Chapter 8
Name the bones composing the acetabulum and state its function.
The acetabulum (as-e-TAB-ū-lum = vinegar cup) is a deep fossa (depression) formed by the ilium, ischium, and pubis. It functions as the socket that articulates with the rounded head of the femur to form the hip joint
Describe how the surface markings of the scapula and humerus articulate.
Each scapula or shoulder lade is a large triangular flat bone situated in the superior part of the posterior thorax. A prominent ridge called the spine runs diagonally across posterior surface of the scapula.The lateral end of the spine projects as flattened,expanded across process called acriomion, easily felt as a high point of the shoulder. Tailors measure the length of the upper limb from the acromion.The arcrimonion articulates with the end of the clavicle. Inferior to acrimion is a shallow depression called the the gelenoid cavity, that articulate with the head of humerous (arm bone). The thin edge of the scapula closer to the vertebral column is called the medial border (Figure 8.3). The thick edge closer to the arm is called the lateral border. The medial and lateral borders join at the inferior angle. The superior edge of the scapula, called the superior border, joins the medial border at the superior angle. At the lateral end of the superior border of the scapula is a projection of the anterior surface, called the coracoid process (KOR-a-koyd = like a crow's beak), to which the tendons of muscles and ligaments attach. Superior and inferior to the spine are two fossae: the supraspinous fossa (sū-pra-SPĪ-nus) and the infraspinous fossa (in-fra-SPĪ-nus), respectively. Each serves as a surface of attachment for a shoulder muscle. On the anterior surface is a slightly hollowed-out area called the subscapular fossa, also a surface of attachment for a shoulder muscle.
State the functions of the greater trochanter, lesser trochanter, medial condyle, and lateral condyle of the femur.
The greater trochanter (trō-KAN-ter) and lesser trochanter are projections of the femur that serve as points of attachment for thigh and buttock muscles. The greater trochanter is the prominence felt and seen anterior to the hollow on the side of the hip. It is a landmark commonly used to locate the site for intramuscular injections into the lateral surface of the thigh. The lesser trochanter is inferior and medial to the greater trochanter. Between the trochanters is an anterior intertrochanteric line (Figure 8.13a) and a posterior intertrochanteric crest (Figure 8.13b). On the posterior surface of the body of the femur is a vertical ridge called the gluteal tuberosity that blends into another vertical ridge called the linea aspera (LIN-ē-a AS-per-a; asper- = rough). Both of these ridges serve as attachment points for several thigh muscles. The distal end of the femur expands to include the medial condyle (= knuckle) and the lateral condyle. These articulate with the medial and lateral condyles of the tibia to form the knee joint. Superior to the condyles are the medial epicondyle and the lateral epicondyle. A depressed area between the condyles on the posterior surface is called the intercondylar fossa (in-ter-KON-di-lar). The patellar surface, located anteriorly between the condyles, is a smooth surface over which the patella glides.
State the functions of the deltoid tuberosity, medial epicondyle, and lateral epicondyle of the humerus.
The medial epicondyle and lateral epicondyle are rough projections on either side of the distal end of the humerus to which most muscles of the forearm are attached. The ulnar nerve may be palpated by rolling a finger over the skin surface above the posterior surface of the medial epicondyle. This superficial nerve makes you feel a severe pain when you hit your elbow, which for some reason is commonly referred to as the funny bone even though this event is anything but funny.
State the function of the lateral malleolus of the fibula.
The medial surface of the distal end of the tibia forms the medial malleolus (mal-LĒ-ō-lus = hammer). This structure articulates with the talus of the ankle and forms the prominence that can be felt on the medial surface of the ankle. The fibular notch (Figure 8.15c) articulates with the distal end of the fibula. The fibula is parallel and lateral to the tibia, but is considerably smaller. Figure 8.15 includes a mnemonic describing the relative positions of the tibia and fibula. Unlike the tibia, the fibula does not articulate with the femur, but it does help stabilize the ankle joint. The head of the fibula, the proximal end, articulates with the inferior surface of the lateral condyle of the tibia below the level of the knee joint. The distal end has a projection, the lateral malleolus, that articulates with the talus of the ankle. The lateral malleolus is the prominence on the lateral surface of the ankle. As noted previously, the fibula also articulates with the tibia at the fibular notch.
Describe the structure and function of the pectoral girdle.
The pectoral gridle or shoulder girldes attaches bones of the upper limb to the axial skeleton.Each of the two pectoral girdles consists of a clavicle and and a scapula.The clavicle,the anterior bone,articulates with the manubrium of the sternum;the scapula,the posterior bone,articulates with the clavicle and humerous, The pectoral girldes do not articulate (form joints) with the vertebral column and are held in the position and stabalized by a group of large muscles that extend from the vertebral column and ribs to the scapula.
Describe the structure and function of the pelvic girdle.v
The pelvic (hip) girdle consists of the two hip bones, also called coxal bones (KOK-sal; cox- = hip) (Figure 8.9). The hip bones unite anteriorly at a joint called the pubic symphysis (PŪ-bik SIM-fi-sis). They unite posteriorly with the sacrum at the sacroiliac joints. The complete ring composed of the hip bones, pubic symphysis, sacrum, and coccyx forms a deep, basinlike structure called the pelvis (plural is pelves [PEL-vēz]; pelv- = basin). Functionally, the pelvis provides a strong and stable support for the vertebral column and protects pelvic and lower abdominal organs. The pelvic girdle of the pelvis also connects the bones of the lower limbs to the axial skeleton.
Distinguish between the pelvic girdle and pelvis; know that "pelves" is the correct plural form of "pelvis".
The pelvic (hip) girdle consists of the two hip bones, also called coxal bones (KOK-sal; cox- = hip) (Figure 8.9). The hip bones unite anteriorly at a joint called the pubic symphysis (PŪ-bik SIM-fi-sis). They unite posteriorly with the sacrum at the sacroiliac joints. The complete ring composed of the hip bones, pubic symphysis, sacrum, and coccyx forms a deep, basinlike structure called the pelvis (plural is pelves [PEL-vēz]; pelv- = basin). Functionally, the pelvis provides a strong and stable support for the vertebral column and protects pelvic and lower abdominal organs. The pelvic girdle of the pelvis also connects the bones of the lower limbs to the axial skeleton.
Describe how the surface markings of the femur, tibia, and fibula articulate.
The proximal end of the tibia is expanded into a lateral condyle and a medial condyle, which articulate with the condyles of the femur to form the knee joint. The inferior surface of the lateral condyle articulates with the head of the fibula. The slightly concave condyles are separated by an upward projection called the intercondylar eminence (Figure 8.15b). The tibial tuberosity on the anterior surface is a point of attachment for the patellar ligament. Inferior to and continuous with the tibial tuberosity is a sharp ridge that can be felt below the skin, known as the anterior border or shin. The medial surface of the distal end of the tibia forms the medial malleolus (mal-LĒ-ō-lus = hammer). This structure articulates with the talus of the ankle and forms the prominence that can be felt on the medial surface of the ankle. The fibular notch (Figure 8.15c) articulates with the distal end of the fibula. The fibula is parallel and lateral to the tibia, but is considerably smaller. Figure 8.15 includes a mnemonic describing the relative positions of the tibia and fibula. Unlike the tibia, the fibula does not articulate with the femur, but it does help stabilize the ankle joint. The head of the fibula, the proximal end, articulates with the inferior surface of the lateral condyle of the tibia below the level of the knee joint. The distal end has a projection, the lateral malleolus, that articulates with the talus of the ankle. The lateral malleolus is the prominence on the lateral surface of the ankle. As noted previously, the fibula also articulates with the tibia at the fibular notch.
State the functions of the tibial tuberosity and medial malleolus of the tibia.
The proximal end of the tibia is expanded into a lateral condyle and a medial condyle, which articulate with the condyles of the femur to form the knee joint. The inferior surface of the lateral condyle articulates with the head of the fibula. The slightly concave condyles are separated by an upward projection called the intercondylar eminence (Figure 8.15b). The tibial tuberosity on the anterior surface is a point of attachment for the patellar ligament. Inferior to and continuous with the tibial tuberosity is a sharp ridge that can be felt below the skin, known as the anterior border or shin. The medial surface of the distal end of the tibia forms the medial malleolus (mal-LĒ-ō-lus = hammer). This structure articulates with the talus of the ankle and forms the prominence that can be felt on the medial surface of the ankle. The fibular notch (Figure 8.15c) articulates with the distal end of the fibula. The fibula is parallel and lateral to the tibia, but is considerably smaller. Figure 8.15 includes a mnemonic describing the relative positions of the tibia and fibula. Unlike the tibia, the fibula does not articulate with the femur, but it does help stabilize the ankle joint. The head of the fibula, the proximal end, articulates with the inferior surface of the lateral condyle of the tibia below the level of the knee joint. The distal end has a projection, the lateral malleolus, that articulates with the talus of the ankle. The lateral malleolus is the prominence on the lateral surface of the ankle. As noted previously, the fibula also articulates with the tibia at the fibular notch.
State the location and composition of the pubic symphysis.
The pubis (PŪ-bis), or pubic bone, is the anterior and inferior part of the hip bone (Figure 8.10b, c). A superior ramus, an inferior ramus, and a body between the rami comprise the pubis. The anterior, superior border of the body is the pubic crest, and at its lateral end is a projection called the pubic tubercle. The pubic symphysis is the joint between the two hip bones (Figure 8.9). It consists of a disc of fibrocartilage. Inferior to this joint, the inferior rami of the two pubic bones converge to form the pubic arch. In the later stages of pregnancy, the hormone relaxin increases the flexibility of the pubic symphysis to ease delivery of the baby. Weakening of the joint, together with an already compromised center of gravity due to an enlarged uterus, also changes the mother's gait during pregnancy.
Describe how the surface markings of the humerus, ulna, and radius articulate.
The ulna and radius articulate with the humerus at the elbow joint. The articulation occurs in two places: where the head of the radius articulates with the capitulum of the humerus, and where the trochlear notch of the ulna receives the trochlea of the humerus (Figure 8.7). The ulna and the radius connect with one another at three sites. First, a broad, flat, fibrous connective tissue called the interosseous membrane (in′-ter-OS-ē-us; inter- = between, -osseous = bone) joins the shafts of the two bones. The ulna and radius also articulate at their proximal and distal ends. Proximally, the head of the radius articulates with the ulna's radial notch (Figure 8.7b). Distally, the head of the ulna articulates with the ulnar notch of the radius (Figure 8.7c). Finally, the distal end of the radius articulates with three bones of the wrist—the lunate, the scaphoid, and the triquetrum—to form the wrist joint.