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Skeletal System – Part 7. Bones of the Pelvic Girdle. Pelvic Girdle - Formed by two coxal bones , commonly called the hip bones . Bony Pelvis – Hip bones + coccyx + sacrum. Bones of the Pelvic Girdle. Large and heavy bones, and they are attached to the axial skeleton.
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Bones of the Pelvic Girdle • Pelvic Girdle- Formed by two coxal bones, commonly called the hip bones. • Bony Pelvis– Hip bones + coccyx + sacrum
Bones of the Pelvic Girdle • Large and heavy bones, and they are attached to the axial skeleton. • The sockets, which receive the thigh bones, are deep and heavily reinforced by ligaments that attach the limbs firmly to the girdle.
Bones of the Pelvic Girdle • Functions of the Girdle: • Bearing weight is the most important function. • Protect the reproductive organs, urinary bladder, and part of the large intestine.
Structure of the Hip Bones • Each hip bone is formed by the fusion of three bones: • Ilium • Ischium • Pubis
Ilium • Ilium – Large, flaring bone that forms most of the hip bone. • Connects posteriorly with the sacrum at the sacroiliac joint. • When you put your hands on your hips, they are resting over the winglike portion of the ilia. • Iliac Crest – The upper edge of the winglike portion of the ilium.
Ischium and the Pubis • Ischium – “Sitdown bone”; Forms the the most inferior part of the coxal bone. • Pubis – Most anterior part of a coxal bone.
Acetabulum • Acetabulum – Deep socket that receives the head of the thigh bone. • Formed by the fusion of the ilium, ischium, and pubis.
Regions of the Bony Pelvis • False Pelvis– Superior to the true pelvis; The area medial to the flaring portions of the ilia. • True Pelvis- Surrounded by bone; Lies inferior to the flaring parts of the ilia and the pelvic brim. • Dimensions of the true pelvis of a woman are very important because they must be large enough to allow the infant’s head to pass during childbirth.
Differences Between a Male and Female Pelvis • The pelvis of a female tends to be: • Inlet is larger and more circular. • As a whole is shallower, and the bones are lighter and thinner. • Ilia flare more laterally. • Sacrum is shorter and less curved. • Ischial spines are shorter and farther apart; thus the outlet is larger. • Pubic arch is more rounded because the angle of the pubic arch is greater.
Bones of the Lower Limbs • The lower limbs carry our total body weight when we are erect. • Hence, it is not surprising that the bones of the lower limbs are much thicker and stronger than the comparable bones of the upper limb. • The 3 segments of the lower limbs: • Thigh • Leg • Foot
Thigh • Femur – Thigh bone. • Only bone in the thigh. • The heaviest, strongest bone in the body. • It slants medially as it runs downward to join with the leg bones. • This brings the knees in line with the body’s center of gravity. • The medial course of the femur is more noticeable in females because of the wider female pelvis.
Structure of the Femur Bone – Proximal End • Its proximal end has a: • Ball-like head • The head of the femur articulates with the acetabulum of the hip bone in a deep, secure socket. • A neck • Common site of fractures, especially in old age.
Structure of the Femur Bone – Distal End • Anteriorly on the distal femur is the smooth patellar surface, which forms a joint with the patella (kneecap).
Leg • Two bones form the skeleton of the leg: • Tibia • Fibula • The tibia and fibula are connected along their length by an interosseous membrane.
Tibia and Fibula • Tibia – Shinbone; Larger and more medial. • At the proximal end, the tibia articulates with the distal end of the femur to form the knee joint.
Tibia and Fibula • Fibula – Lies alongside the tibia; Thin and sticklike. • Forms joints with the tibia both proximally and distally. • Has no part in forming the knee joint. • The distal end of the fibula forms the outer part of the ankle.
Foot • The foot is composed of the: • Tarsals • Metatarsals • Phalanges
Foot • Two important functions of the foot: • Supports our body weight • Serves as a lever that allows us to propel our bodies forward when we walk or run.
Foot: Tarsals • Tarsus – The posterior half of the foot. • Composed of 7 tarsal bones. • Body weight is mostly carried by the two largest tarsals: • Calcaneus - Heelbone • Talus – Tarsal that lies between the tibia and the calcaneus.
Foot: Metatarsals and Phalanges • The sole of the foot: • Composed of 5 metatarsals. • The toes of the foot: • Composed of 14 phalanges. • Like the fingers of the hand, each toe has three phalanges, except the great toe which has two.
Arches of the Foot • The bones in the foot are arranged to form three strong arches: • Two longitudinal (medial and lateral) • One Transverse • Ligaments (bind the foot bones together) and tendons: • Help to hold the bones firmly in the arched position but still allow a certain amount of give or springiness.