Chapter 3: Digestion, Absorption and Metabolism Flashcards
define: metabolism
- sum of all chemical reactions in the body
- Metabolism of nutrients: cellular respiration; captures all the energy in sugars, triglycerides and amino acids into ATP
digestion
- describe 2 types
- Process that separates nutrients in food and breaks larger molecules into smaller ones
- Mechanical digestion: teeth chewing, stomach churning
- Chemical digestion: uses enzymes to alter the chemical structure of nutrients and reduces them to their building blocks
enzymes
Speed up reactions and provides location for chemical reactions to occur
hydrolysis
The input of water breaks down the molecule
condensation
Combines molecules by liberating a water molecule
hormones
Chemical messengers required for many physiological processes
sphincters
Circular muscles that contract to close openings and relaxes to open them
What are some things that impact digestive transit times. What is the average digestive time?
- Age, activity levels, diet, gender, medication, infection, emotional state
- ~2 days for food to pass through the entire tract
List all the layers of the digestive tract wall (5)
- lumen
- mucosa
- submucosa
- muscularis
- serosa
describe the following layer of the digestive tract wall: lumen and mucosa
- lumen: inner cavity of the small intestine tube
- mucosa: layer that secretes mucus, keeps digestive tract moist, and protects it from infection, plays a role in absorption
describe the following layer of the digestive tract wall: submucosa
- Submucosa: connects mucosa to the more superficial muscularis layer, blood vessels, lymphatic vessels, and nerves are found here
describe the following layer of the digestive tract wall: muscularis
- Muscularis: composed of smooth muscles that are autonomic; pushes food forward and helps it mix with digestive secretions
describe the following layer of the digestive tract wall: serosa
- Serosa: outermost layer that consists of a layer of connective tissue; helps to reduce friction with organs or helps anchor tract in place
explain the enteric nervous system
- Various nerves and nerve plexuses that create a system
- 500 million neurons arranged in groupings called a nerve plexeus
- all in the lining of the gastrointestinal system
mouth
- chemical digestion
- manual digestion
- define bolus
- chem. digestion: saliva - from 3 main glands (parotid, submandibular, sublingual)
- 2 enzymes: salivary amylase becomes amylose (starch); lingual lipase (lipids)
- manual digestion: tongue and teeth
- bolus: uniform cohesive structure created through chewing and saliva
pharynx
- role
- define: epiglottis
- Passageway for both food and air
- Epiglottis; flap of tissue that covers trachea opening when we swallow so food goes down the esophagus
esophagus
- role
- Passageway for food from pharynx to stomach; Food enters stomach with the lower esophageal sphincter opens
how does food move through the digestive tract?
- Peristalsis: smooth muscle contractions to move bolus further through the digestion tract
- Gravity helps too
- NOT segmentation
stomach
- how long does food remain in the stomach
- what is chemically digested here
- mechanical digestion
- types of muscle (3)
- define chyme
- pyloric sphincter
- crypts
- 4-5 hours before it empties
- chemical digestion of protein begins; Partial absorption of water and amino acids occur here
- mechanical digestion: diagonal smooth muscle allows for churning to facilitate chemical digestion
- types of muscle: longitudinal, circular, diagonal
- chyme: bolus turns into semiliquid substance
- pyloric sphincter: opens to let chyme enter the small intestine
- crypts: invaginations in the stomach that increase surface area, allowing more stomach cells to be involved in digestion
gastric juices (4)
- Mucus: lubrication and a medium for chemical reactions to occur in; lines the stomach’s inner wall protecting it from stomach acid and juices
- Hydrochloric acid (HCl): unravels proteins, exposing sites where enzymes can further break them down; plays a role in activating pepsin
- Pepsinogen: proenzyme; HCl converts pepsinogen into pepsin; Pepsin: breaks down amino acid chains into smaller chains
- Gastric lipase: breaks down lipids
small intestine
- describe the structure
- villi
- microvilli
- enterocytes
- capillary beds
- lacteal
- peristalsis and segmentation
structure
- 6m in length
- duodenum, jejunum, ileum
- large folds that face the lumen (increase SA and slow the passage of food along its path)
- villi
- microvilli: tiny projections in the enterocytes; make up the brush border; where digestive enzymes are stored (lactase, sucrase, maltase)
- enterocytes: small intestine cells that line the peaks and valleys of the villus surface
- Capillary beds exist within the submucosa of the villi; all nutrients are absorbed here except for large lipids and fat soluble vitamins
- Lacteal: lymphatic vessels that absorb large lipids and fat soluble vitamins; enter the blood by draining through the thoracic duct
- segmentation: movement that breaks material into smaller components while mixing it with digestive juices
absorption in the small intestine
- osmosis
- simple diffusion
- facilitated diffusion
- active transportation
- Osmosis: movement of water in response to concentration differences
- Simple diffusion: fatty acids and fat soluble vitamins; absorbed along the spaces between phospholipids in the enterocyte cell membrane; do not require a transporter
- Facilitated diffusion: a protein transporter acts as tunnels to allow material to pass from an area of high concentration to low concentration; Certain sugars require this (fructose)
- Active transportation: glucose and amino acids move from an area of low concentration to high concentration; requires energy and a protein transporter to move against the concentration grain
List the accessory organs
- pancreas
- gallbladder
- liver
pancreas
- 2 functions
- list the enzymes (4)
- Regulates blood glucose using hormones (endocrine function)
- Insulin: when glucose rises tells body to store sugar
- Glucagon: tells liver to release stored sugar when glucose drops
- Releases pancreatic juices (exocrine function) that contain digestive enzymes into the small intestine
- Protease: protein digestion
- Lipase: lipid digestion
- Amylase: carbohydrate digestion
- Bicarbonate: buffer that reduces acidity of chyme, increasing the effectiveness of digestion in small intestine
Liver and gallbladder
- emulsification
- micelle
- The liver produces bile which promotes lipid digestion
- Gallbladder stores bile; secretes it when needed
- Emulsification: suspension of lipids to be easily transported within the small intestine’s lumen
- Micelle: grouped lipids within a ring of bile salts
summarize the chemical digestion that occurs in the small intestine for
- carbs
- proteins
- lipids
- see google doc
large intestine
- list the parts
- mechanical digestion
- rectum
- 1.5m in length but with a larger diameter than the small i
- ileum from small intestine
- -> cecum: first part of the large intetine
- appendix: hangs from the cecum; plays a role in microbiome composition
- cecum –> ascending, transverse, descending, and sigmoid colons (collectively known as the colon)
- mechanical digestion: peristalsis and segmentation
- rectum: where feces is held until it is ready to be excreted
microbiome
- define
- microbiota
- explain role
- genetic material of the non human organisms found in our body
- microbiota: all the non-human organisms found in our body
- Play a role in vitamin synthesis, energy harvesting, health/disease, appetite
- Fermentation of unused carbohydrates and production of short-chain fatty acids (energy harvesting)
- Promote healthy population of intesntinal cells
- Prevent allergies
- Prevent IBD
- Suppress growth of harmful bacteria
probiotics
- define
- found in?
- impact
- Cultures of living organisms, typically bacteria
- Found in: some supplements, yogurt, kombucha
- Need to be taken for a month+ for effects to be evident: Antibiotic associated diarrhea, traveller’s diarrhea, acute respiratory infections, infant colic, type of colitis; Ongoing research on effect of IBS, obesity, cardiovascular disease, cancer
prebiotics
- Act as food for the microbiome and support its function
- Medium length carbs that our gut microbes ferment
- Sources: asparagus, beet sugar, onion, wheat, honey, banana, barley, tomato, rye, soymilk, peas, beans, and seaweed
ulcers
- what
- how
- 2 types
- Open sores that can occur along the lining of a body structure
- Caused by a weakening of mucosal layer of the digestive tract wall
- Canker sores: ulcer in the mouth; caused by biting the cheek, eating a lot of acidic food, burning the inside of the mouth
- Peptic ulcers: occur in the esophagus, stomach, or small intestine; related to H. pylori bacteria infection
Gastroesophageal reflux disease aka acid reflux
- what
- treatments
- what can it lead to
- Weakening of the lower esophageal sphincter that allows stomach acid to spill upward into the esophagus
- Weight loss improves acid levels and symptoms of acid reflux
- Elevating the head of the bed reduces reflux
- Decreasing tobacco, alcohol, chocolate, large meals, spicy foods, high fat meals reduce symptoms
- Can lead to the narrowing of the esophagus and promote esophageal ulcers
Irritable bowel syndrome (IBS)
- Illness that impacts the large intestine, symptoms include abdominal pain, bloating, cramping, diarrhea, constipation, flatulence
- Cause: muscular and nervous system impairment, inflammation, infection, gender (being a woman), family history can all increase risk
- Changes in the microbiota may promote and aggravate symptoms
Diverticulitis
- define
- diverticula
- bleeding diverticula
- what can increase your risk to get diverticulitis
- diverticula: weakened walls of the large intestine form outpouching
- Inflamed diverticula= diverticulitis
- Bleeding diverticula= diverticulosis
- Age, obesity, smoking, physical inactivity, low fibre high animal fat diet can increase risk
gallstones
- define
- how can it occur
- risk factors
- Hardened bile deposits that accumulate in the gallbladder or bile duct; can cause pain when fat is consumed and the gallbladder contracts to release bile
- Occur due to an overabundance of cholesterol
- Risk factors: gender (women), estrogen-containing contraceptives, obesity, rapid weight loss, physical inactivity
Colorectal cancer
- Physical activity and obesity increase risk
- Diets high in red and processed meats increase risk
- Diets high in vegetables, fruits, and fibre decrease risk
constipation
- Difficult to pass or less frequent bowel movements
- Increases risk for hemorrhoids
- Stools are hard and dry, can be painful to excrete
- Risk factors: age, female sex, genetics, physical inactivity, IBS, use of certain medications
- Diets low in fruits, vegetables and water increase risk
diarrhea
- When matter passes too quickly through large intestine
- Stools are loose and have a liquid like consistency
- Typically due to bacterial and viral infections; body tries to pass bacteria or viruses out of body quickly
Food allergies
Immune system reacts to non harmful antigens called allergens
- First exposure: begins the process with the production of antibodies
- Second: allergens bind to antibodies and cause release of histamine
- Symptoms: redness, swelling, hives, tingling on tongue/lips, difficulty breathing, decreased blood pressure
- Extreme cases lead to anaphylaxis
celiac disease
- Inherited disease
- Gluten protein triggers an immune response which damages villi
- Symptoms and complications: abdominal pain, diarrhea, fatigue, malnutrition, weight loss, anemia, osteoporosis, intestinal cancer
- Treatment: avoid gluten all together
liver
- Nutrients absorbed in the small intestine enter hepatic portal vein that lead to the liver
- Acts as a gatekeeper for nutrients: use them, store them, send them to the rest of the body, detoxify them
- Can store glucose → glycogen
- Whatever isn’t used here is sent to the rest of the body through the bloodstream
lymphatic system
- what
- 3 functions
- Network of lymph vessels that contain infection fighting cells
3 functions - Clears tissues of excess fluid
Immune response is launched when an antigen is detected in the lymph - Large lipids and water insoluble materials are absorbed into the lymph
- Lymph then drains into CVS cvs via the thoracic duct
anabolism
- Smaller molecules coming together to make large ones
- Require added energy
- Example: protein synthesis
catabolism
- Large molecules being broken down into smaller ones
- Process gives off energy
cellular respiration
- metabolic pathway
- location it occurs
- formula
- metabolic pathway
- catabolic process that leads to the capture of released energy within ATP
- occurs in the mitochondria
- see doc
- Metabolic pathway: steps that create ATP
glucose metabolism
- see google doc
lipid metabolism
- see google doc
ketogenesis
- Occurs when diet is high in fat and very low in carbohydrates
- Citric acid cycle requires carbohydrates
- On a low carb diet, fatty acids cannot enter citric acid cycle, instead form ketones
amino acid metabolism
- see google doc
Non energy uses of sugars lipids and amino acids
Most of the excess is stored as lipid in our fat tissue
Synthesizing new molecules
- Energy yielding nutrients that are not used for energy are used to form other molecules (requires ATP)
Glucose:
- Forms glycogen
- Small energy reserve in the muscle/liver
- Forms fatty acids, stored in fat tissue
Fatty acids:
- Stored in fat tissue
- May also be used to help form cell membranes, regulatory molecules
Amino acids:
- Used to synthesize body proteins
- May also be converted into fatty acids and stored in fat tissue