BIOL 2457 1st Edition Lecture 17Outline of Last Lecture The skeletal system: metacarpals and phalangesOutline of Current LectureSKELETAL SYSTEM: lower limb Skeleton of lower limb Skeleton of the Lower Limbs Two separate regions A single pelvic girdle (2 bones) The free part (30 bones)Pelvic (Hip) Girdle Each coxal (hip) bone consists of three bones that fuse together: ilium,pubis, and ischium The two coxal bones are joined anteriorly by the pubic symphysis (fibrocartilage) Joined posteriorly by the sacrum forming the sacroiliac joints (Fig 8.9)The illium Largest of the three hip bones Ilium is the superior part of the hip bone Consists of a superior ala and inferior body which forms the acetabulum (the socket for the head of the femur) Superior border - iliac crest Hip pointer - occurs at anterior superior iliac spine Greater sciatic notch - allows passage of sciatic nerveComparing male and female pelves Males Bones are larger and heavier Pelvic inlet is smaller and heart shaped Pubic arch is less than 90° Female Wider and shallower Pubic arch is greater than 90° More space in the true pelvis (Table 8.1)Skeleton of the thigh- femur Longest, heaviest, and strongest bone in the body Proximally, the head articulates with the acetabulum of the hip bone forming the hip (coxal) joint Neck - distal to head, common site of fracture Distally, the medial and lateral condyles articulate with the condyles ofthe tibia forming the knee joint Also articulates with patellaPatella Largest sesamoid bone in the body Forms the patellofemoral joint Superior surface is the base Inferior, narrower surface is the apex Thick articular cartilage lines the posterior surface Increases the leverage of the quadriceps femoris muscle Patellofemoral stress syndrome - “runner’s knee”Tibia The larger, medial weight-bearing bone of the leg The lateral and medial condyles at the proximal end articulate with the femur It articulates distally with the talus and fibula Tibial tuberosity - attachment site for the patellar ligament Medial malleolus - medial surface of distal end (medial surface of ankle joint)Fibula The smaller, laterally placed bone of the leg Non-weight bearing The head forms the proximal tibiofibular joint Lateral malleolus - distal end, articulates with the tibia and the talus atthe ankleSkeleton of the foot Seven tarsal bones - talus (articulates with tibia and fibula), calcaneus (the heel bone, the largest and strongest), navicular, cuboid and three cuneiforms Five metatarsals - (I-V) base, shaft, head 14 phalanges (big toe is the hallux) Tarsus = ankleDevelopment of the skeletal system Most skeletal tissue arises from mesenchymal cells The skull develops during the fourth week after fertilization Fontanels are the spaces between the skull bones during fetal life and infancy Upper limb buds form during the fourth week after fertilization followed by the lower limb buds During the sixth week, hand plates and foot plates form Vertebrae and ribs are formed from sclerotomes of somites Failure of proper development of the vertebral arches leads to spina
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