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