Organ systems overview
60 flashcards covering Organ systems overview for the MCAT Biology & Biochemistry section.
Organ systems are groups of organs and tissues that work together to perform essential functions in the human body. For example, the circulatory system transports blood and nutrients, while the respiratory system exchanges gases like oxygen and carbon dioxide. This overview covers the major systems—such as digestive, nervous, and immune—and their interconnections, helping you understand how the body maintains homeostasis and responds to changes. Mastering this topic is key to grasping overall human physiology.
On the MCAT, organ systems appear frequently in the Biology and Biochemistry section, often through multiple-choice questions that test your ability to identify functions, explain interactions, or analyze disorders. Common traps include confusing overlapping roles, like those of the endocrine and nervous systems, or overlooking how one system's failure affects others. Focus on memorizing key components, processes, and integrations to handle passage-based questions effectively.
A helpful tip: Use diagrams to visualize how systems interconnect.
Terms (60)
- 01
Organ system
A collection of organs and tissues that work together to perform a specific function necessary for the body's survival and homeostasis, such as the circulatory system transporting blood.
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Integumentary system
The body's outer covering, including skin, hair, and nails, which protects against environmental damage, regulates temperature, and houses sensory receptors.
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Epidermis
The outermost layer of the skin, composed of stratified squamous epithelium, that serves as a barrier against pathogens and prevents water loss.
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Dermis
The layer beneath the epidermis containing blood vessels, nerves, and glands, which provides structural support and facilitates nutrient delivery and sensation.
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Subcutaneous layer
The deepest skin layer, made of fat and connective tissue, that insulates the body, stores energy, and anchors the skin to underlying structures.
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Skeletal system
The framework of bones and cartilage that supports the body, protects organs, enables movement, and produces blood cells in the bone marrow.
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Axial skeleton
The central part of the skeletal system, including the skull, vertebral column, and rib cage, which protects the brain, spinal cord, and vital organs.
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Appendicular skeleton
The portion of the skeletal system consisting of the limbs and their attachments, such as the shoulder and pelvic girdles, which facilitates locomotion and manipulation.
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Bone classification
Bones are categorized as long, short, flat, irregular, or sesamoid based on shape and function, with long bones like the femur supporting weight and enabling movement.
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Muscular system
The network of muscles that produces movement, maintains posture, and generates heat through contraction, working in conjunction with the skeletal system.
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Skeletal muscle
Voluntary muscle attached to bones, composed of striated fibers, that contracts to produce body movements and is under conscious control.
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Smooth muscle
Involuntary muscle found in organs like the intestines, with non-striated fibers, that controls functions such as peristalsis and blood vessel constriction.
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Cardiac muscle
Specialized involuntary muscle in the heart, characterized by striations and intercalated discs, that pumps blood rhythmically throughout the body.
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Nervous system
The body's control center, consisting of the brain, spinal cord, and nerves, that coordinates responses to stimuli and regulates other systems via electrical signals.
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Central nervous system
The brain and spinal cord, which process information, integrate sensory input, and generate motor outputs to maintain homeostasis and behavior.
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Peripheral nervous system
The nerves outside the brain and spinal cord that connect the central nervous system to the rest of the body, transmitting signals for sensation and movement.
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Neurons
Specialized cells in the nervous system that transmit electrical impulses, consisting of a cell body, dendrites, and an axon, to communicate information rapidly.
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Neurotransmitters
Chemical messengers released by neurons at synapses to transmit signals across the gap to other neurons or cells, influencing functions like mood and muscle contraction.
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Endocrine system
A network of glands that produce and secrete hormones into the bloodstream to regulate processes such as metabolism, growth, and reproduction over time.
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Pituitary gland
A small gland at the base of the brain that secretes hormones controlling other endocrine glands and functions like growth and water balance.
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Thyroid gland
A gland in the neck that produces thyroid hormones to regulate metabolism, energy production, and body temperature by influencing cellular activity.
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Adrenal glands
Glands atop the kidneys that release hormones like cortisol and adrenaline, which manage stress responses, blood pressure, and metabolism.
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Hormones
Chemical signals produced by endocrine glands that travel through the blood to target organs, altering cellular activity to maintain homeostasis.
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Cardiovascular system
The heart, blood vessels, and blood that circulate oxygen, nutrients, and hormones while removing waste, ensuring delivery to all body tissues.
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Heart
A muscular organ that pumps blood through the body via rhythmic contractions, divided into four chambers to separate oxygenated and deoxygenated blood.
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Arteries
Blood vessels that carry blood away from the heart, typically under high pressure, and deliver oxygen and nutrients to tissues.
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Veins
Blood vessels that return blood to the heart, often with valves to prevent backflow, and transport deoxygenated blood and waste products.
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Capillaries
Tiny, thin-walled vessels where exchange of gases, nutrients, and waste occurs between blood and tissues due to their close proximity to cells.
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Blood
A fluid connective tissue that transports oxygen, nutrients, hormones, and immune cells while helping regulate pH and temperature.
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Lymphatic system
A network of vessels and organs that drains excess fluid, transports lymph, and houses immune cells to fight infections and maintain fluid balance.
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Lymph nodes
Small structures in the lymphatic system that filter lymph and contain immune cells, which activate to produce antibodies during infections.
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Spleen
An organ in the lymphatic system that filters blood, stores blood cells, and plays a role in immune responses by destroying old red blood cells.
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Thymus
A gland in the lymphatic system that produces T-cells, key immune cells, and is most active during childhood to establish immune function.
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Immune system
The body's defense mechanism, involving cells, tissues, and organs that protect against pathogens through innate and adaptive responses.
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Innate immunity
A non-specific defense system including skin, phagocytes, and inflammation that provides immediate protection against a wide range of pathogens.
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Adaptive immunity
A specific immune response involving lymphocytes that remembers and targets particular pathogens for a stronger, faster reaction upon re-exposure.
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Antibodies
Proteins produced by B-cells that bind to specific antigens on pathogens, marking them for destruction and neutralizing their effects.
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Respiratory system
The organs involved in gas exchange, including the lungs and airways, that take in oxygen and expel carbon dioxide to support cellular respiration.
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Lungs
Paired organs in the chest that facilitate oxygen uptake and carbon dioxide removal through alveoli, expanding and contracting via the diaphragm.
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Alveoli
Tiny air sacs in the lungs where gas exchange occurs, allowing oxygen to enter the blood and carbon dioxide to be exhaled.
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Diaphragm
A dome-shaped muscle below the lungs that contracts to expand the chest cavity, enabling inhalation, and relaxes for exhalation.
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Digestive system
The organs from mouth to anus that break down food, absorb nutrients, and eliminate waste, involving mechanical and chemical processes.
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Mouth
The entry point of the digestive system where mechanical digestion begins with teeth and chemical digestion starts with salivary enzymes.
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Stomach
A muscular organ that mixes food with acid and enzymes to break it down into chyme, beginning protein digestion and killing pathogens.
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Small intestine
The primary site for nutrient absorption, lined with villi and microvilli that increase surface area for efficient uptake of digested food.
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Large intestine
The final segment of the digestive tract that absorbs water and electrolytes, forms feces, and houses beneficial bacteria for fermentation.
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Liver
An organ that produces bile for fat digestion, detoxifies blood, and metabolizes nutrients, playing a central role in homeostasis.
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Urinary system
The kidneys, ureters, bladder, and urethra that filter blood, produce urine, and regulate fluid and electrolyte balance.
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Kidneys
Bean-shaped organs that filter waste from blood, regulate blood pressure via renin, and maintain pH and electrolyte levels.
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Nephron
The functional unit of the kidney, consisting of a glomerulus and tubules, that filters blood and reabsorbs essential substances while excreting waste.
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Bladder
A muscular sac that stores urine produced by the kidneys until it is expelled from the body.
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Ureters
Tubes that transport urine from the kidneys to the bladder, using peristaltic movements to prevent backflow.
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Reproductive system
The organs involved in producing gametes and facilitating fertilization, differing between males and females to ensure species continuation.
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Homeostasis
The process by which the body maintains a stable internal environment, such as temperature and pH, through coordinated organ system functions.
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Negative feedback
A regulatory mechanism where a change in a system triggers a response that reverses the change, like insulin lowering blood sugar levels.
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Positive feedback
A process that amplifies a change, such as oxytocin increasing uterine contractions during childbirth, to drive a response to completion.
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Interorgan communication
The coordination between organ systems via nerves and hormones to ensure integrated functions, like the nervous and endocrine systems regulating metabolism.
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Autonomic nervous system
The part of the nervous system that controls involuntary functions, such as heart rate and digestion, through sympathetic and parasympathetic divisions.
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Sympathetic nervous system
The 'fight or flight' branch of the autonomic nervous system that prepares the body for stress by increasing heart rate and redirecting blood flow.
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Parasympathetic nervous system
The 'rest and digest' branch that conserves energy by slowing heart rate and promoting digestive and restorative functions.