Lower Extremity.docx

31 Pages
Unlock Document

Anatomy and Cell Biology
Anatomy and Cell Biology 3319
Kem Rogers

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
More Less

Related notes for Anatomy and Cell Biology 3319

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.