skeletal system 3

Skeletal System 3

Honors Anatomyto copy edition

The Appendicular Skeleton

The Pectoral Girdle(Shoulder)

• 2 pectoral girdles• attach bones of upper limbs to

axial skeleton• each: 1 clavicle• 1 scapula

Clavicle • S-shaped, (medial ½ convex

anteriorly, lateral ½ concave anteriorly) slender bone

• lies horizontally across anterior thorax superior to 1st rib

Clavicle • medial end = sternal end is

rounded & articulates with the manubrium @ sternoclavicular joint

Clavicle • lateral end = acromial end is flat• articulates with acromion of the

scapula to form acromialclavicular joint

Clavicle • last bone to stop growing• 1 of most frequently fx’d bones

(2 curves) usually from fall on outstretched arm

• or see compression fx in auto accidents from shoulder strap which can cause damage to median n. (between clavicle & 2nd rib)

Scapula • aka shoulder blade, angel bone• large, triangular, flat bone• in superior part of posterior thorax

between levels of 2nd & 7th ribs

• spine: prominent ridge that runs diagonally across posterior surface

Scapula • lateral edge: acromion a

flattened expanded process, easily felt as hi pt of shoulder (tailors use it as landmark to measure length of arm)

• glenoid cavity: inferior to acromion, smooth, shallow depression that accepts head of humerus in shoulder joint

Upper Limb• 6 parts:1. Humerus2. Ulna3. Radius4. Carpals5. Metacarpals 6. Phalanges

• Joints:• Shoulder• Elbow• Wrist• Hand

Humerus • longest & largest bone of upper

limb• articulates proximally with

scapula & distally with ulna & radius

• head: rounded proximal end»articulates with glenoid cavity of scapula to form glenohumeral joint

Humerus• distal end:• capitulum: rounded knob on

lateral aspect that articulates with head of radius

• trochlea: medial to capitulum, spool-shaped, articulates with ulna

Ulna • medial aspect of forearm• longer than radius• proximal end: olecranon

(prominence in elbow)• distal end: head, styloid process

(posterior)

Radius• lateral aspect of

forearm• proximal end:

head of radius: articulates with capitulum

• distal end: styloid process (palpable proximal to thumb)

Ulna & Radius• connect @ 3

places1. interosseous

membrane2. proximal end3. distal end

Carpals • proximal to the

hand, distal to radius & ulna

• 8 small bones joined by ligaments

• articulations w/each other called intercarpal joints

Metacarpals

Phalanges • 14 bones of the digits (each

hand)• #’d I to V beginning with thumb• thumb is the pollex has only 2

phalanges, other digits have 3• joints between phalanges called

interphalangeal joints

Pelvic Girdle• 2 hip bones (os coxa) which

unite anteriorly at pubic symphysis and posteriorly with the sacrum @ sacroiliac joint

Pelvic Girdle• Functions:• provides sturdy

support for vertebral column

• connects lower limb to axial skeleton

Newborn Pelvis• 3 bones on each

side:1. Ilium– superior

2. Pubis– anterior &

inferior3. Ischium • posterior &

inferior

Ilium • largest of the 3 hip bones• distinguishing features:1. Iliac Crest• along superior surface1. Sacroiliac Joint (SI Joint)• between sacrum and ilium

Ischium • ramus of ischium fuses with

pubis• distinguishing features:

1. Ischial Tuberosity• what you feel when someone

sits on your lap

Pubis • Acetabulum – formed by ilium, ischium, & pubis– is the “socket” half of the hip joint

• Pubic Symphysis– joint between the 2 hip bones

True Pelvis/ False Pelvis• Pelvic Brim: line that

distinguishes between true & false palvis

Male Pelvis• generally male bone heavier &

stronger & have larger surface marker (because larger muscles attach)

• Pelvis:– deeper false pelvis, smaller, narrower– pelvic brim heart-shaped– acetabulum larger, faces posterior– obturator foramen round

Female Pelvis• generally bones lighter & thinner• Pelvis:– false pelvis shallow, widers– pelvic brim larger, more oval– acetabulum smaller & faces

anterior– obturator foramen oval

Lower Limb• 30 bones in each:• 1 femur• 1 patella • 1 tibia• 1 fibula• 7 tarsals• 5 metatarsals• 14 phalanges

Femur • longest, heaviest, & strongest

bone in the body• proximally articulates with the

acetabulum to form hip joint–Head of the Femur: “ball” part of

joint• small, central depression: fovea capitis

– Greater Trochanter• prominence felt & seen @ side of hip

Patella (kneecap) • small, triangular, sesamoid bone• develops in tendon of quadriceps

femoris muscle• Parts:• Base: broad, superior end• Apex: pointed, inferior end

Tibia “shin bone”larger, medial, weight-bearing

bone of lower legproximally articulates with femur

& fibuladistally articulates with fibula &

tarsals

Tibia • medial malleolus

forms prominence that is palpable & visible on medial ankle

Fibula • parallel & lateral

to the tibia & considerably smaller

• head of fibula on proximal end

• lateral malleolus at distal end

Tarsals• 7 bones:• 1 calcaneous: heel bone, largest

of the tarsals

Metatarsals

• 5 bones between tarsals & phalanges

• #’d I to V from medial lateral

Arches of the Foot• 2 arches in foot: 1. allows the foot to support

weight of body by distributing weight over the soft & hard tissues

2. provide leverage while walkingfully developed by age 12 - 13

Arches of the Foot• 2 longitudinal

arches (medial & lateral

• 1 transverse arch

Development of the Skeletal System• all skeletal tissue arises from mesoderm

• 1st bone: skull in 4th wk• U/S ~ 24 – 25 wks:

Medical Terminology1. Clubfoot:– inherited deformity in which baby is

born with foot twisted inferiorly & medially

– 1/1000 births– tx: casts or wraps, surgery may be

indicated

Medical Terminology2. Genu valgum:• knees

abnormally close together with increased space between ankles

• aka “knock-knee”