Digestive Review

Six important processes accomplished by the digestive system

• ingestion - taking in foods/liquids

• Propulsion - moving food through digestive tract

• Mechanical digestion - physical breakdown of food (chewing)

• Chemical digestion - digestion enzymatic breakdown of food

Divisions of digestive system

• alimentary canal (GI tract)

• Accessory digestive organs

Accessory organ ex

• teeth

• Tongue

• Salivary gland

• Liver

• Gallbladder

• Pancreas

Difference between organs in digestive tract and accessory organs

• digestive tract - food passes through them

• Accessory - food does NOT pass through them, help digestion by producing/secreting substances

Where does alimentary canal start and end

Start-mouth

Ends-anus

Correct order for layers in the all of alimentary canal from innermost to outermost

• mucosa

• Submucosa

• Muscularis

• Serosa

Which layer of alimentary canal is responsible for absorption

Mucosa

Three accessory organs of mouth

• salivary glands

• Teeth

• Tongue

Functions of saliva

• moistens food

• Dissolves food chemicals for taste

• Helps swallowing

• Begins digestion of carbs

What are the parotid glands

Largest salivary glands, located near ears, projecting saliva rich in amylase

Where does chemical digestion of carbohydrates begin?

Mouth→salivary amylase

Four types of teeth in mouth and function of each

• incisors- cut

• Canines-tear

• Premolars-crush

• Molars-grind

Three segments of pharynx

• nasopharynx

• Oropharynx

• Laryngopharynx

What happens in swallowing reflex/parts of swallowing reflex

Voluntary Phase**: Tongue pushes food to the back of the mouth.

  - Involuntary Phase: 

    - Soft palate elevates, closing off the nasopharynx.

    - Epiglottis covers the trachea.

    - Peristalsis begins in the esophagus to push food down.

Where is the epiglottis found?

Entrance of larynx

What is peristalsis and where does it occur in the digestive system?

- Definition: A series of wave-like muscle contractions that move food through the digestive tract.

- Where It Occurs: Begins in the esophagus and continues throughout the stomach and intestines.

List 5 functions of stomach, what digestion takes place?

- Storage: Holds food before digestion.

- Digestion: Mechanical mixing and chemical digestion of proteins.

- Secretion: Produces gastric juices (HCl and enzymes).

- Absorption: Limited absorption of certain substances.

- Defense: Acidic environment kills pathogens.

Main part of stomach

- Body: The central region where most digestion occurs.

What are ridges in the stomach called

- Rugae: Folds that allow the stomach to expand and contract.

Three things absorbed in stomach

- Water

- Alcohol

- Certain medications

What digestive enzymes are found in pancreas, what do they digest?

- Amylase: Digests carbohydrates.

- Lipase: Digests fats.

- Proteases (e.g., trypsin, chymotrypsin): Digest proteins.

Functions of liver (3)

- Produces bile for fat digestion.

- Metabolizes nutrients (carbohydrates, proteins, fats).

- Detoxifies harmful substances

Function of bile

- Emulsifies fats to increase surface area for digestion by lipases.

function of gallbladder

- Stores and concentrates bile until it is needed for digestion.

Three functions of small intestine

- Digestion: Completes digestion of carbohydrates, proteins, and fats.

- Absorption: Absorbs nutrients and water into the bloodstream.

- Mixing: Combines food with digestive juices for efficient digestion.

Ridges in small intestine

Villi and microvilli

how are the acidic contents of the stomach buffered in the small intestine?

- Bicarbonate is secreted by the pancreas to neutralize stomach acid.

Functions of large intestine

- Absorption: Absorbs water and electrolytes.

- Defecation: Forms and expels feces.

Digestion of protein

- In the Stomach: Proteins are denatured by stomach acid and digested by pepsin.

- In the Small Intestine: Further broken down by pancreatic enzymes (trypsin, chymotrypsin) into amino acids for absorption.

Difference between large and small intestine

- Small Intestine: Has a smoother surface with many folds (plicae circulares).

- Large Intestine: Has a wider diameter, fewer folds, and is often more sacculated (haustra).

Organs that absorb nutrients

- Small Intestine: The primary site for nutrient absorption.

- Large Intestine: Absorbs water and electrolytes.

Digestion of carbs after eating a candy bar in mouth

- In the Mouth: Salivary amylase begins breaking down carbohydrates into simpler sugars.

Digestion of carbs in stomach

the stomach physically churns and mixes chewed food into a semi-liquid called chyme, the highly acidic environment deactivates salivary amylase

Carb digestion in small intestine

- In the Small Intestine: Pancreatic amylase continues digestion; enzymes like maltase, lactase, and sucrase break down sugars into monosaccharides.

Absorption in carb digestion

- Absorption: Monosaccharides are absorbed through the intestinal walls into the bloodstream.

Absorption in the digestive system

- Small Intestine: Absorbs carbohydrates, proteins, fats, vitamins, and minerals.

- Large Intestine: Absorbs water and electrolytes.

Location and function of uvula

- Found: Hanging from the soft palate at the back of the throat.

- Function: Helps prevent food from entering the nasal cavity during swallowing and aids in speech.

Parts of small intestine in order

1. Duodenum

2. Jejunum

3. Ileum

Duodenum

the very first and shortest section of the small intestine. Sitting just below the stomach, it acts as a crucial mixing and staging area where food is further broken down and prepared for nutrient absorption

Jejunum

the middle section of the small intestine, located between the duodenum and the ileum. Measuring roughly 8 feet long, its primary role is to break down food and absorb the vast majority of vital nutrients into bloodstream

Ileum

final, longest segment of the small intestine. Its primary functions are to absorb critical nutrients (especially Vitamin B12 and bile acids) that were missed by the jejunum, finalize digestion, and pass remaining waste to the large intestine

Type of movement in small intestine

- Segmentation: Mixing food with digestive juices.

- Peristalsis: Moving food along the digestive tract.

Ridges in small intestine

Circular folds

Gastrin

Stimulates gastric acid secretion.

Trypsin and chemotrypsin

Digests proteins

Trypsin- basic

Chemotrypsin- aromatic

Lipase

digests fats

Lipase

digests fats

Bile salts

Emulsify fats

Bicarbonate

Neutralizes stomach acid

Maltase

Breaks down maltose into glucose.

Lactase

Breaks down lactose into glucose and galactose.

Sucrase

Breaks down sucrose into glucose and fructose.

Parts of large intestine in order

1. Cecum

2. Ascending Colon

3. Transverse Colon

4. Descending Colon

5. Sigmoid Colon

6. Rectum

7. Anus

Components of feces

- Water

- Fiber

- Bacteria

- Cells shed from the intestinal lining

- Undigested food residues