MOVEMENT AND SUPPORTs

Protection

The external covering of an animal that primarily protects against mechanical injury and invasion by microorganisms.

Integument

The external covering of an animal.

Protozoa

Single-celled eukaryotes that feed on organic matter and may have a plasma membrane or a thick protein coat called pellicle.

Epidermis

The outer layer of the integument consisting of a single layer of columnar epithelial tissues.

Cuticles

Structures consisting of chitin and proteins in rigid plates that vary in structure among invertebrates.

Molting

The process of shedding the old skin or outer cuticle in invertebrates.

Cnidarians

Aquatic organisms with tentacles and stinging cells called nematocysts.

Nematodes

Very small, slender worms with an epidermis that is one cell thick.

Annelids

Segmented worms with an epidermis that is one cell thick.

Echinoderms

Marine animals characterized by a hard, spiny covering or skin.

Arthropods

Invertebrates with the most complex integuments, including chelicerates, crustaceans, hexapoda, and myriapoda.

Exoskeleton

The external skeleton that supports and protects an animal's body.

Skin

The vertebrate integument, consisting of the epidermis, dermis, and hypodermis/subcutaneous tissue.

Lampreys and Hagfishes

Jawless fishes with relatively thick skin and protective mucous secretion.

Cartilaginous Fishes

Fishes with multilayered skin containing mucous, sensory cells, and placoid scales called denticles.

Bony Fishes

Fishes with scales composed of dermal bone and a permeable skin for gas exchange.

Amphibians

Vertebrates with a stratified epidermis, dermis containing mucous and serous glands, and transitional characteristics between aquatic and terrestrial environments.

Nonavian Reptiles

Reptiles with a thick, keratinized outer layer of the epidermis, modified scales, scutes, beaks, rattles, and claws.

Avian Reptiles

Birds with thin epidermis, keratinized feathers, and a uropygial gland.

Mammals

Vertebrates with notable features of mammalian skin, including hair, glands, highly stratified epidermis, and a thick dermis.

Epidermis

The outermost layer of mammalian skin, composed of stratified squamous epithelium and consisting of various types of cells.

Keratinized

Referring to cells that have become hardened and contain the protein keratin, making up the outer layer of the skin.

Dermis

The thickest portion of mammalian skin, containing blood vessels, lymphatic vessels, nerve endings, hair follicles, sensory receptors, small muscles, and glands.

Hypodermis

The layer of loose connective tissue, adipose tissue, and skeletal muscles underneath the dermis.

Sudoriferous glands

Also known as sweat glands, these glands are distributed over most of the human body surface and secrete sweat through perspiration.

Sebaceous glands

Glands connected to hair follicles in the dermis that secrete sebum, a skin-softening agent and protective agent against microorganisms.

Melanin

Pigments within the cells of the epidermal layer and in hair that contribute to mammalian skin color.

Hair follicle

An invagination of the epidermis that extends deep into the dermis and is the site where hair arises.

Arrector pili muscle

A smooth muscle that attaches to the connective-tissue sheath of a hair follicle and can contract, causing the hair to become perpendicular to the skin's surface.

Nails

Flat, horny plates on the dorsal surface of the distal segments of the digits, modified from the epidermis.

Hydrostatic skeleton

A core of liquid surrounded by a tension-resistant sheath of longitudinal and circular muscles, found in invertebrates.

Exoskeleton

A rigid outer covering that provides support and protection to the body, found in arthropods.

Endoskeleton

A skeletal system enclosed within the body tissues, consisting of cartilage and bone, found in vertebrates.

Cartilage

A specialized type of connective tissue that provides a site for muscle attachment and aids in movement at joints.

Bone

A specialized connective tissue that provides attachment for muscles, transmits the force of muscular contraction, supports internal organs, and stores calcium and phosphate.

Tetrapod

A vertebrate animal with four limbs, such as amphibians, reptiles, birds, and mammals.

Amphibians

Cold-blooded vertebrates that live part of their lives in water and part on land, such as frogs and salamanders.

Invertebral disks

Structures in the vertebral column that help hold it together, absorb shock, and provide joint mobility.

Cartilage

A flexible connective tissue that is replaced by bone in the ribs of tetrapods.

Connective tissue

Tissue that connects different parts of the body, such as ligaments and tendons.

Axial skeleton

The central part of the skeleton, including the skull, vertebral column, sternum, and ribs.

Appendicular skeleton

The bones of the limbs and their attachments to the axial skeleton.

Pectoral girdles

The bones that connect the upper limbs to the axial skeleton, such as the shoulder blades.

Pelvic girdle

The bones that connect the lower limbs to the axial skeleton, such as the hip bones.

Non-muscular movement

Movement that does not involve muscles, such as movement of cells and protists.

Cytoskeleton

A network of protein filaments within a cell that provides structural support and allows for movement.

Pseudopodia

Temporary extensions of the cell membrane used for movement in certain cells, such as amoebas.

Cilia

Hair-like structures on the surface of cells that beat in coordinated waves to create movement.

Flagella

Long, whip-like structures on the surface of cells that propel the cell forward.

Actin and myosin

Contractile proteins involved in muscle contraction in animals.

Amoeboid movement

Movement observed in amoebas, which involves the extension and retraction of pseudopodia.

Ciliary movement

Coordinated waves of cilia passing along rows, allowing for movement.

Flagellar movement

Movement created by the whipping motion of flagella.

Muscular tissue

Tissue responsible for movement in animals, characterized by its contractility.

Excitability

The ability of muscle tissue to receive and respond to a stimulus.

Extensibility

The ability of muscle tissue to be stretched.

Elasticity

The ability of muscle tissue to return to its original shape after being stretched or contracted.

Muscle fibers

The contractile cells of muscle tissue.

Smooth muscle

Involuntary muscle with spindle-shaped fibers arranged in a parallel pattern.

Cardiac muscle

Involuntary muscle with striated fibers that are branched and interlock for greater strength.

Skeletal muscle

Voluntary muscle with multinucleated, striated fibers that attach to skeletons.

Antagonistic pairs

Pairs of muscles that work together to bend and straighten joints.

Locomotion

Movement from one place to another.

Pedal locomotion

Locomotion achieved by the movement of the foot or feet.

Sarcomere

The functional unit of a myofibril, extending from one Z line to another Z line.

Actin and myosin

Muscle proteins involved in the sliding-filament model of muscle contraction.

Sliding-filament model of muscle contraction

The movement of actin filaments in relation to myosin filaments during muscle contraction.

Motor unit

A motor nerve fiber and all the muscle fibers it communicates with.

Neuromuscular junction

The chemical synapse between a motor neuron and a muscle fiber.

Calcium ions

Ions that play a crucial role in the process of muscle contraction.