The Digestive System and Excretion

Flashcards covering the key vocabulary and concepts from the lecture notes on the digestive system and excretion.

Nutrient

A substance used for energy, growth, repair, and maintenance.

2,500 Calories

The amount of food energy teenagers need per day.

Nutrients your body needs

Water, carbohydrates, fats, proteins, vitamins, and minerals.

Carbohydrates

Sugars, starches, and cellulose.

Unused carbohydrates

Stored as glycogen in the liver and muscles or stored as fat.

Fats (Lipids)

Fatty acids and glycerol.

Fats Uses

Store energy, make cell membranes, and make steroid hormones; for padding, insulation, and to store some vitamins.

Proteins

Broken down into amino acids, which are used to make other proteins, and used for growth and repair of structures.

Essential Amino Acids

Your body cannot make them.

Vitamins

Dissolve in water or fat, are organic substances, found in foods, needed to keep body functioning in only small amounts.

Minerals

Naturally occurring inorganic substances needed to make substances in the body, to keep nerves and muscles working, and control water balance in cells but cannot be made (must be eaten).

Digestion

The process where the food we eat must be broken down before our body can use it.

Parts of Digestion

Mechanical digestion, chemical digestion, and absorption.

Alimentary Canal

The digestive tract.

Digestion in the Mouth

Break food down into small pieces, saliva makes food easier to swallow and amylase in saliva begins breaking down starch into monosachharides.

Swallowing

Passes from mouth into the pharynx, which causes the epiglottis to close so food doesn’t pass into the trachea and pharynx food moves into the esophagus.

Esophagus

Connects the mouth to the stomach where smooth muscles surrounding the bottom half of the esophagus contract (peristalsis) to push food into the stomach.

Digestion in the Stomach

Mechanically and chemically breaks down food where the stomach makes gastric fluids containing HCl and pepsin which breaks proteins into amino acids.

Gastrin

Controls HCl production to keep the pH below 1.5.

Contracting stomach muscles

Mix the stomach fluids and food into a mixture called chyme.

Cardiac sphincter

Prevents chyme from moving back into the esophagus — otherwise acid reflux occurs.

After about 2 hours

The chyme will move through the pyloric valve and into the small intestine.

Sections of the Small Intestines

Duodenum, jejunum, and ileum.

Small Intestine

Nutrients are absorbed through the lining of the small intestine into the blood stream or lymph vessels.

Villi

Absorption of nutrients occurs through villi.

Duodenum

The liver, gallbladder, and pancreas release digestive fluids into it.

Small Intestines

90% - 95% of nutrients are absorbed in them.

The Pancreas

Makes hormones that control blood sugar levels and makes fluids containing enzymes that digest proteins, fats, carbohydrates, and nucleic acids.

The Pancreas (3)

Makes a fluid that contains sodium bicarbonate to neutralize the HCl to protect the small intestine and allow enzymes to function properly.

Liver

Makes bile (stored in the gallbladder) which breaks fats into small droplets so they can be absorbed, converts excess sugars to glycogen (and the reverse process), changes amino acids, and detoxifies poisons.

Digestive Enzymes

Pepsin, trypsin, amylase, lipases.

The Large Intestines

Also called the colon where water and minerals are absorbed and contains bacteria, dead cells, mucus, and yeast.

Segments of the Large Intestine

Ascending colon, transverse colon, descending colon, cecum, sigmoid, rectum.

Stages of Food Processing

Ingestion, Digestion, Absorption, Elimination.

Excretion

Eliminates waste products and maintains homeostasis.

Waste products

Urine, sweat, CO2, feces.

Lungs

Excrete carbon dioxide and water vapor in exhaled air.

Kidneys

Excrete nitrogen wastes, salts, water, and other substances in urine.

Skin

Excretes water, salts, small amounts of nitrogen wastes, and other substances in sweat.

Kidneys

Control the amount of water and salts in blood plasma & Made of nephrons.

Filtration

Water, nutrients, and wastes are removed from blood.

Reabsorption

Water and nutrients are absorbed back into the blood.

Secretion

Wastes are moved from blood to the tubule.

Filtration (Kidneys: Step 1)

Blood flows into the Bowman’s capsule where it passes through many small capillaries called a glomerulus where excess water, urea, salt, glucose, and amino acids are forced into the hollow interior of the capsule.

Reabsorption and Secretion (Kidneys: Step 2)

Filtrate passes from the Bowman’s capsule into long and narrow renal tubules, Glucose, water, and ions can pass from the tubules back into the blood stream

Urine Formation (Kidneys: Step 3)

Urine passes from the kidneys into the ureters which connect to the bladder, from the bladder urine passes out through the urethra.