Human Body Systems

Vocabulary practice cards focusing on human body systems, anatomical structures, physiological processes, and homeostatic interactions for 7th grade Life Science.

Endocrine System

The body system that produces chemicals (hormones) in glands that release directly into the bloodstream (circulatory system) and works with other systems those hormones influence.

Negative Feedback

A control mechanism in which hormone levels in the blood reaching a certain threshold signals the body to stop releasing that hormone, operating similarly to a thermostat.

Immune System

A defense network made up of several organ systems working together to protect the body against disease-causing pathogens.

Pathogen

Any biological agent that can cause disease, specifically bacteria or viruses.

Lymphatic System

A drainage and filtering system that acts as the body's clean-up crew by returning excess interstitial fluid to the circulatory system and filtering pathogens.

Lymph

The fluid carried by the lymphatic system, composed of water, white blood cells ($\text{WBCs}$), dissolved glucose, and other materials.

Lymph Nodes

Knobs of specialized tissue located along lymphatic vessels that filter lymph by trapping bacteria and other pathogens.

Integumentary System

The organ system consisting of the skin, hair, and nails that acts as an external barrier, regulates body temperature (via sweating and shivering), gathers sensory information, and synthesizes Vitamin D.

Respiratory System

The system responsible for taking in oxygen from inhaled air to deliver to blood cells and expelling carbon dioxide ($\text{CO}_2$) and water ($\text{H}_2\text{O}$) waste upon exhalation.

Trachea (Windpipe)

The airway passage that directs inhaled air from the mouth and nose down toward the lungs.

Diaphragm

A sheet of internal skeletal muscle separating the chest cavity from the abdomen that contracts and relaxes to expand and deflate the lungs for breathing.

Alveoli

Tiny microscopic air sacs within the lungs surrounded by capillaries where the exchange of oxygen and carbon dioxide gases occurs.

Circulatory System

The internal transport network consisting of the heart, blood vessels, and blood that delivers oxygen and nutrients to tissues while removing cellular metabolic wastes.

Heart

A central muscular organ consisting of four hollow chambers that rhythmically contracts to pump blood throughout the body.

Arteries

Thick-walled blood vessels (traditionally diagrammed in red) that carry oxygenated blood away from the heart to bodily tissues.

Veins

Blood vessels (traditionally diagrammed in blue) that carry deoxygenated blood from the tissues back toward the heart.

Capillaries

Extremely small, one-cell-thick blood vessels connecting arteries and veins where the exchange of nutrients, gases ($\text{O}_2$ and $\text{CO}_2$), and wastes takes place.

Plasma

The pale yellowish liquid matrix component of blood in which cellular components and dissolved substances are suspended.

Red Blood Cells

Cells in the bloodstream specialized to bind oxygen in the lungs and distribute it to all working body cells.

White Blood Cells

Immune system cells circulating in the blood that identify and destroy infectious pathogens and foreign particles.

Platelets

Small cellular fragments present in blood that adhere together to initiate blood clotting and scab formation upon injury.

Involuntary Muscle

A class of muscle tissue not subjected to conscious, voluntary regulation, such as those controlling peristalsis, cardiac beating, and respiratory motions.

Voluntary Muscle

A class of muscle tissue that can be consciously controlled by motor neural signals, such as muscles used for smiling, writing, or walking.

Skeletal Muscle

Striated, voluntary muscle tissue attached to bones that contracts to produce skeletal motion.

Smooth Muscle

Non-striated, involuntary muscle tissue found lining hollow internal visceral organs that contracts to move substances such as food through the digestive tract.

Cardiac Muscle

Involuntary, specialized striated muscle tissue found exclusively within the heart wall that pumps blood continuously.

Skeletal System

The rigid structural framework of bones and cartilage that protects vital internal organs, anchors muscles, stores minerals (calcium), and produces blood cells.

Red Marrow

Soft vascular tissue located within internal cavities of bones that continuously generates red blood cells, white blood cells, and platelets.

Yellow Marrow

Fatty connective tissue located within internal marrow cavities of long bones that functions primarily as an energy reserve.

Cartilage

A smooth, resilient connective tissue lining joint articulations that reduces friction and cushions bones by absorbing compressive mechanical shocks.

Tendon

A tough fibrous connective tissue band that connects skeletal muscle securely to bone.

Ligament

A strong, flexible band of fibrous connective tissue that binds bone to bone across a joint.

Neuron

A specialized electrically excitable nerve cell consisting of a cell body, dendrites, and an axon that receives, processes, and transmits electrical impulses.

Central Nervous System

The primary division of the nervous system consisting of the brain and spinal cord that coordinates bodily functions and processes data.

Peripheral Nervous System

The network of motor and sensory nerves extending outside the central brain and spinal cord throughout the rest of the body.

Sensory Nerves

Nerves collecting input from sensory organs (representing the five senses) that transmit environmental stimulus data inward to the central nervous system.

Motor Nerves

Nerves carrying directional output impulses from the central nervous system out to muscles to elicit physical contractions and motion.

Stimulus

Any detectable change or signal occurring in an organism's external or internal environment that elicits a physiological response.

Digestive System

The organ system that ingests, breaks down food into smaller nutrient molecules, absorbs them into the circulatory system, and expels indigestible solid waste.

Mechanical Digestion

The physical breakdown of large food pieces into smaller particles without chemical alteration, achieved through actions such as chewing and involuntary muscular peristalsis.

Chemical Digestion

The enzymatic and acidic breakdown of complex food polymers into smaller nutrient molecules, utilizing saliva, stomach gastric juices, pancreatic enzymes, and liver bile.

Esophagus

A muscular tube that conducts swallowed food from the pharynx down to the stomach via rhythmic peristaltic contractions.

Stomach

An expandable muscular digestive pouch that churns food mechanically and digests it chemically using strong gastric juices and digestive acids.

Small Intestine

The long digestive segment lined with finger-like villi where the majority of chemical digestion concludes and nutrients are absorbed into the bloodstream.

Large Intestine (Colon)

The wide terminal portion of the digestive tract that recovers and reabsorbs water back into the blood, compacting remaining waste into solid feces.

Liver

A major accessory digestive gland that produces bile, a digestive chemical specialized for emulsifying and breaking down dietary fats (lipids).

Gallbladder

A small reservoir organ located beneath the liver that concentrates and stores bile before discharging it into the small intestine.

Pancreas

An accessory organ with dual functions that secretes digestive enzyme juice into the small intestine and synthesizes regulatory hormones such as insulin.

Kidney

The primary bean-shaped excretory organ composed of filtering units called nephrons that filter wastes and excess water from blood to produce urine.

Fertilization

The biological process in which a haploid male sperm cell ($n$) combines with a haploid female egg cell ($n$) to form a new diploid ($2n$) zygote.