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Human Gross Anatomy Lecture 4

by: Anais Ioschpe

Human Gross Anatomy Lecture 4 BISC 2581

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Anais Ioschpe

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GWU Human Gross Anatomy Lecture 1 notes from lecture, powerpoint, and handout.
Human Gross Anatomy
Jeffrey Rosenstein; Raymond Walsh;
Class Notes
anatomy, Axilla, arm, nerves
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This 19 page Class Notes was uploaded by Anais Ioschpe on Wednesday January 20, 2016. The Class Notes belongs to BISC 2581 at George Washington University taught by Jeffrey Rosenstein; Raymond Walsh; in Spring 2016. Since its upload, it has received 83 views. For similar materials see Human Gross Anatomy in Anatomy at George Washington University.


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Date Created: 01/20/16
Human Gross Anatomy Lecture 4 on 21/1/16 Human Gross Anatomy Introduction to the Upper Limb— Axilla and Arm Learning Objectives for the Lecture on the Axilla 1) Describe lymphatic drainage of the breast 2) Describe the arterial blood source in the axilla 3) Recall the arteries which are the chief source of blood supply to (a) the tissues of the lateral half of the breast and (b) the head of the humerus 4) Describe the structure of the brachial plexus 5) Recall the cords of the brachial plexus from which the five major nerves of the upper limb arise. The nerves are the axillary, musculocutaneous, radial, median, and ulnar nerves 6) Recognize the veins of the arm and relation to the cubital fossa Introduction to the Axilla - Under the skin and a little bit of fat there is a tremendous amount of nerves, veins, lymphatics, and a very large artery, the axillary artery, that runs through the middle of the radial plexus. - The axilla (armpit) is a confined space, the contents of which are of great clinical and anatomical significance. The borders of the axilla are formed by the pectoralis major muscle (anterior axillary fold) and the teres major and latissimus Dorsi. (posterior axillary fold). The major contents include: • The branchial plexus, the major nerve network of the upper limb (C5-T1 spinal cord levels). These nerves traverse the neck, enter the axilla and extend down to the fingers. • The axillary artery and its branches • The Lymphatic drainage area of the breast and • The veinous drainage of the upper limp - The most superficial structure of the axillary region is the breast (mammary gland). The breast overlies the pectoralis major and serratus anterior. While obviously on the anterior chest wall, the mammary gland is discussed with the axilla because much of the blood supply is derived Page 1 of 9 from the axillary artery and its lymphatics drain into the axilla. Most of all of the lymph nodes are located in and around the axilla. 75% of the lymphatic drainage of the breast id from the lateral portion where the majority of the glandular tissue is found. Drainage is to several groups of axillary lymph nodes which include apical, posterior, anterior and central subgroups. Lymph may also drain from parasternal nodes along the sternum - Arterial Vasculature • Axillary artery: - The major artery coursing through the axilla is the axillary artery. The axillary is a direct continuation of the subclavian artery, one of the main vessels that arise from the aortic arch. - It begins at the lateral border of the first rib and ends at the inferior border of the teres major as the brancial artery from the second part. It emerges from behind the pectoralis minor and supplies the pect muscles and it is the major blood supply to the lateral part of the breast. It runs close enough to the long thoracic nerve that poor surgical technique during a radical mastectomy can cause a winged scapula in the patient • Other significant arteries emerge from the third part. The large subscapular artery divides into the circumflex scapular and the thoracodorsal which supply much of the musculature around the scapula. Next, the anterior and posterior humeral circumflex arteries course around the surgical neck of the humerus— the anterior circumflex is the chief source of blood to the head of the humerus while the posterior runs with the axillary nerve in the Page 2 of 9 posterior scapular region. Note that the axillary artery continues as the brachial artery in the arm which then divides into the radial and ulnar arteries past the elbow joint. These arteries continue down the forearm and into the hand where they will be discussed in greater detail. • The blood leaves your heart and becomes the subclavian (under the clavical) which is the primary blood supply of the upper limb. The subclavian then turns into the axillary artery as it passes the 1st rib. The axillary artery then turns into the brachial artery as it passed the surgical neck of the humerus. - it branches off in many areas: • Commom carotid: supplies blood to face and brain • Lateral thoracic artery (KNOW FOR EXAM) - Important features: • it runs with the long thoracic nerve— the nerve that can give you winged scapula • it is also a major blood supply to the breast • Vertebral artery - supplies the lateral side of the brain and cerebellum - Axillary Tail of the Mammary Gland This lateral aspect of the best is the vast majority • of the breast tissue (more fatty tissue than glandular tissue) • This fatty tissue is supplied by the lateral thoracic artery • The lymphatic drainage of the lateral aspect of the Page 3 of 9 breast and glandular tissue heads back into the anterior axillary nodes - Brachial Plexus • The brachial plexus originates in the neck and then extends over the last rib to enter the axilla. The plexus gives rise to almost all the nerves for the shoulder, arm, forearm and hand. • The initial parts of the brachial plexus are called the roots of the brachial plexus. - The roots of the brachial plexus lie in the neck outside (external to) the spine. The enterior rami of five spinal nerves (C5, C6, C7, C8, and T1) form the roots of the brachial plexus. It is important to understand that the roots of the branchial plexus are the anterior rami of C5, C6, C7, C8, and T1. - As they come out of the spinal cord they “mix and match” and form a plexus which eventually go down to the entire arm • Upper trunk: where C5 and C6 come together • Lower trunk: Where C8 and T1 come together - Trunks • The 5 roots of the brachial plexus give rise to the 3 trunks of the plexus.The upper trunk is formed from the union of the C5 and C6 roots. The middle trunk is an extension of the C7 root. The lower trunk is formed from the union of the C8 and T1 roots. As the trunks of the Page 4 of 9 brachial plexus pass over the lateral border of the 1st rib, they extend from the neck into the axilla. - Note that the upper trunk of the brachial plexus transmits only C5 and C6 nerve fibers, the middle trunk transmits only C7 nerve fibers, and the lower trunk transmits only C8 and T1 nerve fibers. • Only two nerves arise from the trunks of the brachial plexus: - The suprascapular nerve - The subclavian nerve - Both nerves arise from the upper trunk. The suprascapular nerve transmits nerve fibers from C5 and C6 only and innervates two of the rotator cuff muscles: supraspinatus and infraspinatus. The nerve to subclavius innervates the muscles for which it is named. • The 3 trunks of the brachial plexus give rise to the next major parts of the brachial plexus: the 6 divisions of the brachial plexus. Each trunk gives rise to an anterior division and a posterior division. No nerves arise from the divisions. - T1 • It is tucked under the rib and is at a vulnerable spot which can be ripped out with a very serious injury • responsible for innervating all the small muscles in your hand - Segmental innervation: a nerve ending that is comprised of one of more or more segments of a spinal cord • Musculocutaneous nerve: C5 and C6 • Radial nerve: C6, C7, C8, and T1 • Median nerve: C6, C7, C8, and T1 • Ulnar nerve: C8 and T1 - Only two nerves arise from the roots of the brachial scapular nerve fibers are from C5 only and innervates three shoulder muscles: levatator scapulae, rhomboid major, and rhomboid minor. The long thoracic nerve transmits C5, C6, and C7 nerve fibers and innervates only one shoulder muscle: serratus anterior. Serratus anterior is the chief protractor of the shoulder and one of the closely associated with the lateral thoracic artery. Page 5 of 9 - Rotator cuff is innervated by C5 and C6 - Cords: trunks turn into cords. the names are based on their position relative to the axillary artery - The 6 divisions of the brachial plexus give rise to the next major parts of the brachial plexus: the cords. • Lateral cord— lateral to the artery - The anterior divisions of the upper and middle trunks of the brachial plexus unite to form the lateral cord. • Posterior cord— behind the artery - Gives rise to the upper, middle, and lower subscapular nerves. • Medial cord— medial to the artery Page 6 of 1 9 - A continuation of the anterior division of the lower trunk of the brachial plexus. The medial cord transmits nerve fibers from C8 and T1 only. - The 3 posterior divisions of the brachial plexus unite to form the posterior cord. At its end, the posterior cord divides into 2 of the 5 major nerves of the upper limb: the axillary nerve and the radial nerve. • The axillary nerve transmits nerve fibers from C5 and C6 only and innervates two shoulder muscles: deltoid and the rotator cuff muscle teres minor. • The radial nerve and its branches innervate the only muscle in the posterior part of the arm (triceps brachii) and all the muscles in the posterior part of the forearm. - M formation: Cords divide again to form large nerves. 95% of the human bodies have a M shape. This M is the termination of the brachial plexus and gives rise to the major nerves (ulner, medial, radial, musculocutaneous) - Nerves: (Know the major 5 nerves and what muscles innervate them) Page 7 of 9 • They are very vulnerable - Radial nerve - Ulnar nerve • “Funny bone” - Musculocutaneous nerve • innervates all the muscles on the anterior surface of your arm - Median nerve - Axillary nerve • Three other nerves that arise from the posterior cord: upper subscapular nerve, middle subscapular nerve, lower subscapular nerve - The middle subscapular nerve is alternatively named the thoracodorsal nerve. The subscapular nerves innervate shoulder muscles. The upper and lower subscapular nerves each transmit nerve fibers from C5 and C6 only. The upper and lower subscapular nerves together innervate one of the rotator cuff muscles: subscapularis. The middle subscapular nerve innervates latissimus dorsi. The lower subscapular nerve alone innervates teres major. • The lateral cord divides into one and a half of the 5 major nerves of the upper limb: the musculocutaneous nerve and the lateral root of the median nerve. - The musculocutaneous nerve transmits nerve fibers chiefly from C5 and C6 and innervates all the muscles in the anterior part of the arm. The lateral root of the median nerve unites with medial root of the median nerve to form the median nerve. The lateral pectoral nerve combines with the medial pectoral nerve to innervate the shoulder/chest muscle pectoralis major. • The medial cord divides into one and a half of the 5 major nerves of the upper limb: the ulnar nerve and the medial nerve. The ulner nerve transmits only C8 and T1 nerve fibers and innervates only one and a half muscles in the anterior part of the forearm and all but five of the muscles in the hand. The medial root of the median nerve unites with the lateral root of the median nerve to form the median 
 Page 8 of 9 • nerve (C6, C7, C8, T1). The median nerve and its branches innervate all but one and a half of the muscles in the anterior part of the forearm and five of the muscles in the hand. RECAP OF BRACHIAL PLEXUS - Branches from the roots • nerve to the rhomboids (C5), the dorsal scapular • nerve to serratus anterior, the long thoracic (C5, C6, C7) - Branches from the Trunks • Suprascapular nerve (from the upper trunk) - Branches from the Cords • Lateral cord • Lateral pectoral • Lateral root of median (C6 and C7) • Musculocutaneous (C5, C6, C7) - Medial Cord • Medial pectoral • Medial cutaneous of arm • Medial cutaneous of forearm • Medial root of median (C8 and T1) • Ulnar (C8-T1) - Posterior Cord • Upper subscapular • Thoracodorsal (middle) Lower subscapular • Axillary (C5 and C6) • • Radial (C5 - T1) - C5 and C6 Nerve injury •Injuries to the brachial plexus can produce a broad spectrum of motor and sensory deficits in the upper limb. Complete analysis of the nature of a brachial plexus injury requires Page 9 of 9 examination by a neurologist. Most brachial plexus injuries involve either the upper parts of the plexus or the lower parts of the plexus; accordingly, most brachial plexus injuries are classifies as either upper or lower brachial plexus injuries. Upper brachial plexus injuries typically involve injury to the C5 and C6 roots or the upper trunk in the neck. • Damage to the radial nerve causes wrist drop • Roofer or motorcyclist lands on acromion process the skull absorbs the fall without a helmet. With a helmet he overly extends his neck and head. • C5 and C6 can be stretched or torn out at erbs point, the damage is known as Erbs Pasly or waiters tip palsy - The mechanism of injury which most commonly produces Erb’s palsy is excessive traction on the upper parts of the plexus caused by a fall that separates the head and shoulder. The muscles which may be partially or completely paralyzed by this injury on the upper parts of the brachial plexus include the upper limp muscles whose sole or major innervation is provided by C5 and/or C6 nerve fibers. - If significant damage is sustained to both C5 and C6 nerve fibers, the most important muscular actions compromised or lost by such damage are those of the rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis), teres major, deltoid, biceps brachii and brachialis Patient with Erbs Palsy: The shoulder loses its rounded contour and the upper limb does not swing forward and back when walking, this is due to the atrophy of the deltoid. The entire upper limb hangs in a deadened fashion; the shoulder joint is unstable due to loss of rotator cuff muscles and is medially rotator cuff muscles and is medially rotated due to the pull of pectoralis major which is intact. The elbow cannot be flexed and the forearm is pronated as a consequence of the loss of the brachialis and the biceps brachii’s supination action. The entire upper limb looks like that of the upper limb of a waiter when awaiting a gratuity; thats why its referred to as waiter’s tip palsy Page 10 of 1 9 - C8 and T1 Nerve injury • Injury to the lower part of the brachial plexus, which are less common, are caused by a strong upward pull on the limb such as grabbing something to break a fall or pulling on an infants’ limb during birth. This injury damages the lower trunk (C8-T1) and effectively destroys the ulnar nerve. - T1 is responsible for all the muscles in the hand, and if damaged results in Klumpke palsy • Disabling condition called “Claw hand” • Saturday night palsy— causes transient wrist drop - Common in drunks who fall asleep on chairs and compromise the radial nerve - Only lasts a day or so Page 11 of 1 9 - Veins of the Arm • The superficial veins of the arm of the arm are of clinical importance. Because they are embedded in superficial tissue they are commonly used for venipuncture to draw blood or for catheteriazation. • The basilic and cephalic vein are the largest superficial veins of the arm. - The basilic and cephalic veins lie in the superficial fascia on, respectively, the medial and lateral sides of the arm. The two veins are generally connected in the superficial fascia of the cubital fossa by a short communicating vein called the median cubital vein which is most often used for venipuncture. The basilic vein ends by joining the brachial veins to form the axillary vein at the lower border of teres major. - The sephalic vein is the largest vein to join the axillary vein in the axilla. Page 12 of 1 9 Introduction to the Arm Learning Objectives for the Lecture on the Arm 1. Identify the major nerve of the upper limb most a risk of injury from (a) a fracture of the midshaft of the humerus and (b) a fracture of the medial epicondyle of the humerus. 2. List the innervation and major actions of all the arm muscles 3. List the spinal nerves that control flexion and extension of the arm at the elbow joint 4. List the spinal nerves involved in the biceps and triceps tendon reflex tests\ 5. Describe the contents of the cubital fossa - Anterior compartment and a posterior compartment Muscles of the arm are divided into anterior and posterior gruops by the intermuscular • fascial septa that extend and attach to the humerus. • Skin and fat is the superficial fascia layer above the muscle. When rubbing the skin on your hand, you’re essentially rubbing the fat of the superficial fascia against the top of the deep fascia - Anterior arm muscles • All the anterior arm muscles are innervated by the musculocutaneous nerve • As a group, the muscles work together to flex the elbow joint and supinate the hand Page 13 of 1 9 • Biceps brachii: Anterior surface of the arm, the biceps muscle is the longest and dominant muscle. - Biceps brachii has two heads of origin; a long head of the biceps that goes into the shoulder joints to stabilize the humerus at the intertuberualar groove. The short head of the biceps that actually longer and originates from the corcoid process. Both heads pass the elbow joint and is inserted at the radius. The biceps muscle is the only one that flexes and supinates at the same time.The muscle fibers of the two heads merge in the distal half of the arm. Biceps brachii is the chief supinator and a major flexor of the forearm. • Physical test to check for function biceps brachii - This test is called the biceps brachii tendon reflex test. The biceps brachii tendon reflex test assesses spinal cord reflex activity in the C5 and C6 spinal cord segments because biceps brachii is innervated by nerve fibers that enter and exit the spinal cord chiefly via the C5 and C6 spinal nerves. • Bicipital aponeurosis: a flat sheet of connective tissue which blends into the deep fascia on the upper anteromedial side of the forearm. It covers the cubital fossa in which the medial vein sits on top of. Helps to protect the brachial artery and the median nerve running underneath (during venipuncture) from the median cubital vein. It originates from the distal insertion of the biceps brachii and runs across the brachial artery Page 14 of 1 9 - Posterior arm muscle • Consists of only the triceps brachii muscle - Innervated by the radial nerve - Chief extensor of the forearm; serves to extend the forearm from a flexed position (e.g. doing a push up) - Has three heads; the long head originates from the infraglenoid tubercle of the scapula, the short head originates from the posterior part of the humeral shaft which is lateral and superior to the spiral groove, and the medial and inferior to the spiral groove, and the medial head originates from the part of the posterior surface of the humeral shaft which is medial and inferior to the spiral groove. • The muscle fibers from all the three heads merge in the lower half of the arm and give rise to a tendon of insertion that passes behind the elbow joint onto the olecranon process of the ulna. - Physical test to check for function triceps brachii • Called the tricepts brachii tendon reflex test. A gentle but firm and quick hammer tap to the muscle’s tendon of insertion should elicit a short, quick extension of a partially flexed forearm. The triceps brachii reflex test assesses spinal cord reflex activity in the C7 and C8 spinal cord segments levels because triceps branchii is innervated by nerve fibers that exist and enter the spinal cord chiefly via the C7 and C8 spinal cord levels. At this point you should recall that the triceps is innervated by the radial nerve which is composed of all the brachial plexus segments (C5-T1). However, the triceps innervation is derived predominantly from C7 with lesser contribution from C8. Therefore elbow extension is controlled by that portion of the radial. - Coracobrachiallis • Muscle under the biceps muscle. It is the smallest of the anterior arm muscles. Originates from the coracoid process of the scapula and inserts onto the shaft of the humerus. • Can weakly flex and adduct the arm at the shoulder joint. It does not work on the elbow joint. • It is innervated by the musculocutaneous nerve. The musculocuntaneous nerve then comes down and innervates another muscle, the brachialis muscle that runs from the middle of the humerus, passes the elbow joint, and reaches the ulnar. - Brachialis: originates from the lower half of the anterior surface of the shaft of the humerus, passes anterior to the elbow joint, and inserts onto the anterior surface of the upper ulna near the coracoid process. Brachialis is the chief flexor of the forearm. Flexion of the forearm at the elbow joint is controlled mainly by C6 nerve fibers because biceps brachii and brachialis, Page 15 of 1 9 which are the major flexors of the forearm at the elbow joint, each receive more innervation from C6 than C5 nerve fibers. RECAP - Flexor Compartment of the Arm •Coracobracialis - Attachments: coracoid to shaft of humerus - Actions: weak adduction and flexion of humerus •Biceps brachii - Attachments: short head; coracoid. long head; supraglenoid tubercle-radial tuberosity - Actions: flexion of shoulder and elbow and supination •Brachialis - Attachments: lower front of humerus-coronoid of ulna - Actions: flexion of elbow. *Nerve supply of all flexor compartment-musculo-cuntaneous (C5-C6)* - Extensor Compartment of the Arm •Triceps - Attachments: infraglenoid tubercle and back of humerus-olecranon - Actions: extension of elbow Page 16 of 1 9 *Nerve supply: radial (C7-C8)* Vasculator system in the upper arm - Three veins of importance • Cephalic vein - Runs between the deltoid muscle and the pec major • Basilic vein - located on the medial side • Median cubital vein - vein that crosses over between the two veins, running over the cubital fossa - Arteries • Subclavian artery Axillary artery • Brachial artery runs with the median nerve; and is divided into two other arteries • - Radial artery on the thumb side - Ulnar artery on the little finger side Page 17 of 1 9 - Cubital fossa (elbow pit) • Is the triangular shaped area on the anterior aspect of the elbow region. Several important structures are found in the fossa as they transition from the arm into the forearm. The lateral border is formed by the brachioradialis muscle and the medial border is the pronator teres muscle of the forearm. The floor is the brachioradialis muscles of the forearm. • Very exposed, no bony protection • Contents - Radial nerve is in the vicinity of the cubital fossa, located between brachioradialis and brachialis muscles. The is often by not always considered part of the cubital fossa - Biceps branchii tendon - Brachial artery. The artery usually bifurcates (divide into two branches or forks.) near the apex (inferior part) of the cubital fossa into the radial artery (superficial) and ulnar artery (deeper) - Median nerve • The ulnar nerve is also in the area, but its not in the cubital fossa • Several veins are also in the area ( median cubital vein, cephalic vein, and basilic vein) but these are usually considered superficial to the cubital fossa and not part of its contents • Bicipital aponeurosis sheet of connective tissue that the medial cubital vein sits on - Optimal for IVs and the reason why you can move the vein when drawing blood - Fracture of the Humerus/Nerve Relationship • Fracture of the humerus is not the most common fracture in the upper limb, but this injury can have serious neurological consequences because of the proximity of large nerves to specific regions of the bone. • There are 3 important areas: - The axillary nerve, which supplies the deltoid, the major abductor of the shoulder joint, is closely related to the surgical neck of the humerus - The radial nerve, which supplies all the extensor muscles of the upper limb, passes diagonally around the posterior surface of the middle (midshaft) of the humerus in the radial (spinal) groove. Serious damage here would produce characteristic “wrist drop” - The ulnar nerve, which is destined for the hand, passes posteriorly in a groove on the medial epicondyle on medial side of the distal end of humerus. You can palpate this on Page 18 of 1 9 yourself-it is your “funny bone”. Ulnar nerve damage here can cause serious motor and sensory deficits in the hand. - RECAP (most important to know) • Brachial artery • Median nerve • Biceps tendon • Radial nerve Page 19 of 9


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