Digestions Notes Flashcards
The body needs nutrients for?
- Growth
- Maintenance
- Repair
Nutrients include:
- Carbohydrates
- Proteins
- Fats
- Vitamins
- Minerals
- Water
Digestion is:
The process of breaking food down into nutrients
Digestion can be
Mechanical or chemical
1. Mechanical- chewing
2. Chemical- stomach acid
The primary organs of the digestive system are arrange along a tube called?
Alimentary canal
What is the gastrointestinal tract composed of
Organs and structures which food passes
Where does digestions start
The mouth
Where does digestion end?
The anus
Accessory glands ____ the process of digestion
Assist
Accessory organs and glands
- Salivary glands- produce enzymes, soften food
- Teeth
- Tongue
- Pancreas- maintains blood sugar, produces insulin
- Liver- removes toxins
- Gallbladder- produces bile that breaks down fats
Functions of the digestive system
- Ingestion
- Propulsion
- Mechanical digestion
- Chemical digestion
- Absorption
- Defication
Ingestion is what kind of process
Voluntary
Propulsion
The forceful movement of food from one organ to the next
Peristalsis
Alternating waves of contraction and relaxation that push food along GI tract
How many layers of muscle does the alimentary canal have
2
Reduces the diameter of the alimentary canal
Circular layer
Shortens the sections of the alimentary canal
Longitudinal muscles
Examples of mechanical digestion
- Tongue mixes food
- Teeth tear food
- Churning of food in stomach
- Segmentation in small and large intestines to mix food
When does chemical digestion occur
When large food molecules are broken down into their building blocks
What breaks down food into their building blocks
Enzymes
Enzymes are protiens that ______ chemical reactions
Speed up
What is required for hydrolysis reactions
Water
Absorption
When nutrients travel from the GI tract into the blood stream in the Small intestine
What carries nutrients to cells throughout the body
Bloodstream
The elimination of solid waste from the body
Deification
Un digested/unabsorbed food, water, bacteria
Feces
Digestive activity
- Mechanoreceptors detect stretching of organ wall
- Chemoreceptors detect factors such as solute concentration, pH and the presence of substrates and end products
- The brainstem coordinates responses that activate or inhabit glands and muscles of the digestive system
What detects factors such as solute concentration, pH, and the presence if substrates and end products
Chemoreceptors
What coordinates responses that activate or inhibit glands and muscles of the digestive system
Brainstem
How is mechanical digestion accomplished in the mouth
Teeth, tongue, and salivary glands
What do salivary glands produce to begin chemical digestion
Enzymes
Anatomy of the mouth
- oral cavity
- lined with mucus membrane
- lips protect anterior opening
- cheeks form lateral walls
- hard and soft palate form roof
- tongue occupies the floor of the mouth
- tonsils located at the back of the mouth
What is another name for chewing
Mastication
What is the ball of digested food called
Bolus
Chemical digestion in the mouth begins with
Saliva
What does the enzymes salivary amylase do
-Begins digestion of carbohydrates
-polysaccharides (starch and glycogen) are broken down into disaccharides
3 salivary glands
- parotid
-submandibular
-sublingual
Saliva contains
- water
- salivary amylase
-mucus
-antibacterial substances
Amylase
Break down carbs
Lipase
Break down lipids
Swallowing is also called
Deglutition
Swallowing starts as voluntary and then
Involuntary reflexes take over
Pharynx
- area behind the nose and mouth
- oropharynx and laryngopharynx common passageway for food, air, and liquids
Food plus passes through the pharynx to the
Esophagus, stomach, small intestine, large intestine
The esophagus extends to the
-stomach
-25cm long
-posterior to the trachea (why we can preform a tracheotomy)
- passes through the diaphragm
How does the esophagus conduct food
Through peristalsis
The stomach
- j shaped organ
- expands from the inferior end of the esophagus
- secretes enzymes that digest protiens
-muscle contractions contribute to mechanical digestion
Gross anatomy of stomach
- 25mc long
-food enters through cardioesophagial sphincter
-pyloric sphincter is located at the terminal end just before the duodenum
-upper left quadrant of abdominal cavity
Muscle layers of stomach
-oblique muscle, circular and longitudinal layers
- three layers allow for churning of food
Mucus membrane
- lines stomach
- secretes protective mucus
- gastric pits secrete gastric juice
Gastric juice
- enzymes such as pepsinogen (secreted by chief cells) break down proteins
-allows b12 to be absorbed
-hydrochloride acid activates pepsinogen and transforms it into intestine
-Hormones such as gastric are stimulated by food and low pH and trigger the secretion of gastric juice
Major functions of the stomach
-stores food
-initiates protein digestion
- prepares food into a thick semi liquid called chyme
-gradually releases chyme into the small intestine
The small intestine
-the body’s major digestive organ
- digestion of all nutrients is completed and almost all absorption occurs in the small intestine
- extends from the stomach to the large intestine
- longest part of GI track (3-4m long, 2.5 cm in diameter)
- 3 subdivisions (duodenum, jejunum, and ileum)
The broad fan shaped fold of tissue that anchors the small intestine to the posterior abdominal wall
Mesentery
What branches through the mesentery
Blood vessels, nerves, and lymphatic vessels
What muscle lines the esophagus
Smooth muscle
Structural modifications of small intestine increase
Surface area
Structural modifications of the SI
- plicae circulares are deep circular folds of the intestinal lining
-villi are finger like projections of the mucosa
-microvilli are tiny projections of the plasma membrane of epithelial cells
The first portion of the small intestine
The duodenum
What process occurs in the duodenum
Enzymes from the intestinal cells and pancreas, and bile from the liver complete the chemical breakdown of food
Intestinal juice
-secreted by glands at the base of the villi
- composed mostly of water and alkaline mucus
- neutralizes the acidic shame from the stomach
- intestinal glands secrete 1-2 liters of intestinal juice per-day
Brush boarder enzymes
-bound to the surface of the microvilli
-complete the final stages of carbohydrate and protien digestion
-microvilli creates a fuzzy appearance
The liver
- the largest internal organ
-primary function is to secrete bile - bile is a basic solution that digests fats
Where is bile stored and released
-stored in the gallbladder
-rereleased to the duodenum through the bile duct
-controlled by the hormones CCK and secretin
Bile is not
And enzyme
emulsification
- the process of breaking down fat droplets into smaller pieces
-aids the digestion of fats by pancreatic lipase by increasing surface area
Pancreatic juice
- enters the duodenum through the pancreatic duct
- contains enzymes that break down all types of nutrients
-contains bicarbonate which maintains a basic pH of 8
Pancreatic enzymes
Proteases
- trypsin, chymotryspin, carboxypeptidase
- complete digestion of protiens
Pancreatic amylase
- works with brush border to complete the digestion of carbs
Lipases
- important fat-digesting enzymes (assisted by the emulsification of fats by bile)
Production and release is controlled by CCK and secretin
Absorption
-occurs when the end products of digestion enter the capillaries of the villi after being transported into the intestinal cell plasma membranes
-fats enter north the capillaries and lymphatic vessels or lacteals by diffusion
Large intestine
-produces no digestive enzymes
-absorbs water and a few other substances and dries out indigestible waste
-1.5m in length 6-7cm in diameter
-extends from small intestine to anus
Subdivisions of the large intestine
- cecum
- appendix
- colon
-rectum - anal canal
Four regions of the colon
- ascending colon
-transverse colon
-deceasing colon
-sigmoid colon
Which salve is located at the entrance of the large intestine and keeps food from re-entering the small intestine
Ileocecal valve
The ouch below the ileocecal valve
Cecum
The appendix
-finger like projection suspended from the cecum
-plays a role in the immune system by providing the cecum with bacteria after an illness
Sigmoid colon
-s-shaped
-stores feces
The rectum
-final storage area for feces
- where water is absorbed and mucus is secreted
Anus
The opening of the anal canal
Goblet cells
Secrete mucus to aid in deification
Bacteria in the colon
- variety of bacteria colonize the colon
- some ferment indigestible carbohydrates
-others a synthesize vitamin B and vitamin K
Primary function of the large intestine
Propel fecal matter and eliminate it from the body
Bowel movement
- also calle mass movements
- long slow moving contractions of the colon
- occur 3-4 time a day
- push contents of the colon towards the rectum
- once feces enter the rectum the need to dedicate us felt
- internal sphincter may be voluntary relaxed or constricted to delay the passage if feces
GERD
- gastroesophageal reflux disease
-acid reflux occurs when stomach acids back up in the esophagus - weak cardioesophageal sphincter
- heartburn
-frequent reflux
Stomach ulcers
- hole or damaged area in the lining of the stomach most often caused by bacteria
- also called gastric ulcers
-primarily treated with antibiotics
-60% are caused by bacteria H. pylori
-20% are caused by NSAIDs such as aspirin or ibuprofen
Gallstones
- hard deposits of cholesterol
- pain is caused when stones move through or block bile duct
- surgical removal is most common treatment
Hepatitis
- inflammation of the liver usually caused by a virus
- type C is the deadliest infectious disease in the US
Pancreatitis
-Inflammation of pancreases when digestive enzymes are activated too soon and damage enzymes
-most commonly caused by gallstones or heavy alcohol use
IBD
-inflammatory bowl disease
-chronic inflammation of digestive tract, especially the large intestine
-includes crohns disease and ulcerative colitis
Appendicitis
- severe pain in lower right abdomen, nausea, vomiting
- treatment if removal of appendix, appendectomy
- can be fatal if ruptured
Cystic fibrosis
- inherited disease that causes a thick mucus to form in the lungs, pancreas, and other organs
-blocks secretion of digestive enzymes and bicarbonate solution from the pancreas
Hemorrhoids
- swollen veins in lower rectum
-can cause bleeding itching and pain
May result from straining during elimination
Vomiting and diarrhea
- caused by infection from a bacteria or virus such as norovirus
Cleft lip/palate
- occurs when when either the lip or palate (or both) fail to close during development
- leaving a split called a cleft
- one of the most common birth defects and can be fixed by surgery
PKU
-phenylketonuria is a rare genetic disorder that causes a build-up of the amino acid phenylalanine
- cause by a mutation in the gene for an enzyme that converts the amino acid into other compounds needed by the body
- in the US babies are screened for it at birth
- if untreated can result in Brain damage
Reflexes
- babies are both with the the rooting and sucking reflex
-triggered by touches of the cheek or anything on the roof of their mouth
Cancer
-there is an increase in the risk of cancer with age
-more than half of all cancers occur in people over the age of 65
-colorectal cancer is one of the most common types of cancers
