W2 - Appendicular Skeleton Flashcards
LO1: Describe the bones of the appendicular skeleton
shoulder girdle
upper limbs
pelvic girdle
lower limbs
Although the bones of upper and lower limbs differ in their functions and mobility, they have the same fundamental organisation: each limb is composed of a girdle and a free portion, which in turn has three regions united by movable joints.
LO1: Describe the bones of the appendicular skeleton (upper limb skeleton)
2 main parts = shoulder girdle and the free upper limb itself.
The shoulder girdle = the set of bones that connects the free portion of the upper limb to the axial skeleton
(clavicle and the scapula)
The free upper limb consists of the three regions:
Arm – includes the humerus
Forearm – includes the radius and ulna
Hand – includes 8 carpals, 5 metacarpals and 5 digits (each of which consists of phalanges)
LO2: Describe the bones of the appendicular skeleton (shoulder girdle)
The medial end of the clavicle articulates with the sternum. This is the only point of articulation between the upper limb and the axial skeleton. The lateral end of the clavicle articulates with the scapula. The scapula, in turn, articulates with the humerus at the shoulder joint. There is no anatomical joint between the thoracic cage and the scapula. Instead, the scapula is held in place by muscles.
Therefore, the shoulder girdle bones form a chain with several segments and articulations prior to the shoulder joint. This significantly increases the mobility of the upper limb. Since only the clavicle attaches to the axial skeleton, the scapula can move quite freely along the thoracic cage, allowing the free upper limb to move with it. Many muscles attach to the bones of the shoulder girdle and allow for the high mobility of this region.
LO3: Describe the bones of the appendicular skeleton (clavicle bone)
The clavicle or ‘collarbone’ can be easily palpated. You can feel its rounded medial or sternal end that articulates with the manubrium of the sternum and its flattened lateral or acromial end that articulates with the acromion of the scapula. If you run your fingers along the clavicle, you will feel that the medial 2/3rd of the clavicle is convex anteriorly and the lateral 1/3rd is concave anteriorly.
The superior surface of the clavicle is smooth while the inferior surface is rough due to the attachment of ligaments and muscles.
LO3: Describe the bones of the appendicular skeleton (anterior scapula)
The scapula is a thin, flat bone aligned against the posterior aspect of the thoracic cage and held in place by many muscles.
Like a triangle, the scapula has 3 angles: superior, inferior and lateral. The lateral angle has a feature called the glenoid fossa, which is a shallow depression for articulation with the humerus at the shoulder joint. Also like a triangle, the scapula has three borders: superior, lateral and medial.
On the anterior surface, the scapula has a large depression called the subscapular fossa where a muscle called subscapularis originates from. This muscle belongs to a group of muscles called the rotator cuff. Projecting anteriorly from the lateral part of the superior border of the scapula is the coracoid process.
LO3: Describe the bones of the appendicular skeleton (posterior scapula)
On the posterior aspect of the scapula, a prominent spine can be identified and this can be palpated. The spine extends laterally as the acromion. Acromion means the apex of the shoulder and this feature can be palpated. The acromion articulates with the lateral or acromial end of the clavicle. The spine separates the posterior surface of the scapula into two fossae: the supraspinous fossa and the infraspinous fossa. Two muscles called supraspinatus and infraspinatus originate from these fossae, respectively. These muscles also belong to the rotator cuff group.
LO3: Describe the bones of the appendicular skeleton (free upper limb, humerus)
Round head at the proximal end and an anatomical neck immediately below it.
Head of the humerus articulates with the glenoid fossa - form shoulder joint.
Proximal end has greater and lesser tubercles (attach to rotator cuff muscles)
The surgical neck of the humerus is located below the tubercles and separates them from the shaft.
Deltoid tuberosity for the attachment of the deltoid muscle.
Distal - two epicondyles (lateral and medial) = attachment sites for many forearm muscles.
Capitulum –> radius (radial fossa) (coronoid notch for coronoid process when elbow is flexed)
Trochlea –> ulna (trochlear notch)
Olecranon fossa –> acommodates olecrannon process with ulna (when elbow is flexed)
LO3: Describe the bones of the appendicular skeleton (free upper limb, radius)
The radius is the lateral bone of the forearm. It has a head at the proximal end and a neck immediately below it. The head of the radius articulates with the capitulum of the humerus at the elbow joint and sits in the radial fossa of the humerus when the elbow is flexed.
On the anterior surface of the radius is a feature called the radial tuberosity, which serves as the attachment site for the tendon of the biceps brachii muscle. The shaft of the radius gradually widens towards the distal end, which forms the articulation at the wrist joint.
LO3: Describe the bones of the appendicular skeleton (free upper limb, ulna)
The ulna is the medial bone of the forearm. The posterior aspect of its proximal end features the olecranon process.
When elbow is fully flexed, the olecranon forms the most prominent point on the posterior aspect. When the elbow is extended, it sits in the olecranon fossa of the humerus. The anterior surface of the proximal end features the trochlear notch, which articulates with the trochlea of the humerus at the elbow joint.
Note the sharp coronoid process of the ulna that sits in the coronoid fossa of the humerus when the elbow is flexed.
Below the coronoid process = ulnar tuberosity = attachment site for the brachialis muscle. Ulna head = distal unlike humerus and radius
LO3: Describe the bones of the appendicular skeleton (free upper limb, articulation of humerus and radius/ulna)
LO3: Describe the bones of the appendicular skeleton (free upper limb, hand)
he bones of the hand include 8 carpals, 5 metacarpals and 5 digits (each of which consists of phalanges).
The 8 carpal bones are arranged in two rows: proximal and distal. The proximal row of carpals articulates with the radius at the wrist joint, while the distal row articulates with the metacarpals.
The metacarpal bones form the palm and dorsum of the hand and are numbered 1 to 5 from lateral to medial. At their distal ends, they articulate with the bones of the digits.
The digits are also numbered 1 to 5 from lateral to medial, therefore starting at the thumb, or ‘pollex’. Each digit consists of three phalanges: proximal, middle, distal; except for the thumb, which has only two phalanges: proximal and distal.
LO2: Describe the bones of the appendicular skeleton (lower limb skeleton)
The two main parts of the lower limb are the girdle (called the pelvic girdle) and the free lower limb.
Similar to the shoulder girdle, which connects the free upper limb to the axial skeleton, the pelvic girdle connects the free lower limb to the axial skeleton.
Free lower limb = three regions
Thigh – includes the femur
Leg – includes the tibia and fibula
Foot – includes 7 tarsals, 5 metatarsals and 5 digits (each of which consists of phalanges).
LO3: Describe the bones of the appendicular skeleton (pelvic girdle)
Pelvic girdle = two hip bones (coxal bones or os coxae).
The two hip bones articulate with each other anteriorly at the pubic symphysis, and with the sacrum posteriorly, forming a continuous bony ring.
In contrast to the pelvic girdle, the bony pelvis includes four bones: the two hip bones, the sacrum and the coccyx.
LO3: Describe the bones of the appendicular skeleton (hip bone)
The hip bone is large and irregularly shaped. It is formed by the fusion of the three bones: the ilium, the ischium and the pubis. During childhood, these are three separate bones united by cartilage at the acetabulum, which is a deep depression for the articulation of the femur to form the hip joint. In adults, the ilium, ischium and pubis are fused.
LO3: Describe the bones of the appendicular skeleton (ilium)
Forms the superior region of the hip bone.
It consists of the body and the ala (wing), which has a prominent ridge called the iliac crest (which anteriorly as the anterior superior iliac spine and posteriorly as the posterior superior iliac spine)
Below each of the superior iliac spines, there are corresponding inferior iliac spines
Lateral surface = the gluteal surface The medial surface = iliac fossa
The medial surface of the ilium has a large articular surface for the sacroiliac joint,
LO3: Describe the bones of the appendicular skeleton (ischium)
Forms posteroinferior region
Shaped like an arch with the body + ramus
Located posterior to the acetabulum is a triangular feature called the ischial spine, which separates two notches: the greater (or superior) sciatic notch above and the lesser (or inferior) sciatic notch below.
Inferior to the lesser sciatic notch is a prominent feature called the ischial tuberosity, which serves as the common origin point of the hamstring muscles.
LO3: Describe the bones of the appendicular skeleton (pubis)
Forms the anterior region of the hip bone.
Body + superior and anterior rami and the inferior ramus.
Pubic tubercle = small round prominence = an attachment point for a ligament called the inguinal ligament that runs in the groin region.
A large hole called the obturator foramen is located between the pubis and the ischium, which is enclosed by a fibrous membrane called the obturator membrane.
LO3: Describe the bones of the appendicular skeleton (free lower limb, femur)
Round head at the proximal end and a neck below it. The neck is positioned at an angle to the shaft of the femur (weakest part)
On the posterior aspect of the proximal femoral shaft, there are two large, rough projections called the greater and lesser trochanters.
Laterally on the posterior aspect of the proximal shaft, there is a feature called the gluteal tuberosity for attachment of one of the gluteal muscles.
Running down the length of the posterior aspect of the shaft is a prominent ridge called linea aspera, which is also for muscle attachment.
LO3: Describe the bones of the appendicular skeleton (free lower limb, tibia)
Medial and weight-bearing bone of the leg.
2 large condyles (medial and lateral) at proximal end, which have two flat articular surfaces superiorly to articulate with the corresponding femoral condyles at the knee joint.
Separating the two articular surfaces is an elevation called the intercondylar eminence that serves for the attachment of ligaments in the knee joint.
Anteriorly, the proximal end of the tibia has a feature called the tibial tuberosity for the attachment of the patellar ligament.
The shaft of the tibia has a sharp anterior border that is palpable together with the medial surface of the tibia, as these features are located subcutaneously, or underneath the skin.
The posterior aspect of the tibia has a prominent line called the soleal line, which is the origin point of a muscle called soleus.
Distally, the tibia widens and has a feature on its medial aspect called the medial malleolus. This can be easily palpated, as it forms the medial bulge at the ankle.
Both the proximal and distal ends of the tibia feature surfaces for the articulation with the fibula.
LO3: Describe the bones of the appendicular skeleton (free lower limb, fibula)
The fibula is the lateral bone of the leg. It is important to note that unlike the tibia, it does not participate in the knee joint. At the proximal end, the fibula has a head that articulates with the lateral tibial condyle. At the distal end, it has a feature called the lateral malleolus that can be easily palpated, as it forms the lateral bulge at the ankle.
The distal ends of the tibia and fibula form the so-called ‘malleolar mortise’, which articulates with one of the tarsal bones called the talus to form the ankle joint.
LO3: Describe the bones of the appendicular skeleton (free lower limb, articulation at the knee joint)
LO3: Describe the bones of the appendicular skeleton (free lower limb, foot)
Divided into three regions: 7 tarsals, 5 metatarsals and 5 digits (each of which consists of phalanges).
The tarsus forms the posterior aspect of the foot and consists of 7 tarsal bones. The two main weight-bearing bones are the talus, which articulates with the malleolar mortise at the ankle joint, and the calcaneus, which forms the heel of the foot.
Anteriorly, the tarsals articulate with the metatarsals. Like the metacarpals in the hand, the metatarsals in the foot are numbered 1 to 5, but this time from medial to lateral. Also like the hand, the metatarsals articulate with the bones of the digits at their distal ends.
Like in the hand, the digits of the foot are numbered 1 to 5, but this time from medial to lateral, therefore starting with the great toe, or ‘hallux’. Each digit consists of three phalanges: proximal, middle and distal; except for the great toe, which has only two phalanges: proximal and distal. This is the same as the digits of the hand.
To support the body weight, the foot is structured so that it is arched upward. There are two longitudinal foot arches and one transverse foot arch. These arches are supported by interlocking bones, strong ligaments and muscle tendons. As a result, the foot arches ‘give’ when weight is applied to the foot, then spring back when the weight is removed, thus supporting the body weight and locomotion.
