Using the Sectra table, you will identify the structures of the forearm and hand. Bolded terms are in the objectives for this lab.
The upper limb
“The upper limb is divided into four regions: shoulder (pectoral girdle), arm (brachium), forearm (antebrachium), and hand (manus). The upper limb is structured for mobility so we can place our hands, which are grasping organs, in a large area of space. Some of the muscles that control the upper limb are extrinsic, meaning they extend into the other regions of the body, specifically the anterior thorax and the back.” – Grant’s Dissector 16th ed.
Review the bones of the upper limb in the VH Dissector:
- Identify bones of the forearm and hand: radius, ulna, carpals, metacarpals, and phalanges
- Rotate the model image with one finger, or use two fingers to move the image around and zoom in and out
Q1: What joint is affected in a patient with nursemaid’s elbow (be specific)? (answer)
As you highlight a muscle, note that the muscle will also be highlighted in the multiplanar reconstructed (MPR), or cross-sectional images in the leftmost pane. All structures should be identified on the MPR images. Using three fingers, scroll through the MPR images to understand the three-dimensional relationships between different structures as you work though the lab. Structures that are difficult to identify in the MPR images will have additional links to assist you.
Note that the upper limbs of the model are not in anatomical position, but in a more natural resting position. As you work through the lab activity, make sure you are correctly identifying the position of structures relative to correct anatomical position. As certain points in this lab, you’ll notice the axes of the MPR images have been shifted to show you views in the correct transverse, sagittal, and coronal planes.
Superficial veins of the upper limb
Begin your virtual dissection by using the left upper limb of the model (select this button at any time to start over):
As you identify and dissect muscles, you should review their origin, insertion, innervation, and action(s). As you identify and dissect neurovascular structures, you should review their pathways.
If you are having trouble highlighting narrow structures (arteries, veins, nerves), you can search for them by selecting the Anatomy tab, typing the name of the structure in the search box, and selecting the sun icon next to the listed structure. You can dissect these structures by selecting the eye icon.
- Identify the cephalic, basilic, and median cubital veins. The venous pattern of these superficial vessels is extremely variable. You will need to rotate the model to view these veins on both the anterior and posterior sides of the arm and forearm
- The dorsal venous plexus is the network of veins visible on the dorsum (posterior side) of the hand. The basilic and cephalic veins originate from the dorsal venous plexus
- The lateral cutaneous nerve of the forearm and medial cutaneous nerve of the forearm can generally be identified superficial to the cubital fossa, but are not visible on to model. Identify them in the images below:
Q2: What blood vessel is typically accessed during venipuncture in the cubital fossa? (answer)
Cubital Fossa
Rotate the model and zoom in to view the cubital fossa – the anterior depression on the anterior surface of the elbow. The roof of the cubital fossa (the bicipital aponeurosis and the deep fascia of the arm) is not visible on the model.
- Identify the medial and lateral borders of the cubital fossa: the pronator teres and brachioradialis muscles
- Identify the contents of the cubital fossa: the tendon of biceps brachii (selecting the tedon will select the entire muscle), the brachial artery, and the median nerve (MPR)
- Dissect the brachioradialis
- Identify the floor of the cubital fossa: the brachialis and supinator muscles
Q3: Describe the motions of the brachialis and brachioradialis muscles. (answer)
Forearm
For the next steps, use the model with the superficial veins removed:
- Identify and dissect the brachioradialis muscle
- Identify the extensor carpi radialis longus and extensor carpi radialis brevis muscles
- Identify the extensor digitorum and extensor digiti minimi muscles
- Identify the extensor carpi ulnaris muscle
Distally, you’ll see some muscle tendons that are not highlighted – the bellies of these posterior compartment muscles are deep to the highlighted muscles.
- Dissect the extensor carpi radialis longus, extensor radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris
- Identify the muscles that form the anatomical snuffbox: extensor pollucis longus, extensor pollucis brevis, and abductor pollucis longus (MPR)
- Identify the radial artery in the anatomical snuffbox
- Identify the radial nerve
- Identify the remaining deep muscles of the posterior compartment of the forearm: supinator and extensor indicis
Rotate the model to view the anterior forearm.
- Identify the superficial muscles of the anterior compartment of the forearm: flexor carpi ulnaris, flexor digitorum superficialis, flexor carpi radialis, and pronator teres (MPR)
- The palmaris longus muscle is variable, and is absent from the model
- Dissect flexor carpi ulnaris, flexor carpi radialis, and flexor digitorum superficialis muscles
- Identify the median and ulnar nerves
- Identify the ulnar artery travelling with the ulnar nerve in the anterior forearm
- Identify the flexor pollicis longus, and flexor digitorum profundus muscles (MPR)
- Dissect the flexor pollicis longus and flexor digitorum profundus muscles and identify the pronator quadratus (MPR)
The carpal tunnel
The flexor retinaculum and extensor retinaculum are not visible on the model, but you can use this view to assist in understanding the carpal tunnel:
The tendons and nerve passing through the carpel tunnel are highlighted, as well as the bones where the flexor retinaculum attach. Using the MPR images, especially the transverse MPR pane (top left) make sure you understand the contents of the carpal tunnel:
- median nerve
- flexor digitorum superficialis
- flexor digitorum profundus
- flexor pollicis longus
- Highlight the ulnar nerve and artery to observe that they pass superficially to the flexor retinaculum, and are not in the carpal tunnel
Q4: What structures are affected in carpel tunnel syndrome? (answer)
The hand
To observe structures in the hand, use the following view:
- Identify the basilic and cephalic veins, and recall that were the network on the dorsum of the hand is the dorsal venous plexus. Dissect these veins
- Identify the extensor muscles whose tendons run on the dorsum of the hand: extensor digitorum, extensor digiti minimi, extensor indicis, and extensor pollicis longus. Dissect these muscles (MPR)
- Identify the (4) remaining muscles visible on the dorsum of the hand. These are the dorsal interossei muscles, which are numbered according to their proximity to the pollux (first digit/thumb)
- On the MPR images, observe how the interossei muscles sit in between the metacarpals
Rotate the model to the palmar side (you may have to zoom out, as the model rotates around the midline and not the current view)
- The most superficial structures of the palm are the palmar aponeurosis (not visible on the model) and the palmaris brevis. Identify and dissect the palmaris brevis.
- On the thumb side, the model will show a single muscle labeled “opponens pollcis”. There are actually three muscles here (the thenar muscle group): abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. Identify the 2 superficial thenar muscles visible in the images below, then dissect this muscle group. (MPR)
- Identify the hypothenar muscles: abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi
- Identify the median nerve, ulnar nerve, and ulnar artery as they travel into the hand. The median and ulnar nerves branch in the palm but these branches are not specifically labeled on the model
- On the image below, identify the branches of the ulnar nerve: superficial branch of the ulnar nerve, deep branch of the ulnar nerve, common palmar digital branch, proper palmar digital branches
- On the image below, identify the branches of the median nerve: recurrent branch of the median nerve, common palmar digital branches, proper palmar digital branches
- Identify the common palmar digital arteries and the proper palmar digital arteries. The superficial palmar arch is erroneously included with the common palmar digital arteries on the model – use the image below (or above) to differentiate them, and to identify the superficial branch of the ulnar artery and superficial branch of the radial artery
- Dissect the median nerve, ulnar nerve, common palmar digital arteries, and flexor digitorum superficialis
- Identify the tendons of the flexor digitorum profundus
- Identify the 4 lumbrical muscles (MPR)
- Dissect the lumbricals and the flexor digitorum profundus
- Identify the adductor pollicis. Adductor pollicis has a transverse head and an oblique head (not defined on the model)
- The deep palmar arch is not visible on the model. Identify it on the image below:
- Dissect the adductor pollicis and identify the 3 palmar interossei muscles (MPR)
Deep structures of the palm (2)
Q5: Review the movements of the muscles of the hand. (answer)
End of Sectra activity
Answers to activity questions
Below are answers to questions asked during the activity. Clicking the ‘back to lab’ link below each answer will take you back to the question (you may need to scroll up a little to view the question again).
Q1: What joint is affected in a patient with nursemaid’s elbow (be specific)?
- Also known as a “pulled elbow”, nursemaid’s elbow is the subluxation (incomplete dislocation) of the elbow, specifically the radiocapitellar joint, when the head of the radius slips out of the annular ligament
Q2: What blood vessel is typically accessed during venipuncture in the cubital fossa?
- The median cubital vein is most commonly accessed during venipuncture in the cubital fossa
Q3: Describe the motions of the brachialis and brachioradialis muscles.
- Brachialis: flexes forearm in all positions
- Brachioradialis: flexes forearm when mid-pronated (as if lifting a glass)
Q4: What structures are affected in carpel tunnel syndrome?
- Commonly caused by inflammation of the synovial sheaths, carpal tunnel syndrome primarily affects the median nerve. It may also affect tendons of the following muscles: flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus
Q5: Review the movements of the muscles of the hand.
- Thenar muscles
- opponens pollicis: brings thumb into opposition (draws 1st metacarpal medially to center of palm and rotates it medially)
- abductor pollicis brevis: abducts thumb, assists in opposition
- flexor pollicis brevis: flexes thumb
- Hypothenar muscles
- abductor digiti minimi: abducts 5th digit (pinkie)
- flexor digiti minimi brevis: flexes proximal phalanx of 5th digit
- opponens digiti minimi: brings 5th digit into opposition (draws 5th metacarpal anterior and rotates it)
- Adductor pollicis (oblique and transverse heads): adducts thumb
- Lumbricals: flexes metacarpophalangeal joints, extends interphalangeal joints of 2nd-5th digits
- Dorsal interossei: abducts 2nd-4th digits
- Palmar interossei: adducts 2nd, 4th, and 5th digits