Study sets, textbooks, questions
Upgrade to remove ads
chapter 3 notes - digestion
Terms in this set (56)
biochemically, you are what you eat.
- food and fluid taken into the body is broken down into smaller components so the body can use it.
atoms form molecules
- molecules are organized into cells
- atoms > molecules > cell > tissue > organ > organ system > organism
cells form tissues and organs
- in any living system, molecules are organized into structures the form cells, the smallest unit of life.
- cells of similar structure and function are organized into tissues. The human body contains four types of tissue: muscle, nerve, epithelial, and connective
- the tissues are organized in varying combinations into organs, which are discrete structures that perform specialized function in the body.
organs cooperate as organ systems:
1. digestive system
2. endocrine system
3. nervous system
4. cardiovascular system
5. respiratory system
1. primarily responsible for movement of nutrients into the body. In the mouth, pharynx, esophagus, stomach, intestines, pancreas, liver, and gallbladder. ingests and digests food, absorbs nutrients, eliminated unabsorbed food residue and other wastes
2. secretes hormones/ chemical messengers that help regulate food intake/absorption and function of digestive organs.
3. send nerve signals that help control control the passage of food through the digestive tract. Respond to stimuli from the external and internal environment; conducts impulses to activate muscles and glands; integrates activities other systems
4. once absorbed, nutrients are transported to individual cells via the cardiovascular system; transports blood, which carries oxygen, nutrients, and waste.
5. supplies the blood with oxygen and removes carbon dioxide
6. transports fat-soluble nutrients.
the digestive system: 2 major functions
- digestion: prices of breaking food into components small enough to be absorbed by the body
- absorption: process of taking substances into the interior of the body.
most food must be digested to be absorbed
- proteins to amino acids
- carbs to sugars
- fats to fatty acids
organs of the digestive system: gastrointestinal tract
(includes GI tract, gut, digestive tract, intestinal tract, alimentary canal)
hollow tube consisting of:
- mouth: chews food and mixes with saliva
- pharynx: swallows chewed food mixed with saliva
- esophagus: moves food into the stomach
- stomach: churns and mixes food, secretes acid and a protein-digesting enzyme
- small intestine: completes digestion, absorbs nutrients into blood and lymph.
- large intestine: absorbs water and some vitamins and minerals home to intestinal bacteria, passes waste material
- anus: opens to allow wastes to leave the body
lumen: "inside the tube"
- food within the lumen has not been absorbed and is technically still "outside" the body.
- only absorbed substances are "inside" the body (i.e. an apple seed just pass through the DI... never broken down... never entering the blood/cells
4 layers of the small intestine
1. mucosa: in direct contact with churning food, harsh digestive secretions (short life span of 2-5 days, lines the lumen, protective layer, responsible for absorption of end products of digestion
2. connective tissue: contains nerves, blood vessels, provides support, delivers nutrients to mucosa, provides nerve signals controlling secretions and muscle contractions
3. layer of smooth muscle: no voluntary control, contraction of muscles mixes food, breaks into smaller particles, propels through GI tract
4. external layers of connective tissue: support and protection
- salivary glands: produces saliva, which contains a starch-digesting enzyme
- liver: makes bile, which aids in digestion and absorption of fat
- gallbladder: stores bile and releases it into the small intestines when needed
- pancreas: releases bicarbonate to neutralize intestinal contents; produces enzymes that digest carbohydrate, protein, and fat
- Time between ingestion of food and elimination of solid waste from that food
- Time it takes food to pass the length of the GI tract
- ~24→72 hours
- shorter time = more rapid passage through GI tract
body waste, including unabsorbed food, residue, bacteria, and dead cells
- digestion inside the GI tract is assisted by digestive secretions
- mucus: vicious material produced by goblet cells; mucus moistens, lubricates, and protects the GI tract.
- enzymes: protein molecules that speed up chemical reactions; enzymes are not changed during reactions
- digestive enzymes: pepsin - comes from stomach, works in the stomach, breaks proteins into polypeptides and amino acids
- digestive hormones: help regulate digestion of nutrients and the rate that food moves through the GI tract (ex: gastrin and secretin)
= gastrin: comes form stomach mucosa, increases gastric motility and emptying
= secretin: comes from duodenal mucosa, inhibits gastric secretion and motility.
how gastrointestinal activity is regulated
- Nerve signals help regulate activity in the GI tract. The sight and smell of food stimulate nerves throughout the GI tract.
- Nerve signals cause muscle contractions that churn and propel through the gut at a rate that allows optimal absorption of nutrients.
- Nerve signals also stimulate or inhibit digestive secretions.
- Activity in the digestive tract is also regulated by hormones released into the bloodstream. Hormones that affect gastrointestinal function are produced both by cells lining the digestive tract and by a number of accessory organs.
- Hormonal signals help prepare different parts of the gut for the arrival of food and thus regulate the digestion of nutrients and the rate that food moves through the system.
digestion and absorption: the mouth
- cephalic phase: sense of smell and sight
- the mouth is the entry point for food into the digestive tract:
- chemical digestion: saliva contains salivary amylase, which helps to brea down carbohydrates and lysosomes, which help to inhibit bacterial growth in the mouth
- mechanical digestion: chewing mechanically breaks down food, increasing the surface area in contact with digestive enzymes saliva begins the chemical digestion
digestion and absorption: the pharynx
- a funnel shaped, common passageway for food and air, responsible for swallowing.
- before swallowing, the passageway to the lung is open.
- during swallowing, the bolus forces the epiglottis down to cover the passageway to thehe lungs
- after swallowing, the epiglottis returns to its original position, reopening the airway to the lungs.
- food lodged in the passageway to the lungs can block to flow of air
- hemlock maneuver forces air out of the lungs, blowing lodged food out of the air passageway.
digestion and absorption: the esophagus
- tube passing through the diaphragm, connecting the pharynx to the stomach
- peristalsi = through the GI tract
- circular muscle contract, pushing the bolus down.
- longitudinal muscles contract, shorting the passageway ahead of the bolus
- the rhythmic contractions of peristalsis propel food down the esophagus
- when a wave of peristaltic contraction reaches the stomach, it causes the sphincter to relax, allowing the bolus to enter the stomach
digestion and absorption: the stomach
- expanded portion of the GI
- temporary storage
- bolus is mashed, mixed with highly acidic stomach secretions, forming chyme (semiliquid food mass)
- very little absorption in the stomach
- walls = thicker, stronger muscles with powerful contraction to mix food
- stomach has three muscle layers: longitudinal, circular, and diagonal
- lining of the stomach = covered in gastric pits
digestion and absorption: the stomach: gastric glands
- inside the gastric pits
- gastric glands are made up of cells the produce components of gastric juice
- gastric juice = water, mucus, hydrochloric acid, pepsinogen
- acidity stops salivary amylase (no CHO digestion in the stomach)
- parietal cels = hydrochloric acid and intrinsic factor (B12)
- chief cells = pepsinogen, activated to pepsin by Hal
digestion and absorption: the stomach: regulation of stomach acidity
signals from nerves and hormones regulate:
- how much the stomach churns
- how much gastric juice is released
- how fast materials empties out of the stomach
signals come from:
1. Before food enters the stomach, the though, smell, sight, or taste of food causes the brain to send nerve signals that stimulate gastric secretions and increase stomach motility, thereby preparing the stomach to receive food.
2. Food entering the stomach increases the rate of gastric secretion and motility by stimulating local nerves, sending signals to the brain, and stimulating the secretion of gastrin
3. Food leaving the stomach and entering the small intestine distends the intestine, triggering hormonal and nervous signals that decrease stomach motility and slow the secretion of gastric juices.
- small intestine
digestion and absorption: stomach:
- nutritional components of meal
- high fat meal stays in the stomach the longest
- primarily protein meal leaves more quickly
- mostly carbohydrate meal leaves the fastest
digestion and absorption: stomach: hunger, satiety, and meal composition
- breakfast choices affect when you become hungry for lunch
- toast and coffee leave you more quickly than larger meals with more protein an more fat
- bacon, eggs, and buttered toast leave more slowly keeping you fuller longer
digestion and absorption: the small intestine
main site of digestion of food and absorption of nutrients
- narrow tube ~ 20 ft., 3 sections: duodenum (12 in), jejunum (8 ft.), ileum (11 ft.).
the small intestine: structure maximizes function
- length increases the area of absorptive surface
- 3 other features increase absorptive surface area: large circular foods, villi line the entire surface of the small intestine (finger-like projections of the lining of the small intestine participate in digestion and absorption of nutrients), microvilli cover mucosal cells on each villi (aka brush border, within each villus= blood vessel and lymph vessel [lacteal])
- together these features provide a surface area about the size of a tennis court
- nutrients still cross the mucosal cell layer to reach the bloodstream or lymphatic system for delivery to the tissue of the body
- segmentation: alternating contraction and relaxation of segments of the small intestine move food forward and backward - mixing it rather than propelling it forward. rhythmic local constrictions. mixing chyme with digestive secretions
small intestine: gallbladder, liver, and pancreas
- pancreas secretes digestive enzymes ad bicarbonate ions into the small intestine during digestion
- bicarbonate ion neutralize acidic chyme
- small intestine is a neutral environment so enzymes can function.
- pancreatic amylase: continues breaking down starch that was started in mouth by salivary amylase
- pancreatic protease: typist and chymotrypsin; breaks protein into shorter and shorter chains of amino acids.
- lipase: breaks triglycerides into fatty acids
small intestine: gall bladder
- stores/secretes bile which is produced by the liver
- bile = necessary for fat digestion and absorption
- bile + digested fats form small droplets that facilitate absorption of fat into mucosal cells; products of fat digestion are incorporated into transport particles and absorbed into lymph before passing into blood
small intestine: digestion and absorption
- the primary site for absorption of water, vitamins, minerals, and products of cholesterol, protein, and fat digestion
- to be absorbed, nutrients must pass form the lumen of GI tract into mucosal cells lining the tract then into blood or lymph.
small intestine: 4 mechanisms for absorption
- include simple diffusion, osmosis, facilitated diffusion, and active transport
- digestion = nutrient breakdown
- cholesterol nutrient breakdown:
1. pancreatic amylase digests starch to double sugars and short glucose chains
2. fiber, which cannot be digested by human enzymes, passes to the large intestine
3. enzymes in the microvilli digest double sugars into single sugars which are absorbed into the blood. Starch digestion begins in the mouth (salivary amylase) but most digestion/absorption occurs in the small intestine.
protein nutrient breakdown (in the small intestines)
4. pancreatic proteases, along with proteases in the microvilli digest polypeptides into amino acids, dipeptides, and tripeptides
5. amino acids, dipeptides, and tripeptides are absorbed into the mucosal cells where they are digested into single amino acids, which pass into the blood. proteins are broken into smaller polypeptides in the stomach, but most digestion/absorption occurs in the small intestine.
fat nutrient breakdown (in the small intestines)
6. bile helps divide large fat globules. Pancreatic lipases digest triglycerides
7. short chain fatty acids are absorbed into the mucosal cells and then pass directly into the blood
8. long-chain fatty acids and other lipids combine with bile to form small droplets that aid the absorption of fatty acids and other fat-soluble substances into the mucosal cell
9. absorbed lipids are incorporated into transport particles that pass into the lymph. They enter the blood without first passing through the liver
review of hormonal control
- hormones secreted by mucosa of the duodenum
- help regulate digestion of nutrients and the rate that food moves through the GI system,
- secretin: comes from the duodenal mucosa, inhibits gastric secretion and motility increases output of water and bicarbonate form the pancreas; increases bile output from the liver
- cholecystokinin (CCK) - comes from the duodenal mucosa; stimulates contraction of the gallbladder to expel bile; increases output of enzyme-rich pancreatic juice
digestion and absorption: the large intestine
- includes the colon and rectum
- some absorption: water and some vitamin and minerals
- intestinal microflora produced here (can act on unabsorbed portion of food [fiber], may synthesize some B vitamins, Vitamin K)
- water, nutrients, and fecal material may send 24-72 hours in the large intestine.
- slower peristalsis in the large intestine
- primary function: feces = prepares undigested, unabsorbed matter, dead cells, secretions from GI, water (affected by water intake), bacteria (makes up more than half of the weight) for excretion.
- Substances that pass undigested into the colon and serve as a food supply for bacteria that stimulates growth and/or activity of certain types of bacteria
- Naturally found in onions, bananas, garlic, and artichokes
- Fermentable fibers that feed bacteria in large intestine
- Sold as dietary supplements
- Live bacteria you can consume; will live temporarily in colon and confer health benefits
- Most yogurts contain active cultures of beneficial bacteria
- Lactobacillus and bifidobacterium
- Immune function, colon cell (growth/production), inhibit harmful bacteria growth, transit time
- When living beneficial bacteria are consumed in adequate amounts, they live temporarily in the colon, where they inhibit the growth of harmful bacteria and confer other health benefits on the host.
- The bacteria must be consumed frequently because they are flushed out in the feces.
Health microflora have been shown to:
- Reduce duration of diarrhea associated with antibiotics
- Reduce duration of diarrhea resulting from intestinal infections
- May relieve constipation, reduce allergy symptoms, modify risk of inflammatory bowel disease, and colon cancer
health of the GI tract is essential to overall health
digestion and health: gut
- take sin nutrients
- acts as defense against invasion
- food allergies have origins in the GI tract
- most GI problems = minor and no impact long term
- some digestive problems = serious consequences.
immune functions of the gastrointestinal tract
- the GI tract plays an important role in protecting the body from infection.
- acid in the stomach [HCl] kills most bacteria
- mucosa [thick protective layer] = barrier - limits the absorption of toxins and disease causing organisms
immune functions of the gastrointestinal tract: immune system activity
Some of the immune system are present in the GI tract:
- white blood cell:
-- phagocytes - first type of cell to come to body's defense. Can engulf and destroy invading substances
-- lymphocytes - very specific, produce and secrete protein molecules (antibodies)
- Peyer's patches
-- made up of the immune system tissue and are embedded through the mucosa of small intestines
-- Peyer's patches contain cells that participate in the immune system;s effort to prevent harmful organisms or materials present in the GI tract from making us ill.
causes and consequences of digestive problems:
- allergic reaction = response of immune system,
- 1st time eaten and protein consumed intact = immune system is stimulated
- 2nd time, immune system recognizes it and mounts and attack (allergic reaction)
- most common food allergens must be indicated on labels
- seafood, peanuts, tree nuts, fish, soy, wheat, milk, eggs
causes and consequences of digestive problems: celiac disease
- gluten triggers immune system response
- gluten = protein in wheat, barley, and rye
- destroys villi in the small intestine
- untreated = intestinal damage, reduced nutrient absorption, malnutrition, weight loss, anemia, osteoporosis, intestinal cancer
- inherited condition (1/141): confirmed with a blood test
- should you be gluten free?
-- for weight loss? gluten free foods are not any lower in kcal but eliminating gluten foods (most cereal, bread, pasta, cakes, and cookies) may help cut calories
-- no nutritional benefit unless sensitive to gluten but carefully choosing everything you put in your mouth (to avoid gluten foods) will force you to plan your diet and may improve nutrient density.
causes and consequences of digestive problems: heartburn, gasatroesophageal reflux disease (GERD)
- causes: stomach acid leaking into esophagus
- irritates the lining of the esophagus
- treatment/management: reduce meal size, avoid high fat foods, consume liquids between rather than with meals, remain upright after eating, take antacids and other medications.
causes and consequences of digestive problems: antacids - getting the drug facts
- over the counter heartburn and remedies often contain nutrients
- neutralize stomach acids, reduces absorption of nutrients(esp. B12, Fe, Ca)
- Both Ca and Mg are typically low in our diets, so they can be a welcome supplement but
--- Ca = 320 mg; 32% of Daily Value
--- Mg = 69 mg; 17% of Daily Value
- Alka Seltzer = 520 mg of sodium, 24% of daily value
- aluminum = often found in antacids bind
- phosphorus and may cause constipation
causes and consequences of digestive enzymes: ulcers
- lesions in the wall of the stomach or GI tract.
- infection of the stomach by H.pylori
- H. pylori causes inflammation and ulcers, is associated with cancer of the stomach.
- Rx = antibiotics, acid suppression for healing
- ulcer = cured
- seem through protective mucus layer an adhere to mucosal cells then neutralize acid immediately around them causing inflammation, immune response, tissue damage
alternative feeding methods
- if an individual cannot take adequate food or fluid by mouth: internal or tube feeding.
- delivered by a narrow tube passed through nasal passages or directly into stomach or intestine so that a liquid diet can be delivered for digestion and absorption
- if a person;s GI tract is not functional nutrition. Delivers a solution providing all of the essential nutrients directly into the bloodstream through a large vein - upper arm or chest.
- pregnancy: early in pregnancy, hormonal changes cause nausea, vomiting referred to as morning sickness. Later, the uterus and muscle-relaxing hormones contribute to heartburn and constipation.
- infants: young infants have no teeth and can't consume solid food. They have digestive enzymes that are well suited to the digestion of the lipids, proteins, and carbohydrate in human milk
- Children/adolescents: young children don't have all of their teeth, so to avoid choking they need a diet that consists of soft foods. Most children have a full set of teeth by age 3.
- Older adults: In older adults, the sense of smell and taste are often diminished. Dry mouth is common and can make swallowing difficult, decrease the taste of food, and promote tooth decay.
After nutrients are absorbed into mucosal cells of the intestine, they enter the blood circulation by either:
1. hepatic portal circulation: water soluble pathway
- Part of the cardiovascular system (heart/blood vessels)
- Amino acids, simple sugars, water-soluble products of fat digestion = absorbed into capillaries
- Collects nutrient-laden blood from the digestive organs and delivers it to the liver
- Most nutrients go directly to the liver
- In small intestine, water-soluble molecules, amino acids, sugars, water-soluble vitamins, water-soluble products from fat digestion cross mucosal cells of villi and enter capillaries
- Capillaries merge to form venues
- Venules merge to larger veins an d eventually the hepatic portal vein. Transport blood directly from the GI tract to the liver
- Carries blood form the stomach to intestines to liver.
- Nutrients absorbed directly into the blood reach liver via hepatic portal vein
After nutrients are absorbed into mucosal cells of the intestine, they enter the blood circulation by either:
2. lymphatic system: fat-soluble pathway
- Transports non water-soluble products of fat digestion, taken into lacteals (small vessels of lymphatic system) before entering the blood
- System of vessels, organs, and tissues that drain excess fluid from spaces between cells
- Contribute to immune function
the cardiovascular system
- Blood carries nutrients and oxygen to the cells of all the organs and tissues of the body and removes waste products form these same cells
1. Oxygen poor blood that reaches the heart form the rest of the body is pumped through the pulmonary arteries to the capillaries of the lungs
2. In the capillaries of the lungs, oxygen from inhaled air is picked up by the blood, and carbon dioxide is released into the lungs and exhaled.
3. Oxygen rich blood returns to the heart from the lungs via pulmonary veins
4. Oxygen rich blood is pumped out of heart into the arteries that lead to the rest of the body
5. In capillaries, nutrients and oxygen move from the blood to the body's tissues and carbon dioxide and other waste products move from the tissues to the blood to be carried away.
6. Oxygen poor blood returns to the heart via veins
delivering nutrients to the body: function of the liver
- liver = gatekeeper
- processes absorbed nutrients before circulating.
- depends on the body's needs:
-- synthesis and breakdown of amino acids, proteins, and fats
-- changed - conversion of breakdown products for safe excretion by kidneys; detoxification
-- allowed to pass to cells - participates in controlling blood levels of nutrients as glucose.
the roles of the lymphatic system
- Important for fluid balance and immune function and absorption of lipids
- Important for absorption because fat-soluble materials: triglycerides, cholesterol, fat-soluble vitamins are incorporated into particles that are too large to enter intestinal capillaries
- Substance absorbed via lymphatic system do not pass through liver before entering blood circulation
how nutrients enter body cells
- what happens once macronutrients are absorbed?
- cell = final destination of absorbed nutrients
- protein, cholesterol, and fat can be:
-- broken down to provide energy
-- used to synthesize structural or regulatory molecules
-- transformed into energy storage molecules
-- each absorbed nutrient plays a unique role in metabolism
anabolic and catabolic pathways
- Depending on the body's needs, the glucose, fatty acids, and amino acids absorbed frm the diet are broken down to provide energy, used to synthesize essential structural or regulatory molecules or transformed into energy-storage molecules.
- Metabolic pathways: series of reactions needed to transform food into a final product that can be used by the body (involves enzymes and coenzymes)
- Catabolic pathways: release energy trapped in chemical bonds
- Energy from catabolic reactions is converted into ATP
- ATP is the energy currency of the cell
- Adenosine Triphosphate (ATP):
•ATP consists of an adenosine molecule attached to 3 phosphate groups. The bonds between the phosphate groups are very high in energy, which is released when bonds are broken.
•Nutrients delivered to body cells can be used either in catabolic reactions to produce ATP or as raw materials in anabolic reactions that use ATP to synthesize molecules needed by the body.
synthesizing new molecules
- Metabolizing nutrients: cellular respiration
1. In the presence of oxygen, glucose, fatty acids, and amino acids can be metabolized to produce acetyl-CoA
2. Acetyl CoA is broken down by the citric acid cycle to yield carbon dioxide (CO2) and high energy electrons.
3. Electrons are shuttled to the electron transport chain where their energy is used to convert ADP to ATP. They eventually combine with oxygen and hydrogen to form water.
elimination of metabolic wastes
substances in the food that cannot be absorbed are eliminated in the feces
the respiratory system and skin
- Nutrients that are absorbed form the digestive system and oxygen take in by the respiratory system are distributed to all the cells in the body by the cardiovascular system.
- Wastes generated from nutrient metabolism, called metabolic wastes [ ex: CO2, Nitrogen, Water] are eliminated from the body by the integumentary, the urinary, and the respiratory systems.
- Part of the urinary system
- Primary means of excreting water, metabolic waste products, excess minerals
- Nephron/glomeruli filter blood
• Reabsorption of needed substances
• Excretion in urine of water and unneeded substances
other body organ system
- Respiratory system: carbon dioxide is exhaled from the lungs into the environment
- Integumentary system water and minerals
- Body cells: red blood cells transport carbon dioxide form the body cells to the lungs
- Urinary system: nitrogen-containing metabolic waste products (urine)
• In the kidneys, water and small molecules are filtered out of the blood. Some filtered substances are reabsorbed into the blood, and those that are not are excreted in urine.
- Anus: unabsorbed waste is excreted as feces
What would be considered a gonadotropic hormone that is secreted from the adenohypophysis of the pituitary gland?
Where do hair cells get their color?
What is the term for a muscles that have opposite actions?
What is the most proximal block of the brachial plexus?
Recommended textbook explanations
Hole's Essentials of Human Anatomy & Physiology
David N. Shier, Jackie L. Butler, Ricki Lewis
Introduction to Anatomy and Physiology
Michelle Provost-Craig, Susan J. Hall, William C. Rose
Essentials of Human Anatomy and Physiology
Elaine N. Marieb, Suzanne M. Keller
Human Anatomy & Physiology
Elaine N. Marieb, Katja Hoehn
Sets found in the same folder
nutrition: chapter 1 - food for health
chapter 7 notes - energy balance and weight manage…
chapter 12 notes - trace elements
chapter 7 study questions
Sets with similar terms
Nutrition CH.3 Digestion
Visualizing nutrition chapter 3
Chapter 3: Digestion
Other sets by this creator
ICU exam 2
2 - cells, disease, and cell biology
1 - Normal Cell Structure and Function
lecture 10 - integumentary system
Other Quizlet sets
CTR Exam-Data Collection (Abstracting/Coding)-55%
Unit III - History
ANATOMY AND PHYSIOLOGY
Every year dozens of elderly people are found dead in their unheated apartments and listed as victims of hypothermia. What is hypothermia, and how does it kill? Why are the elderly more susceptible to hypothermia than the young?
ANATOMY AND PHYSIOLOGY
Which is not a component of sweat? a. Water, b. Sodium chloride, c. Sebum, d. Ammonia, e. Vitamin D.
ANATOMY AND PHYSIOLOGY
What type of reflex can protect the foot when a painful stimulus is sensed? a. stretch reflex b. gag reflex c. withdrawal reflex d. corneal reflex
ANATOMY AND PHYSIOLOGY
How many chromosomes does a human sex cell have?