Download Bones of Appendicular Skeleton Notes

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Transcript
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Bones of the Appendicular Skeleton
Formed by limbs and their girdles- they are “appended” to axial skeleton to enable movement
o Pectoral girdles attach upper limbs to body trunk and provide attachment points for many muscles that help move
upper limbs
o Pelvic girdle is more sturdy, and attaches lower limbs to the trunk (body)
Bones of upper and lower have 3 basic parts, and are connected by movable joints
Upper Extremities
 Pectoral (Shoulder) Girdles-paired, one on each side- clavicle anteriorly and scapula posteriorly
o These along with muscles associated with them form your shoulders
o Girdle usually go all the way around, so shoulder girdles do not quite meet requirement
 Scapulae are attached to thorax and vert column by muscles only
 Pectoral girdle is very light, and allows movement not seen anywhere else in the body, 2 reasons:
 Only the clavicle attaches to the axial skeleton, scapula can move freely across thorax and arms
can move with them
 Socket of shoulder joint is shallow and poorly reinforced, does not restrict movement of the
humerus, bad for stability- dislocation common
 Clavicles- collar bones- slender curved bones that go horizontally across superior thorax
 Sternal end- medial end (attaches to sternal manubrium- bow tie part)
 Acromial end- flattened lateral end (articulates with scapula)
 Very sensitive to mechanical forces, become noticeably large in those who do manual labor or
athletics involving shoulder and arm muscles
 Scapula- shoulder blades- thin triangular flat bones, dorsal surf rib cage between ribs 2 and 7
 Name comes from word meaning spade, ancient man used animal scapula as shovels
 glenoid cavity- articulates with humerus of arm= shoulder joint (also a point of attachment for
biceps)
 acromion- point of shoulder- articulates with acromial end of clavicle to form acromioclavicular
joint
 coracoid process- projects anteriorly from superior border- held anchor biceps (just medial to
acromion)
o
Upper Limb- formed of 30 separate bones
 Arm- humerus is sole bone, typical long bone- longest bone of upper limb- articulates with scapula at
shoulder and radius and ulna at elbow
 Proximal end or head fits into glenoid cavity, allows arm to hang freely at side
 Just inferior to head= anatomical neck- slight constriction
 Inferior to that are attachment points for rotator cuff muscles (lateral= greater tubercle, medial=
lesser tubercle)
 Distal to tubercles is the surgical neck- called because most commonly broken part
 Deltoid tuberosity- half way down shaft on lateral side- rough spot to attach deltoid muscle of
shoulder
 2 condyles at distal end of humerus articulate with ulna and radius, flanked with medial and
lateral epicondyles- muscles attachment- above them are grooves for nerves, your ulnar nerve
runs behind the medial epicondyle and is responsible for the painful, tingly feeling when you hit
your “funny bone”
o medial epicondylitis- golfer’s elbow
o lateral epicondylitis- tennis elbow
 depressions near the surface above medial condyle
o condyles allow elbow to flex and extend,
 Forearm= antebrachium
 Radius- lateral, ulna- medial, when pronate arms (make palms face back) distal end radius
crosses over= X
o Ulna- medial forearm bone, slightly longer than radius, forms most of elbow joint with
humerus
 Two processes: olecranon processes (part that forms angle of elbow and rests
on tables) and coronoid process separated by trochlear notch- processes grip
the trochlea of the humerus hinge for bending and straightening (flexion and
extension)
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When you “lock your elbows” the olecranon process locks into the olecranon
fossa- stopping the arm from hyperextension
o Radius- lateral forearm bone, thin proximal end, wide distal (opposite ulna)
 radial tuberosity- inferior to head, attachment for biceps
 small medial ulnar notch articulates with ulna
 styloid process- ligaments run to wrist
 between ulnar notch and styloid process is concave, so can articulate with
carpal bones, major contributor to wrist and hand movement (ulna= more
elbow)
Hand- includes carpus (wrist), metacarpus (palm) and phalanges (fingers)
 Carpus- actually below where a wrist watch goes, a bracelet is actually worn on the distal end of
the forearm, wrist is proximal part of what we call our hand- made of 8 marble size bones called
carpals, closely united by ligaments
o Bones glide past one another to give lots of flexibility
o 2 irregular rows of 4
o proximal first, lateral to medial- scaphoid, lunate, triquetral and pisiform
 scaphoid and lunate articulate with radius to form wrist joint
o next distal, lateral to medial- trapezium, trapezoid, capitate and hamate
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“Sally Left The Party To Take Cathy Home” if that helps 
o bones form so the carpus is concave anteriorly with a ligament roof over the concavity=
the carpal tunnel- median nerve that supplies hand, many muscles and tendons crowd
through here, over use causes them to swell (repeated flexion), compressing the median
nerve= tingling and numbness in areas served, pain greatest at night, splint or surgery
 Metacarpus- radiate from wrist like spokes to form palm, not named, just numbered 1-5 from
thumb (lateral) to little finger (medial)
o Bases articulate with the carpals proximally and the other medially and laterally
o Heads (knuckles of fist) articulate with proximal phalanges of fingers
o 1- with thumb, most mobile, more anterior than other metacarpals, creates a special
saddle joint, allows opposition
 Phalanges- fingers or digits- also 1-5
o 1= pollex or thumb; thumb has no middle phalanx (singular)
o 3= usually longest
o except thumb, each has 3 phalanges- distal, middle, and proximal
Lower Extremities and hip
 Pelvic (Hip) Girdle
o Attaches lower limbs to axial skeleton, transmits weight of upper body to lower limbs, supports visceral organs of
the pelvis
o Unlike pectoral girdle that is sparingly attached to thoracic cage, pelvic girdle is attached to axial skeleton by some
of strongest ligaments in body
 Also, glenoid cavity shallow, sockets of pelvic girdle deep, firmly secure head of femur (can’t wheel legs
around like arms, even though both are ball and socket joints)- not as mobile, but much more stable!
o Made of pair of hip bones= coxal bones, unite anteriorly to each other and posteriorly with the sacrum
 Deep basin formed by coxal bones together with sacrum= bony pelvis
 Hip bones= 3 separate bones in childhood that fuse= ilium, ischium and pubis. Where all 3 meet= deep
socket called acetabulum; receives head of femur at hip joint
 Ilium- flaring bones= superior region coxal bone
 Body with superior ala (wings)
 Iliac crests- thickened superior crest- part you rest your hands on
 Greater sciatic notch- sciatic nerve passes through
 Posterolateral surface has 3 ridges for gluteal muscles to attach
 Ischium- posterior-inferior part of hip bone, L or arc shaped- thick body joins with ilium and ramus
(branches) joining pelvis
 Ischial spine- projects medially into pelvic cavity- attachment for ligament from sacrum
(sacrospinous ligament)
 Ischial tuberosity- rough, thickened portion, inferior surface of body, weight all goes her when
we sit- strongest part of hip bones, sometimes called “sit bones”
o Also site of attachment for hamstring muscles (post thigh)
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Pubis (pubic bone) is the anterior portion of coxal bone- V-shaped- anatomical position runs nearly
horizontal, urinary bladder rests on it
 Pubic crest= thickened portion on anterior of medial body
 Obturator foramen- large opening in coxal bone- rami of pubic bone run laterally and join with
ramus and body of ischium- blood vessels and nerves pass through, nearly closed off by fibrous
membrane in life (obturator= closed up)
 Pubic symphysis- fibrocartilage disc where 2 pubic bones join
 Pubic arch- form V angle - Acuteness of this angle helps us tell male from female
o Male vs female (table 7.4 in textbook)
 female modified for child bearing- wider, shallower, lighter and rounder to accommodate growth and
large enough for infant’s relatively large head to exit at birth
 dimensions of pelvis (especially inlet and outlet) critical in uncomplicated child birth, measured carefully
by obstertrician
Lower Limbs
o Carry weight of entire body and subject to lots of force when we run, jump, etc- they are thicker and stronger than
upper limbs
 Thigh- femur- largest, longest and strongest bone in body
 Clothed by large muscles, can’t feel it all the way down
 Attaches to hip proximally (head) and curves medially to knee
o Arranged so knees are closer to center of gravity= better balance
 Head carried on neck, angle laterally to shaft (just like humerus)
o Neck= weakest part, often fractured= “broken hip”
 Greater and lesser trochanter-at junction shaft and neck, lateral and postermedial respectivielysites of attachment for thigh and buttox muscles
 Distally femur broadens, ends in lateral and medial condyles (again, like humerus!)- articulate
with tibia of leg
o Lateral and medial epicondyles- flank superiorly- more muscle attachmento Smooth surface between condyles= patellar surface- articulates with patella (knee cap)
 Patella- triangular sesamoid bone, enclosed by quadriceps tendon that secures anterior muscles
of thigh to tibia- protects knee joint and improves leverage of thigh muscles acting across the
knee
Leg and foot
o Tibia and fibula- connected by interosseous membrane and articulate proximally and distally like radius and ulna
o difference- tibiofibular joints allow essentially no movement- bones of leg less flexible, but stronger than forearm
o tibia- articulates proximally to form modified hinge joint of knee, distally with tallus of foot and ankle
o fibula- does not contribute to knee joint, just helps stabilize ankle
o tibia- takes weight of body from femur and transmits to foot, 2nd only to femur in size and strength, “shin bone”
o fibula- sticklike bones, slightly expanded ends, articulates with tibia
 does not bear weight but several muscles attach to it
o Feet- 2 functions- supports body weight and acts like a lever to propel body forward
o a single bone could work for this, but would adapt poorly to uneven surfaces, segmentation makes foot pliable
o Tarsus, metatarsus, and phalanges
o Tarsus- tarsal bones- posterior half of foot
 Body weight carried by 2 largest tarsals= talus and calcaneous
 Talus articulates with tibia and fibula superiorly at trochlea of talus
 Calcaneous= heel bone, carries talus on superior surface (with a shelf structure)
o Calcaneal or Achilles tendon- attaches calf muscles to posterior surface of calcaneous
o Calcaneal tuberosity touches ground
o Metatarsus- metatarsals
 5 small long bones, 1-5 from big toe (hallux) in (starts medial unlike hands, but still biggest first)
 more parallel than metacarpals
 1st one is short and thick and rests on seasmoid bones for support
 large head where articulates with phalanges of toes= ball of foot
o Phalanges- 14, much smaller than hand= less nimble
 General= same, 3 in each except hallux, proximal, middle and distal, middle missing in big toe
 Standing immobile for long periods puts extra stress on ligaments and tendons (feet muscles inactive). It
can result in “flat feet” or fallen arches, particularly if overweight. Nunning on hard surfaces without
proper foot wear/arch support can also cause damage.