Structural Support and Movement

Chapter 36 Part 1

Impacts, IssuesPumping Up Muscles

Increasing muscle size and strength with drugs such as “andro” has unwanted side effects and can damage other organ systems

36.1 Invertebrate Skeletons

Hydrostatic skeleton• An enclosed fluid that contracting muscles act

upon (as in sea anemones, earthworms)

Exoskeleton• A hardened external skeleton found in some

mollusks and all arthropods

Endoskeleton • An internal skeleton, as in echinoderms

Hydrostatic Skeleton: Sea Anemone

Fig. 36-2a, p. 618

mouth

gastro-vascular cavity; the mouth can close and trap fluid inside this cavity

Animation: Hydrostatic skeleton

Hydrostatic Skeleton: Earthworm

Exoskeleton: Fly

Fig. 36-4, p. 619

longitudinal muscle contracts

longitudinal muscle relaxes

vertical muscle relaxes

vertical muscle contracts

A Wings pivot down as the relaxation of vertical muscle and the contraction of longitudinal muscle pulls in sides of thorax.

B Wings pivot up when the contraction of vertical muscle and relaxation of longitudinal muscle flattens the thorax.

thorax

Animation: Fly wing action

Exoskeleton: Spider

36.1 Key Concepts Invertebrate Skeletons

Contractile force exerted against a skeleton moves animal bodies

In many invertebrates a fluid-filled body cavity is a hydrostatic skeleton

Others have an exoskeleton of hard structures at the body surface

Still others have a hard internal skeleton, or endoskeleton

36.2 The Vertebrate Endoskeleton

All vertebrates have an endoskeleton• Usually consists primarily of bones• Supports the body, site of muscle attachment• Protects the spinal cord

The vertebral column (backbone) is made up of individual vertebrae separated by intervertebral disks made of cartilage

Axial and Appendicular Skeleton

Axial skeleton• Skull• Vertebral column• Ribs

Appendicular skeleton• Pectoral girdle• Pelvic girdle• Limbs

Skeletal Elements: Fish and Reptile

Fig. 36-7a, p. 620

vertebral column

pectoral girdle

pelvic girdle

Fig. 36-7b, p. 620

rib cage

vertebral column

skull bones

pelvic girdle

pectoral girdle

The Human Skeleton

Some features of the human skeleton are adaptations to upright posture and walking• Foramen magnum at the base of the skull allows

brain and spinal cord to connect• Vertebrae stacked one above the other in an S

curve

Bones of the Human Skeleton

Fig. 36-8, p. 621

A Skull bonesCRANIAL BONES

D Pectoral girdle and upper limb bones

FACIAL BONES

B Rib cage

CLAVICLE (collarbone)

SCAPULA (shoulder blade)STERNUM (breastbone) HUMERUS (upper arm bone)RIBS (twelve pairs)

RADIUS (forearm bone)C Vertebral column, or backbone CARPALS (wrist bones)

ULNA (forearm bone)

VERTEBRAE 12

4 35INTERVERTEBRAL

DISKSMETACARPALS (palm bones)

PHALANGES (thumb, finger bones)

E Pelvic girdle and lower limb bonesPELVIC GIRDLE (six fused bones)FEMUR (thighbone)

PATELLA (kneebone)

ligament bridginga knee joint, side view, midsection

TIBIA (lower leg bone)

FIBULA (lower leg bone)

TARSALS (ankle bones)METATARSALS (sole bones) PHALANGES (toe bones)

Animation: Human skeletal system

36.3 Bone Structure and Function

Bones have a variety of shapes and sizes• Long bones (arms and legs)• Flat bones (skull, ribs)• Short bones (carpals)

The human skeleton has 206 bones ranging from tiny ear bones to the massive femur

Bone Anatomy

Bones consist of three types of living cells in a secreted extracellular matrix• Osteoblasts build bones• Osteocytes are mature osteoblasts• Osteoclasts break down bone matrix

Bone cavities contain bone marrow• Red marrow in spongy bone forms blood cells• Yellow marrow in long bones is mostly fat

Bone Anatomy: Long Bone

Fig. 36-9a, p. 622

Fig. 36-9a, p. 622

space occupied by living bone cell

blood vessel

nutrient canal

location of yellow marrow

compact bone tissue

spongy bone tissue

55 µm

Fig. 36-9b, p. 622

Fig. 36-9b, p. 622

spongy bone tissue

compact bone tissue

outer layer of dense

connective tissueblood vessel

Animation: Structure of a femur

Bone Functions

Bone Formation and Remodeling

The embryonic skeleton consists of cartilage which is modeled into bone, grows until early adulthood, and is constantly remodeled

Bones and teeth store the body’s calcium• Calcitonin slows release of calcium from bones• Parathyroid hormone releases bone calcium • Sex hormones encourage bone building• Cortisol slows bone building

Long Bone Formation

Fig. 36-10, p. 623

Embryo: cartilage model of bone forms

Fetus: blood vessel invades model; osteoblasts start producing bone tissue; marrow cavity forms

Newborn: remodeling and growth continue; secondary bone-forming centers appear at knobby ends of bone

Adult: mature bone

About Osteoporosis

Osteoporosis (“porous bones”)• When more calcium is removed from bone than is

deposited, bone become brittle and break easily

Proper diet and exercise help keep bones healthy

Osteoporosis

36.4 Skeletal Joints—Where Bones Meet

Joint• Area of contact or near contact between bones

Three types of joints• Fibrous joints (teeth sockets): no movement• Cartilaginous joints (vertebrae): little movement• Synovial joints (knee): much movement

Synovial Joints

In synovial joints, bones are separated by a fluid-filled cavity, padded with cartilage, and held together by dense connective tissue (ligaments)

Different synovial joints have different movements• Ball-and-socket joints (shoulder)• Gliding joints (wrist and ankles)• Hinged joints (elbows and knees)

Three Types of Joints

Three Types of Joints

Fig. 36-12a, p. 624

fibrous joint attaches tooth to jawbone

synovial joint (ball and socket) between humerus and scapula

cartilaginous joint between rib and sternum

cartilaginous joint between adjacent vertebraesynovial joint (hinge type) between humerus and radius

synovial joint (ball and socket) between pelvic girdle and femur

Fig. 36-12b, p. 624

femur

patella

cartilage

ligaments

menisci

tibia

fibula

36.5 Those Aching Joints

We ask a lot of our joints when we engage in sports, carry out repetitive tasks, or strap on a pair of high heels

Joint Injuries and Diseases

Common joint injuries• Sprained ankle; torn cruciate ligaments in knee;

torn meniscus in knee; dislocations

Arthritis (chronic inflammation)• Osteoarthritis; rheumatoid arthritis; gout

Bursitis (inflammation of a bursa)

36.2-36.5 Key Concepts Vertebrate Skeletons

Vertebrates have an endoskeleton of cartilage, bone, or both

Bones interact with muscles to move the body; they also protect and support organs, and store minerals

Blood cells form in some bones

A joint is a place where bones meet; there are several kinds

36.6 Skeletal–Muscular Systems

Muscle fibers• Long, cylindrical cells with multiple nuclei that

hold contractile filaments

Tendons attach skeletal muscle to bone• Muscle contraction transmits force to bone and

makes it move

Muscles and bones interact as a lever system • Many skeletal muscles work in opposing pairs

Skeletal–Muscular Action

Fig. 36-14, p. 626

C The first muscle group in the upper hindlimb contracts again and draws it back toward body.

B An opposing muscle group attached to the limb forcefully contracts and pulls it back. The contractile force, applied against the rock, now propels the frog forward.

A A muscle attached to each upper hindlimb contracts and pulls it slightly forward relative to main body axis.

Opposing Muscle Groups

Fig. 36-15, p. 626

Triceps contracts, pulls the forelimb down.

Triceps relaxes.

Biceps contracts at the same time, and pulls forelimb up.

At the same time, biceps relaxes.

A When the triceps relaxes and its opposing partner (biceps) contracts, the elbow joint flexes and the forearm is pulled upward.

B When the triceps contracts and the biceps relaxes, the forearm is extended downward.

Animation: Opposing muscle action

Muscles and Tendons

Muscles and Tendons

Fig. 36-16a, p. 627

TRICEPS BRACHIIStraightens the forearm at elbow

BICEPS BRACHIIBends the forearm at the elbow

PECTORALIS MAJORDraws the arm forward and in toward the body

DELTOIDRaises the armSERRATUS ANTERIOR

Draws shoulder blade forward, helps raise arm, assists in pushes

TRAPEZIUSLifts the shoulder blade, braces the shoulder, draws the head backEXTERNAL OBLIQUE

Compresses the abdomen, assists in lateral rotation of the torso

LATISSIMUS DORSIRotates and draws the arm backward and toward the bodyRECTUS ABDOMINIS

Depresses the thoracic (chest) cavity, compresses the abdomen, bends the backbone

GLUTEUS MAXIMUS

ADDUCTOR LONGUS

Extends and rotates the thigh outward when walking, running, and climbingFlexes, laterally rotates,

and draws the thighs toward the bodySARTORIUS

BICEPS FEMORIS

Bends the thigh at the hip, bends lower leg at the knee, rotates the thigh in an outward direction

(Hamstring muscle) Draws thigh backward, bends the knee

QUADRICEPS FEMORISSet of four muscles that flex the thigh at the hip, extend the leg at knee

GASTROCNEMIUS

TIBIALIS ANTERIOR

Bends the lower leg at the knee when walking, extends the foot when jumping

Flexes the foot toward the shin

Achilles tendon

Fig. 36-16b, p. 627

muscle

tendon

bursae

synovial cavity

Animation: Human skeletal muscles

36.6 Key Concepts The Muscle–Bone Partnership

Skeletal muscles are bundles of muscle fibers that interact with bones and with one another

Some cause movements by working as pairs or groups; others oppose or reverse the action of a partner muscle

Tendons attach skeletal muscles to bones

Animation: Long bone formation

Animation: Vertebrate skeletons