intro to nutrition chapter three- digestion, absorption and transport

digestion

the breakdown of foods into nutrients

what are the steps or digestion?

• mouth

• esophagus

• stomach

• small intestine

• large intestine

• rectum

• anus

portion of chewed foods mixed with saliva that is passing down into the esophagus

bolus

peristalsis

waves of smooth muscle contraction in the walls of the alimentary canal

what does the action of peristalsis do?

this moves what we’ve swallowed down to our stomachs

gastrointestinal tract

a long hollow tube that extends from the mouth to the anus that is responsible for digesting food, absorbing nutrients and water, then eliminating waste

five basic sensations of taste

• sweet

• bitter

• sour

• salty

• umami/savory

does aroma, texture and temperature affect the flavor?

yes

process of digestion begins here

• __ breaks up food

• fluids from the salivary glands blends with food and liquid to ease swallowing

mouth

what enzymes start the digestion process in the mouth?

amylase and lipase

swallowed food passes through here

pharynx

whats another word for the pharynx?

throat

what are two more words used commonly to discuss the gastriintestinal tract?

digestive tract and alimentary canal

has a sphincter muscle at each end, connects the pharynx to the stomach

esophagus

what happens to the bolus once it goes down your esophagus?

moves into your stomach

food matter (bolus) that mixes with stomach acid

chyme

circular, longitudinal and diagonal layers

these are the muscles that mix stomach content

controls the release of chyme into the small intestine

pyloric sphincter

esophageal sphincter

a ring shaped muscle that relaxes or tightens to open or close a passage

receives chyme from the stomach and continues the breakdown process with enzymes from the pancreas and liver

small intestine

What does the pancreas do in digestion?

Secreting digestive enzymes into the small intestine

What is the function of the epiglottis?

to prevent food from entering the trachea

what are the three segments of the small intestine?

• duodenum

• jejunum

• ileum

duodenum

First part of the small intestine; receives chyme from the stomach and secretions from the pancreas and liver (bile). Main site of chemical digestion.

jejunum

Middle part of the small intestine; main site for nutrient absorption (especially sugars, amino acids, fatty acids).

ileum

Last part of the small intestine; absorbs vitamin B12, bile salts, and any remaining nutrients. Connects to the large intestine.

segmentation

contraction of circular physical action muscles in small intestine

what does the physical action of segmentation do?

• mix chyme

• promote contact with digestive juices and absorption cells

another word for the large intestine is

the colon lleocecal valve

large intestine

Last section of the digestive tract; absorbs water and electrolytes, forms and stores feces, and houses gut bacteria that aid in vitamin production (like vitamin K and some B vitamins).

what does the colon include?

ascending and descending colons, cecum, transverse colon, sigmoid colon and rectum

cecum

First pouch-like section of the large intestine; connects the ileum to the colon and helps start compaction. Attached is the appendix.

colon

Largest portion of the large intestine, divided into ascending, transverse, descending, and sigmoid regions; main site for water and electrolyte absorption, as well as bacterial fermentation.

rectum

Final section of the large intestine; stores feces until elimination.

anus

Opening at the end of the digestive tract; controlled by internal and external anal sphincters to regulate elimination of feces.

what are the five organs of digestion?

salivary glands, liver, pancreas, stomach and small intestine

substances are produced and discharged from a cell/gland/organ for a particular function in the organism

secretions

moistens food for easy passage

saliva

what are the two functions of saliva?

• protective role - softens the food

• contains enzymes - to begin carbohydrate digestion

gastric juice

A mixture of hydrochloric acid (HCl), pepsinogen, and intrinsic factor; helps break down food, kill bacteria, and begin protein digestion.

mucus

Protective coating mixed of water and proteins secreted by cells of the stomach lining; prevents the stomach from digesting itself and protects against acid damage.

whats the pH of saliva?

near pH 7, neutral

whats the pH of the stomach?

pH is lower than 7, very acidic

bile

A digestive fluid produced by the liver and stored in the gallbladder; contains bile salts that emulsify fats, making them easier to digest and absorb.

absorption

occurs mainly in the small intestine, 10ft long and there are three types

what are the three absorption techniques?

simple diffusion, facilitated diffusion, active transport

Movement of nutrients from high to low concentration directly across the cell membrane without needing carrier proteins or energy (e.g., water, small lipids).

simple diffusion

Movement of nutrients from high to low concentration with the help of a carrier protein, but no energy needed (e.g., fructose).

facilitated diffusion

Movement of nutrients against the concentration gradient (low to high) using both a carrier protein and energy (ATP) (e.g., glucose, amino acids)

active transport

Which structure increases surface area for absorption in the small intestine?

villi and microvilli