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COMPARATIVE ANATOMY OF BRAIN,
SKULL, BONE, MUSCULOSKELETALSYSTEM, GAIT AND POSTURE-
PLANTIGRADE AND ORTHOGRADE
AMIT
POSTGRADUATE 1ST YEAR
PROSTHODONTICS
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CONTENTS
INTRODUCTION COMPARATIVE ANATOMY OF BRAIN
COMPARATIVE ANATOMY OF SKULL
COMPARATIVE ANATOMY OF BONE COMPARATIVE ANATOMY OF
MUSCULOSKELETAL SYSTEM
GAIT AND POSTURE- PLANTIGRADE AND
ORTHOGRADE
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INTRODUCTION
Anatomically, we are very similar to apes andeven to monkeys
But we are not identical: Humans are fully
bipedal, for example, while chimps are not. We have two arches in our foot; chimps do
not.
Therefore we need to compare our ownanatomy with (a) other living primates and (b)fossil hominin forms.
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Structure of the Brain
Frontal Lobe: The lobe that allows us to think andplan ahead
Motor Cortex: The strip along the edge of the motor
cortex that moves the facial muscles (lips, tongue,vocalization) and the arm,
hand, and finger muscles
Parietal Lobe: The lobe that
enables us to touch and taste
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Structure of the Brain
Occipital Lobe: The lobe of the brain thatenables us to see
Temporal Lobe: The lobe that enables us to
hear Olfactory Bulb: The part
of the brain that enables us
to smell
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The Motor Cortex
Lower part: The strip regulates the facial and oralmuscles
They include the tongue, the lips, the organs forvocalization, and the jaws
These are related to the speech function Upper part: The strip regulates the arm, the hand,
and their fingers
These are related to the tool manufacture and use
functions.
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Parts of the Brain: Motor Cortex
Related to Language: Lower
Part
Lips
Tongue Vocalization
Related to Tool Making and
Use: Upper part
Fingers and Thumb Hand
Arm
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Language Functions of the Brain
The language functions all occur on the left hemisphere of the
brain.
Brocas Area functions to process the generating of speech
Notice that it is located at the base of the motor cortex, whichhandles the tongue, vocalization, and lip movements
Wernickes Area functions to
process the reception of speech
Notice its location in thetemporal lobe,which processes
hearing
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Language Functions of the Brain:
Description II The angular gyrus is the part that coordinates all the
sense functions housed in the brain
They coordinate the senses of sight from the occipitallobe, of the touch and taste of the parietal lobe, of the
smell from the olfactory lobe, and of hearing from thetemporal lobe
Its function for language is to translate all the sensoryinformation into the sense of hearing so we can
assign meaning to speech.
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Parts of the Brain: Language
CentersParts of Cerebrum
Frontal Lobe
Motor Cortex
Brocas Area
Temporal Lobe
Auditory Cortex
Wernickes Area
Arcuate Fasciculus
Parietal Lobe
Occipital Lobe
Angular Gyrus
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Human Skull: A Description
The forehead is high, making room for the
frontal lobe
The skull is rounded, allowing a greater
volume for the entire brain
There is no brow ridge or supraorbital torus
The jaw does not jut forward; it is notprognathous
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Human Skull: Bones that Cover the
Lobes
The bones of the skull are named after the
lobes they cover
The frontal bone covers the frontal lobe
The parietal bone covers the parietal lobe
The occipital bone covers the occipital lobe
The temporal bone covers the temporal lobe Refresh your memory: what are each of these
lobes for?
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Human Skull: The Diagram
Note the following:
High forehead
Rounded skull
No brow ridge
Chin is present
Teeth are small
The bones are namedafter the lobes of the
brain they cover
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Comparative Primate Anatomy:
Human and Chimpanzee
In the next diagrams, the differences are significant tobiological capacity for culture
The area for brain of a chimp is more limited than
human brain because of its sloping forehead andtheheavy supraorbital torus that covers much of theforehead
The chimp jaw has a prognathism absent in humans
Chimps have larger canine teeth than humans; somuch so that there is a diastema (gap) for theopposite canine to fit.
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Skull Morphology: Chimp and
Human
Note the following Larger brow ridge (supraorbital torus) of chimp compared to human
Sloping forehead of chimp compared to human
More prognathous (jutting) jaw of chimp compared to human
Larger canine and gap (diastema) of chimp compared to human
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Comparative Brain Structure:
Human and Chimpanzee the human brain has a Brocas area for processing
speech.
The chimp brain has a Brodmans area, where callsmay originate, but no speech
Our Wernickes area, which receives speech,is atthe same place as the planum temporale among thechimps
The chimp brain is much smaller than humans400
cubic centimeters compared with our 1400 cc. The frontal lobe of the chimp is smaller than the
humans, partly owing to the sloping forehead
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Human and Chimp Skulls
Compared: Brain Structure Compare the following
Chimps brain is much smaller(400cc vs. 1400cc)
It has reduced frontal lobe
It has no Brocas or Wernickesarea
It does have Brodmanns area10, where calls may originate
but no speech It does have planum temporale,
where calls are receivedbutnot processed as language
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What This All Means
Our brains are larger than the chimps
We have a well-developed frontal lobe
We have well developed language areas:Brocas and Wernickes area
The motor strip is more well developed among
humans than among chimps
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COMPARATIVE ANATOMY
OF BONES
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Comparative Anatomy: Hand
Structure
Our fingers are straight; that of the chimps and
other apes are curved
We have a much longer thumb than do the
apes
Importance: we are capable of a more precise
grip than the apes
This implies that we can make finer tools than
those apes who can make and use tools
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Human Hand Structure: Diagram
Note The Following:
Our digits are straight
Our thumb is opposable
The thumb is long
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Ape and Human Hands:
Diagram Hands of orangutan, chimpanzee, gorilla and human
Note the following:
Our thumbs are longer than the others
We can make a finer grip than the others can
Less visible: apes digits are curved, ours are straight
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Power and Precision Grip
Note the Following:
Power grip: Fingersand thumbs wrap
around the object Precision grip:
Forefingers and thumbhold the object
Importance: We can dofiner work compared tononhuman primates
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Chimp and Human Locomotion
Compared
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Vertebral Column and Pelvis
Note the following: Human vertebral column
is S-shaped, supportingthe upper torso
Chimp vertebral column isbow-shaped
Human pelvis, with ilium,is bowl-shaped; musclesfrom the thigh keep him
upright Chimp pelvis is long, with
flat ilium
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Pelvis and Femur Longer ilium of chimp
Shorter, more curved
ilium of human
Straight vertical
orientation of chimpfemurs, which do not
support the upper body
well
Inward angle of human
femurs, which support
the upper body more
efficiently
http://images.google.com/imgres?imgurl=http://www.mc.maricopa.edu/dept/d10/asb/anthro2003/origins/hominid_journey/pictures/chimp_afar_pelvis.gif&imgrefurl=http://www.mc.maricopa.edu/dept/d10/asb/anthro2003/origins/hominid_journey/afarensis4.html&h=207&w=288&sz=25&hl=en&start=12&sig2=5wp1rfL2ueYJPCDfWHsyuw&tbnid=fjKz94WJ_5q01M:&tbnh=83&tbnw=115&ei=1Zh0Roy1BqWOggPyh8y1Aw&prev=/images?q=Chimp+and+Human+Pelvis+and+Femur&gbv=2&svnum=10&hl=en&sa=G7/31/2019 Comparative Anatomy of Bone ,Brain,Skull,Muskuloskeletal System,Gait and Posture
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Foot Structure
Note the following:
Large toe of chimp foot(right) is opposable to otherdigits
Large toe of human foot(left) is aligned with otherdigits
Ankle bones (tarsals) ofhuman food are larger andmore rigid than the chimps
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Foot Arch: Longitudinal and
Transverse
Note the following:
Longitudinal arch that runs
from the first metatarsal to
the calcaneus (heel bone)
Large tarsals to the rear
contribute to the rigid
structure of the foot and its
arch
Transverse arch can be
inferred from lower
placement of outside foot to
the instep
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Chewing Mechanism
The next diagrams compare human dentition(structure of teeth) with that of the chimps
Our overall dental arcade (arrangement of teeth) ismore rounded (arc-like) than the chimps
Chimpanzee have a more rectangular dental arcade,with the back teeth more parallel
Our teeth are much smaller than the chimps
We have small canines (jagged teeth) Chimps have large canines, so large that they need a
gap (diastema) in the opposite jaw for them to fit
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Human Dentition: Diagram
For each jaw (upper or
maxilla or lower or
mandible:
Incisors (4) in the frontfor cutting food)
Canines (cuspid) (2) for
piercing
Premolars (4) for light
grinding of food
Molars (6) in back for
heavy grinding of food
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Chimp and Human Dentition
Note the following:
Dental Arcade: Humans are arc-like; apes, parallel back
teeth
Canines and Diastema (gap): Apes have larger canines
and gaps in opposite jaw to fit them; humans do not
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MUSCULOSKELETAL
SYSTEM
Muscles of head and neck - human ancestors
had larger, stronger jaw muscles attached to the
skull which would be expected with a diet rich in
fruit and plants.
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Muscles of head and neck
Human ancestors had more muscles connecting
the skull, neck, and shoulders/back which caused
their neck and skull regions to appear to
sag,These diminished muscles allow the humanhead to be held in its current upright position
and lets the occipitofrontalis muscle, or the
forehead, to function as an aid to expressions
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Muscles of Upper body/back
Humans became taller as the years passed after
becoming bipedal which lengthened back muscles at
the base of the tail bone and hips which in effect
made them weigh more, further hampering theirabilities in the trees
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Muscles of Upper body/back
It is well known that the Homo sapien line of primates
developed the opposable thumb which opened the door
to many muscle functions not yet possible in the hand
and other upper body regions The stretching muscles ofthe forearms whose tendons allowed the human to
concentrate its force and abilities within his/her hands
and fingers contributed to great new abilities..
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Overall, upper body muscles developed to deal
with more activities that involved
concentration of strength in those muscles such
as holding, throwing, lifting, and running withsomething to assist in escaping danger,
hunting, and constructing habitats and shelters
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M l f L b d /b l
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Muscles of Lower body/below
waistBy having to center the force of gravity on two feet, the human
thigh bone developed an inward slope down to the knee
gluteal abductors to adapt to the stress and build the necessary
muscle.
This allows the human to manage their balance on a single foot
and when in-stride during walking..
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M l f L b d /b l
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Muscles of Lower body/below
waist
The plantaris muscle
grab and manipulate objects like chimps do, has
adapted to its new evolutionary role
becoming so underdeveloped that it cannot gripor grab anything, the foot has grown more
elongated as a result and now 9% of humans are
born without it.
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GAIT AND POSTURE
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GAIT
Gait is the pattern of movement of the limbs of
animals, including humans, during locomotion
over a solid substrate
Human gait is defined as bipedal, biphasic
forward propulsion of centre of gravity of
human body, in which there is alternate
sinuous movements of different segments ofthe body with least expenditure of energy.
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Bipedalism vs. Quadrupedalism
Homo sapiens is the only mammal capable ofbipedalism, or the ability to stand and walk entirelyon two feet.
Kangaroos stand on two feet, but they hop rather than
walk and their forepaws are too small for anyfunction.
Chimpanzees can walk on two feet, but not veryefficiently; they are closer to quadrupedalism, or theability to move around on four feet.
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Bipedalism: Diagram
We are the only mammalsthat can stand and walk ontwo feet
Apes are semi-bipedal, butuse their knuckles to get
around (top photo) The bottom photo compares
the quadrupedalism of ahuman with that of a chimp
Notice the human is on his
knees, not just his feet The chimp is using its hind
feet, not its knees.
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Advantages of Bipedalism
Efficient locomotion
Freeing of hands for many proposes:
Foraging and hunting/scavenging
Tool making and use
Care and provisioning of offspring
Increased height for viewing across landscape:
Tracking migrating herds
Predator avoidance
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POSTURE
Posture is the position in which you hold your
body upright against gravity while standing,
sitting or lying down
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PLANTIGRADE POSTURE
plantigrade locomotion means walking with the podials and metatarsals flat on the ground.
The leg of a plantigrade mammal includes the bones of the upper leg (femur/humerus)
and lower leg (tibia and fibula/radius and ulna).
Humans are an example of a plantigrade species.
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1)stability andweight-bearing
ability;2)plantigrade feethave the largestsurface area.
1)With more bonesand joints in the
foot, the leg is bothshorter and heavierat the far end, whichmakes it difficult to
move rapidly.
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ORTHOGRADE POSTURE
Orthograde is a term derived from Latin [ortho (upright) +
gradi(to walk)] that describes a manner of walking which is
upright, with the independent motion of limbs.
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ORTHOGRADE POSTURE
Monkeys are primarily arboreal, and they have a
tendency to walk with their limbs swinging in parallel
to one another.
This differs from the manner of walkingdemonstrated by the apes. Chimpanzees, gorillas, and
humans, when walking, walk upright, and their limbs
swing in opposition to one another for balance (unlike
monkeys, apes lack a tail to use for balance). Thisupright locomotion is called "orthograde posture".
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REFERRENCES
Matt Cartmill, Fred H. Smith The Human
Lineage pg-110-130
Grays Anatomy 40th edition page no.- 546,661
Guyton and Hall Textbook of Medical
Physiology 12th edition
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THANK YOU