\n\r\n[caption id=\"attachment_3978\" align=\"aligncenter\" width=\"548\"]![\"11.3.4](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Facial_skeleton_-_en.svg_-2.png\")
Figure 11.3.4 The 14 bones that make up the face are labeled in this drawing of the skull.<\/em>[\/caption]\r\nVertebral Column<\/h2>\r\n[caption id=\"attachment_4000\" align=\"alignleft\" width=\"313\"]![\"11.3.5](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Spinal_column_curvature-2.png\")
Figure 11.3.5 The vertebral column consists of 24 individual vertebrae that are separated by intervertebral discs of cartilage. An additional nine vertebrae are fused together at the base of the spine. Note the S-shaped curve of the vertebral column in the profile view on the right.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"3958\"]vertebral column[\/pb_glossary]<\/strong>\u00a0\u2014 also called the spine or backbone \u2014 is the flexible column of\u00a0[pb_glossary id=\"3964\"]vertebrae[\/pb_glossary] (singular, vertebra)<\/strong> that connects the trunk with the [pb_glossary id=\"3957\"]skull[\/pb_glossary] and encloses the spinal cord. It consists of 33 vertebrae that are divided into five regions, as shown in Figure 11.3.5: the [pb_glossary id=\"3979\"]cervical[\/pb_glossary], [pb_glossary id=\"5491\"]thoracic[\/pb_glossary], [pb_glossary id=\"3998\"]lumbar[\/pb_glossary], [pb_glossary id=\"3999\"]sacral[\/pb_glossary], and [pb_glossary id=\"6453\"]coccygeal[\/pb_glossary] regions. From the neck down, the first 24 vertebrae (cervical, thoracic, and lumbar) are individual bones. The five sacral vertebrae are fused together, as are the four coccygeal vertebrae.\r\n\r\nThe vertebral column consists of 24 individual vertebrae that are separated by [pb_glossary id=\"4001\"]intervertebral disc[\/pb_glossary]s of cartilage. An additional nine vertebrae are fused together at the base of the spine. Note the S-shaped curve of the vertebral column in the profile view in Figure 11.3.5 on the left.<\/span>\r\n\r\nThe human vertebral column reflects adaptations for upright bipedal locomotion (walking upright on two legs). For example, the vertebral column is less like a rigid column than an S-shaped spring (see profile view in Figure 11.3.5). Although newborn infants have a relatively straight spine, the curves develop as the backbone starts taking on its support functions, such as keeping the trunk erect, holding up the head, and helping to anchor the limbs. The S shape of the vertebral column allows it to act like a shock absorber, absorbing much of the jarring of walking and running so the forces are not transmitted directly from the pelvis to the skull. The S shape also helps protect the spine from breaking, which would be more likely with a straight, more rigid vertebral column. In addition, the S shape helps to distribute the weight of the body \u2014 particularly of the internal organs, so the weight load is not all at the bottom, as would occur with a straight spine.\r\nRib Cage<\/h2>\r\nThe\u00a0[pb_glossary id=\"4002\"]rib cage[\/pb_glossary]<\/strong> (also called thoracic cage) is aptly named, because it forms a sort of cage that holds within it the organs of the upper part of the trunk, including the [pb_glossary id=\"2987\"]heart[\/pb_glossary] and [pb_glossary id=\"2990\"]lungs[\/pb_glossary]. It is shown in Figures 11.3.6\u201311.3.8. The rib cage includes the 12 thoracic vertebrae and the sternum, as well as 12 pairs of ribs, which are attached at joints to the vertebrae. The ribs are divided into three groups, called true ribs, false ribs, and floating ribs. The top seven pairs of ribs are true ribs. They are attached by cartilage directly to the sternum. The next three pairs of ribs are false ribs. They are attached by cartilage to the ribs above them, rather than directly to the sternum. The lowest two pairs of ribs are floating ribs. They are attached by cartilage to muscles in the abdominal wall. The attachments of false and floating ribs let the lower part of the rib cage expand to accommodate the internal movements of breathing.\r\n
Axial Skeleton<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_3955\" align=\"alignright\" width=\"429\"] Figure 11.3.2 The axial skeleton.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"3953\"]axial skeleton[\/pb_glossary],<\/strong> shown in blue in Figure 11.3.2, consists of a total of 80 bones. Besides the skull, it includes the rib cage and vertebral column. It also includes the three tiny ossicles (hammer, anvil, and stirrup) in the middle ear and the hyoid bone in the throat, to which the tongue and some other soft tissues are attached.\r\nSkull<\/h2>\r\nThe\u00a0[pb_glossary id=\"3957\"]skull[\/pb_glossary]<\/strong> is the part of the human skeleton that provides a bony framework for the head. It consists of 22 different bones. There are eight bones in the cranium, which encloses the brain, and 14 bones in the face.\r\nCranium<\/h3>\r\nThe\u00a0[pb_glossary id=\"3975\"]cranium[\/pb_glossary]\u00a0<\/strong>forms the entire upper portion of the skull. As shown in Figure 11.3.3, it consists of eight bones: one frontal bone, two parietal bones, two temporal bones, one occipital bone, one sphenoid bone, and one ethmoid bone. The ethmoid bone separates the nasal cavity from the brain. The sphenoid bone is one of several bones, including the frontal bone, that help form the eye sockets. The other bones of the cranium are large and plate-like. They cover and protect the brain. The bottom of the skull has openings for major blood vessels and nerves. A large opening, called the foramen, connects the spinal cord and brain.\r\n\r\n[caption id=\"attachment_3976\" align=\"aligncenter\" width=\"426\"] Figure 11.3.3 The cranium consists of eight bones that are fused together at their joints.<\/em>[\/caption]\r\nFacial Bones<\/h3>\r\nThe 14 facial bones of the skull are located below the frontal bone of the cranium, and they are depicted in Figure 11.3.4. Large bones in the face include the upper jaw bones, or maxillae (singular, maxilla),<\/strong>\u00a0which form the middle part of the face and the bottom of the two eye sockets. The maxillae are fused together, except for an opening between them for the nose. The lower edge of the maxillae contains sockets for the upper teeth. The lower jaw bone, or\u00a0mandible,<\/strong> is also large. The top edge of the mandible contains sockets for the lower teeth. The mandible opens and closes to chew food and is controlled by strong muscles. There are two zygomatic (or cheek) bones and two nasal bones. The nasal region also contains seven smaller bones, as indicated in Figure 11.3.4.\r\n\r\n[caption id=\"attachment_3978\" align=\"aligncenter\" width=\"548\"] Figure 11.3.4 The 14 bones that make up the face are labeled in this drawing of the skull.<\/em>[\/caption]\r\nVertebral Column<\/h2>\r\n[caption id=\"attachment_4000\" align=\"alignleft\" width=\"313\"] Figure 11.3.5 The vertebral column consists of 24 individual vertebrae that are separated by intervertebral discs of cartilage. An additional nine vertebrae are fused together at the base of the spine. Note the S-shaped curve of the vertebral column in the profile view on the right.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"3958\"]vertebral column[\/pb_glossary]<\/strong>\u00a0\u2014 also called the spine or backbone \u2014 is the flexible column of\u00a0[pb_glossary id=\"3964\"]vertebrae[\/pb_glossary] (singular, vertebra)<\/strong> that connects the trunk with the [pb_glossary id=\"3957\"]skull[\/pb_glossary] and encloses the spinal cord. It consists of 33 vertebrae that are divided into five regions, as shown in Figure 11.3.5: the [pb_glossary id=\"3979\"]cervical[\/pb_glossary], [pb_glossary id=\"5491\"]thoracic[\/pb_glossary], [pb_glossary id=\"3998\"]lumbar[\/pb_glossary], [pb_glossary id=\"3999\"]sacral[\/pb_glossary], and [pb_glossary id=\"6453\"]coccygeal[\/pb_glossary] regions. From the neck down, the first 24 vertebrae (cervical, thoracic, and lumbar) are individual bones. The five sacral vertebrae are fused together, as are the four coccygeal vertebrae.\r\n\r\nThe vertebral column consists of 24 individual vertebrae that are separated by [pb_glossary id=\"4001\"]intervertebral disc[\/pb_glossary]s of cartilage. An additional nine vertebrae are fused together at the base of the spine. Note the S-shaped curve of the vertebral column in the profile view in Figure 11.3.5 on the left.<\/span>\r\n\r\nThe human vertebral column reflects adaptations for upright bipedal locomotion (walking upright on two legs). For example, the vertebral column is less like a rigid column than an S-shaped spring (see profile view in Figure 11.3.5). Although newborn infants have a relatively straight spine, the curves develop as the backbone starts taking on its support functions, such as keeping the trunk erect, holding up the head, and helping to anchor the limbs. The S shape of the vertebral column allows it to act like a shock absorber, absorbing much of the jarring of walking and running so the forces are not transmitted directly from the pelvis to the skull. The S shape also helps protect the spine from breaking, which would be more likely with a straight, more rigid vertebral column. In addition, the S shape helps to distribute the weight of the body \u2014 particularly of the internal organs, so the weight load is not all at the bottom, as would occur with a straight spine.\r\nRib Cage<\/h2>\r\nThe\u00a0[pb_glossary id=\"4002\"]rib cage[\/pb_glossary]<\/strong> (also called thoracic cage) is aptly named, because it forms a sort of cage that holds within it the organs of the upper part of the trunk, including the [pb_glossary id=\"2987\"]heart[\/pb_glossary] and [pb_glossary id=\"2990\"]lungs[\/pb_glossary]. It is shown in Figures 11.3.6\u201311.3.8. The rib cage includes the 12 thoracic vertebrae and the sternum, as well as 12 pairs of ribs, which are attached at joints to the vertebrae. The ribs are divided into three groups, called true ribs, false ribs, and floating ribs. The top seven pairs of ribs are true ribs. They are attached by cartilage directly to the sternum. The next three pairs of ribs are false ribs. They are attached by cartilage to the ribs above them, rather than directly to the sternum. The lowest two pairs of ribs are floating ribs. They are attached by cartilage to muscles in the abdominal wall. The attachments of false and floating ribs let the lower part of the rib cage expand to accommodate the internal movements of breathing.\r\n
Cranium<\/h3>\r\nThe\u00a0[pb_glossary id=\"3975\"]cranium[\/pb_glossary]\u00a0<\/strong>forms the entire upper portion of the skull. As shown in Figure 11.3.3, it consists of eight bones: one frontal bone, two parietal bones, two temporal bones, one occipital bone, one sphenoid bone, and one ethmoid bone. The ethmoid bone separates the nasal cavity from the brain. The sphenoid bone is one of several bones, including the frontal bone, that help form the eye sockets. The other bones of the cranium are large and plate-like. They cover and protect the brain. The bottom of the skull has openings for major blood vessels and nerves. A large opening, called the foramen, connects the spinal cord and brain.\r\n\r\n[caption id=\"attachment_3976\" align=\"aligncenter\" width=\"426\"] Figure 11.3.3 The cranium consists of eight bones that are fused together at their joints.<\/em>[\/caption]\r\nFacial Bones<\/h3>\r\nThe 14 facial bones of the skull are located below the frontal bone of the cranium, and they are depicted in Figure 11.3.4. Large bones in the face include the upper jaw bones, or maxillae (singular, maxilla),<\/strong>\u00a0which form the middle part of the face and the bottom of the two eye sockets. The maxillae are fused together, except for an opening between them for the nose. The lower edge of the maxillae contains sockets for the upper teeth. The lower jaw bone, or\u00a0mandible,<\/strong> is also large. The top edge of the mandible contains sockets for the lower teeth. The mandible opens and closes to chew food and is controlled by strong muscles. There are two zygomatic (or cheek) bones and two nasal bones. The nasal region also contains seven smaller bones, as indicated in Figure 11.3.4.\r\n\r\n[caption id=\"attachment_3978\" align=\"aligncenter\" width=\"548\"] Figure 11.3.4 The 14 bones that make up the face are labeled in this drawing of the skull.<\/em>[\/caption]\r\nVertebral Column<\/h2>\r\n[caption id=\"attachment_4000\" align=\"alignleft\" width=\"313\"] Figure 11.3.5 The vertebral column consists of 24 individual vertebrae that are separated by intervertebral discs of cartilage. An additional nine vertebrae are fused together at the base of the spine. Note the S-shaped curve of the vertebral column in the profile view on the right.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"3958\"]vertebral column[\/pb_glossary]<\/strong>\u00a0\u2014 also called the spine or backbone \u2014 is the flexible column of\u00a0[pb_glossary id=\"3964\"]vertebrae[\/pb_glossary] (singular, vertebra)<\/strong> that connects the trunk with the [pb_glossary id=\"3957\"]skull[\/pb_glossary] and encloses the spinal cord. It consists of 33 vertebrae that are divided into five regions, as shown in Figure 11.3.5: the [pb_glossary id=\"3979\"]cervical[\/pb_glossary], [pb_glossary id=\"5491\"]thoracic[\/pb_glossary], [pb_glossary id=\"3998\"]lumbar[\/pb_glossary], [pb_glossary id=\"3999\"]sacral[\/pb_glossary], and [pb_glossary id=\"6453\"]coccygeal[\/pb_glossary] regions. From the neck down, the first 24 vertebrae (cervical, thoracic, and lumbar) are individual bones. The five sacral vertebrae are fused together, as are the four coccygeal vertebrae.\r\n\r\nThe vertebral column consists of 24 individual vertebrae that are separated by [pb_glossary id=\"4001\"]intervertebral disc[\/pb_glossary]s of cartilage. An additional nine vertebrae are fused together at the base of the spine. Note the S-shaped curve of the vertebral column in the profile view in Figure 11.3.5 on the left.<\/span>\r\n\r\nThe human vertebral column reflects adaptations for upright bipedal locomotion (walking upright on two legs). For example, the vertebral column is less like a rigid column than an S-shaped spring (see profile view in Figure 11.3.5). Although newborn infants have a relatively straight spine, the curves develop as the backbone starts taking on its support functions, such as keeping the trunk erect, holding up the head, and helping to anchor the limbs. The S shape of the vertebral column allows it to act like a shock absorber, absorbing much of the jarring of walking and running so the forces are not transmitted directly from the pelvis to the skull. The S shape also helps protect the spine from breaking, which would be more likely with a straight, more rigid vertebral column. In addition, the S shape helps to distribute the weight of the body \u2014 particularly of the internal organs, so the weight load is not all at the bottom, as would occur with a straight spine.\r\nRib Cage<\/h2>\r\nThe\u00a0[pb_glossary id=\"4002\"]rib cage[\/pb_glossary]<\/strong> (also called thoracic cage) is aptly named, because it forms a sort of cage that holds within it the organs of the upper part of the trunk, including the [pb_glossary id=\"2987\"]heart[\/pb_glossary] and [pb_glossary id=\"2990\"]lungs[\/pb_glossary]. It is shown in Figures 11.3.6\u201311.3.8. The rib cage includes the 12 thoracic vertebrae and the sternum, as well as 12 pairs of ribs, which are attached at joints to the vertebrae. The ribs are divided into three groups, called true ribs, false ribs, and floating ribs. The top seven pairs of ribs are true ribs. They are attached by cartilage directly to the sternum. The next three pairs of ribs are false ribs. They are attached by cartilage to the ribs above them, rather than directly to the sternum. The lowest two pairs of ribs are floating ribs. They are attached by cartilage to muscles in the abdominal wall. The attachments of false and floating ribs let the lower part of the rib cage expand to accommodate the internal movements of breathing.\r\n
Figure 11.3.4 The 14 bones that make up the face are labeled in this drawing of the skull.<\/em>[\/caption]\r\n![\"11.3.6](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/True_ribs_animation-2.gif\")
Figure 11.3.6 True ribs are attached to both the vertebrae and the sternum.\u00a0 In this image, true ribs are highlighted in red.<\/em>[\/caption]<\/td>\r\n![\"11.3.7](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/False_ribs_animation-2.gif\")
Figure 11.3.7 False ribs are attached to the vertebrae and to the ribs above them by cartilage.\u00a0 In this image, false ribs and floating ribs are highlighted in red.<\/em>[\/caption]<\/td>\r\n![\"11.3.8](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Floating_ribs_animation-2.gif\")
Figure 11.3.8 Floating ribs are attached to vertebrae and the the muscles in the abdominal wall. In this image floating ribs are highlighted in red.<\/em>[\/caption]<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n![\"11.3.9](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Appendicular_skeleton_diagram.svg_-2.png\")
Figure 11.3.9 The appendicular skeleton includes the upper and lower appendages and girdles.<\/em>[\/caption]\r\n![\"11.3.10](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Humerus_ulna_and_radius_female-2.png\")
Figure 11.3.10 The arm consists of three bones: the humerus, radius and ulna.[\/caption]\r\n\r\n[caption id=\"attachment_4008\" align=\"alignnone\" width=\"400\"]![\"11.3.11](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Human_left_hand_bones_with_metacarpal_numbers_and_carpal_letters.svg_-2.png\")
Figure 11.3.11 Bones of the wrist (carpals A-E) and hand (metacarpals 1-5 and phalanges).[\/caption]\r\n![\"11.3.12](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Human_leg_bones_labeled.svg_-2.png\")
Figure 11.3.12 Bones of the legs.<\/em>[\/caption]\r\n\r\nEach lower limb consists of 30 bones. As shown in Figure 11.3.12 to the left, there is one bone (called the femur) in each of the upper legs, and there are two bones (called the tibia and fibula) in each of the lower legs. The knee cap (or patella) is an additional leg bone at the front of each knee, which is the largest joint in the human body.\r\n\r\n[caption id=\"attachment_4010\" align=\"alignright\" width=\"233\"]![\"11.3.13](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Blausen_0411_FootAnatomy-2.png\")
Figure 11.3.13 Bones of the lower leg (fibula and tibia), ankle (talus), heel (calcaneus), foot (metatarsals), and toes (phalanges).<\/em>[\/caption]\r\n\r\nThe remaining bones of the lower limbs are in Figure 11.3.13 to the right. Each ankle contains seven tarsal bones (including the talus and calcaneus), and each foot contains five metatarsal bones. The tarsals and metatarsals form the ankle, heel, and arch of the foot. They give the foot strength while allowing flexibility. The bones in the toes of each foot consist of 14 phalanges (three in each toe except the big toe, which has two phalanges)\r\n\r\n![\"11.3.14](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Pectoral_girdle_front_diagram.svg_-2.png\")
Figure 11.3.14 Bones of the shoulder girdle.<\/em>[\/caption]\r\n\r\n![\"11.3.15](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/2048px-Blausen_0723_Pelvis-2.png\")
Figure 11.3.15 Bones of the pelvic girdle.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"3963\"]pelvic girdle[\/pb_glossary]<\/strong> attaches the legs to the trunk of the body, and also provides a basin to contain and support the organs of the abdomen. It is connected to the vertebral column of the axial skeleton by ligaments. The pelvic girdle consists of two halves \u2014 one half for each leg \u2014 but the halves are fused with each other in adults at a joint called the pubic symphysis. Each half of the pelvic girdle includes three bones, as shown in Figure 11.3.15 to the right: the ilium (flaring upper part of the pelvic girdle), pubis (lower front), and ischium (lower back). Each of these bones helps form the acetabulum, which is a depression into which the top of the femur (thighbone) fits. When the body is in a seated position, it rests on protrusions (called tuberosities) of the two ischial bones.\r\n![Human_skulls_on_display<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Human_skulls_on_display.JPG\"){kind=link}
![Axial_skeleton_diagram_blank.svg<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Axial_skeleton_diagram_blank.svg\"){kind=link}
![Axial skeleton diagram.svg<\/a>, by Mariana Ruiz Villarreal [](\"https:\/\/commons.wikimedia.org\/wiki\/File:Axial_skeleton_diagram.svg\"){kind=link}
![822px-Cranial_bones_en_v2.svg<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Cranial_bones_en_v2.svg\"){kind=link}
![File:Cranial bones en.svg<\/a>. by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Cranial_bones_en.svg\"){kind=link}
![Facial_skeleton_-_en.svg<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Facial_skeleton_-_en.svg\"){kind=link}
![File:Es-Human skull front simplified (bones).svg<\/a>. by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Es-Human_skull_front_simplified_(bones).svg\"){kind=link}
![Spinal_column_curvature<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Spinal_column_curvature.png\"){kind=link}
![True_ribs_animation<\/a> from](\"https:\/\/commons.wikimedia.org\/wiki\/File:True_ribs_animation.gif\"){kind=link}
![False_ribs_animation<\/a> from](\"https:\/\/commons.wikimedia.org\/wiki\/File:False_ribs_animation.gif\"){kind=link}
![Floating_ribs_animation<\/a> from](\"https:\/\/commons.wikimedia.org\/wiki\/File:Floating_ribs_animation.gif\"){kind=link}
![Appendicular_skeleton_diagram.svg<\/a> by Mariana Ruiz Villarreal [](\"https:\/\/commons.wikimedia.org\/wiki\/File:Appendicular_skeleton_diagram.svg\"){kind=link}
![Humerus,_ulna_and_radius_(female)<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Humerus,_ulna_and_radius_(female).png\"){kind=link}
![Human_left_hand_bones_with_metacarpal_numbers_and_carpal_letters.svg<\/a> by Mariana Ruiz Villarreal [](\"https:\/\/commons.wikimedia.org\/wiki\/File:Human_left_hand_bones_with_metacarpal_numbers_and_carpal_letters.svg\"){kind=link}
![Human_leg_bones_labeled.svg<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Human_leg_bones_labeled.svg\"){kind=link}
![Blausen_0411_FootAnatomy<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Blausen_0411_FootAnatomy.png\"){kind=link}
![Pectoral_girdle_front_diagram.svg<\/a> by Mariana Ruiz Villarreal [](\"https:\/\/commons.wikimedia.org\/wiki\/File:Pectoral_girdle_front_diagram.svg\"){kind=link}
![2048px-Blausen_0723_Pelvis<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Blausen_0723_Pelvis.png\"){kind=link}