The Appendicular Skeleton

THE SKELETAL SYSTEMThe Appendicular Skeleton

2 pairs of limbs and 2 girdles Pectoral (shoulder) girdle attaches upper limbs Pelvic (hip) girdle secures lower limbs 3-Segmented limbs

Upper = arm Arm Forearm Hand

Lower = leg Thigh Leg Foot

Pectoral Girdle(Shoulder Girdle)

Clavicle – anterior: collar boneSternal end attaches to the manubrium

mediallyAcromial end articulates with the scapula

laterally Scapula – posterior: shoulder blade

Scapulae: triangular, paired, but don’t connect in back (adds thoracic flexibility)

Scapula

Glenoid cavity articulates with the humerus

Acromium articulates with clavicle

Coracoid process projects anteriorly

Upper extremity

Arm or Brachium = upper arm Between shoulder

and elbow (humerus) Forearm or

Antebrachium Radius & ulna

Hand includes: Wrist (carpus) Palm (metacarpus) Fingers (phalanges)

Arm Humerus is the only

bone Head of humerus fits

into glenoid cavity of scapula

Distal & medially, trochlea articulates with the ulna

Distal & laterally capitulum articulates with the radius

Medial & lateral epicondyles

Right humerus, anterior view

Right humerus, posterior view

Forearm

2 bones: articulate with each other proximally and distally

Interosseous membrane between them

Ulna Olecranon hinges with the

humerus forming elbow Styloid process distally

Radius Contributes to wrist joint Styloid process anchors a

ligament to wrist (thumb side)

Radius is thinner proximally, like a spool of thread, and wide distally; ulna is slightly longer and looks like a monkey wrench (supposedly!)

Right forearm bones, anterior view

Right forearm bones, posterior view

In the anatomical position, the radius is lateral (thumb side); with pronation the palm faces posteriorly and the bones cross

Left forearm

Prone: body lying face downSuppine: body lying face up

(you can remember prone if you think about how you would fall forward onto your face if you passed out)

Anatomical position

prone

pronation moves the forearm into the prone position and supination moves it back to the anatomical position

proximal ulna

Proximal and distal joints of the forearm

Hand Proximal is “wrist” – 8 carpal bones Palm of hand - 5 metacarpals Fingers (or digits) consist of miniature long bones called

phalanges: thumb (“pollex”) has 2; fingers have 3: proximal, middle, distal

Right hand, 2 views:

Pelvic Girdle (Hip Girdle)

Strongly attached to axial skeleton (sacrum) Deep sockets More stable than pectoral (shoulder) girdle Less freedom of movement Made up of the paired hip bones

“Bony pelvis” is basin-like structure: hip bones plus the axial sacrum and coccyx

Hip bone (os coxae): 3 separate bones in childhood which fuse

Ilium

Ischium

Pubis

Ilium Iliac crest Anterior

superior iliac spine

Greater sciatic notch

Forms part of “acetabulum” (hip socket) which receives ball-shaped head of femur

ilium

ilium

Ischium

Body Ramus Ischial spine Ischial

tuberosity Part of socket

ischium

ischium

Pubis Joins

medially in pubic symphysis

Forms “obturator foramen” (large hole) with ischium

Part of socket

pubis

pubis

Hip bones with labels

Ligaments

False (greater) andtrue (lesser) pelvis

Pelvis and childbearing Male/female differences

Large & heavy vs light & delicate Heart shaped pelvic inlet vs oval Narrow deep true pelvis vs wide & shallow Narrow outlet vs wide Less than 90 degree pubic arch vs more than 90

degree Birth canal changes shape as baby descends:

head turns ¼ Higher: pelvic inlet (brim) - side to side largest Lower: pelvic outlet - largest in AP direction

Lower limb

Thigh: femur

Leg (lower leg)TibiaFibula

Foot

Thigh

Femur is largest, longest and strongest bone in the body

Head fits in socket (acetabulum) of pelvis

Neck is weakest Greater trochanter Distal: lateral & medial

condyles and epicondyles Patella: sesmoid bone

Right femur, anterior view

Right femur, posterior view

Leg Tibia: shin bone

Medial and lateral condyles

Tibial tuberosity Distal medial malleolus

(medial ankle) Fibula

Distal lateral malleolus (lateral ankle)

Interosseous membrane

Right lower leg, anterior view

Foot Tarsus: 7 tarsal bones

Talus: articulates with tibia and fibula anteriorly and calcaneus posteriorly

Calcaneus: heel bone Smaller cuboid, navicular,

and 3 cunieforms (medial, intermediate and lateral)

5 metatarsals 14 phalanges

Great toe is hallux

Right foot, superior (dorsal) view and inferior (plantar) view

Right foot, lateral and medial views

Arches