Comparative Anatomy of Bone ,Brain,Skull,Muskuloskeletal System,Gait and Posture

7/31/2019 Comparative Anatomy of Bone ,Brain,Skull,Muskuloskeletal System,Gait and Posture

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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=G


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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
http://www.netterimages.com/image/4012.htm


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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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http://upload.wikimedia.org/wikipedia/commons/1/13/Plantigrade.png


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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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Comparative Anatomy of Bone ,Brain,Skull,Muskuloskeletal System,Gait and Posture

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