LOCOMOTION & SUPPORT
Dr. M. Azzopardi
OVERVIEW
A)TYPES OF MUSCLESB) STRIATED MUSCLEC) HYDROSTATIC SKELETONS, EXOSKELETONS
AND ENDOSKELETONSD) THE VERTEBRAL COLUMN
Three kinds of muscle:
Smooth Unstriated,
Unstriped or Involuntary
Skeletal, Striated, Striped or Voluntary
Cardiac
Three kinds of muscle:
1. Smooth Musclecontracts slowly & fatigues slowly
2. Cardiac Muscleis self-stimulating &
does not fatigue
3. Skeletal Musclecontracts quickly &
fatigues quickly
Gap junctions
Cardiac muscle:is striated
cells: are smaller than skeletal have one nucleus
branch and interdigitate: can withstand tearing
Functions of the Intercalated discs:
1. add to the strength of cardiac muscle
2. provide strong mechanical adhesions between adjacent cells
3. have GAP JUNCTIONS allowing the rapid spread of a depolarisation initiated at one point in the heart
OVERVIEW
A) TYPES OF MUSCLES
B) STRIATED MUSCLEC) HYDROSTATIC SKELETONS,
EXOSKELETONS AND ENDOSKELETONS
D) THE VERTEBRAL COLUMN
Tendons attach skeletal muscle to bone:
Organisation of Skeletal Muscle1. Muscle 2. Muscle fibre bundles
3. Muscle fibre
4. Myofibril
5. Myofilaments
muscle cell
[groups of 10-100 or more muscle fibers]
contractile proteins: actin & myosin
composed of myofilaments
Organisation of Skeletal Muscle
Cells are multinucleate
Each muscle fibre is composed of MYOFIBRILS
Structure of a muscle fibre
Plasma membrane
Cytoplasm
Endoplasmic reticulum
Transverse tubule
Release calcium ions
Skeletal muscle is striated i.e. has visible banding
Striations = bands
Nuclei
Connective tissue separates cells
Myofibrils fill sarcoplasm
Nucleus
Striations Sarcolemma
Myofibril
Myofibrils:are bundles of myofilamentsseparated by sarcoplasmic reticulumcontractile organelles of skeletal muscle extend the entire length of a muscle fibre [6-25 cm
long]
Myofilaments :
MYOSIN – thick filaments
ACTIN – thin filaments
Sarcomere
Sarcomere: distance between two Z-lines
Sarcomeres are:
repeating units of equal length in a myofibril
the units of contraction
Sarcomeres are made of overlapping actin & myosin filaments
A band – dArk
I band - lIght
Thick and thin filaments overlap each other in a pattern that
creates striations.
Two bands in the SarcomereActin + myosin ActinActin
I band I bandA band
Z line Z lineH zone
SARCOMERE
Myosin
Actin
Region of overlap
Myosin cross-bridge
Learn to draw sarcomere structure
Syllabus says: M line, but some books call it M band
The structure of Skeletal Muscle
A bands - made of actin and myosinI bands - made solely of actin filaments
M line
A Sarcomere
How will a TS through the I band look like?
Proteins required for muscle contraction:
1. Actin2. Myosin3. Troponin4. Tropomyosin
Each actin filament is made up of:
two helical strands of globular actin molecules
(G-actin) which twist round each another
G-actin
F-actin
The whole assembly of actin molecules is called F-actin (fibrous actin).
Tropomyosin:- forms a fibrous strand around the actin
filament
Troponin : a globular protein vital to contraction of muscle fibre
one to bind:Troponin has three subunits:
1.Actin
2. Tropomyosin
3. Ca2+
Tropomyosin covers sites where actin binds to myosin
The Myosin molecule consists of two long polypeptide chains coiled together :
each chain ends in a globular head [cross bridge]
Tail
(a) A myosin molecule
The Myosin Heads have two sites:
myosin binds to actin, forming a
cross-bridge
binds &hydrolyses ATP
Actin-binding site
ATPase siteTropomysoin
Myosin head changes position
The Sliding Filament Theory of Muscle Contraction: actin slides past myosin
Skeletal Muscle Contraction
The Sliding Filament Theory of Muscle Contraction
• sarcomeres shorten and so myofibril shortens
• in turn, the muscle fibre shortens
What happens to the size of actin & myosin as they slide?
Do not change in length
What happens to the size of :
Shortens
Shortens
Remains the sameA band -
I band -
H zone -
Micrographs showing sarcomere contraction
The light (I) bands become shorter
Relaxedmuscle
Contractedmuscle
relaxed sarcomere
contracted sarcomere
The dark bands (A) bands stay the same length
The Sliding Filament Theory of Muscle Contraction
• Myosin cross-bridgespull on thin filaments.
• Thin filaments slide inward.
• Z lines come toward each other.
• Sarcomeres shorten. The muscle fiber shortens. The muscle shortens.
Figure 6.7
The Neuromuscular Junction
A Motor Unit is made up of:
all the fibres activated by a single motor neurone all the fibres contract simultaneously
Number of Motor Units involved varies
Ca2+ ions needed for contraction are released from:
Depolarisation travels along T-tubules
Closer look at T-Tubules
Sliding FilamentModel
Actin cross-bridges to myosin.
Actin slides past myosin in a short power stroke.
Cross-bridge is broken. Head is cocked.
Another cross-bridge forms.
Another power stroke slides actin closer to centre of sarcomere.
Details of Sliding Filament Theorystart
Remember that when:
Myosin binds ATP: cross-bridge is disconnected
ATP is hydrolysed: myosin head is
repositioned able to form another cross-
bridge
1 2
1
2
Cross-bridge formation occurs in the presence of………
Ca 2+
What happens if Ca2+ levels are:
High: Ca2+ binds to troponin tropomyosin is
displaced, allowing the formation of actin-myosin cross-bridges
Low:tropomyosin inhibits cross-bridge formation
How is the cross-bridge broken?
The myosin head binds a molecule of ATP, which causes it to release the actin
What happens in the absence of ATP?
This explains why muscles stiffen soon after animals die, a
condition known as
RIGOR MORTIS
the actin-myosin bonds cannot be broken
the muscles stiffen
Do the muscles remain stiff forever in a dead animal?
NO
Eventually the proteins begin to lose their integrity, and the muscles soften.
Dead !!
Question: [MAY, 2000]
This question concerns muscle.a) Distinguish between sarcomeres and
myofibrils. (2)Sarcomeres are the units of contraction. They lie between two Z-lines.Myofibrils are bundles of myofilaments made of actin and myosin.
Question: [MAY, 2000]
b) Briefly explain the role of actin and myosin in contraction of striated muscle. (4)When calcium ions bind to troponin, myosin-binding sites on actin filaments are exposed and myosin heads bind to actin, releasing ADP.The myosin head changes position and filaments slide past each other.ATP binds to myosin, causing it to release actin.Hydrolysis of ATP makes the myosin head return to original position.
Question: [MAY, 2000]
c) What role is played by the Z line (or Z disc) during the contraction of striated muscle fibres?Z-lines hold actin filaments together. Distance between Z–lines shortens on contraction. (2)
d)The presence of calcium ions is necessary for the
hydrolysis of ATP. How would removal of calcium ions from the muscle fibre sarcoplasm affect contraction? (2) Contraction stops. ATP is needed to break the cross-bridges between myosin and actin.
SummaryNAME FUNCTION
Actin filaments
Slide past myosin, causing contraction
Ca2+ Needed for myosin to bind to actin
Myosin filaments
Pull actin filaments by means of cross-bridges; are enzymatic and split ATP
ATP Supplies energy for muscle contraction
Energy Supply for Contraction:
Glucose: is usually the source of energy for muscle
contraction Phosphocreatine:
is a PHOSPHAGEN – a high energy phosphate compound which acts as a reservoir of phosphate-bond energy in the cell
Fig. 12 Glycogen stores in muscle
Question: [SEP, 2001] The figure is an electron micrograph of mammalian muscle tissue.a) What type of muscle tissue is shown in the figure? (1)
skeletal / voluntary / striated
b) What name is given to the region delimited by the horizontal arrows in the diagram? (1)Sarcomere
c) Briefly describe the structure of this region. (2)Lies between two Z-lines.Consists of alternating thin actin and thick myosin filaments.
d)Give a brief outline of the role of actin, myosin and ATP in the functioning of this type of muscle. (3)When calcium ions bind to troponin, myosin-binding sites on actin filaments are exposed and myosin heads bind to actin, releasing ADP.The myosin head changes position and filaments slide past each other.ATP binds to myosin, causing it to release actin.Hydrolysis of ATP makes the myosin head return to original position.
Question: [SEP, 2011] This question concerns skeletal muscle in the human body.a) What is muscle? (1)
A muscle is a contractile tissue of animals.
b) Briefly describe the gross structure of skeletal muscle. (2)Skeletal muscle is composed of bundles of muscle fibres. A muscle fibre is a muscle cell which is composed of myofibrils. Myofibrils are composed of myofilaments.
Question: [SEP, 2011]
c) Why is skeletal muscle striated? (3)The striations are bands seen under the microscope. There are dark and light bands which alternate. The bands consist of alternating thin actin and thick myosin filaments organised within the sarcomere.
Question: [SEP, 2011]
d) Draw a diagrammatic representation of a single sarcomere in the space below. (2)
Essay Titles
1.Write an account on ‘The role of proteins in animal locomotion’. [MAY, 2005]
2.Describe the fine structure of vertebrate
skeletal muscle and review the mechanism through which skeletal muscle contracts.[MAY, 2009]
OVERVIEW
A) TYPES OF MUSCLESB) STRIATED MUSCLE
C) HYDROSTATIC SKELETONS, EXOSKELETONS AND ENDOSKELETONS
D) THE VERTEBRAL COLUMN
Muscles can only contract and relax.
Without something rigid to pull against, a
muscle would just be a formless mass.
Skeletal systems provide rigid support against which muscles can pull, creating directed
movements.
Look at the flashes of red when the legs walk forward. These are the working muscles as they contract; the muscles in yellow are at rest
Three types of skeletons in animals:
1. Hydrostatic
2. Exoskeletons
3. Endoskeletons
Hydrostatic skeleton / hydroskeleton is ideal for:
Burrowing
A hydrostatic skeleton is :
a volume of fluid enclosed in a body cavity surrounded by muscle
chaetae
Circular muscle
Longitudinal muscleFluid-filled cavity
TS Earthworm
A hydrostatic skeleton is found:
primarily in soft-bodied invertebrates, both terrestrial and aquatic
EarthwormCnidarians
Hydrostatic skeleton:consists of internal fluids
(held under pressure in compartments surrounded by muscles)
this makes a soft-walled structure like an earthworm’s rigid so that muscles can act against it
since the liquid cannot escape, it forms a skeleton which cannot be compressed
What happens when the:
circular muscles in a segment contract:The compartment in that segment
elongates
longitudinal muscles of a segment contract: The compartment shortens and bulges
Alternating contractions of the circular & longitudinal muscles create waves of :
narrowing & widening; lengthening & shortening, that travel down the body
An earthworm uses its hydrostatic skeleton to crawl
Chaetae :
anchor earthworm while it pushes itself forwards
EXOSKELETONS
What is an ‘Exoskeleton’?A hardened outer surface to which muscles
attach
Exoskeletons occur in: molluscs, arthropods
An exoskeleton:protects all the soft tissues of the animal
BUT
is itself subject to damage by:
Around 50,000 Spider crabs invaded an Australian coast [2005]
Abrasion Crushing
What is the greatest drawback of the arthropod exoskeleton? Exoskeleton cannot grow
What must the animal do to become larger?
MOULT
Arthropods are the only non-vertebrate group to possess:
jointed appendages
Chitin:- the hard, composite
material that shields insects from harm - is light, strong
- can be both: hard (as in exoskeleton)
flexible (as in joints)
the levers on either side are operated by:
The Joints are hinges
Flexor musclesExtensor muscles
Contractions of the muscles cause:
jointed segments of the exoskeleton to move relative to each other
In which direction does the limb move when:
Flexor muscles contract:Towards the body
Extensor muscles contract:Away from the body
The hollow tubular form of the exoskeleton:
is very efficient for: support & locomotion
can support a much greater weight without giving way than a solid cylinder strut (like a bone) of the same mass
in small animals e.g. arthropods
bone
HOWEVER, the exoskeleton:loses this efficiency when organisms:
become greater their mass increases
Relate the following structures to their biological function, in view of locomotion and support: flexor and extensor muscles in insects; (2)Flexor muscles bend the limb on contracting while extensor muscles, extend the limb on contracting.
[MAY, 2013]
Endoskeleton
Dolphin
The Endoskeleton of vertebrates:is an internal scaffolding to which muscles
attach and against which they can pull
Functions of the mammalian endoskeleton:
1. provides a rigid framework that supports the body and protects the internal organs e.g. rib cage protects lungs and heart
2. important for locomotion – although muscle contractions provide the power, skeletal structures actually bring about movement
Functions of the mammalian endoskeleton:
3. in adults, the bone marrow produces blood cells and platelets – the red bone marrow produced red blood cells
Functions of the mammalian endoskeleton:
4. bone serves as a storage site for: calcium & phosphorus
– bone contains 90% of the phosphorus in the human body
Yellow bone marrow, dominated by fat cells, also stores energy reserves
Functions of the mammalian endoskeleton:
5. the skeleton participates in sensory transduction – three tiny bones in the middle ear transmit sound vibrations between the eardrum and the cochlea
[not in syllabus]
Cochlea [send impulses to brain]
Bipedal Gait
Bipedal Gaitbipedalism is a form of terrestrial locomotion
where an organism moves by means of its two rear limbs, or legs
Types of Bipedal movement include:
WalkingRunningHopping on two appendages
(typically legs)
Bipedal Gait is found in many animals:some of them:
Jesus lizard
habitually (e.g. birds and humans)
sporadically (e.g. some lizards)
Adjustment of the skeleton to allow bipedal gait:
1. The Skull alterations :
1. at the base of the cranium 2. of the head-neck alignment
result in a head which:
2. does not hang forward from an oblique spinal
column (as in apes)
1. is well balanced on an upright
column
Adjustment of the skeleton:
foramen magnum is the large hole at the base of the skull which allows passage of the spinal cord
A centrally located foramen magnum balances the head
in humans (fig. 18)
Adjustment of the skeleton:
2. The vertebral column: takes a:
forward bend in the lumbar (lower) region
a backward bend in the thoracic (upper) region
Together, the lumbar and thoracic curves bring the body's center of
gravity directly over the feet
Centre of gravity is:
over the hips and feet in humans
anterior to hip joint, in chimps, giving tendency
to fall forwards when standing bipedally
Adjustment of the skeleton:3. Hip when compared to quadripedal species, human hip
joints are: larger shorter, broader shape
Reason:to better support the greater amount of body weight passing through them
Adjustment of the skeleton:3. Hipa wider pelvis assists in upright muscle attachment
ChimpHuman
Long, narrow pelvis
Broad, short pelvis
Adjustment of the skeleton:
4. Kneehuman knee joints are enlarged:
to better support an increased amount of body weight
Adjustment of the skeleton:
5. Foot the human foot:
evolved to act as a platform to support the entire weight of the body
the big toe acts as a spring and aids in bipedal gait (fig. 23)
Adjustment of the skeleton:
arched feet provide shock absorption for pressure created by bearing all body’s weight on two feet (not four)
Foot print – 3.7 million years old
Human ancestors walked on two feet 3.2 million years ago
Adjustment of the skeleton:6. Limbslonger legs allow mass to be located in the
lower body
redistribution of body mass due to shift in centre of gravity. Humans more in legs, less in torso and arms.
An angled femur moves the centre of mass towards the middle of the body, promoting stability
Chimp Human
femur
Adjustment of the skeleton to allow bipedal gait:
1. Directly inferior foramen magnum2. S-curved spine3. Broad, bowl-shaped pelvis4. Knee with hip joint changes5. Ankle and foot modifications
Advantages of bipedalism:
Limited and exclusive bipedalism can offer a species several advantages:
1. the head is raised this allows a greater field of
vision with improved: detection of distant dangers or resources access to deeper water for wading animals allows the animals to reach higher food sources
with their mouths
Advantages of bipedalism:2. while upright, non-locomotory limbs become free
for other uses, including: manipulation (in primates and rodents) flight (in birds) digging (in the giant scaly ant eater) combat (in bears)
Ant eater
Advantages of bipedalism:3. upright posture allows the animal to expose less
body surface to the sun having less skin exposed to the sun decreases
the: impact of radiation need for cooling
Advantages of bipedalism:
4. humans walking on two legs consume only a quarter of the energy that chimpanzees use while “knuckle-walking” on all fours
Advantages of bipedalism:
early humans became bipedal: as a way to reduce energy costs
associated with moving about
the energy saved by walking upright: gave our ancient ancestors an
evolutionary advantage over other apes by reducing the costs of foraging for food
Disadvantages of bipedalism:
1. Slow speed 2. Strain placed on a body that was not intentionally designed to walk upright
Bolt [2012 Olympic champion] ran 200 m in 19.19 seconds, while a cheetah could
sprint that distance in 6.9 seconds.
Tissues composing the vertebrate skeleton:
consist primarily of three types: BoneCartilageLigaments
Bone & Cartilage are rigid tissues:
consist of living cells embedded in a matrix of collagen protein
Bone
Cartilage
The Structure of Bone
bone is the most rigid form of connective tissue
although bone resembles cartilage: the collagen fibres of bone are hardened by
deposits of calcium phosphate
The femur showing the location of spongy / cancellous and compact bone.
“shaft” of a bone
Vertical section through the femur showing the location of spongy and compact bone.
“shaft” of a bone
ends of a bone
hollow cavity filled with yellow
marrow
Membrane
Spongy and Compact bone
Compact bone is: dense strong provides an attachment site
for muscle
Spongy bone is: lightweight rich in blood vessels highly porous
Question: MAY, 2013
Relate the following structures to their biological function, in view of locomotion and support : spongy and compact bone in the femur. (2)Compact bone lines the surface of the femur, providing smooth surfaces where bones can articulate at joints. Also being dense, it provides support.Spongy bone is less dense than compact bone. As it is lighter, it makes locomotion easier as animal has less weight to carry.
Bone is well supplied with blood capillaries, unlike cartilage
Three types of bone cells:OSTEOBLASTSbone-building cells OSTEOCLASTS
bone-dissolving cells
OSTEOCYTES retired builders
Renovating bone
OSTEOBLAST
OSTEOCLAST
OSTEOCYTE in lacuna
Bone resorption
Bone formation
Osteoblasts secrete the organic matrix: calcium phosphate is later deposited
OSTEOCLASTS remove bone from
the internal surface of the diaphysis
OSTEOBLASTS add bone tissue to
the external surface of the diaphysis
Structure of Compact BoneHaversian System (Osteon): functional unit of compact bone
Bone Matrix :2/3 calcium phosphate- mineral salts make:bone rigid compression resistant BUT would be prone to
shattering
1/3 collagen proteins - collagen fibers add extra tensile strength
BUT- mostly add torsional flexibility to resist
shattering
Tensile Forces Torsional
ForcesCompressional
Forces
Question: [MAY, 2010]
Use your knowledge of biology to describe the significance of the following. (5 marks)
The development of collagen was an important step in the evolution of multicellular animals.
Question: [MAY, 2010]
Multicellular animals tend to be large. They need to be well supported.Endoskeletons are ideal for large organisms rather than hydrostatic or exoskeleton ones. Endoskeletons may be made of bone or cartilage and both contain collagen fibres in their matrix. Collagen adds extra tensile strength to the rigid calcium phosphate matrix. If matrix was made only of calcium phosphate it would be prone to shattering. Collagen adds torsional flexibility to the bone, preventing shattering.
Osteoporosis is characterised by low bone mass
Osteoporosis
Normal bone
Most Compact Bone is Composed of Haversian Systems
Haversian System
Haversian System (Osteon) is the:functional unit of compact bone
A Haversian System is made up: of concentric lamellae of the bone that surround a
Haversian canal
TS Compact Bone
Haversian canal (HC): contains blood vessels & nerves Concentric lamellae (CL): a thin plate of matrix Lacuna (L): a small space that contains an osteocyte
Canaliculi:fine channels radiating from each lacunacontain cytoplasm
Osteocytes
Live in lacunaeFound between layers (lamellae) of matrixConnected by cytoplasmic extensions through
canaliculiMaintain protein & mineral content of matrixHelp repair damaged boneQuickly differentiate into osteoblasts and are
activated if the bone needs structural changes
The endoskeleton can heal itselfCan this happen in the exoskeleton?
NO
What happens to osteocytes when a bone is fractured?
They differentiate into osteoblasts to lay the matrix .
Osteoblast(forms matrix of bone tissue) Osteocyte
(maintains matrix of bone tissue)
Question: [SEP, 2008]
The photomicrograph shows a section through a tissue from the human body.
1. What tissue is shown in Figure 2? (2) Skeletal /compact bone
2. What is the orientation of the section shown in the
figure ? (2) Transverse section
Question: [SEP, 2008]3. Draw an annotated map of the section shown in the
figure . (6)
SCALE: x 1
Annotated map of the bone section showing a Haversian system observed
under high power magnification
Question: [MAY, 2012]The photomicrograph in the figure shows part of the transverse section of a human compact bone.Use the space below to draw an annotated map of the compact bone shown in the figure. (8)
EXAMINERS’ COMMENTS:In most cases not all the structures in the diagram were labelled and annotated. A substantial number of students used a pen for labelling rather than a pencil, while a good number of candidates failed to include a title and a scale to the drawn diagram.
Question: [SEP, 2004]
Briefly describe how the following adaptations have increased the evolutionary success of the organisms that possess them. Your discussion should refer to the structures and functions related to each adaptation.
An endoskeleton versus a chitinous exoskeleton.
(5 marks)
Question: [SEP, 2004]
The endoskeleton of vertebrates is made of bone, which is a cellular, living tissue capable of growth, self-repair, and remodelling in response to physical stress. An exoskeleton made of chitin is not capable to carry out any of these functions.
Moulting is required if the animal is to grow, rendering it susceptible to infections and vulnerable to predators during the time when a new exoskeleton is being formed. These disadvantages are not associated with an endoskeleton.
The exoskeleton limits the size of the animal. The exoskeleton would have to become thicker and heavier in order to prevent collapse as the animal grows bigger. This would make movement difficult.
The skeleton facilitates movement by providing
a framework that muscles can move
Movement of the skeleton is accomplished by:
the action of pairs of ANTAGONISTIC MUSCLES: one muscle actively contracts, causing the other to be passively extended
Muscles move the skeleton around flexible JOINTS
What is a ‘JOINT’?– the point where two bones meet
Joint
What is the function of a joint?– joints hold bones together, giving stability, yet at
the same time, give the skeleton mobililty
bones act as levers that can be moved by the skeletal muscles to which they are attached
Not all joints are movablein those that move, the portion of each bone
that forms the joint is coated with a layer of cartilage
Immovable joints (sutures)
Function of cartilage at a joint:its smooth surface allows the bones surfaces
to slide past each other during movement
A synovial joint
[structure not required by
syllabus]
Where articulating bone ends are separated by a joint cavity and inside is synovial fluid
What is a ‘Synovial Joint’?
Painful joints when:
Ligaments & Tendons:on either side of a joint:
Tendons attach skeletal muscles to bones Ligaments attach the bones together
TENDON
LIGAMENTS
The Elbow
Hinge Joints – Synovial Joints occur at the elbows, knees
and finger joints are movable in only two
dimensions
allow movement in several directions
Ball & Socket Joints – Synovial Joints
Fig. 28 Antagonistic muscles of the forearm
Point of origin: the end of the muscle which is fixed to a relatively immovable bone
Point of insertion: the other end which is attached to
a mobile bone on the far side of the joint
Action of extensor & flexorBiceps: Flexor [bends arm on contraction]
Triceps: Extensor [extends arm on contraction]
Antagonistic muscles of the forearm
Which muscle is pulling on the bone?
BICEPSTRICEPS
OVERVIEW
A) TYPES OF MUSCLESB) STRIATED MUSCLEC) HYDROSTATIC SKELETONS,
EXOSKELETONS AND ENDOSKELETONS
D)THE VERTEBRAL COLUMN
The Vertebral Column consists of:
a series of vertebrae, separated by intervertebral discs made of cartilage
Intervertebral discs
Intervertebral disc acts as a shock absorber
Flexion (Bending Forward)
Extension (Bending Backward)
Vertebrae protect the Spinal cord
Spinal nerve
Spinal cord
Intervertebral disc may protrude & compress nerves
The Vertebral Column has an "S"-like curve :
when looking at it from the side this allows for an even
distribution of weight
the "S" curve helps a healthy spine withstand all kinds of stress
The vertebrae are held together by ligaments which:
– prevent their dislocation– permit a degree of movement so that the
vertebral column as a whole is flexible
24 Vertebrae make up the vertebral column
Lumbar vertebrae:
are subject to the greatest stress in terms of gravity and locomotion
must:1. provide rigidity for the body2. permit bending, sideways
movement and rotation of the trunk
Anterior (front) view of a typical mammalian vertebra
An articulating surface is one where two bones meet and movement between the
bones is possible
(articulating surface)
neural spine transverse process
neural arch
prezygapophysis
centrum neural canal
(a) Lumbar vertebra of a rabbit from left side.
(b) Anterior view of the third lumbar vertebra.
A Lumbar Vertebrum
centrum & neural arch are massive
centrum is quite short
this arrangement provides greater flexibility between
the lumbar vertebrae
centrum
neural arch
Why is the centrum flat?
Provides a platform where the intervertebral disc can be accommodated
centrum intervertebral disc
Lumbar VertebraeSpinal cord Centrum
Neural spine
Articular process
Transverse process- is long and wide- points forwards and
downwards
The large muscles of the back are attached to the lumbar vertebrae
Muscle
Label the lumbar vertebrum:
1. Neural spine2. Articular
process3. Transverse
process4. Neural canal5. Centrum
Question: [SEP, 2001]The diagram represents a transverse view of a lumbar vertebrum from a mammal. a) Identify the structures labelled A through D. (8)
A – neural spineB – neural canal C – centrum D – transverse process
b) What is the general function of the long projections arising from the vertebrum? (3)To provide a point of attachment for the large muscles of the back.
Question: [SEP, 2001]c) In what way is the three-dimensional shape of these
projections adapted to their function? (3)
To allow interlocking of adjacent vertebrae and thus provide rigidity.
d) Suggest a reason as to why structure C is particularly
large in lumbar vertebrae. (3)Provides support; resists stresses due to movement and gravity.
Question: [SEP, 2001]
e)Why is structure A particularly long in lumbar vertebrae when compared with most cervical vertebrae? (3)Structure A provides a large surface area for large muscle attachment as lumbar vertebrae need to support the upper half of the body, while cervical vertebrae just support the head.
Question: [SEP, 2001]
f) Draw a diagram showing a lumbar vertebrum as it would be expected to appear in longitudinal view. Use the space provided below for your drawing. (5)
Essay Titles
1. The various types of skeleton in the animal world are an adaptation to the modes of the life of the organisms that possess them. Discuss. [SEP, 2001]
2. Plants and animals solve problems associated with mechanical support in different ways. Discuss. [MAY, 2004]
3. Briefly compare the advantages and disadvantages of internal and external skeletons and describe how mechanical support is achieved by different groups in the animal kingdom.
[MAY 2006]
4. Outline the role of the exoskeleton of insects in movement and support. [SEP, 2011]
THE END
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