The Appendicular Skeleton


What is it?

The appendicular skeleton works in conjunction with the axial skeleton to produce the full skeleton that humans need to function. While the axial skeleton provides movement for the skull, vertebrae, and ribs, the appendicular skeleton consists of the girdles and the skeleton of the limbs. The upper body part limbs are attached to the pectoral, or shoulder, girdles. The lower body part limbs are attached to the pelvic, or hip, girdle. Together, these limbs, connected to their respective girdles, provide movement for the body part of the skeleton. the appendicular skeleton enables us to carry out the movements typical for our manipulative lifestyle.

The Pectoral Girdle

The pectoral also known as a shoulder girdle consists of the clavicle anteriorly and the scapula posteriorly.The paired pectoral girdle and their associated muscles form your shoulders. The two shoulder blades(scapulae) a
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courtesy of www.botany.uwc.ac.za/.../appendicular.htm
nd two collar bones(clavicle) articulate with one another, allowing some degree of movement. The pectoral girdles attach the upper limbs to the axial skeleton and provide attachment points for many of the muscles that move the upper limbs.The articulations between the scapulae and the clavicle are what allows us to have the range of upper body movement that we do have. This mobility is due because only the clavicle attches to the axial skeleton, the scapula can move quite freely across the thorax, allowing the arm to move with it. Also movement is possible because the socket of the shoulder joint is shallow and poorly reinforced, so it does not restrict the movement of the humerus.



Scapulae

Scapula is just a technical way of saying shoulder blades, which are flat and triangular and extend from the shoulder to the vertebral external image 432145916_6f9c547ba0.jpg?v=0column on the back. The acromion is a bony protrusion, which can be seen above the joint of the shoulder. Underneath the acromion is a bony ridge which allows the muscles to connect to it. The coracoid process also serves the same purpose as the bottom ridge of the acromion, but it is located just outside of the shoulder joint. The glenoid cavity, on the outer edge of the shoulder blade, is where the head of the upper arm bone connects.
picture of scapula




Clavicles

The clavicles or collar bones, are slender doubly curved long bones that can be felt along the entire course as they extend horizexternal image Clavicle.GIFontally across the superior thorax. Each clavicle is coned shaped at its medial sternal end, which attaches to the sternal manubrium, and flattened at its lateral acromial end which articulates with the scapula. It articulates in the middle and the front of the breastbone, above the first rib. The far end of the clavicle, closest to the arm bones, articulates with the acromion of the scapulae. The clavicles are vitally important because they serve as support for the shoulder blades. Along with support, the clavicles also allow the arms to hang down by keeping the shoulder blades back. Clavicles prevent the pectoral girdles from getting out of place easily and also provide movement for the limbs and shoulders.
picture of a clavicle all pictures from flickr.com or getty images

Humerus

The humerus is a key long bone of the body that makes up the arm of the body. This particular bone also fits in between the ulna and the scapula. The humerus is then divided into three important sections, called the lower extremity, the body, and the upper extremity of the humerus. Each of these three different sections also contain various special markings on them. For example, the upper extremity of the humerus contains the head of the humerus, and also the greater and lesser tubercles. The head of the humerus is essential because it is articulated with the gleniod cavity of the scapula. Nextly, there is the greater tubercle, and it is rounded and marked by three flat impressions located on the upper surface. These also allow the insertion of the supraspinatus, the infraspinatus, and the teres muscle. In the body, there is located several different unique markings such as the deltoid tuberosity and also, the radial groove. The deltoid tuberosity is significant because, it is the site of attachment for the deltoid muscle, and the radial groove marks the path of the radial nerve, an important nerve of the upper limb. Then, in the lower extremity of the humerus there are a number of fossae, and condyles. The the medial trochlea and the later capitulum are two of the most important condyles that articulate with the ulna and the radius. Then there are the different fossae that are received with different types of bones. For example, the radial fossa articulates with the head of the radius, allowing movement to be made in the elbow.


Limbs connected to the Pectoral Girdle

The limbs that are associated with the pectoral girdle are: the humerus, the radius and the ulna, the carpals, the metacarpals, and the philanges
hbones.gif
courtesy of www.pncl.co.uk/~belcher/handbone.htm
in the hands. The humerus is connected to the scapula by the ball and socket joint, which is what allows such a free range of movement for the upper arm. The humerus also articulates with the radius and the ulna to complete the arm bones. The ulna is the larger of the two forearm bones. It is located proximally on the interior side of the forearm. The proximal end of the ulna forms the hinge joint of the elbow, along with the humerus. The distal end of the ulna helps to form the bones of the wrist. The radius is located on the outer side of the forearm, and makes up most of the joint that the carpals attach to. It is the smaller of the two forearm bones and does not play such a major role in the formation of the elbow as the ulna does. The carpals are the bones of the wrist that attach mainly to the radius, although the ulna does have some role in their attachment. The carpals are small and short bones arranged in two rows of four, meaning that there are eight in each wrist. In the anatomical position, starting with the thumb, the first row consists of : scaphoid, lunate, triquestral, and pisiform. The row below that, in anatomical position, consists of : the trapezium, trapezoid, capitate, and hamate bones. The simple way to remember the order of the carpal bones is the saying "Some Lovers Try Positions That They Can't Handle" or, the carpal bones in order of the first letter. After the carpals come the metacarpals, or the bones that make up the palm of the hand. The five metacarpals, one for each finger, articulate proximally with the carpals and distally with the philanges. They are counted from one to five starting with the thumb and ending with the pinky finger. The metacarpals can be found by the knuckles in your wrist. The philanges are what we commonly refer to as our fingers. There are three parts to them, the distal, the middle, and the proximal. The proximal articulates with the metacarpals, the middle with the proximal and the distal, and the distal with the middle.








The Pelvic Girdle- The hip

The pelvic girdle is often referred to as the hip bones. Two sturdy bones (the hip bones) form the girdle that the lower limbs are attached to. The pelvic girdle is also formed by a coxal bone, which consists of the illium and ischium and there is also the pubic bone. They are fused together to make one half of the hip and the sacrum fits in between them to complete the pelvic girdle. The main function of the pelvic girdle is to provide a strong attachment for the lower limbs. Unlike in other places of the body, it creates great stability for the body, and it is much stronger than many of those located in the pectoral girdle, which also has more mobility. Since the lower limbs carry all of the body's weight and the pelvis provides the attachment for those limbs, it has to be strong enough to support them easily. For the some, specifically women, the pelvic girdle is a good deal wider and this plays a significant role in child bearing. The hip bone though is characterized by three different bones, fused together known as the ilium, the ischium, and the pubis. These bones create different regions of the hip and they each have many unique characteristics essential for our body.

Ilium

This particular bone flares outward, also created the superior region of the coxal bone. The ilium crest is also something that could be easily felt because it protrude out from the body. The illium also articulates with the sacrum, through the sacroiliac joints. This is important because the weight of the body is distributed from the spine to the pelvis through these joints. On the ilium, there are also located, many different features. For example, there is the iliac crests, which thickened portions of the outer ilium. Also on the more inferior part of the ilium, there is the greater sciatic notch, through which the sciatic nerve enters the thigh. Also in the same area, there is the arcuate line, which helps to distinguish the margin of the true pelvis.

Ischium

The ischium forms the posteroinferior part of the hip. Similarly to the ilium, the ischium contains a lesser sciatic notchm and this is a place where many nerves and blood vessels pass through, in order to give supplies to the anogenital area of the body. Another important portion of the i schium is the ischial tuberosity. This is important especially when we sit down, because on the ischial tuberosity is where the weight of our body is transfered into. The ischial tuberosity is also important for the attachment of the hamstring muscle onto the posterior thigh.

Pubis

The pubis, or the pubic bone forms the anterior part of the hip bone.It is formed mostly from a superior and inferior rami, which creates a flattened medial body. There is also a pubic crest that is formed from the thickened anterior border of the pubis. This bone is also a main contributor in creating the obturator foraman, which is a large opening formed with the two rami of the pubic bone and the ramus of the ischium. The obturator foramen is essential for which several nerves and blood vessels pass through. Something else that is also formed is the pubic arch, which is formed by the joining of the two pubic bones. This arch is mostly important for helping to differentiate female from male pelves.

Limbs connected to the Pelvic Girdle

The upper leg has only one bone in it- the femur. It is both the largest and strongest bone in the body. It articulates with the acetabulum of the hip to form a ball and socket joint, allowing flexibility of the leg. This ball and socket joint is what allows gymnists and dancers to be flexible enough to do the splits, and other feats such as that. At the distal end of the femur it widens to form two condyles (or knobs) that are the upper part of the patella on the anterior part and the knee joint with the tibia on the posterior part. The patella is the knee, and allows movement of the knee joint. It is a flat bone, small and triangular, that forms on the thigh muscle tendon and attaches to the tibia by ligaments. The tibia is attached to both
pelvic_girdle.jpg
courtesy of bbbob_99 from Flickr.com
the patella and the femur and carries approximately 95% of your body weight. The fibula is a much smaller bone loacted behind the tibia which accounts for carrying the rest of your body weight, about 5%. The tibia is commonly known as the shin bone and articulates with the tarsals as well as the patella. Both the tibia and the fibula play a role in the formation of the tarsals, or the ankle bones. The tibia connects to the front while the fibula connects to the back. The fibula, although it is attached to the tibia and the tarsals, does not attach to the patella, nor does it help to form part of the knee joint. There are seven tarsal bones in each foot that make up the ankle. The largest is the calcaneum, or the heel bone. Calf muscles attach to the calcaneum which allow it to propel the person forwards. Unfortunately, unlike the carpals in the wrist, there is no easy way to remember the tarsals besides simple memorization. The arch of the foot is formed by the metatarsals, the equivalent of the metacarpals. They are counted the same way, starting with one and ending with five from the big toe to the pinky toe. The arch of the foot is designed to help support the weight of the body. Falling arches is the technical term for those people who are flat footed. They have no arch, or it is fallen, thus the name. There are fourteen philanges in each foot. The big toe has two while all the others have three. They are the proximal, those that are attached to the metatarsals; the middle, those that are attached to the proximal and distal both; and the distal, those that are attached only to the middle philanges.

femur.jpg
Picture of femur courtesy of Pepe(Max_Max) from Flickr.com

tibia.gif
Picture of tibia and fibula courtesy of doctorchuckcolumbo from Flickr.com

patella.jpg
Picture of patella courtesy of akeg from Flickr.com