Week 11 (Digestive System)

Question 1

DIGESTIVE SYSTEM

Answer 1

The digestive system performs the following functions:

Mechanical and chemical processes of digestion

Absorption of nutrients

Elimination of wastes

Question 2

Divisions of the Digestive System

Answer 2

Alimentary canal / gastrointestinal (GI) tract

Accessory digestive organs

The digestive system consists of a hollow, muscular tube that extends from the oral cavity to the anus.

Question 3

FUNCTIONS OF THE DIGESTIVE SYSTEM

Answer 3

Ingestion:
The process of taking in food.

Motility:
Controlled movement of materials through the digestive tract
Propulsive movement: Unidirectional
Mixing movement: Bidirectional

Digestion:
Mechanical Digestion: Physical breakdown of food (chewing, churning, segmentation)
Chemical Digestion: Enzymes break down macromolecules into usable nutrients
Carbohydrates → Monosaccharides
Proteins → Amino acids
Lipids → Fatty acids and glycerol
Nucleic acids → Nucleotides

Secretion:
Digestive juices from glands
Hormones from endocrine glands
Regulates digestion, secretion, absorption, GI motility

Absorption:
Digested food into bloodstream
Fluids and electrolytes
Maintains fluid and electrolyte balance

Elimination of Wastes:
Removal of indigestible substances
Defecation

Immune Function:
Lymphatic tissue along GI tract aids immune defense

Question 4

Oral Cavity (Mouth)

Answer 4

Functions: Ingestion

Mechanical Digestion: Teeth chew, tongue mixes food

Chemical Digestion: Salivary amylase starts carb digestion

Question 5

Pharynx (Throat)

Answer 5

Passageway for food, liquids, air

Moves food into esophagus

Epiglottis covers trachea when swallowing

Question 6

Esophagus

Answer 6

Propels food to stomach via peristalsis

UES and LES regulate movement

Deglutition = Swallowing

Question 7

Stomach

Answer 7

Functions: Temporary food storage (1.5L), mixing movements

Mechanical Digestion: Churning

Chemical Digestion: Protein digestion starts

Secretion: Gastric juice, gastrin

Regulates chyme to small intestine

Gastric Juice Composition:
HCl: pH 2, kills bacteria, activates pepsin
Pepsinogen → Pepsin
Intrinsic Factor: B12 absorption
Mucous: Protects lining

Question 8

Small Intestine

Answer 8

~20 ft long: Duodenum, Jejunum, Ileum

Duodenum: Secretes juices, chemical digestion

Jejunum: Absorbs 90% of nutrients

Ileum: Absorbs water, bile salts, B12, remaining nutrients

Motility: Segmentation, peristalsis

Secretion: Intestinal juice with enzymes

Main site of digestion/absorption

Villi and microvilli → increased surface area

Question 9

Large Intestine

Answer 9

Divisions: Caecum, Colon (ascending, transverse, descending, sigmoid), Rectum

Functions:

Motility: Mixing, peristalsis

Absorption: Water, electrolytes

Storage: Feces

Elimination: Defecation

Vitamin synthesis by bacteria (e.g., B12, K)

Question 10

Teeth

Answer 10

Mastication: Breaks down food

Increases surface area for enzymes

Question 11

Salivary Glands

Answer 11

Three pairs: Parotid, Sublingual, Submandibular

Saliva:
Contains amylase (carb digestion)
Moistens food
Protects enamel, inhibits bacteria
Stimulates taste buds

Question 12

Liver

Answer 12

Functions:

Secretes bile (bile salts, bicarbonate, lecithin)

Bile emulsifies lipids

Metabolizes/detoxifies drugs/hormones

Stores vitamins/minerals (A, D, E, K, B12)

Activates vitamin D

Synthesizes plasma proteins

Question 13

Gallbladder

Answer 13

Stores & concentrates bile (up to 20x)

Releases bile for fat digestion

Question 14

Pancreas

Answer 14

Endocrine: Insulin, glucagon, somatostatin → blood

Exocrine: Pancreatic juice (enzymes + bicarbonate) → duodenum
-Enzymes digest carbs, proteins, fats
-Bicarbonate neutralizes stomach acid