AP Biology Notes: Other Organ Systems

Five Things to Know about Other Organ Systems

  1. Lungs are the primary structures for respiration in mammals. The circulatory system connects the lungs and the cells around an organism’s body. All mammalian lungs end in blind sacs called alveoli, which are surrounded by a dense net of capillaries into which oxygen diffuses and from which carbon dioxide is excreted.
  2. Blood pressure is the force per area that blood exerts on the walls of blood vessels and is expressed as a systolic number over a diastolic number. Blood pressure drops as blood moves farther away from the heart because the distance from the pump has increased and because of the muscular construction of arteries versus veins.
  3. Mechanical digestion is the physical breakdown of food, by chewing in the mouth and churning in the stomach. Chemical digestion starts in the mouth with the break-down of carbohydrates and continues through the stomach and small intestine. Nutrients, water, and minerals are absorbed into the body in the colon.
  4. Excretion is the removal of metabolic wastes, and all metabolic processes lead to the production of mineral salts that must be excreted.
  5. Kidneys regulate the concentration of water, ions, and other dissolved substances in the blood through the formation and excretion of urine.

Key Topics–Other Organ Systems

Remember that the AP Biology exam tests you on the depth of your knowledge, not just your ability to recall facts. While we have provided brief definitions here, you will need to know these terms in even more depth for the AP Biology exam.

Respiratory and Circulatory Systems

  • Organ: A group of tissues that perform a specific function in the body
  • Gas exchange: The exchange of gases, such as oxygen and carbon dioxide, through respiratory surfaces, gills, lungs, or tracheae
  • Lungs: Saclike respiratory organs of most vertebrates
  • Circulatory system: System that circulates blood throughout the body; includes the heart, blood, and blood vessels
  • Lumen: The inner cavity of a tubular organ, such as an intestine
  • Hemoglobin (Hb): The protein found in red blood cells that carries oxygen
  • Myoglobin (Mb): An iron- and oxygen-binding protein found in muscle tissue

Digestive and Excretory Systems

  • Digestion: The process of breaking down large organic molecules into smaller ones
  • Absorption: The process by which water and dissolved substances pass through a membrane
  • Excretion: The elimination of metabolic waste matter
  • Digestive tract: The alimentary canal
  • Stomach: The portion of alimentary canal in which some protein digestion occurs; its muscular walls churn food so that it is more easily digested; its low-pH environment activates certain protein-digesting enzymes
  • Intestines: Part of the alimentary canal that extends from the stomach to the anus
  • Digestive system: The alimentary canal and glands that ingest, digest, and absorb food
  • Bile: An emulsifying agent secreted by the liver
  • Carnivore: A flesh-eating animal; an animal that subsists on other animals or parts of animals
  • Herbivore: A plant-eating animal
  • Urea: An excretory product of protein metabolism

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