Langdon Ch6

how many lumbar vertebrae do humans have?

5

Bear a greater proportion of body weight than superior segments

5 Lumbar vertebrae

What is the human adaptation that is responsible for the characteristics of our spine?

Bipedalism: Disproportionate size of lumbar vertebrae is uniquely human adaptation to bipedalism. Receives greatest stress from bipedal posture

How many vertebrae does Homo ergaster have?

also has 5 lumbar vertebrae

There are at least four requirements that the human spine must meet. Some of these requirements require conflicting solutions. Thus, when everything is considered the human vertebral column is a series of_____

compromises

ribs

found only on the thoracic region in mammals.

A major requirement that the human vertebral column must meet is supporting weight against ___________

gravity

mammalian limb position

permits active flexion of the spine in the sagittal plane.

bipedalism

requires that the human vertebral column have lateral ligaments for reinforcement to ensure smooth movement.

thoracic region

ribs attach to this region

The curves of the spine help to distribute and stabilize weight by bringing the ____ closer to the center of the body.

spine

cervical region

supports and balances the head.

axial skeleton

the portion of the human skeleton that consists of the bones of the head and trunk of an organism.

another name for the spine

the vertebral column (not the spinal cord)

human vertebral column

this is the best argument against intelligent design.

spine

this structure must provide mobility to the trunk.

sacroiliac joint

transmits the weight of the body to the feet.

lumbar region

vertebral region that bears most of the bodyʼs weight.

coccyx

vestige of the caudal vertebrae that formed an ancestorʼs tail

What requirements must the human spine meet?

*support body weight against gravity *provide substantial mobility to the trunk

Compare the limb position of amphibians and reptiles with that of mammals.

-Amphibians+Reptile limbs splay laterally, much more efficient for swimming. Less effecient for supporting trunk on land -Mammal limbs underneath trunk. Permitted active flexion of the spine in a sagittal plane

What other functions must the human vertebral column perform.

-Anchors muscles and protects the spinal cord

Describe the vertebral column of the australopiths.

-Lumbar lordosis is present. -Lumbar vertebrae appear surprisingly small and not adapted for habitual weight-bearing of normal human bipedality. -Skeletal anatomy suggests a unique but poorly understood bipedal gait. Less well adapted for sustained travel.

three main regions of the axial skeleton.

-Spine, ribs, and skull

Describe the curves of the human vertebral column and explain why these curves are present.

-The spinal column is behind organs and thus is off-center. Compensates for balance with regular curvatures in each region. The curves brings spine closer to trunk.

What is the best argument against intelligent design?

-The structure of our spine is a compromise that occasionally fails to meet the demands we place on it

mammalian ribs

-To increase mobility of spine, ribs were eliminated from all but the thoracic region and the other regions *cervical, lumbar, sacral, and caudal - became more specialized

Compare our thorax to that of a non-human ape.

-ape; human thorax nearly resembles great apes, except humans taper less at top a.k.a barrel-shaped. Apes is conical -ape ribcage wide at bottom because pelvis flares wide laterally. -human pelvis is relatively deeper to apes and more rounder

Humans have an additional arrangement that is not found in quadrupedal mammals. What is this?

-human spine further reinforced by LATERALLY POSITIONED LIGAMENTS between ribs and transverse processes

Compare our thorax to that of a monkey.

-monkey;deep and narrow thorax. limbs placed closer together and nearer the midline of the body. Scapula lies on lateral side of ribcage and moves easily with limb in parasigttal plane.

Immobilized by ribcage

12 Thoracic Vertebrae.

describe the Lumbar region of the spine

5 vertebrae with largest centra due to having larger proportion of body weight than other segment -its ribs are very short and fused onto vertebrae to contribute to transverse processes. -the vertebrae are wedge-shaped, creates lumbar lordosis and permits sacrum to form at 60degree angle with the long axis of the spine.The lordosis means that carrying a load creates bending stress in lumbar region and possibility of damage

Supports and balances head

7 Cervical Vertebrae.

describe the sacral region of the spine

A single bone created by the fusion of five vertebrae. Segmentation apparent in presence of five pairs of sacral spinal nerves. Number of segments in sacrum varies by species. 3 in apes, 5 in humans reflects increasing demands of bipedalism.

1. Which of the following is not part of the axial skeleton? A. skull. B. coxal bone. C. sacrum. D. thorax. E. vertebral column.

B. coxal bone

4. Which of the following is characterized by kyphosis? A. cervical region. B. thoracic region. C. lumbar region. D. coccyx. E. both A and C.

B. thoracic region

3. Which of the following is not a function of the vertebral column? A. anchors muscles of the back. B. protects the spinal cord. C. transmits nerve impulses to and from the brain. D. provides mobility of the trunk. E. supports weight against gravity.

C. transmits nerve impulses to and from the brain.

2. Which of the following is not the proper term for the bony part of the axial skeleton? A. vertebral column. B. spine. C. backbone. D. spinal cord. E. both B and D.'

D. spinal cord

T F The human vertebral curves are present in Australopithecus. However, the lumbar region is small and this suggests that Australopithecus was not adapted for habitual bipedalism.

TRUE

T F The vertebral column of Homo ergaster is consistent with the modern condition. However, the vertebral canal is narrower.

TRUE

The most mobile region of the vertebral column is A. cervical region. B. thoracic region. C. lumbar region. D. sacrum. E. coccyx.

a. cervical region

The human thorax is different than the cone-shaped thoraces of apes and is referred to as ____-shaped.

barrel

how many lumbar veterbrae do monkeys have?

between 3-4

We do not know why the tail was lost in our lineage, but it is gone by the time of the earliest apes that we have fossils for. It is speculated that the ape pattern of slow ____ in trees made the tail less adaptive

climbing

Humans have ___ wedge-shaped lumbar vertebrae. These are the largest vertebrae and bear the most weight.

five

The main part of the vertebral column that bears the weight above it is not the bone, but the ____________ that are made of cartilage that encloses fluid for more cushioning.

intervertebral-discs

_____ is a ventral curvature of the spine. The lumbar lordosis of the lower back is a unique characteristic of humans.

lordosis