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Topic 9. Definitions thanks to Pearson Education.


Group of cells with common structure and function


Functional units of tissues

Organ system

Groups of organs that work together

Epithelial tissue

Sheets of tightly packed cells that cover the body, line the organs, and act as a protective barrier

Connective tissue

Supports and binds other tissues, and consist of scattered cells within an extracellular matrix

Muscle tissue

Responsible for nearly all types of body movement, and made up of the proteins actin and myosin

Nervous tissue

Divided into functional units called nerve cells, which senses stimuli and transmits signals from one part of the body to another


Animals maintain a relatively constant internal environment, even when the external environment changes significantly

Set point

The "target" in homeostasis. Sensors detect stimuli below or above this point and trigger a physiological response to help the body return to the set point

Negative feedback systems

Animal responds to a stimulus in a way that reduces the stimulus (e.g. after exercise, the body temperature rises, so sweating cools the body)

Positive feedback systems

Change in a variable triggers mechanisms that amplify rather than reverse the change (e.g. during childbirth, pressure of baby's head stimulates greater contractions, which cause greater pressure, etc)


How animals maintain their internal temperature


Warmed by heat generated by metabolism, includes mammals and birds


Gain heat from external sources, includes, fish, invertebrates, amphibians, and reptiles

Countercurrent exchange

Antiparallel arrangement of blood vessels result in warm blood from the core heating cold blood from the extremities

Essential nutrients

Minerals and preassembled organic molecules that an animal cannot produce from raw materials

Essential amino acids

About half of the 20 amino acids, cannot be obtained from food

Essential fatty acids

Used to make cell membranes, must be ingested


Organic molecules that must be ingested


Inorganic nutrients that must be ingested


Act of taking in food


Breakdown of food into small molecules capable of being absorbed by the cells of the body


Stage of food processing where the body's cells take up small molecules such as amino acids and simple sugars from the digestive tract


Passing of undigested material from digestive tract

Intracellular digestion

Occurs within a cell enclosed by a protective membrane, technique used by sponges

Extracellular digestion

Food is broken down outside cells, allows animals to devour larger food sources, technique used by most animals

Gastrovascular cavity

One chamber for digestion to take place in. Animals with this have one opening from which food enters and waste is eliminated.

Alimentary canals

Complete digestive tracts


Muscular, ringlike valves that regulate passage of material between digestive compartments


Rhythmic waves of contraction by smooth muscle in the walls of the alimentary canal

Oral cavity

Mouth, where digestion begins


Enzyme in saliva that begins hydrolyzing starch and glycogen into smaller polysaccharides and the disaccharide maltose


What food is shaped into during chewing


Junction that opens to the esophagus and trachea


Cartilage flap that covers the trachea and prevents food from entering the airway


Moves food down the pharynx down to the stomach through peristalsis

Gastric juice

Secreted by the stomach to begin digestion, includes hydrochloric acid and pepsin

Hydrochloric acid

Breaks down ECM of meat and plant materials, and kills bacteria. Has a pH of about 2


Hydrolyzes proteins into smaller polypeptides. Secreted as pepsinogen so the cells that produce it aren't digested themselves


Protects stomach lining

Acid chyme

Result of stomach digestion

Pyloric sphincter

Moves acid chyme from stomach to small intestine


Major site of chemical digestion where acid chyme mixes with pancreatic and liver secretions

Bicarbonate fluid

Buffer, released from pancreas


Made in liver and stored in gall bladder, emulsifies fats in the duodenum

Carbohydrate digestion

Begins with breakdown of starch and glycogen by salivary amylase. In the small intestine, pancreatic amylases continue to break them down into the disaccharide maltose. This is broken into its monomers at the wall of the duodenum epithelium

Protein digestion

Begins with breakdown of proteins by pepsin in the stomach. In the duodenum, trypsin and cymotrypsin break the polypeptides into smaller chains. Dipeptidases, carboxypeptidase, and aminopeptidase break apart polypeptides into amino acids

Nucleic acid digestion

Starts with hydrolysis of DNA and RNA into nucleotides. Then they are broken into nitrogenous bases, sugar, and phosphate groups. Most enzymes involved are from the pancreas


Starts in the small intestine when bile coats the fat droplets. Then lipase from the pancreas hydrolyzes the droplets


Folds in the epithelial lining of the small intestine that increase surface area


Projections of villi


In the villi, a lymph vessel that absorbs small fatty acids

Hepatic portal vessel

Destination of capillaries in villi that drain away nutrients--the hepatic portal vessel takes the nutrients to the liver for distribution


Stomach hormone that increases gastric juice production


Hormone produced by the duodenum in the presence of fats to slow peristalsis and allow more time for fat digestion

Secretin and cholecystokinin

Hormone secreted by walls of the duodenum and increase the flow of digestive juices from pancreas and gall bladder


Large intestine


Where small intestine connects with large intestine, has an extension called the appendix


Correlates with diet

Open circulatory system

Blood bathes the organs directly, found in mollusks and arthropods


Combined blood and lymph in an open circulatory system


Where hemolymph is pumped

Closed circulatory systems

Blood is contained in vessels and pumped around the body


Carry blood away from the heart


Small branches of arteries


Composed of only a single layer of cells, the endothelium. Where diffusion occurs


Carry the blood back to the heart


Receive blood


Pump blood


Contraction phase


Relaxation phase

Heart rate

Contractions per minute

Stroke volume

Amount of blood pumped by left ventricle per contraction

Atrioventricular (AV) valve

Prevents backflow of blood into the atria

Semilunar valves

Prevents backflow of blood into the ventricles

Sinoatrial (SA) node

Pacemaker, located in the upper wall of right atrium

AV node

Delays impulses from SA node to allow the atria to completely empty before the ventricles contract, located in the lower wall of right atrium

Blood pressure

Systolic pressure/Diastolic pressure (e.g. 120/70)

Lymphatic system

Returns lost fluid and proteins to the blood in the form of lympth

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