The Appendicular Skeleton

The Appendicular Skeleton

The Appendicular Skeleton • 126 bones • Limbs (appendages) • Pectoral girdle (attaches arm to the axial skeleton) • Pelvic girdle (attaches leg to the axial skeleton)

The Pectoral (Shoulder) Girdle • Composed of two bones • Clavicle - collarbone • Scapula – shoulder blade

The Pectoral (Shoulder) Girdle • These bones are very light and allow the upper limb to have exceptionally free movement because: • Each pectoral girdle attaches to axial skeleton at only 1 point = sternoclavicular joint • The loose attachment of the scapula allows it to slide back & forth against the thorax • The glenoid cavity is shallow & the shoulder joint is poorly reinforced by ligaments

Bones of the Shoulder Girdle Figure 5.20a–b

The Pectoral (Shoulder) Girdle • Consists of 2 bones • Clavicle (collar bone) = slender, double curved bone • Attaches to manubrium of the sternum medially & to the scapula laterally • Acts as a brace to hold the arm away from the thorax & helps prevent shoulder dislocation

The Pectoral (Shoulder) Girdle • Scapula (shoulder blade) = triangular & flare when we move our arms posteriorly (“wings”) • Not directly attached to axial skeleton; held in place by trunk muscles • Flattened body w/ 2 processes: • Acromion process • Coracoid process

The Pectoral (Shoulder) Girdle • Acromion process = the enlarged end of the spine of the scapula • Connects w/ the clavicle @ the acromioclavicular joint • Coracoid process = beaklike • Points over the shoulder & anchors some of the arm muscles • Suprascapular notch serves as a nerve passageway

The Pectoral (Shoulder) Girdle • Scapula has 3 borders & 3 angles: • Superior • Medial (vertebral) borders • Lateral (axillary) • Superior • Inferior Angles • Lateral

Bones of the Shoulder Girdle Figure 5.20c–d

Bones of the Upper Limb (30) • The arm is formed by a single bone • Humerus • Rounded proximal end fits into glenoid cavity of scapula Figure 5.21a–b

Bones of the Upper Limb (30) • Opposite of the head – 2 bony processes = greater & lesser tubercles, sites of muscle attachment • Midpoint of shaft – deltoid tuberosity where the deltoid m. attaches Figure 5.21a–b

Bones of the Upper Limb (30) • Radial groove runs obliquely down the posterior shaft • Distal end – medial trochlea (looks like a spool) & lateral ball-like capitulum – both articulate w/ bones of forearm Figure 5.21a–b

Bones of the Upper Limb (30) • Above the trochlea anteriorly is a depression – coronoid fossa • On posterior surface is the olecranon fossa • Both are flanked by medial & lateral epicondyles Figure 5.21a–b

Bones of the Upper Limb • The forearm consists of the radius and the ulna. • Radius is lateral when the arm is in the anatomical position (on the thumb side) & the ulna is medial • When the hand is rotated, the distal end of the radius crosses over & ends up medial to the ulna. Figure 5.21c

Bones of the Upper Limb • Radius & ulna articulate @ small radioulnar joints • They are connected along their entire length by a flexible interosseous membrane • Both have a styloid process @ their distal end Figure 5.21c

Bones of the Upper Limb • Disc-shaped radial head forms a joint w/ the capitulum of the humerus. • Below the head is the radial tuberosity where tendon of biceps m. attaches. Figure 5.21c

Bones of the Upper Limb • On the ulna’s proximal end are the anterior coronoid process & the posterior olecranon process, which are separated by the trochlear notch. • These 2 processes grip the trochlea of the humerus in a pliers-like joint. Figure 5.21c

Bones of the Upper Limb • Hand consists of carpals, metacarpals & phalanges • 8 carpals arranged in 2 irregular rows of 4 bones each form the part of the hand called the carpus (wrist) • Bound together by ligaments that restrict movements between them. Figure 5.22

Bones of the Upper Limb • Metacarpals form the palm • Numbered 1 to 5 from the thumb to the pinky • Clenched fist – heads of the metacarpals = knuckles • Phalanges (14) are the finger bones (3 in each finger & 2 in the thumb) Figure 5.22

Bones of the Upper Limb • Carpals starting Left to Right (pinky to thumb - both rows): • Joe took a Hamate and hit poor Pete in the Capitate, breaking it into a Trapezoid and Trapezium. He did it b/c he was Pisiform(d) Triquetral times. The Judge said he was Lunate and sent him to the Scaphoid. Figure 5.22

The Bony Pelvis vs. the Pelvic Girdle • Bony Pelvis • Composed of: • Sacrum • Coccyx • Coxal bones (coxae) or ossa coxae (Hip bones) • Pelvic Girdle • Coxae are composed of 3 pair of fused bones • Ilium • Ischium • Pubic bone

The Bony Pelvis Figure 5.23a

The Pelvic Girdle: Right Coxal Bone Figure 5.23b

The Pelvic Girdle • Coxae are large, heavy & attached securely to the axial skeleton. • Sockets that receive the femur are deep & heavily reinforced w/ ligaments. • Function = bearing weight; total wt. of upper body rests on pelvis. • Reproductive organs, bladder & part of large intestine lie within & are protected by pelvis.

The Pelvic Girdle • Each coxais formed by the fusion of 3 bones: • Ilium (Large flaring bone - forms most of the coxa) • Connects posteriorly w/ sacrum @ the sacroiliac joint. • Alae - winglike portions of the ilia. • Iliac crest – upper edge of alae that ends anteriorly in the anterior superior iliac spine & posteriorly in the posterior superior iliac spine w/ small inferior spines located below these.

The Pelvic Girdle • Ischium (“sit down bone”) • Most inferior part of coxa. • Ischial tuberosity, a roughened area, receives body wt. when sitting. • Ischial spine, superior to the tuberosity, narrows the outlet through which the baby passes during childbirth. • Greater sciatic notch allows blood vessels & the large sciatic nerve to pass from the pelvis posteriorly into the thigh.

The Pelvic Girdle • Pubis or pubic bone • Most anterior part of the coxa. • Fusion of the rami of the pubis anteriorly & the ischium posteriorly forms a bar of bone enclosing the obturator foramen, an opening through which blood vessels & nerves pass into the anterior part of the thigh. • Pubic bones fuse anteriorly to form a cartilaginous joint called the pubic symphysis.

The Pelvic Girdle • The ilium, ischium, & pubis fuse @ the deep socket called the acetabulum (“vinegar cup”); it receives the head of the femur.

The Bony Pelvis • Bony pelvis is divided into 2 regions: • False pelvis, superior to the true pelvis, is the area medial to the flaring portions of the ilia. • True pelvis lies inferior to the flaring parts of the ilia & the pelvic brim.

The Bony Pelvis • Dimensions of the true pelvis are important for childbirth – must be large enough for the head to pass. • Outlet is the inferior opening of the pelvis. • Inlet is the superior opening.

Differing Characteristics Between the Male and Female Pelvis • Female inlet is larger & more circular. • Female pelvis as a whole is shallower & the bones are lighter & thinner. • Female ilia flare more laterally.

Differing Characteristics Between the Male and Female Pelvis • Female sacrum is shorter & less curved. • Female ischial spines are shorter & farther apart; thus the outlet is larger. • Female pubic arch is more rounded because the angle of the pubic arch is greater.

Bones of the Lower Limbs • Carry our total body weight when standing = thicker & stronger • The thigh has one bone – Femur (thigh bone) Figure 5.24a–b

Bones of the Lower Limbs • Femur (thigh bone) • Heaviest, strongest bone in the body. • Proximal end has ball-like head, neck and greater & lesser trochanters. Trochanters are separated anteriorly by intertrochanteric line and posteriorly by intertrochanteric crest. Figure 5.24a–b

Bones of the Lower Limbs • Trochanters, inter.-crest & gluteal tuberosity are sites for muscle attachment. • Slants medially as it runs downward to bring knees in line w/ body’s center of gravity. (more noticeable in females b/c of wider pelvis) Figure 5.24a–b

Bones of the Lower Limbs • Distally are the lateral & medial condyles – articulate w/ tibia. (condyles separated by condylar fossa) • Anteriorly on distal end is the patellar surface – forms a joint w/ patella (kneecap) Figure 5.24a–b

Bones of the Lower Limbs • The leg has two bones – tibia and fibula • Connected by interosseous membrane Figure 5.24c

Bones of the Lower Limbs • Tibia (shinbone) • Larger & more medial • At proximal end – medial & lateral condyles (separated by intercondylar eminence) articlulate w/ distal end of femur to form knee joint. Figure 5.24c

Bones of the Lower Limbs • Patellar ligament attaches to tibial tuberosity (anter.) • Distally, a process called medial malleolus forms inner bulge of ankle. • Anterior surface has sharp ridge – anterior border (unprotected by muscle – so you can feel this) Figure 5.24c

Bones of the Lower Limbs • Fibula • Thin & sticklike • Distally - lateral malleolus forms outer part of ankle. Figure 5.24c

Bones of the Lower Limbs • Foot – composed of tarsals, metatarsals & phalanges • Two important fxns.: supports body weight & serves as a lever allowing us to propel body forward when walking,etc. Figure 5.25

Bones of the Lower Limbs • 7Tarsalbones • Weight carried by the 2 largest tarsals: • calcaneus (heelbone) & • talus (lies b/n tibia & calcaneus) Figure 5.25

Bones of the Lower Limbs • 5 metatarsals form the sole • 14 phalanges form the toes (each toe has 3, except the big toe) Figure 5.25

Arches of the Foot • Bones are arranged to form 3 strong arches: • 2 longitudinal (medial & lateral), 1 transverse • Ligaments bind foot bones together • Tendons of the foot muscles help to hold bones in arched position but allow for “springiness” – weak arches are referred to as “fallen arches” or “flat feet” Figure 5.26

The Appendicular Skeleton