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213: HUMAN FUNCTIONAL ANATOMY: PRACTICAL CLASS 1: Proximal bones, plexuses and patterns CLAVICLE Examine an isolated clavicle and compare it with a clavicle on an articulated skeleton. Viewed from above, it is an 'S' shaped bone with a bulbous medial end, and a flattened lateral end. On the inferior surface near the lateral end is a roughened area for the coraco-clavicular ligament. Make sure you can determine whether an isolated clavicle is from the left or right side. What features allow you to distinguish: Medial from lateral Anterior from posterior Superior from inferior Surface Anatomy Palpate your own clavicle, feel the sternoclavicular joint medially, and try to determine where the clavicle joins the acromion of the scapula laterally. Use the skeletons to help you find where to feel for your coracoid process. Place your hand on your clavicle and move your shoulder about. What is the role of the clavicle in the mechanics of the shoulder? Use the plastinated preparations of the ligamentous shoulder to identify the strong coracoclavicular (conoid and trapezoid) ligaments that attach the clavicle to the scapula On wet specimens identify the muscles (see above) that attach to the clavicle IN each case indicate the nerve supply: Trapezius Sternomastoid Pectoralis major Deltoid Examine the dissection of a dog shoulder. Where does anterior trapezius and deltoid, and the clavicular part of pectoralis major attach when there is no clavicle. Why do you think the dog lacks a clavicle? THE ROOT OF THE NECK. Using deep prosections. 1. Find the scalenus anterior muscle; it arises from the anterior tubercles of the cervical transverse processes. 2. Find the scalenus medius and posterior muscles arising from the posterior tubercles of cervical transverse processes. 3. Find the roots of the brachial plexus in the interscalene plane Use the diagram of the cervical vertebra to add the scalenes and cervical spinal nerves forming the roots of the brachial plexus THE POSTERIOR TRIANGLE is above the clavicle Examine the side of the neck in the space bounded by trapezius, sternomastoid and the clavicle. Identify, the muscles forming the floor of this space starting inferiorly: scalenus anterior, brachial plexus, scalenus medius and posterior, levator scapulae, splenius and semispinalis (at the apex of the triangle). Draw a diagram of the posterior triangle in the space provided. (Note : this is a diagrammatic representation. In reality the “triangle” is narrow and somewhat “twisted”. Label the following: Semispinalis capitus Splenius Levator scapulae Scalenus medius/posterior Brachial plexus Scalenus anterior Trapezius Sternomastoid Accessory nerve (CN XI) Phrenic nerve Subclavian vein Subclavian artery Cervical plexus Clavicle What does the accessory nerve supply? What does the cervical plexus (C1, 2, 3, 4) supply? Motor Sensory The phrenic nerve comes partly from the cervical plexus and partly from the brachial plexus (C3,4,5). What does it supply? Motor Sensory THE AXILLA. is below the clavicle. It is the pathway for all nerves and vessels entering the upper limb The axilla is a pyramidal space formed at the junction of the shoulder and trunk. On a skeleton identify the apex of this pyramid, sometimes called the cervico-axillary canal, between the first rib, clavicle and scapula. The base of the pyramid is the skin of the armpit. Examine the diagram of a horizontal section through the axilla. Note the walls of the axilla: medial, posterior, anterior and the very narrow lateral wall Identify the greater and lesser tubercles of the humerus and the crests descending from them. Note that the muscles of the anterior and posterior walls attach to these and that the lateral wall is comprised of the intertubercular (bicipital) groove. Return to the prosections and study the walls of the axilla: Posterior wall made up of the scapula and the muscles which pass from the scapula to the humerus: Latissumus dorsi Teres major Subscapularis Long head of triceps Note the gap between teres major and subscapularis. What passes through this opening in the posterior axillary wall? Medial wall made up of the rib cage clothed in the serratus anterior muscle, note the long thoracic nerve on serratus anterior. Anterior wall: Pectoralis major and Pectoralis minor. The lateral wall is very narrow and consists of the long tendon of biceps in the intertubercular groove. Indicate the nerve supplies of the muscles forming the walls of the axilla: 1. All the posterior wall muscles are supplied by posterior divisions of the plexus 2. The anterior wall muscles are supplied by the anterior divisions of the plexus Inside the diagram of the axilla, draw the axillary vessels and the brachial plexus. What parts of the brachial plexus appear in this cross section? What other structures fill the space inside the axilla? BRACHIAL PLEXUS Revise the brachial plexus, drawing a large diagram of its roots, trunks, divisions, cords, and branches. ROOTS TRUNKS DIVISIONS CORDS NERVES C5 C6 C7 C8 T1 Now add the following collateral branches and state what each nerve supplies: Nerve Long thoracic nerve Dorsal scapular nerve Suprascapular nerve Medial pectoral nerve Lateral pectoral nerve Thoracodorsal nerve Subscapular nerves Medial Cut. n. of the arm Medial Cut. n. of forearm Origin from Roots C5 6 7 Roots C3 4 5 6 Upper trunk Medial cord Lateral cord Posterior cord Posterior cord Medial cord Medial cord Comments Motor to serratus anterior. Sensory to medial forearm Study the brachial plexus again on the prosections, start at the roots and follow the plexuses branching and rejoining pattern, as you do so identify each of the collateral branches. Hint : When you reach the divisions it will help to place a stick between the anterior and posterior divisions 1. The anterior divisions unite to form a “big M’ shape comprising the medial and lateral cords giving off the musculocutaneous, median and ulnar nerves. 2. The posterior divisions all unite to form the posterior cord which divides into radial and axillary nerves. Note the relationship of the cords of the brachial plexus to: a) The axillary artery b) The pectoralis minor muscle . What parts of the plexus lie between the scalene muscles? THE PELVIS AND STRUCTURES THAT PASS INTO THE LOWER LIMB Examine the skeleton of the pelvis. Identify the following structures and indicate them on the diagrams below – you should be able to feel the underlined structures on yourself Anterior Ilium Gluteal surface Iliac surface ASIS Crest Ischium Tuberosity Spine Sciatic notches Obturator foramen Pubis Posterior Pubic tubercle Body Superior ramus Ischiopubic ramus Inguinal ligament Sacrum Sacrotuberous ligament Sacrospinous ligament Greater sciatic foramen Find the following openings in the pelvis, both on the bones and the wet specimens. Also indicate the structure passing into the lower limb Space below the inguinal ligament and structures that pass through it to reach the front of the thigh (femoral triangle) Nerve Artery Vein Lymphatics Obturator foramen and canal Nerve Artery and vein Greater Sciatic notch/foramen Nerve Nerve Nerve Artery and vein Artery and vein LUMBOSACRAL PLEXUS Examine the prosections of the lower limb and identify the following nerves 1. Obturator (L2,3,4) 2. Femoral (L234) 3. Superior gluteal (L4,5,S1) 4. Inferior gluteal (L5,S1,2) 5. Sciatic (L45,S1,2,3) (including the Tibial and Common peroneal nerve) Trace each nerve from its source to its distribution in the limb, note the division of the sciatic nerve into its tibial and commo n peroneal divisions. For each of the major nerves of the lumbosacral and brachial plexuses, state its distribution and classify it as "dorsal" or "ventral". (Remember that the upper and lower limbs rotate in opposite direction during development.) Nerve Distribution Dorsal or ventral Radial Motor: Posterior compartment of arm and forearm dorsal Sensory: Posterior aspect of upper limb Femoral Common peroneal Axillary Superior and inferior gluteal Median Ulnar Tibial Musculocutaneous Obturator Consider which nerves from the lumbosacral sacral plexus are homologous with nerves of the brachial plexus (use the worksheet on the next page) Do you think the sciatic nerve is really one nerve that “branches” into two? What is your argument? Examine more than one prosection, check for variations in the division of the sciatic nerve. HOME WORKSHEET: Dorsal and ventral structures Be prepared to discuss your answers/opinions at a tutorial in week 3. of upper & lower limbs DORSAL Darker, hairer skin side of limb, usually has extensor muscle groups. Upper limb Lower limb Bones Most of the Scapula Vertebrae Ilium Vertebral column Nerves Radial Axillary Gluteal Femoral Common peroneal Muscles Triceps Deltoid Extensors of the wrist and hand Quadriceps & iliopsoas Gluteals Peroneal muscles Foot and ankle extensors VENTRAL Paler, less hairy skin, usually has flexor muscle groups. Upper limb Lower limb Bones Coracoid and supraglenoid tubercle Clavicle Ribs and sternum Ischium Pubis Nerves Ulna Median Musculocutanous Pectoral nerves Tibial Obturator Muscles Pectorals Biceps etc Flexors of the wrist and hand Adductors Hamstrings Calf muscles Flexors of the foot and toes As you read the muscle groups, touch those areas of your own limbs For each of the muscle groups pick the nerve supply from the nerves directly above. Try to connect homologous (similar) bones, nerve and muscle between limbs – this should be fairly easy for the nerves and muscles – but not so clear for the boney parts Are there any nerves or muscle groups that don’t have any counterparts in the other limb? Are all the dorsal muscles extensors? Practical anatomy checklist Osteology Clavicle Parts of the clavicle, muscles, ligaments, joints and orientation Pelvis Parts of the ilium, ischium and pubis Ligaments (inguinal, sacrotuberous, sacrospinous, sacroiliac) Openings (for femoral neurovascular structures, obturator, Sciatic foramina) Humerus Head, tubercles, crests descending from the tubercles and bicipital groove Regions: Posterior triangle Boundaries, and muscles in the floor Scalenes and roots of brachial plexus Axilla Muscles forming the anterior, posterior, medial and lateral walls of the axilla) Contents Femoral triangle Boundaries, and muscles in the floor Femoral nerve artery and vein Nerve plexuses Brachial plexus Pattern of main parts (roots, trunks, divisions, cords branches and nerves) Main branches and their distribution to muscle groups Other branches to shoulder muscles (long thoracic. suprascapular, dorsal scapula, pectoral, thoracodorsal, subscapular) Lumbosacral plexus Main branches and their root values (femoral, obturator, tibial, common peroneal, superior and inferior gluteal) Distribution of main branches to muscle groups
