Lecture 7: The Upper Limb Flashcards
What does stylopod refer to?
Arm (humerus)
What does zygopodium refer to?
Forearm (radius + ulna)
What does autopodium refer to?
Wrist + hand
How does the positioning of the upper limb in pronograde posture allow for quadrupedal walking?
Its retroflex positioning leaves the upper limb elbow joint always slightly flexed
Describe the typical quadrupedal mammal shoulder arrangement, such as is seen in the baboon
Shoulder is placed on the side of the rib cage with the scapula balanced on top of the humerus
The rib cage is narrow side-to-side and deep front to back
Describe the chimp shoulder in terms of chest shape, scapula placement, clavicle characteristics, and humerus placement
Chest is wide front to back
Scapula is placed on the back
Clavicles are long and angled
Humerus on the side of the rib cage
Describe the Homo erectus shoulder in terms of chest shape, scapula placement, clavicle characteristics, and humerus placement
Chest is wide front to back
Scapula is placed on the SIDE
Clavicles are long and HORIZONTAL
Humerus is pulled forward, limiting backwards rotation of the arm
Describe the Homo sapien shoulder in terms of chest shape, scapula placement, clavicle characteristics, and humerus placement
Chest is wide front to back
Scapula is placed on the BACK
Clavicles are SHORT and horizontal
Humerus is placed on the side of rib cage so we can pull our arms back to throw/run
True or false: the humerus is not considered part of the pectoral girdle
True
Upward and downward rotation of the scapula changes the orientation of what cavity?
Glenoid
The position of the pectoral (shoulder) girdle on the thorax is more ________ in quadrupeds, with a clavicle that accommodates a more ____________ positioned shoulder.
The position of the pectoral (shoulder) girdle on the thorax is more __________ in climbers, suspensory, and orthograde/bipedal forms, with curved, thicker clavicle that accommodates a more _________ oriented shoulder with a more cranially oriented glenoid.
Lateral; vertically
Posterior; laterally
In terms of scapular shape, the glenoid of apes and humans is _________ to accommodate more shoulder mobility.
In quadrupedal monkeys, the glenoid is _________ is shape.
In both cases, the shape of the humeral head mirrors the glenoid (it is more ___________ in apes and humans and more _____ in monkeys).
Rounder
Pririform
Globular; ovoid
In terms of the shape of the scapula, quadrupeds have a ________ scapula cranially-caudally but ___________ from the vertebral border to axillary border to facilitate movement during quadrupedal locomotion.
Climbers and suspensions forms have ________ scapulae with a more ________ oriented glenoid to allow greater mobility and rotational movement.
Shorter; broader
Long; cranially
In particular, lengthening of the infraspinous portion of the scapula does what?
Provides greater attachment for muscles that superiorly rotate the glenoid, raising the arm over the head
What scapular muscle keeps the scapula against the rib cage and also superiorly rotates the glenoid?
Serratus anterior
What aspect of humerus bone structure offsets the humeral head from the distal articular surface and to what degree does this occur in humans?
Humeral torsion - the shaft of the humerus is twisted
The highest degree of humeral torsion is seen in humans
The progressive increase in humeral torsion is associated with what locomotion behavior in apes?
Climbing and suspension
It is also thought to be an adaptation for weight-bearing in knuckle walking apes and possible tool use in early hominins
The idea that humeral torsion in humans is related to tool use corresponds to the _________ oriented shoulder and ___________ oriented elbow; both essential for mobility and manipulation of the upper limb. Humeral torsion is present ________ in ontogeny and affects placement of the ___________ _________ on the humerus, which accommodates the tendon of the ___________ _________.
Laterally Anteriorly Early Bicipital groove Biceps brachii
The human upper limb is adapted for use in a lowered position and is less powerful in a raised position. Humans are not powerful climbers and do not naturally suspend.
We have relatively _______supraspinous fossa and _______ infraspinous fossa with ________ rotator cuff muscles.
Upward rotation of the scapula is more like that of quadrupeds. We have lateral facing shoulder joints (instead of cranial) and the _______ end of the clavicle lacks the cranial twist seen in apes.
Small; large; small
Lateral
The shoulder adaptations from apes to humans may lead to what syndrome associated with repetitive overhead motion?
Shoulder impingement syndrome
What aspect of the elbow joint limits the degree of extension? - is this a quadrupedal or climbing/suspension trait?
Size of the olecranon (longer = less extension) which is a quadrupedal trait
How might stronger flexion at the elbow be accommodated anatomically in climbers?
Stronger flexion is accommodated by a higher coronoid process (attachment point for the brachialis - main elbow flexor)
In terms of comparing the elbow joints of humans and apes, they are overall similar due to similar distal humerus. Differences reflect weight bearing and strength/lever advantages of _________ musculature. Apes have deeper _________ _______ for hyperextension during weight bearing knuckle walking. Apes lateral ___________ ___________ is strongly developed to help stabilize the elbow joint during hyperextension when knuckle walking
Brachial
Olecranon fossa
Trochlear ridge
The human hand and wrist:
of carpal bones =
of metacarpals =
of phalanges =
Carpals = 8 Metacarpals = 5
Phalanges = 14 (5 digits, each has 3 segments except thumb which has 2)
Compare the general primitive carpus with modern human carpus
Reduced wrist bones due to fusion
In terms of flexion and extension at the wrist joints:
40% of flexion occurs at the ______________ joint while 60% occurs at the ____________ joint.
33% of extension occurs at the __________ joint while 67% occurs a the _____________ joint.
Radiocarpal; midcarpal
Midcarpal; radiocarpal
Radial and ulnar deviation (to achieve abduction and addiction) mostly occurs at which joint?
Midcarpal
The “power grip” consists of strong flexion of what joints and muscle?
MP and IP joints
Flexor digitorum profundus
Compared to apes, we have much more dexterity to our thumbs due to increased musculature and nerve innervation. The bulge of intrinsic thumb muscles that allows for this dexterity is called the __________ __________
Thenar eminence
African ape knuckle-walking features include:
Limited degree of wrist _____________
Limited metacarpophalangeal joint ___ and ____ dorsiflexion
Deeply __________ distal radial surface
Dorsal __________ of metacarpal heads
Relatively _________ proximal phalangeal segments
Dorsiflexion (extension) II and V Concave Expansion Short
Orangutans do not knuckle-walk due to _______ and _________ digits; what is their alternative to knuckle-walking?
Long; curved
Orangutans fist-walk
Orangutans have the following adaptations to climbing:
_________ and _________ phalangeal segments
Metacarpals ____ and ____ show a greater degree of curvature
__________ bony cortex of all metacarpals
__________ length of the 4th digit relative to other digits
Long; curved
II and V
Thicker
Increased