Unit 5: Body Systems and Levels of Organization

Multicellular Organisms

Organisms composed of trillions of cells.

Cell Differentiation

Process where cells specialize for functions.

Levels of Organization

Cells → Tissues → Organs → Organ Systems → Organisms.

Tissue

Groups of similar cells performing specific tasks.

Types of Human Tissue

Four main types: muscle, connective, epithelial, nervous.

Muscle Tissue

Causes movement in the body.

Connective Tissue

Provides structure and support to organs.

Epithelial Tissue

Lines organs and forms outer skin layer.

Nervous Tissue

Carries messages to and from the brain.

Dermal Tissue

Outer covering of plants preventing water loss.

Ground Tissue

Provides storage and support in plants.

Vascular Tissue

Transports water and nutrients in plants.

Organs

Groups of tissues working together for specific jobs.

Examples of Organs

Lungs, liver, heart, brain, stomach.

Organ Systems

Groups of organs completing series of tasks.

Muscular System

Enables movement and maintains body temperature.

Skeletal Muscle

Voluntary muscle attached to bones.

Smooth Muscle

Involuntary muscle lining blood vessels and organs.

Muscle Contraction

Cells shorten to enable movement.

Muscle Relaxation

Cells return to original length after contraction.

Function of Muscles

Movement, protection, stability, temperature maintenance.

Tissue Function in Stomach

Different tissues work together for digestion.

Cardiac muscles

Involuntary muscles found only in the heart.

Muscular system

System of muscles enabling body movement.

Skeletal system

Composed of over 200 bones supporting the body.

Joints

Where two or more bones meet, allowing movement.

Ligaments

Tissues connecting bones at joints for stability.

Tendons

Tissues connecting muscles to bones for movement.

Hydrostatic skeleton

Fluid-filled cavity surrounded by muscle tissue.

Exoskeletons

Hard outer coverings protecting animal bodies.

Calorie (Cal)

Energy to raise 1 kg water by 1°C.

Nutrients

Food components necessary for growth and survival.

Esophagus

Muscular tube connecting mouth to stomach.

Peristalsis

Waves of muscle contractions moving food through digestive tract.

Mechanical digestion

Physical breakdown of food into smaller pieces.

Chemical digestion

Chemical reactions breaking food into molecules.

Ingestion

Process of taking food into the mouth.

Saliva

Fluid containing enzymes aiding in food breakdown.

Stomach

Hollow organ storing food, holding about 2 L.

Muscle contractions

Actions enabling movement by shortening muscles.

Skeletal functions

Support, protection, and material storage for the body.

Coelom

Fluid-filled cavity in organisms with hydrostatic skeletons.

Bones

Rigid structures forming the skeleton, aiding movement.

Flexibility

Ability of joints to allow movement.

Stomach capacity

Adult stomach holds about 2 L of contents.

Chemical digestion

Process of breaking down food chemically.

Stomach folds

Folds allow stomach to expand for food storage.

Gastric juice

Acidic fluid aiding in food breakdown.

Pepsin

Enzyme breaking proteins into amino acids.

Peristalsis

Muscle contractions moving food through digestive tract.

Small intestine length

Approximately 7 m (23 ft) long.

Small intestine diameter

Diameter of about 2.5 cm (1 in).

Villi

Fingerlike projections increasing nutrient absorption area.

Nutrient absorption

Nutrients enter blood through villi's blood vessels.

Large intestine length

About 1.5 m (5 ft) long.

Large intestine diameter

Diameter of about 5 cm (2 in).

Water absorption

Large intestine absorbs additional water from waste.

Rectum function

Stores semisolid waste before excretion.

Excretory system

Eliminates wastes and regulates body fluid levels.

Urinary system

Processes and removes liquid waste (urine).

Kidneys

Filter waste from blood, bean-shaped organs.

Ureters

Tubes draining urine from kidneys to bladder.

Bladder

Sac that stores urine before excretion.

Urethra

Tube excreting urine from the body.

Respiratory system

Exchanges gases between body and environment.

Pharynx

Passageway for air, food, and liquids.

Pharynx

Connects mouth to trachea for air passage.

Trachea

Windpipe; tube connecting pharynx to bronchi.

Bronchi

Two tubes leading from trachea to lungs.

Bronchioles

Smaller tubes branching from bronchi in lungs.

Alveoli

Microscopic sacs for gas exchange in lungs.

Diaphragm

Muscle that changes chest air pressure.

Gas Exchange

Oxygen enters blood; CO2 exits alveoli.

Circulatory System

Transports blood, nutrients, gases, and wastes.

Heart

Muscle that pumps blood throughout the body.

Atria

Upper heart chambers receiving blood.

Ventricles

Lower heart chambers pumping blood out.

Arteries

Carry oxygen-rich blood away from heart.

Veins

Transport carbon dioxide-rich blood to heart.

Capillaries

Tiny vessels for nutrient and gas exchange.

Pulmonary Artery

Carries carbon dioxide-rich blood to lungs.

Pulmonary Vein

Carries oxygen-rich blood from lungs to heart.

Open Circulatory System

Blood flows into open spaces around organs.

Closed Circulatory System

Blood moves through vessels; faster transport.

Heart Chambers

Four sections: two atria and two ventricles.

Blood Pressure

Higher in arteries; lower in veins.

Oxygen Transport

Essential for cellular respiration in organisms.

Nutrient Transport

Blood carries essential nutrients to cells.

Nervous System

Gathers, processes, and responds to information.

Neurons

Basic functioning units of the nervous system.

Sense Receptors

Detect changes in the environment.

Brain

Control center that processes information.

Response

Action sent out by the brain after processing.

Memory Storage

Brain retains some processed information.

Response Time

Nervous system reacts in less than one second.

Signal Speed

Signals can travel up to 400 km/h.

Central Nervous System (CNS)

Includes brain and spinal cord.

Peripheral Nervous System (PNS)

Transmits information between CNS and body.

Somatic System

Controls voluntary movements and skeletal muscles.

Autonomic System

Regulates involuntary actions and smooth muscles.