Topic 3 - Digestive System Flashcards
(33 cards)
Digestive System - Functions + Definition
The digestive system extracts nutrients from food and absorbs them for cell use. The organs of the digestive system perform six key functions:
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– Ingestion – Taking in food and water.
– Mechanical digestion – Physically breaking food into smaller pieces.
– Chemical digestion – Breaking down food using enzymes.
– Movement – Moving food along the alimentary canal
– Absorption – Nutrients and water enter the blood and lymph.
– Elimination – Expelling undigested material.
What is Mechanical Digestion
- The physical breakdown of food into smaller pieces, to increase surface area for chemical digestion
Processes:
- Teeth cut, tear, and grind food.
- Stomach churning breaks food down further.
- Gallbladder releases bile into the small intestine. Bile salts act as emulsifying agents, breaking fat into smaller droplets.
*liver produces bile, gallbladder stores it
Key Concept: Mechanical digestion increases surface area, which speeds up chemical digestion.
What is Chemical Digestion
- Enzymes break down large, complex molecules, into simpler molecules for absorption
Breakdown of Macromolecules:
- Carbohydrates → Monosaccharides (e.g., glucose, fructose, galactose).
- Proteins → Peptides & amino acids.
- Lipids → Fatty acids & glycerol.
- Nucleic acids → Nucleotides.
Enzymes Involved:
- Salivary Amylase: Breaks down starch & glycogen.
- Pepsin: Breaks down proteins.
- Lipase: Breaks down lipids (triglycerides).
What are Amylases
Salivary Amylase:
- Produced by: Salivary glands
- Acts in: Mouth
- Function: Starch → maltose (disaccharide)
Pancreatic Amylase:
- Produced by: Pancreas
- Acts in: Small intestine
- Function: Starch → maltose (disaccharide)
No Intestinal Amylase in humans
Instead: Disaccharidases (like maltase, sucrase, lactase) are produced by the small intestine lining and break down disaccharides into monosaccharides (e.g., maltose → glucose)
What is the Alimentary Canal
A continuous tube running from the mouth to the anus, responsible for digestion and nutrient absorption.
Alimentary Canal - Major Structures and Function
Major structures & functions:
- Mouth & Salivary Glands: Mechanical digestion (chewing) and chemical digestion (salivary amylase for starch).
- Pharynx & Oesophagus: Pushes food into the stomach via peristalsis.
- Stomach: Mechanical digestion (churning), chemical digestion (pepsin for proteins), produces chyme.
- Small Intestine: Absorbs nutrients with villi and microvilli, aided by bile and pancreatic juice.
- Large Intestine: Absorbs water, minerals, and vitamins, forming faeces. Rectum & Anus: Stores and expels waste.
How does Digestion work in the Mouth
- Teeth aid in mechanical digestion.
- Saliva contains salivary amylase, beginning starch digestion.
- Food is formed into a bolus, pushed into the pharynx for swallowing.
Digestion in the mouth - Structure
- Teeth: Different shapes (incisors for cutting, canines for tearing, molars for grinding).
- Salivary glands: Secrete saliva (contains amylase and mucus).
- Tongue: Muscular, helps form and push food into the pharynx.
Digestion in the Mouth - Function
- Mechanical digestion: Teeth break food into smaller pieces.
- Chemical digestion: Salivary amylase starts breaking starch into maltose.
- Lubrication: Mucus helps food move easily.
✔ How structure supports function:
- Sharp incisors & canines for cutting and tearing, flat molars for grinding.
- Salivary glands moisten food for easier swallowing.
- Tongue muscles shape food into a bolus for swallowing.
What is the Esophagus
The esophagus is a muscular tube (about 23-25 cm long) that connects the pharynx to the stomach. It moves food down via peristalsis, a wave-like muscle contraction, and passes through the diaphragm into the abdominal cavity.
How the muscular walls of the esophagus support its function
Muscular walls allow peristalsis.
Circular and longitudinal muscles work together to push food.
Mucus lining reduces friction.
Perystalsis: The involuntary constriction and relaxation of the muscles of the intestine or another canal, creating wave-like movements that push the contents of the canal forward.
What is the Stomach + Its role in digestion
A J-shaped muscular organ that performs mechanical digestion (churning) and chemical digestion (using gastric juice with pepsin to break down proteins). It converts food into chyme before passing it to the small intestine.
How does the Stomachs structure support its function
- Three muscle layers allow powerful churning in multiple directions.
- Gastric pits secrete HCl (kills bacteria) and pepsin (digests protein).
- Pyloric sphincter prevents early release of food.
Small Intestine’s role in Digestion + Structure
- Small Intestine: A 6-7 meter long tube where most digestion and nutrient absorption occur. It consists of the duodenum, jejunum, and ileum, with villi and microvilli increasing surface area for absorption.
How structure of Small Intestine supports its Function
- Long length (6-7m) increases digestion and absorption time.
- Villi & microvilli increase surface area for maximum absorption.
- Enzymes from pancreas and bile from liver assist digestion.
Large Intestine + Role in Digestion
Large Intestine: A 1.5-meter-long section responsible for absorbing water, minerals, and vitamins. It houses bacteria that break down remaining organic material, forming faeces, which are stored in the rectum before elimination.
Large Intestine - How structure supports function
- Wide diameter allows faeces storage.
- No villi since no further digestion occurs.
- Mucus lining helps faeces pass smoothly.
What is the Liver
- Produces bile to emulsify fats.
- Detoxifies blood and stores nutrients.
What is the Gall Bladder + Structure + Function
Structure: Small sac under the liver.
Function: Stores and releases bile into the small intestine.
✔ How structure supports function:
Storage function ensures bile is released only when needed.
What is the Pancreas + Structure + Function
Structure: Located behind the stomach, connected to the duodenum via the pancreatic duct.
Function: Produces pancreatic juice containing: Amylase (starch → maltose). Trypsin (polypeptides → peptides). Lipase (lipids → fatty acids + glycerol).
What is segmentation
- Segmentation is a process of mechanical digestion in the small intestine where circular muscle contractions mix food with digestive juices. Unlike peristalsis, it does not move food forward but helps break it into smaller pieces for better absorption.
What is Chyme
- Chyme is a thick, soupy liquid formed in the stomach when food is mixed with gastric juices and broken down by mechanical and chemical digestion. It then moves into the duodenum for further digestion.
How is the Mucosa of the stomach suited to its function
- The mucosa of the stomach is specialized for secreting gastric juice, which contains hydrochloric acid, mucus, and digestive enzymes (pepsin) to aid in protein digestion.
- The mucus lining protects the stomach from its own acid.
- Gastric glands in the mucosa secrete pepsinogen, which is activated into pepsin in the acidic environment.
What are the features of the small intestine that make it suited to its function?
Long length (6-7 meters) for maximum nutrient absorption.
Villi and microvilli increase surface area for absorption.
Rich blood supply for rapid transport of absorbed nutrients.
Enzyme secretion from the pancreas and intestinal glands aids in digestion.
Bile salts emulsify fats to enhance absorption.
