HON ANATOMY: Digestive System Study Guide, Nutrition Basics: Serving Size, Calories, Fat

digestive system

the body system that breaks down food and absorbs nutrients

digestion

the process of breaking down food into nutrients

mechanical digestion

the physical breakdown of food into smaller particles through actions like chewing/grinding

chemical digestion

the enzymatic breakdown of complex molecules into simpler ones, typically occurring in the digestive tract (stomach)

absorption

the process that allows substances you eat to be taken up by blood

where is gastric juice produced? what is a digestive enzyme that is found in gastric juice?

- gastric juice = folded lining of the stomach which as gastric pits containing the juice
- enzyme = pepsin

Mixing with it is [---] released from the pancreas. This juice contains [---], [---], and [---]

- pancreatic juice
- amylase, protease, and lipase

where does digestion begin and what is the first macromolecule (carbohydrate, protein, lipids, or nucleic acids) that is broken down there?

- digestion begins with the mouth
- release of digestive enzymes by salivary glands (major salivary enzyme is amylase)
- begins the chemical digestion of carbohydrates by breaking down starch into sugar

digestive system labels (look in notes)

- mouth
- esophagus
- stomach
- small intestine
- large intestine
- anus
- rectum
- pancreas
- liver

mouth

- Structure: Oral cavity with teeth, tongue, and salivary glands.
- Function: Mechanical breakdown of food by chewing, initiation of carbohydrate digestion via salivary amylase, and formation of bolus for swallowing.

salivary glands

- Structure: Parotid, submandibular, and sublingual glands.
- Function: Produce saliva containing enzymes (e.g., amylase) and lubricating fluids to facilitate swallowing and initial digestion of carbohydrates.

pharynx

- Structure: Muscular tube at the back of the throat.
- Function: Passage for food and air; initiation of swallowing reflex.

esophagus

- Structure: Muscular tube connecting the pharynx to the stomach.
- Function: Propels food bolus from the pharynx to the stomach via peristaltic contractions.

liver

- Structure: Largest internal organ located in the upper right abdomen.
- Function: Produces bile, metabolizes nutrients, detoxifies harmful substances, stores glycogen, and synthesizes proteins.

stomach

- Structure: J-shaped organ in the upper abdomen.
- Function: Stores and mixes food with gastric juices, initiates protein digestion by pepsin, and regulates the release of chyme (partially digested food) into the small intestine.

pancreas

- Structure: Gland located behind the stomach.
- Function: Secretes pancreatic juices containing enzymes (e.g., amylase, lipase, proteases) into the small intestine to aid in the digestion of carbohydrates, fats, and proteins.

small intestine

- Structure: Long coiled tube comprising duodenum, jejunum, and ileum.
- Function: Primary site of nutrient absorption (e.g., carbohydrates, proteins, fats) into the bloodstream, facilitated by villi and microvilli.

large intestine

- Structure: Larger diameter tube comprising cecum, colon, and rectum.
- Function: Absorbs water and electrolytes from indigestible food residues, forms and stores feces, and houses beneficial bacteria (intestinal flora).

gallbladder

- Structure: Small sac located beneath the liver.
- Function: Stores and concentrates bile produced by the liver, releases bile into the small intestine to aid in fat digestion and absorption.

rectum/rectus

- Structure: Terminal portion of the large intestine.
- Function: Stores feces before defecation; initiates the urge to defecate.

anus

- Structure: External opening at the end of the digestive tract.
- Function: Controls the expulsion of feces from the body during defecation.

alimentary canal

- Structure:
Mouth: Entry point for food ingestion; contains teeth and salivary glands.
Pharynx: Common passage for both air and food.
Esophagus: Muscular tube connecting the pharynx to the stomach.
Stomach: J-shaped organ in the upper abdomen.
Small Intestine: Long coiled tube comprising duodenum, jejunum, and ileum.
Large Intestine (Colon): Larger diameter tube comprising cecum, colon, and rectum.
Anus: External opening at the end of the digestive tract.
- Function:
Ingestion: Intake of food through the mouth.
Mechanical Digestion: Physical breakdown of food by chewing (in the mouth) and peristalsis (movement) throughout the digestive tract.
Chemical Digestion: Breakdown of food molecules into smaller, absorbable nutrients by enzymes and gastric juices.
Absorption: Process of nutrients crossing the intestinal wall into the bloodstream for distribution to the body's cells.
Secretion: Release of digestive enzymes, acids, and other substances necessary for digestion from glands along the alimentary canal.
Excretion: Elimination of undigested food material (feces) from the body through the anus.

accessory organs

- liver = massive/fatty, 4 lobed organ; main goal is to make bile (stored in gallbladder)
- pancreas = brews up pancreatic juice (trypsin + peptidase)
- large intestine = colon, rectum, anus; reabsorbs water from chyme = poop

epiglottis

a flap that is right above two tubes (the esophagus/the trachea)

peristalsis

the involuntary constriction/relaxation that creates wave-like movements that push the contents of the canal forward

stomach lining (mucus)

prevents stomach from digesting itself, small openings called gastric pits contain glands; glands secrete gastric juices to breakdown food

gastric juices

- HCL (hydrochloric acid) = makes the stomach acidic so pepsinogen can be converted into pepsin
- Pepsinogen -> pepsin = most important digestive enzyme for breaking down proteins into a smaller form
- lipase = enzyme responsible for the breakdown of fats

chyme

paste, after food has been broken down released then into the duodenum via the pyloric sphincter valve

pancreatic juice

includes amylase, pancreatic lipase

duodenum

- main section of the small intestine where digestion is still occurring
- 3 important digestive juices are add here:
Bile
Pancreatic juices
Intestinal juices
- Where absorption starts

bile

- Produced in the liver
- Stored in the Gallbladder
- Enters the small intestine through the bile duct
- Two Functions:
- Bile is alkaline (basic), so it neutralizes the acid which was added in the stomach. This allows the enzymes to work
- Bile emulsifies fats
Breaking down large molecules of fats into small droplets, which allow the enzyme lipase to start breaking the fat droplets down further

pancreatic juices

- Enzymes created in the pancreas, released in the duodenum
- Pancreatic Amylase breaks down carbohydrates
- Trypsin breaks down proteins
Pancreatic Lipase breaks down lipids (fats)

intestinal juices

- The glands in the wall of the small intestine produce intestinal juice
- Maltase breaks down carbohydrates
Peptidase breaks down proteins
Intestinal Lipase breaks down lipids (fats)

enzymes

(look into notes)
- Selectively speed up the breakdown of specific nutrient molecules.

cecum (large intestine)

start of large intestine, has an attached appendix

colon (large intestine)

4 section ascending/transverse/descending/sigmoid

carbohydrate digestion

the process of breaking down complex carbohydrates into simpler sugars for absorption

protein digestion

the process of breaking down proteins into amino acids for absorption

fat digestion

the process of breaking down fats into fatty acids and glycerol for absorption

Villi absorption

- when villi are taller, there is more surface area for nutrients to come into contact with absorptive cells, creating a greater intake of nutrients
- taller villi = more space for nutrients to be absorbed

Serving Size

Basis of a food label; all numbers correspond to this.

What do calories measure?

Energy needed or ingested per day

How is a calorie defined?

The amount of heat needed to raise 1kg of water by 1 degree Celsius

What is fat?

Nutrient; important source of energy and provide insulation and cushioning for skin, bone, and major organs.

What are the types of fats?

Fats can be unsaturated, saturated, or trans.

Unsaturated fats

Considered 'good fats'; found in vegetable oils, nuts, and fish. Don't raise cholesterol levels as much as the others.

Saturated fats

Considered 'bad fats'; raise cholesterol levels.

Trans fats

Considered 'bad fats'; raise cholesterol levels.

Cholesterol - HDL vs. LDL

LDL is 'bad' cholesterol; HDL is 'good' cholesterol.

Cholesterol

Important for vitamin D production and hormone synthesis.

What is sodium?

Component of salt

How does sodium affect the body?

Small amounts keep proper body fluid balance and help transmit electrical signals through nerves

What are the consequences of excessive sodium intake?

It can increase water retention and blood pressure in people who are sensitive to it

Fiber

Indigestible; reduces cholesterol levels , no calories and keeps you full.

Protein

Major body component; can be used for energy in the absence of fat and carbohydrates (difficult process).

LDL

low-density lipoprotein; high LDL levels lead to a buildup of cholesterol in the arteries

HDL

high-density lipoprotein; absorbs cholesterol into the blood and carries it back to the liver