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PinkMonkey Online Study Guide-Biology

(D) Leg or Hindlimb bones

(a) Femur (Thigh bone). (Figure 20.19). (1) It is the longest and strongest bone in the body, and consists of upper end, shaft and lower end. (2) The head articulates with the acetabulum the of hip bone giving a secure joint but with less freedom of movement. Below the head is the neck, greater and lesser trochanter, and a small depression called the foveas, or pit. (3) The shaft is narrow in the center with nutrient foramen. (4) The lower end of the femur articulates with the tibia and patella. It consists of thick medial and lateral condyles separated from each other by an inter condylar fossa or notch. (5) This notch lies within the capsule of the knee joint and gives attachment to ligaments. (6) The patella (knee cap) is a flattened, triangular bone present in front of the knee joint, and its posterior surface articulates with femoral condyles.

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Figure 20.19 Femur Figure 20.20 Tibia-Fibula


(b) Tibia - Fibula (Figure 20.20)

(1) These are bones of the shank (lower leg) the tibia on the medial and fibula on the lateral side of the leg. (2) The tibia is stronger and transmits body weight from femur to the foot. The fibula is long but slender and does not articulate with either patella or femur. (3) The upper end of the tibia is broad and consists of medial and lateral condyles and a tuberosity. The tibia takes part in formation of several joint, knee, ankle and superior and inferior-tibio-fibular joints. The lower end is smaller and has a strong process (medial malleolus). (4) In the fibula, the upper end is rounded with a circular facet for articulation with fibular faced on lateral condyle of tibia. The styloid process is a small blunt process. The lower end of the fibula is expanded, flat and is called the "lateral malleolus."

(c) Tarsal Bones

(1) These are seven bones of the ankle which form the skeleton of the posterior part of the foot. They are arranged in two rows.

(2) Proximal row has (a) Talus and (b) Calcaneus.

(3) Distal row has (a) Medial cuneiform, (b) Intermediate cuneiform, (c) Lateral cuneiform and (d) Cuboid. These are adapted for supporting weight. (d) Metatarsals and Phalanges The foot has five metatarsals, which correspond to the metacarpals of the palm; and 14 phalanges - two in the big toe and three in the other toes.

SUMMARY

(1) The skeleton has basic functions like support, protection, movement and locomotion, muscle attachment, hemopoiesis and storage of calcium and phosphate. (2) The adult human skeleton consists of 206 bones. (3) The entire skeleton is divided into the axial skeleton (skull, ear, ossicles, hyoid bone, vertebral column, sternum and ribs) and appendicular skeleton (bones of pectoral girdle, pelvic girdle, arms and legs). (4) The femur is the longest and strongest bone, and the stapes is the smallest bone in the body. (5) Adult male and female skeletons can be identified by the differences in the structures of the skull, sacrum, coccyx and pelvis.

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Table of Contents

20.0 - Introduction
20.1 - Axial Skeleton
20.2 - Appendicular Skeleton

Chapter 21





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