Flashcards in Lecture 11.3 Deck (60):
How is the Dens different in humans and apes?
Dens (odontoid process) of C2 in monkeys and apes is dorsally angled.
In humans it runs in line with the opening of C1.
Why is the Dens' orientation different in Apes and humans?
Apes need to flex their head backwards to maintain the correct position. Humans have a slight extension backwards meaning there isn't much need for a dorsally angled Dens.
How are spinous processes different in apes and humans?
In apes spinous processes in cervical vertebrae are long and end in large knobs.
Why are spinous processes so long in apes?
To attach to the nuccal muscles which maintain the retroflexed head.
Do humans and apes have nuccal ligaments?
Humans have nuccal ligaments whereas apes do not have a well developed nuccal ligament.
Why do humans have a bifid spinous process?
Bifid spinous process in humans allows a greater attachment site for nuccal ligament to hold head in habitual extension.
Do monkeys have a flexible back?
Yes, Monkeys have a flexible back just like humans.
How is the vertebral column oriented relative to the rib cage?
In monkeys the vertebral column is on the outer edge of the rib cage. In humans and age the vertebral column is situated within the thoracic cage.
How are ribs and transverse processes positioned in humans?
Ribs are positioned more posteriorly and the transverse processes are longer and posterior in apes and humans.
Is the sternum wider in apes, humans, or monkeys?
Apes and humans have a wider sternum compared to monkeys.
What is different about the articular facets of apes compared to humans?
Orientation of articular facets in apes does not change in transitional vertebrae.
How does the width of the lumbar vertebrae change in apes?
Width of lumbar vertebrae remains constant in apes.
What kinds of movements can humans do between vertebrae beside flexion and extension?
Conjunct rotation can be done in humans as well as adduction and abduction. (Small amounts approx. 5 degrees) This typically occurs in cervical vertebrae.
What is the structure of the vertebral column like for primates with long tails and for apes?
Primates with tails have long caudal region made up of coccygeal vertebrae (17 - 35 caudal vertebrae)
Apes have a long sacrum and a short coccyx.
What is the size of the lumbosacral angle in humans? Why is it this way?
Lumbosacral angle in humans is a lot larger than in other primates (approximately 60 degrees). This allows humans to pass a larger brained neonate through the pelvis.
It is also important for the formation of the S-shaped curve.
How far into the vertebral canal does the spinal cord extend in animals with a tail?
Spinal cord in animals that have tails goes into caudal vertebrae..
In NW monkeys it goes all the way to the tip with a really good vascular supply.
Typically the spinal cord goes into proximal end of the caudal vertebrae but in monkeys this is not the case.
How are erector spinae muscles different in apes and humans?
Why is this difference important?
Erector spinae are better developed with more muscle bellies in the form of iliocostalis and longissimus in humans.
In apes iliocostalis and longissimus are fused.
Separation of muscle bellies in humans is to control forward and lateral flexion of the trunk.
What is the intermembral index?
Intermembral index is the ratio between humerous + radius and Femur + tibia.
It tells whether an animal is upper or lower limb dominated.
What does the intermembral index tell about animals and what are the significant numbers?
Hindlimb domination = index less than 100
Forelimb domination = index greater than 100
Equal usage of both = index approximately 100.
How are different apes scored on the intermembral index?
Vertical clingers and leapers have lowest intermembral index followed by quadrupeds then brachiaters have a higher than 100 intermembral index.
What is the human intermembral index?
How is the glenoid socket different in apes compared to humans??
Apes have a deeper glenoid socket (more stability).
Humans have shallow glenoid socket.
What is different about the supraglenoid tubercle in apes compared to humans?
Supraglenoid tubercle is more projected and prominent in monkeys limiting hyperflexion of the arm.
In apes this projection is absent and this allows above arm flexion.
How are the greater and lesser tubercles oriented in monkeys and humans? How does this effect mobility of the arm?
Greater and lesser tubercle in monkeys is higher than in humans this limits ability of arm to flex above a certain point. This mechanism limits abduction of the arm as well.
How is the spine of the scapula different in brachiators and how does this affect the acromion process of the scapula?
Spine of scapula is longer in brachiators and acromion process is positioned further laterally. This allows greater abduction in apes. In humans it is smaller in size.
Where do the deltoid muscles originate and insert?
Deltoid muscles originate at the spine of the scapula and insert onto the deltoid tuberosity of the humerus.
How does the orientation of the deltoid tuberosity in humans and apes affect their mobility?
Deltoid tuberosity is lower in humans and apes allows for more range of motion (greater moment arm) compared to monkeys
How is the supraspinous fossa:infraspinous fossa ratio different in humans compared to apes?
In humans the supraspinous:infraspinous fossae ratio is smaller than in apes.
What happened to the supraspinatus and deltoids in humans compared to apes?
Supraspinatus and deltoids reduced in size and action in humans.
How are the rotator cuff muscles different in apes compared to humans?
apes have stronger rotator cuff muscles than humans.
How do the trapezius and the serratus anterior muscles insert onto the scapula and how does this effect the motion of the scapula?
Fibers of trapezius insert further more laterally in apes and serratus anterior fibers insert more medially. Net effect of this is that the scapula can perform more medial rotation.
How is the insertion of the triceps onto the scapula compared to humans?
Long head of triceps in apes has a wider insertion on the scapula in apes.
Which animals have the dorsoepitrochlearis?
Dorsoepitrochlearis is present in apes and monkeys but not in humans.
Where does the long head of the triceps originate?
The long head of the triceps originates at the infraglenoid tubercle of the scapula.
Where is the dorsoepitrochlearis located and what is it's function?
Dorsoepitrochlearis originates at the intertubercular groove near the insertion of latissimus dorsi.
It is located deep to the long head of the triceps. Important to keep arm in abduction and cranial rotation.
How is the olecranon fossa different in humans compared to apes? Why does this difference exist?
Olecranon fossa is deeper in apes. The olecranon process is shorter than coracoid process allowing chimps to hyperextend.
In humans olecranon process is also lower in the trochlear notch.
How do chimps prevent lateral dislocation of the radius?
Chimps have a large lateral trochlear ridge to prevent lateral dislocation.
How is the trochlear notch different in humans compared to chimps?
In apes the trochlear notch does not project too far anteriorly.
In humans olecranon process is also lower in the trochlear notch.
What mechanism do knuckle walking apes use to prevent hyperextension of the distal radiocarpal joint?
In apes the distal radius has a stronger projection dorsally allowing more stability when knuckle walking this prevents hyper extension of the wrist.
How are human hands different to apes?
Humans have more broad and flat phalanges. This allows for a power grip in humans.
Apes use hook grip which uses the long phalanges to grip the branches. Thumb is small in size and vestigial.
What muscles do apes use in their hand for the hook grip? Do humans have any of these muscles?
Contrahentes muscles allow for hook gripping in apes and many of these muscles exist in apes. Humans only have adductor pollicis
Which hand muscles are better developed in apes?
Apes have better developed FDS and FDP.
Which hand muscles are better developed in humans than in apes?
Humans have a better developed FPL and FPB than apes.
How is the weight resistance in upper and lower limbs different in humans and apes?
Lower limbs in humans take up more weight than upper limbs.
In apes it's the opposite.
How does gravity affect posture in humans?
Gravity causes rotational axis which are resisted by ligaments and muscles.
What is the first phase of the gait cycle?
Heel strike (dorsiflexors and quads contract)
What phase follows heel strike?
The loading response (the foot is planted on the ground while body weight is shifted forward)
What phase follows the loading response?
Midstance (full contact with the ground)
What phase follows the midstance phase?
Terminal stance (heel off and plantar flexors of the leg are utilized)
What phase follows the terminal phase?
The preswing phase (toe leaves the ground and gluteal muscles contract to keep hip from tilting)
What phase follows the preswing phase?
The swing phase (thigh is flexed and quads contract preparing for heel strike)
Why do humans have this gait cycle?
The human gait is very energy efficient
How is the greater sciatic notch different in humans compared to apes?
Greater sciatic notch is deeper in humans than in chimps.
How is the function of the gluteal muscles different in apes compared to humans?
In apes gluteus medius and minimus is an extensor
How is the bicondylar angle different in humans compared to apes?
bicondylar angle is more oblique in humans than apes allowing for a valgus knee
How is the neck of the femur different in humans compared to apes?
Humans have a longer neck of femur than apes
How is the distal femur and the condyles different in humans compared to apes?
femoral condyles in humans are very large and eliptically shaped
How is the congruence between the femur and the tibia different in humans compared to apes?
Congruence between distal femur and tibia is greater in humans
How is the patella orientation different in humans compared to apes?
Patella is further forward in humans than in apes.