Extremities Labs 4-5 Osteology

Lab 4: Upper Limb

The Clavicle and Scapula:

The clavicle (collar bone) is the only bony connection between the upper limb and the trunk; it articulates with the sternum and the scapula. The shaft of the clavicle has anterior (lateral) and posterior (medial) curvatures, which increase its resilience.

The scapula (shoulder blade) is a large, flat triangular bone that slides across the back of the rib cage. It articulates with the head of the humerus at the glenohumeral joint and with the clavicle at the acromioclavicular joint. The scapula has distinctive medial, lateral and superior margins and the following features:

Glenoid fossa – a shallow depression on the scapula that articulates with the head of the humerus.

Supraglenoid tubercle - bump at the top of the glenoid fossa to which the long head of the biceps brachii tendon attaches.

Spine - ridge across the posterior surface.

Acromion - anterolateral projection of the spine that arches over the glenohumeral joint and articulates with the clavicle.

Subscapular fossa - the shallow, concave anterior surface.

Coracoid process - hook-like anterolateral projection.

Suprascapular notch - indentation medial to the coracoid process that allows the passage of nerves and vessels to the posterior surface of the scapula.

The Arm:

The head of the humerus is the large rounded end of the bone that articulates with the glenoid fossa of the scapula to form the shoulder joint.

Just inferior to the head is a constriction, the anatomic neck of the humerus. This circumferential depression in the bone is the site of attachment of the connective tissue that forms the shoulder joint capsule.

On the anterior surface of the humerus, just inferior to the surgical neck, are the greater and lesser tubercles of the humerus, which are raised, roughened areas of bone where muscles attach.

Between the tubercles is the intertubercular groove, which the tendon of the long head of the biceps brachii m. passes through.

Inferior to the tubercles is a circumferential area called the surgical neck of the humerus. This is a region of the bone that is small in diameter relative to the head and the tubercles, and so is the region of the humerus most often fractured.

On the lateral aspect of the humerus, around the mid-shaft of the bone, is a roughened area for attachment of the deltoid m., the deltoid tuberosity.

Recall that the radial n. and the deep brachial a. pass along the posterior surface of the humerus, and sometimes you can find the groove that they form in the bone, the radial groove.

At the distal end of the humerus the bone starts to widen out laterally and medially, forming the lateral and medial supracondylar ridges, which terminate with the lateral and medial epicondyles. The ridges and epicondyles are sites of attachment for many of the forearm muscles, with the medial ridge and epicondyle serving mainly as a site for attachment of flexor muscles, and the lateral ridge and epicondyle serving mainly as a site for extensor muscles.

The smooth articular surfaces of the distal humerus are the trochlea (medially, for articulation with the ulna) and the capitulum (laterally, for articulation with the radius).

Posteriorly the olecranon fossa is a depression that the olecranon process of the ulna fits into when the elbow is fully extended.

The Forearm:

The radius and ulna are the paired bones that form the skeleton of the forearm, and articulate with the humerus proximally and the carpal bones distally. The radius and ulna also articulate with one another, which allows pronation and supination of the forearm. The bones are joined to one another along their length by a thick and inextensible interosseous membrane.

At the proximal end of the radius and ulna, the trochlear notch of the ulna articulates with the trochlea of the humerus, forming the primary joint of the elbow. A shallow depression in the end of the radius also articulates with the capitulum of the humerus, but that articulation bears little weight.

Elbow flexors attach to raised features on the proximal ends of both the radius and ulna. The biceps brachii inserts into the bicipital tuberosity (also called the radial tuberosity) of the radius, and the brachialis inserts into the coronoid process of the ulna.

At the elbow the primary articulation is between the humerus and ulna, but at the wrist the primary articulation is between the radius and the scaphoid bone, and to a lesser degree with the lunate bone (2 of the 7 carpal bones). The carpal bones, or wrist bones, are 7 irregularly shaped bones that collectively bridge the forearm to the hand.

The Hand:

Viewed in cross-section, the carpal bones form a U-shaped passage, the carpal tunnel, that is roofed over by the transverse carpal ligament (flexor retinaculum). This is a tight space with 9 muscle tendons and 1 nerve passing though it, and any inflammation in the carpal tunnel puts pressure on the median n. and can lead to sensory and motor deficit in the hand.

Moving distally, the bones of the palm of the hand are the 5 metacarpals, which are numbered 1 (thumb) to 5 (pinky). The digits (fingers, in the case of the hand), are formed by the phalanges (singular = phalanx). Digit 1 (the thumb) is composed of 2 phalanges (proximal phalanx and distal phalanx), while digits 2-5 are composed of 3 phalanges (proximal phalax, middle phalanx, and distal phalanx).

The joints between the metacarpals and the proximal phalanges are the metacarpophalangeal joints (MCP joints). The joints between the phalanges are interphalangeal joints (IP joints), and digits 2-5 have both a proximal IP joint (between proximal and middle phalanges) and a distal IP joint (between middle and distal phalanges). The thumb has a single IP joint.

Sites of Muscle Attachment:

Lab 5: Lower Limb

The Hip:

Each pelvic bone (os coxa) is formed by three bones (ilium, ischium, and pubis), which fuse during childhood along lines that intersect in the acetabular fossa. The sacrum is not fused to os coxa.

Acetabulum — articular socket on the lateral surface of each os coxa, which, together with the head of the femur, forms the hip joint

Obturator foramen (FIG. 1)— located inferior and anterior to the acetabulum; most of the foramen is closed by a flat connective tissue membrane called the obturator membrane; a small obturator canal remains open superiorly between the membrane and adjacent bone, providing communication between the lower limb and the pelvic cavity for the obturator n., a., and v.

Ilium — the most superior of the os coxa bones; articulates with the sacrum (Figure 35-2)

- - Iliac crest — thickened, superior margin of the ilium that serves as an attachment for muscles and fascia
  - Anterior superior iliac spine — anterior termination of the iliac crest
  - Anterior inferior iliac spine — inferior to the anterior superior iliac spine
  - Posterior superior iliac spine — posterior termination of the iliac crest
  - Iliac fossa — the iliacus muscle sits here

Ischium — the most inferior of the os coxa bones

- - Ischial tuberosity — the most prominent feature of the ischium, a large tuberosity on the posteroinferior aspect of the bone; an important site for lower limb muscle attachments and for supporting the body when sitting
  - Ischial spine — on the posterior margin of the ischium; separates the lesser and greater sciatic notches
  - Ischial ramus — projects anteriorly and superiorly to join with the inferior ramus of the pubis; the ischial ramus and inferior pubic ramus are fused and therefore are often called the ischiopubic ramus or conjoint ramus

Pubis — the most anterior of the os coxa bones

- - Superior pubic ramus — projects laterally and superiorly to join with the ilium; has notches for the external iliac a. and v., femoral n., and iliopsoas m./tendon
  - Inferior pubic ramus — a ramus that projects laterally and interiorly to join with the ramus of the ischium; the inferior pubic ramus and ischial ramus are termed the ischiopubic ramus
  - Pubic symphysis — a fibrocartilagenous pad of cartilage that joins the left and right pubic bones
  - Pubic tubercle — The pubic tubercle is a prominent tubercle on the superior ramus of the pubis bone of the pelvis. The pubic tubercle is the inferior attachment of the inguinal ligament.

The Thigh:

The femur is the longest bone in the body:

The head of the femur is the proximal, spherical structure that articulates with the acetabulum to form the hip joint.

The neck of the femur is the cylindrical strut of bone that attaches the head of the femur to the shaft of the femur. A common site of femoral fracture.

The greater trochanter of the femur is a roughened prominence that extends superiorly from the shaft of the femur just lateral to the region where the neck joins the shaft.

The lesser trochanter of the femur is inferior and medial to the greater trochanter and has a blunt conical shape. It is joined to the greater trochanter by the intertrochanteric crest.

The linea aspera is a roughened crest that runs longitudinally along the posterior surface of the femur.

The medial condyle is the smooth, rounded surface at the distal end of the femur that articulates with the medial condyle of the tibia at the knee joint.

The medial epicondyle is the raised bone just proximal to the medial condyle. The adductor tubercle is a prominent feature of the medial epicondyle.

The lateral condyle is the smooth, rounded surface at the distal end of the femur that articulates with the lateral condyle of the tibia at the knee joint.

The lateral epicondyle is the raised bone just proximal to the lateral condyle.

The Leg:

The patella (kneecap) is the largest sesamoid bone in the body. The patella develops within the tendon of insertion of the quadriceps femoris.

The tibia is the medial and larger of the two bones of the leg, it articulates with the femur at the knee joint.

The medial condyle and lateral condyle of the tibia are expanded surfaces at the proximal end of tibia where the condyles of the femur and tibia articulate.

The tibial tuberosity is a raised area of bone on the anterior, proximal surface of the tibia. Attachment site of the quadricpes femoris mm.

The soleal line (popliteal line) is a roughened oblique line on the posterior aspect of the tibia, for attachment of the soleus m.

The medial malleolus is a bony protruberance on the medial, distal end of the tibia. The bump you can see and feel on the medial aspect of your ankle.

The fibula is the smaller, lateral bone of the leg. It does not bear weight and is not part of the knee joint.

The head of the fibula is the bony expansion at the proximal end of the bone.

The lateral malleolus is the expanded distal end of the bone, the bump you see and feel on the lateral aspect of the ankle.

The Foot:

There are 7 tarsal bones that form the ankle.

The talus is most superior, and articulates with the tibia to form the hinge joint of the ankle.

The calcaneus is the largest of the tarsal bones and form the heel of the foot.

The navicular is medial, and just anterior to the talus, while the cuboid is lateral and just anterior to the calcaneus.

Anterior to the navicular are the 3 cuneiform bones, the medial, intermediate, and lateral.

There are 5 metatarsal bones in the foot. Number 1 is the great toe (hallux) and number 5 is the little toe.

The hallux is composed of 2 phalanges, while the digits 2-5 all are made up of 3 phalanges.

Sites of Muscle Attachment:

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