There are 32 bones in the lower extremity:
Hip bone (1)
Femur (1)
Patella (1)
Tibia (1)
Fibula (1)
Tarsals (8)
Metatarsals (5)
Phalanges(14)
Hip Bone
The coxal bone (innominate or hip bone) is the supporting bone of the body. It is very important bone because its fracture cause two litre blood to bleed. It is mainly consist of three parts: ileum, ischium and pubis which fuse together at the time of puberty.
Ileum
It is the superior part of the hip bone. The margin of the ileum is called as ilaiac crest. The iliac crest has two projections anteriorly: Anterior superior iliac spine and Anterior inferior iliac spine. The iliac crest has also two projections posteriorly: Posterior superior iliac spine and Posterior inferior iliac spine.
Ischium
It is the posterior inferior part of the hip bone. It starts below the sciatic notch. Ischium has a body and a ramus. The body of the ischium starts ischial spine. Below the this spine is the ramus of the ischium. The ramus has a downward projection called as ischial tuberosity which we use to sit.
Pubis
It is the anterior inferior part of the hip bone. It forms the anterior border of the pelvic brim. It has a body and two rami (superior and inferior). On the interior side of the superior ramus of the pubic bone is a curved line which is the continuation of arcuate line called as illeopectineal line which completes the circle of pelvic brim anteriorly. The inferior ramus has a downward projection called as pubic tuberosity. Anteriorly the right and left pubic bones form the pubis symphysis.
All the three parts of the hip bone meet at the Y shaped area at the acetabulum. Both the rami of pubis, body and inferior ramus of ischium form a foramen called as obturator foramen for the passage of the obturator nerve anmd vessels.
Femur
It is the longest and strongest bone of the body. It is 30-35cm in male and 35- 40cm in female. superiorly it forms the hip joint and inferiorly it forms the patellfemoral and tibiofemoral joints( knee joint). The superior end consists of a head, neck, and two trochanters [greater(lateral projection) and lesser(medial projection)]. The head has a small depression called as fovia capitis to which the ligament of the head is attached. The femoral neck is separated from the shaft anteriorly by the intertrochanteric line and posteriorly by intertronchanteric crest. Below the crest is the elevation called as Quadrate tubercle. The greater trochanter is situated laterally and can be palpated (most easily with the hip abducted) on the lateral side of the thigh. The lesser trochanter projects medially at the junction of the neck with the shaft.
The shaft of the femur (convex anteriorly) presents anterior, medial, and lateral surfaces. In the middle third, the prominent posterior border is known as the linea aspera. It has medial and lateral lips and an intermediate area b/w medial and lateral lips that broadens into a posterior surface in the upper and lower thirds of the shaft. The superior aspect of the medial lip of the linea aspera is continuous with the spiral line and the lateral lip is continuous with the gluteal tuberosity. The inferior part of the medial lip of the linea aspera is continuous with the medial supracondylar line and ends in the adductor tubercle. The lateral lip is continuous as the lateral supracondylar line, which descends to the lateral epicondyle. The posterior, or popliteal, surface lies between the two supracondylar lines at the posteroinferior part of the femur. The inferior end of the femur consists of two condyles, which are continuous anteriorly but separated inferiorly and posteriorly by the intercondylar fossa. Medially, the most prominent part of the medial condyle is the medial epicondyle. Laterally, the lateral condyle presents the lateral epicondyle.
Patella
It is the largest sessamoid bone of the body. It grows in the Quadriceps femoris muscle of the thigh. There are four borders of the patella i.e. Base, Apex, Medial border and Lateral border. The superior border of the patella is the base of the triangle. Its lateral and medial borders descend to converge at the apex.
It has two surfaces; Muscular surface(anterior) and Articular surface(posterior). The patella articulates on its posterior side with the patellar surface of the condyles of the femur.
Tibia
Tibia is the large weight bearing medial bone of the leg.It can be palpated on the anterior and medial sides of the leg. The superior end is expanded for articulation with the inferior end of the femur. It has medial and lateral condyles. The upper parts of medial and lateral condyles which make the articular surface of the knee joint are called medial and lateral pleateaus having semicircular meniscus. Both the pleateaus are separated by intercondylar eminence.
The shaft of the tibia has medial, lateral, and posterior surfaces that are separated from one another by anterior, lateral, and medial borders. The posterior surface is crossed superiorly by a rough ridge termed as soleal line. The inferior end of the tibia has a lateral surface, which terminates in the fibular notch (for articulation with the lower end of the fibula), a medial surface, which runs onto the distal prolongation of the tibia known as the medial malleolus; and an inferior surface, that articulates with the talus.
Fibula
The weak lateral bone of the leg which doesn't take part in the weight bearing. The fibula articulates with the tibia superiorly and with the talus inferiorly and is anchored in between to the tibia by the interosseous membrane.The head is on the same level as the tuberosity of the tibia. The inferior end of the fibula, or the lateral malleolus, is more prominent, more posterior and extends about 1 cm more distally than the medial malleolus. It articulates with the tibia and with the lateral surface of the talus.
Tarsals
Calcaneum (heel):
It is the biggest and most strongest bone among the tarsal bones.Half of the body weight is carried by the calcaneum. It is irregular type of bone having four surfaces: Anterior, posterior, superior, and inferior.
Anteriorly: Calcaneum forms the joint with the cuboid bone.
Posteriorly: The strongest tendon of the body, Achilles tendon attaches to the calcaneum.
Superiorly: Calcaneum forms talo-calcaneal joint which is separated by a groove called as sulcus calcani.
Inferiorly: On the medial side of the calcaneum is the shelf like process called sustenaculum talus .On the lateral side the calcaneum there is small tubercle called peroneal tubercle,which separates the tendon of peroneus longus and peroneus brevis muscle.
Talus:
It is the adjoining bone of other tarsals and leg bones.
Superiorly: It form the joint with medial and lateral meleolus called as ankle joint.
Anteriorly: Its head form joint with the navicular called as talonavicular joint.
The talus has head, neck and body.The neck is the narrow part of the talus which has a groove on its inferior surface called as sulcus tali. Sulcus tali along with sulcus calcani form the sinus tarsi for the passage of interroseus talocalcaneal ligament. Body is the most posterior part of the talus which form the joint superiorly, with the tibia and fibula, inferiorly,with the calcaneum. Importantly talus has no muscle insertion.
Navicular (little boat):
The navicular lies between the talus on the posterior side and the three cuneiforms that are immediately anterior to it.
Cuboid (cube shape):
The cuboid articulates posteriorly with the calcaneus, anteriorly with the fourth and fifth metatarsals, and medially with the lateral cuneiform and sometimes the navicular.
Three Cuneforms:
The three cuneiform bones, so called because they are wedge-shaped, lie anterior to the navicular and posterior to the first three metatarsals.
Metatarsals
The tarsus is connected to the phalanges by five metatarsal bones, referred to collectively as the metatarsus. They are numbered from 1 to 5, from medial to lateral. They are longer and thinner than the metacarpals. Each metatarsal is a long bone, consisting of a base proximally, a shaft, and a head distally.
Phalanges
The great toe (and frequently the little toe) has two phalanges, whereas each of the other toes has three. They are proximal, middle, and distal. Each phalanx is a long bone, consisting of a base proximally, a shaft, and a head distally.
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