6.1 - Digestive System

Question 1

Digestion (Types)

Answer 1

Mechanical digestions: break down of food into smaller components by muscular activity (chewing, churning)
Chemical digestion: break down of food by digestive fluids, enzymes

Question 2

Peristalsis

Answer 2

Peristalsis: waves of smooth muscle contractions moving food down the dietary tract/small intestines and mixing food with enzymes, unconsciously controlled by the enteric nervous system
Circular muscle: contracts behind food in the gut to prevent it from returning out the mouth
Longitudinal muscle: contracts where food is located to move it along the gut.

Question 3

Pancreas

Answer 3

2 glands, secretes hormones (insulin, glucagon) into the blood and digestive enzymes in pancreatic juice into the gut lumen through ducts.

Digestive enzymes: synthesized by pancreatic gland cells on ribosomes of rER, secreted by exocytosis (after processing by GA)

Pancreatic juice: contains amylase, lipases, proteases

Question 4

Digestive enzymes

Answer 4

Digestive enzymes: break down food macromolecules into monomers by hydrolysis
Amylase: digests starch (carbohydrates) into maltose
Lipases: digests triglycerides (lipids) into fatty acids and glycerol/monoglycerides
Proteases: digests proteins and peptides into shorter peptides or amino acids
Exopeptidases: removes 1 amino acid from peptides until it becomes a dipeptide
Dipeptidases: digests dipeptides into amino acids
Nucleases: digest DNA and RNA into nucleotides
Maltase: digest maltose into glucose
Lactase: lactose into glucose and galactose
Sucrase: sucrose into glucose and fructose

Question 5

Villi

Answer 5

Small projections of the mucosa inside the small intestines wall to increase surface area of epithelium for absorption of nutrients into cells and blood
larger SA -> faster rate of absorption
Increases SA by a factor of 10

Question 6

Epithelium of small intestines (permeable substances)

Answer 6

Epithelium: layer of cells that cover the villi as a permeable barrier allowing absorption of nutrients (monomers broken down from digestion) and protection from harmful substances.
- Monosaccharides (glucose, fructose, galactose
- Amino acids
- Fatty acids, glycerol, monoglycerides
- Mineral ions (calcium, potassium, sodium)
- Bases (from nucleotides)
- Vitamins
Harmful substances that manage to pass through are removed
- blood is detoxified by the liver and removed as urine
- Removed from the blood by phagocytosis

Question 7

Absorption of fatty acids in the small intestines

Answer 7

into epithelium cells of intestines: non-polar absorbed through simple diffusion through the plasma membrane, the surface area is increased with microvilli

out of epithelium cells to villus: by exocytosis by reforming into triglycerides and merging with cholesterol and phospholipids forming lipoproteins

enter lymphatic system through lacteals

Question 8

absorption of glucose in intestines

Answer 8

into epithelium cells: secondary active transport, co-transport with sodium ions as sodium-potassium pump transports sodium out of the epithelium into the lumen of intestines

out of epithelium cells into villus: facilitated diffusion through glucose channels

into blood stream through capilaries

Question 9

Digestive system diagram

Answer 9

mouth: salivary amylase, chewing
esophagus: peristalsis
stomac: acidic, protease, churning, signals pancreatic fluid secretion
small intestines: neutralize stomach acid, food break down, absorption of nutrients/vitamins/minerals
large intestines: absorption of water, breakdown of carbs by gut bacteria, feces storage
anus
liver: filter blood of waste, secretes surfactants for bile
gall bladder: stores and releases bile
pancreas: pancreatic juice, amylase, protease (endopeptidase), lipase

Question 10

Tissue layer of small intestines

Answer 10

Mucosa: inner layer facing lumen, includes epithelium and villi
submucose: next layer with blood vessels and lymph vessels
muscle layer: circular muscles and longitudinal muscles on outside
serosa: outermost layer