The Appendicular Skeleton

The Carpal (wrist) bones

-8 small bones connected to each other by ligaments -they are arranged in 2 rows of 4 bones each -the proximal row (scaphoid, lunate, triquetrum, pisiform) articulates with the distal radius and ulna -the distal row (trapezium, trapezoid, capitate, hamate) articulates with the metacarpals (hand bones)

Clavicle

-S shaped -aka collar bone -lies horizontally across the anterior part of the thorax superior to the first rib -it is subcutaneous (under the skin) and easily palpable along its length -rougher and more curved in males -Its medial (sternal) end articulates with the manubrium of the sternum, and the lateral (acromial) end articulates with the acromion of the scapula

Ulna

-The olecranon and the coracoid process at the proximal end of the ulna form the trochlear notch which wraps around the trochlea of the humerus making up the elbow joint -is located on the medial aspect (pinky side) of the forearm and is longer than the radius

Patella

-a triangular bone that develops in the quadriceps tendon -located anterior to the knee joint -it articulates on its posterior surface with the femur

Tarsus

-ankle -contains 7 tarsal bones, these are: ~the talus ~calcaneous (heel) ~navicular ~3 cuneiform (medial-1st, intermediate-2nd, and lateral-3rd)~the cuboid -the only bone that articulates with the tibia and fibula

Phalanges

-are arranged exactly like those of the hand -the big toe has a proximal and distal phalanx and the other toes have a proximal, middle and distal phalanx

Humerus

-arm bone -the longest and largest bone of the upper limb -it articulates proximally with the scapula (its rounded head fits into the glenoid cavity) distally with two bones, the ulna and radius (the trochlea articulates with the ulna and capitulum with the radius) to form the elbow joint.

Pelvic (hip) girdle

-consists of the two hip bones, also called coxal or pelvic bones -coxal bones articulate with the sacrum posteriorly -each hip bone is made out of 3 individual bones: the ilium, ischium, and the pubis (pubic bone) -the two bones articulate anteriorly at the pubic bones (pubic symphysis) -there is a disc of fibrocartilage between the two bones -the 3 individual bones fuse into one hip bone by the age of 23

Metatarsus

-footbones -made up of 5 metatarsal bones numbered I-V (1-5) starting with the big toe -they make up the sole and dorsal surface of the foot -the proximal ends articulate with the 3 cuneiform bones and the cuboid -the distal ends articulate with the proximal phalanges

The Five Metacarpals

-hand bones -make up the palm and back of the hand -numbered I through V (or 1-5) starting with the thumb -the bases articulate with the distal carpals while their heads articulate with the proximal phalanges

Pelvis

-is divided into a superior and an inferior portion by the pelvic brim which is where the abdomen meets the pelvic cavity The male pelvis is usually longer and heavier The female pelvis is mainly associated with the requirements of pregnancy and childbirth, so it is wider and shallower than the male pelvis

Scapula

-or shoulder blade -is a large, triangular, flat bone situated in the superior part of the posterior thorax between the levels of the second and seventh ribs -its glenoid cavity is the attachment point for the humerus (which is the upper bone)

Fibula

-parallel and lateral to the tibia, but it is considerably smaller -does not articulate with the femur, but it does help stabilize the ankle joint

Tibia

-shin bone -the larger, medial, weight-bearing bone of the leg -articulates at its proximal end with the femur and fibula, and at its distal end with the fibula and the talus bone of the ankle

The Phalanges

-the bones of the digits (fingers) -there are 14 in all -the thumb contains 2 (proximal and distal) -the other 4 fingers contains 3 each (proximal, middle, and distal)

Radius

-the smaller bone of the forearm and is located on the lateral aspect of the forearm (thumb side) -The articulation of its head with the capitulum of the humerus and with the ulna allow the forearm to rotate -narrow at its proximal end and widens at the distal end

Femur

-thighbone -the longest, heaviest and strongest bone in the body -the proximal end (head) inserts into the acetabulum of the hip bone (hip joint) -the distal end articulates with the tibia (shinbone) (knee joint) and patella (kneecap)

Two arches of the foot

1. the longitudinal arch 2. transverse arch

Pectoral (shoulder) girdles

Attaches the bones of the upper limbs to the axial skeleton -Each of the 2 pectoral girdles consists of a clavicle and a scapula -These girdles do not articulate with the vertebral column and are held in position and stabilized by a group of large muscles that extend from the vertebral column and ribs to the scapula

Most of the skull arises from the outer layer called the ______.

Ectoderm

Skull bones develop in 2 ways:

The neurocranium forms the bones of the skull itself. It is divided into the cartilaginous neurocranium (hyaline cartilage that undergoes endochondral ossification) and the membranous neurocranium that undergoes intamembranous ossification

The bones of the face form from the _____.

Viscerocranium

Most skeletal tissue arises from the middle primary germ layer in embryos know as the ___________.

Mesoderm