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 places

1. interosseous membrane

2. 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 &

inferior

3. 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 Terminology

2. Genu valgum:• knees

abnormally close together with increased space between ankles

• aka “knock-knee”