Biology — The Digestive & Excretory Systems

What does the digestive system do?

it breaks food into small molecules that cells can use

What are the two kinds of digestion?

mechanical (physical breakdown) and chemical (using enzymes and bile)

What is mechanical digestion?

the physical breakdown of food, like chewing and churning

What is chemical digestion?

the breakdown of food using enzymes and bile

What is the path of food through the digestive tract?

mouth, oesophagus, stomach, small intestine, large intestine, rectum, and anus

What happens in the mouth?

teeth grind the food, and amylase in saliva begins breaking down carbohydrates

What is amylase?

an enzyme in saliva that starts breaking down carbohydrates

What is a bolus?

the ball of chewed food formed in the mouth

What does the oesophagus do?

it carries the bolus from the mouth to the stomach, with no digestion

What happens in the stomach?

its walls churn the food while acids and enzymes break it down chemically

What is pepsin?

a stomach enzyme that breaks down most protein

What is chyme?

the liquid that the stomach turns the bolus into

What happens in the small intestine?

most chemical digestion and most nutrient absorption take place there

What is absorption?

nutrients passing through the digestive wall into the blood

What does bile do, and where is it made?

it digests fats, and it is made in the liver and stored in the gallbladder

What is the first part of the small intestine?

the duodenum

What does the large intestine do?

it removes water, and its bacteria produce compounds like vitamin K

What is left at the end of the large intestine?

concentrated waste called faeces

What do the rectum and anus do?

the rectum stores faeces and the anus eliminates them

What are the accessory digestive organs?

the salivary glands, liver, gallbladder, and pancreas

What does the pancreas do in digestion?

it secretes juices with enzymes for digesting protein and carbohydrates

What does the liver do in digestion?

it makes bile, detoxifies the blood, and processes vitamins

What does the excretory system do?

it removes metabolic wastes from the body

What are the main organs of the excretory system?

the kidneys

What do the kidneys do?

they filter the blood, regulate water balance, and make urine

Besides the kidneys, what other organs help excrete waste?

the skin through sweat, the lungs through carbon dioxide, and the liver

What waste does the liver produce?

urea, formed from nitrogenous waste

What is a nephron?

the functional unit of the kidney that makes urine

What are the three steps of urine formation?

filtration, then reabsorption, then excretion

What happens during filtration?

blood is filtered, keeping cells and large proteins behind

What happens during reabsorption?

water and nutrients are reabsorbed back into the blood

What is the path of urine out of the body?

kidneys, then ureters, then the bladder, then out through the urethra

Where does digestion actually begin?

in the mouth, not the stomach

Which system does urine come from?

the excretory system, not the digestive system

Which intestine is longer, and how are they named?

the small intestine is longer, and they are named for diameter rather than length