Digestion, Absorption and Transport

Question 1

What is digestion?

Answer 1

the breaking down of foods into nutrients, in preparation for absorption

Question 2

What is the GI?

Answer 2

The gastrointestinal tract - a flexible muscular tube that extends from the mouth, through the oseophagus, stomach, small intestine, large intestine and rectum to anus.

Question 3

What is the lumen?

Answer 3

the inner space within the GI tract

Question 4

Explain what happens in the mouth in digestion

Answer 4

Chewing (mastication), salivary glands help create bolus

Pushed down pharynx, a short tube.

To bypass entrance to lands, epiglottis closes off air passages

Question 5

Explain what happens in the osephagus ?

Answer 5

Sphincter muscle at each end.

During swallow, upper sphincter opens, bolus slides down to stomach.

Lower sphincter closes to avoid reflux.

Question 6

Explain what happens in the stomach

Answer 6

Stomach retains bolus in upper portion, then gradually transfers food to lower portions.

Stomach acid and muscles grunt it - creates chyme.

Gradually released through pyloric sphincter - opens into the small intestine

Question 7

What happens in the small intestine?

Answer 7

Chyme pay passes the opening from common bile duct, which drips fluids from gall bladder and pancreas

Chyme travels down through 3 segments of small intestine - duodenum, jejunum, ileum

Question 8

What happens in the large intestine (colon)?

Answer 8

Sphincter opens - ileocaecal valve (lower right side of abdomen)

Passes another opening into the appendix.

Goes left to right, then above rectum

Dietary fibre (fat, cholesterol, minerals, water) enters colon. Intestinal bacteria ferments some of it, producing water, gas, small fragments of fat that provides energy for cells of colon

Question 9

What happens at the anus/rectum?

Answer 9

As intestinal contents pass to rectum, colon withdraws water, leaving semi-solid waste

Two sphincters in anus open when you decides to defecate.

Question 10

What are the two layers of muscles in the GI tract?

Answer 10

Segmentation - inner circular muscles contract and relax. Occurs in small and large intestines (churn chyme, mixing secretions)

Peristalsis - outer longitudinal muscles contract rhythmically to move chyme forward. Contractions occur at varying rates and intestines. Stress, drugs illness interferes

Question 11

How does bulk get added to stools?

Answer 11

Dietary fibre - as it is undigested and retains water

Question 12

Explain the muscles in the stomach

Answer 12

Thickest walls and strongest muscles of GI tract

Third layer of muscles - diagonal.

Question 13

Explain the all sphincter contractions in the GI tract

Answer 13

Upper osephaegal sphincter - opens in response to swallowing

Bottom oseophaegal sphincter - prevents reflux

Pyloric sphincter - holds chyme in, prevents intestinal contents from backing up into stomach

End of small intestine - ileocaecal valve, allows small intestine to empty into large

Rectal muscle - prevents elimination until chosen

Question 14

What is an enzyme?

Answer 14

A protein that facilitates a chemical reaction

Question 15

What does saliva do?

Answer 15

Protects teeth and linings of mouth, osephagus and stomach from harmful substances

Moistens mouthful of food, contains water, salts, mucus and enzymes

Initiates digestion of carbs

Question 16

What does gastric juice do?

Answer 16

Gastric glands secret gastric juice, extremely acidic (prevents bacterial growth)

Contains water, enzymes and hydrochloride acid

Breaks down bolus into chyme

Question 17

What are the three digestive enzymes?

Answer 17

amylase (digest carbs)
Lipase (digests fats)
Protease (digest proteins)

Question 18

What does pancreatic lipase do?

Answer 18

Pancreas contributes digestive juices through ducts leading into duodenum (small intestime)

Pancreatic juice - enzymes that act on all energy nutrients (also cells of intestinal wall)

Bicarbonate (alkaline) neutralising acidic chyme

Question 19

What does bile do?

Answer 19

An emulsifier - brings fat into suspension in water, so enzymes can break it down

Liver produces bile, then concentrated and stored in gall bladder

Squirted into duodenum of small intestine when fat arrives

Question 20

How does the GI tract absorp nutrients?

Answer 20

Small intestine engulfs and absorbs the nutrient molecules

Rush of cumulating blood continuously washes underside of surface - quickly carrying away to other parts of body

Question 21

Name the anatomy of the absorptive system

Answer 21

Villi - inner surface, constant motion, recognises nutrients needed to body.
Microvilli - cells, traps small nutrients
Crypts - crevices between villi, secrete intestinal juices
Goblet cells - secrete musics

Question 22

Does the GI tract absorb nutrients all in one place?

Answer 22

No, nutrients ready for absorption are absorbed near top of GI tract, those that take longer are absorbed further down

Question 23

What happens when a nutrient molecule has crossed the cell of villus?

Answer 23

It enters the bloodstream or lymphatic system

Question 24

How does the body react to water-soluble nutrients compared to fat-soluble nutrients?

Answer 24

Water soluble - Releases directly into the liver

Fat soluble - intestinal cells assemble products of fat digestion into larger molecules. They cluster with special proteins called chlyomicrons
These are release into lymphatic system
Moves through lymph until they enter bloodstream near heart (bypasses liver initially)

Question 25

What is the circulatory systems role in the absorption of nutrients?

Answer 25

it delivers the nutrients to wherever they are needed

Question 26

Explain the vascular system

Answer 26

HEART - ARTERIES - CAPILLARIES - VEINS - HEART Blood leaves right side of heart, circulates through lungs, back into left side of heart Left side pumps blood out of aorta through arteries to all systems of body Blood circulates in capillaries, exchanges materials with cells then collects into veins Blood leaving digestion system goes by hepatic portal vein, directs blood to liver

Question 27

What does the liver do?

Answer 27

first to receive nutrients - major metabolic organ. Defends body by detoxifying harmful substances and preparing waste products for excretion

Question 28

What is the lymphatic system?

Answer 28

One way route for fluid from tissue spaces to enter the blood. Lymph circulates between cells of body, collects in theocratic duct behind heart, opens int subclavian vein - where lymph entrees blood stream Nutrients from GI tract enter lacteals (lymphatic vessels) that circulate nutrients in blood stream (but bypass liver)

Question 29

What is the gastrointestinal microbiome?

Answer 29

Defines the health of the GI tract - home to 100 trillion microbes (bacteria, viruses, fungi, Protozoa, etc - 400+ species) Persons health reflects stability, disturbance and resilience of microbiome - dramatically respond to diet

Question 30

What is homeostasis?

Answer 30

The body regulating itself to have the same conditions (temp, blood pressure etc

Question 30

What do prebiotics and probiotics do?

Answer 30

prebiotics - encourages growth the activity of bacteria (reduces risk of infection, disorder, increases bioavailability of nutrients) Probiotics - feeds live microbes that improves health of GI tracts (alleviates IBS like symptoms, ulcers, enhances immune function)

Question 31

What does the hormone gastrin do?

Answer 31

Responds to food in stomach, secreted from stomach wall - hydrochloric acid maintains an acidic pH balance

Question 32

What does the hormone secretin do?

Answer 32

responds to the acidic chyme in the small intestine, secreted from duodenal wall Bicarbonate rich juices secreted into small intestine maintain slightly alkaline pH

Question 33

What does hormone cholecystokinin do?

Answer 33

Responds to fat/protein, secreted from intestinal wall Bile emulsifies fats, maintains pH, digest fats and proteins and slow GI tract motility

Question 34

What are some factors that impact the GI tract?

Answer 34

Healthy supply of blood (inflamed without) Sleep (repairs tissue, removes waste) Activity (promotes healthy muscle tone) Stress (alters GI motility) Relaxed mealtimes (eases digestion) Balance (i.e. some fats beneficial to slow GI motility, more absorption time) Variety - some food constituents interfere with nutrient absorption Adequacy (all nutrients interdependent)

Question 35

What do the macronutrients create?

Answer 35

Carbs - glucose Fats - single fatty acids Protein - amino acids