IB Bio Topic 6.1 - Structure of the Digestive System

Assimilation

The process in which essential molecules from ingested food enter the bloodstream to be accessed by body cells for cellular activities.

Alimentary Canal (Digestive Tract)

Organs that form the “tube” of the digestive system.

Accessory Organ

In the digestive system, these types of organs secrete chemicals into the main tube of the system.

Pancreas

Secretes amylase, lipase, and protease into the small intestine.

Liver

Secretes bile to emulsify lipids (break them into smaller particles).

Gall Bladder

Stores bile.

Bile

a SUBSTANCE secreted by the liver. It is not an enzyme and does not hydrolyze any reactions.

Mouth

Where food is mechanically chewed and mixed with amylase-containing saliva; carbohydrate digestion begins

Bolus

mixture of food and saliva

Peristalsis

a wave of contraction and relaxation of the longitudinal and circular muscles along the alimentary canal, forcing contents through the tube

Chyme

mixture of bolus from the esophagus and stomach acid

Small Intestine

a long, muscular tube located between the stomach and large intestine in humans

Duodenum

first section of the small intestine

Jejunum

middle section of the small intestine

Ileum

last section of the small intestine

Serosa

outermost layer of the small intestine, has connective tissue that touches body cavities

Submucosa

connective tissue of the small intestine; supports mucosa, contains large veins & arteries that result in the mucosa’s capillary bed

Mucosa

innermost layer of the small intestine, forms soft lining of the tube, made of epithelium

Lumen

physical space in the center of intestines, arteries, and other tubular structures of the human body

Duct Cells

Cells from the pancreas that transport enzymes produced by acinar cells. They also secrete sodium hydrogen carbonate to neutralize stomach acid.

Acinar Cells

Cells from the pancreas that secrete digestive enzymes.

Amylase

an enzyme that breaks down starch into maltose

Endopeptidase (Trypsin)

an enzyme that breaks down proteins into smaller polypeptides

Lipase

enzymes that break down lipids into glycerol and fatty acid monomers

Phospholipase

enzymes that break down phospholipids into glycerol, fatty acid, and phosphate monomers

Nuclease

an enzyme that breaks down DNA and RNA

Maltase

an enzyme that breaks down maltose into glucose

Lactase

an enzyme that breaks down lactose into galactose and glucose

Exopeptidase

an enzyme that removes a single amino acid from the end of small peptides

Dipeptidase

an enzyme that breaks dipeptides into two amino acids

Absorption

The taking in of digested food substances, vitamins, and minerals from the lumen of the small intestine into the blood

Villi

specialized structures that cover the inner surface of the small intestine, increasing its surface area

Epithelial Cells

the cells in villi where absorption actually occurs

Goblet Cells

cells in villi that produce mucus

Lamina propia

connective tissue of the villus

Microvilli

projections of each epithelial cell of a villus. They further increase the surface area of the small intestine.

Lacteal

a structure within the villi of the digestive tract that connects to the lymph.

Maltose

a dimer made up of two glucose molecules linked by 𝝰-1,4 glycosidic bonds

Maltotriose

a trisaccharide made up of three glucose molecules linked by 𝝰-1,4 glycosidic bonds

Glucosidase

an enzyme that breaks down maltotriose

Dextrin

small polymers that contain 𝝰-1,6 glycosidic bonds. They are left over after amylopectin’s 𝝰-1,4 glycosidic bonds are broken up by amylase

Dextrinase

an enzyme that breaks down dextrin

Dialysis

the separation of smaller molecules from larger molecules in a solution by selective diffusion through a semipermeable membrane