Nutrition Chapter 3

Front 1

Why do we eat?

Back 1

A need for food increases production of Grehlin (hormone) which makes us eat more.

Front 2

How do we taste?

Back 2

-taste buds
-detect 5 different tastes:
1. sweet
2. salty (we like because we need Na and Cl ions)
3. sour
4. bitter (prevents us from eating toxins)
5. umami (protein enhanced by MSG)

Front 3

Digestion (definition)

Back 3

to break molecules into smaller molecules; a main function of the digestive tract with respect to food.

Front 4

Absorption (definition)

Back 4

to take in, as nutrients are taken into the intestinal cells after digestion; the main function of the digestive tract with respect to nutrients.

Front 5

Functions of digestive system (6):

Back 5

1. ingestion
2. transport
3. secretion
4. digestion
5. absorption
6. elimination

Front 6

Organs and their functions in digestion:

Back 6

-Mouth: chews and mixes food with saliva
-Salivary Glands: secretes enzymes and mucous
-Pharynx and Esophagus: passages for food
-Stomach: adds acid and enzymes. Mixes, churns, and grinds food. Regulates entry of food into small intestine.
-Liver: manufactures bile (required for fat digestion)
-Pancreas: secretes enzymes and buffers. secretes hormones
-Gallbladder: stores and releases bile
-Small intestine: primary site of digestion and absorption
-Large intestine: reabsorbs water and minerals. Contains bacteria which digest some food and synthesize some vitamins

Front 7

Peristalsis

Back 7

the wavelike muscular squeezing of the esophagus, stomach, and small intestine that pushes their contents along.

Front 8

Chyme

Back 8

the fluid resulting from the actions of the stomach upon a meal

Front 9

Pyloric Valve

Back 9

the circular muscle of the lower stomach that regulates the flow of partly digested food into the small intestine (also called the pyloric sphincter).

Front 10

Segmentation

Back 10

Mixing contractions that knead material back and forth without propelling food forward. This allows for greater contact between the partially digested food and the intestinal juices and enzymes.

Front 11

Mouth:

Back 11

-chewing
-Saliva
1. enzymes (salivary amylase) to help breakdown simple sugars
2. mucus to lubricate the food for easier swallowing
3. lysozyme to kill bacteria
-Tongue
1. taste receptors
2. enzymes to help break down fatty acids
-Epiglottis

Front 12

Stomach

Back 12

-Lower Esophageal Sphincter and Pyloric Sphincter
-Capacity of ~4 cups
-Parietal cells secrete hyrochloric acid (aids in protein digestion and solubilizes minerals for absorption)
-Chief cells secrete enzymes
-Holds food for 2-4 hours
-Results in the formation of chyme
-Mucus layer prevents autodigestion
-Secretion of the intrinsic factor

Front 13

6 layers of digestive tract:

Back 13

1. mucosa
2. sub-mucosa
3. circular muscle
4. longitudinal muscle
5. serosa
6. nerve plexuses

Front 14

Anterograde propulsion:

Back 14

food is propelled in the anterior direction (from mouth to anus)

Front 15

Mechanical Digestion

Back 15

Mixes and reduces the size of food (this primarily happens in the stomach, but also occurs in the small and large intestine)

Front 16

Rate of Propulsion

Back 16

This occurs in the GI tract that aims to optimize time for digestion and absorption to occur

*if rate of propulsion is not regulated it can lead to diarrhea and there will be excessive water and ion loss.

Front 17

cholecystochinin

Back 17

hormonal messenger that stimulates the gallbladder to release bile into the intestine

(bile is an emulsifier = a compound that attracts both fat and water)

Front 18

secretin

Back 18

hormonal messenger that stimulates pancreas to release pancreatic juice containing enzymes and bicarbonate (neutralizes stomach acid)

Front 19

Pancreatic secretions (2):

Back 19

1. Exocrine
-released into the digestive system via a duct
-includes enzymes and buffers (HCO3-)

2. Endocrine
-secreted directly into the bloodstream
-includes hormones such as insulin, glucagon, and secretin

Front 20

Intrinsic Factor

Back 20

secreted by stomach. needed for vitamin absorption

Front 21

Pepsin

Back 21

begins protein digestion

Front 22

Gastric Lipase

Back 22

begins some lipid digestion in stomach

Front 23

Sections of the small intestine:

Back 23

1. Duodenum: most digestion occurs here
2. Jejunum: absorbs digested nutrients
3. Ileum: absorbs digested nutrients

Front 24

Absorption occurs mainly in....

Back 24

the small intestine. Its large surface area allows absorption to take place efficiently. Folds, villi, and microvilli all contribute to the large surface area.

Front 25

Large Intestine:
-digestion
-absorption
-elimination

Back 25

-digestion: most of digestion is already complete. Some digestion of fiber by bacteria

-absorption: water, sodium, potassium, chloride, vitamin K (produced by bacteria)

-elimination: goes through anal canal and rectum

Front 26

Types of Absorption:

Back 26

1. Passive- the unassisted movement of substances down a concentration gradient

2. Facilitated Diffusion: carrier proteins (transporters) in the cell membrane help move substance in or out of a cell down the concentration gradient.

3. Active Transport: the movement of substances in or out of a cell against the concentration gradient using a carrier protein.

4. Endocytosis: the uptake of material by a cell through the indentation and pinching off of part of the membrane to form a vesicle

Front 27

Nutrient Transport (2 systems)

Back 27

1. Blood: direct absorption of glucose, fructose, galactose, and protein, and small lipid molecules. Travels directly to liver

2. Lymph: larger lipid molecules are too big to enter the blood directly. Absorbed first into the lymph

*Some nutrients travel freely in the blood (e.g. glucose, proteins) while others are bound to protein transporters (e.g. lipids, vitamins, and minerals)

Front 28

The two sphincters of the stomach:

Back 28

1. Lower Esophageal Sphincter (LES): prevents reflux of stomach contents into esophagus

2. Pyloric Sphincter: controls movement of stomach contents into the small intestine

Front 29

Constipation

Back 29

-infrequent difficult bowel movements
-often caused by diet, dehydration, inactivity, or medication
-chronic constipation is associated with 2X the risk of colon cancer

Front 30

Diarrhea

Back 30

-frequent watery bowel movements
-often caused by diet, stress, or irritation of the colon
-severe prolonged diarrhea causes dehydration and mineral imbalances
-can lead to irritable bowel syndrome

Front 31

To treat constipation..

Back 31

*don't use laxatives
-defecate when you need to
-the longer you wait, the more water extracted from the feces, the harder it is
-consume sufficient fiber to create softer bulkier stools that stimulate muscle contraction
-drink water
-stay physically active

Front 32

Antacids:

Back 32

-don't work
-stomach just produces more acid to combat antacids.
-can also interfere with absorption of nutrients
-acid reducers can help, but you must check with physician

Front 33

Nephrons

Back 33

the working units in the kidneys, consisting of intermeshed blood vessels and tubules

Front 34

Hiccups

Back 34

spasms of both the vocal cords, and the diaphragm, causing periodic, audible, short, inhaled coughs. Can be caused by irritation of the diaphragm, indigestion, or other causes. Hiccups usually resolve in a few minutes but can have serious effects if prolonged. Breathing into a paper bag (inhaling CO2) or dissolving a teaspoon of sugar in the mouth may stop them.

Front 35

Heartburn

Back 35

a burning sensation in the chest caused by back-flow of stomach acid into the esophagus

Front 36

Ulcer

Back 36

an erosion in the topmost, and sometimes underlying, layers of cells that form a lining. Ulcers of the digestive tract commonly form in the esophagus, stomach, or upper small intestine.

Front 37

Storage of nutrients in the body

Back 37

glycogen: carbohydrate stored in the liver and muscle tissue (liver glycogen can sustain cell activities when the intervals between meals become long)

adipose tissue: liver ships out fat in packages to be picked up by cells that need it. fat cells provide long term energy needs. unlike the liver, fat tissue has virtually infinite storage capacity.

*liver and fat cells store many vitamins, and bones provide reserves of calcium and other minerals

Front 38

Digestion can be limited by 2 things...

Back 38

1. exercise
2. sleep