Appendicular Skeleton
1. Explain the differences between the male and female pelvis
2. Explain how the structure of specific bones of the appendicular skeleton are suited to the function they perform

1. Explain the differences between the male and female pelvis

external image pelvis2.gif

pubis symphysis
pubis symphysis

Link to website with skeletal system animations, including male and female pelvis differences

The Female Pelvis:
There are significant differences in the anatomy of the pelvis in the female and male. The female pelvis is more delicate, wider than, and not as high as the male pelvis. The angle of the female pubic arch is wide and round. This rounded shape allows for more drastic stretching of the pubic symphysis. This piece of cartilage connects the left and right halves of the pubic bone. During childbirth, the ability for the pubic symphysis to stretch can slightly enlarge the birth canal, facilitating the passage of the child. The female sacrum is wider than the male's and the iliac bone is flatter. The female's coccyx tends to be smaller than the male's, and not as inwardly sloped. This allows it to stay out of the way during childbirth. Along with the coccyx, the acetabulum of the female is also curved less inward as to avoid getting in the way of the child. The pelvic basin of the female is more spacious and less funnel-shaped.
The Female Pelvis is located in the lower part of the abdomen between the hip bones in the female and is part of the appendicular skeleton. It is made of mainly spongy bone inside with an outer layer of compact bone.
The form of the Female Pelvis is particularly suited to its function of accommodating the fetus during pregnancy and permitting the baby to be born as it is wider and has an inner cavity of greater size. For this reason it is shaped differently than the Male Pelvis.

The Male Pelvis:
The male pelvis is more robust, narrower, and taller than the female pelvis. The angle of the male pubic arch is closer to 50-60 degrees and the sacrum is curved inward more. The male pelvis is naturally thicker and stronger to support the naturally heavier mass of a male. The "true" pelvis is narrow and deep, more conical in shape.

2. Explain how the structure of specific bones of the appendicular skeleton are suited to the function they perform

external image 99192-004-234CDC7F.jpg One major bone that is found in the appendicular skeleton is the femur. The femur is the only bone in the upper leg, and that means it must be extremely supportive to keep us walking. Therefore, the femur is the largest and one of the strongest bones of the human body. The shaft of the femur consists of hard compact bone that gives it a lot of support. Furthermore, the shaft is slightly curved so it can dissipate the tremendous force applied when we walk and run. As mentioned earlier, the femur is the only bone connecting the leg to the pelvis. Thus, it must have a special articulation to enable us to walk, run, and jump. The proximal end of the femur contains a ball and socket joint. With this joint, we are able to do so many different activities in a variety of different motions.

Long Bones:
Epiphysis - spongy bone surrounded by thin layer of compact bone; articulation and movement
Diaphysis - consists of mainly compact bone; strength/support, rhymes with epiphysis.
Articular Cartilage- surrounds end of bones to reduce friction and allow gliding between bones
Periosteum - nutrient sheath; protects and nourishes bone
Cancellous Bone - network of trabeculae; strength
Compact bone - many cylinders; strength
Medullary Cavity - cavity of the diaphysis. It contains marrow: red in the young, turning to yellow in many long bones in maturity. It is lined by endosteal tissue (thin connective tissue with many osteoprogenitor cells).
Red Marrow - red, gelatinous substance composed of a red and white blood cells in a variety of developmental forms (hematopoietic tissue) and specialized capillaries (sinusoids) enmeshed in reticular tissue. In adults, red marrow is generally limited to the sternum, vertebrae, ribs, hip bones, clavicles, and cranial bones. very common in young children.
Yellow Marrow - yellow, fatty connective tissue and no longer productive of blood cells. It replaces red marrow in the epiphyses and medullary cavities of long bones, and cancellous bone of other bones

Shoulder Blades (Scapulae)
The shoulder blade is a flat triangular bone which stretches from the shoulder to the vertebral column at the back. On the back side it has a bony ridge for the attachment of the muscles. The bony ridge forms a prominent projection, the acromion, above the shoulder joint. Beneath the collar bone and just on the inside of the shoulder joint, is another bony projection of the shoulder blade, the coracoid process, which also serves for the attachment of muscles. The upper outer corner of the shoulder blade ends in the glenoid cavity into which fits the head of the upper arm bone, forming a ball and socket joint.
Collar Bones (Clavicles)
Each collar bone is rod-shaped and roughly S-shaped. It lies horizontally and articulates with the upper end of the breastbone, right in the middle and front, just above the first rib. The lateral end articulates with the acromium. Collar bones serve as a support for the shoulder blades in front and keep the shoulder blades back so that the arms can hang freely at the sides of the body. They prevent the pectoral girdles from getting out of joint easily and ample movement of the shoulders.
The Wrist
The wrist consists of eight carpal bones; the scaphoid, the lunate, the triquelateral, the pisiform, the trapezium, the trapazoid, the capitate, and the hamate. These are small, short bones that are arranged in two rows of four. They have articulating facets which allow them to slide over one another. This allows us to move our wrist in a wide variety of ways, and makes it a very versatile joint.
The Palm of the Hand
The palm is supported by five long metacarpals. The metacarpals articulate with carpals at one end and with the phalanges at the other end.
The Fingers
The fingers are made up of fourteen phalanges. There are three phalanges in each finger but only two in the thumb. Because there are several phalanges, the fingers are able to curve in more than one way. This allows humans to grip objects with relative ease. If there were only two phalanges in all of the fingers, we would be much more limited in the kinds of tasks we can perform.
The Pelvic (Hip) Girdle
The pelvic girdle consists of two large, sturdy hip bones. Each hip bone consists of three fused bones namely the ilium, ischium and the pubis. The ilium is the largest of the three and forms the upper part of the hip bones. The sacrum fits like a wedge posteriorly between the two hip bones. The sacrum has a large, flat articular surface on each side for articulation with the ilia. The ischium forms the inferior part of the hip bone and the pubis the central in front. The two pubic bones are attached in the middle, on the front side by a symphysis which consists of fibrocartilage and ligaments, the pubic symphysis. The two hip bones and the sacrum form a complete bony ring, the pelvis . On the outer side of the point where the fused bones meet, there is a deep hip socket into which the head of the femur fits.
The pelvic girdle forms a strong support for the attachment of the limbs. Strong muscles of the back, the legs and the buttocks are attached to it. It protects some of the internal organs. In females it forms a strong basin-like structure for supporting and protecting the developing foetus during child-bearing.

The Ankle
There are seven short, thick tarsal bones, the largest of which is the heel bone (calcaneum), which presses firmly onto the ground when one stands, walks or runs. The calf muscles and achilles tendon are attached to the calcenum, allowing the heel to be lifted during locomotion.
The Arch of the Foot
The arch is formed partly by some of the tarsals but mainly by the five long metatarsals, which extends from the tarsals to the toes. The arch is modified for receiving the weight of the body. some people can have excessively high arches or too shallow arches.