Lower Extremity.docx

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Department
Anatomy and Cell Biology
Course
Anatomy and Cell Biology 3319
Professor
Kem Rogers
Semester
Fall

Description
Lower Extremity Pelvic Girdle • Attaches lower limps to spine and supports visceral organs of the pelvis • Full weight of upper body passes through girdle to lower limbs • Attaches to axial skeleton by very strong ligaments • Pelvic girdle socket is a deep cup that firmly secures the head of the femur • Lower limbs have less freedom of movement but are much more stable • Consists of o Paired hip bones o Sacrum (part of the axial skeleton) • Each hip bone (also called coxal or pelvic bone) units with its partner anteriorly & sacrum posteriorly • Deep structure formed by hip bones, sacrum & coccyx is the pelvis • During childhood, it consists of 3 separate bones: ilium, ischium, & pubis • In adults, 3 bones are fused and boundaries are indistinguishable • At Y-shaped junction of ilium, ischium & pubis - deep hemispherical socket: acetabulum on lateral pelvic surface  receives ball-shaped head of femur Ilium • Large, flaring bone that forms superior region of hip bone • Consists of: inferior body & superior winglike ala • Thicker superior margin of ala is iliac crest • Many muscles attach to crest – thickest at tubercle of iliac crest • Each iliac crest ends o Anteriorly in a blunt anterior superior iliac spine o Posteriorly in a sharp posterior superior iliac spine • Position of posterior superior iliac spines is indicated by dimples in skin that lie approx. 5 cm lateral to midline of the back at the junction of lumbar and gluteal regions • Located inferior to superior iliac spines are anterior & posterior inferior iliac spines • Posteriorly, just inferior to posterior inferior iliac spine – indented to form greater sciatic notch • Sciatic nerve, largest nerve in the body, passes through to enter posterior thigh • Broad posterolateral surface: gluteal surface - crossed by 3 ridges: posterior, anterior & inferior gluteal lines - define attachment sites of gluteal muscles • Internal surface of iliac ala is concave – iliac fossa • Posterior to fossa lies roughened auricular surface - articulates with sacrum, forming sacroiliac joint • Weight of the body is transmitted from vertebral column to pelvis through this joint • Running anteriorly & inferiorly from auricular surface is robust ridge: arcuate line o Defines superior boundary of true pelvis o Inferior part of ilium joins with ischium posteriorly Ischium • Forms posteroinferior region of hip bone • Shaped like an arc, it has a thicker, superior body & thinner, inferior ramus • Anteriorly ischial ramus joins pubis • Triangular ischial spine lies posterior to acetabulum and projects medially o Attachment point for a ligament from sacrum & coccyx: sacrospinous ligament • Just inferior to ischial spine is lesser sciatic notch o Nerves pass & vessels that serve perineum (area around anus & external genitalia) • Inferior surface of ischial body is rough & thickened ischial tuberosity – strongest part of hip bone o Bears all the weight of body when individual is sitting o Massive sacrotuberous ligament runs from sacrum to each ischial tuberosity & holds pelvis together o Area of attachment of hamstring muscles Pubis • Forms anterior region of hip bone • Lies nearly horizontal & bladder rests upon it • V-shaped, with superior & inferior rami extending from flat body • Body of pubis lies medially, & its anterior border is thickened to form pubic crest • At lateral end of each crest is knoblike pubic tubercle – attachment point for inguinal ligament • Two rami of the pubic bone – extend laterally o Inferior pubic ramus jons ischial ramus o Superior pubic ramus joins with bodies of ischium & ilium • Thin ridge: pectineal line – lies along superior pubic ramus – forming anterior portion of pelvic brim • Large hole: obturator formaen o Occurs between pubis & ischium o Few nerves & vessels pass through it o Almost completely closed by fibrous membrane: obturator membrane • In midline – bodies of two pubic bones are joined by disc of fibrocartilage – joint: pubic symphysis • Inferior to joint – inferior pubic rami & ischial rami from arch shaped like inverted V – pubic arch or subpubic angle o Angle of this arch helps to distinguish male pelvis from female pelvis Pelvic Structure • Body pelvis is divided into 2 parts: false (greater) pelvis & true (lesser) pelvis • Parts are separated by pelvic brim –oval ridge that runs form pubic crest through arcuate line – rounded inferior edges of sacral ala & the sacral promontory • False pelvis o Superior to pelvic brim o Bound by alae of iliac bones o Part of the abdomen & contains abdominal organs • True pelvis o Lies inferior to pelvic brim o Forms deep bowl containing pelvic organs Childbearing • Pelvic inlet o Delineated by pelvic brim o Largest diameter is from right to left in the frontal plane o As labor begins, infants head enters inlet & forehead faces one ilium & back of head faces other o If mother’s sacral promontory is too large – can block the entry of infant into true pelvis • Pelvic outlet o Inferior margin of true pelvis o Boundaries are pubic arch anteriorly, ischial tuberosities laterally & sacrum & coccyx posteriorly o Both coccyx & ischial spines protrude into outlet – sharp angled coccyx or unusually large ischial spine can interfere with delivery o Largest dimension is anteroposterior diameter o Generally after infants head passes through – rotates so that forehead faces posteriorly & back of its head faces anteriorly o Usual position of head as it leaves mother o During birth – infants head makes a quarter turn to follow widest dimensions of true pelvis • Female Pelvis o Tilts forward, adapting for childbearing o True pelvis defines the birth canal o Bones lighter, less dense o Smaller acetabula o Public angle more rounded (80-90 degrees) • Male Pelvis o Less forward tilt, better to support the heavier male build o Cavity of true pelvis is deep & narrow o Larger acetabula o Public angle is more acute (50-60 degrees) Lower Limb • Bones of lower limbs are thicker & stronger than the comparable bones of the upper limbs Thigh • Femur: single bone of the thigh, largest, strongest bone in the body • Femur courses medially as it descends toward the knee o Places knee joints closer to body’s centre of gravity in midline & provides for better balance o Pronounced in women because of wider pelvis – greater angle between femur & tibia (shinbone) o May contribute to greater incidence of knee problems in female athletes • Ball-like head of the femur has a small central put called fovea capitis • Short ligament, ligament of the head of the femur, runs from this pit to the acetabulum of the hip bone • Head of femur is carried on a neck, which angles laterally to join the shaft • Angled course reflects fact that femur articulates with lateral aspect, rather than inferior region of pelvis • Neck is the weakest part of the femur & is often fractured in a broken hip • Clinical application o Hip fracture as result of osteoporosis o When elderly people fall, breaking a hip – order of events is in many cases actually reverse o Bone loss causes neck to weaken & fracture from stresses that healthy bone would withstand o Fracture causes the person to fall • At junction of shaft & neck are lateral greater trochanter & posteromedial lesser trochanter, sites of muscle attachment • 2 trochanters are interconnected by intertrochanteric line anteriorly & by intertrochanteric crest posteriorly • Inferior to intertrochanteric crest on posterior surface of shaft is gluteal tuberosity • Inferior part of tuberosity blends into long vertical ridge, linae aspera (rough line) • Areas are sites of muscle attachments • Distally, femur broadens to end in lateral & medial condyles shaped like wide wheels o Joint surfaces that articulate with tibia • Most raised points, on sides of condyles: lateral & medial epicondyle – muscles & ligaments attach • Adductor tubercle is a bump on upper part of medial epicondyle • Anteriorly, 2 condyles are separated by a smooth patellar surface – articulates with kneecap or patella • Posteriorly, condyles are separated by a deep intercondylar fossa • Extending superiorly from respective condyles to linae aspera are lateral & medial supracondylar lines • Patella: triangular sesamoid bone enclosed in tendon - secures quadriceps muscles of anterior thigh to tibia • Protects the knee joint anteriorly & improves leverage of quadriceps muscle acting across the knee • Clinical Application: Osteochondromas of the Femur o Most common benign bone tumor o Tumor is often diagnosed as an incidental binding o Account for approx. 35% of benign bone tumors & 9% of all bone tumors o Exact etiology of these growths is not known – however a peripheral portion of the physis is thought to herniate rom the growth plate during bone growth o Can occur in any bone that undergoes enchondral bone formation – but they are most common around the knee, off the femur o Surgical excision is the only treatment Leg • Anatomists use the term leg to define lower part of limb between knee & ankle • Parallel bones, tibia & fibula – form skeleton • Tibia o Located medially o Bigger • Two bones articulate with each other both superiorly & inferiorly • Unlike the joints between radius & ulna – tibiofibular joints allow almost no movmenet • interosseous membrane connects tibia & fibula along their entire length • Tibia articulate with femur to form knee joint, & with talus bone of the foot at angle joint • Fibula does not contribute to the knee joint & merely helps stabilize the ankle joint Tibia • Receives the weight of the body from femur & transmits it to the foot • Second only to femur in size & strength • At its proximal end: broad medial & lateral condyles – resemble two thick checkers lying side by side on the top of the shaft, articulate with the corresponding condyles of the femur • Tibial condyles are separated by an irregular projection: intercondylar eminence • Inferior part of lateral tibial condyle has a facet that articulates with fibula to form superior tibiofibular joint • Just inferior to condyles, on tibia’s anterior surface, is tibial tuberosity – attachment of patellar ligament • Shaft of tibia is triangular in cross section • Sharp anterior border lies just below skin & is easily palpated • Distally, end of the tibia is flat where it articulates with talus of the foot • Medial to this joint surface, tibia has inferior projection: medial malleolus – forms medial bulge of ankle • Fibular notch, on lateral side of distal tibia, articulates with the tibula: forming inferior tibiofibular joint Fibula • Located lateral to the tibia • Thin long bone with two expanded ends • Superior end is its head, & its inferior end is lateral malleolus • Malleolus forms lateral bulge of ankle & articulates with talus bone of foot • Shaft of fibula is heavily ridged, fibula does not bear weight, but several muscles originate from it Foot • Skeleton of foot includes bones of tarsus, bones of metatarsus & phalanges (toe bones) • Foot has two important functions: o Supports weight of the body o Acts as a lever to propel body forward during walking or running • Single bone could serve both those purposes but would not function on uneven ground • Multicomponent structure makes foot pliable, avoiding this problem Tarsus • Makes up the posterior half of the foot & contains 7 bones tarsals • Weight of body is carried primarily by 2 largest, most posterior tarsal bones o Talus (ankle) which articulates with tibia & fibula superiorly o Strong calcaneus which forms the heel of the foot • Tibia articulates with the talus at the trochlae of the talus • Inferiorly, talus articulates with the calcaneus • Thick tendon of the calf muscles attaches to posterior surface of calcaneus • Part of calcaneus that touches ground is calcaneal tuberosity & medial, shelf-like projection is sustentaculum tali or talar shelf • Remaining tarsal bones are: lateral cuboid, medial navicular, & anterior, medial, intermediate & lateral cuneiforms • Clinical Application o Medial & lateral malleoli are commonly fractured when foot is forcefully inverted or everted at ankle - when one lands either on lateral side of foot & twists sole medially (inversion) or on medial side & turns sole laterally (eversion) o Types of injury occurs frequently in general population & in people participating in contact sports Metatarsus • Consist of five small long bones - numbered I to V beginning on medial side of foot • First metatarsal at base of the big toe is largest, & plays an important in supporting weight of the body • Are more nearly parallel to one another than are metacarpals in the palm • Distally, where metacarpals articulate with proximal phalanges of the toes, enlarged head of the first metatarsal forms ball of the foot • Clinical application o Metatarsal stress fracture o One of the most common foot injuries o Results from repetitive stress on foot, typically as a result of increasing running mileage too quickly o Second & third metatarsals are most often affected o Treatment generally involves resulting the foot & wearing stiff or well-cushioned shoes Phalanges of Toes • 14 bones of the toes are smaller than those of the fingers & are less nimble • 3 phalanges in each digit except great toe (hallus) - has only 2 phalanges - proximal, middle & distal Arches of the Foot • Structure composed of multiple components can support weight only if it is arched • Foot has three arches: o Medial & lateral longitudinal arches o Transverse arch • Arches are maintained by interlocking shapes of the foot bones, by strong ligaments, & by the pull of some tendons during muscle activity • Ligaments & tendons also provide resilience • Arches “give” when weight is applied to the foot & spring back when weight is removed • Medial longitudinal arch o Curves well above the ground o Footprints – foot’s medial margin, from heel to distal end of first metatarsal, leaves no print o Talus, near talonavicular joint – keystone of arch  Originates at the calcaneus, rises to talus & descends to the three medial metatarsals • Lateral longitudinal arch o Very low o Elevates lateral edge of foot just enough to redistribute some of body weight to calcaneus & some to the head of the fifth metatarsal (that is, two the two ends of the arch) o Cuboid bone is the keystone bone • Two longitudinal arches serve as pillars for transverse arch o Runs obliquely from one side of foot to other, following line of joints between tarsals & metatarsals • 3 arches form half dome that distributes approx. half of person’s standing & walking weight to heel bones & half to heads of metatarsals • Various tendons run inferior to foot bones, & help support arches of foot • Muscles associated with these tendons are less active during standing than walking • People who stand all day or running on hard surfaces without support may devel
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