Appendicular Skeleton: Derivation, Components, and Comparative Anatomy

What is the appendicular skeleton primarily derived from?

Lateral plate mesoderm.

What are the main components of the appendicular skeleton?

Upper and lower extremities, including pectoral and pelvic girdles.

What is the function of the pectoral and pelvic girdles?

They provide connection points to the axial skeleton and transfer mechanical load.

What is the procoracoid?

The anterior part of the coracoid that connects the cranial edge of the sternum to the shoulder joint complex.

How does the pectoral girdle differ in reptiles and amphibians compared to humans?

In reptiles and amphibians, the procoracoid is present, while it is replaced by the clavicle in humans.

What bones make up the forelimb in the pectoral girdle?

Humerus, radius, ulna, carpals, metacarpals, and phalanges.

What are the two types of fins found in fish?

Pectoral fins (anterior) and pelvic fins (posterior).

What characterizes the bony pectoral girdle in fish?

It includes a vertical cleithrum that supports the scapula and may have dermal clavicles.

What are the key features of the tetrapod pectoral girdle in amphibians?

Lost dermal bones, retained endoskeletal elements, and a rudimentary sternum.

How does the pectoral girdle of birds differ from that of reptiles?

Birds have a prococroid process reaching to the sternum and a fused furcula (wishbone).

What is the structure of the mammalian pectoral girdle?

Triangular scapula with a spine ending in an acromion, reduced coracoid, and no articulation with the sternum.

What is the ilium in the pelvic girdle?

The broad upper part of each half of the pelvis.

What is the acetabulum?

The socket of the hipbone into which the femur fits.

What bones comprise the hindlimb in the pelvic girdle?

Femur, tibia, fibula, tarsals, metatarsals, and phalanges.

What is the puboischial plate?

A structure that incorporates the pubis and ischium in the pelvic girdle.

How does the pelvic girdle of amphibians differ from that of reptiles?

Amphibians have a cartilaginous hip bone, while reptiles have an ilium joined to sacral vertebrae.

What is the synsacrum in birds?

The fusion of the ilium and many vertebrae.

What is mammalian digit suppression?

The reduction of individual digits over time, with specific sequences of digit reduction.

Which digit is typically the first to be reduced in mammals?

The pollex (1st digit).

What distinguishes even-toed and odd-toed mammals in terms of digit presence?

Even-toed mammals have the pollex gone and other digits present, while odd-toed mammals retain the 3rd digit.