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Home , Trochlea of humerus

ANAT2009 – Comparative Primate Anatomy

Table of Contents:

STARTING TIPS INTRODUCTION (LECTURE 1) PECTORAL GIRDLE AND (LECTURE 5) AND DISTAL (LECTURE 7) WRIST AND (LECTURE 9) SKULL (LECTURE 11) BRAIN (LECTURE 13) VERTEBRAL COLUMN (LECTURE 15) THE PELVIS (LECTURE 17) HIP JOINT AND THIGH (LECTURE 19) KNEE JOINT AND LEG (LECTURE 21) ANKLE AND FOOT (LECTURE 23) EARLY COMPARATIVE LECTURES (LECTURES 2, 3 & 4) COMPARATIVE PECTORAL GIRDLE AND SHOULDER (LECTURE 6) COMPARATIVE ELBOW AND DISTAL HUMERUS (LECTURE 8) COMPARATIVE WRIST AND HAND (LECTURE 10) COMPARATIVE SKULL (LECTURE 12) COMPARATIVE BRAIN (LECTURE 14) COMPARATIVE VERTEBRAL COLUMN (LECTURE 16) COMPARATIVE PELVIS (LECTURE 18) COMPARATIVE HIP JOINT AND THIGH (LECTURE 20) COMPARATIVE KNEE JOINT AND LEG (LECTURE 22) COMPARATIVE ANKLE JOINT AND FOOT (LECTURE 24)

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ELBOW AND DISTAL HUMERUS (LECTURE 7)

Articulations - articular parts of humerus = = capitulum and trochlea - non-articular parts = lateral and medial epicondyles - capitulum articulates with radial head - trochlea articulates with trochlea notch of - radial articulation/ulnar facet on ULNA articulates with the ulnar notch of the - articulates with the of the ulnar Features (name - capitulum (can’t see from posterior angle) the notch after - trochlea the feature they - (contains radius IN FLEXION) ACCEPT) - coronoid fossa (contains ulnar coronoid process) - fossa (contains ulnar olecranon in EXTENSION) - radial head and neck (constriction below head) - - sharp borders on medial side (interosseous border) at distal end of radius/ulna - interosseous membrane (attaches to interosseous borders) - styloid process of radius (radius distal end) on lateral side - dorsal tubercle (radius distal end) on posterior side - olecranon - - radial notch (on lateral side of coronoid process) - coronoid process - ulnar tuberosity - styloid process of ulna (ulnar distal end) - radial articulation/facet (ulnar distal end) – conforms to the ulnar notch of the radius Joints - Elbow joint comprised of: a) humeroulnar joint = hinge (trochlea of humerus and trochlear notch of ulna) b) humeroradial joint = gliding à (capitulum of humerus and head of radius) *** some controversy about the classification of this joint. - Radioulnar joint comprised of: a) Superior radioulnar joint (proximal end) = pivot = radial head and radial notch of ulna à this is absolutely key in the ability of the radius to cross over the ulna (which is fixed in place) during supination b) Inferior radioulnar joint (distal end) = pivot = ulna notch of radius and facet on lateral side of ulna Capsules and - 1 capsule around BOTH elbow and superior RU joints ligaments - Annular ligament (surrounds head of radius) - Ulnar collateral ligament (medial) à reinforces capsule, attached to medial epicondyle, coronoid process and medial olecranon process - Radial collateral ligament (lateral) à reinforces capsule, attached to lateral epicondyle and annular ligament - 1 capsule around inferior RU joint

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Movements - Flexion around the elbow - extension joint Muscles moving Elbow flexion: (any muscle crossing anterior side will be a flexor) the elbow joint - brachialis à origin is halfway down the anterior side of the humerus at a similar point to brachioradialis (use this to differentiate from corachobrachialis, which also sits under the BB but originates from the ) and crosses DIAGONALLY across elbow to insert into the ulnar tuberosity. IT APPEARS WHERE THE DELTOID STOPS. - biceps brachii à a superficial muscle, arises from just below pec major and deltoid. Crosses shoulder joint and elbow joint. Originates at the AND coronoid process (hence two heads = “biceps”). Goes down to the radial tuberosity. Under the BB sit the coracobrachialis (shoulder joint mover) + brachialis (elbow joint mover) + brachioradialis (elbow joint mover). - brachioradialis à origin on the lateral, anterior side of the humerus (similar point to brachialis), then moves STRAIGHT down radius (no diagonal movement) to attach way down in the . Easy because sits exactly between triceps brachii and brachialis and is very long. - pronator teres à crosses diagonally from medial to lateral on the anterior side of the , and has two heads. One attaches to JUST above the medial epicondyle, the other attaches to the medial side of the coranoid process à then crosses obliquely (more diagonally than pronator quadratus) to insert into the lateral side of the radius, just distal to the supinator insertion.

Elbow extension: - triceps brachii (TB) à quite wide and fat, can actually see its medial and lateral heads from the anterior side - poking out from behind the big biceps brachii (BB), mostly in top area. Don’t confuse with coracobrachialis or brachialis in anterior view – look for origins as clues à coracobrachialis originates at the coracoid process and lodges down quite quickly to anterior side of humerus, brachialis is a teardrop-shaped muscle that sits under BB – starts halfway down humerus on lateral side then crosses over to insert into the ulnar tuberosity. The long head of the TB originates from the infraglenoid tuberosity. Its two other heads originate from the lateral/medial posterior side of the humerus. They joint to insert into the olecranon. - anconeus – short muscle on posterior side, crosses obliquely down from its tiny origin lateral epicondyle of the humerus to the top of the ulnar (becomes wide at base, quite a wide insertion). Movements - pronation around RU joint - supination (both superior + inferior) Muscles moving Pronation: RU joint (move - pronator teres à see previous description.

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& hand - pronator quadratus à attaches to the distal end of the ulna, then moves with it) diagonally down (only at a slight angle) to insert into the distal end of the radius.

Supination: - supinator à anterior and posterior. Two heads. One is at the medial, posterior side of the ulna, the other is at the lateral epicondyle of the humerus. They converge on the posterior side then wrap around SLIGHTLY to insert into the lateral side of the radius. - biceps brachii à see previous description Movements of the - flexion and extension hand and wrist - adduction and abduction Muscles in - superficial forearm flexors ARISE AS A GROUP from the medial epicondyle anterior (anterior surface) compartment of - deep forearm flexors arise from the anterior interosseous membrane forearm - the intermediate layer lies in between. - The deep layer lie in contact with the radius and ulna.

Superficial: - flexor carpi radialis (ends on radial side) – flexes and abducts wrist - palmaris longus (inserts into palm area just below fingers) – flexes wrist - flexor carpi ulnaris (ends on ulnar side – at pisiform ) – flexes and adducts wrist. - End in the metacarpal region.

Intermediate: - flexor digitorium superficialis (flexes middle and proximal phalanges of fingers, splits in half to let profundus through and attaches to either side of middle phalanges on anterior surface)) and may flex wrist. - LOOK VERY CAREFULLY FOR THE SPLIT. End at middle phalanges.

Deep: - flexor digitorium profundus (flexes phalanges of fingers – goes to distal phalanges, may also flex wrist) - flexor pollicis longus (flexes phalanges of thumb). - End at distal phalanges.

** flexor digitorium profundus and flexor digitorium superficialis work together to flex fingers Muscles in - some forearm extensors attach to lateral epicondyle posterior - only to be identified as a group compartment of - have superficial (origin = lateral epicondyle and supracondyloid ridge of forearm humerus) and deep (origin R and U) extensors - intra-articular disc

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COMPARATIVE ELBOW AND DISTAL HUMERUS (LECTURE 8)

Elbow Use: - Humans: o Manipulation: Set of elbow makes it perfect for this – places hand in position ideal for manipulation o Non-weight-supporting mostly o Key in throwing (except in cricket) - Apes: o Supports weight during locomotion – climbing, suspension and brachiation or in fist walking (orangutan) or knuckle walking (chimp and gorilla – weight supported on middle phalanges and elbow held straight)

Apes vs. Humans: Structural Similarities and Differences in the DISTAL HUMERUS AND ELBOW

Similarities (when compared to a quadruped) – - Wider trochlea in humans and apes than quadrupeds; in quadrupeds the arm does not pronate/supinate (can only flex and extend) - Large lateral trochlear ridge in humans and apes ** both of the structural features above contribute to stability between humerus and ulna AND frees up the radius for pronation/supination in a variety of elbow postures - Humans and apes share a large amount of extension in their elbow joints compared to other animals, including monkeys. Overall the upper limb is more similar between apes and humans than it is different.

Differences – Feature Structural comparison Functional Significance Humerus - capitulum Faces more posteriorly in apes, can see Allows more hyperextension and a greater arc of movement in apes it from a posterior angle

In humans faces more anteriorly Humerus – lateral In apes, the lateral epicondyle is higher Allows greater LEVER advantage of extensors of wrist and fingers epicondyle and up on the humerus and more (remember they attach to ridge and lateral epicondyle) supracondylar ridge developed

Apes also have a strong supracondylar ridge 5

Humerus – trochlear Apes have a more strongly developed Stabilises elbow joint in hyperextension when knuckle walking AND ridge ridge prevents lateral dislocation Humerus – medial More developed in apes Allows greater LEVER advantage for flexors of wrist and fingers epicondyle Humerus -Olecranon More shallow in humans Allows greater hyperextension in apes fossa Deeper in chimps with a steep/sharp lateral margin Radius - shaft Greater lateral curvature in apes Allows longer pronator muscles therefore greater power in pronation (KNUCKE WALKING) Radius - radial Faces more medially in apes, more Allows a greater mechanical advantage of biceps brachii in apes (attaches tuberosity anteriorly in humans to radial tuberosity) Ulna - shaft Greater medial curvature in apes Allows longer pronator muscles therefore greater power in pronation (KNUCKE WALKING) Ulna - Trochlear notch Wider and more robust in apes Aids transmission of weight during locomotion Dorso-epitrochlearis Extra muscle in apes: Additional strength when climbing (tensor of arm fascia) muscle Originates in Lat Dorsi at top (near ) and inserts into medial epichondyle Forearm length Longer forearm in apes Gives apes better suspensory movement/support

Shorter in humans Allows human to be positioned comfortably in front of body and allows for more precise movement of hands

Hominin Elbow and Distal Humerus Differences Hominin Structure Interpreted Function Ardipithecus Elbow found Does not support knuckle walking – suggests that KW evolved after humans and apes split as no remnants in older hominins Au. afarensis Lack steep lateral margin of Therefore lack a feature important in knuckle walking

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Strongly developed lateral trochlear crest Some adaptations for knuckle walking, climbing and brachiating Moderate lateral epicondyle Au. sediba Long upper limb Does not support KW but possibly some arboreal lifestyle and manipulation Paranthropus robustus Great robusticity of limbs (even more than gorillas) Suggests knuckle walker

Massive markings for brachioradialis Suggests powerful elbow flexion Homo erectus Very similar to modern humans Bipedal not arboreal

Average sized epicondyles

Small trochlear ridge

Radius not bowed Homo neanderthalensis Distal humerus similar to modern humans Not KW b/c too short

Well developed lateral supracondyloid crests for extensor muscles

Radius and ulnar – more powerful Greater power in supination and pronation

More medial position of radial tuberosity Greater lever advantage of biceps in supination

Greater curvature of radial shaft

Pronounced pronator quadratus crest

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