Chapter 8: The Appendicular Skeleton

appendicular skeleton

bones of the extremities and shoulder and pelvic girdles

pectoral (shoulder) girdle

attaches bones of the upper extremities to the axial skeleton

clavicle

number: 2

description: 

• collarbone

• slender s-shaped bone

articulation:

• sternoclavicular joint: clavicle articulates medially with the manubrium of the sternum

• acromioclavicular joint: clavicle articulates laterally with acromion process of scapula

scapula 

number: 2

description:

• shoulder blade

• flat triangular bone in dorsal thorax

  • special features:

    • borders: superior, medial (vertebral), lateral (axillary)

    • spine: sharp diagonal ridge on posterior surface

    • acromion process: expanded process at lateral end of spine

    • coracoid process: hook-like process on lateral end of spine

    • glenoid cavity: depression below acromion (arm socket)

articulation:

• acromioclavicular joint: acromion process of scapula articulates with clavicle

• shoulder joint: glenoid cavity of scapula articulates with head of humerus 

humerus 

number: 2

description: 

• long bone of upper arm

  • special features

  • proximal

    • head: rounded enlargement at proximal end

    • greater tubercle: lateral projection distal to head

    • lesser tubercle: projection on anterior surface

    • deltoid tuberosity: roughened area along middle of shaft

  • distal

    • medial and lateral epicondyles: rough projections on either side

    • capitulum: rounded knob below lateral epicondyle on anterior surface

    • trochlea: pulley like process on anterior surface

    • coronoid fossa: depression on anterior surface above trochlea

    • olecranon fossa: depression on posterior surface above trochlea

articulation:

• proximal

  • humerus articulates with glenoid cavity of scapula

• distal

  • capitulum of humerus articulates with head of radius 

  • trochlea of humerus articulates with ulna

ulna

number: 2

description:

• medial bone of forearm

  • special features:

  • proximal

    • olecranon process: superior process that forms point of elbow

    • coronoid process: anterior projection

    • radial notch: lateral depression

  • distal

    • head

    • styloid process: short pointed process

articulation:

• proximal

  • coronoid process and olecranon process of ulna articulate with trochlea of humerus

• distal

  • ulna articulates with carpals

radius 

number: 2

description: 

• small lateral bone of forearm

  • special features

  • proximal

    • head: flat, disc shaped process

  • distal

    • styloid process: pointed lateral projection

articulation:

• proximal

  • head of radius articulates with capitulum of humerus

  • head of radius articulates with radial notch of ulna

• distal

  • radius articulates with carpals

carpals 

number: 16

description: 2 rows of 4 bones each (wrist)

articulation:

• proximal

  • carpals articulate with radius and ulna

• distal

  • carpals articulate with metacarpals

metacarpals

number: 10

description: long bones forming palm

articulation:

• proximal

  • metacarpals articulate with carpals

• distal

  • metacarpals articulate with proximal phalanges of finger 

hand phalanges 

number: 28

description: bones of the finger; 3 per finger, 2 per thumb (pollex)

articulations:

• proximal

  • proximal phalanges of fingers articulate with metacarpals

pelvic girdle

attaches bones of lower extremities to the axial skeleton

hip bone (coxal or pelvic bone)

number: 2

description: 

• hip bones

• fusion of three bones 

  • ilium: flat flaring superior region

  • ischium: lower posterior portion

  • pubis: medial anterior portion

    • special features:

      • acetabulum: hip socket. depression where ilium, ischium and pubic bone have fused

      • obturator foramen: large hole; covered by fibrous membrane in body

articulation:

• anterior

  • pubic symphysis: anterior joint between pubic bones

• posterior

  • sacroiliac joint: ilia articulate posterior with the sacrum

• lateral

  • hip joint: acetabulum of hip bone articulates with the head of the femur

pelvis 

basin like structure formed by the union of the hip bones with sacrum and coccyx

imaginary line

sacral promontory to pubic symphysis

superior = false pelvis

inferior = true pelvis

why are the differences in a male and female pelvis necessary?

adaptions for child brith

male pelvis

increased curvature of sacrum and coccyx = makes pelvic outlet smaller

• <90 degrees

female pelvis 

enlarged pelvic outlet and ilia project laterally. this shape helps to support a growing fetus and allows for delivery 

• >100 degrees 

femur

number: 2

description:

• thigh bone

  • special features

  • proximal

    • head: rounded upper end

    • fovea capitis: small pit in head

    • neck

    • greater trochanter: large process lateral to head

    • lesser trochanter: small process medial to head

    • linea aspera: sharp ridge on posterior surface

  • distal

    • medial and lateral condyles: expanded processes

articulation:

• proximal

  • head of femur articulates with the acetabulum of the hip bone

• distal

  • medial and lateral condyles of femur articulate with tibia

  • medial and lateral condyles of femur articulate with posterior surface of patella

patella 

number: 2

description: 

• knee cap

• small triangular bone

• a sesamoid bone embedded in the tendon of the quadriceps femoris muscle group

articulation:

• articulates with the medial and lateral condyles of the femur

tibia

number: 2

description:

• shinbone

• large medial bone of leg

  • special features

  • proximal

    • medial and lateral condyles: large bulging processes at proximal end

    • tibial tuberosity: rough region between medial and lateral condyles

    • anterior crest: sharp vertical ridge on anterior surface

  • distal

    • medial malleolus: sharp medial process

articulation:

• proximal

  • medial and lateral condyles of tibia articulate with medal and lateral condyles of femur

  • tibia articulates with fibula 

• distal

  • tibia articulates with fibula 

  • tibia articulates with tarsal bone

fibula

number: 2

description: 

• thin lateral bone of lower leg

  • special features

  • proximal

    • head

  • distal

    • lateral malleolus

articulation:

• proximal

  • head of fibula articulates with lateral condyle of tibia below the knee

• distal

  • lateral malleolus of fibula articulates with talus

  • fibula articulates with tibia

tarsals

number: 14

description: 

• ankle bones

• talus: superior bone

• calcaneous: heel bone

articulation: 

• proximal

  • talus articulates with tibia an fibula

• distal

  • tarsals articulate with metatarsals

metatarsals 

number: 10

description: 

• instep

• long bones of foot

articulation:

• proximal

  • metatarsals articulate with tarsals

• distal

  • metatarsals articulate with phalanges of toes

foot phalanges 

number: 28

description:

• toe bones

• 2 per big toe (hallux)

• 3 per other toes 

articulation:

• proximal

  • phalanges articulate with proximal metatarsals

arches of the foot

two arches - held by tendons and ligaments 

longitudinal arch

from calcaneus to distal end of metatarsals

transverse arch

follows joints between tarsals and metatarsals 

what purpose do the arches of the foot serve?

• shock absorption

• balance

• transfer of weight when walking