Bones & Muscles!

36–1 The Skeletal System

The Skeleton

All organisms need structural support.

Unicellular organisms have a cytoskeleton.

Multicellular animals have either an exoskeleton (arthropods) or an endoskeleton (vertebrates).

The Skeleton

The human skeleton is composed of bone.

Bones and other connective tissues, such as cartilage and ligaments, form the skeletal system.

The Skeleton

The skeleton:

•supports the body.

•protects internal organs.

•provides for movement (with muscles).

•stores mineral reserves.

•provides a site for blood cell formation.

Axial Skeleton (blue)

Skull

Sternum

Ribs

Vertebral column

The axial skeleton supports the central axis of the body.

The Skeleton

Clavicle Scapula

Humerus

Radius Pelvis Ulna Carpals Metacarpals

Phalanges Femur

Patella Fibula

Tibia Tarsals Metatarsals

Phalanges

The Skeleton

Appendicular Skeleton (gray)

There are 206 bones in the adult human skeleton

Structure of Bones

Bones are a solid network of living cells and protein fibers that are surrounded by deposits of calcium salts.

Bone marrow

Periosteum

Spongy bone

Compact bone

Haversian canalCompact bone

Spongy bone

Periosteum

Osteocyte Artery

Vein

Structure of Bones

The bone is surrounded by a tough layer of connective tissue called the periosteum. Blood vessels in the periosteum carry oxygen and nutrients to the bone.

Structure of Bones

Bone marrow is a soft tissue inside the cavities within bones.

• Yellow marrow is made up of fat cells.

• Red marrow produces red blood cells, some kinds of white blood cells, and platelets.

The skeleton of an embryo is composed of cartilage, a strong connective tissue that supports the body and is softer and more flexible than bone.

Development of Bones

Development of Bones

Cartilage is replaced by bone during the process of bone formation called ossification.

Many long bones have growth plates at either end where growth of cartilage causes bones to lengthen.

By early adulthood, cartilage in the growth plates is replaced by bone, the bones become ossified, and growth stops.

Development of Bones

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Types of Joints

A place where one bone attaches to another bone is called a joint.

Joints permit bones to move without damaging each other.

Types of Joints

Depending on its type of movement, a joint is classified as immovable, slightly movable, or freely movable.

Types of Joints

Immovable joints, called fixed joints, allow no movement.

The bones are interlocked and held together by connective tissue, or they are fused together.

Places where bones in the skull meet are examples of immovable joints.

Types of Joints

Slightly movable joints permit a small amount of restricted movement.

Slightly movable joints are found in the joints between adjacent vertebrae.

Types of Joints

Freely movable joints permit movement in one or more directions.

Four common freely movable joints are:

•ball-and-socket joints

•hinge joints

•pivot joints

•saddle joints

Types of Joints

Ball-and-socket joints permit movement in many directions.

Active Art

Types of Joints

Hinge joints permit back-and-forth motion.

Types of Joints

Pivot joints allow one bone to rotate around another.

Types of Joints

Saddle joints permit one bone to slide in two directions.

Ball & socket - shoulder

hinge - knee

pivot - forearm saddle - wrist

Structure of Joints

In freely movable joints, cartilage covers the surfaces where two bones come together.

Joints are also surrounded by a fibrous capsule that holds the bones together while still allowing them to move.

Knee Joint

Structure of JointsMuscle

Tendon

Femur

Patella Bursa Ligament Synovial fluidCartilage

Fat

Fibula

Tibia

Structure of Joints

Connective tissue called ligaments hold bones together in joints.

Synovial fluid enables the bones to slide past each other more smoothly.

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Structure of Joints

In some freely movable joints small sacs of synovial fluid called bursae form.

A bursa reduces the friction between bones of a joint and also acts as a shock absorber.

Skeletal System Disorders

Excessive strain on a joint may produce inflammation, in which excess fluid causes swelling, pain, heat, and redness.

•Inflammation of a bursa is called bursitis.

•Inflammation of the joint itself is called arthritis.

Another skeletal system disorder is osteoporosis. Osteoporosis is caused by a loss of calcium in the bone.

36–2 The Muscular System

Muscles

The function of the muscular system is movement.

The average human body is over 40% muscle by mass.

Types of Muscle Tissue

There are three different types of muscle tissue:

skeletal

smooth

cardiac

Skeletal muscles:

•are usually attached to bones.

•are responsible for voluntary movements.

•have many nuclei.

•are sometimes called striated muscles.

Types of Muscle Tissue

Smooth muscles:

•are usually not under voluntary control.

•are spindle-shaped.

•have one nucleus.

•are not striated.

•are found in many internal organs and blood vessels.

Types of Muscle Tissue

Cardiac muscle:

•is only found in the heart.

•is striated.

•may have one or two nuclei.

Cardiac muscle cells are connected to each other by gap junctions.

Types of Muscle Tissue

Types of Muscle Tissue

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skeletal

cardiac

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Muscle Contraction

Skeletal muscle fibers are composed of myofibrils which are made of filaments that contain proteins called myosin and actin.

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Muscle Contraction

Skeletal muscle

Bundle of muscle fibers

Muscle fiber (cell)

Myofibril

Z line

Sarcomere

Myosin

Actin

Movie

Muscle Contraction

A muscle contracts when the thin actin filaments in the muscle fiber slide over the thick myosin filaments.

This process is called the sliding filament model of muscle contraction.

Control of Muscle Contraction

Impulses from motor neurons control the contraction of skeletal muscle fibers.

A neuromuscular junction is the point of contact between a motor neuron and a skeletal muscle cell.

How Muscles and Bones Interact

Skeletal muscles are joined to bones by tendons.

Tendons pull on the bones so they work like levers.

The joint functions as a fulcrum.

The muscles provide the force to move the lever.

Opposing Muscles Contract and Relax

How Muscles and Bones Interact

Opposing Muscles Contract and Relax

How Muscles and Bones Interact

A controlled movement requires contraction by both muscles.

How Muscles and Bones Interact

Exercise and Health

Regular exercise is important in maintaining muscular strength and flexibility.

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Exercise and Health

Aerobic exercises help the body’s systems to become more efficient.

Resistance exercises increase muscle size and strength.

36–3 The Integumentary System

The Integumentary System

The skin, hair, nails, and a variety of glands make up the integumentary system.

The skin is the largest organ in the body & its main function is to protect.

The integumentary system:

serves as a barrier against infection and injury.

helps to regulate body temperature.

removes waste products from the body.

provides protection against ultraviolet radiation from the sun.

The Integumentary System

The Skin

The skin is made up of two main layers—the epidermis (outer layer) and the dermis (inner layer).

Beneath the dermis is a layer of fat (hypodermis) and loose connective tissue that insulates the body.

The Skin

Structures of the Skin

Epidermis

Dermis

Hypodermis

Hair follicle

Sweat pore

Nerves

Muscle

Sweat gland

Fat

Sebaceous gland

Hair Blood vessels

The Skin

Epidermis 

The outer layer of the skin is the epidermis.

The epidermis has two layers.

•outer = dead cells.

•inner layer = living cells.

The Skin

Cells in the inner layer undergo rapid cell division, producing new cells that push older cells to the surface of the skin.

Older cells flatten and their organelles disintegrate.

Older cells also begin making keratin, a tough, fibrous protein.

When these cells die, they form a waterproof covering on the skin’s surface.

The Skin

The epidermis also contains melanocytes, which are cells that produce melanin, a dark brown pigment.

Melanin protects the skin from sun damage.

The Skin

Dermis 

The inner layer of the skin is the dermis.

The dermis contains collagen fibers, blood vessels, nerve endings, glands, sensory receptors, smooth muscles, and hair follicles.

The Skin

The dermis contains two major types of glands:

sweat glands

sebaceous, or oil, glands

The Skin

If your body gets too hot, sweat glands produce sweat.

When sweat evaporates, it cools the body.

Sweat also gets rid of wastes from the blood, along with water.

The Skin

Sebaceous glands produce an oily secretion called sebum.

Sebum spreads out along the surface of the skin and helps to keep the skin flexible and waterproof.

Hair and Nails

Hair 

Hair covers most body surfaces. Hair:

•protects the scalp from ultraviolet light from the sun.

•provides insulation from the cold.

•prevents dirt and other particles from entering the body.

Hair and Nails

Hair is produced by hair follicles, which are tubelike pockets of epidermal cells that extend into the dermis.

An individual hair is a column of cells that have filled with keratin and died.

The oily secretions of sebaceous glands help maintain the condition of each individual hair.

Hair and Nails

Nails 

Nails grow from rapidly dividing cells in the nail root.

The nail root is located near the tips of the fingers and toes.

During cell division, cells fill with keratin and produce a platelike nail that covers and protects the fingertips and toes.