Slide 1:By Feryal Jamal Kherissat HAND EVOLUTION


OBJECTIVES :OBJECTIVES


THE SKELETON :THE SKELETON The skeleton of the hand and wrist consists of: 19 long bones : 5 metacarpals 14 phalanges 8 carpal bones


Slide 4:The fixed elements consist of : distal carpal row second and third metacarpals. The mobile elements consist of : phalanges Thumb The first metacarpal makes an angle of about 45 degrees with the second metacarpal in the sagittal plane and is independent. This allows the thumb ray to oppose the other four digital rays.


HAND AND FINGERS JOINTS :HAND AND FINGERS JOINTS The wrist contains: The radiocarpal: formed between the radial head and the proximal row of carpal bones. It allows adduction/abduction, flexion/extension, and circumduction. Midcarpal joints: between the proximal and distal carpal rows. It acts as a hinge joint with one degree of freedom. Distal radioulnar joint : a pivot joint between the head of the ulna and the ulnar notch of the radius. It provides supination and pronation which is the most important functional movement of the wrist.


Slide 8:The finger contains: 5 carpometacarpal joints (CMC). 5 metacarpophalangeal joints (MCP). 4 proximal interphalangeal joints (PIP). 5 distal interphalangeal joints (DIP).


TYPE OF MOVEMENTS :TYPE OF MOVEMENTS Finger movement: Flexion/ extension. Adduction/ abduction. Isolate movement. Wrist movement: Flexion/extension. Deviation.


Finger MCP flexion (A), PIP flexion (B), DIP flexion (C), and MCP, PIP, and DIP extension (D). :Finger MCP flexion (A), PIP flexion (B), DIP flexion (C), and MCP, PIP, and DIP extension (D).


Finger MCP abduction (A) and adduction (B). :Finger MCP abduction (A) and adduction (B).


EVOLION OF FORELIMB :EVOLION OF FORELIMB Function of forelimb: To support the weight of the body in quadrupedal locomotion. To suspended the weight of the body in brachiation. To manipulates objects.


THE PECTORAL GIRDLE :THE PECTORAL GIRDLE PRIMATES: Two-bonded pectoral girdle….....…move 40 degree about the sternocalvicular joints in each of two plans. Scapula can move freely in relation to the clavicle about the acromioclvaicular joints. The two joints allow the scapula to move over the surface of the thorax in both the vertical and horizontal plans.


Slide 19:The scapula moves forward round the thorax in pushing or thrusting. The scapula moves forward or upward in climbing. The scapula can rotated so that the glenoid cavity can face in different direction………… allow the arm to rise vertically……….. Important in brachiating. Change from quadrupedalism to brachiation is reflected in the form of scapula and its masculature.


Slide 20:Type of scapula: Quadrupedal scapula : short and squarer in proportion, with a downward- glenoid cavity. Brachiating scapula: elongated, with an upward- glenoid cavity. Human scapula: elongated, with downward- pointing glenoid cavity.


The muscles: :Muscles are better developed in brachiators than in quadrupeds ……….. Man is close to brachiators. Increase in length in bony lever to which these muscles are attached……….. The insertion area of the muscles on the scapula tend to move away from the central point around which the scapula rotates. The muscles:


UPPER ARM & FOREARM :UPPER ARM & FOREARM The plan of articular head of the humerus in relation to the elbow joint: Quadrupedal: the center line of the ball joint of the humerus, which fits into the glenoid cavity, is just about at the right angle to the elbow. Brachiating: the humerus has twisted so the angle between elbow and head is near 30 degree, and the head point inwared……… arm able to move laterally as well as backward and forward. The trochlea, allow full extension of the forearm and is relatively broad……… given greater lateral stability. Modern man: share this character with the branchiating group


Australopithecus Chimpanzees anamensis humans :Australopithecus Chimpanzees anamensis humans


Mean Arm length (Humerus and radius) as a % of Trunk Length :Mean Arm length (Humerus and radius) as a % of Trunk Length


Correlates of brachiation in the forelimb of higher primates :Correlates of brachiation in the forelimb of higher primates


The man share 4 characters with brachiaters: :The man share 4 characters with brachiaters: A relative long and stout humerus. Relatively large arm- raising muscles and a low point of insertion of deltoid. The head of the humerus pointing inward rather than straight backward. A fairy broad trochlea at the elbow.


EVOLUTION OF :EVOLUTION OF HUMAN HAND


chimpanzees are genetically our nearest relatives :chimpanzees are genetically our nearest relatives Chimpanzees fingers: Metacarpal and carpal bones are elongated. Third and fourth metacarpals, which absorb the highest compression during knuckle-walking, are especially robust. Human fingers: The palm and fingers are shorter. Apart from thickening of the fifth metacarpal and enlargement of its base, the balance of strength and robusticity has shifted radially, to the thumb, second and third fingers.


Slide 32:Bones of the chimpanzee (left) and human hands


Slide 33:Both proximal and middle phalanges are curved toward the palm to withstand stress from gripping limbs during arboreal locomotion. The finger tips are cone-shaped, and lack broad apical tufts. The fingers have lost their curvature. The distal phalanges have gained large apical tufts which support broad, palmar, fibrofatty pads that distribute pressure during forceful grasping and whose deformation accommodates the pads to uneven surfaces.


Slide 34:1st row: Phalanges shown in lateral view. Curvature in extended position decreases toward the human. 2nd row: Terminal phalanx increases in breadth.


Slide 35:The thumb is small. Thumb phalanges and metacarpals are slender and short and the intrinsic muscles of the thumb, underlying the thenar region of the palm, are small. Thumb is weak and relatively immobile. The thumb is longer. The intrinsic thumb muscles are larger and three new muscles add strength and control to thumb movements. The thumb metacarpal articulates with the carpals in a saddle joint which in combination with remodeling in the metacarpal–phalangeal joint allows its distal pad to be placed against those of the other fingers, providing full opposability.


Relative length of thumb, and angle between thumb and index finger, increase toward human. :Relative length of thumb, and angle between thumb and index finger, increase toward human.


Mean proportion of the hand and thumb in primates. :Mean proportion of the hand and thumb in primates.


Human Chimpanzee Gorilla Orangutan (Homo sapiens) (Pan troglodytes) (Pongo pygmaeus) (Gorilla gorilla) :Human Chimpanzee Gorilla Orangutan (Homo sapiens) (Pan troglodytes) (Pongo pygmaeus) (Gorilla gorilla)


Pan :Pan


Pango :Pango


Gorilla :Gorilla


The opposability of the thumb in a chimpanzee and in a man and average of some proportions of the hand. The total thumb length is much shorter in relation to the total length in the ape than in man, but in relation to the trunk length the thumb has the same length in both, while the total hand length has greatly increased in ape (phalangeal and metacarpal parts) :The opposability of the thumb in a chimpanzee and in a man and average of some proportions of the hand. The total thumb length is much shorter in relation to the total length in the ape than in man, but in relation to the trunk length the thumb has the same length in both, while the total hand length has greatly increased in ape (phalangeal and metacarpal parts)


Slide 43:Flexor pollicis longus muscle absent. Flexor pollicis longus muscle is the most powerful thumb muscle in humans. It flexes the distal phalanx of the thumb and maintains the orientation of its pad toward the fingers against pressure. Also : the deep head of the flexor pollicis brevis and the first volar interosseous muscle


The muscle of human and Chimpanzee thumb. :The muscle of human and Chimpanzee thumb.


Slide 45:Right hand of a modern human shown in anterior (palmar) aspect. Strong muscles (adductor pollicis and abductor pollicis) move thumb towards and away from palm. Saddle joint at trapezium and 1st metacarpal allows thumb to be rotated within a 450 cone and to be placed in opposition to all other digits.


THE HAND OF PRIMATE :THE HAND OF PRIMATE Five fingered hand. Each phalanx carries a claw. Six Volar pads of friction skin on the palm and one terminal pad on each phalanx. A small skin projection over the wrist (papilla) act as a tactile sense organs: long hairs (carpal vabrissae ) growing from it and form an extremely sensitive but undiscriminating tactical sense organ. As volar pad increase in area and sensitivity in primate evolution, the importance of carpal vabrissae decrease.


Slide 47:The hand of primates: Carpal papilla on the wrist of Tupaia (The tree shrew). Increase in the area of the volar skin in the higher primates. Elongatede thumb of Indria and the short thumb of Pongo.


CLAW AND NAILS :CLAW AND NAILS Primate nails were evolved in association with opposable first digits of hands. Nails splaying out laterally of each terminal phalanx so as to accommodate the broad tactile sensory digital pad. This is necessitated broadening the nail from the claw. Differences in the mechanical requirements of claws and nails led to reduction in thickness of the deep layer of the claw, its main component in other mammals. This layer was lost entirely in nails unless it is represented by the thin ventral plate of the human nail. Nails were evolved from claws by differential growth


How to achieve a hold on a branch: :How to achieve a hold on a branch: The thumb diverge from the phalanges and can be opposed to them round the branch. The lengthening of the phalanges and, a reduction in the thumb. Length and thickness of radius and ulna as in humerus. The shoulder girdle can be rotated to allow the arm to rise vertically. Lengthened scapula. Well developed muscles.


GRASPING HAND :GRASPING HAND The hands of man are specially well adapted for holding objects as well as for delicate manipulations because neither have the thumb shortened, as in many monkeys, nor have the finger II-V been lengthen.


Opposability index = length of thumb / length of index finger :Opposability index = length of thumb / length of index finger low number long first finger relative to thumb Primates range between 40% and 65% Humans ~60%


THE TWO UNIQE HUMAN HAND GRIPS :THE TWO UNIQE HUMAN HAND GRIPS Power grip: The clamp around the cylinder is formed by the partly flexed fingers and the palm, counter pressure being applied by the thumb, which is wrapped over the dorsum of the fingers, where it acts as a buttress to reinforce the grip.


Slide 54:Pprecision grip: The terminal pad of the thumb forms one jaw of a clamp, the other being formed by the fingertip pads. Large objects held in this way involve all the fingers, but smaller ones require only the thumb, index and middle fingers with the fourth and fifth fingers providing lateral stability.


A fully opposable thumb gives the human hand its unique (left) power grip (object grasped between fingers and palm while thumb applies counter pressure), (right) precision grip (object manipulated with tips of fingers and fully opposable thumb). :A fully opposable thumb gives the human hand its unique (left) power grip (object grasped between fingers and palm while thumb applies counter pressure), (right) precision grip (object manipulated with tips of fingers and fully opposable thumb).


Slide 56:Though the monkeys have an opposable thumb, its only in man that the thumb is long enough and divergent enough to carry a heavy muscular. The length and the strength make possible a precision grip, strong yet delicate. The hand no longer functioning to grasp branches, the metacarpals and phalanges straighten out in the course of human evolution, and the terminal segment broaden.


Slide 57:THANK YOU